Parietal Cortex Area Research Articles

Cortical activity and gait parameter characteristics in people with multiple sclerosis during unobstructed gait and obstacle avoidance

BackgroundPeople with Multiple Sclerosis (PwMS) present higher cortical activity during walking. However, the cortical activity during gait while avoiding an obstacle is still not clear. ObjectiveTo investigate cortical activity and gait spatial-temporal parameters in PwMS during two different gait tasks (i.e., unobstructed and obstacle avoidance). MethodFifteen PwMS and 15 healthy controls (CG) were recruited. Participants performed ten trials in each gait condition, wearing a 64-electrode cap electroencephalogram (EEG) at 1024 Hz. Kinematic data were obtained through 10 Vicon® cameras at 200 Hz. EEG was analyzed through four cortical areas (frontal, motor, parietal, and occipital cortex areas) and five frequency bands (delta, theta, alpha, beta, and gamma) obtained through the power spectral density. In addition, spatial-temporal gait parameters (e.g., step length and velocity) were measured. Two-way ANOVA (group x gait condition) and MANOVA (group x gait condition) were used to compare gait and EEG parameters, respectively. One-way ANOVA was used to compare groups in the crossing phase of the obstacle avoidance condition. ResultsPwMS presented lower step length and velocity, and higher cortical activity in frontal (beta and gamma) and parietal (gamma) cortical areas in both gait conditions compared to CG. Moreover, PwMS presented increased cortical activation (frontal and parietal) and decreased step length and velocity in obstacle avoidance compared with unobstructed gait. In addition, PwMS required more cortical resources (frontal and parietal) than CG to accomplish both gait conditions. During the obstacle avoidance task, it was further observed that PwMS positioned their feet closer to the obstacle, before and after the task, compared to CG. ConclusionPwMS demand higher cortical resources to accomplish gait tasks, mainly when it is necessary to negotiate an obstacle in the pathway. This higher cortical activity may be a compensatory mechanism to deal with damage in subcortical structures caused by multiple sclerosis.

Region-Specific Effects of 10-Hz Transcranial Alternate Current Stimulation Over the Left Posterior Parietal Cortex and Primary Somatosensory Area on Tactile Two-Point Discrimination Threshold.

Changes in α-band cortical oscillatory activity (8–13 Hz) affect perception; however, how these changes in the left posterior parietal cortex (PPC) and primary somatosensory cortex (S1), which play different roles in determining the two-point discrimination (TPD) threshold, affect TPD threshold remains unelucidated. Therefore, to determine TPD threshold, we aimed to investigate the function of the left PPC and S1 by applying α-band transcranial alternating current stimulation (α-tACS; 10 Hz). TPD threshold was examined at the pad of the right index finger, contralateral to the stimulation site, in 17 healthy adults using a custom-made, computer-controlled, two-point tactile stimulation device, with random application of either active or sham α-tACS over the left PPC (Experiment 1) and left S1 (Experiment 2). Then, 50% TPD threshold was obtained in the active and sham conditions via logistic regression analysis. Afterward, we compared the difference between the active and sham conditions at 50% TPD threshold in each region and found that α-tACS reduced TPD threshold when applied over the left PPC (P = 0.010); however, its effect was insignificant when applied over the left S1 (P = 0.74). Moreover, a comparison of the change in 50% TPD threshold among the regions revealed that α-tACS applied over the left PPC significantly reduced TPD threshold compared with that applied over the left S1 (P = 0.003). Although we did not reveal the actual changes in cortical activity induced by α-tACS, this is the first empirical evidence that α-tACS applied over the left PPC and left S1 exerts region-specific effects on determining TPD threshold assessed in the contralateral index finger pad by stimulation.

