Multisensory maps in parietal cortex

The order of multisensory associative sequences is reinstated as context feature during successful recognition

The ability of the human brain to encode and recognize sequential information from different sensory modalities is key to memory formation. The sequence in which these modalities are presented during encoding critically affects recognition. This study investigates the encoding of sensory modality sequences and its neural impact on recognition using multivariate pattern analysis (MVPA) of oscillatory EEG activity. We examined the reinstatement of multisensory episode-specific sequences in n = 32 participants who encoded sound-image associations (e.g., the image of a ship with the sound of a frog). Images and sounds were natural scenes and 2-second real-life sounds, presented sequentially during encoding. During recognition, stimulus pairs were presented simultaneously, and classification was used to test whether the modality sequence order could be decoded as a contextual feature in memory. Oscillatory results identified a distinct neural signature during successful retrieval, associated with the original modality sequence. Furthermore, MVPA successfully decoded neural patterns of different modality sequences, hinting at specific memory traces. These findings suggest that the sequence in which sensory modalities are encoded forms a neural signature, affecting later recognition. This study provides novel insights into the relationship between modality encoding and recognition, with broad implications for cognitive neuroscience and memory research.

Semantic audio-visual congruence modulates visual sensitivity to biological motion across awareness levels

Whether cross-modal interaction requires conscious awareness of multisensory information or whether it can occur in the absence of awareness, is still an open question. Here, we investigated if sounds can enhance detection sensitivity of semantically matching visual stimuli at varying levels of visual awareness. We presented biological motion stimuli of human actions (walking, rowing, sawing) during dynamic continuous flash suppression (CFS) to 80 participants and measured the effect of co-occurring, semantically matching or non-matching action sounds on visual sensitivity (d'). By individually thresholding stimulus contrast, we distinguished participants who detected motion either above or at chance level. Participants who reliably detected visual motion above chance showed higher sensitivity to upright versus inverted biological motion across all experimental conditions. In contrast, participants detecting visual motion at chance level, i.e. during successful suppression, demonstrated this upright advantage exclusively during trials with semantically congruent sounds. Across the whole sample, the impact of sounds on visual sensitivity increased as participants' visual detection performance decreased, revealing a systematic trade-off between auditory and visual processing. Our findings suggest that semantic congruence between auditory and visual information can selectively modulate biological motion perception when visual awareness is minimal or absent, while more robust visual signals enable perception of biological motion independent of auditory input. Thus, semantically congruent sounds may impact visual representations as a function of the level of visual awareness.

Brain mechanisms of oral multisensory processing related to oral health: a systematic review of neuroimaging findings

AIM

Oral functions related to eating, including mastication, swallowing, and taste, are fundamentally a multisensory experience that relies on the crossmodal interaction of touch, gustation, temperature, pain, and proprioception. The brain mechanisms of oral multisensory processing related to eating have remained unknown.

METHODS

The current systematic review summarizes the findings from neuroimaging studies (mainly functional magnetic resonance imaging) focusing on the interaction of multiple sensory stimuli in human participants. Neuroimaging studies of human adults on the interaction between multiple sensory stimuli related to oral functions were identified and extracted via three electronic databases and reviewed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

RESULTS

Thirteen primary studies were eligible to be included in this review. Five studies investigated the interaction of intraoral (i.e., sensorimotor, taste, and noxious) stimuli. Six studies investigated the interaction between intraoral and extraoral (i.e., auditory, olfactory, and visual) stimuli. One study investigated the audio-visual interaction on dental fear, and another study investigated sensorimotor processing of eating tools. The studies showed great diversity in the experimental design of crossmodal interaction. Regarding the brain features related to the interaction, the somatosensory and motor regions were mostly reported in the studies.

CONCLUSIONS

The systematic review revealed a complex pattern of brain activation of oral multisensory processing, which can be attributed to the diversity in the experimental design of crossmodal interaction. The findings highlight the role of multisensory integration in maintaining oral health.

Increased sensorimotor and superior parietal activation correlate with reduced writing dysfluency in writer's cramp dystonia

Writer's cramp (WC) dystonia is a disabling brain disorder characterized by abnormal postures during writing tasks. Although abnormalities were identified in the sensorimotor, parietal, basal ganglia, and cerebellum, the network-level interactions between these brain regions and dystonia symptoms are not well understood. This study investigated the relationship between peak accelerations, an objective measure of writing dysfluency, and functional network (FN) activation in WC and healthy volunteers (HVs). Twenty WC and 22 HV performed a writing task using a kinematic software outside an MRI scanner and repeated it during functional MRI. Group independent component analysis identified 21 FNs, with left sensorimotor, superior parietal, cerebellum, and basal ganglia FNs selected for further analysis. These FNs were activated during writing and no group differences in FN activity were observed. Correlational analysis between FN activity and peak acceleration behavior revealed that reduced activity in left sensorimotor and superior parietal FNs correlated with greater writing dysfluency in WC, a pattern distinct from HVs. These findings suggest that enhanced activation of the left sensorimotor and superior parietal networks may mitigate writing dysfluency in WC. This study provides a mechanistic hypothesis to guide the development of network-based neuromodulation therapies for WC dystonia.

Self-other boundary under social threat in schizophrenia

Spatial representation of the self plays a vital role constructing our sense of bodily self-boundary that distinguishes the self from others. This perceptual border, known as the peripersonal space (PPS), has been suggested to be altered in individuals with schizophrenia (SZ). PPS represents a protective defensive zone that triggers alarm signals upon threat detection; thus disrupted PPS could lead to social interactional difficulties. However, very little is known about the impact of threat on PPS. To address this gap, a visual-tactile response-time (RT) experiment was conducted in immersive virtual reality (VR) for SZ and matched controls (CO). Participants were asked to detect a tactile vibration on their hand while an avatar (either threatening or neutral) approached them. Avatars were presented at different distance from the participants. PPS size and slope were estimated by identifying significant RT drop at the hypothesized self-other boundary. We also examined the relationship between PPS parameters, clinical symptoms and social disconnection. There was no overall group difference in PPS size. Perceived social threat posed in the avatars sharpened the self-boundary in CO but not in SZ. In SZ, shallower PPS slope was associated with delusion, persecution, negative symptoms and loneliness but not in CO. These results show that the regulation of self-other boundary in response to impending social threat may be maladaptive in SZ. Further research is needed on the causal mechanisms between self-disturbance and social impairments.

Seeing the piles of the velvet bending under our finger sliding over a tactile stimulator improves the feeling of the fabric

Using friction modulation to simulate fabrics with a tactile stimulator (i.e. virtual surface) is not sufficient to render fabric touch and even more so for hairy fabrics. We hypothesized that seeing the pile of the velvet darken or lighten depending on changes in the finger movement direction on the virtual surface should improve the velvet fabric rendering. Participants actively rubbed a tactile device or a velvet fabric looking at a screen that showed a synthesized image of a velvet that either remained static (V-static) or darkening/lightening with the direction of touch (V-moving). We showed that in V-moving condition, the touched surface was always perceived rougher, which is a descriptor of a real velvet (Experiment 1). Using electroencephalography and sources localization analyses, we found increased activity in the occipital and inferior parietal lobes (Experiment 2) when seeing dark and shining traces during back-and-forth finger movements over the virtual surface. This suggests that these two posterior cortical regions work together to evaluate visuo-tactile congruence between the seen and the felt (tactile). The visuo-tactile binding, evidenced by neural synchronization (specifically, theta band (5-7 Hz) oscillation) in the left inferior posterior parietal lobule, is consistent with enhanced integration of information and probably contributed to the emergence of a more realistic velvet representation.

