Multimodal representation of space in the posterior parietal cortex and its use in planning movements

Measuring instability in chronic human intracortical neural recordings towards stable, long-term brain-computer interfaces

Intracortical brain-computer interfaces (iBCIs) enable people with tetraplegia to gain intuitive cursor control from movement intentions. To translate to practical use, iBCIs should provide reliable performance for extended periods of time. However, performance begins to degrade as the relationship between kinematic intention and recorded neural activity shifts compared to when the decoder was initially trained. In addition to developing decoders to better handle long-term instability, identifying when to recalibrate will also optimize performance. We propose a method, "MINDFUL", to measure instabilities in neural data for useful long-term iBCI, without needing labels of user intentions. Longitudinal data were analyzed from two BrainGate2 participants with tetraplegia as they used fixed decoders to control a computer cursor spanning 142 days and 28 days, respectively. We demonstrate a measure of instability that correlates with changes in closed-loop cursor performance solely based on the recorded neural activity (Pearson r = 0.93 and 0.72, respectively). This result suggests a strategy to infer online iBCI performance from neural data alone and to determine when recalibration should take place for practical long-term use.

New functional dissociations between prefrontal and parietal cortex during task switching: A combined fMRI and TMS study

Preparatory control in task-switching has been suggested to rely upon a set of distributed regions within a frontoparietal network, with frontal and parietal cortical areas cooperating to implement switch-specific preparation processes. Although recent causal evidence using transcranial magnetic stimulation (TMS) have generally supported this model, alternative results from both functional neuroimaging and neurophysiological studies have questioned the switch-specific role of both frontal and parietal cortices. The aim of the present study was to clarify the involvement of prefrontal and parietal areas in preparatory cognitive control. With this purpose, an fMRI study was conducted to identify the brain areas activated during cue events in a task-switching paradigm, indicating whether to switch or to repeat among numerical tasks. Then, TMS was applied over the specific coordinates previously identified through fMRI, that is, the right inferior frontal gyrus (IFG) and right intraparietal sulcus (IPS). Results revealed that TMS over the right IFG disrupted performance in both switch and repeat trails in terms of delayed responses as compared to Sham condition. In contrast, TMS over the right IPS selectively interfered performance in switch trials. These findings support a multi-component model of executive control with the IFG being involved in more general switch-unspecific process such as the episodic retrieval of goals, and the IPS being related to the implementation of switch-specific preparation mechanisms for activating stimulus-response mappings. The results are discussed within the framework of contemporary hierarchical models of prefrontal cortex organization, suggesting that distinct prefrontal areas may carry out coordinated functions in preparatory control.

Modulation of multisensory nociceptive neurons in monkey cortical area 7b and behavioral correlates

Wide-range thermoreceptive neurons (WRT-EN) in monkey cortical area 7b that encoded innocuous and nocuous cutaneous thermal and threatening visuosensory stimulation with high fidelity were studied to identify their multisensory integrative response properties. Emphasis was given to characterizing the spatial and temporal effects of threatening visuosensory input on the thermal stimulus-response properties of these multisensory nociceptive neurons. Threatening visuosensory stimulation was most efficacious in modulating thermal evoked responses when presented as a downward ("looming"), spatially congruent, approaching and closely proximal target in relation to the somatosensory receptive field. Both temporal alignment and misalignment of spatially aligned threatening visual and thermal stimulation significantly increased mean discharge frequencies above those evoked by thermal stimulation alone, particularly at near noxious (43°C) and mildly noxious (45°C) temperatures. The enhanced multisensory discharge frequencies were equivalent to the discharge frequency evoked by overtly noxious thermal stimulation alone at 47°C (monkey pain tolerance threshold). A significant increase in behavioral mean escape frequency with shorter escape latency was evoked by multisensory stimulation at near noxious temperature (43°C), which was equivalent to that evoked by noxious stimulation alone (47°C). The remarkable concordance of elevating both neural discharge and escape frequency from a nonnociceptive and prepain level by near noxious thermal stimulation to a nociceptive and pain level by multisensory visual and near noxious thermal stimulation and integration is an elegantly designed defensive neural mechanism that in effect lowers both nociceptive response and pain thresholds to preemptively engage nocifensive behavior and, consequently, avert impending and actual injurious noxious thermal stimulation.NEW & NOTEWORTHY Multisensory nociceptive neurons in cortical area 7b are engaged in integration of threatening visuosensory and a wide range of innocuous and nocuous somatosensory (thermoreceptive) inputs. The enhancement of neuronal activity and escape behavior in monkey by multisensory integration is consistent and supportive of human psychophysical studies. The spatial features of visuosensory stimulation in peripersonal space in relation to somatic stimulation in personal space are critical to multisensory integration, nociception, nocifensive behavior, and pain.

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

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

Let's do it: Response times in Mental Paper Folding and its execution

Action imagery is the ability to mentally simulate the execution of an action without physically performing it. Action imagery is assumed to rely at least partly on similar mechanisms as action execution. Therefore, we expected that imagery and execution durations would be constrained by the number of folds in a Paper Folding Task. Analogously, individual differences in execution durations were expected to be reflected in imagery durations. Twenty-eight participants performed two imagery conditions (computer vs. paper) and one execution condition (paper) where two-dimensional grids of a three-dimensional cube were (mentally) folded to determine whether two selected edges overlapped or not. As expected, imagery performance and execution performance were strongly correlated and decreased with the number of folds. Further, the number of folds influenced imagery durations even more than execution durations. This may be due to the additional cognitive load in imagery that emerges when tracking the folds to follow up with the next ones. The results indicate that Mental Paper Folding predominantly involves dynamic visual representations that are not functionally associated with one's own movements as in action imagery.

Preliminary investigation of SEZUAL device for basic material identification and simple spatial navigation for blind and visually impaired people

PURPOSE

we present a preliminary set of experimental studies that demonstrates device-aided echolocation enabling in blind and visually impaired individuals. The proposed device emits a click-like sound into the surrounding space and returning sound is perceived by participants to infer the surrounding environment.

MATERIALS AND METHODS

two sets of experiments were set up to evaluate the echolocation abilities of nine blind participants. The first setup was designed to identify four material types based on the sound reflection properties of materials, such as glass, metal, wood, and ceramics. The second setup was navigation through a basic maze with the device.

RESULTS

experimental data demonstrate that the use of the proposed device enables active echolocation abilities in blind participants, particularly for material identification and spatial mobility.

CONCLUSION

the proposed device can potentially be used to rehabilitate disabled blind and visually impaired individuals in terms of spatial mobility and orientation.

Neuroanatomical correlates of distracted straight driving performance: a driving simulator MRI study across the lifespan

Background

Driving is the preferred mode of transportation for adults across the healthy age span. However, motor vehicle crashes are among the leading causes of injury and death, especially for older adults, and under distracted driving conditions. Understanding the neuroanatomical basis of driving may inform interventions that minimize crashes. This exploratory study examined the neuroanatomical correlates of undistracted and distracted simulated straight driving.