Distinct saccade planning and endogenous visuospatial attention maps in parietal cortex: A basis for functional differences in sensory and motor attention

Parietal cortex activity contributes to higher-level cognitive processes, including endogenous visual attention and saccade planning. While visual attention is the process of selecting pertinent information from the environment, saccade planning may involve motor attention in the planning of a specific movement, including the process of selecting the correct path. We isolated areas in parietal cortex involved in saccade planning, while controlling visual attention, to understand the relationship between the two processes. Using our novel stimulus, participants performed a delayed saccade task and an endogenous covert visuospatial attention task with peripheral targets in identical locations. We compared multiple target locations across the two domains at the level of the individual to better understand variability in the relationship between these two maps. The anterior–posterior organization of saccade planning and visual attention maps varied among, but not within, participants, and 14–29% of the maps for each task overlapped one another across hemispheres. Interestingly, within the region of co-activation, over 67% of the voxels responded to the same location for both tasks. These cortical areas of overlap may represent regions of the brain specifically involved in the transfer of information from vision to action along the visuomotor pathway. These results further establish the relationship between maps associated with saccade planning and visual attention at the individual level, indicating the lack of a single saliency map in parietal cortex.

Adaptive Hausdorff Estimation of Movement-Related Eeg Patterns for Brain-Computer Interfaces

The study was aimed at developing a new automatic search technique for specific invariant patterns associated with the execution of voluntary motor activity (Readiness potentials, RP) reflected in multidimensional electroencephalogram (EEG) signals. The Hausdorff metric was used as a criterion function for searching specific movement-related EEG patterns in brain activity. To increase the metric sensitivity, an adaptive low-pass filter was synthesized with the multivariate singular spectrum analysis (SSA). It has been experimentally demonstrated that significant temporal characteristics of the brain potentials preceding movement execution in the frontal, central and parietal areas of the cerebral cortex, on average, were 240±90 ms. It is shown that the synthesized adaptive filter has provided a reliable automatic search for induced pre-movement EEG patterns and the correct determination of their time boundaries (accuracy up to 96%). The developed method expands the existing tools to improve the functionality and reliability of various Brain-computer interfaces including those based on randomly generated, user-induced patterns of brain activity associated with voluntary motor activity.

Multimodal 3D atlas of the macaque monkey motor and premotor cortex

In the present study we reevaluated the parcellation scheme of the macaque frontal agranular cortex by implementing quantitative cytoarchitectonic and multireceptor analyses, with the purpose to integrate and reconcile the discrepancies between previously published maps of this region.We applied an observer-independent and statistically testable approach to determine the position of cytoarchitectonic borders. Analysis of the regional and laminar distribution patterns of 13 different transmitter receptors confirmed the position of cytoarchitectonically identified borders. Receptor densities were extracted from each area and visualized as its “receptor fingerprint”. Hierarchical and principal components analyses were conducted to detect clusters of areas according to the degree of (dis)similarity of their fingerprints. Finally, functional connectivity pattern of each identified area was analyzed with areas of prefrontal, cingulate, somatosensory and lateral parietal cortex and the results were depicted as “connectivity fingerprints” and seed-to-vertex connectivity maps.We identified 16 cyto- and receptor architectonically distinct areas, including novel subdivisions of the primary motor area 4 (i.e. 4a, 4p, 4m) and of premotor areas F4 (i.e. F4s, F4d, F4v), F5 (i.e. F5s, F5d, F5v) and F7 (i.e. F7d, F7i, F7s). Multivariate analyses of receptor fingerprints revealed three clusters, which first segregated the subdivisions of area 4 with F4d and F4s from the remaining premotor areas, then separated ventrolateral from dorsolateral and medial premotor areas. The functional connectivity analysis revealed that medial and dorsolateral premotor and motor areas show stronger functional connectivity with areas involved in visual processing, whereas 4p and ventrolateral premotor areas presented a stronger functional connectivity with areas involved in somatomotor responses.For the first time, we provide a 3D atlas integrating cyto- and multi-receptor architectonic features of the macaque motor and premotor cortex. This atlas constitutes a valuable resource for the analysis of functional experiments carried out with non-human primates, for modeling approaches with realistic synaptic dynamics, as well as to provide insights into how brain functions have developed by changes in the underlying microstructure and encoding strategies during evolution.