The impact of metabolic syndrome on the cerebral cortex: a Mendelian randomization study

Metabolic syndrome exhibits associations with diverse neurological disorders, and its potential influence on the cerebral cortex may be one of the many potential factors contributing to these adverse outcomes. In this study, we aimed to investigate the causal relationship between metabolic syndrome and changes in cerebral cortex structure using Mendelian randomization analysis. Genome-wide association study data for the 5 components of metabolic syndrome were obtained from individuals of European descent in the UK Biobank. Genome-wide association study data for 34 known cortical functional regions were sourced from the ENIGMA Consortium. Data on Alzheimer's disease, major depression, and anxiety disorder were obtained from the IEU Open genome-wide association study database. The causal links between metabolic syndrome elements and cerebral cortex architecture were evaluated using inverse variance weighting, Mendelian randomization-Egger, and weighted median techniques, with inverse variance weighting as the primary method. Inverse variance weighting, Mendelian randomization Egger, weighted median, simple mode, and weighted mode methods were employed to assess the relationships between metabolic syndrome and neurological diseases (Alzheimer's disease, major depression, and anxiety disorder). Outliers, heterogeneity, and pleiotropy were assessed using Cochran's Q test, MR-PRESSO, leave-one-out analysis, and funnel plots. Globally, no causal link was found between metabolic syndrome and overall cortical thickness or surface area. However, regionally, metabolic syndrome may influence the surface area of specific regions, including the caudal anterior cingulate, postcentral, posterior cingulate, rostral anterior cingulate, isthmus cingulate, superior parietal, rostral middle frontal, middle temporal, insula, pars opercularis, cuneus, and inferior temporal. It may also affect the thickness of the medial orbitofrontal, caudal middle frontal, paracentral, superior frontal, superior parietal, and supramarginal regions. These findings were nominally significant and withstood sensitivity analyses, showing no substantial heterogeneity or pleiotropy. Furthermore, we found an association between metabolic syndrome and the risk of Alzheimer's disease, major depression, and anxiety disorder. This study suggests a potential association between metabolic syndrome and changes in cerebral cortex structure, which may underlie certain neurological disorders. Furthermore, we found an association between metabolic syndrome and the risk of Alzheimer's disease, major depression, and anxiety disorder. Early diagnosis of metabolic syndrome holds significance in preventing these neurological disorders.

Immediate and long-term brain activation of acupuncture on ischemic stroke patients: an ALE meta-analysis of fMRI studies

Background

Acupuncture, as an alternative and complementary therapy recommended by the World Health Organization for stroke treatment, holds potential in ameliorating neurofunctional deficits induced by ischemic stroke (IS). Understanding the immediate and long-term effects of acupuncture and their interrelation would contribute to a better comprehension of the mechanisms underlying acupuncture efficacy.

Methods

Activation likelihood estimation (ALE) meta-analysis was used to analyze the brain activation patterns reported in 21 relevant functional neuroimaging studies. Among these studies, 12 focused on the immediate brain activation and 9 on the long-term activation. Single dataset analysis were employed to identify both immediate and long-term brain activation of acupuncture treatment in IS patients, while contrast and conjunction analysis were utilized to explore distinctions and connections between the two.

Results

According to the ALE analysis, immediately after acupuncture treatment, IS patients exhibited an enhanced cluster centered around the right precuneus (PCUN) and a reduced cluster centered on the left middle frontal gyrus (MFG). After long-term acupuncture treatment, IS patients showed an enhanced cluster in the left PCUN, along with two reduced clusters in the right insula (INS) and hippocampus (HIP), respectively. Additionally, in comparison to long-term acupuncture treatment, the right angular gyrus (ANG) demonstrated higher ALE scores immediately after acupuncture, whereas long-term acupuncture resulted in higher scores in the left superior parietal gyrus (SPG). The intersecting cluster activated by both of them was located in the left cuneus (CUN).

Conclusion

The findings provide initial insights into both the immediate and long-term brain activation patterns of acupuncture treatment for IS, as well as the intricate interplay between them. Both immediate and long-term acupuncture treatments showed distinct patterns of brain activation, with the left CUN emerging as a crucial regulatory region in their association.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, CRD42023480834.

Exploring Electrocortical Signatures of Gait Adaptation: Differential Neural Dynamics in Slow and Fast Gait Adapters

Individuals exhibit significant variability in their ability to adapt locomotor skills, with some adapting quickly and others more slowly. Differences in brain activity likely contribute to this variability, but direct neural evidence is lacking. We investigated individual differences in electrocortical activity that led to faster locomotor adaptation rates. We recorded high-density electroencephalography while young, neurotypical adults adapted their walking on a split-belt treadmill and grouped them based on how quickly they restored their gait symmetry. Results revealed unique spectral signatures within the posterior parietal, bilateral sensorimotor, and right visual cortices that differ between fast and slow adapters. Specifically, fast adapters exhibited lower alpha power in the posterior parietal and right visual cortices during early adaptation, associated with quicker attainment of steady-state step length symmetry. Decreased posterior parietal alpha may reflect enhanced spatial attention, sensory integration, and movement planning to facilitate faster locomotor adaptation. Conversely, slow adapters displayed greater alpha and beta power in the right visual cortex during late adaptation, suggesting potential differences in visuospatial processing. Additionally, fast adapters demonstrated reduced spectral power in the bilateral sensorimotor cortices compared with slow adapters, particularly in the theta band, which may suggest variations in perception of the split-belt perturbation. These findings suggest that alpha and beta oscillations in the posterior parietal and visual cortices and theta oscillations in the sensorimotor cortex are related to the rate of gait adaptation.

How we perceive the width of grasped objects: Insights into the central processes that govern proprioceptive judgements

Low-level proprioceptive judgements involve a single frame of reference, whereas high-level proprioceptive judgements are made across different frames of reference. The present study systematically compared low-level (grasp → $\rightarrow$ grasp) and high-level (vision → $\rightarrow$ grasp, grasp → $\rightarrow$ vision) proprioceptive tasks, and quantified the consistency of grasp → $\rightarrow$ vision and possible reciprocal nature of related high-level proprioceptive tasks. Experiment 1 (n = 30) compared performance across vision → $\rightarrow$ grasp, a grasp → $\rightarrow$ vision and a grasp → $\rightarrow$ grasp tasks. Experiment 2 (n = 30) compared performance on the grasp → $\rightarrow$ vision task between hands and over time. Participants were accurate (mean absolute error 0.27 cm [0.20 to 0.34]; mean [95% CI]) and precise (R 2 $R^2$ = 0.95 [0.93 to 0.96]) for grasp → $\rightarrow$ grasp judgements, with a strong correlation between outcomes (r = -0.85 [-0.93 to -0.70]). Accuracy and precision decreased in the two high-level tasks (R 2 $R^2$ = 0.86 and 0.89; mean absolute error = 1.34 and 1.41 cm), with most participants overestimating perceived width for the vision → $\rightarrow$ grasp task and underestimating it for grasp → $\rightarrow$ vision task. There was minimal correlation between accuracy and precision for these two tasks. Converging evidence indicated performance was largely reciprocal (inverse) between the vision → $\rightarrow$ grasp and grasp → $\rightarrow$ vision tasks. Performance on the grasp → $\rightarrow$ vision task was consistent between dominant and non-dominant hands, and across repeated sessions a day or week apart. Overall, there are fundamental differences between low- and high-level proprioceptive judgements that reflect fundamental differences in the cortical processes that underpin these perceptions. Moreover, the central transformations that govern high-level proprioceptive judgements of grasp are personalised, stable and reciprocal for reciprocal tasks. KEY POINTS: Low-level proprioceptive judgements involve a single frame of reference (e.g. indicating the width of a grasped object by selecting from a series of objects of different width), whereas high-level proprioceptive judgements are made across different frames of reference (e.g. indicating the width of a grasped object by selecting from a series of visible lines of different length). We highlight fundamental differences in the precision and accuracy of low- and high-level proprioceptive judgements. We provide converging evidence that the neural transformations between frames of reference that govern high-level proprioceptive judgements of grasp are personalised, stable and reciprocal for reciprocal tasks. This stability is likely key to precise judgements and accurate predictions in high-level proprioception.

