Visual feedback decoding during bimanual circle drawing

The between-hand interference during bimanual tasks is a consequence of the connection between the neural controllers of movement. Previous studies showed the existence of an asymmetric between-hand interference (caused by neural cross talk) when different kinematics plans were to be executed by each hand or when only one was visually guided and received perturbed visual feedback. Here, in continuous bimanual circle drawing tasks, we investigated if the central nervous system (CNS) can benefit from visual composite feedback, i.e., a weighted sum of hands' positions presented for the visually guided hand, to control the nonvisible hand. Our results demonstrated improvement in the nonvisible nondominant hand (NDH) performance in the presence of the composite feedback. When NDH was visually guided, the dominant hand's (DH) performance during asymmetric drawing deteriorated, whereas its performance during symmetric drawing improved. This indicates that the CNS's ability to leverage composite feedback, which can be the result of decoding the nonvisible hand positional information from the composite feedback, is task-dependent and can be asymmetric. Also, the nonvisible hand's performance degraded when DH or NDH was visually guided with amplified error feedback. The results of the amplified feedback condition do not strongly support the asymmetry of the interference during asymmetric circle drawing. Comparing muscle activations in the asymmetric experiment, we concluded that the observed kinematic differences were not due to alternation in muscle co-contractions.NEW & NOTEWORTHY Many daily activities involve bimanual coordination while simultaneous movement of the hands may result in interference with their movements. Here, we studied whether the central nervous system could use the relevant information in composite feedback, i.e., a weighted sum of positional information of nonvisible and visible hands, to improve the movement of the nonvisible hand. Our results suggest the ability to decode and associate task-relevant information from the composite feedback.

Functional MRI Lateralization [M1] of dlPFC and Implications for Transcranial Magnetic Stimulation (TMS) Targeting

The present study investigates a potential method of optimizing effective strategies for the functional lateralization of the dorsolateral prefrontal cortex (dlPFC) while in a scanner. Effective hemisphere lateralization of the dlPFC is crucial for lowering the functional risks connected to specific interventions (such as neurosurgery and transcranial magnetic stimulation (TMS), as well as increasing the effectiveness of a given intervention by figuring out the optimal location. This task combines elements of creative problem solving, executive decision making based on an internal rule set, and working memory. A retrospective analysis was performed on a total of 58 unique participants (34 males, 24 females, Mage = 42.93 years, SDage = 16.38). Of these participants, 47 were classified as right-handed, 7 were classified as left-handed, and 4 were classified as ambidextrous, according to the Edinburgh Handedness Inventory. The imaging data were qualitatively judged by two trained, blinded investigators (neurologist and neuropsychologist) for dominant handedness (primary motor cortex) and dominant dorsolateral prefrontal cortex (dlPFC). The results demonstrated that 21.4% of right-handed individuals showed a dominant dlPFC localized to the right hemisphere rather than the assumed left, and 16.7% of left-handers were dominant in their left hemisphere. The task completed in the scanner might be an efficient method for localizing a potential dlPFC target for the purpose of brain stimulation (e.g., TMS), though further study replications are needed to extend and validate these findings.

Characteristics of cognitive function in patients with cerebellar infarction and its association with lesion location

Objective: This study aimed to explore the characteristics of cognitive function in patients with cerebellar infarction and its association with lesion location. Methods: Forty-five patients with isolated cerebellar infarction were collected in the Department of Neurology, Beijing Tiantan Hospital. Thirty healthy controls were recruited matched by age and education. Global cognitive function was evaluated by using Addenbrooke's Cognitive Examination version III (ACE-III). An extensive neuropsychological assessment battery was also tested to evaluate the characteristics of each cognitive domain. 3D slicer software was used to draw the lesion, and evaluate the lesions' volume, side, and location. Group analysis was used to compare the differences in cognitive performance between patients and healthy controls, and patients with left and right cerebellar hemisphere infarction. Spearman analysis was used to explore the correlation between cognitive function and lesion volume. We also subdivided each patient's lesions according to the cerebellar atlas to identify the specific cerebellar location related to cognitive decline. Results: Patients with cerebellar infarction had a lower ACE-III score compared with the healthy group (87.9 ± 6.2 vs. 93.7 ± 2.9, p < 0.001), and 22 (48.9%) patients were diagnosed with cognitive impairment. The z-transformed score of attention and executive function in the patients' group was -0.9 ± 1.4 and -0.8 ± 1.0 respectively, with 19 (43.2%) and 23 (56.4%) patients impaired. Compared with healthy controls, the relative risk ratio with 95% confidence interval (CI) for impairment in attention and executive function were 3.24 (1.22-8.57) and 3.39 (1.45-7.89). However, only 10 (22.1%) patients showed impairment in more than two cognitive domains. Compared with the left lesion group, patients with right cerebellar infarction showed significantly impaired executive function (-1.1 ± 0.3 vs. -0.5 ± 0.2, p = 0.01). And the cerebellar posterior lobe regions, especially lobules VI, VIII, and IX, were explored to have lower cognitive performance. Furthermore, lesion volume was identified to be associated with the ACE-III score (r = -0.37, p = 0.04). Conclusion: We identified that cerebellar involvement in cognition, especially in attention processing and executive function. Cerebellar right-sided lateralization of cognition and functional topography were also revealed in the current study.