The Role of Frontoparietal Cortex across the Functional Stages of Visual Search

Areas in frontoparietal cortex have been shown to be active in a range of cognitive tasks and have been proposed to play a key role in goal-driven activities (Dosenbach, N. U. F., Fair, D. A., Miezin, F. M., Cohen, A. L., Wenger, K. K., Dosenbach, R. A. T., et al. Distinct brain networks for adaptive and stable task control in humans. Proceedings of the National Academy of Sciences, U.S.A., 104, 11073-11078, 2007; Duncan, J. The multiple-demand (MD) system of the primate brain: Mental programs for intelligent behavior. Trends in Cognitive Sciences, 14, 172-179, 2010). Here, we examine the role this frontoparietal system plays in visual search. Visual search, like many complex tasks, consists of a sequence of operations: target selection, stimulus-response (SR) mapping, and response execution. We independently manipulated the difficulty of target selection and SR mapping in a novel visual search task that involved identical stimulus displays. Enhanced activity was observed in areas of frontal and parietal cortex during both difficult target selection and SR mapping. In addition, anterior insula and ACC showed preferential representation of SR-stage information, whereas the medial frontal gyrus, precuneus, and inferior parietal sulcus showed preferential representation of target selection-stage information. A connectivity analysis revealed dissociable neural circuits underlying visual search. We hypothesize that these circuits regulate distinct mental operations associated with the allocation of spatial attention, stimulus decisions, shifts of task set from selection to SR mapping, and SR mapping. Taken together, the results show frontoparietal involvement in all stages of visual search and a specialization with respect to cognitive operations.

Patterns of Functional Connectivity in the Brain in Temporal and Frontal Epilepsy

Objectives. To identify the pattern of functional connectivity (FC) between areas and networks in the brain in patients with frontal and temporal foci of epileptic activity. Materials and methods. A total of 43 patients aged 18–50 years with focal epilepsy – 32 with temporal epilepsy (TE) and 11 with frontal epilepsy (FE) – were studied. The control group consisted of 32 healthy subjects. The main method used in the study was brain MRI scans run using the epilepsy protocol and additionally including high-resolution structural images of the brain, along with resting-state fMRI. Results and conclusions. The most marked fMRI feature in patients with TE as compared with healthy subjects was a decrease in the FC of the insular cortex and the temporal opercula (the part of the temporal gyrus of each hemisphere overhanging the insula). In left-sided FE, the decrease on the left was significant. Increased FC in the dorsal part of the attention network on the left with the temporal and parietal areas of the cerebral cortex was specific for right-sided TE. TE also produced a decrease in FC between the anterior part of the cingulate gyrus and the basal ganglia. All significant results were linked with increases in FC in patients with FE as compared with healthy subjects, maximally in areas of the temporal cortex. Thus, the localization and lateralization of the focus of epileptic activity determine the pattern of FC in these areas and neural networks of the brain in patients with focal epilepsy.

Dissociating Arithmetic Operations in the Parietal Cortex Using 1 Hz Repetitive Transcranial Magnetic Stimulation: The Importance of Strategy Use.

The triple-code model (TCM) of number processing suggests the involvement of distinct parietal cortex areas in arithmetic operations: the bilateral horizontal segment of the intraparietal sulcus (hIPS) for arithmetic operations that require the manipulation of numerical quantities (e.g., subtraction) and the left angular gyrus (AG) for arithmetic operations that require the retrieval of answers from long-term memory (e.g., multiplication). Although neuropsychological, neuroimaging, and brain stimulation studies suggest the dissociation of these operations into distinct parietal cortex areas, the role of strategy (online calculation vs. retrieval) is not yet fully established. In the present study, we further explored the causal involvement of the left AG for multiplication and left hIPS for subtraction using a neuronavigated repetitive transcranial magnetic stimulation (rTMS) paradigm. Stimulation sites were determined based on an fMRI experiment using the same tasks. To account for the effect of strategy, participants were asked whether they used retrieval or calculation for each individual problem. We predicted that the stimulation of the left AG would selectively disrupt the retrieval of the solution to multiplication problems. On the other hand, stimulation of the left hIPS should selectively disrupt subtraction. Our results revealed that left AG stimulation was detrimental to the retrieval and online calculation of solutions for multiplication problems, as well as, the retrieval (but not online calculation) of the solutions to subtraction problems. In contrast, left hIPS stimulation had no detrimental effect on both operations regardless of strategy.