Modality-specific effects of threat on self-motion perception

BACKGROUND

Threat and individual differences in threat-processing bias perception of stimuli in the environment. Yet, their effect on perception of one's own (body-based) self-motion in space is unknown. Here, we tested the effects of threat on self-motion perception using a multisensory motion simulator with concurrent threatening or neutral auditory stimuli.

RESULTS

Strikingly, threat had opposite effects on vestibular and visual self-motion perception, leading to overestimation of vestibular, but underestimation of visual self-motions. Trait anxiety tended to be associated with an enhanced effect of threat on estimates of self-motion for both modalities.

CONCLUSIONS

Enhanced vestibular perception under threat might stem from shared neural substrates with emotional processing, whereas diminished visual self-motion perception may indicate that a threatening stimulus diverts attention away from optic flow integration. Thus, threat induces modality-specific biases in everyday experiences of self-motion.

Predicting attentional allocation in real-world environments: The need to investigate crossmodal semantic guidance

Real-world environments are multisensory, meaningful, and highly complex. To parse these environments in a highly efficient manner, a subset of this information must be selected both within and across modalities. However, the bulk of attention research has been conducted within sensory modalities, with a particular focus on vision. Visual attention research has made great strides, with over a century of research methodically identifying the underlying mechanisms that allow us to select critical visual information. Spatial attention, attention to features, and object-based attention have all been studied extensively. More recently, research has established semantics (meaning) as a key component to allocating attention in real-world scenes, with the meaning of an item or environment affecting visual attentional selection. However, a full understanding of how semantic information modulates real-world attention requires studying more than vision in isolation. The world provides semantic information across all senses, but with this extra information comes greater complexity. Here, we summarize visual attention (including semantic-based visual attention), crossmodal attention, and argue for the importance of studying crossmodal semantic guidance of attention. This article is categorized under: Psychology > Attention Psychology > Perception and Psychophysics.

Increases in pre-stimulus theta and alpha oscillations precede successful encoding of crossmodal associations

A central aspect of episodic memory is the formation of associations between stimuli from different modalities. Current theoretical approaches assume a functional role of ongoing oscillatory power and phase in the theta band (3-7 Hz) for the encoding of crossmodal associations. Furthermore, ongoing activity in the theta range as well as alpha (8-12 Hz) and low beta activity (13-20 Hz) before the presentation of a stimulus is thought to modulate subsequent cognitive processing, including processes that are related to memory. In this study, we tested the hypothesis that pre-stimulus characteristics of low frequency activity are relevant for the successful formation of crossmodal memory. The experimental design that was used specifically allowed for the investigation of associative memory independent from individual item memory. Participants (n = 51) were required to memorize associations between audiovisual stimulus pairs and distinguish them from newly arranged ones consisting of the same single stimuli in the subsequent recognition task. Our results show significant differences in the state of pre-stimulus theta and alpha power between remembered and not remembered crossmodal associations, clearly relating increased power to successful recognition. These differences were positively correlated with memory performance, suggesting functional relevance for behavioral measures of associative memory. Further analysis revealed similar effects in the low beta frequency ranges, indicating the involvement of different pre-stimulus-related cognitive processes. Phase-based connectivity measures in the theta band did not differ between remembered and not remembered stimulus pairs. The findings support the assumed functional relevance of theta band oscillations for the formation of associative memory and demonstrate that an increase of theta as well as alpha band oscillations in the pre-stimulus period is beneficial for the establishment of crossmodal memory.

Peripheral vision is mainly for looking rather than seeing

Vision includes looking and seeing. Looking, mainly via gaze shifts, selects a fraction of visual input information for passage through the brain's information bottleneck. The selected input is placed within the attentional spotlight, typically in the central visual field. Seeing decodes, i.e., recognizes and discriminates, the selected inputs. Hence, peripheral vision should be mainly devoted to looking, in particular, deciding where to shift the gaze. Looking is often guided exogenously by a saliency map created by the primary visual cortex (V1), and can be effective with no seeing and limited awareness. In seeing, peripheral vision not only suffers from poor spatial resolution, but is also subject to crowding and is more vulnerable to illusions by misleading, ambiguous, and impoverished visual inputs. Central vision, mainly for seeing, enjoys the top-down feedback that aids seeing in light of the bottleneck which is hypothesized to starts from V1 to higher areas. This feedback queries for additional information from lower visual cortical areas such as V1 for ongoing recognition. Peripheral vision is deficient in this feedback according to the Central-peripheral Dichotomy (CPD) theory. The saccades engendered by peripheral vision allows looking to combine with seeing to give human observers the impression of seeing the whole scene clearly despite inattentional blindness.

Mapping of facial and vocal processing in common marmosets with ultra-high field fMRI

Primate communication relies on multimodal cues, such as vision and audition, to facilitate the exchange of intentions, enable social interactions, avoid predators, and foster group cohesion during daily activities. Understanding the integration of facial and vocal signals is pivotal to comprehend social interaction. In this study, we acquire whole-brain ultra-high field (9.4 T) fMRI data from awake marmosets (Callithrix jacchus) to explore brain responses to unimodal and combined facial and vocal stimuli. Our findings reveal that the multisensory condition not only intensifies activations in the occipito-temporal face patches and auditory voice patches but also engages a more extensive network that includes additional parietal, prefrontal and cingulate areas, compared to the summed responses of the unimodal conditions. By uncovering the neural network underlying multisensory audiovisual integration in marmosets, this study highlights the efficiency and adaptability of the marmoset brain in processing facial and vocal social signals, providing significant insights into primate social communication.

How three-dimensional sketching environments affect spatial thinking: A functional magnetic resonance imaging study of virtual reality

Designers rely on sketching to visualize and refine their initial ideas, and virtual reality (VR) tools now facilitate sketching in immersive 3D environments. However, little research has been conducted on the differences in the visual and spatial processes involved in 3D versus 2D sketching and their effects on cognition. This study investigated potential differences in spatial and visual functions related to the use of 3D versus 2D sketching media by analyzing functional magnetic resonance imaging (fMRI) data. We recruited 20 healthy, right-handed students from the Department of Horticulture and Landscape Architecture with at least three years of experience in freehand landscape drawing. Using an Oculus Quest VR headset controller and a 12.9-inch iPad Pro with an Apple Pencil, we tested participants individually with 3D and 2D sketching, respectively. When comparing 2D and 3D sketches, our fMRI results revealed significant differences in the activation of several brain regions, including the right middle temporal gyrus, both sides of the parietal lobe, and the left middle occipital gyrus. We also compared different sketching conditions, such as lines, geometrical objects (cube), and naturalistic objects (perspective view of a tree), and found significant differences in the spatial and visual recognition of brain areas that support visual recognition, composition, and spatial perception. This finding suggests that 3D sketching environments, such as VR, may activate more visual-spatial functions during sketching compared to 2D environments. The result highlights the potential of immersive sketching environments for design-related processes and spatial thinking.

Reward-based option competition in human dorsal stream and transition from stochastic exploration to exploitation in continuous space

Primates exploring and exploiting a continuous sensorimotor space rely on dynamic maps in the dorsal stream. Two complementary perspectives exist on how these maps encode rewards. Reinforcement learning models integrate rewards incrementally over time, efficiently resolving the exploration/exploitation dilemma. Working memory buffer models explain rapid plasticity of parietal maps but lack a plausible exploration/exploitation policy. The reinforcement learning model presented here unifies both accounts, enabling rapid, information-compressing map updates and efficient transition from exploration to exploitation. As predicted by our model, activity in human frontoparietal dorsal stream regions, but not in MT+, tracks the number of competing options, as preferred options are selectively maintained on the map, while spatiotemporally distant alternatives are compressed out. When valuable new options are uncovered, posterior β1/α oscillations desynchronize within 0.4 to 0.7 s, consistent with option encoding by competing β1-stabilized subpopulations. Together, outcomes matching locally cached reward representations rapidly update parietal maps, biasing choices toward often-sampled, rewarded options.