Methods

One-hundred-and-thirty-eight participants (40.6% female) aged 17-85 years old (mean and SD = 58.1 ± 19.9 years) performed a simulated driving task involving straight driving and turns at intersections in a city environment using a steering wheel and foot pedals. During some straight driving segments, participants responded to auditory questions to simulate distracted driving. Anatomical T1-weighted MRI was used to quantify grey matter volume and cortical thickness for five brain regions: the middle frontal gyrus (MFG), precentral gyrus (PG), superior temporal cortex (STC), posterior parietal cortex (PPC), and cerebellum. Partial correlations controlling for age and sex were used to explore relationships between neuroanatomical measures and straight driving behavior, including speed, acceleration, lane position, heading angle, and time speeding or off-center. Effects of interest were noted at an unadjusted p-value threshold of 0.05.

Results

Distracted driving was associated with changes in most measures of straight driving performance. Greater volume and cortical thickness in the PPC and cerebellum were associated with reduced variability in lane position and heading angle during distracted straight driving. Cortical thickness of the MFG, PG, PPC, and STC were associated with speed and acceleration, often in an age-dependent manner.

Conclusion

Posterior regions were correlated with lane maintenance whereas anterior and posterior regions were correlated with speed and acceleration, especially during distracted driving. The regions involved and their role in straight driving may change with age, particularly during distracted driving as observed in older adults. Further studies should investigate the relationship between distracted driving and the aging brain to inform driving interventions.

Euterpe music therapy method for children with cerebral palsy

Introduction

The main purpose of our study was to evaluate whether involvement in a personalized music therapy program (Euterpe method), could improve the condition of children with cerebral palsy and their parents, compared to a control group. It investigated whether it could positively affect children's sleep quality, temperament and quality of life, quality of family life, and parental stress.

Methods

A prospective single-center experimental study was conducted at "Bambino Gesù" Children's Hospital (Rome, Italy). All subjects involved attended an intensive rehabilitation program in the Neurorehabilitation Unit. In a group of patients (n = 25), a music therapy treatment was applied to evaluate the effect before and after the intervention. This group was also compared with a control group (n = 10) undergoing a standard protocol without music therapy.

Results

In the experimental group, the analysis shows statistically significant effects in the Disorders of initiating and maintaining sleep (p = 0.050) and the Sleep wake transition disorders (p = 0.026) factors, and the total score (p = 0.031) of Sleep Disturbances Scale for Children; the Positive emotionality scale (p = 0.013) of Italian Questionnaires of Temperament (QUIT); the Emotional Functioning (p = 0.029), Social Functioning (p = 0.012), Worry (p = 0.032), Daily Activities (p = 0.032), Total Score (p = 0.039) and Parent HRQL Summary Score (p = 0.035) dimensions of Pediatric Quality of Life for family. While in the control group, only the Attention scale of QUIT (p = 0.003) reaches statistical significance.

Discussion

Our study suggests that music therapy with the Euterpe Method has beneficial effects on fundamental aspects of the child's and his parents' lives, such as sleep, emotion control, and quality of family life.

Oculomotor Impairments in Children After Posterior Fossa Tumors Treatment

Posterior fossa tumors (PFT) are the most common pediatric brain tumors, and the study of the somatic and cognitive status of PFT survivors still remains a critical problem. Since cerebellar damage can affect eye movement centers located in the vermis and hemispheres, such patients suffer from disturbances in visual perception, visual-spatial functions, reading, etc. Our investigation aimed at describing oculomotor impairments in PFT survivors linked to core oculomotor functions assessed through eye tracking method: gaze holding, reflexive saccades, and organization of voluntary saccades and their dependency on age at tumor diagnosis. Also, we investigated the relationship between oculomotor functions and ataxia measured with International Cooperative Ataxia Rating Scale (ICARS). A total of 110 children (patients and age-matched healthy controls, aged 9-17 years old) participated in the study. We found that the earlier the child had a tumor, the more impaired gaze holding (p = 0.0031) and fewer isometric saccades (p = 0.035) were observed at the time of examination. The above-mentioned functions in healthy controls improved with age. Visual scanning was also impaired compared to controls but was not related to age at diagnosis. A positive correlation between ICARS scores and number of hypermetric saccades (r = 0.309, p = 0.039), but no correlation with the number of hypometric saccades (r = - 0.008, p = 0.956). Furthermore, number of hypometric saccades did not differ between patients and controls (p = 0.238). Thus, primarily hypermetric saccades can be considered a prominent oculomotor symptom of cerebellar tumors. Our study provides basis for new methods of PFT diagnosis and rehabilitation procedure evaluation, both playing essential roles in modern pediatric neurooncology.

Modality-Independent Effect of Gravity in Shaping the Internal Representation of 3D Space for Visual and Haptic Object Perception

Visual and haptic perceptions of 3D shape are plagued by distortions, which are influenced by nonvisual factors, such as gravitational vestibular signals. Whether gravity acts directly on the visual or haptic systems or at a higher, modality-independent level of information processing remains unknown. To test these hypotheses, we examined visual and haptic 3D shape perception by asking male and female human subjects to perform a "squaring" task in upright and supine postures and in microgravity. Subjects adjusted one edge of a 3D object to match the length of another in each of the three canonical reference planes, and we recorded the matching errors to obtain a characterization of the perceived 3D shape. The results show opposing, body-centered patterns of errors for visual and haptic modalities, whose amplitudes are negatively correlated, suggesting that they arise in distinct, modality-specific representations that are nevertheless linked at some level. On the other hand, weightlessness significantly modulated both visual and haptic perceptual distortions in the same way, indicating a common, modality-independent origin for gravity's effects. Overall, our findings show a link between modality-specific visual and haptic perceptual distortions and demonstrate a role of gravity-related signals on a modality-independent internal representation of the body and peripersonal 3D space used to interpret incoming sensory inputs.

Irregularity of instantaneous gamma frequency in the motor control network characterize visuomotor and proprioceptive information processing

Objective.The study aims to characterize movements with different sensory goals, by contrasting the neural activity involved in processing proprioceptive and visuo-motor information. To accomplish this, we have developed a new methodology that utilizes the irregularity of the instantaneous gamma frequency parameter for characterization.Approach.In this study, eight essential tremor patients undergoing an awake deep brain stimulation implantation surgery repetitively touched the clinician's finger (forward visually-guided/FV movement) and then one's own chin (backward proprioceptively-guided/BP movement). Neural electrocorticographic recordings from the motor (M1), somatosensory (S1), and posterior parietal cortex (PPC) were obtained and band-pass filtered in the gamma range (30-80 Hz). The irregularity of the inter-event intervals (IEI; inverse of instantaneous gamma frequency) were examined as: (1) auto-information of the IEI time series and (2) correlation between the amplitude and its proceeding IEI. We further explored the network connectivity after segmenting the FV and BP movements by periods of accelerating and decelerating forces, and applying the IEI parameter to transfer entropy methods.Main results.Conceptualizing that the irregularity in IEI reflects active new information processing, we found the highest irregularity in M1 during BP movement, highest in PPC during FV movement, and the lowest during rest at all sites. Also, connectivity was the strongest from S1 to M1 and from S1 to PPC during FV movement with accelerating force and weakest during rest.Significance. We introduce a novel methodology that utilize the instantaneous gamma frequency (i.e. IEI) parameter in characterizing goal-oriented movements with different sensory goals, and demonstrate its use to inform the directional connectivity within the motor cortical network. This method successfully characterizes different movement types, while providing interpretations to the sensory-motor integration processes.