Lateralization of short-term memory in the frontal cortex

Despite essentially symmetric structures in mammalian brains, the left and right hemispheres do not contribute equally to certain cognitive functions. How both hemispheres interact to cause this asymmetry remains unclear. Here, we study this question in the anterior lateral motor cortex (ALM) of mice performing five versions of a tactile-based decision-making task with a short-term memory (STM) component. Unilateral inhibition of ALM produces variable behavioral deficits across tasks, with the left, right, or both ALMs playing critical roles in STM. Neural activity and its encoding capability are similar across hemispheres, despite that only one hemisphere dominates in behavior. Inhibition of the dominant ALM disrupts encoding capability in the non-dominant ALM, but not vice versa. Variable behavioral deficits are predicted by the influence on contralateral activity across sessions, mice, and tasks. Together, these results reveal that the left and right ALM interact asymmetrically, leading to their differential contributions to STM.

Callosal Fiber Length Scales with Brain Size According to Functional Lateralization, Evolution, and Development

Brain size significantly impacts the organization of white matter fibers. Fiber length scaling, the degree to which fiber length varies according to brain size, was overlooked. We investigated how fiber lengths within the corpus callosum, the most prominent white matter tract, vary according to brain size. The results showed substantial variation in length scaling among callosal fibers, replicated in two large healthy cohorts (∼2000 human subjects, including both sexes). The underscaled callosal fibers mainly connected the precentral gyrus and parietal cortices, whereas the overscaled callosal fibers mainly connected the prefrontal cortices. The variation in such length scaling was biologically meaningful: larger scaling corresponded to larger neurite density index but smaller fractional anisotropy values; cortical regions connected by the callosal fibers with larger scaling were more lateralized functionally as well as phylogenetically and ontogenetically more recent than their counterparts. These findings highlight an interaction between interhemispheric communication and organizational and adaptive principles underlying brain development and evolution.SIGNIFICANCE STATEMENT Brain size varies across evolution, development, and individuals. Relative to small brains, the neural fiber length in large brains is inevitably increased, but the degree of such increase may differ between fiber tracts. Such a difference, if it exists, is valuable for understanding adaptive neural principles in large versus small brains during evolution and development. The present study showed a substantial difference in the length increase between the callosal fibers that connect the two hemispheres, replicated in two large healthy cohorts. Together, our study demonstrates that reorganization of interhemispheric fibers length according to brain size is intrinsically related to fiber composition, functional lateralization, cortical myelin content, and evolutionary and developmental expansion.

Hemispheric Lateralization of Visuospatial Attention Is Independent of Language Production on Right-Handers: Evidence From Functional Near-Infrared Spectroscopy

It is well-established that visuospatial attention is mainly lateralized to the right hemisphere, whereas language production is mainly left-lateralized. However, there is a significant controversy regarding how these two kinds of lateralization interact with each other. The present research used functional near-infrared spectroscopy (fNIRS) to examine whether visuospatial attention is indeed right-lateralized, whereas language production is left-lateralized, and more importantly, whether the extent of lateralization in the visuospatial task is correlated with that in the task involving language. Specifically, fifty-two healthy right-handed participants participated in this study. Multiple-channel fNIRS technique was utilized to record the cerebral hemodynamic changes when participants were engaged in naming objects depicted in pictures (the picture naming task) or judging whether a presented line was bisected correctly (the landmark task). The degree of hemispheric lateralization was quantified according to the activation difference between the left and right hemispheres. We found that the picture-naming task predominantly activated the inferior frontal gyrus (IFG) of the left hemisphere. In contrast, the landmark task predominantly activated the inferior parietal sulcus (IPS) and superior parietal lobule (SPL) of the right hemisphere. The quantitative calculation of the laterality index also showed a left-lateralized distribution for the picture-naming task and a right-lateralized distribution for the landmark task. Intriguingly, the correlation analysis revealed no significant correlation between the laterality indices of these two tasks. Our findings support the independent hypothesis, suggesting that different cognitive tasks may engender lateralized processing in the brain, but these lateralized activities may be independent of each other. Meanwhile, we stress the importance of handedness in understanding the relationship between functional asymmetries. Methodologically, we demonstrated the effectiveness of using the multichannel fNIRS technique to investigate the hemispheric specialization of different cognitive tasks and their lateralization relations between different tasks. Our findings and methods may have important implications for future research to explore lateralization-related issues in individuals with neural pathologies.

