Somatotopic mapping of the human primary motor cortex with functional magnetic resonance imaging

Organization of the human cerebral cortex estimated within individuals: networks, global topography, and function

The cerebral cortex is populated by specialized regions that are organized into networks. Here we estimated networks from functional MRI (fMRI) data in intensively sampled participants. The procedure was developed in two participants (scanned 31 times) and then prospectively applied to 15 participants (scanned 8-11 times). Analysis of the networks revealed a global organization. Locally organized first-order sensory and motor networks were surrounded by spatially adjacent second-order networks that linked to distant regions. Third-order networks possessed regions distributed widely throughout association cortex. Regions of distinct third-order networks displayed side-by-side juxtapositions with a pattern that repeated across multiple cortical zones. We refer to these as supra-areal association megaclusters (SAAMs). Within each SAAM, two candidate control regions were adjacent to three separate domain-specialized regions. Response properties were explored with task data. The somatomotor and visual networks responded to body movements and visual stimulation, respectively. Second-order networks responded to transients in an oddball detection task, consistent with a role in orienting to salient events. The third-order networks, including distinct regions within each SAAM, showed two levels of functional specialization. Regions linked to candidate control networks responded to working memory load across multiple stimulus domains. The remaining regions dissociated across language, social, and spatial/episodic processing domains. These results suggest that progressively higher-order networks nest outward from primary sensory and motor cortices. Within the apex zones of association cortex, there is specialization that repeatedly divides domain-flexible from domain-specialized regions. We discuss implications of these findings, including how repeating organizational motifs may emerge during development.NEW & NOTEWORTHY The organization of cerebral networks was estimated within individuals with intensive, repeat sampling of fMRI data. A hierarchical organization emerged in each individual that delineated first-, second-, and third-order cortical networks. Regions of distinct third-order association networks consistently exhibited side-by-side juxtapositions that repeated across multiple cortical zones, with clear and robust functional specialization among the embedded regions.

How do visual, auditory and motor dual-tasking each affect swallowing and chewing function?

BACKGROUND

It can be challenging to perform a second task at the same time as swallowing.

OBJECTIVE(S)

The study aimed to investigate the effect of visual, auditory and motor dual-tasking on swallowing and chewing function in healthy young adults.

METHOD

Right-handed healthy adults without any psychological and cognitive problems were included in the study. Swallowing was evaluated based on the dysphagia limit in different liquid textures such as water and nectar consistencies, and chewing was evaluated by the Test of Masticating and Swallowing Solids. For the second task, visual and auditory performance was assessed using reaction time, and the motor performance was assessed using a bilateral tapping task. Assessments were performed in two steps: baseline and dual-task. For baseline, all evaluation methods were applied individually. After completing the baseline assessment, dual-task assessment were carried out the following day. For dual-task assessment, the swallowing and chewing tasks were performed simultaneously with visual, auditory and motor tasks.

RESULTS

Results showed a significant decrease in dysphagia limit in the nectar consistency, and significant increase in chewing time, visual reaction time and tapping rate (right-left) when compared to baseline and dual-task conditions (χ2(3) = 9.61, p = .02; χ2(3) = 9.02, p = .02; χ2(3) = 28.09, p < .001; χ2(3) = 28.97, p < .001; χ2(3) = 21.56, p < .001, respectively). However, there were no differences in dysphagia limit in the water and auditory reaction time compared to baseline and dual-task conditions (χ2(3) = 3.18, p = .36; χ2(3) = 2.56, p = .50, respectively).

CONCLUSION

Results shedding light on how simultaneous dual tasks can influence swallowing and chewing. Dual-tasking cause a decrease in both swallowing/chewing and the visual/motor performances. These results may provide valuable information for designing interventions or strategies aimed at improving or maintaining optimal swallowing and chewing during in various populations during daily life.

Volitional muscle activation intensifies neuronal processing of proprioceptive afference in the primary sensorimotor cortex: an EEG study

Proprioception refers to the ability to perceive the position and movement of body segments in space. The cortical aspects of the proprioceptive afference from the body can be investigated using corticokinematic coherence (CKC). CKC accurately quantifies the degree of coupling between cortical activity and limb kinematics, especially if precise proprioceptive stimulation of evoked movements is used. However, there is no evidence on how volitional muscle activation during proprioceptive stimulation affects CKC strength. Twenty-five healthy volunteers (28.8 ± 7 yr, 11 females) participated in the experiment, which included electroencephalographic (EEG), electromyographic (EMG), and kinematic recordings. Ankle-joint rotations (2-Hz) were elicited through a movement actuator in two conditions: passive condition with relaxed ankle and active condition with constant 5-Nm plantar flexion exerted during the stimulation. In total, 6 min of data were recorded per condition. CKC strength was defined as the maximum coherence value among all the EEG channels at the 2-Hz movement frequency for each condition separately. Both conditions resulted in significant CKC peaking at the Cz electrode over the foot area of the primary sensorimotor (SM1) cortex. Stronger CKC was found for the active (0.13 ± 0.14) than the passive (0.03 ± 0.04) condition (P < 0.01). The results indicated that volitional activation of the muscles intensifies the neuronal proprioceptive processing in the SM1 cortex. This finding could be explained both by peripheral sensitization of the ankle joint proprioceptors and central modulation of the neuronal proprioceptive processing at the spinal and cortical levels.NEW & NOTEWORTHY The current study is the first to investigate the effect of volitional muscle activation on CKC-based assessment of cortical proprioception of the ankle joint. Results show that the motor efference intensifies the neuronal processing of proprioceptive afference of the ankle joint. This is a significant finding as it may extend the use of CKC method during active tasks to further evaluate the motor efference-proprioceptive afference relationship and the related adaptations to exercise, rehabilitation, and disease.

Nordic Walking in Water on Cerebrovascular Reactivity and Cognitive Function in Elderly Patients with Type 2 Diabetes

INTRODUCTION

Aquatic Nordic walking (ANW) is a novel whole-body low-impact exercise that can be practiced by a variety of older adults with chronic conditions. However, its efficacy on several aspects of health is largely unknown.

PURPOSE

This study aimed to determine the effects of regular ANW on glycemic control and vascular function in older adults with type 2 diabetes and mild cognitive impairment.

METHODS

Thirty-three older adults with type 2 diabetes age 60-75 yr were randomly allocated to nonexercising control ( n = 17) or ANW ( n = 17) groups. Nordic walking was performed in a pool at water temperature of 34°C-36°C, three times per week for 12 wk.

RESULTS

Measures of functional physical fitness including chair stand, timed up and go, chair sit and reach, reach and back scratch, and 6-min walk test scores were all improved after ANW (all P < 0.05). Plasma glucose, glycosylated hemoglobin, and homeostasis model assessment of insulin resistance decreased (all P < 0.05) in ANW. Vascular reactivity as assessed by brachial flow-mediated dilation increased, and arterial stiffness as assessed by brachial-ankle pulse wave velocity decreased in ANW (all P < 0.05). No significant changes were observed in the control group. Middle cerebral artery pulsatility index decreased with ANW under normocapnia condition ( P < 0.05). Cerebrovascular conductance increased with ANW under hypercapnia condition. Montreal Cognitive Assessment score increased in the ANW group ( P < 0.001). Changes in Montreal Cognitive Assessment scores were positively associated with corresponding changes in brain-derived neurotrophic factor ( r = 0.540, P = 0.031).