Measuring instability in chronic human intracortical neural recordings towards stable, long-term brain-computer interfaces

Intracortical brain-computer interfaces (iBCIs) enable people with tetraplegia to gain intuitive cursor control from movement intentions. To translate to practical use, iBCIs should provide reliable performance for extended periods of time. However, performance begins to degrade as the relationship between kinematic intention and recorded neural activity shifts compared to when the decoder was initially trained. In addition to developing decoders to better handle long-term instability, identifying when to recalibrate will also optimize performance. We propose a method to measure instability in neural data without needing to label user intentions. Longitudinal data were analyzed from two BrainGate2 participants with tetraplegia as they used fixed decoders to control a computer cursor spanning 142 days and 28 days, respectively. We demonstrate a measure of instability that correlates with changes in closed-loop cursor performance solely based on the recorded neural activity (Pearson r = 0.93 and 0.72, respectively). This result suggests a strategy to infer online iBCI performance from neural data alone and to determine when recalibration should take place for practical long-term use.

Object-oriented hand dexterity and grasping abilities, from the animal quarters to the neurosurgical OR: a systematic review of the underlying neural correlates in non-human, human primate and recent findings in awake brain surgery

Introduction

The sensorimotor integrations subserving object-oriented manipulative actions have been extensively investigated in non-human primates via direct approaches, as intracortical micro-stimulation (ICMS), cytoarchitectonic analysis and anatomical tracers. However, the understanding of the mechanisms underlying complex motor behaviors is yet to be fully integrated in brain mapping paradigms and the consistency of these findings with intraoperative data obtained during awake neurosurgical procedures for brain tumor removal is still largely unexplored. Accordingly, there is a paucity of systematic studies reviewing the cross-species analogies in neural activities during object-oriented hand motor tasks in primates and investigating the concordance with intraoperative findings during brain mapping. The current systematic review was designed to summarize the cortical and subcortical neural correlates of object-oriented fine hand actions, as revealed by fMRI and PET studies, in non-human and human primates and how those were translated into neurosurgical studies testing dexterous hand-movements during intraoperative brain mapping.

Methods

A systematic literature review was conducted following the PRISMA guidelines. PubMed, EMBASE and Web of Science databases were searched. Original articles were included if they: (1) investigated cortical activation sites on fMRI and/or PET during grasping task; (2) included humans or non-human primates. A second query was designed on the databases above to collect studies reporting motor, hand manipulation and dexterity tasks for intraoperative brain mapping in patients undergoing awake brain surgery for any condition. Due to the heterogeneity in neurosurgical applications, a qualitative synthesis was deemed more appropriate.

Results

We provided an updated overview of the current state of the art in translational neuroscience about the extended frontoparietal grasping-praxis network with a specific focus on the comparative functioning in non-human primates, healthy humans and how the latter knowledge has been implemented in the neurosurgical operating room during brain tumor resection.

Discussion

The anatomical and functional correlates we reviewed confirmed the evolutionary continuum from monkeys to humans, allowing a cautious but practical adoption of such evidence in intraoperative brain mapping protocols. Integrating the previous results in the surgical practice helps preserve complex motor abilities, prevent long-term disability and poor quality of life and allow the maximal safe resection of intrinsic brain tumors.

Crossmodal Associations and Working Memory in the Brain

Crossmodal associations between stimuli from different sensory modalities could emerge in non-synesthetic people and be stored in working memory to guide goal-directed behaviors. This chapter reviews a plethora of studies in this field to summarize where, when, and how crossmodal associations and working memory are processed. It has been found that in those brain regions that are traditionally considered as unimodal primary sensory areas, neural activity could be influenced by crossmodal sensory signals at temporally very early stage of information processing. This phenomenon could not be due to feedback projections from higher level associative areas. Sequentially, neural processes would then occur in associative cortical areas including the posterior parietal cortex and prefrontal cortex. Neural oscillations in multiple frequency bands may reflect brain activity in crossmodal associations, and it is likely that neural synchrony is related to potential neural mechanisms underlying these processes. Primary sensory areas and associative areas coordinate together through neural synchrony to fulfil crossmodal associations and to guide working memory performance.

Effect of dual-task interaction combining postural and visual perturbations on cortical activity and postural control ability

Previous studies have suggested cortical involvement in postural control in humans by measuring cortical activities and conducting dual-task paradigms. In dual-task paradigms, task performance deteriorates and can be facilitated in specific dual-task settings. Theoretical frameworks explaining these dual-task interactions have been proposed and debated for decades. Therefore, we investigated postural control performance under different visual conditions using a virtual reality system, simultaneously measuring cortical activities with a functional near-infrared spectroscopy system. Twenty-four healthy participants were included in this study. Postural stability and cortical activities after perturbations were measured under several conditions consisting of postural and visual perturbations. The results showed that concurrent visual and postural perturbations could facilitate cortical activities in the supplementary motor area and superior parietal lobe. Additionally, visual distractors deteriorated postural control ability and cortical activation of the supplementary motor area. These findings supported the theoretical framework of the "Cross talk model", in which concurrent tasks using similar neural domains can facilitate these task performances. Furthermore, it indicated that the cortical resource capacity and domains activated for information processing should be considered in experiments involving dual-task paradigms and training.

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

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

Sensorimotor adaptation in spatial orientation task: a fNIRS study

In sensorimotor conflicts, the brain forms and updates a new sensorimotor relationship through sensorimotor integration. As humans adapt to new sensorimotor mapping, goal-directed movements become increasingly precise. Using functional near-infrared spectroscopy, we investigated the changes in cortical activity during sensorimotor adaptation in a spatial orientation task with sensorimotor conflict. Individuals performed a reversed spatial orientation training in which the visual feedback guiding hand movements was reversed. We measured cortical activity and spatial orientation performance, including the response time, completion number, error, and accuracy. The results revealed the continuous activation in the left SMG during sensorimotor adaptation and decreased activation in the right SAC, AG and SMG after sensorimotor adaptation. These findings indicated the contribution of the left SMG to sensorimotor adaptation and the improved efficiency of cortical activity after sensorimotor adaptation, respectively. Our studies suggest the neural mechanisms related to sensorimotor adaptation to a reversed spatial orientation task.