Human brain representations of internally generated outcomes of approximate calculation revealed by ultra-high-field brain imaging

Much of human culture's advanced technology owes its existence to the ability to mentally manipulate quantities. Neuroscience has described the brain regions overall recruited by numerical tasks and the neuronal codes representing individual quantities during perceptual tasks. Nevertheless, it remains unknown how quantity representations are combined or transformed during mental computations and how specific quantities are coded in the brain when generated as the result of internal computations rather than evoked by a stimulus. Here, we imaged the brains of adult human subjects at 7 Tesla during an approximate calculation task designed to disentangle in- and outputs of the computation from the operation itself. While physically presented sample numerosities were distinguished in activity patterns along the dorsal visual pathway and within frontal and occipito-temporal regions, a representation of the internally generated result was most prominently detected in higher order regions such as angular gyrus and lateral prefrontal cortex. Behavioral precision in the task was related to cross-decoding performance between sample and result representations in medial IPS regions. This suggests the transformation of sample into result may be carried out within dorsal stream sensory-motor integration regions, and resulting outputs maintained for task purposes in higher-level regions in a format possibly detached from sensory-evoked inputs.

A multimodal cortical network of sensory expectation violation revealed by fMRI

The brain is subjected to multi-modal sensory information in an environment governed by statistical dependencies. Mismatch responses (MMRs), classically recorded with EEG, have provided valuable insights into the brain's processing of regularities and the generation of corresponding sensory predictions. Only few studies allow for comparisons of MMRs across multiple modalities in a simultaneous sensory stream and their corresponding cross-modal context sensitivity remains unknown. Here, we used a tri-modal version of the roving stimulus paradigm in fMRI to elicit MMRs in the auditory, somatosensory and visual modality. Participants (N = 29) were simultaneously presented with sequences of low and high intensity stimuli in each of the three senses while actively observing the tri-modal input stream and occasionally reporting the intensity of the previous stimulus in a prompted modality. The sequences were based on a probabilistic model, defining transition probabilities such that, for each modality, stimuli were more likely to repeat (p = .825) than change (p = .175) and stimulus intensities were equiprobable (p = .5). Moreover, each transition was conditional on the configuration of the other two modalities comprising global (cross-modal) predictive properties of the sequences. We identified a shared mismatch network of modality general inferior frontal and temporo-parietal areas as well as sensory areas, where the connectivity (psychophysiological interaction) between these regions was modulated during mismatch processing. Further, we found deviant responses within the network to be modulated by local stimulus repetition, which suggests highly comparable processing of expectation violation across modalities. Moreover, hierarchically higher regions of the mismatch network in the temporo-parietal area around the intraparietal sulcus were identified to signal cross-modal expectation violation. With the consistency of MMRs across audition, somatosensation and vision, our study provides insights into a shared cortical network of uni- and multi-modal expectation violation in response to sequence regularities.

Functional organization of the caudal part of the human superior parietal lobule

Like in macaque, the caudal portion of the human superior parietal lobule (SPL) plays a key role in a series of perceptive, visuomotor and somatosensory processes. Here, we review the functional properties of three separate portions of the caudal SPL, i.e., the posterior parieto-occipital sulcus (POs), the anterior POs, and the anterior part of the caudal SPL. We propose that the posterior POs is mainly dedicated to the analysis of visual motion cues useful for object motion detection during self-motion and for spatial navigation, while the more anterior parts are implicated in visuomotor control of limb actions. The anterior POs is mainly involved in using the spotlight of attention to guide reach-to-grasp hand movements, especially in dynamic environments. The anterior part of the caudal SPL plays a central role in visually guided locomotion, being implicated in controlling leg-related movements as well as the four limbs interaction with the environment, and in encoding egomotion-compatible optic flow. Together, these functions reveal how the caudal SPL is strongly implicated in skilled visually-guided behaviors.

Dynamic spatial coding in parietal cortex mediates tactile-motor transformation

Movements towards touch on the body require integrating tactile location and body posture information. Tactile processing and movement planning both rely on posterior parietal cortex (PPC) but their interplay is not understood. Here, human participants received tactile stimuli on their crossed and uncrossed feet, dissociating stimulus location relative to anatomy versus external space. Participants pointed to the touch or the equivalent location on the other foot, which dissociates sensory and motor locations. Multi-voxel pattern analysis of concurrently recorded fMRI signals revealed that tactile location was coded anatomically in anterior PPC but spatially in posterior PPC during sensory processing. After movement instructions were specified, PPC exclusively represented the movement goal in space, in regions associated with visuo-motor planning and with regional overlap for sensory, rule-related, and movement coding. Thus, PPC flexibly updates its spatial codes to accommodate rule-based transformation of sensory input to generate movement to environment and own body alike.

The structural connectivity mapping of the intralaminar thalamic nuclei

The intralaminar nuclei of the thalamus play a pivotal role in awareness, conscious experience, arousal, sleep, vigilance, as well as in cognitive, sensory, and sexual processing. Nonetheless, in humans, little is known about the direct involvement of these nuclei in such multifaceted functions and their structural connections in the brain. Thus, examining the versatility of structural connectivity of the intralaminar nuclei with the rest of the brain seems reasonable. Herein, we attempt to show the direct structural connectivity of the intralaminar nuclei to diencephalic, mesencephalic, and cortical areas using probabilistic tracking of the diffusion data from the human connectome project. The intralaminar nuclei fiber distributions span a wide range of subcortical and cortical areas. Moreover, the central medial and parafascicular nucleus reveal similar connectivity to the temporal, visual, and frontal cortices with only slight variability. The central lateral nucleus displays a refined projection to the superior colliculus and fornix. The centromedian nucleus seems to be an essential component of the subcortical somatosensory system, as it mainly displays connectivity via the medial and superior cerebellar peduncle to the brainstem and the cerebellar lobules. The subparafascicular nucleus projects to the somatosensory processing areas. It is interesting to note that all intralaminar nuclei have connections to the brainstem. In brief, the structural connectivity of the intralaminar nuclei aligns with the structural core of various functional demands for arousal, emotion, cognition, sensory, vision, and motor processing. This study sheds light on our understanding of the structural connectivity of the intralaminar nuclei with cortical and subcortical structures, which is of great interest to a broader audience in clinical and neuroscience research.

Peripheral and central sensation: multisensory orienting and recognition across species

Attentional bottlenecks force animals to deeply process only a selected fraction of sensory inputs. This motivates a unifying central-peripheral dichotomy (CPD), which separates multisensory processing into functionally defined central and peripheral senses. Peripheral senses (e.g., human audition and peripheral vision) select a fraction of the sensory inputs by orienting animals' attention; central senses (e.g., human foveal vision) allow animals to recognize the selected inputs. Originally used to understand human vision, CPD can be applied to multisensory processes across species. I first describe key characteristics of central and peripheral senses, such as the degree of top-down feedback and density of sensory receptors, and then show CPD as a framework to link ecological, behavioral, neurophysiological, and anatomical data and produce falsifiable predictions.

Dynamic Feedback Between Antidepressant Placebo Expectancies and Mood

Importance

Despite high antidepressant placebo response rates, the mechanisms underlying the persistence of antidepressant placebo effects are still poorly understood.

Objective

To investigate the neurobehavioral mechanisms underlying the evolution of antidepressant placebo effects using a reinforcement learning (RL) framework.

Design, Setting, and Participants

In this acute within-patient cross-sectional study of antidepressant placebos, patients aged 18 to 55 years not receiving medication for major depressive disorder (MDD) were recruited at the University of Pittsburgh between February 21, 2017, to March 1, 2021.

Interventions

The antidepressant placebo functional magnetic resonance imaging task manipulates placebo-associated expectancies using visually cued fast-acting antidepressant infusions and controls their reinforcement with sham visual neurofeedback while assessing expected and experienced mood improvement.

Main Outcomes and Measures

The trial-by-trial evolution of expectancies and mood was examined using multilevel modeling and RL, relating model-predicted signals to spatiotemporal dynamics of blood oxygenation level-dependent (BOLD) response.

