Ventral Premotor Cortex Research Articles

Sensitivity to perception level differentiates two subnetworks within the mirror neuron system.

Mirror neurons are a subset of brain cells that discharge during action execution and passive observation of similar actions. An open question concerns the functional role of their ability to match observed and executed actions. Since understanding of goals requires conscious perception of actions, we expect that mirror neurons potentially involved in action goal coding, will be modulated by changes in action perception level. Here, we manipulated perception level of action videos depicting short hand movements and measured the corresponding fMRI BOLD responses in mirror regions. Our results show that activity levels within a network of regions, including the sensorimotor cortex, primary motor cortex, dorsal premotor cortex and posterior superior temporal sulcus, are sensitive to changes in action perception level, whereas activity levels in the inferior frontal gyrus, ventral premotor cortex, supplementary motor area and superior parietal lobule are invariant to such changes. In addition, this parcellation to two sub-networks manifest as smaller functional distances within each group of regions during task and resting state. Our results point to functional differences between regions within the mirror neurons system which may have implications with respect to their possible role in action understanding.

T017 Hebbian plasticity in the parieto-frontal network

Transcranial magnetic stimulation (TMS) provides a unique opportunity to test the causal neurophysiological interactions between interconnnected brain areas. This can be done by applying two coils over two different brain areas and deliver subsequent TMS pulses with a certain time interval in the range of few milliseconds (dual-site TMS). In these paradigms, a conditioning stimulus (CS) is first used to activate putative pathways to the motor cortex (M1) from the site of stimulation, while a second, test stimulus (TS), delivered a few ms later probes any changes in excitability that are produced by the input. Dual-site TMS can be used to investigate mechanisms of spike timing dependent plasticity within a certain network. LTP- and LTD-like effects can be induced in M1 following the repeated application of paired pulses over interconnected areas such as contralateral M1, ventral premotor cortex, supplementary motor area or the posterior parietal cortex (PPC). A crucial question is whether dual site TMS effects are limited to M1 or can be used to measure the activity of the other targeted non motor areas. The combination of dual site TMS with electroencephalography (EEG) is a promosing way to overcome these issues (Veniero et al., 2013; Picazio et al., 2014). TMS/EEG allows to measure physiological signals generated at the cortical level by TMS, including those generated in the so-called silent-areas such as PPC and to assess modifications of cortical connectivity.

Dissecting direct and indirect pathways between ventral premotor cortex and the spinal cord by transcranial magnetic stimulation

Dissecting direct and indirect pathways between ventral premotor cortex and the spinal cord by transcranial magnetic stimulation

P130 Assessing the roles of inferior parietal lobule and ventral premotor cortex in emotion body processing: a combined cTBS-fMRI study

Introduction The perception of emotion stimuli in the environment prepares our bodies for action, and especially when confronted with whole body expressions of an emotion like anger, action-related areas in the brain are triggered. Previously, parietal dorsal stream and premotor areas have been linked as crucial areas for processing of such stimuli, but questions about their contributions and specificity within the body processing network remain. Objectives We set out to disentangle the respective roles of dorsal stream areas crucial for action observation (inferior parietal lobule (IPL)) and premotor areas involved in action preparation (ventral premotor cortex (PMv)) in the processing of emotional bodies by assessing local as well as remote effects of cTBS stimulation within the body processing network. Methods Seventeen participants completed the experiment, which consisted of three fMRI sessions. Functional images were acquired using a 3T scanner with a 64-channel head-neck coil. During each session a passive viewing task was performed in which blocks of short videoclips of actors performing a neutral or angry action were presented. Two of the sessions were preceded by neuronavigated cTBS stimulation over either rIPL or rPMv based on individual anatomy. One session was used to assess baseline activity. During the baseline session two functional localizers were acquired to determine regions of interest (ROI). Functional ROIs include bilateral extrastriate body area (EBA), right temporoparietal junction (rTPJ), and right posterior superior temporal sulcus (rpSTS). Results Preliminary results of five participants hint at a general decreased response to both angry and neutral bodies in three of the functionally defined regions of interest (lEBA, rTPJ and rpSTS). Further analysis will focus on anatomically defined ROIs representing the areas stimulated (rIPL and rPMv), as well as whole brain group analysis comparing the three sessions. Conclusions Initial results confirm the involvement of rIPL and rPMv in the processing of dynamic body stimuli. Stimulation of these areas has previously shown effects on the behavioural level, the results of the current experiment will extend these results by showing how also remote areas involved in body processing are affected by stimulation.