Turning Attention Inside Out: How Working Memory Serves Behavior

Flexible behavior requires guidance not only by sensations that are available immediately but also by relevant mental contents carried forward through working memory. Therefore, selective-attention functions that modulate the contents of working memory to guide behavior (inside-out) are just as important as those operating on sensory signals to generate internal contents (outside-in). We review the burgeoning literature on selective attention in the inside-out direction and underscore its functional, flexible, and future-focused nature. We discuss in turn the purpose (why), targets (what), sources (when), and mechanisms (how) of selective attention inside working memory, using visual working memory as a model. We show how the study of internal selective attention brings new insights concerning the core cognitive processes of attention and working memory and how considering selective attention and working memory together paves the way for a rich and integrated understanding of how mind serves behavior.

Thalamocortical and corticothalamic connections of multiple functional domains in posterior parietal cortex of galagos

In prosimian galagos, the posterior parietal cortex (PPC) is subdivided into a number of functional domains where long-train intracortical microstimulation evoked different types of complex movements. Here, we placed anatomical tracers in multiple locations of PPC to reveal the origins and targets of thalamic connections of four PPC domains for different types of hindlimb, forelimb, or face movements. Thalamic connections of all four domains included nuclei of the motor thalamus, ventral anterior and ventral lateral nuclei, as well as parts of the sensory thalamus, the anterior pulvinar, posterior and ventral posterior superior nuclei, consistent with the sensorimotor functions of PPC domains. PPC domains also projected to the thalamic reticular nucleus in a somatotopic pattern. Quantitative differences in the distributions of labeled neurons in thalamic nuclei suggested that connectional patterns of these domains differed from each other.

Mental Paper Folding Revisited: The Involvement of Visual Action Imagery

Action imagery describes a mental representation of an action and its consequences. Although it is widely recognized that people differ in their ability to imagine actions, objective validated tests to measure such differences are scarce. In search of an objective testing method for action imagery ability, the present study investigated whether solving mental paper-folding tasks involves action imagery. The stimuli were two-dimensional grids of six squares. A total of 99 participants mentally folded each grid into a three-dimensional cube to judge whether two highlighted lines in the grid overlapped in the imagined cube. This was done in two sessions of 214 judgements each, where the grids differed in overlaps, the least number of imagined folds, and the least number of imagined directional changes. Error rates and reaction times increased with the number of imagined folds and with the number of directional changes. Furthermore, more errors were committed with overlapping lines than with no overlaps. This was not reflected in the reaction times. Hence, the reaction times increased when the stepwise folding process was enlarged, but not when the final selection was more difficult. We concluded that the participants predominantly used action imagery as a task-solving strategy rather than for abstract problem-solving.

A Neurosurgical Functional Dissection of the Middle Precentral Gyrus during Speech Production

Classical models have traditionally focused on the left posterior inferior frontal gyrus (Broca's area) as a key region for motor planning of speech production. However, converging evidence suggests that it is not critical for either speech motor planning or execution. Alternative cortical areas supporting high-level speech motor planning have yet to be defined. In this review, we focus on the precentral gyrus, whose role in speech production is often thought to be limited to lower-level articulatory muscle control. In particular, we highlight neurosurgical investigations that have shed light on a cortical region anatomically located near the midpoint of the precentral gyrus, hence called the middle precentral gyrus (midPrCG). The midPrCG is functionally located between dorsal hand and ventral orofacial cortical representations and exhibits unique sensorimotor and multisensory functions relevant for speech processing. This includes motor control of the larynx, auditory processing, as well as a role in reading and writing. Furthermore, direct electrical stimulation of midPrCG can evoke complex movements, such as vocalization, and selective injury can cause deficits in verbal fluency, such as pure apraxia of speech. Based on these findings, we propose that midPrCG is essential to phonological-motoric aspects of speech production, especially syllabic-level speech sequencing, a role traditionally ascribed to Broca's area. The midPrCG is a cortical brain area that should be included in contemporary models of speech production with a unique role in speech motor planning and execution.

The effects of bilateral posterior parietal cortex tRNS on reading performance

According to established cognitive neuroscience knowledge based on studies on disabled and typically developing readers, reading is based on a dual-stream model in which a phonological-dorsal stream (left temporo-parietal and inferior frontal areas) processes unfamiliar words and pseudowords, whereas an orthographic-ventral stream (left occipito-temporal and inferior frontal areas) processes known words. However, correlational neuroimaging, causal longitudinal, training, and pharmacological studies have suggested the critical role of visuo-spatial attention in reading development. In a double blind, crossover within-subjects experiment, we manipulated the neuromodulatory effect of a short-term bilateral stimulation of posterior parietal cortex (PPC) by using active and sham tRNS during reading tasks in a large sample of young adults. In contrast to the dual-stream model predicting either no effect or a selective effect on the stimulated phonological-dorsal stream (as well as to a general multisensory effect on both reading streams), we found that only word-reading performance improved after active bilateral PPC tRNS. These findings demonstrate a direct neural connectivity between the PPC, controlling visuo-spatial attention, and the ventral stream for visual word recognition. These results support a neurobiological model of reading where performance of the orthographic-ventral stream is boosted by an efficient deployment of visuo-spatial attention from bilateral PPC stimulation.

Multisensory representations of space and time in sensory cortices

Clear evidence demonstrated a supramodal organization of sensory cortices with multisensory processing occurring even at early stages of information encoding. Within this context, early recruitment of sensory areas is necessary for the development of fine domain-specific (i.e., spatial or temporal) skills regardless of the sensory modality involved, with auditory areas playing a crucial role in temporal processing and visual areas in spatial processing. Given the domain-specificity and the multisensory nature of sensory areas, in this study, we hypothesized that preferential domains of representation (i.e., space and time) of visual and auditory cortices are also evident in the early processing of multisensory information. Thus, we measured the event-related potential (ERP) responses of 16 participants while performing multisensory spatial and temporal bisection tasks. Audiovisual stimuli occurred at three different spatial positions and time lags and participants had to evaluate whether the second stimulus was spatially (spatial bisection task) or temporally (temporal bisection task) farther from the first or third audiovisual stimulus. As predicted, the second audiovisual stimulus of both spatial and temporal bisection tasks elicited an early ERP response (time window 50-90 ms) in visual and auditory regions. However, this early ERP component was more substantial in the occipital areas during the spatial bisection task, and in the temporal regions during the temporal bisection task. Overall, these results confirmed the domain specificity of visual and auditory cortices and revealed that this aspect selectively modulates also the cortical activity in response to multisensory stimuli.