CONCLUSIONS

Nordic walking in water was a safe and effective innovative exercise modality to improve glycemic control, vascular function, physical fitness, cerebrovascular reactivity, and cognitive function in older adults with type 2 diabetes.

Within-Individual Organization of the Human Cerebral Cortex: Networks, Global Topography, and Function

The human cerebral cortex is populated by specialized regions that are organized into networks. Here we estimated networks using a Multi-Session Hierarchical Bayesian Model (MS-HBM) applied to intensively sampled within-individual functional MRI (fMRI) data. The network estimation procedure was initially developed and tested in two participants (each scanned 31 times) and then prospectively applied to 15 new participants (each scanned 8 to 11 times). Detailed analysis of the networks revealed a global organization. Locally organized first-order sensory and motor networks were surrounded by spatially adjacent second-order networks that also linked to distant regions. Third-order networks each possessed regions distributed widely throughout association cortex. Moreover, regions of distinct third-order networks displayed side-by-side juxtapositions with a pattern that repeated similarly across multiple cortical zones. We refer to these as Supra-Areal Association Megaclusters (SAAMs). Within each SAAM, two candidate control regions were typically adjacent to three separate domain-specialized regions. Independent task data were analyzed to explore functional response properties. The somatomotor and visual first-order networks responded to body movements and visual stimulation, respectively. A subset of the second-order networks responded to transients in an oddball detection task, consistent with a role in orienting to salient or novel events. The third-order networks, including distinct regions within each SAAM, showed two levels of functional specialization. Regions linked to candidate control networks responded to working memory load across multiple stimulus domains. The remaining regions within each SAAM did not track working memory load but rather dissociated across language, social, and spatial / episodic processing domains. These results support a model of the cerebral cortex in which progressively higher-order networks nest outwards from primary sensory and motor cortices. Within the apex zones of association cortex there is specialization of large-scale networks that divides domain-flexible from domain-specialized regions repeatedly across parietal, temporal, and prefrontal cortices. We discuss implications of these findings including how repeating organizational motifs may emerge during development.

A machine learning approach towards the differentiation between interoceptive and exteroceptive attention

Interoception, the representation of the body's internal state, plays a central role in emotion, motivation and wellbeing. Interoceptive sensibility, the ability to engage in sustained interoceptive awareness, is particularly relevant for mental health but is exclusively measured via self-report, without methods for objective measurement. We used machine learning to classify interoceptive sensibility by contrasting using data from a randomized control trial of interoceptive training, with functional magnetic resonance imaging assessment before and after an 8-week intervention (N = 44 scans). The neuroimaging paradigm manipulated attention targets (breath vs. visual stimuli) and reporting demands (active reporting vs. passive monitoring). Machine learning achieved high accuracy in distinguishing between interoceptive and exteroceptive attention, both for within-session classification (~80% accuracy) and out-of-sample classification (~70% accuracy), revealing the reliability of the predictions. We then explored the classifier potential for 'reading out' mental states in a 3-min sustained interoceptive attention task. Participants were classified as actively engaged about half of the time, during which interoceptive training enhanced their ability to sustain interoceptive attention. These findings demonstrate that interoceptive and exteroceptive attention is distinguishable at the neural level; these classifiers may help to demarcate periods of interoceptive focus, with implications for developing an objective marker for interoceptive sensibility in mental health research.

Functional mapping of sensorimotor activation in the human thalamus at 9.4 Tesla

Although the thalamus is perceived as a passive relay station for almost all sensory signals, the function of individual thalamic nuclei remains unresolved. In the present study, we aimed to identify the sensorimotor nuclei of the thalamus in humans using task-based fMRI at a field strength of 9.4T by assessing the individual subject-specific sensorimotor BOLD response during a combined active motor (finger-tapping) and passive sensory (tactile-finger) stimulation. We demonstrate that both tasks increase BOLD signal response in the lateral nuclei group (VPL, VA, VLa, and VLp), and in the pulvinar nuclei group (PuA, PuM, and PuL). Finger-tapping stimuli evokes a stronger BOLD response compared to the tactile stimuli, and additionally engages the intralaminar nuclei group (CM and Pf). In addition, our results demonstrate reproducible thalamic nuclei activation during motor and tactile stimuli. This work provides important insight into understanding the function of individual thalamic nuclei in processing various input signals and corroborates the benefits of using ultra-high-field MR scanners for functional imaging of fine-scale deeply located brain structures.

Laterality Index Calculations in a Control Study of Functional Near Infrared Spectroscopy

Hemispheric dominance has been used to understand the influence of central and peripheral neural damage on the motor function of individuals with stroke, cerebral palsy, and limb loss. It has been well established that greater activation occurs in the contralateral hemisphere to the side of the body used to perform the task. However, there is currently a large variability in calculation procedures for brain laterality when using functional near-infrared spectroscopy (fNIRS) as a non-invasive neuroimaging tool. In this study, we used fNIRS to measure brain activity over the left and right sensorimotor cortices while participants (n = 20, healthy and uninjured) performed left and right-hand movement tasks. Then, we analyzed the fNIRS data using two different processing pipelines (block averaging or general linear model [GLM]), two different criteria of processing for negative values (include all beta values or include only positive beta values), and three different laterality index (LI) formulas. The LI values produced using the block averaging analysis indicated an expected contralateral dominance with some instances of bilateral dominance, which agreed with the expected contralateral activation. However, the inclusion criteria nor the LI formulas altered the outcome. The LI values produced using the GLM analysis displayed a robust left hemisphere dominance regardless of the hand performing the task, which disagreed with the expected contralateral activation but did provide instances of correctly identifying brain laterality. In conclusion, both analysis pipelines were able to correctly determine brain laterality, but processes to account for negative beta values were recommended especially when utilizing the GLM analysis to determine brain laterality.

An integrated resource for functional and structural connectivity of the marmoset brain

Comprehensive integration of structural and functional connectivity data is required to model brain functions accurately. While resources for studying the structural connectivity of non-human primate brains already exist, their integration with functional connectivity data has remained unavailable. Here we present a comprehensive resource that integrates the most extensive awake marmoset resting-state fMRI data available to date (39 marmoset monkeys, 710 runs, 12117 mins) with previously published cellular-level neuronal tracing data (52 marmoset monkeys, 143 injections) and multi-resolution diffusion MRI datasets. The combination of these data allowed us to (1) map the fine-detailed functional brain networks and cortical parcellations, (2) develop a deep-learning-based parcellation generator that preserves the topographical organization of functional connectivity and reflects individual variabilities, and (3) investigate the structural basis underlying functional connectivity by computational modeling. This resource will enable modeling structure-function relationships and facilitate future comparative and translational studies of primate brains.