P052 Investigation of the influence of the parieto-premotor network on the motor cortex in writer’s cramp using transcranial magnetic stimulation (TMS)

Objective We aimed to study the influence of the parieto-premotor network on the motor cortex in patients with writer’s cramp. Background The parietal and premotor cortices have been shown to be involved in right-handed writing. It has also been shown that the connectivity between these regions may be reduced in writer’s cramp, a type of task-specific focal hand dystonia. Methods We used a three single-pulse TMS paradigm (preconditioning, conditioning and test pulse) to sequentially stimulate the left posterior parietal cortex (PPC), left ventral premotor cortex (PMv) and the left motor cortex (M1). A paired-pulse TMS paradigm was used to probe the functional connectivity of the PMv and M1, as well as the PPC and M1 prior to the three single-pulse TMS paradigm. Results 8 right-handed healthy volunteers (mean age 55 years, standard error 4 years) and 8 right-handed patients with writer’s cramp (mean age 62 years, standard error 2 years) completed the study. We confirmed the presence of premotor-to-motor inhibition in the healthy volunteer group at interstimulus intervals (ISI) s of 4 ms and 8 ms, while this was not seen in the patient group. Facilitatory influences from the posterior parietal cortex was seen in both groups (ISIs of 4 ms and 6 ms in the healthy group, and 6 ms in the patient group). Download : Download high-res image (202KB) Download : Download full-size image The premotor-to-motor inhibition was found to reverse in healthy volunteers (shown in Fig. 2, as no statistical significance was seen amongst the test and triple conditions), while no effects were seen in patients. Conclusions We confirmed that in healthy volunteers, the PPC appears to have an influence on the PMv, resulting in reversal of the inhibition seen with PMv paired-pulse stimuli. This along with premotor-to-motor inhibition, was not seen in patients with writer’s cramp. Facilitatory parietal influences on M1, on the other hand, appear to be intact in these patients. These results suggest that the connectivity between PPC and M1 is intact in patients with writer’s cramp, while the connectivity between PPC and PMv, and PMv and M1 appears altered. Download : Download high-res image (77KB) Download : Download full-size image

P139 Assessment of cortico-cortical connectivity between premotor and motor cortices by means of combined peripheral nerve electrical stimulation and transcranial magnetic stimulation

Introduction Cortico-cortical connectivity can be assessed by Transcranial Magnetic Stimulation (TMS) paradigms. The “conditioning” coil delivers a pulse over the cortex of interest, followed a few milliseconds later by a pulse delivered on the motor cortex (M1) through the “test” coil. Functional connectivity between the two regions is demonstrated by a change in motor evoked potentials (MEPs) produced by the test coil alone compared to those preceded by conditioning TMS. However, the need to place two TMS coils on the same hemisphere produces practical limitations when testing connectivity between sites located in close spatial proximity to M1 and M1 itself. Objectives Here we devised a new paradigm to test M1 excitability after a TMS conditioning pulse delivered to a different cortical region (in this case the ventral premotor cortex – PMv). We exploited a well-known trans-cortical long latency reflex (LLR) in the upper limb. Therefore, instead of testing MEP amplitudes, we assessed the modulation in amplitude of the LLR by the conditioning TMS pulse. Materials & Methods The LLR was obtained by electrical stimulation of the median nerve at the wrist and recording from the ipsilateral thenar muscles. In some trials the median nerve was stimulated alone, in others it was coupled with a single conditioning TMS pulse delivered to the PMv contralateral to the stimulated hand. The timing of TMS was set from +9 to +42 ms at 3 ms steps after electrical stimulation of the median nerve at the wrist. Results We found a significant effect of conditioning TMS over PMv on the LLR amplitude, only when TMS was delivered around 15 ms from the electrical stimulation. Conclusion We propose that the observed interaction between TMS and peripheral nerve stimulation occurs at the cortical level. In particular, the hypothesis that we favour is that the corticofugal volley evoked by TMS on PMv interacts with the afferent volley from the median nerve at the level of M1. This protocol could provide information on cortico-cortical connectivity in alternative to dual-coil TMS methodology.

Dissociation between sustained single-neuron spiking and transient β-LFP oscillations in primate motor cortex.