Comparative Analysis of Lateral Preferences in Patients With Resistant Schizophrenia

BACKGROUND

Schizophrenia is a chronic brain disorder of diverse etiology and clinical presentation. Despite the expansion of treatment methods, between 30 and 50% of cases remain resistant to treatment. In patients with schizophrenia, specifics in the dominant lateralization in the brain function have been discovered. This gave a reason to seek the relation between functional lateralization and the effect of treatment.

METHODS

Of the 105 people observed with schizophrenia, 45 (42.9%) were treatment resistant, and 60 (57.1%) were considered responders. We compared functional lateralization (hand, foot, and eye) between the two groups. Handedness was ascertained by using the Edinburgh Handedness Inventory. The assessment was made at 12 weeks of treatment.

RESULTS

Of all patients with schizophrenia, 41.89% have mixed lateralization, 53.34% are right winged, and 4.76% of the patients are left winged. Resistance of the symptoms shows that 26 (57.78%) are cross-dominated, 18 (40%) are right winged, and 1 (2.22%) is left winged. In patients with clinical remission, 18 (30%) are of mixed dominance, 38 (63.33%) are right winged, and 4 (6.66%) are left winged. From the results for the separate lateralization of the hand, foot, and eye, we found a significant difference only in terms of the dominance of the eye. In 44 (41.9%) of the patients, we found dominance of the left eye. In patients with resistance, the percentage established by us is higher-at 26 (57.8%). These results indicate that the increased percentage of mixed dominance in patients with schizophrenia is mainly due to left-sided lateralization of the eye, especially in those with resistance to treatment.

CONCLUSION

We find an increased number of patients with cross-dominance left eye dominance in patients with schizophrenia. Cross-dominance and left eye dominance are associated with a higher probability of symptom resistance than other forms of lateralization (left-handed or right-handed). The high percentage of cross-dominance is due to the high percentage of left-sided dominance of the eye.

Mental Shopping Calculations: A Transcranial Magnetic Stimulation Study

One of the most critical skills behind consumer's behavior is the ability to assess whether a price after a discount is a real bargain. Yet, the neural underpinnings and cognitive mechanisms associated with such a skill are largely unknown. While there is general agreement that the posterior parietal cortex (PPC) on the left is critical for mental calculations, and there is also recent repetitive transcranial magnetic stimulation (rTMS) evidence pointing to the supramarginal gyrus (SMG) of the right PPC as crucial for consumer-like arithmetic (e.g., multi-digit mental addition or subtraction), it is still unknown whether SMG is involved in calculations of sale prices. Here, we show that the neural mechanisms underlying discount arithmetic characteristic for shopping are different from complex addition or subtraction, with discount calculations engaging left SMG more. We obtained these outcomes by remodeling our laboratory to resemble a shop and asking participants to calculate prices after discounts (e.g., $8.80-25 or $4.80-75%), while stimulating left and right SMG with neuronavigated rTMS. Our results indicate that such complex shopping calculations as establishing the price after a discount involve SMG asymmetrically, whereas simpler calculations such as price addition do not. These findings have some consequences for neural models of mathematical cognition and shed some preliminary light on potential consumer's behavior in natural settings.

Sex differences in the functional lateralization of emotion and decision making in the human brain

Dating back to the case of Phineas Gage, decades of neuropsychological research have shown that the ventromedial prefrontal cortex (vmPFC) is crucial to both real-world social functioning and abstract decision making in the laboratory (see, e.g., Stuss et al., ; Bechara et al., 1994; Damasio et al., ). Previous research has shown that the relationship between the laterality of individuals' vmPFC lesions and neuropsychological performance is moderated by their sex, whereby there are more severe social, emotional, and decision-making impairments in men with right-side vmPFC lesions and in women with left-side vmPFC lesions (Tranel et al., 2005; Sutterer et al., 2015). We conducted a selective review of studies examining the effect of vmPFC lesions on emotion and decision making and found further evidence of sex-related differences in the lateralization of function not only in the vmPFC but also in other neurological structures associated with decision making and emotion. This Mini-Review suggests that both sex and laterality effects warrant more careful consideration in the scientific literature. © 2016 Wiley Periodicals, Inc.