Age-related decrease in motor contribution to multisensory reaction times in primary school children

Traditional measurement of multisensory facilitation in tasks such as speeded motor reaction tasks (MRT) consistently show age-related improvement during early childhood. However, the extent to which motor function increases with age and hence contribute to multisensory motor reaction times in young children has seldom been examined. Thus, we aimed to investigate the contribution of motor development to measures of multisensory (auditory, visual, and audiovisual) and visuomotor processing tasks in three young school age groups of children (n = 69) aged (5-6, n = 21; 7-8, n = 25.; 9-10 n = 18 years). We also aimed to determine whether age-related sensory threshold times for purely visual inspection time (IT) tasks improved significantly with age. Bayesian results showed decisive evidence for age-group differences in multisensory MRT and visuo-motor processing tasks, though the evidence showed that threshold time for visual identification IT performance was only slower in the youngest age group children (5-6) compared to older groups. Bayesian correlations between performance on the multisensory MRT and visuo-motor processing tasks indicated moderate to decisive evidence in favor of the alternative hypothesis (BF10 = 4.71 to 91.346), though not with the threshold IT (BF10 < 1.35). This suggests that visual sensory system development in children older than 6 years makes a less significant contribution to the measure of multisensory facilitation, compared to motor development. In addition to this main finding, multisensory facilitation of MRT within race-model predictions was only found in the oldest group of children (9-10), supporting previous suggestions that multisensory integration is likely to continue into late childhood/early adolescence at least.

The neural response is heightened when watching a person approaching compared to walking away: Evidence for dynamic social neuroscience

The action observation network has been proposed to play a key role in predicting the action intentions (or goals) of others, thereby facilitating social interaction. Key information when interacting with others is whether someone (an agent) is moving towards or away from us, indicating whether we are likely to interact with the person. In addition, to determine the nature of a social interaction, we also need to take into consideration the distance of the agent relative to us as the observer. How this kind of information is processed within the brain is unknown, at least in part because prior studies have not involved live whole-body motion. Consequently, here we recorded mobile EEG in 18 healthy participants, assessing the neural response to the modulation of direction (walking towards or away) and distance (near vs. far distance) during the observation of an agent walking. We evaluated whether cortical alpha and beta oscillations were modulated differently by direction and distance during action observation. We found that alpha was only modulated by distance, with a stronger decrease of power when the agent was further away from the observer, regardless of direction. Critically, by contrast, beta was found to be modulated by both distance and direction, with a stronger decrease of power when the agent was near and facing the participant (walking towards) compared to when they were near but viewed from the back (walking away). Analysis revealed differences in both the timing and distribution of alpha and beta oscillations. We argue that these data suggest a full understanding of action observation requires a new dynamic neuroscience, investigating actual interactions between real people, in real world environments.

Hierarchical Reinforcement Learning, Sequential Behavior, and the Dorsal Frontostriatal System

To effectively behave within ever-changing environments, biological agents must learn and act at varying hierarchical levels such that a complex task may be broken down into more tractable subtasks. Hierarchical reinforcement learning (HRL) is a computational framework that provides an understanding of this process by combining sequential actions into one temporally extended unit called an option. However, there are still open questions within the HRL framework, including how options are formed and how HRL mechanisms might be realized within the brain. In this review, we propose that the existing human motor sequence literature can aid in understanding both of these questions. We give specific emphasis to visuomotor sequence learning tasks such as the discrete sequence production task and the M × N (M steps × N sets) task to understand how hierarchical learning and behavior manifest across sequential action tasks as well as how the dorsal cortical-subcortical circuitry could support this kind of behavior. This review highlights how motor chunks within a motor sequence can function as HRL options. Furthermore, we aim to merge findings from motor sequence literature with reinforcement learning perspectives to inform experimental design in each respective subfield.

Source Localization of Audiovisual Multisensory Neural Generators in Young Adults with Attention-Deficit/Hyperactivity Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder that exhibits unique neurological and behavioural characteristics. Our previous work using event-related potentials demonstrated that adults with ADHD process audiovisual multisensory stimuli somewhat differently than neurotypical controls. This study utilised an audiovisual multisensory two-alternative forced-choice discrimination task. Continuous whole-head electroencephalography (EEG) was recorded. Source localization (sLORETA) software was utilised to determine differences in the contribution made by sources of neural generators pertinent to audiovisual multisensory processing in those with ADHD versus neurotypical controls. Source localization techniques elucidated that the controls had greater neural activity 164 ms post-stimulus onset when compared to the ADHD group, but only when responding to audiovisual stimuli. The source of the increased activity was found to be Brodmann Area 2, postcentral gyrus, right-hemispheric parietal lobe referenced to Montreal Neurological Institute (MNI) coordinates of X = 35, Y = −40, and Z = 70 (p < 0.05). No group differences were present during either of the unisensory conditions. Differences in the integration areas, particularly in the right-hemispheric parietal brain regions, were found in those with ADHD. These alterations may correspond to impaired attentional capabilities when presented with multiple simultaneous sensory inputs, as is the case during a multisensory condition.

Impaired body-centered sensorimotor transformations in congenitally deaf people

Congenital deafness modifies an individual’s daily interaction with the environment and alters the fundamental perception of the external world. How congenital deafness shapes the interface between the internal and external worlds remains poorly understood. To interact efficiently with the external world, visuospatial representations of external target objects need to be effectively transformed into sensorimotor representations with reference to the body. Here, we tested the hypothesis that egocentric body-centred sensorimotor transformation is impaired in congenital deafness. Consistent with this hypothesis, we found that congenital deafness induced impairments in egocentric judgements, associating the external objects with the internal body. These impairments were due to deficient body-centred sensorimotor transformation per se, rather than the reduced fidelity of the visuospatial representations of the egocentric positions. At the neural level, we first replicated the previously well-documented critical involvement of the frontoparietal network in egocentric processing, in both congenitally deaf participants and hearing controls. However, both the strength of neural activity and the intra-network connectivity within the frontoparietal network alone could not account for egocentric performance variance. Instead, the inter-network connectivity between the task-positive frontoparietal network and the task-negative default-mode network was significantly correlated with egocentric performance: the more cross-talking between them, the worse the egocentric judgement. Accordingly, the impaired egocentric performance in the deaf group was related to increased inter-network connectivity between the frontoparietal network and the default-mode network and decreased intra-network connectivity within the default-mode network. The altered neural network dynamics in congenital deafness were observed for both evoked neural activity during egocentric processing and intrinsic neural activity during rest. Our findings thus not only demonstrate the optimal network configurations between the task-positive and -negative neural networks underlying coherent body-centred sensorimotor transformations but also unravel a critical cause (i.e. impaired body-centred sensorimotor transformation) of a variety of hitherto unexplained difficulties in sensory-guided movements the deaf population experiences in their daily life.