Determining the relationship between single-neuron spiking and transient (20 Hz) β-local field potential (β-LFP) oscillations is an important step for understanding the role of these oscillations in motor cortex. We show that whereas motor cortex firing rates and beta spiking rhythmicity remain sustained during steady-state movement preparation periods, β-LFP oscillations emerge, in contrast, as short transient events. Single-neuron mean firing rates within and outside transient β-LFP events showed no differences, and no consistent correlation was found between the beta oscillation amplitude and firing rates, as was the case for movement- and visual cue-related β-LFP suppression. Importantly, well-isolated single units featuring beta-rhythmic spiking (43%, 125/292) showed no apparent or only weak phase coupling with the transient β-LFP oscillations. Similar results were obtained for the population spiking. These findings were common in triple microelectrode array recordings from primary motor (M1), ventral (PMv), and dorsal premotor (PMd) cortices in nonhuman primates during movement preparation. Although beta spiking rhythmicity indicates strong membrane potential fluctuations in the beta band, it does not imply strong phase coupling with β-LFP oscillations. The observed dissociation points to two different sources of variation in motor cortex β-LFPs: one that impacts single-neuron spiking dynamics and another related to the generation of mesoscopic β-LFP signals. Furthermore, our findings indicate that rhythmic spiking and diverse neuronal firing rates, which encode planned actions during movement preparation, may naturally limit the ability of different neuronal populations to strongly phase-couple to a single dominant oscillation frequency, leading to the observed spiking and β-LFP dissociation.NEW & NOTEWORTHY We show that whereas motor cortex spiking rates and beta (~20 Hz) spiking rhythmicity remain sustained during steady-state movement preparation periods, β-local field potential (β-LFP) oscillations emerge, in contrast, as transient events. Furthermore, the β-LFP phase at which neurons spike drifts: phase coupling is typically weak or absent. This dissociation points to two sources of variation in the level of motor cortex beta: one that impacts single-neuron spiking and another related to the generation of measured mesoscopic β-LFPs.

Encoding of Both Reaching and Grasping Kinematics in Dorsal and Ventral Premotor Cortices.

Classically, it has been hypothesized that reach-to-grasp movements arise from two discrete parietofrontal cortical networks. As part of these networks, the dorsal premotor cortex (PMd) has been implicated in the control of reaching movements of the arm, whereas the ventral premotor cortex (PMv) has been associated with the control of grasping movements of the hand. Recent studies have shown that such a strict delineation of function along anatomical boundaries is unlikely, partly because reaching to different locations can alter distal hand kinematics and grasping different objects can affect kinematics of the proximal arm. Here, we used chronically implanted multielectrode arrays to record unit-spiking activity in both PMd and PMv simultaneously while rhesus macaques engaged in a reach-to-grasp task. Generalized linear models were used to predict the spiking activity of cells in both areas as a function of different kinematic parameters, as well as spike history. To account for the influence of reaching on hand kinematics and vice versa, we applied demixed principal components analysis to define kinematics synergies that maximized variance across either different object locations or grip types. We found that single cells in both PMd and PMv encode the kinematics of both reaching and grasping synergies, suggesting that this classical division of reach and grasp in PMd and PMv, respectively, does not accurately reflect the encoding preferences of cells in those areas.SIGNIFICANCE STATEMENT For reach-to-grasp movements, the dorsal premotor cortex (PMd) has been implicated in the control of reaching movements of the arm, whereas the ventral premotor cortex (PMv) has been associated with the control of grasping movements of the hand. We recorded unit-spiking activity in PMd and PMv simultaneously while macaques performed a reach-to-grasp task. We modeled the spiking activity of neurons as a function of kinematic parameters and spike history. We applied demixed principal components analysis to define kinematics synergies. We found that single units in both PMd and PMv encode the kinematics of both reaching and grasping synergies, suggesting that the division of reach and grasp in PMd and PMv, respectively, cannot be made based on their encoding properties.

Who's that Knocking at My Door? Neural Bases of Sound Source Identification.