Spinach in the teeth: How ego- and allocentric perspectives modulate neural correlates of embarrassment in the face of others' public mishaps

Humans experience vicarious embarrassment when they observe other's mishaps in public settings, even when the protagonist is not embarrassed at all. Though neural correlates of vicarious embarrassment have been studied before, it is yet poorly understood how they are influenced by egocentric or allocentric processes of perspective-taking. In the present study we examined the effects of deliberate allocentric and egocentric perspectives during the evaluation of others' public mishaps that pose a threat to the protagonist's reputation. Forty-three participants were shown sketches depicting a protagonist's mishaps and were asked to rate either their own vicarious embarrassment as observers (egocentric perspective) or the protagonist's embarrassment (allocentric perspective). Using functional magnetic resonance imaging, we found that observing others' mishaps engaged the anterior insula, anterior cingulate cortex and medial prefrontal cortex, irrespective of the adopted mental perspective. Further, as part of the mentalizing network, the right middle temporal gyrus and right temporo-parietal junction were exclusively engaged when participants adopted an allocentric perspective while observing others' mishaps. Activation within bilateral areas of the inferior parietal cortex extending to the somatosensory cortex varied as a function of the protagonist's awareness of the blunder and the adopted perspective. In this study, we for the first time dissociate regions within the mentalizing network that contribute to a rather spontaneous versus a rather deliberate and motivated act of understanding other's mental states in the context of vicarious embarrassment.

Decoding and encoding models reveal the role of mental simulation in the brain representation of meaning.

How the brain representation of conceptual knowledge varies as a function of processing goals, strategies and task-factors remains a key unresolved question in cognitive neuroscience. In the present functional magnetic resonance imaging study, participants were presented with visual words during functional magnetic resonance imaging (fMRI). During shallow processing, participants had to read the items. During deep processing, they had to mentally simulate the features associated with the words. Multivariate classification, informational connectivity and encoding models were used to reveal how the depth of processing determines the brain representation of word meaning. Decoding accuracy in putative substrates of the semantic network was enhanced when the depth processing was high, and the brain representations were more generalizable in semantic space relative to shallow processing contexts. This pattern was observed even in association areas in inferior frontal and parietal cortex. Deep information processing during mental simulation also increased the informational connectivity within key substrates of the semantic network. To further examine the properties of the words encoded in brain activity, we compared computer vision models—associated with the image referents of the words—and word embedding. Computer vision models explained more variance of the brain responses across multiple areas of the semantic network. These results indicate that the brain representation of word meaning is highly malleable by the depth of processing imposed by the task, relies on access to visual representations and is highly distributed, including prefrontal areas previously implicated in semantic control.

Neural Correlates of Non-Specific Skin Conductance Responses During Resting State fMRI

Skin conductance responses (SCRs) reliably occur in the absence of external stimulation. However, the neural correlates of these non-specific SCRs have been less explored than brain activity associated with stimulus-elicited SCRs. This study modeled spontaneous skin conductance responses observed during an unstructured resting state fMRI scan in 58 adolescents. A Finite Impulse Response (FIR) fMRI model was used to detect any type of hemodynamic response shape time-locked to non-specific SCRs; the shape of these responses was then carefully characterized. The strongest evidence for signal change was found in several sub-regions of sensorimotor cortex. There also was evidence for engagement of discrete areas within the lateral surfaces of the parietal lobe, cingulate cortex, fronto-insular operculum, and both visual and auditory primary processing areas. The hemodynamic profile measured by FIR modeling clearly resembled an event-related response. However, it was a complex response, best explained by two quickly successive, but opposing neuronal impulses across all brain regions - a brief positive response that begins several seconds prior to the SCR with a much longer negative neuronal impulse beginning shortly after the SCR onset. Post hoc exploratory analyses linked these two hemodynamic response phases to different emotion-related individual differences. In conclusion, this study shows the neural correlates of non-specific SCRs are a widespread, cortical network of brain regions engaged in a complex, seemingly biphasic fashion. This bimodal response profile should be considered in replication studies that attempt to directly link brain activity to possible homeostatic mechanisms or seek evidence for alternative mechanisms.