Results

A bayesian RL model comparison in 60 individuals (mean [SE] age, 24.5 [0.8] years; 51 females [85%]) with MDD revealed that antidepressant placebo trial-wise expectancies were updated by composite learning signals multiplexing sensory evidence (neurofeedback) and trial-wise mood (bayesian omnibus risk <0.001; exceedance probability = 97%). Placebo expectancy, neurofeedback manipulations, and composite learning signals modulated the visual cortex and dorsal attention network (threshold-free cluster enhancement [TFCE] = 1 - P >.95). As participants anticipated antidepressant infusions, learned placebo expectancies modulated the salience network (SN, TFCE = 1 - P >.95), positively scaling with depression severity.

Conclusions and Relevance

Results of this cross-sectional study suggest that on a timescale of minutes, antidepressant placebo effects were maintained by positive feedback loops between expectancies and mood improvement. During learning, representations of placebos and their perceived effects were enhanced in primary and secondary sensory cortices. Latent learned placebo expectancies were encoded in the SN.

Parieto-Occipital Electrocortical Dynamics during Real-World Table Tennis

Traditional human electroencephalography (EEG) experiments that study visuomotor processing use controlled laboratory conditions with limited ecological validity. In the real world, the brain integrates complex, dynamic, multimodal visuomotor cues to guide the execution of movement. The parietal and occipital cortices are especially important in the online control of goal-directed actions. Table tennis is a whole-body, responsive activity requiring rapid visuomotor integration that presents a myriad of unanswered neurocognitive questions about brain function during real-world movement. The aim of this study was to quantify the electrocortical dynamics of the parieto-occipital cortices while playing a sport with high-density electroencephalography. We included analysis of power spectral densities (PSDs), event-related spectral perturbations, intertrial phase coherences (ITPCs), event-related potentials (ERPs), and event-related phase coherences of parieto-occipital source-localized clusters while participants played table tennis with a ball machine and a human. We found significant spectral power fluctuations in the parieto-occipital cortices tied to hit events. Ball machine trials exhibited more fluctuations in θ power around hit events, an increase in intertrial phase coherence and deflection in the event-related potential, and higher event-related phase coherence between parieto-occipital clusters as compared with trials with a human. Our results suggest that sport training with a machine elicits fundamentally different brain dynamics than training with a human.

Contrary neuronal recalibration in different multisensory cortical areas

The adult brain demonstrates remarkable multisensory plasticity by dynamically recalibrating itself based on information from multiple sensory sources. After a systematic visual-vestibular heading offset is experienced, the unisensory perceptual estimates for subsequently presented stimuli are shifted toward each other (in opposite directions) to reduce the conflict. The neural substrate of this recalibration is unknown. Here, we recorded single-neuron activity from the dorsal medial superior temporal (MSTd), parietoinsular vestibular cortex (PIVC), and ventral intraparietal (VIP) areas in three male rhesus macaques during this visual-vestibular recalibration. Both visual and vestibular neuronal tuning curves in MSTd shifted - each according to their respective cues' perceptual shifts. Tuning of vestibular neurons in PIVC also shifted in the same direction as vestibular perceptual shifts (cells were not robustly tuned to the visual stimuli). By contrast, VIP neurons demonstrated a unique phenomenon: both vestibular and visual tuning shifted in accordance with vestibular perceptual shifts. Such that, visual tuning shifted, surprisingly, contrary to visual perceptual shifts. Therefore, while unsupervised recalibration (to reduce cue conflict) occurs in early multisensory cortices, higher-level VIP reflects only a global shift, in vestibular space.

The influence of tDCS on perceived bouncing/streaming

Processing ambiguous situations is a constant challenge in everyday life and sensory input from different modalities needs to be integrated to form a coherent mental representation on the environment. The bouncing/streaming illusion can be studied to provide insights into the ambiguous perception and processing of multi-modal environments. In short, the likelihood of reporting bouncing rather than streaming impressions increases when a sound coincides with the moment of overlap between two moving disks. Neuroimaging studies revealed that the right posterior parietal cortex is crucial in cross-modal integration and is active during the bouncing/streaming illusion. Consequently, in the present study, we used transcranial direct current stimulation to stimulate this brain area. In the active stimulation conditions, a 9 cm² electrode was positioned over the P4-EEG position and the 35 cm² reference positioned over the left upper arm. The stimulation lasted 15 min. Each participant did the bouncing/streaming task three times: before, during and after anodal or sham stimulation. In a sample of N = 60 healthy, young adults, we found no influence of anodal tDCS. Bayesian analysis showed strong evidence against tDCS effects. There are two possible explanations for the finding that anodal tDCS over perceptual areas did not modulate multimodal integration. First, upregulation of multimodal integration is not possible using tDCS over the PPC as the integration process already functions at maximum capacity. Second, prefrontal decision-making areas may have overruled any modulated input from the PPC as it may not have matched their decision-making criterion and compensated for the modulation.

Primate preoptic neurons drive hypothermia and cold defense

Maintaining body temperature within a narrow range is vital for warm-blooded animals. In rodents, the preoptic area (POA) of the hypothalamus detects and regulates core body temperature. However, knowledge about the thermal regulation center in primates remains limited. Here, we show that activating a subpopulation of POA neurons by a chemogenetic strategy reliably induces hypothermia in anesthetized and freely moving macaques. Comprehensive monitoring of physiological parameters reveals that such hypothermia is accompanied by autonomic changes including a rise in heart rate, skeletal muscle activity, and correlated biomarkers in blood. Consistent with enhanced ambulatory movement during hypothermia, the animals show a full range of cold-defense behaviors. Resting-state fMRI confirms the chemogenetic activation of POA and charts a brain-wide network of thermoregulation. Altogether, our findings demonstrate the central regulation of body temperature in primates and pave the way for future application in clinical practice.

Interdigitated Columnar Representation of Personal Space and Visual Space in Human Parietal Cortex

Personal space (PS) is the space around the body that people prefer to maintain between themselves and unfamiliar others. Intrusion into personal space evokes discomfort and an urge to move away. Physiologic studies in nonhuman primates suggest that defensive responses to intruding stimuli involve the parietal cortex. We hypothesized that the spatial encoding of interpersonal distance is initially transformed from purely sensory to more egocentric mapping within human parietal cortex. This hypothesis was tested using 7 Tesla (7T) fMRI at high spatial resolution (1.1 mm isotropic), in seven subjects (four females, three males). In response to visual stimuli presented at a range of virtual distances, we found two categories of distance encoding in two corresponding radially-extending columns of activity within parietal cortex. One set of columns (P columns) responded selectively to moving and stationary face images presented at virtual distances that were nearer (but not farther) than each subject's behaviorally-defined personal space boundary. In most P columns, BOLD response amplitudes increased monotonically and nonlinearly with increasing virtual face proximity. In the remaining P columns, BOLD responses decreased with increasing proximity. A second set of parietal columns (D columns) responded selectively to disparity-based distance cues (near or far) in random dot stimuli, similar to disparity-selective columns described previously in occipital cortex. Critically, in parietal cortex, P columns were topographically interdigitated (nonoverlapping) with D columns. These results suggest that visual spatial information is transformed from visual to body-centered (or person-centered) dimensions in multiple local sites within human parietal cortex.SIGNIFICANCE STATEMENT Recent COVID-related social distancing practices highlight the need to better understand brain mechanisms which regulate "personal space" (PS), which is defined by the closest interpersonal distance that is comfortable for an individual. Using high spatial resolution brain imaging, we tested whether a map of external space is transformed from purely visual (3D-based) information to a more egocentric map (related to personal space) in human parietal cortex. We confirmed this transformation and further showed that it was mediated by two mutually segregated sets of columns: one which encoded interpersonal distance and another that encoded visual distance. These results suggest that the cortical transformation of sensory-centered to person-centered encoding of space near the body involves short-range communication across interdigitated columns within parietal cortex.

