Distinct spatio-temporal profiles of beta-oscillations within visual and sensorimotor areas during action recognition as revealed by MEG

Using virtual reality to assess gesture performance deficits in schizophrenia patients

Introduction

Gesture performance deficits are prevalent in schizophrenia patients and are strongly associated with poor social communication skills and community functioning, affecting their overall quality of life. Currently, video-recording technology is widely used in clinical settings to assess gesture production deficits in schizophrenia patients. Nevertheless, the subjective evaluation of video-recordings can encumber task assessment. The present study will aim to use virtual reality to examine its potential use as an alternative tool to objectively measure gesture performance accuracy in schizophrenia patients and healthy controls.

Methods

Gesture performance in the virtual reality setting will be based on the well-established Test of Upper Limb Apraxia. Participants will be immersed in a virtual environment where they will experience themselves being embodied in a collocated virtual body seen from a first-person perspective. Motion trackers will be placed on participants' hands and elbows to track upper body movements in real-time, and to record gesture movement for later analysis. Participants will see a virtual agent sitting across from them, with a virtual table in between. The agent will perform various types of gestures and the participants' task will be to imitate those gestures as accurately as possible. Measurements from the tracking devices will be stored and analyzed to address gesture performance accuracy across groups.

Discussion

This study aims to provide objective measurements of gesture performance accuracy in schizophrenia patients. If successful, the results will provide new knowledge to the gesture literature and offer the potential for novel therapeutic interventions using virtual reality technologies. Such interventions can improve gesturing and thus advance social communication skills in schizophrenia patients.

Aberrant neural processing of event boundaries in persons with Parkinson's disease

The perception of everyday events implies the segmentation into discrete sub-events (i.e. event segmentation). This process is relevant for the prediction of upcoming events and for the recall of recent activities. It is thought to involve dopaminergic networks which are strongly compromised in Parkinson's disease (PD). Indeed, deficits of event segmentation have been previously shown in PD, but underlying neuronal mechanisms remain unknown. We therefore investigated 22 persons with PD and 22 age-matched healthy controls, who performed an event segmentation task with simultaneous electroencephalography (EEG). Both groups had to indicate by button press the beginning of sub-events within three movies showing persons performing everyday activities. The segmentation performance of persons with PD deviated significantly from that of controls. Neurophysiologically, persons with PD expressed reduced theta (4-7 Hz) activity around identified event boundaries compared to healthy controls. Together, these results point to disturbed event processing in PD. According to functions attributed to EEG activities in particular frequency ranges, the PD-related theta reduction could reflect impaired matching of perceptual input with stored event representations and decreased updating processes of event information in working memory and, thus, event boundary identification.

Beta band oscillations in the motor thalamus are modulated by visuomotor coordination in essential tremor patients

Introduction

Beta oscillations in sensorimotor structures contribute to the planning, sequencing, and stopping of movements, functions that are typically associated with the role of the basal ganglia. The presence of beta oscillations (13-30 Hz) in the cerebellar zone of the thalamus (the ventral intermediate nucleus - Vim) indicates that this rhythm may also be involved in cerebellar functions such as motor learning and visuomotor adaptation.

Methods

To investigate the possible role of Vim beta oscillations in visuomotor coordination, we recorded local field potential (LFP) and multiunit activity from the Vim of essential tremor (ET) patients during neurosurgery for the implantation of deep brain stimulation (DBS) electrodes. Using a computer, patients performed a visuomotor adaptation task that required coordinating center-out movements with incongruent visual feedback imposed by inversion of the computer display.

Results

The results show that, in ET, Vim beta oscillations of the LFP were lower during the incongruent center-out task than during the congruent orientation. Vim firing rates increased significantly during periods of low beta power, particularly on approach to the peripheral target. In contrast, beta power in the subthalamic nucleus of Parkinson's disease (PD) patients did not differ significantly between the incongruent and the congruent orientation of the center-out task.

Discussion

The findings support the hypothesis that beta oscillations of the Vim are modulated by novel visuomotor tasks. The inverse relationship between the power of Vim-LFP beta oscillations and Vim firing rates suggest that the suppression of beta oscillations may facilitate information throughput to the thalamocortical circuit by modulation of Vim firing rates.

Using dynamic point light display stimuli to assess gesture deficits in schizophrenia

Background

Gesture deficits are ubiquitous in schizophrenia patients contributing to poor social communication and functional outcome. Given the dynamic nature of social communications, the current study aimed to explore the underlying socio-cognitive processes associated with point-light-displays (PLDs) of communicative gestures in the absence of any other confounding visual characteristics, and compare them to other well-established stimuli of gestures such as pictures by examining their association with symptom severity and motor-cognitive modalities.

Methods

We included 39-stable schizophrenia outpatients and 27-age-gender matched controls and assessed gesture processing using two tasks. The first task used static stimuli of pictures of a person performing a gesture. The limbs executing the gesture were missing and participants' task was to choose the correct gesture from three-options provided. The second task included videos of dynamic PLDs interacting with each other. One PLD performed communicative gestures, while the other PLD imitated/followed these performed gestures. Participants had to indicate, which of the two PLDs was imitating/following the other. Additionally, we evaluated symptom severity, as well as, motor and cognitive parameters.