Action representation in the mouse parieto-frontal network

The posterior parietal cortex (PPC) and frontal motor areas comprise a cortical network supporting goal-directed behaviour, with functions including sensorimotor transformations and decision making. In primates, this network links performed and observed actions via mirror neurons, which fire both when individuals perform an action and when they observe the same action performed by a conspecific. Mirror neurons are believed to be important for social learning, but it is not known whether mirror-like neurons occur in similar networks in other social species, such as rodents, or if they can be measured in such models using paradigms where observers passively view a demonstrator. Therefore, we imaged Ca2+ responses in PPC and secondary motor cortex (M2) while mice performed and observed pellet-reaching and wheel-running tasks, and found that cell populations in both areas robustly encoded several naturalistic behaviours. However, neural responses to the same set of observed actions were absent, although we verified that observer mice were attentive to performers and that PPC neurons responded reliably to visual cues. Statistical modelling also indicated that executed actions outperformed observed actions in predicting neural responses. These results raise the possibility that sensorimotor action recognition in rodents could take place outside of the parieto-frontal circuit, and underscore that detecting socially-driven neural coding depends critically on the species and behavioural paradigm used.

Temporal analysis of histopathology and cytokine expression in the rat cerebral cortex after insulin‐induced hypoglycemia

Hypoglycemic coma causes neuronal death in the cerebral neocortex; however, its unclear pathogenesis prevents the establishment of preventive measures. Inflammation plays a pivotal role in neuronal damage in the hypoglycemic state; however, the dynamics of glial cell activation or cytokine expression remain unknown. Here, we aimed to elucidate the spatiotemporal morphological changes of microglia and time-course cytokine expression profiles in the rat cerebral cortex after hypoglycemic coma. We performed histopathological and immunohistochemical (Iba1, neuronal nuclei, glial fibrillary acidic protein) analyses in the cingulate cortex and four areas of the neocortex: hindlimb area (HL), parietal cortex area 1 (Par1), parietal cortex area 2 (Par2), and perirhinal cortex (PRh). We measured tumor necrosis factor alpha (TNFα) and interleukin-6 messenger RNA (mRNA) expression by real-time reverse transcriptase-polymerase chain reaction. Necrotic neurons appeared in the neocortex as early as 3 h after hypoglycemic coma, while they were absent in the cingulate cortex. Neuronal nuclei-immunopositive neurons in the HL, Par2, and PRh were significantly less abundant than in the control at day 1. In Iba1 immunostaining, large rod-shaped cells were detected at 3-6 h after hypoglycemia, and commonly observed in the HL, Par2, and PRh. After 6 h, rod-shaped cells were rarely observed; instead, there was a prominent infiltration of hypertrophic and ameboid-shaped cells until day 7. The mRNA expression of TNFα was significantly higher than the control at 3-6 h after hypoglycemia in the neocortex, while it was significantly higher only at 3 h in the cingulate cortex. Our results indicate that early and transient appearance of rod-shaped microglia and persisting high TNFα expression levels characterize inflammatory responses to hypoglycemic neuronal damage in the cerebral neocortex, which might contribute to neuronal necrosis in response to transient hypoglycemic coma.

Thalamic afferents emphasize the different functions of macaque precuneate areas

We studied the thalamic afferents to cortical areas in the precuneus using injections of retrograde fluorescent neuronal tracers in four male macaques (Macaca fascicularis). Six injections were within the limits of cytoarchitectural area PGm, one in area 31 and one in area PEci. Precuneate areas shared strong input from the posterior thalamus (lateral posterior nucleus and pulvinar complex) and moderate input from the medial, lateral, and intralaminar thalamic regions. Area PGm received strong connections from the subdivisions of the pulvinar linked to association and visual function (the medial and lateral nuclei), whereas areas 31 and PEci received afferents from the oral division of the pulvinar. All three cytoarchitectural areas also received input from subdivisions of the lateral thalamus linked to motor function (ventral lateral and ventral anterior nuclei), with area PEci receiving additional input from a subdivision linked to somatosensory function (ventral posterior lateral nucleus). Finally, only PGm received substantial limbic association afferents, mainly via the lateral dorsal nucleus. These results indicate that area PGm integrates information from visual association, motor and limbic regions of the thalamus, in line with a hypothesized role in spatial cognition, including navigation. By comparison, dorsal precuneate areas (31 and PEci) are more involved in sensorimotor functions, being akin to adjacent areas of the dorsal parietal cortex.