An evaluation of how connectopic mapping reveals visual field maps in V1

Abstract

Functional gradients, in which response properties change gradually across the cortical surface, have been proposed as a key organising principle of the brain. However, the presence of these gradients remains undetermined in many brain regions. Resting-state neuroimaging studies have suggested these gradients can be reconstructed from patterns of functional connectivity. Here we investigate the accuracy of these reconstructions and establish whether it is connectivity or the functional properties within a region that determine these “connectopic maps”. Different manifold learning techniques were used to recover visual field maps while participants were at rest or engaged in natural viewing. We benchmarked these reconstructions against maps measured by traditional visual field mapping. We report an initial exploratory experiment of a publicly available naturalistic imaging dataset, followed by a preregistered replication using larger resting-state and naturalistic imaging datasets from the Human Connectome Project. Connectopic mapping accurately predicted visual field maps in primary visual cortex, with better predictions for eccentricity than polar angle maps. Non-linear manifold learning methods outperformed simpler linear embeddings. We also found more accurate predictions during natural viewing compared to resting-state. Varying the source of the connectivity estimates had minimal impact on the connectopic maps, suggesting the key factor is the functional topography within a brain region. The application of these standardised methods for connectopic mapping will allow the discovery of functional gradients across the brain.

Protocol registration

The stage 1 protocol for this Registered Report was accepted in principle on 19 April 2022. The protocol, as accepted by the journal, can be found at 10.6084/m9.figshare.19771717.

Aging: working memory capacity and spatial strategies in a virtual orientation task

Brain networks involved in working and spatial memory are closely intertwined, outlining a potential relation between these processes, which are also affected in non-pathological aging. Working memory is a pre-requisite for other complex cognitive processes. The main aim of this study is to explore how working memory capacity (WMC) can influence the asymmetrical decline in spatial orientation strategies in an older segment of population compared to young participants. Forty-eight older adults and twelve young students took part in the study. Working memory and spatial memory were assessed using the Change Localization Task and The Boxes Room Task, respectively. In The Boxes Room Task, two different configurations assessed the use of egocentric and allocentric reference frames. Results showed that older adults with better WMC outperformed those with lower WMC in several tasks. Independently of WMC capacity, older participants performed better in the allocentric condition of The Boxes Room. In addition, young participants outscored low WMC older participants, but did not differ from high WMC older adults. Overly, these findings support the important relationship between working memory capacity and spatial orientations abilities. Thus, basic cognitive mechanisms engaged in information processing could inform about other brain processes more complex in nature, like spatial orientation skills.

Imaging Insights of Isolated Idiopathic Dystonia: Voxel-Based Morphometry and Activation Likelihood Estimation Studies

The understanding of brain structural abnormalities across different clinical forms of dystonia and their contribution to clinical characteristics remains unclear. The objective of this study is to investigate shared and specific gray matter volume (GMV) abnormalities in various forms of isolated idiopathic dystonia. We collected imaging data from 73 isolated idiopathic dystonia patients and matched them with healthy controls to explore the GMV alterations in patients and their correlations with clinical characteristics using the voxel-based morphometry (VBM) technique. In addition, we conducted an activation likelihood estimation (ALE) meta-analysis of previous VBM studies. Our study demonstrated widespread morphometry alterations in patients with idiopathic dystonia. Multiple systems were affected, which mainly included basal ganglia, sensorimotor, executive control, and visual networks. As the result of the ALE meta-analysis, a convergent cluster with increased GMV was found in the left globus pallidus. In subgroup VBM analyses, decreased putamen GMV was observed in all clinic forms, while the increased GMV was observed in parahippocampal, lingual, and temporal gyrus. GD demonstrated the most extensive GMV abnormalities in cortical regions, and the aberrant GMV of the posterior cerebellar lobe was prominent in CD. Moreover, trends of increased GMV regions of the left precuneus and right superior frontal gyrus were demonstrated in the moderate-outcome group compared with the superior-outcome group. Results of our study indicated shared pathophysiology of the disease-centered on the dysfunction of the basal ganglia-thalamo-cortical circuit, impairing sensorimotor integration, high-level motor execution, and cognition of patients. Dysfunction of the cerebello-thalamo-cortical circuit could also be involved in CD especially. Finally, the frontal-parietal pathway may act as a potential marker for predicting treatment outcomes such as deep brain stimulation.

Improving Depressive Symptoms of Post-stroke Depression Using the Shugan Jieyu Capsule: A Resting-State Functional Magnetic Resonance Imaging Study

Regional homogeneity (ReHo) and fractional amplitude of low-frequency fluctuation (fALFF) were used to detect the neuroimaging mechanism of Shugan Jieyu Capsule (SG) in ameliorating depression of post-stroke depression (PSD) patients. Fifteen PSD patients took SG for 8 weeks, completed the 24-item Hamilton Depression Scale (HAMD) assessment at the baseline and 8 weeks later, and underwent functional magnetic resonance imaging (fMRI) scanning. Twenty-one healthy controls (HCs) underwent these assessments at the baseline. We found that SG improved depression of PSD patients, in which ReHo values decreased in the left calcarine sulcus (CAL.L) and increased in the left superior frontal gyrus (SFG.L) of PSD patients at the baseline. The fALFF values of the left inferior parietal cortex (IPL.L) decreased in PSD patients at the baseline. Abnormal functional activities in the brain regions were reversed to normal levels after the administration of SG for 8 weeks. Receiver operating characteristic (ROC) analysis found that the changes in three altered brain regions could be used to differentiate PSD patients at the baseline and HCs. Average signal values of altered regions were related to depression in all subjects at the baseline. Our results suggest that SG may ameliorate depression of PSD patients by affecting brain region activity and local synchronization.

Morphological patterns and spatial probability maps of the superior parietal sulcus in the human brain

The superior parietal sulcus (SPS) is the defining sulcus within the superior parietal lobule (SPL). The morphological variability of the SPS was examined in individual magnetic resonance imaging (MRI) scans of the human brain that were registered to the Montreal Neurological Institute (MNI) standard stereotaxic space. Two primary morphological patterns were consistently identified across hemispheres: (i) the SPS was identified as a single sulcus, separating the anterior from the posterior part of the SPL and (ii) the SPS was found as a complex of multiple sulcal segments. These morphological patterns were subdivided based on whether the SPS or SPS complex remained distinct or merged with surrounding parietal sulci. The morphological variability and spatial extent of the SPS were quantified using volumetric and surface spatial probabilistic mapping. The current investigation established consistent morphological patterns in a common anatomical space, the MNI stereotaxic space, to facilitate structural and functional analyses within the SPL.

Towards a mechanistic understanding of mindfulness-based stress reduction (MBSR) using an RCT neuroimaging approach: Effects on regulating own stress in social and non-social situations

Although much research has shown that mindfulness-based interventions (MBIs) can reduce psychological stress, it is less clear if effects generalize to everyday social situations, which range among the largest stress triggers. Furthermore, mechanisms of MBIs have not been fully established. Emotion regulation (ER) has been suggested as one key mechanism, yet the role of cognitive reappraisal and acceptance strategies is still under debate. To address these questions, a neuroimaging-based randomized controlled trial (RCT) was performed (n=68), comparing mindfulness-based stress reduction (MBSR) with a reading/listening intervention (READ), using a novel dyadic paradigm for self and other emotion regulation under stress as primary outcome on behavior and brain levels and established empathy measures (clinicatrials.gov NCT03035669). Compared to READ, MBSR led to self-reported stress reduction through both cognitive reappraisal and acceptance only when regulating self and not when regulating others' distress. In addition, MBSR led to increased brain activation over time for regulating own (parietal cortex) and others' (precuneus, TPJ) emotions through cognitive reappraisal and acceptance, albeit this effect was also seen for the reading intervention for regulating own stress via reappraisal. Brain changes did not scale with subjective stress reduction and amount of meditation practice. More distant generalization effects of MBSR on socio-emotional functioning (cognitive empathy and compassion) could also not be shown. This study identified both cognitive reappraisal and acceptance as two ER mechanisms of MBSR, but indicates that effects do not extend to social settings.