An fMRI dataset for whole-body somatotopic mapping in humans

The somatotopic representation of the body is a well-established organizational principle in the human brain. Classic invasive direct electrical stimulation for somatotopic mapping cannot be used to map the whole-body topographical representation of healthy individuals. Functional magnetic resonance imaging (fMRI) has become an indispensable tool for the noninvasive investigation of somatotopic organization of the human brain using voluntary movement tasks. Unfortunately, body movements during fMRI scanning often cause large head motion artifacts. Consequently, there remains a lack of publicly accessible fMRI datasets for whole-body somatotopic mapping. Here, we present public high-resolution fMRI data to map the somatotopic organization based on motor movements in a large cohort of healthy adults (N = 62). In contrast to previous studies that were mostly designed to distinguish few body representations, most body parts are considered, including toe, ankle, leg, finger, wrist, forearm, upper arm, jaw, lip, tongue, and eyes. Moreover, the fMRI data are denoised by combining spatial independent component analysis with manual identification to clean artifacts from head motion associated with body movements.

Comprehensive decoding mental processes from Web repositories of functional brain images

Associating brain systems with mental processes requires statistical analysis of brain activity across many cognitive processes. These analyses typically face a difficult compromise between scope-from domain-specific to system-level analysis-and accuracy. Using all the functional Magnetic Resonance Imaging (fMRI) statistical maps of the largest data repository available, we trained machine-learning models that decode the cognitive concepts probed in unseen studies. For this, we leveraged two comprehensive resources: NeuroVault-an open repository of fMRI statistical maps with unconstrained annotations-and Cognitive Atlas-an ontology of cognition. We labeled NeuroVault images with Cognitive Atlas concepts occurring in their associated metadata. We trained neural networks to predict these cognitive labels on tens of thousands of brain images. Overcoming the heterogeneity, imbalance and noise in the training data, we successfully decoded more than 50 classes of mental processes on a large test set. This success demonstrates that image-based meta-analyses can be undertaken at scale and with minimal manual data curation. It enables broad reverse inferences, that is, concluding on mental processes given the observed brain activity.

Task-Based Functional Connectivity and Blood-Oxygen-Level-Dependent Activation During Within-Scanner Performance of Lumbopelvic Motor Tasks: A Functional Magnetic Resonance Imaging Study

There are a limited number of neuroimaging investigations into motor control of the lumbopelvic musculature. Most investigation examining motor control of the lumbopelvic musculature utilize transcranial magnetic stimulation (TMS) and focus primarily on the motor cortex. This has resulted in a dearth of knowledge as it relates to how other regions of the brain activate during lumbopelvic movement. Additionally, task-based functional connectivity during lumbopelvic movements has not been well elucidated. Therefore, we used functional magnetic resonance imaging (fMRI) to examine brain activation and ROI-to-ROI task-based functional connectivity in 19 healthy individuals (12 female, age 29.8 ± 4.5 years) during the performance of three lumbopelvic movements: modified bilateral bridge, left unilateral bridge, and right unilateral bridge. The whole brain analysis found robust, bilateral activation within the motor regions of the brain during the bilateral bridge task, and contralateral activation of the motor regions during unilateral bridging tasks. Furthermore, the ROI-to-ROI analysis demonstrated significant connectivity of a motor network that included the supplemental motor area, bilateral precentral gyrus, and bilateral cerebellum regardless of the motor task performed. These data suggest that while whole brain activation reveals unique patterns of activation across the three tasks, functional connectivity is very similar. As motor control of the lumbopelvic area is of high interest to those studying low back pain (LBP), this study can provide a comparison for future research into potential connectivity changes that occur in individuals with LBP.

Rolandic Cortex Morphology: Magnetic Resonance Imaging-Based Three-Dimensional Cerebral Reconstruction Study and Intraoperative Usefulness

Background  During brain surgery, the neurosurgeon must be able to identify and avoid injury to the Rolandic cortex. However, when only a small part of the cortex is exposed, it may be difficult to identify the Rolandic cortex with certainty. Despite various advanced methods to identify it, visual recognition remains an important backup for neurosurgeons. The aim of the study was to find any specific morphology pattern that may help to identify the Rolandic cortex intraoperatively.

Materials and Methods  Magnetic resonance imaging of the brain from patients with various conditions was used to create the three-dimensional cerebral reconstruction images. A total of 216 patients with 371 intact hemispheres were included. Each image was inspected to note the morphology of the Rolandic cortex and the suprasylvian cortex. Additionally, other two evaluators exclusively inspected the morphology of the suprasylvian cortex. Their observation results were compared to find the agreements.

Results  Several distinctive morphology patterns have been identified at the Rolandic cortex and the suprasylvian cortex including a genu, or a knob at the upper precentral gyrus, an angulation of the lower postcentral gyrus, a strip for pars opercularis, a rectangle for the lower precentral gyrus, and a triangle for the lower postcentral gyrus. Combined total and partial agreement of the suprasylvian cortex morphology pattern ranged from 60.4 to 85.2%.

Conclusion  The authors have demonstrated the distinctive morphology of the Rolandic cortex and the suprasylvian cortex. This information can provide visual guidance to identify the Rolandic cortex particularly during surgery with limited exposure.

A method for mapping retinal images in early visual cortical areas

The visual cortex has been a heavily studied region in neuroscience due to many factors, not the least of which is its well-defined retinotopic organization. This organization makes it possible to predict the general location of cortical regions that stimuli will activate during visual tasks. However, the precise and accurate mapping of these regions in human patients takes time, effort, and participant compliance that can be difficult in many patient populations. In humans, this retino-cortical mapping has typically been done using functional localizers which maximally activate the area of interest, and then the activation profile is thresholded and converted to a binary mask region of interest (ROI). An alternative method involves performing population receptive field (pRF) mapping of the whole visual field and choosing vertices whose pRF centers fall within the stimulus. This method ignores the spatial extent of the pRF which changes dramatically between central and peripheral vision. Both methods require a dedicated functional scan and depend on participants' stable fixation. The aim of this project was to develop a user-friendly method that can transform a retinal object of interest (for example, an image, a retinal lesion, or a preferred locus for fixation) from retinal space to its expected representation on the cortical surface without a functional scan. We modeled the retinal representation of each cortical vertex as a 2D Gaussian with a location and spatial extent given by a previously published retinotopic atlas. To identify how affected any cortical vertex would be by a given retinal object, we took the product of the retinal object with the Gaussian pRF of that cortical vertex. Normalizing this value gives the expected response of a given vertex to the retinal object. This method was validated using BOLD data obtained using a localizer with discrete visual stimuli, and showed good agreement to predicted values. Cortical localization of a visual stimulus or retinal defect can be obtained using our publicly available software, without a functional scan. Our software may benefit research with disease populations who have trouble maintaining stable fixation.