Reconstruction of hand, elbow and shoulder actual and imagined trajectories in 3D space using EEG slow cortical potentials

Objective. The ability to decode kinematics of imagined movement from neural activity is essential for the development of prosthetic devices that can aid motor-disabled persons. To date, non-invasive recording methods, including electroencephalogram (EEG) were used to decode actual and imagined hand trajectory to control neuromotor prostheses, commonly by applying multi-dimensional linear regression (mLR) models to adjust the two temporal signals—neural signal and limb kinematics. It is still debated, however, whether the EEG signal, in general, and slow cortical potentials (SCPs), in specific, hold motor neural correlates. Moreover, it has not yet been tested whether the trajectory of proximal arm joints, i.e. shoulder, can also be reconstructed and if decoding performance is dependent on movement speed and/or position variance. Approach. We predicted hand, elbow and shoulder trajectories in 3D space in time series of both movement types (actual and imagined) of seven subjects using an mLR model, commonly applied for motion trajectory prediction (MTP) and used source localization to detect and compare between brain areas activated during actual and imagined movements for each arm joint. Main results. For all arm joints and movement types, SCPs contributed the most to trajectory reconstruction, and decoding accuracy peaked using neural signals preceding kinematics by 120–210 ms. The average (across subjects) Pearson’s correlation coefficient between predicted and actual trajectories ranged 0.24–0.49, 0.41–0.48 and 0.18–0.40 for the hand, elbow and shoulder, respectively, and was significantly higher than chance level (p < 0.01) for all subjects. For the imagined movements, reconstruction accuracy ranged between 0.09–0.23, 0.20–0.27 and 0.11–0.18 for the hand, elbow and shoulder, respectively, and was significantly higher than chance level (p < 0.05) for all or some of the arm joints. The model performance was positively correlated with movement speed and negatively correlated with position variance. Source localization suggested that the neural circuits engaged in motor imagery are more diffuse and bilateral; motor imagery was, when compared to movement execution, more associated with recruiting premotor regions and a large area of the left parietal cortex. Significance. Our results demonstrate the feasibility of predicting 3D imagined trajectories of all arm joints from scalp EEG and imply the existence of movement related neural correlates in slow cortical potentials.

Neural Correlates of True and False Recognition Memory for Socially Relevant Information in Schizophrenia

Abstract Individuals with schizophrenia (SZ) demonstrate poor recognition memory, even when information is socially relevant. The neural alterations associated with responses to old information that is accurately recognized (true recognition) vs new information inaccurately identified as old (false recognition) are not known. Twenty SZ patients and 16 healthy controls performed a recognition paradigm during functional magnetic resonance imaging (fMRI) using 78 learned target and 78 new distractor words (all socially relevant trait adjectives). Participants were asked to indicate whether they had seen the word before or not. Words were classified according to the subjects’ responses, as hits (true recognition), false alarms (false recognition), correct rejections, or misses and compared for blood-oxygen-level-dependent (BOLD) activation. During hits, patients with SZ and controls showed similar BOLD activation in expected areas of lateral prefrontal cortex, parietal cortex, and anterior cingulate cortex. During false alarms, controls activated many of the same regions as were activated during hits. In contrast, patients had reduced activation in lateral prefrontal cortex (Brodmann Area, BA, 9, 46), anterior cingulate/paracingulate (BA 24/32, 6), and posterior cingulate cortex (BA 23/31). These results indicate that, compared to controls, patients with SZ exhibit a lack of correspondence between behavior (ie, falsely identifying new items as old) and neural activation patterns (ie, overlap in activation of regions associated with true and false recognition). These findings shed light on the neural mechanisms associated with false recognition memory in SZ.

Time-Frequency Linearization of Reactive Cortical Responses for the Early Detection of Balance Losses

Aiming at finding a fast and accurate preimpact fall detection (PIFD) strategy, this paper proposes a novel methodology that precociously discriminates the occurrence of unexpected loss of balance from the steady walking, by analyzing the subject’s cortical signal modifications (at the scalp level) in the time-frequency domain. In this study, the subjects were asked to walk at their preferred speed on the treadmill platform programmed to provide unexpected bilateral slippages. The proposed PIFD method exploits synchronously recorded electromyographic (EMG: 2 channels from the same lower limb muscle bundle, bilaterally) and electro-encephalographic (EEG: 13 channels from motor, sensory-motor and parietal cortex areas) signals. To validate the method offline, also, the lower limb kinematics has been reconstructed via a motion capture system (23 reflective markers and 8 fixed cameras). During the PIFD system functioning, the EMG signals from the lateral gastrocnemii are first translated in a binary waveform and then used to trigger the EEG analysis. Once enabled via EMG (every gait cycle), the EEG computation branch extracts and linearizes the rate of variation in the EEG power spectrum density (PSD) for five bands of interests: θ (4–7 Hz), α (8–12 Hz), β I, β II, β III rhythms (13–15 Hz, 16–20 Hz, and 21–28 Hz). The slope of the linearized trend identifies, in this context, the cortical responsiveness parameter. Experimental results from six subjects revealed that the proposed system can distinguish the loss of balance with an overall accuracy of ~96% (average value between sensitivity and specificity). The discrimination process requests, on average, 370.6 ms. This value could be considered suitable for the implementation of countermeasures aimed at restoring the balance of the subject.