Voxel-based meta-analysis of gray matter abnormalities in idiopathic dystonia

BACKGROUND

Neuroimaging studies have reported gray matter changes in patients with idiopathic dystonia but with considerable variations. Here, we aimed to investigate the convergence of dystonia-related gray matter changes across studies.

METHODS

The whole brain voxel-based morphometry studies comparing idiopathic dystonia and healthy controls were systematically searched in the PubMed, Web of Science and Embase. Meta-analysis of gray matter changes was performed using the anisotropic effect size-based signed differential mapping.

RESULTS

Twenty-eight studies comparing 701 idiopathic dystonia patients and 712 healthy controls were included in the meta-analysis. Compared to healthy controls, idiopathic dystonia patients showed increased gray matter in bilateral precentral and postcentral gyri, bilateral putamen and pallidum, right insula, and left supramarginal gyrus, while decreased gray matter in bilateral temporal poles, bilateral supplementary motor areas, right angular gyrus, inferior parietal gyrus and precuneus, left insula and inferior frontal gyrus. These findings remained robust in the jackknife sensitivity analysis, and no significant heterogeneity was detected. Subgroup analyses of different phenotypes of dystonia were performed to further confirm the above findings.

CONCLUSION

The meta-analysis showed that consistent widespread gray matter abnormalities were shared in different subtypes of idiopathic dystonia and were not restricted to the corticostriatal circuits.

Exploring Cognition with Brain-Machine Interfaces

Traditional brain-machine interfaces decode cortical motor commands to control external devices. These commands are the product of higher-level cognitive processes, occurring across a network of brain areas, that integrate sensory information, plan upcoming motor actions, and monitor ongoing movements. We review cognitive signals recently discovered in the human posterior parietal cortex during neuroprosthetic clinical trials. These signals are consistent with small regions of cortex having a diverse role in cognitive aspects of movement control and body monitoring, including sensorimotor integration, planning, trajectory representation, somatosensation, action semantics, learning, and decision making. These variables are encoded within the same population of cells using structured representations that bind related sensory and motor variables, an architecture termed partially mixed selectivity. Diverse cognitive signals provide complementary information to traditional motor commands to enable more natural and intuitive control of external devices.

The macaque ventral intraparietal area has expanded into three homologue human parietal areas

The macaque ventral intraparietal area (VIP) in the fundus of the intraparietal sulcus has been implicated in a diverse range of sensorimotor and cognitive functions such as motion processing, multisensory integration, processing of head peripersonal space, defensive behavior, and numerosity coding. Here, we exhaustively review macaque VIP function, cytoarchitectonics, and anatomical connectivity and integrate it with human studies that have attempted to identify a potential human VIP homologue. We show that human VIP research has consistently identified three, rather than one, bilateral parietal areas that each appear to subsume some, but not all, of the macaque area's functionality. Available evidence suggests that this human "VIP complex" has evolved as an expansion of the macaque area, but that some precursory specialization within macaque VIP has been previously overlooked. The three human areas are dominated, roughly, by coding the head or self in the environment, visual heading direction, and the peripersonal environment around the head, respectively. A unifying functional principle may be best described as prediction in space and time, linking VIP to state estimation as a key parietal sensorimotor function. VIP's expansive differentiation of head and self-related processing may have been key in the emergence of human bodily self-consciousness.

Auditory, Visual, and Cross-Modal Mismatch Negativities in the Rat Auditory and Visual Cortices

When the brain tries to acquire an elaborate model of the world, multisensory integration should contribute to building predictions based on the various pieces of information, and deviance detection should repeatedly update these predictions by detecting “errors” from the actual sensory inputs. Accumulating evidence such as a hierarchical organization of the deviance-detection system indicates that the deviance-detection system can be interpreted in the predictive coding framework. Herein, we targeted mismatch negativity (MMN) as a type of prediction-error signal and investigated the relationship between multisensory integration and MMN. In particular, we studied whether and how cross-modal information processing affected MMN in rodents. We designed a new surface microelectrode array and simultaneously recorded visual and auditory evoked potentials from the visual and auditory cortices of rats under anesthesia. Then, we mapped MMNs for five types of deviant stimuli: single-modal deviants in (i) the visual oddball and (ii) auditory oddball paradigms, eliciting single-modal MMN; (iii) congruent audio-visual deviants, (iv) incongruent visual deviants, and (v) incongruent auditory deviants in the audio-visual oddball paradigm, eliciting cross-modal MMN. First, we demonstrated that visual MMN exhibited deviance detection properties and that the first-generation focus of visual MMN was localized in the visual cortex, as previously reported in human studies. Second, a comparison of MMN amplitudes revealed a non-linear relationship between single-modal and cross-modal MMNs. Moreover, congruent audio-visual MMN exhibited characteristics of both visual and auditory MMNs—its latency was similar to that of auditory MMN, whereas local blockage of N-methyl-D-aspartic acid receptors in the visual cortex diminished it as well as visual MMN. These results indicate that cross-modal information processing affects MMN without involving strong top-down effects, such as those of prior knowledge and attention. The present study is the first electrophysiological evidence of cross-modal MMN in animal models, and future studies on the neural mechanisms combining multisensory integration and deviance detection are expected to provide electrophysiological evidence to confirm the links between MMN and predictive coding theory.

Vision for action: thalamic and cortical inputs to the macaque superior parietal lobule

The dorsal visual stream, the cortical circuit that in the primate brain is mainly dedicated to the visual control of actions, is split into two routes, a lateral and a medial one, both involved in coding different aspects of sensorimotor control of actions. The lateral route, named "lateral grasping network", is mainly involved in the control of the distal part of prehension, namely grasping and manipulation. The medial route, named "reach-to-grasp network", is involved in the control of the full deployment of prehension act, from the direction of arm movement to the shaping of the hand according to the object to be grasped. In macaque monkeys, the reach-to-grasp network (the target of this review) includes areas of the superior parietal lobule (SPL) that hosts visual and somatosensory neurons well suited to control goal-directed limb movements toward stationary as well as moving objects. After a brief summary of the neuronal functional properties of these areas, we will analyze their cortical and thalamic inputs thanks to retrograde neuronal tracers separately injected into the SPL areas V6, V6A, PEc, and PE. These areas receive visual and somatosensory information distributed in a caudorostral, visuosomatic trend, and some of them are directly connected with the dorsal premotor cortex. This review is particularly focused on the origin and type of visual information reaching the SPL, and on the functional role this information can play in guiding limb interaction with objects in structured and dynamic environments.

Neuroplasticity and Crossmodal Connectivity in the Normal, Healthy Brain

Objective

Neuroplasticity enables the brain to establish new crossmodal connections or reorganize old connections which are essential to perceiving a multisensorial world. The intent of this review is to identify and summarize the current developments in neuroplasticity and crossmodal connectivity, and deepen understanding of how crossmodal connectivity develops in the normal, healthy brain, highlighting novel perspectives about the principles that guide this connectivity.

Methods

To the above end, a narrative review is carried out. The data documented in prior relevant studies in neuroscience, psychology and other related fields available in a wide range of prominent electronic databases are critically assessed, synthesized, interpreted with qualitative rather than quantitative elements, and linked together to form new propositions and hypotheses about neuroplasticity and crossmodal connectivity.

Results

Three major themes are identified. First, it appears that neuroplasticity operates by following eight fundamental principles and crossmodal integration operates by following three principles. Second, two different forms of crossmodal connectivity, namely direct crossmodal connectivity and indirect crossmodal connectivity, are suggested to operate in both unisensory and multisensory perception. Third, three principles possibly guide the development of crossmodal connectivity into adulthood. These are labeled as the principle of innate crossmodality, the principle of evolution-driven 'neuromodular' reorganization and the principle of multimodal experience. These principles are combined to develop a three-factor interaction model of crossmodal connectivity.

Conclusions

The hypothesized principles and the proposed model together advance understanding of neuroplasticity, the nature of crossmodal connectivity, and how such connectivity develops in the normal, healthy brain.