When hearing knocking on a door, a listener typically identifies both the action (forceful and repeated impacts) and the object (a thick wooden board) causing the sound. The current work studied the neural bases of sound source identification by switching listeners' attention toward these different aspects of a set of simple sounds during functional magnetic resonance imaging scanning: participants either discriminated the action or the material that caused the sounds, or they simply discriminated meaningless scrambled versions of them. Overall, discriminating action and material elicited neural activity in a left-lateralized frontoparietal network found in other studies of sound identification, wherein the inferior frontal sulcus and the ventral premotor cortex were under the control of selective attention and sensitive to task demand. More strikingly, discriminating materials elicited increased activity in cortical regions connecting auditory inputs to semantic, motor, and even visual representations, whereas discriminating actions did not increase activity in any regions. These results indicate that discriminating and identifying material requires deeper processing of the stimuli than discriminating actions. These results are consistent with previous studies suggesting that auditory perception is better suited to comprehend the actions than the objects producing sounds in the listeners' environment.

Causal role of ventral premotor cortex during observation of transitive actions

Event Abstract Back to Event Causal role of ventral premotor cortex during observation of transitive actions Guy Rens1* and Marco Davare1, 2 1 KU Leuven, Department of Kinesiology, Belgium 2 University College London, Sobell Department of Motor Neuroscience and Movement Disorders, United Kingdom In monkeys, neurons in F5 become active both when the monkey performs an action and when the monkey observes a similar action performed by the experimenter (mirror neurons). Using double coil transcranial magnetic stimulation (TMS) in healthy subjects (n=16), we investigated whether short-latency interactions between the ventral premotor cortex (PMv, the homologue of F5 in monkeys) and the primary motor cortex (M1) are modulated by the observation of different types of actions. We further compared PMv-M1 interactions during observation and execution of the same actions. Finally we investigated the causal contribution of PMv to the increase in corticospinal excitability (motor resonance) occurring during action observation. PMv-M1 interactions were tested before and after a train of continuous theta-burst stimulation (cTBS) to PMv during four experimental conditions: (1) object presentation (pen or disc), (2) observation of a transitive action towards an object (goal-directed), (3) observation of an intransitive action and (4) execution of the same actions. We found that both transitive and intransitive action observation modulated PMv-M1 interactions in a grasp-specific fashion (all p<0.011). For example, when observing the grasp of a pen, delivering a conditioning pulse over PMv 6 ms before a test pulse over M1 led to larger motor evoked potentials in muscles specifically required for the grasp. Following PMv cTBS, these grasp-specific PMv-M1 interactions were abolished (all p<0.001); in contrast, grasp-specific M1 resonance was still maintained for intransitive, but not transitive action observation (p=0.003). These results suggest that PMv has a causal role in mediating goal-directed information to M1 during observation of transitive actions. We suggest that other areas of the mirror neuron system enable motor resonance in M1 during intransitive actions. Our results shed new light on complex interactions between the different components of the action observation system. Keywords: TMS, ventral premotor cortex (PMv), action observation, theta burst stimulation, mirror neuron system, motor resonance, goal-directed actions Conference: 12th National Congress of the Belgian Society for Neuroscience, Gent, Belgium, 22 May - 22 May, 2017. Presentation Type: Poster Presentation Topic: Cognition and Behavior Citation: Rens G and Davare M (2019). Causal role of ventral premotor cortex during observation of transitive actions. Front. Neurosci. Conference Abstract: 12th National Congress of the Belgian Society for Neuroscience. doi: 10.3389/conf.fnins.2017.94.00007 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 02 May 2017; Published Online: 25 Jan 2019. * Correspondence: Mr. Guy Rens, KU Leuven, Department of Kinesiology, Heverlee, België, 3001, Belgium, rensguy1@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Guy Rens Marco Davare Google Guy Rens Marco Davare Google Scholar Guy Rens Marco Davare PubMed Guy Rens Marco Davare Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Altered praxis network underlying limb kinetic apraxia in Parkinson's disease - an fMRI study.