Functional Topography of the Human Subthalamic Nucleus: Relevance for Subthalamotomy in Parkinson's Disease

BACKGROUND

The subthalamic nucleus (STN) is considered a key structure in motor, behavioral, and emotional control. Although identification of the functional topography of the STN has therapeutic implications in the treatment of the motor features of Parkinson's disease (PD), the details of its functional and somatotopic organization in humans are not well understood.

OBJECTIVE

The aim of this study was to characterize the functional organization of the STN and its correlation with the motor outcomes induced by subthalamotomy.

METHODS

We used diffusion-weighted imaging to assess STN connectivity patterns in 23 healthy control subjects and 86 patients with PD, of whom 39 received unilateral subthalamotomy. Analytical tractography was used to reconstruct structural cortico-subthalamic connectivity. A diffusion-weighted imaging/functional magnetic resonance imaging-driven somatotopic parcellation of the STN was defined to delineate the representation of the upper and lower limb in the STN.

RESULTS

We confirmed a connectional gradient to sensorimotor, supplementary-motor, associative, and limbic cortical regions, spanning from posterior-dorsal-lateral to anterior-ventral-medial portions of the STN, with intermediate overlapping zones. Functional magnetic resonance imaging-driven parcellation demonstrated dual segregation of motor cortico-subthalamic projections in humans. Moreover, the relationship between lesion topography and functional anatomy of the STN explains specific improvement in bradykinesia, rigidity, and tremor induced by subthalamotomy.

CONCLUSIONS

Our results support an interplay between segregation and integration of cortico-subthalamic projections, suggesting the coexistence of parallel and convergent information processing. Identifying the functional topography of the STN will facilitate better definition of the optimal location for functional neurosurgical approaches, that is, electrode placement and lesion location, and improve specific cardinal features in PD. © 2021 International Parkinson and Movement Disorder Society.

Human larynx motor cortices coordinate respiration for vocal-motor control

Vocal flexibility is a hallmark of the human species, most particularly the capacity to speak and sing. This ability is supported in part by the evolution of a direct neural pathway linking the motor cortex to the brainstem nucleus that controls the larynx the primary sound source for communication. Early brain imaging studies demonstrated that larynx motor cortex at the dorsal end of the orofacial division of motor cortex (dLMC) integrated laryngeal and respiratory control, thereby coordinating two major muscular systems that are necessary for vocalization. Neurosurgical studies have since demonstrated the existence of a second larynx motor area at the ventral extent of the orofacial motor division (vLMC) of motor cortex. The vLMC has been presumed to be less relevant to speech motor control, but its functional role remains unknown. We employed a novel ultra-high field (7T) magnetic resonance imaging paradigm that combined singing and whistling simple melodies to localise the larynx motor cortices and test their involvement in respiratory motor control. Surprisingly, whistling activated both 'larynx areas' more strongly than singing despite the reduced involvement of the larynx during whistling. We provide further evidence for the existence of two larynx motor areas in the human brain, and the first evidence that laryngeal-respiratory integration is a shared property of both larynx motor areas. We outline explicit predictions about the descending motor pathways that give these cortical areas access to both the laryngeal and respiratory systems and discuss the implications for the evolution of speech.

Differences in cortical structure between cognitively normal East Asian and Caucasian older adults: a surface-based morphometry study

There is a growing literature on the impact of ethnicity on brain structure and function. Despite the regional heterogeneity in age-related changes and non-uniformity across brain morphometry measurements in the aging process, paucity of studies investigated the difference in cortical anatomy between the East Asian and Caucasian older adults. The present study aimed to compare cortical anatomy measurements, including cortical thickness, volume and surface area, between cognitively normal East Asian (n = 171) and Caucasian (n = 178) older adults, using surface-based morphometry and vertex-wise group analysis of high-dimensional structural magnetic resonance imaging (MRI) data. The East Asian group showed greater cortical thickness and larger cortical volume in the right superior temporal gyrus, postcentral gyrus, bilateral inferior temporal gyrus, and inferior parietal cortex. The Caucasian group showed thicker and larger cortex in the left transverse temporal cortex, lingual gyrus, right lateral occipital cortex, and precentral gyrus. Additionally, the difference in surface area was discordant with that in cortical thickness. Differences in brain structure between the East Asian and Caucasian might reflect differences in language and information processing, but further studies using standardized methods for assessing racial characteristics are needed. The research results represent a further step towards developing a comprehensive understanding of differences in brain structure between ethnicities of older adults, and this would enrich clinical research on aging and neurodegenerative diseases.

Incentives and voluntary stopping: The intentional hand task

Intentional inhibition, the endogenous decision to stop or cancel an action, is arguably a more ecologically valid process than automatized, reactive, inhibition which occurs in response to an external stop signal without active decision making at the moment of inhibition. Choosing to stop an act of opening the fridge door, or of reaching for a bottle of alcohol may therefore extend beyond a reactive inhibitory process, e.g. stopping at a red traffic light. Existing paradigms of intentional inhibition focus on the proportions of intentional stops. Here we developed the Intentional Hand Task, which provides stop response times for intentional and instructed trials. Participants move a cursor by initiating an arm movement, after which a Go, Stop or Choice trial occurs. In Go trials, participants are instructed to make a speeded continuation of their arm movement towards a target whereas in the Stop trials participants are instructed to rapidly stop the already initiated movement. In Choice trials, participants chose whether to continue or stop the movement. By comparing response times when movement was stopped, we found that intentionally stopping took significantly longer than externally instructed stopping. We further investigated the influence of reward incentives, by cueing trials with either the prospect of No, Low or High reward for correctly continuing in Go trials, stopping in Stop trials or achieving a random balance of intentional Go and Stops in Choice trials. Reward incentives led to greater approach behaviours, indicated by significantly higher Go accuracy in instructed Go trials and faster response times across both Go trial types. The presence of reward incentives led to significantly fewer intentional stop choices. Our findings suggest intentional inhibition of an ongoing action may require a further decisional process. Furthermore, monetary incentives may implicitly trigger an appetitive system thus facilitating approach rather than intentional inhibitory behaviour. These findings are particularly relevant to cue-related relapse in disorders of addiction where cues may facilitate approach behaviours to the detriment of intentional inhibitory control.

Hand, foot and lip representations in primary sensorimotor cortex: a high-density electroencephalography study

The primary sensorimotor cortex plays a major role in the execution of movements of the contralateral side of the body. The topographic representation of different body parts within this brain region is commonly investigated through functional magnetic resonance imaging (fMRI). However, fMRI does not provide direct information about neuronal activity. In this study, we used high-density electroencephalography (hdEEG) to map the representations of hand, foot, and lip movements in the primary sensorimotor cortex, and to study their neural signatures. Specifically, we assessed the event-related desynchronization (ERD) in the cortical space. We found that the performance of hand, foot, and lip movements elicited an ERD in beta and gamma frequency bands. The primary regions showing significant beta- and gamma-band ERD for hand and foot movements, respectively, were consistent with previously reported using fMRI. We observed relatively weaker ERD for lip movements, which may be explained by the fact that less fine movement control was required. Overall, our study demonstrated that ERD based on hdEEG data can support the study of motor-related neural processes, with relatively high spatial resolution. An interesting avenue may be the use of hdEEG for deeper investigations into the pathophysiology of neuromotor disorders.