Robust Coding of Eye Position in Posterior Parietal Cortex despite Context-Dependent Tuning

Neurons in posterior parietal cortex (PPC) encode many aspects of the sensory world (e.g., scene structure), the posture of the body, and plans for action. For a downstream computation, however, only some of these dimensions are relevant; the rest are "nuisance variables" because their influence on neural activity changes with sensory and behavioral context, potentially corrupting the read-out of relevant information. Here we show that a key postural variable for vision (eye position) is represented robustly in male macaque PPC across a range of contexts, although the tuning of single neurons depended strongly on context. Contexts were defined by different stages of a visually guided reaching task, including (1) a visually sparse epoch, (2) a visually rich epoch, (3) a "go" epoch in which the reach was cued, and (4) during the reach itself. Eye position was constant within trials but varied across trials in a 3 × 3 grid spanning 24° × 24°. Using demixed principal component analysis of neural spike-counts, we found that the subspace of the population response encoding eye position is orthogonal to that encoding task context. Accordingly, a context-naive (fixed-parameter) decoder was nevertheless able to estimate eye position reliably across contexts. Errors were small given the sample size (∼1.78°) and would likely be even smaller with larger populations. Moreover, they were comparable to that of decoders that were optimized for each context. Our results suggest that population codes in PPC shield encoded signals from crosstalk to support robust sensorimotor transformations across contexts.SIGNIFICANCE STATEMENT Neurons in posterior parietal cortex (PPC) which are sensitive to gaze direction are thought to play a key role in spatial perception and behavior (e.g., reaching, navigation), and provide a potential substrate for brain-controlled prosthetics. Many, however, change their tuning under different sensory and behavioral contexts, raising the prospect that they provide unreliable representations of egocentric space. Here, we analyze the structure of encoding dimensions for gaze direction and context in PPC during different stages of a visually guided reaching task. We use demixed dimensionality reduction and decoding techniques to show that the coding of gaze direction in PPC is mostly invariant to context. This suggests that PPC can provide reliable spatial information across sensory and behavioral contexts.

Modulation of subjective peripheral sensation, F-waves, and somatosensory evoked potentials in response to unilateral pinch task measured on the contractile and non-contractile sides

Depression of the sensory input during voluntary muscle contractions has been demonstrated using electrophysiological methods in both animals and humans. However, the association between electrophysiological responses of the sensory system and subjective peripheral sensation (SPS) during a voluntary muscle contraction remains unclear. This study aimed to describe the changes in SPS, spinal α-motoneuron excitability (F-wave to M-wave amplitude), and somatosensory evoked potentials (SEPs) during a unilateral pinch-grip task. Outcome variables were measured on the side ipsilateral and contralateral to the muscle contraction and at rest (control). Participants were 8 healthy men aged 20.9±0.8 years. The isometric pinch-grip task was performed at 30% of the maximum voluntary isometric force measured for the right and left hands separately. The appearance rate of the F-wave during the task was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and control condition. Although there was no difference in the F-wave latency between hands and the control condition, the amplitude of the F-wave was significantly higher for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. There was no difference in the amplitude of the SEP at N20. However, the amplitude at P25 was significantly lower for the ipsilateral (right) hand than for the contralateral (left) hand and the control condition. The accuracy rate of detecting tactile stimulation, evaluated for 20 repetitions using a Semmes–Weinstein monofilament at the sensory threshold for each participant, was significantly lower during the pinch-grip task for both the ipsilateral (right) and contralateral (left) hands than in the control condition. Overall, our findings show that SPS and neurophysiological parameters were not modulated in parallel during the task, with changes in the subjective sensation preceding changes in electrophysiological indices during the motor task. Our findings provide basic information on sensory-motor coordination.

Entropy Could Quantify Brain Activation Induced by Mechanical Impedance-Restrained Active Arm Motion: A Functional NIRS Study

Brain activation has been used to understand brain-level events associated with cognitive tasks or physical tasks. As a quantitative measure for brain activation, we propose entropy in place of signal amplitude and beta value, which are widely used, but sometimes criticized for their limitations and shortcomings as such measures. To investigate the relevance of our proposition, we provided 22 subjects with physical stimuli through elbow extension-flexion motions by using our exoskeleton robot, measured brain activation in terms of entropy, signal amplitude, and beta value; and compared entropy with the other two. The results show that entropy is superior, in that its change appeared in limited, well established, motor areas, while signal amplitude and beta value changes appeared in a widespread fashion, contradicting the modularity theory. Entropy can predict increase in brain activation with task duration, while the other two cannot. When stimuli shifted from the rest state to the task state, entropy exhibited a similar increase as the other two did. Although entropy showed only a part of the phenomenon induced by task strength, it showed superiority by showing a decrease in brain activation that the other two did not show. Moreover, entropy was capable of identifying the physiologically important location.

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

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

Signals from posterior parietal area 5 to motor cortex during locomotion

Area 5 of the parietal cortex is part of the "dorsal stream" cortical pathway which processes visual information for action. The signals that area 5 ultimately conveys to motor cortex, the main area providing output to the spinal cord, are unknown. We analyzed area 5 neuronal activity during vision-independent locomotion on a flat surface and vision-dependent locomotion on a horizontal ladder in cats focusing on corticocortical neurons (CCs) projecting to motor cortex from the upper and deeper cortical layers and compared it to that of neighboring unidentified neurons (noIDs). We found that upon transition from vision-independent to vision-dependent locomotion, the low discharge of CCs in layer V doubled and the proportion of cells with 2 bursts per stride tended to increase. In layer V, the group of 2-bursters developed 2 activity peaks that coincided with peaks of gaze shifts along the surface away from the animal, described previously. One-bursters and either subpopulation in supragranular layers did not transmit any clear unified stride-related signal to the motor cortex. Most CC group activities did not mirror those of their noID counterparts. CCs with receptive fields on the shoulder, elbow, or wrist/paw discharged in opposite phases with the respective groups of pyramidal tract neurons of motor cortex, the cortico-spinal cells.

Feel Your Reach: An EEG-Based Framework to Continuously Detect Goal-Directed Movements and Error Processing to Gate Kinesthetic Feedback Informed Artificial Arm Control

Establishing the basic knowledge, methodology, and technology for a framework for the continuous decoding of hand/arm movement intention was the aim of the ERC-funded project "Feel Your Reach". In this work, we review the studies and methods we performed and implemented in the last 6 years, which build the basis for enabling severely paralyzed people to non-invasively control a robotic arm in real-time from electroencephalogram (EEG). In detail, we investigated goal-directed movement detection, decoding of executed and attempted movement trajectories, grasping correlates, error processing, and kinesthetic feedback. Although we have tested some of our approaches already with the target populations, we still need to transfer the "Feel Your Reach" framework to people with cervical spinal cord injury and evaluate the decoders' performance while participants attempt to perform upper-limb movements. While on the one hand, we made major progress towards this ambitious goal, we also critically discuss current limitations.