Parkinson's disease (PD) patients frequently suffer from dexterous deficits impeding activities of daily living. There is controversy whether impaired fine motor skill may stem from limb kinetic apraxia (LKA) rather than bradykinesia. Based on classical models of limb praxis LKA is thought to result when premotor transmission of time-space information of skilled movements to primary motor representations is interrupted. Therefore, using functional magnetic resonance imaging (fMRI) we tested the hypothesis that dexterous deficits in PD are associated with altered activity and connectivity in left parieto-premotor praxis network. Whole-brain analysis of fMRI activity during a task for LKA (coin rotation) showed increased activation of superior and inferior parietal lobule (SPL, IPL) and ventral premotor cortex (vPM) in PD patients compared to controls. For bradykinesia (assessed by finger tapping) a decreased fMRI activity could be detected in patients. Additionally, psychophysical interaction analysis showed increased functional connectivity between IPL and the posterior hippocampi in patients with PD. By contrast, functional connectivity to the right dorsolateral prefrontal cortex was decreased in patients with PD compared to controls.In conclusion, our data demonstrates that dexterous deficits in PD were associated with enhanced fMRI activation of the left praxis network upstream to primary motor areas, mirroring a neural correlate for the behavioral dissociation of LKA and bradykinesia. Furthermore, the findings suggest that patients recruit temporal areas of motor memory as an attempt to compensate for impaired motor skills. Finally, dysexecutive function may contribute to the deficit.

Common and distinct brain regions processing multisensory bodily signals for peripersonal space and body ownership

We take the feeling that our body belongs to us for granted. However, recent research has shown that it is possible to alter the subjective sensation of body ownership (BO) by manipulating multisensory bodily inputs. Several frontal and parietal regions are known to specifically process multisensory cues presented close to the body, i.e., within the peripersonal space (PPS). It has been proposed that these PPS fronto-parietal regions also underlie BO. However, most previous studies investigated the brain mechanisms of either BO or of PPS processing separately and by using a variety of paradigms. Here, we conducted an extensive meta-analysis of functional neuroimaging studies to investigate PPS and BO processing in humans in order to: a) assess quantitatively where each one of these functions was individually processed in the brain; b) identify whether and where these processes shared common or engaged distinct brain mechanisms; c) characterize these areas in terms of whole-brain co-activation networks and functions, respectively. We identified (i) a bilateral PPS network including superior parietal, temporo-parietal and ventral premotor regions and (ii) a BO network including posterior parietal cortex (right intraparietal sulcus, IPS; and left IPS and superior parietal lobule, SPL), right ventral premotor cortex, and the left anterior insula. Co-activation maps related to both PPS and BO encompassed largely overlapping fronto-parietal networks, but whereas the PPS network was more frequently associated with sensorimotor tasks, the BO network was rather associated with attention and awareness tasks. Finally, the conjunction analysis showed that (iii) PPS and BO tasks anatomically overlapped only in two clusters located in the left parietal cortex (dorsally at the intersection between the SPL, the IPS and area 2 and ventrally between areas 2 and IPS). Distinct activations were located for PPS at the temporo-parietal junction and for BO in the anterior insula. These results in PPS and BO and provide evidence-based insight about the overlap of the two processes in the IPS region and the extensive connectivity between the two associated co-activation networks. They also show significant dissociations, with PPS fronto-parietal areas located more proximal to the central sulcus than BO areas. Such anatomical distinction may also reflect the different functions of the two processes, whereby PPS areas underlie a multisensory-motor interface for body-objects interaction and BO areas being involved in bodily awareness and self-consciousness.

How specialized are writing-specific brain regions? An fMRI study of writing, drawing and oral spelling

Several brain imaging studies identified brain regions that are consistently involved in writing tasks; the left premotor and superior parietal cortices have been associated with the peripheral components of writing performance as opposed to other regions that support the central, orthographic components. Based on a meta-analysis by Planton, Jucla, Roux, and Demonet (2013), we focused on five such writing areas and questioned the task-specificity and hemispheric lateralization profile of the brain response in an functional magnetic resonance imaging (fMRI) experiment where 16 right-handed participants wrote down, spelled out orally object names, and drew shapes from object pictures. All writing-related areas were activated by drawing, and some of them by oral spelling, thus questioning their specialization for written production. The graphemic/motor frontal area (GMFA), a subpart of the superior premotor cortex close to Exner's area (Roux et al., 2009), was the only area with a writing-specific lateralization profile, that is, clear left lateralization during handwriting, and bilateral activity during drawing. Furthermore, the relative lateralization and levels of activation in the superior parietal cortex, ventral premotor cortex, ventral occipitotemporal cortex and right cerebellum across the three tasks brought out new evidence regarding their respective contributions to the writing processes.