Precise finger somatotopy revealed by focal motor cortex injury

BACKGROUND

Somatotopy is considered the hallmark of the primary motor cortex. While this is fundamentally true for the major body parts (head, upper and lower extremities), evidence supporting the existence of within-limb somatotopy is scarce.

METHOD

We report a young man presenting recurrent ischemic strokes with selective finger weakness in whom serial motor cortex mapping procedures were performed.

RESULT

Following the first stroke, which largely spared the motor cortex, motor mapping displayed overlap of the motor representations of the hand muscles. The second focal stroke, affecting the lateral part of the hand knob, resulted in selective loss of the first dorsal interosseous muscle motor evoked potentials while sparing those of the adductor digiti minimi muscle. This observation is in apparent contradiction with the first mapping results that suggested complete overlap of motor representations.

DISCUSSION

Our mapping results provide evidence for the existence of very precise within-limb somatotopy and confirm the proposed homuncular order, whereby lateral fingers are represented laterally and medial fingers medially. The discrepancy between the initial and subsequent mapping results is discussed in light of functional organization of the primary motor cortex.

How does human motor cortex regulate vocal pitch in singers?

Vocal pitch is used as an important communicative device by humans, as found in the melodic dimension of both speech and song. Vocal pitch is determined by the degree of tension in the vocal folds of the larynx, which itself is influenced by complex and nonlinear interactions among the laryngeal muscles. The relationship between these muscles and vocal pitch has been described by a mathematical model in the form of a set of 'control rules'. We searched for the biological implementation of these control rules in the larynx motor cortex of the human brain. We scanned choral singers with functional magnetic resonance imaging as they produced discrete pitches at four different levels across their vocal range. While the locations of the larynx motor activations varied across singers, the activation peaks for the four pitch levels were highly consistent within each individual singer. This result was corroborated using multi-voxel pattern analysis, which demonstrated an absence of patterned activations differentiating any pairing of pitch levels. The complex and nonlinear relationships between the multiple laryngeal muscles that control vocal pitch may obscure the neural encoding of vocal pitch in the brain.

Development of a New Robotic Ankle Rehabilitation Platform for Hemiplegic Patients after Stroke

A large amount of hemiplegic survivors are suffering from motor impairment. Ankle rehabilitation exercises act an important role in recovering patients' walking ability after stroke. Currently, patients mainly perform ankle exercise to reobtain range of motion (ROM) and strength of the ankle joint under a therapist's assistance by manual operation. However, therapists suffer from high work intensity, and most of the existed rehabilitation devices focus on ankle functional training and ignore the importance of neurological rehabilitation in the early hemiplegic stage. In this paper, a new robotic ankle rehabilitation platform (RARP) is proposed to assist patients in executing ankle exercise. The robotic platform consists of two three-DOF symmetric layer-stacking mechanisms, which can execute ankle internal/external rotation, dorsiflexion/plantarflexion, and inversion/eversion exercise while the rotation center of the distal zone of the robotic platform always coincides with patients' ankle pivot center. Three exercise modes including constant-speed exercise, constant torque-impedance exercise, and awareness exercise are developed to execute ankle training corresponding to different rehabilitation stages. Experiments corresponding to these three ankle exercise modes are performed, the result demonstrated that the RARP is capable of executing ankle rehabilitation, and the novel awareness exercise mode motivates patients to proactively participate in ankle training.

Autobiography of James S. Hyde

The papers, book chapters, reviews, and patents by James S. Hyde in the bibliography of this document have been separated into EPR and MRI sections, and within each section by topics. Within each topic, publications are listed chronologically. A brief summary is provided for each patent listed. A few publications and patents that do not fit this schema have been omitted. This list of publications is preceded by a scientific autobiography that focuses on selected topics that are judged to have been of most scientific importance. References to many of the publications and patents in the bibliography are made in the autobiography.

Novel imaging techniques to study the functional organization of the human brain

Despite more than a century of investigation into the cortical organization of motor function, the existence of motor somatotopy is still debated. We review functional magnetic resonance imaging (fMRI) studies examining motor somatotopy in the cerebral cortex. In spite of a substantial overlap of representations corresponding to different body parts, especially in non-primary motor cortices, geographic approaches are capable of revealing somatotopic ordering. From the iconic homunculus in the contralateral primary cortex to the subtleties of ipsilateral somatotopy and its relations with lateralization, we outline potential reasons for the lack of segregation between motor representations. Among these are the difficulties in distinguishing activity that arises from multiple muscular effectors, the need for flexible motor control and coordination of complex movements through functional integration and artefacts in fMRI. Methodological advances with regard to the optimization of experimental design and fMRI acquisition protocols as well as improvements in spatial registration of images and indices aiming at the quantification of the degree of segregation between different functional representations are inspected. Additionally, we give some hints as to how the functional organization of motor function might be related to various anatomical landmarks in brain morphometry.

Functional parcellation using time courses of instantaneous connectivity

Functional neuroimaging studies have led to understanding the brain as a collection of spatially segregated functional networks. It is thought that each of these networks is in turn composed of a set of distinct sub-regions that together support each network's function. Considering the sub-regions to be an essential part of the brain's functional architecture, several strategies have been put forward that aim at identifying the functional sub-units of the brain by means of functional parcellations. Current parcellation strategies typically employ a bottom-up strategy, creating a parcellation by clustering smaller units. We propose a novel top-down parcellation strategy, using time courses of instantaneous connectivity to subdivide an initial region of interest into sub-regions. We use split-half reproducibility to choose the optimal number of sub-regions. We apply our Instantaneous Connectivity Parcellation (ICP) strategy on high-quality resting-state FMRI data, and demonstrate the ability to generate parcellations for thalamus, entorhinal cortex, motor cortex, and subcortex including brainstem and striatum. We evaluate the subdivisions against available cytoarchitecture maps to show that our parcellation strategy recovers biologically valid subdivisions that adhere to known cytoarchitectural features.

The ovine motor cortex: A review of functional mapping and cytoarchitecture

In recent years, sheep (Ovis aries) have emerged as a useful animal model for neurological research due to their relatively large brain and blood vessel size, their cortical architecture, and their docile temperament. However, the functional anatomy of sheep brain is not as well studied as that of non-human primates, rodents, and felines. For example, while the location of the sheep motor cortex has been known for many years, there have been few studies of the somatotopy of the motor cortex and there were a range of discrepancies across them. The motivation for this review is to provide a definitive resource for studies of the sheep motor cortex. This work critically reviews the literature examining the organization of the motor cortex in sheep, utilizing studies that have applied direct electrical stimulation and histological methods A clearer understanding of the sheep brain will facilitate and progress the use of this species as a scientific animal model for neurological research.