Modulation of Gamma Spectral Amplitude and Connectivity During Reaching Predicts Peak Velocity and Movement Duration

Modulation of gamma oscillations recorded from the human motor cortex and basal ganglia appears to play a key role in movement execution. However, there are still major questions to be answered about the specific role of cortical gamma activity in both the planning and execution of movement features such as the scaling of peak velocity and movement time. In this study, we characterized movement-related gamma oscillatory dynamics and its relationship with kinematic parameters based on 256-channels EEG recordings in 64 healthy subjects while performing fast and uncorrected reaching movements to targets located at three distances. In keeping with previous studies, we found that movement-related gamma synchronization occurred during movement execution. As a new finding, we showed that gamma synchronization occurred also before movement onset, with planning and execution phases involving different gamma peak frequencies and topographies. Importantly, the amplitude of gamma synchronization in both planning and execution increased with target distance and predicted peak velocity and movement time. Additional analysis of phase coherence revealed a gamma-coordinated long-range network involving occipital, frontal and central regions during movement execution that was positively related to kinematic features. This is the first evidence in humans supporting the notion that gamma synchronization amplitude and phase coherence pattern can reliably predict peak velocity amplitude and movement time. Therefore, these findings suggest that cortical gamma oscillations have a crucial role for the selection, implementation and control of the appropriate kinematic parameters of goal-directed reaching movements.

Mind over matter: Perceived phantom/prosthesis co-location contributes to prosthesis embodiment in lower limb amputees

Prosthesis embodiment - the cognitive integration of a prosthesis into an amputees' body representation - has been identified as important for prosthetic rehabilitation. However, the underlying cognitive mechanisms remain unclear. There is reason to assume that phantom limbs that are experienced as part of the bodily self (phantom self-consciousness) can affect prosthesis embodiment, but only if the phantom and the prosthesis can be brought into perceived co-location (phantom prosthesis tolerance, PPT). In the present study, phantom-prosthesis interactions were examined in lower limb amputees, and a PPT component was psychometrically extracted. Mediation analysis revealed an indirect-only effect, where the relationship between phantom self-consciousness and prosthesis embodiment was mediated by PPT, indicating that phantom limbs can transfer their immanent vividness to the prosthesis. Subsequent analyses suggested that this effect can compensate for negative consequences on prosthesis embodiment that arise from phantom limb awareness. These results shape theoretical considerations about the cognitive processes contributing to the bodily self.

Differential coding of goals and actions in ventral and dorsal corticostriatal circuits during goal-directed behavior

Goal-directed behavior requires identifying objects in the environment that can satisfy internal needs and executing actions to obtain those objects. The current study examines ventral and dorsal corticostriatal circuits that support complementary aspects of goal-directed behavior. We analyze activity from the amygdala, ventral striatum, orbitofrontal cortex, and lateral prefrontal cortex (LPFC) while monkeys perform a three-armed bandit task. Information about chosen stimuli and their value is primarily encoded in the amygdala, ventral striatum, and orbitofrontal cortex, while the spatial information is primarily encoded in the LPFC. Before the options are presented, information about the to-be-chosen stimulus is represented in the amygdala, ventral striatum, and orbitofrontal cortex; at the time of choice, the information is passed to the LPFC to direct a saccade. Thus, learned value information specifying behavioral goals is maintained throughout the ventral corticostriatal circuit, and it is routed through the dorsal circuit at the time actions are selected.

Reinforcement-learning in fronto-striatal circuits

We review the current state of knowledge on the computational and neural mechanisms of reinforcement-learning with a particular focus on fronto-striatal circuits. We divide the literature in this area into five broad research themes: the target of the learning-whether it be learning about the value of stimuli or about the value of actions; the nature and complexity of the algorithm used to drive the learning and inference process; how learned values get converted into choices and associated actions; the nature of state representations, and of other cognitive machinery that support the implementation of various reinforcement-learning operations. An emerging fifth area focuses on how the brain allocates or arbitrates control over different reinforcement-learning sub-systems or "experts". We will outline what is known about the role of the prefrontal cortex and striatum in implementing each of these functions. We then conclude by arguing that it will be necessary to build bridges from algorithmic level descriptions of computational reinforcement-learning to implementational level models to better understand how reinforcement-learning emerges from multiple distributed neural networks in the brain.

Direct and indirect cues can enable dual adaptation, but through different learning processes

Switching between motor tasks requires accurate adjustments for changes in dynamics (grasping a cup) or sensorimotor transformations (moving a computer mouse). Dual-adaptation studies have investigated how learning of context-dependent dynamics or transformations is enabled by sensory cues. However, certain cues, such as color, have shown mixed results. We propose that these mixed results may arise from two major classes of cues: "direct" cues, which are part of the dynamic state and "indirect" cues, which are not. We hypothesized that explicit strategies would primarily account for the adaptation of an indirect color cue but would be limited to simple tasks, whereas a direct visual separation cue would allow implicit adaptation regardless of task complexity. To test this idea, we investigated the relative contribution of implicit and explicit learning in relation to contextual cue type (colored or visually shifted workspace) and task complexity (1 or 8 targets) in a dual-adaptation task. We found that the visual workspace location cue enabled adaptation across conditions primarily through implicit adaptation. In contrast, we found that the color cue was largely ineffective for dual adaptation, except in a small subset of participants who appeared to use explicit strategies. Our study suggests that the previously inconclusive role of color cues in dual adaptation may be explained by differential contribution of explicit strategies across conditions.NEW & NOTEWORTHY We present evidence that learning of context-dependent dynamics proceeds via different processes depending on the type of sensory cue used to signal the context. Visual workspace location enabled learning different dynamics implicitly, presumably because it directly enters the dynamic state estimate. In contrast, a color cue was only successful where learners were apparently able to leverage explicit strategies to account for changed dynamics. This suggests a unification for the previously inconclusive role of color cues.

Comparative metabolic profiling of posterior parietal cortex, amygdala, and hippocampus in conditioned fear memory

Fear conditioning and retrieval are suitable models to investigate the biological basis of various mental disorders. Hippocampus and amygdala neurons consolidate conditioned stimulus (CS)-dependent fear memory. Posterior parietal cortex is considered important for the CS-dependent conditioning and retrieval of fear memory. Metabolomic screening among functionally related brain areas provides molecular signatures and biomarkers to improve the treatment of psychopathologies. Herein, we analyzed and compared changes of metabolites in the hippocampus, amygdala, and posterior parietal cortex under the fear retrieval condition. Metabolite profiles of posterior parietal cortex and amygdala were similarly changed after fear memory retrieval. While the retrieval of fear memory perturbed various metabolic pathways, most metabolic pathways that overlapped among the three brain regions had high ranks in the enrichment analysis of posterior parietal cortex. In posterior parietal cortex, the most perturbed pathways were pantothenate and CoA biosynthesis, purine metabolism, glutathione metabolism, and NAD+ dependent signaling. Metabolites of posterior parietal cortex including 4'-phosphopantetheine, xanthine, glutathione, ADP-ribose, ADP-ribose 2'-phosphate, and cyclic ADP-ribose were significantly regulated in these metabolic pathways. These results point to the importance of metabolites of posterior parietal cortex in conditioned fear memory retrieval and may provide potential biomarker candidates for traumatic memory-related mental disorders.