Functional Organization of the Cerebral Cortex in Cued and Implicit Modality-Specific Anticipatory Attention. Analysis of α-Rhythm Coherence in the Sources Space

Studies in healthy right-handed subjects (N = 16, mean age 23 ± 5.7 years) analyzed the functional organization of the cerebral cortex during preparation to solve visual and auditory sensory tasks in two conditions: (1) anticipation of a visual or auditory signal after being told its modality (cued anticipatory attention) and (2) implicit anticipation formed during multiple repetition of a given sequence of visual and auditory stimuli. In both conditions subjects had to perform the same task – to identify the order of the stimuli (visual or auditory) in monomodal pairs. During the prestimulus period, the α frequency range was used to assess the coherence of cortical sources corresponding to previously selected cortical regions (regions of interest). More functional connections between cortical zones in the frontoparietal modulatory system were seen in cued anticipatory attention than during the period preceding appearance of the prompt stimulus, this obtaining in both sensory tasks. There was also a greater number of local connections between sensory-specific and associative (parietal and prefrontal) areas. Implicit anticipation preceding execution of the visual task was accompanied by an increase in connections between the ventral premotor cortex and the caudal (parietal and occipital) areas of the right hemisphere. Execution of the auditory task was preceded by an increase in connections between the auditory sensory cortex, the rostral part of the supplementary motor area, and the ventral premotor area. In contrast to cued attention, implicit anticipation was not accompanied by changes in frontoparietal connections. These results provide evidence of significant differences in the cerebral organization of these two types of anticipatory attention.

The Desire for Amputation or Paralyzation: Evidence for Structural Brain Anomalies in Body Integrity Identity Disorder (BIID).

BackgroundBody Integrity Identity Disorder (BIID) is a condition in which individuals perceive a mismatch between their internal body scheme and physical body shape, resulting in an absolute desire to be either amputated or paralyzed. The condition is hypothesized to be of congenital nature, but evidence for a neuro-anatomical basis is sparse.MethodsWe collected T1-weighted structural magnetic resonance imaging scans on a 3T scanner in eight individuals with BIID and 24 matched healthy controls, and analyzed the data using voxel-based morphometry.ResultsThe results showed reduced grey matter volume in the left dorsal and ventral premotor cortices and larger grey matter volume in the cerebellum (lobule VIIa) in individuals with BIID compared to controls.ConclusionThe premotor cortex and cerebellum are thought to be crucial for the experience of body-ownership and the integration of multisensory information. Our results suggest that BIID is associated with structural brain anomalies and might result from a dysfunction in the integration of multisensory information, leading to the feeling of disunity between the mental and physical body shape.

Functional Parcellation of Frontal Higher Order Motor Cortex

Motor areas in the frontal cortex are classified into medial and lateral functional groups. The dorsal premotor areas in the lateral groups are involved in motor guidance based on behavioral rules. The ventral premotor cortex contributes to motor guidance relying on spatial aspects of sensory information. The supplementary motor complex in the medial groups is related to the bimanual and temporal organization of multiple motor acts. The cingulate motor area is involved in motor control based on reward-prediction errors. The supplementary eye field is involved in monitoring performance and the adjustment of sequential visual search. The motor areas are coordinated in a context-dependent manner, influenced by top-down signals from the prefrontal cortex and by bottom-up signals from the parietal cortex, which are also organized into the lateral and medial functional groups. Evidence suggests that the medial and lateral functional groups are balanced by the insula cortex and anterior cingulate cortex which serve as salience detectors for changes in bodily states.

Visuomotor signals for reaching movements in the rostro-dorsal sector of the monkey thalamic reticular nucleus.

The thalamic reticular nucleus (TRN) collects inputs from the cerebral cortex and thalamus and, in turn, sends inhibitory outputs to the thalamic relay nuclei. This unique connectivity suggests that the TRN plays a pivotal role in regulating information flow through the thalamus. Here, we analyzed the roles of TRN neurons in visually guided reaching movements. We first used retrograde transneuronal labeling with rabies virus, and showed that the rostro-dorsal sector of the TRN (TRNrd) projected disynaptically to the ventral premotor cortex (PMv). In other experiments, we recorded neurons from the TRNrd or PMv while monkeys performed a visuomotor task. We found that neurons in the TRNrd and PMv showed visual-, set-, and movement-related activity modulation. These results indicate that the TRNrd, as well as the PMv, is involved in the reception of visual signals and in the preparation and execution of reaching movements. The fraction of neurons that were non-selective for the location of visual signals or the direction of reaching movements was greater in the TRNrd than in the PMv. Furthermore, the fraction of neurons whose activity increased from the baseline was greater in the TRNrd than in the PMv. The timing of activity modulation of visual-related and movement-related neurons was similar in TRNrd and PMv neurons. Overall, our data suggest that TRNrd neurons provide motor thalamic nuclei with inhibitory inputs that are predominantly devoid of spatial selectivity, and that these signals modulate how these nuclei engage in both sensory processing and motor output during visually guided reaching behavior.