Preparation and execution of teeth clenching and foot muscle contraction influence on corticospinal hand-muscle excitability

Contraction of a muscle modulates not only the corticospinal excitability (CSE) of the contracting muscle but also that of different muscles. We investigated to what extent the CSE of a hand muscle is modulated during preparation and execution of teeth clenching and ipsilateral foot dorsiflexion either separately or in combination. Hand-muscle CSE was estimated based on motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) and recorded from the first dorsal interosseous (FDI) muscle. We found higher excitability during both preparation and execution of all the motor tasks than during mere observation of a fixation cross. As expected, the excitability was greater during the execution phase than the preparation one. Furthermore, both execution and preparation of combined motor tasks led to higher excitability than individual tasks. These results extend our current understanding of the neural interactions underlying simultaneous contraction of muscles in different body parts.

Winning is not enough: ventral striatum connectivity during physical aggression

Social neuroscience studies have shown that the ventral striatum (VS), a highly reward-sensitive brain area, is activated when participants win competitive tasks. However, in these settings winning often entails both avoiding punishment and punishing the opponent. It is thus unclear whether the rewarding properties of winning are mainly associated to punishment avoidance, or if punishing the opponent can be additionally gratifying. In the present paper we explored the neurophysiological correlates of each outcome, aiming to better understand the development of aggression episodes. We previously introduced a competitive reaction time task that separates both effects: in half of the won trials, participants can physically punish their opponent (active trials), whereas in the other half they can only avoid a punishment (passive trials). We performed functional connectivity analysis seeded in the VS to test for differential network interactions in active compared to passive trials. The VS showed greater connectivity with areas involved in reward valuation (orbitofrontal cortex), arousal (dorsal thalamus and posterior insula), attention (inferior occipital gyrus), and motor control (supplementary motor area) in active compared to passive trials, whereas connectivity between the VS and the inferior frontal gyrus decreased. Interindividual variability in connectivity strength between VS and posterior insula was related to aggressive behavior, whereas connectivity between VS and supplementary motor area was related to faster reaction times in active trials. Our results suggest that punishing a provoking opponent when winning might adaptively favor a "competitive state" in the course of an aggressive interaction.

Risonanza magnetica funzionale dell'encefalo in pazienti candidati ad intervento chirurgico con guida stereotassica

Negli ultimi anni la risonanza magnetica funzionale dell'encefalo (fMRI) si è proposta con successo nello studio dell'attività encefalica durante lo svolgimento di determinate funzioni. Si è inoltre delineato per essa un ruolo paricolarmente interessante nell'ambito della pianificazione preoperatoria di pazienti destinati ad un intervento chirurgico in sedi encefaliche critiche, ovvero ad alto rischio di invalidtà postoperatoria.

Il presente lavoro mira alla realizzazione di mappe di attivazione motoria in pazienti con lesioni occupanti spazio nell'encefalo mediante un tomografo a 1,5 T di non recentissima tecnologia; successivamente si è voluto valutare l'informatività di tali mappe, sia dal punto di vista neurochirurgico sia dal punto di vista neurofisiologico.

Sono stati presi in esame 5 pazienti, tutti portatori di una lesione occupante spazio in prossimità della corteccia perirolandica e tutti destinati ad un intervento chirurgico in stereotassi per l'asportazione di tale lesione. I pazienti venivano sottoposti in un'unica seduta allo studio funzionale e morfologico dell'encefalo con il casco stereotassico in sede.

Lo studio di fMRI si è svolto su uno o massimo due piani assiali orientati ortogonalmente al decorso della scissura di Rolando. Esso prevedeva come prova di attivazione il movimento della mano controlaterale all'emisfero con la lesione da asportare.

In un paziente la funzione motoria è stata studiata anche intraoperatoriamente mediante la stimolazione elettrica della corteccia cerebrale.

In 4 pazienti si è avuta una netta rappresentazione della corteccia sensitivo-motoria di tale emisfero. In 3 di essi si è vista inoltre un'attivazione dell'emisfero opposto, ipsilaterale alla mano in movimento. Altre zone di attivazione visualizzate nei nostri studi sono state messe in relazione con l'area motoria supplementare (3 pazienti) e l'area premotoria (2 pazienti).

Nel paziente in cui si è proceduto intraoperatoriamente con la stimolazione elettrica della corteccia cerebrale è stata riscontrata una buona concordanza tra lo studio elettrofisiologico e l'indagine di fMRI.

Analizzando i risultati da noi conseguiti possiamo concludere che anche un tomografo a 1,5 T di tipo convenzionale si presta ad un'indagine di fMRI in pazienti con lesioni encefaliche. Le mappe di attivazione realizzate su uno o due piani assiali sono in grado di fornire delle informazioni sui rapporti tra la lesione da asportare e la corteccia sensitivo-motoria, in particolare l'area della mano. Ciò ha notevoli implicazioni dal punto di vista neurochirurgico, considerando quanto sia importante la salvaguardia dell'integrità funzionale del soggetto che si sottopone ad un intervento neurochirurgico in una sede critica come la corteccia perirolandica.

Clinical Significance of Invasive Motor Cortex Stimulation for Trigeminal Facial Neuropathic Pain Syndromes

BACKGROUND:

Invasive neuromodulation of the cortical surface for various chronic pain syndromes has been performed for &gt;20 years. The significance of motor cortex stimulation (MCS) in chronic trigeminal neuropathic pain (TNP) syndromes remains unclear. Different techniques are performed worldwide in regard to operative procedure, stimulation parameters, test trials, and implanted materials.

OBJECTIVE:

To present the clinical experiences of a single center with MCS, surgical approach, complications, and follow-up as a prospective, noncontrolled clinical trial.

METHODS:

The implantation of epidural leads over the motor cortex was performed via a burr hole technique with neuronavigation and intraoperative neurostimulation. Special focus was placed on a standardized test trial with an external stimulation device and the implementation of a double-blinded or placebo test phase to identify false-positive responders.

RESULTS:

A total of 36 patients with TNP were operated on, and MCS was performed. In 26 of the 36 patients (72%), a significant pain reduction from a mean of 8.11 to 4.58 (on the visual analog scale) during the test trial was achieved (P &lt;.05). Six patients were identified as false-positive responders (17%). At the last available follow-up of 26 patients (mean, 5.6 years), active MCS led to a significant pain reduction compared with the preoperative pain ratings (mean visual analog scale score, 5.01; P &lt;.05).

CONCLUSION:

MCS is an additional therapeutic option for patients with refractory chronic TNP, and significant long-term pain suppression can be achieved. Placebo or double-blinded testing is mandatory.