Sleep Leads to Brain-Wide Neural Changes Independent of Allocentric and Egocentric Spatial Training in Humans and Rats

Sleep is important for memory consolidation and systems consolidation in particular, which is thought to occur during sleep. While there has been a significant amount of research regarding the effect of sleep on behavior and certain mechanisms during sleep, evidence that sleep leads to consolidation across the system has been lacking until now. We investigated the role of sleep in the consolidation of spatial memory in both rats and humans using a watermaze task involving allocentric- and egocentric-based training. Analysis of immediate early gene expression in rodents, combined with functional magnetic resonance imaging in humans, elucidated similar behavioral and neural effects in both species. Sleep had a beneficial effect on behavior in rats and a marginally significant effect in humans. Interestingly, sleep led to changes across multiple brain regions at the time of retrieval in both species and in both training conditions. In rats, sleep led to increased gene expression in the hippocampus, striatum, and prefrontal cortex. In the humans, sleep led to an activity increase in brain regions belonging to the executive control network and a decrease in activity in regions belonging to the default mode network. Thus, we provide cross-species evidence for system-level memory consolidation occurring during sleep.

Distributed functions of prefrontal and parietal cortices during sequential categorical decisions

Comparing sequential stimuli is crucial for guiding complex behaviors. To understand mechanisms underlying sequential decisions, we compared neuronal responses in the prefrontal cortex (PFC), the lateral intraparietal (LIP), and medial intraparietal (MIP) areas in monkeys trained to decide whether sequentially presented stimuli were from matching (M) or nonmatching (NM) categories. We found that PFC leads M/NM decisions, whereas LIP and MIP appear more involved in stimulus evaluation and motor planning, respectively. Compared to LIP, PFC showed greater nonlinear integration of currently visible and remembered stimuli, which correlated with the monkeys' M/NM decisions. Furthermore, multi-module recurrent networks trained on the same task exhibited key features of PFC and LIP encoding, including nonlinear integration in the PFC-like module, which was causally involved in the networks' decisions. Network analysis found that nonlinear units have stronger and more widespread connections with input, output, and within-area units, indicating putative circuit-level mechanisms for sequential decisions.

Dedicated Representation of Others in the Macaque Frontal Cortex: From Action Monitoring and Prediction to Outcome Evaluation

Social neurophysiology has increasingly addressed how several aspects of self and other are distinctly represented in the brain. In social interactions, the self–other distinction is fundamental for discriminating one’s own actions, intentions, and outcomes from those that originate in the external world. In this paper, we review neurophysiological experiments using nonhuman primates that shed light on the importance of the self–other distinction, focusing mainly on the frontal cortex. We start by examining how the findings are impacted by the experimental paradigms that are used, such as the type of social partner or whether a passive or active interaction is required. Next, we describe the 2 sociocognitive systems: mirror and mentalizing. Finally, we discuss how the self–other distinction can occur in different domains to process different aspects of social information: the observation and prediction of others’ actions and the monitoring of others’ rewards.

Large Postural Sways Prevent Foot Tactile Information From Fading: Neurophysiological Evidence

Cutaneous foot receptors are important for balance control, and their activation during quiet standing depends on the speed and the amplitude of postural oscillations. We hypothesized that the transmission of cutaneous input to the cortex is reduced during prolonged small postural sways due to receptor adaptation during continued skin compression. Central mechanisms would trigger large sways to reactivate the receptors. We compared the amplitude of positive and negative post-stimulation peaks (P₅₀N₉₀) somatosensory cortical potentials evoked by the electrical stimulation of the foot sole during small and large sways in 16 young adults standing still with their eyes closed. We observed greater P₅₀N₉₀ amplitudes during large sways compared with small sways consistent with increased cutaneous transmission during large sways. Postural oscillations computed 200 ms before large sways had smaller amplitudes than those before small sways, providing sustained compression within a small foot sole area. Cortical source analyses revealed that during this interval, the activity of the somatosensory areas decreased, whereas the activity of cortical areas engaged in motor planning (supplementary motor area, dorsolateral prefrontal cortex) increased. We concluded that large sways during quiet standing represent self-generated functional behavior aiming at releasing skin compression to reactivate mechanoreceptors. Such balance motor commands create sensory reafference that help control postural sway.

Cortical connections of the functional domain for climbing or running in posterior parietal cortex of galagos

Previous studies in prosimian galagos (Otolemur garnetti) have demonstrated that posterior parietal cortex (PPC) is subdivided into several functionally distinct domains, each of which mediates a specific type of complex movements (e.g., reaching, grasping, hand-to-mouth) and has a different pattern of cortical connections. Here we identified a medially located domain in PPC where combined forelimb and hindlimb movements, as if climbing or running, were evoked by long-train intracortical microstimulation. We injected anatomical tracers in this climbing/running domain of PPC to reveal its cortical connections. Our results showed the PPC climbing domain had dense intrinsic connections within rostral PPC and reciprocal connections with forelimb and hindlimb region in primary motor cortex (M1) of the ipsilateral hemisphere. Fewer connections were with dorsal premotor cortex (PMd), supplementary motor (SMA), and cingulate motor (CMA) areas, as well as somatosensory cortex including areas 3a, 3b, and 1-2, secondary somatosensory (S2), parietal ventral (PV), and retroinsular (Ri) areas. The rostral portion of the climbing domain had more connections with primary somatosensory cortex than the caudal portion. Cortical projections were found in functionally matched domains in M1 and premotor cortex (PMC). Similar patterns of connections with fewer labeled neurons and terminals were seen in the contralateral hemisphere. These connection patterns are consistent with the proposed role of the climbing/running domain as part of a parietal-frontal network for combined use of the limbs in locomotion as in climbing and running. The cortical connections identify this action-specific domain in PPC as a more somatosensory driven domain.

Affective sounds entering the peripersonal space influence the whole-body action preparation

The peripersonal space (PPS), the space surrounding us, is found to have enhanced multisensory-motor representation in the brain. In this study, we investigate how approaching sounds stopping at different distances within the peripersonal space, and carrying emotional content (positive, negative, and neutral), modulate the preparation of action as performing a Step. Premotor reaction times were measured by means of anticipatory forces and muscular activations to capture action preparation, the kinematics of stepping was considered for defining action performance, and for each stimulus, the individual perceived level of arousal and valence was evaluated. In general, we found a prompter premotor reaction for closer sounds compared to the farther ones and the fastest reactions detected for the neutral sound at each distance. We interpreted this time facilitation for neutral sound due to the large frequency spectrum of the stimuli and the absence of affective component and semantical content to decode. Interestingly, while at the close distance, none difference was found between positive and negative emotional stimuli, at the far distance faster reactions were present for negative compared to the positive sounds indicating that when arousal is less enhanced individuals are able to differentiate the emotional content of a sound. The kinematics observed after action initiation sustained the anticipatory results by showing that larger steps were performed when reacting to close compared to far sounds, being perceived as more arousing, and this happened particularly for neutral and negative sounds. Altogether, the results showed that action preparation is influenced by the vicinity and by the valence carried by looming auditory stimuli. For discriminating the stimuli valence, a certain distance, still within the PPS, is necessary; when instead stimuli are too close to the body valence discrimination is not performed.