Multivariate Pattern Analysis Reveals Category-Related Organization of Semantic Representations in Anterior Temporal Cortex.

The neural substrates of semantic representation have been the subject of much controversy. The study of semantic representations is complicated by difficulty in disentangling perceptual and semantic influences on neural activity, as well as in identifying stimulus-driven, "bottom-up" semantic selectivity unconfounded by top-down task-related modulations. To address these challenges, we trained human subjects to associate pseudowords (TPWs) with various animal and tool categories. To decode semantic representations of these TPWs, we used multivariate pattern classification of fMRI data acquired while subjects performed a semantic oddball detection task. Crucially, the classifier was trained and tested on disjoint sets of TPWs, so that the classifier had to use the semantic information from the training set to correctly classify the test set. Animal and tool TPWs were successfully decoded based on fMRI activity in spatially distinct subregions of the left medial anterior temporal lobe (LATL). In addition, tools (but not animals) were successfully decoded from activity in the left inferior parietal lobule. The tool-selective LATL subregion showed greater functional connectivity with left inferior parietal lobule and ventral premotor cortex, indicating that each LATL subregion exhibits distinct patterns of connectivity. Our findings demonstrate category-selective organization of semantic representations in LATL into spatially distinct subregions, continuing the lateral-medial segregation of activation in posterior temporal cortex previously observed in response to images of animals and tools, respectively. Together, our results provide evidence for segregation of processing hierarchies for different classes of objects and the existence of multiple, category-specific semantic networks in the brain. The location and specificity of semantic representations in the brain are still widely debated. We trained human participants to associate specific pseudowords with various animal and tool categories, and used multivariate pattern classification of fMRI data to decode the semantic representations of the trained pseudowords. We found that: (1) animal and tool information was organized in category-selective subregions of medial left anterior temporal lobe (LATL); (2) tools, but not animals, were encoded in left inferior parietal lobe; and (3) LATL subregions exhibited distinct patterns of functional connectivity with category-related regions across cortex. Our findings suggest that semantic knowledge in LATL is organized in category-related subregions, providing evidence for the existence of multiple, category-specific semantic representations in the brain.

Grasp-specific motor resonance is influenced by the visibility of the observed actor

Motor resonance is the modulation of M1 corticospinal excitability induced by observation of others' actions. Recent brain imaging studies have revealed that viewing videos of grasping actions led to a differential activation of the ventral premotor cortex depending on whether the entire person is viewed versus only their disembodied hand. Here we used transcranial magnetic stimulation (TMS) to examine motor evoked potentials (MEPs) in the first dorsal interosseous (FDI) and abductor digiti minimi (ADM) during observation of videos or static images in which a whole person or merely the hand was seen reaching and grasping a peanut (precision grip) or an apple (whole hand grasp). Participants were presented with six visual conditions in which visual stimuli (video vs static image), view (whole person vs hand) and grasp (precision grip vs whole hand grasp) were varied in a 2 × 2 × 2 factorial design. Observing videos, but not static images, of a hand grasping different objects resulted in a grasp-specific interaction, such that FDI and ADM MEPs were differentially modulated depending on the type of grasp being observed (precision grip vs whole hand grasp). This interaction was present when observing the hand acting, but not when observing the whole person acting. Additional experiments revealed that these results were unlikely to be due to the relative size of the hand being observed. Our results suggest that observation of videos rather than static images is critical for motor resonance. Importantly, observing the whole person performing the action abolished the grasp-specific effect, which could be due to a variety of PMv inputs converging on M1.

Effects of Forced Use on the Ventral Premotor Cortex Distal Forelimb Representation After Ischemic Infarct in Primary Motor Cortex

Effects of Forced Use on the Ventral Premotor Cortex Distal Forelimb Representation After Ischemic Infarct in Primary Motor Cortex