The role of vestibular function on the representation of space and its impairment after central and peripheral lesions

Our perception of space is based on the integration of signals from vestibular, visual, and somatosensory systems. These sensory modalities allow awareness of the displacements and positions of our body and body parts, as well as the locations of objects in extra-personal space. Brain lesions can produce severe deficits in the representation of personal or extra-personal space, as demonstrated by the syndrome of unilateral (left) spatial neglect after (right) hemisphere stroke. Many aspects of the neglect syndrome have been ascribed to pathological biases in the internal representation of space, some of which can also be observed in patients with dysfunction of the vestibular pathways, either in the peripheral or central nervous system. The recent studies showed for example, neglect patients like vestibular patients exhibit an ipsilesional (e.g. rightward) deviation of their subjective body midline when pointing straight-ahead, as well as ipsilesional biases in posture and abnormal perception of verticality. Therefore, it has been hypothesized that some impairment in the integration of vestibular signals at the brain level might contribute to impaired spatial cognition and neglect after focal hemispheric damage. A critical role for the vestibular system in neglect would be consistent with its central projections on multisensory integration areas in parietal and frontal cortex which are thought to be involved in the representation of space across egocentric and allocentric spatial frames of reference, and which are typically damaged in neglect patients.

The Computational Activity of Younger Students: Neuropsychological Approach

The article is devoted to the research of computational activity of junior pupils taking into account their neuropsychological peculiarities. The place of computational activity in the system of higher mental functions is determined. It is shown that the necessary prerequisite for the development of higher mental functions is the aging of various brain structures. The following basic areas of the brain that are involved in the calculations are defined: occipital, parietal and frontal areas of the cerebral cortex. It has been established that various compositions of these zones are used to perform computations, which in turn influences the choice of methods of reasoning. It has been experimentally proven that in the process of computational activity, young learners apply different methods of computing to the same tasks.

Assessing the similarity of cortical object and scene representations through cross-validated voxel encoding models

Object and scene perception are instantiated in overlapping networks of cortical regions, including three scene-selective areas in parahippocampal, occipital, and medial parietal cortex (PPA, OPA, and MPA), and a lateral occipital cortical area (LOC) selective for intact objects. The exact contributions of these regions to object and scene perception remain unknown. Here, we leverage BOLD5000 (Chang et. al, 2018), a public fMRI dataset containing responses to ~5000 images in ImageNet, COCO, and Scenes databases, to better understand the roles of these regions in visual perception. These databases vary in the degree to which images focus on single objects, a few objects, or whole scenes, respectively. We build voxel encoding models based on features from a deep convolutional neural network (DCNN) and assess the generalization of our encoding models trained and tested on all combinations of ImageNet, COCO, and Scenes databases. As predicted, we find good generalization between models trained and tested on ImageNet and COCO and poor generalization between ImageNet/COCO trained models and Scenes for most DCNN layer/ROI encoding models. Surprisingly, we find generalization from ImageNet/COCO to Scenes only in early visual cortex with encoding models of intermediate DCNN layers. Additionally, LOC and PPA exhibit similarly good generalization between ImageNet and COCO and poor generalization to Scenes. Excluding MPA responses to Scenes, all scene-selective areas generalize well to held-out data in the trained image database, but PPA exhibits the most robust generalization out-of-database between ImageNet and COCO, reflecting a more general perceptual role. Our work reflects a novel application of encoding models in neuroscience in which distinct stimulus sets are used for training and testing in order to test the similarity of representations underlying these stimuli. We plan to further test the effect of pretraining the DCNN on Places365 rather than ImageNet, and to look at image-level predictors of generalization.