Lateralization of Eye Use in Cuttlefish: Opposite Direction for Anti-Predatory and Predatory Behaviors

Vertebrates with laterally placed eyes typically exhibit preferential eye use for ecological activities such as scanning for predators or prey. Processing visual information predominately through the left or right visual field has been associated with specialized function of the left and right brain. Lateralized vertebrates often share a general pattern of lateralized brain function at the population level, whereby the left hemisphere controls routine behaviors and the right hemisphere controls emergency responses. Recent studies have shown evidence of preferential eye use in some invertebrates, but whether the visual fields are predominately associated with specific ecological activities remains untested. We used the European common cuttlefish, Sepia officinalis, to investigate whether the visual field they use is the same, or different, during anti-predatory, and predatory behavior. To test for lateralization of anti-predatory behavior, individual cuttlefish were placed in a new environment with opaque walls, thereby obliging them to choose which eye to orient away from the opaque wall to scan for potential predators (i.e., vigilant scanning). To test for lateralization of predatory behavior, individual cuttlefish were placed in the apex of an isosceles triangular arena and presented with two shrimp in opposite vertexes, thus requiring the cuttlefish to choose between attacking a prey item to the left or to the right of them. Cuttlefish were significantly more likely to favor the left visual field to scan for potential predators and the right visual field for prey attack. Moreover, individual cuttlefish that were leftward directed for vigilant scanning were predominately rightward directed for prey attack. Lateralized individuals also showed faster decision-making when presented with prey simultaneously. Cuttlefish appear to have opposite directions of lateralization for anti-predatory and predatory behavior, suggesting that there is functional specialization of each optic lobe (i.e., brain structures implicated in visual processing). These results are discussed in relation to the role of lateralized brain function and the evolution of population level lateralization.

A cross-linguistic evaluation of script-specific effects on fMRI lateralization in late second language readers

Behavioral and neuroimaging studies have provided evidence that reading is strongly left lateralized, and the degree of this pattern of functional lateralization can be indicative of reading competence. However, it remains unclear whether functional lateralization differs between the first (L1) and second (L2) languages in bilingual L2 readers. This question is particularly important when the particular script, or orthography, learned by the L2 readers is markedly different from their L1 script. In this study, we quantified functional lateralization in brain regions involved in visual word recognition for participants' L1 and L2 scripts, with a particular focus on the effects of L1–L2 script differences in the visual complexity and orthographic depth of the script. Two different groups of late L2 learners participated in an fMRI experiment using a visual one-back matching task: L1 readers of Japanese who learnt to read alphabetic English and L1 readers of English who learnt to read both Japanese syllabic Kana and logographic Kanji. The results showed weaker leftward lateralization in the posterior lateral occipital complex (pLOC) for logographic Kanji compared with syllabic and alphabetic scripts in both L1 and L2 readers of Kanji. When both L1 and L2 scripts were non-logographic, where symbols are mapped onto sounds, functional lateralization did not significantly differ between L1 and L2 scripts in any region, in any group. Our findings indicate that weaker leftward lateralization for logographic reading reflects greater requirement of the right hemisphere for processing visually complex logographic Kanji symbols, irrespective of whether Kanji is the readers' L1 or L2, rather than characterizing additional cognitive efforts of L2 readers. Finally, brain-behavior analysis revealed that functional lateralization for L2 visual word processing predicted L2 reading competency.

On the planum temporale lateralization in suprasegmental speech perception: evidence from a study investigating behavior, structure, and function

This study combines functional and structural magnetic resonance imaging to test the "asymmetric sampling in time" (AST) hypothesis, which makes assertions about the symmetrical and asymmetrical representation of speech in the primary and nonprimary auditory cortex. Twenty-three volunteers participated in this parametric clustered-sparse fMRI study. The availability of slowly changing acoustic cues in spoken sentences was systematically reduced over continuous segments with varying lengths (100, 150, 200, 250 ms) by utilizing local time-reversion. As predicted by the hypothesis, functional lateralization in Heschl's gyrus could not be observed. Lateralization in the planum temporale and posterior superior temporal gyrus shifted towards the right hemisphere with decreasing suprasegmental temporal integrity. Cortical thickness of the planum temporale was automatically measured. Participants with an L > R cortical thickness performed better on the in-scanner auditory pattern-matching task. Taken together, these findings support the AST hypothesis and provide substantial novel insight into the division of labor between left and right nonprimary auditory cortex functions during comprehension of spoken utterances. In addition, the present data yield support for a structural-behavioral relationship in the nonprimary auditory cortex.