Distinct Causal Influences of Dorsolateral Prefrontal Cortex and Posterior Parietal Cortex in Multiple-Option Decision Making

Our knowledge about neural mechanisms underlying decision making is largely based on experiments that involved few options. However, it is more common in daily life to choose between many options, in which processing choice information selectively is particularly important. The current study examined whether the dorsolateral prefrontal cortex (dlPFC) and posterior parietal cortex (PPC) are of particular importance to multiple-option decision making. Sixty-eight participants received anodal high definition-transcranial direct current stimulation (HD-tDCS) to focally enhance dlPFC or PPC in a double-blind sham-controlled design. Participants then performed a multiple-option decision making task. We found longer fixations on poorer options were related to less optimal decisions. Interestingly, this negative impact was attenuated after applying anodal HD-tDCS over dlPFC, especially in choices with many options. This suggests that dlPFC has a causal role in filtering choice-irrelevant information. In contrast, these effects were absent after participants received anodal HD-tDCS over PPC. Instead, the choices made by these participants were more biased towards the best options presented on the side contralateral to the stimulation. This suggests PPC has a causal role in value-based spatial selection. To conclude, the dlPFC has a role in filtering undesirable options, whereas the PPC emphasizes the desirable contralateral options.

Patients with lesions to the intraparietal cortex show greater proprioceptive realignment after prism adaptation: Evidence from open-loop pointing and manual straight ahead

Reaching toward a target viewed through laterally refracting prisms results in adaptation of both visual and (limb) proprioceptive spatial representations. Common ways to measure adaptation after-effect are to ask a person to point straight ahead with their eyes closed ("manual straight ahead", MSA), or to a seen target using their unseen hand ("open-loop pointing", OLP). MSA measures changes in proprioception only, whereas OLP measures the combined visual and proprioceptive shift. The behavioural and neurological mechanisms of prism adaptation have come under scrutiny following reports of reduced hemispatial neglect in patients following this procedure. We present evidence suggesting that shifts in proprioceptive spatial representations induced by prism adaptation are larger following lesions to the intraparietal cortex - a brain region that integrates retinotopic visual signals with signals of eye position in the orbit and that is activated during prism adaptation. Six healthy participants and six patients with unilateral intraparietal cortex lesions underwent prism adaptation. After-effects were measured with OLP and MSA. After-effects of control participants were larger when measured with OLP than with MSA, consistent with previous research and with the additional contribution of visual shift to OLP after-effects. However, patients' OLP shifts were not significantly different to their MSA shifts. We conclude that, for the patients, correction of pointing errors during prism adaptation involved proportionally more changes to arm proprioception than for controls. Since lesions to intraparietal cortex led to enhanced realignment of arm proprioceptive representations, our results indirectly suggest that the intraparietal cortex could be key for visual realignment.

Neural encoding of actual and imagined touch within human posterior parietal cortex

In the human posterior parietal cortex (PPC), single units encode high-dimensional information with partially mixed representations that enable small populations of neurons to encode many variables relevant to movement planning, execution, cognition, and perception. Here, we test whether a PPC neuronal population previously demonstrated to encode visual and motor information is similarly engaged in the somatosensory domain. We recorded neurons within the PPC of a human clinical trial participant during actual touch presentation and during a tactile imagery task. Neurons encoded actual touch at short latency with bilateral receptive fields, organized by body part, and covered all tested regions. The tactile imagery task evoked body part-specific responses that shared a neural substrate with actual touch. Our results are the first neuron-level evidence of touch encoding in human PPC and its cognitive engagement during a tactile imagery task, which may reflect semantic processing, attention, sensory anticipation, or imagined touch.

Sensory capability and information integration independently explain the cognitive status of healthy older adults

While there is evidence that sensory processing and multisensory integration change with age, links between these alterations and their relation to cognitive status remain unclear. In this study, we assessed sensory thresholds and performance of healthy younger and older adults in a visuotactile delayed match-to-sample task. Using Bayesian structural equation modelling (BSEM), we explored the factors explaining cognitive status in the group of older adults. Additionally, we applied transcranial alternating current stimulation (tACS) to a parieto-central network found to underlie visuotactile interactions and working memory matching in our previous work. Response times and signal detection measures indicated enhanced multisensory integration and enhanced benefit from successful working memory matching in older adults. Further, tACS caused a frequency-specific speeding (20 Hz) and delaying (70 Hz) of responses. Data exploration suggested distinct underlying factors for sensory acuity and sensitivity d’ on the one side, and multisensory and working memory enhancement on the other side. Finally, BSEM showed that these two factors labelled ‘sensory capability’ and ‘information integration’ independently explained cognitive status. We conclude that sensory decline and enhanced information integration might relate to distinct processes of ageing and discuss a potential role of the parietal cortex in mediating augmented integration in older adults.

A Sensorimotor Numerosity System

Incoming sensory input provides information for the planning and execution of actions, which yield motor outcomes that are themselves sensory inputs. One dimension where action and perception strongly interact is numerosity perception. Many non-human animals can estimate approximately the number of external elements as well as their own actions, and neurons have been identified that respond to both. Recent psychophysical adaptation studies on humans also provide evidence for neural mechanisms responding to both the number of externally generated events and self-produced actions. Here we advance the idea that these strong connections may arise from dedicated sensorimotor mechanisms in the brain, part of a more generalized system interfacing action with the processing of other quantitative magnitudes such as space and time.

Hierarchical cortical gradients in somatosensory processing

Sensory information is processed in the visual cortex in distinct streams of different anatomical and functional properties. A comparable organizational principle has also been proposed to underlie auditory processing. This raises the question of whether a similar principle characterize the somatosensory domain. One property of a cortical stream is a hierarchical organization of the neuronal response properties along an anatomically distinct pathway. Indeed, several hierarchies between specific somatosensory cortical regions have been identified, primarily using electrophysiology, in non-human primates. However, it has been unclear how these local hierarchies are organized throughout the cortex. Here we used phase-encoded bilateral full-body light touch stimulation in healthy humans under functional MRI to study the large-scale organization of hierarchies in the somatosensory domain. We quantified two measures of hierarchy of BOLD responses, selectivity and laterality. We measured how selectivity and laterality change as we move away from the central sulcus within four gross anatomically-distinct regions. We found that both selectivity and laterality decrease in three directions: parietal, posteriorly along the parietal lobe, frontal, anteriorly along the frontal lobe and medial, inferiorly-anteriorly along the medial wall. The decline of selectivity and laterality along these directions provides evidence for hierarchical gradients. In view of the anatomical segregation of these three directions, the multiplicity of body representations in each region and the hierarchical gradients in our findings, we propose that as in the visual and auditory domains, these directions are streams of somatosensory information processing.

The relationship between eating disorder psychopathology and sexuality: etiological factors and implications for treatment

PURPOSE OF REVIEW

There is a remarkable overlap between eating disorders and sexual problems, both in terms of sexual dysfunctions and risky sexual behaviors. This systematic review of the recent literature aimed at clarifying the nature of this relationship in terms of psychopathological meaning.

RECENT FINDINGS

Body image disturbance, and particularly body dissatisfaction and embodiment disorder, emerged as shared psychopathological dimensions between eating disorder symptoms and sexual dysfunctions. Interpersonal difficulties, a disturbed intimacy and insecure attachment style, but not a history of sexual abuse per se, resulted to play a pivotal role in the interconnection between eating disorder psychopathology and sexual dysfunctions. On the other hand, several studies confirmed the association between eating disorder symptoms and risky sexual behaviors, which has been explained in terms of several common psychopathological dimensions, including impulsivity and addiction.

SUMMARY

Sexuality is deeply interconnected with eating disorder psychopathology, and it should be considered a fundamental aspect in managing these disorders. An accurate assessment of sexual function might allow to characterize etiological information (e.g., sexual abuse) and maintaining factors (embodiment disorder and emotion dysregulation). Accordingly, the recovery of a good sexuality should be considered a crucial signal of recovery.