Dynamic Motor Cortical Organization

Motor cortical organization has commonly been conceived as somatotopically ordered, with single body parts controlled from individual patches of cortical tissue. An opposing viewpoint suggests that motor cortex has a distnbuted, adaptive, and dynamic organi zation that underlies movement planning, performance, adaptation, and learning. Con verging evidence from anatomic, neurophysiologic, and functional neuroimaging sources indicates that the arm area of motor cortical areas in monkeys and humans has multiple, interconnected sites that ostensibly contribute to controlling various parts of the arm. These representations can exhibit rapid and sometimes enduring modifications following injury, changes in somatic sensory input, and motor learning. Activity-dependent changes in the intrinsic motor cortical network of horizontal and vertical connections coupled with ascending thalamic and corticocortical inputs could provide a substrate for dynamic mod ulation of motor cortex functional representations. NEUROSCIENTIST 3:158-165, 1997

Abnormal surface morphology of the central sulcus in children with attention-deficit/hyperactivity disorder

The central sulcus (CS) divides the primary motor and somatosensory areas, and its three-dimensional (3D) anatomy reveals the structural changes of the sensorimotor regions. Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that is associated with sensorimotor and executive function deficits. However, it is largely unknown whether the morphology of the CS alters due to inappropriate development in the ADHD brain. Here, we employed the sulcus-based morphometry approach to investigate the 3D morphology of the CS in 42 children whose ages spanned from 8.8 to 13.5 years (21 with ADHD and 21 controls). After automatic labeling of each CS, we computed seven regional shape metrics for each CS, including the global average length, average depth, maximum depth, average span, surface area, average cortical thickness, and local sulcal profile. We found that the average depth and maximum depth of the left CS as well as the average cortical thickness of bilateral CS in the ADHD group were significantly larger than those in the healthy children. Moreover, significant between-group differences in the sulcal profile had been found in middle sections of the CSs bilaterally, and these changes were positively correlated with the hyperactivity-impulsivity scores in the children with ADHD. Altogether, our results provide evidence for the abnormity of the CS anatomical morphology in children with ADHD due to the structural changes in the motor cortex, which significantly contribute to the clinical symptomatology of the disorder.

Impact of World War I on brain mapping

Although much tragedy was experienced during World War I (WWI), the nature of the war and the advancements of weaponry led to a change in the quality and quantity of injuries which were conducive for study. This paper discusses how trauma during WWI led to advances in brain mapping from occipital injuries. Gordon Holmes was a British neurologist who was able to create a retinotopic map of the visual cortex from studying more than 400 cases of occipital injuries; his work has contributed immensely to our understanding of visual processing. There have been many extensions from Holmes' work in regard to how we analyze other sensory modalities and in researching how the brain processes complex stimuli such as faces. Aside from the scholastic benefit, brain mapping also has functional use and can be used for neurosurgical planning to preserve important structures. With the advent of more advanced modalities for analyzing the brain, there have been initiatives in total brain mapping which has added significantly to the body of work started by Holmes during WWI. This paper reviews the history during WWI that led to advances in brain mapping, the lasting scholastic and functional impact from these advancements, and future improvements.

Monitoring Neuro-Motor Recovery From Stroke With High-Resolution EEG, Robotics and Virtual Reality: A Proof of Concept

A novel system for the neuro-motor rehabilitation of upper limbs was validated in three sub-acute post-stroke patients. The system permits synchronized cortical and kinematic measures by integrating high-resolution EEG, passive robotic device and Virtual Reality. The brain functional re-organization was monitored in association with motor patterns replicating activities of daily living (ADL). Patients underwent 13 rehabilitation sessions. At sessions 1, 7 and 13, clinical tests were administered to assess the level of motor impairment, and EEG was recorded during rehabilitation task execution. For each session and rehabilitation task, four kinematic indices of motor performance were calculated and compared with the outcome of clinical tests. Functional source maps were obtained from EEG data and projected on the real patients' anatomy (MRI data). Laterality indices were calculated for hemispheric dominance assessment. All patients showed increased participation in the rehabilitation process. Cortical activation changes during recovery were detected in relation to different motor patterns, hence verifying the system's suitability to add quantitative measures of motor performance and neural recovery to classical tests. We conclude that this system seems a promising tool for novel robot-based rehabilitation paradigms tailored to individual needs and neuro-motor responses of the patients.

Microsurgical anatomy of the central lobe

OBJECT

Central Lobe consists of the pre- and postcentral gyri on the lateral surface and the Paracentral Lobule on the medial surface and corresponds to the sensorimotor cortex. The objective of the present study was to define the neural features, craniometric relationships, arterial supply, and venous drainage of the central lobe.

METHODS

Cadaveric hemispheres dissected using microsurgical techniques provided the material for this study.

RESULTS

The coronal suture is closer to the precentral gyrus and central sulcus at its lower rather than at its upper end, but they are closest at a point near where the superior temporal line crosses the coronal suture. The arterial supply of the lower two-thirds of the lateral surface of the central lobe was from the central, precentral, and anterior parietal branches that arose predominantly from the superior trunk of the middle cerebral artery. The medial surface and the superior third of the lateral surface were supplied by the posterior interior frontal, paracentral, and superior parietal branches of the pericallosal and callosomarginal arteries. The venous drainage of the superior two-thirds of the lateral surface and the central lobe on the medial surface was predominantly through the superior sagittal sinus, and the inferior third of the lateral surface was predominantly through the superficial sylvian veins to the sphenoparietal sinus or the vein of Labbé to the transverse sinus.

CONCLUSIONS

The pre- and postcentral gyri and paracentral lobule have a morphological and functional anatomy that differentiates them from the remainder of their respective lobes and are considered by many as a single lobe. An understanding of the anatomical relationships of the central lobe can be useful in preoperative planning and in establishing reliable intraoperative landmarks.

Generation and Evaluation of a Cortical Area Parcellation from Resting-State Correlations

The cortical surface is organized into a large number of cortical areas; however, these areas have not been comprehensively mapped in the human. Abrupt transitions in resting-state functional connectivity (RSFC) patterns can noninvasively identify locations of putative borders between cortical areas (RSFC-boundary mapping; Cohen et al. 2008). Here we describe a technique for using RSFC-boundary maps to define parcels that represent putative cortical areas. These parcels had highly homogenous RSFC patterns, indicating that they contained one unique RSFC signal; furthermore, the parcels were much more homogenous than a null model matched for parcel size when tested in two separate datasets. Several alternative parcellation schemes were tested this way, and no other parcellation was as homogenous as or had as large a difference compared with its null model. The boundary map-derived parcellation contained parcels that overlapped with architectonic mapping of areas 17, 2, 3, and 4. These parcels had a network structure similar to the known network structure of the brain, and their connectivity patterns were reliable across individual subjects. These observations suggest that RSFC-boundary map-derived parcels provide information about the location and extent of human cortical areas. A parcellation generated using this method is available at http://www.nil.wustl.edu/labs/petersen/Resources.html.