Right and left perisylvian cortex and left inferior frontal cortex mediate sentence-level rhyme detection in spoken language as revealed by sparse fMRI

In this study, we used functional magnetic resonance imaging to investigate the neural basis of auditory rhyme processing at the sentence level in healthy adults. In an explicit rhyme detection task, participants were required to decide whether the ending syllable of a metrically spoken pseudosentence rhymed or not. Participants performing this task revealed bilateral activation in posterior-superior temporal gyri with a much more extended cluster of activation in the right hemisphere. These findings suggest that the right hemisphere primarily supports suprasegmental tasks, such as the segmentation of speech into syllables; thus, our findings are in line with the "asymmetric sampling in time" model suggested by Poeppel (: Speech Commun 41:245-255). The direct contrast between rhymed and nonrhymed trials revealed a stronger BOLD response for rhymed trials in the frontal operculum and the anterior insula of the left hemisphere. Our results suggest an involvement of these frontal regions not only in articulatory rehearsal processes, but especially in the detection of a matching syllable, as well as in the execution of rhyme judgment.

Functional hemispheric specialization in processing phonemic and prosodic auditory changes in neonates

This study focuses on the early cerebral base of speech perception by examining functional lateralization in neonates for processing segmental and suprasegmental features of speech. For this purpose, auditory evoked responses of full-term neonates to phonemic and prosodic contrasts were measured in their temporal area and part of the frontal and parietal areas using near-infrared spectroscopy (NIRS). Stimuli used here were phonemic contrast /itta/ and /itte/ and prosodic contrast of declarative and interrogative forms /itta/ and /itta?/. The results showed clear hemodynamic responses to both phonemic and prosodic changes in the temporal areas and part of the parietal and frontal regions. In particular, significantly higher hemoglobin (Hb) changes were observed for the prosodic change in the right temporal area than for that in the left one, whereas Hb responses to the vowel change were similarly elicited in bilateral temporal areas. However, Hb responses to the vowel contrast were asymmetrical in the parietal area (around supra marginal gyrus), with stronger activation in the left. These results suggest a specialized function of the right hemisphere in prosody processing, which is already present in neonates. The parietal activities during phonemic processing were discussed in relation to verbal-auditory short-term memory. On the basis of this study and previous studies on older infants, the developmental process of functional lateralization from birth to 2 years of age for vowel and prosody was summarized.

Assessing signal-driven mechanisms in neonates: brain responses to temporally and spectrally different sounds

Past studies have found that, in adults, the acoustic properties of sound signals (such as fast versus slow temporal features) differentially activate the left and right hemispheres, and some have hypothesized that left-lateralization for speech processing may follow from left-lateralization to rapidly changing signals. Here, we tested whether newborns’ brains show some evidence of signal-specific lateralization responses using near-infrared spectroscopy (NIRS) and auditory stimuli that elicits lateralized responses in adults, composed of segments that vary in duration and spectral diversity. We found significantly greater bilateral responses of oxygenated hemoglobin (oxy-Hb) in the temporal areas for stimuli with a minimum segment duration of 21 ms, than stimuli with a minimum segment duration of 667 ms. However, we found no evidence for hemispheric asymmetries dependent on the stimulus characteristics. We hypothesize that acoustic-based functional brain asymmetries may develop throughout early infancy, and discuss their possible relationship with brain asymmetries for language.

Training to use voice onset time as a cue to talker identification induces a left-ear/right-hemisphere processing advantage

We examined the effect of perceptual training on a well-established hemispheric asymmetry in speech processing. Eighteen listeners were trained to use a within-category difference in voice onset time (VOT) to cue talker identity. Successful learners (n=8) showed faster response times for stimuli presented only to the left ear than for those presented only to the right. The development of a left-ear/right-hemisphere advantage for processing a prototypically phonetic cue supports a model of speech perception in which lateralization is driven by functional demands (talker identification vs. phonetic categorization) rather than by acoustic stimulus properties alone.