Neural activation in humans during a simple motor task differs between BDNF polymorphisms

The BDNF Val66Met polymorphism has been linked to decreased synaptic plasticity involved in motor learning tasks. We investigated whether individual differences in this polymorphism may promote differences in neural activity during a two-alternative forced-choice motor performance. In two separate sessions, the BOLD signal from 22 right-handed healthy men was measured during button presses with the left and right index finger upon visual presentation of an arrow. 11 men were Val66Val carriers (ValVal group), the other 11 men carried either the Val66Met or the Met66Met polymorphism (Non-ValVal group). Reaction times, resting and active motor thresholds did not differ between ValVal and Non-ValVal groups. Compared to the ValVal group the Non-ValVal group showed significantly higher BOLD signals in the right SMA and motor cingulate cortex during motor performance. This difference was highly consistent for both hands and across all four sessions. Our finding suggests that this BDNF polymorphism may not only influence complex performance during motor learning but is already associated with activation differences during rather simple motor tasks. The higher BOLD signal observed in Non-ValVal subjects suggests the presence of cumulative effects of the polymorphism on the motor system, and may reflect compensatory functional activation mediating equal behavioral performance between groups.

Causal interaction following the alteration of target region activation during motor imagery training using real-time fMRI

Motor imagery training is an effective approach for motor skill learning and motor function rehabilitation. As a novel method of motor imagery training, real-time fMRI (rtfMRI) enables individuals to acquire self-control of localized brain activation, achieving desired changes in behavior. The regulation of target region activation by rtfMRI often alters the activation of related brain regions. However, the interaction between the target region and these related regions is unclear. The Granger causality model (GCM) is a data-driven method that can explore the causal interaction between brain regions. In this study, we employed rtfMRI to train subjects to regulate the activation of the ipsilateral dorsal premotor area (dPMA) during motor imagery training, and we calculated the causal interaction of the dPMA with other motor-related regions based on the GCM. The results demonstrated that as the activity of the dPMA changed during rtfMRI training, the interaction of the target region with other related regions became significantly altered, and behavioral performance was improved after training. The altered interaction primarily exhibited as an increased unidirectional interaction from the dPMA to the other regions. These findings support the dominant role of the dPMA in motor skill learning via rtfMRI training and may indicate how activation of the target region interacts with the activation of other related regions.

Functional somatotopy revealed across multiple cortical regions using a model of complex motor task

The primary motor cortex (M1) possesses a functional somatotopic structure-representations of adjacent within-limb joints overlap to facilitate coordination while maintaining discrete centers for individuated movement. We examined whether similar organization exists across other sensorimotor cortices. Twenty-four right-handed healthy subjects underwent functional magnetic resonance imaging (fMRI) while tracking complex targets with flexion/extension at right finger, elbow and ankle separately. Activation related to each joint at false discovery rate of 0.005 served as its representation across multiple regions. Within each region, we identified the center of mass (COM) for each representation, and the overlap between the representations of within-limb (finger and elbow) and between-limb joints (finger and ankle). Somatosensory (S1) and premotor cortices (PMC) demonstrated greater distinction of COM and minimal overlap for within- and between-limb representations. In contrast, M1 and supplementary motor area (SMA) showed more integrative somatotopy with higher sharing for within-limb representations. Superior and inferior parietal lobule (SPL and IPL) possessed both types of structure. Some clusters exhibited extensive overlap of within- and between-limb representations, while others showed discrete COMs for within-limb representations. Our results help to infer hierarchy in motor control. Areas such as S1 may be associated with individuated movements, while M1 may be more integrative for coordinated motion; parietal associative regions may allow switch between both modes of control. Such hierarchy creates redundant opportunities to exploit in stroke rehabilitation. The use of complex rather than traditionally used simple movements was integral to illustrating comprehensive somatotopic structure; complex tasks can potentially help to understand cortical representation of skill and learning-related plasticity.

The retinotopic organization of striate cortex is well predicted by surface topology

In 1918, Gordon Holmes combined observations of visual-field scotomas across brain-lesioned soldiers to produce a schematic map of the projection of the visual field upon the striate cortex. One limit to the precision of his result, and the mapping of anatomy to retinotopy generally, is the substantial individual variation in the size, volumetric position, and cortical magnification of area V1. When viewed within the context of the curvature of the cortical surface, however, the boundaries of striate cortex fall at a consistent location across individuals. We asked whether the surface topology of the human brain can be used to accurately predict the internal, retinotopic function of striate cortex as well. We used fMRI to measure polar angle and eccentricity in 25 participants and combined their maps within a left-right, transform-symmetric representation of the cortical surface. These data were then fit using a deterministic, algebraic model of visual-field representation. We found that an anatomical image alone can be used to predict the retinotopic organization of striate cortex for an individual with accuracy equivalent to 10-25 min of functional mapping. This indicates tight developmental linkage of structure and function within a primary, sensory cortical area.

Functional MRI assessment of orofacial articulators: neural correlates of lip, jaw, larynx, and tongue movements

Compared with complex coordinated orofacial actions, few neuroimaging studies have attempted to determine the shared and distinct neural substrates of supralaryngeal and laryngeal articulatory movements when performed independently. To determine cortical and subcortical regions associated with supralaryngeal motor control, participants produced lip, tongue and jaw movements while undergoing functional magnetic resonance imaging (fMRI). For laryngeal motor activity, participants produced the steady-state/i/vowel. A sparse temporal sampling acquisition method was used to minimize movement-related artifacts. Three main findings were observed. First, the four tasks activated a set of largely overlapping, common brain areas: the sensorimotor and premotor cortices, the right inferior frontal gyrus, the supplementary motor area, the left parietal operculum and the adjacent inferior parietal lobule, the basal ganglia and the cerebellum. Second, differences between tasks were restricted to the bilateral auditory cortices and to the left ventrolateral sensorimotor cortex, with greater signal intensity for vowel vocalization. Finally, a dorso-ventral somatotopic organization of lip, jaw, vocalic/laryngeal, and tongue movements was observed within the primary motor and somatosensory cortices using individual region-of-interest (ROI) analyses. These results provide evidence for a core neural network involved in laryngeal and supralaryngeal motor control and further refine the sensorimotor somatotopic organization of orofacial articulators.

Deformable anatomic templates embed knowledge into brain images: part 2. Validation using functional magnetic resonance imaging of the motor hand

OBJECTIVE

This study evaluated the concordance between the Deformable Anatomic Template (DAT)-identified origin of motor hand fibers and localization of the motor cortex of the hand by functional magnetic resonance imaging (fMRI).

METHODS

Preoperative fMRI during hand motor tasks was performed on 36 hemispheres in 26 patients with gliomas in or near eloquent areas. Reformatted volume-rendered surface images were labeled with the DAT's hand motor fibers and fMRI data. Five reviewers assessed the data for concordance.

RESULTS

Available fMRI data were diagnostically usable in 92% (33/36 analyzed hemispheres), with DAT anatomic accuracy in the remaining cases. The DAT prediction and fMRI findings were concordant in all 9 normal hemispheres and in 20 (83%) of 24 glioma-bearing hemispheres. The 4 discordant cases resulted from substantial mass effect by large frontal tumors.

CONCLUSIONS

This study validated DAT's anatomic atlas and alignment process for the expected position of the motor cortex of the hand.