Results

Patients underperformed in both gesture tasks compared to controls. Task performance for static stimuli was associated with blunted affect, motor coordination and sequencing domains, while PLD performance was associated with expressive gestures and sensory integration processes.

Discussion

Gesture representations of static and dynamic stimuli are associated with distinct processes contributing to poor social communication in schizophrenia, requiring novel therapeutic interventions. Such stimuli can easily be applied remotely for screening socio-cognitive deficits in schizophrenia.

Human movements do not look the same in a tilted world: Gravitational constraints influence the perception of biological motion

We investigated whether gravitational constraints influence the interaction of visual, proprioceptive and vestibular cues for Biological Motion Perception (BMP). Participants were asked to distinguish between plausible and random point-light movements, while passively placed in either an upright or a tilted body orientation. Manipulating the body orientation with respect to gravity leads to different gravitational signals transmitted by the visual, proprioceptive, and vestibular systems. Participants were overall faster in distinguishing plausible point-light movements than random movements. Critically, response times for biologically plausible point-light movements - but not for random movements - were significantly prolonged in the tilted body orientation. Our results suggest that BMP depends not only on the spatial-temporal cues embedded in point-light movements but also rely on the congruency between current gravitational signals detected by the sensory systems and our previous knowledge of terrestrial gravity. STATEMENT OF RELEVANCE: As humankind is preparing for a new space age, understanding how gravity influences behaviour and cognition has never been more pressing. All living organisms have evolved to survive in a terrestrial gravitational field. Although we cannot consciously feel gravity, it has an impact in our life: it affects how we move and interact with the external environment. The sensory signals from the vestibular system are continuously combined with visual and proprioceptive cues to help us in maintaining a stable representation of the world. Here we placed participants in a tilted body orientation and were able to determine that a conflict between prior gravitational knowledge and what was actively sensed about gravity affected human Biological Movement Perception. Humans suffer changes in perception under non-terrestrial gravity conditions that may potentially compromise performance during space exploration.

Brain Stimulation and Group Therapy to Improve Gesture and Social Skills in Schizophrenia-The Study Protocol of a Randomized, Sham-Controlled, Three-Arm, Double-Blind Trial

An important component of nonverbal communication is gesture performance, which is strongly impaired in 2/3 of patients with schizophrenia. Gesture deficits in schizophrenia are linked to poor social functioning and reduced quality of life. Therefore, interventions that can help alleviate these deficits in schizophrenia are crucial. Here, we describe an ongoing randomized, double-blind 3-arm, sham-controlled trial that combines two interventions to reduce gesture deficits in schizophrenia patients. The combined interventions are continuous theta burst stimulation (cTBS) and social cognitive remediation therapy (SCRT). We will randomize 72 patients with schizophrenia spectrum disorders in three different groups of 24 patients. The first group will receive real cTBS and real SCRT, the second group will receive sham cTBS and real SCRT, and finally the third group will receive sham SCRT. Here, the sham treatments are, as per definition, inactive interventions that mimic as closely as possible the real treatments (similar to placebo). In addition, 24 age- and gender-matched controls with no interventions will be added for comparison. Measures of nonverbal communication, social cognition, and multimodal brain imaging will be applied at baseline and after intervention. The main research aim of this project will be to test whether the combination of cTBS and SCRT improves gesture performance and social functioning in schizophrenia patients more than standalone cTBS, SCRT or sham psychotherapy. We hypothesize that the patient group receiving the combined interventions will be superior in improving gesture performance.

CLINICAL TRIAL REGISTRATION

[www.ClinicalTrials.gov], identifier [NCT04106427].

Spatiotemporal dynamics of responses to biological motion in the human brain

We sought to understand the spatiotemporal characteristics of biological motion perception. We presented observers with biological motion walkers that differed in terms of form coherence or kinematics (i.e., the presence or absence of natural acceleration). Participants were asked to discriminate the facing direction of the stimuli while their magnetoencephalographic responses were concurrently imaged. We found that two univariate response components can be observed around ~200 msec and ~650 msec post-stimulus onset, each engaging lateral-occipital and parietal cortex prior to temporal and frontal cortex. Moreover, while univariate responses show biological motion form-specificity only after 300 msec, multivariate patterns specific to form can be well discriminated from those for local cues as early as 100 msec after stimulus onset. By finally examining the representational similarity of fMRI and MEG patterned responses, we show that early responses to biological motion are most likely sourced to occipital cortex while later responses likely originate from extrastriate body areas.

Cortical dynamics during preparation and execution of reactive balance responses with distinct postural demands

The contributions of the cerebral cortex to human balance control are clearly demonstrated by the profound impact of cortical lesions on the ability to maintain standing balance. The cerebral cortex is thought to regulate subcortical postural centers to maintain upright balance and posture under varying environmental conditions and task demands. However, the cortical mechanisms that support standing balance remain elusive. Here, we present an EEG-based analysis of cortical oscillatory dynamics during the preparation and execution of balance responses with distinct postural demands. In our experiment, participants responded to backward movements of the support surface either with one forward step or by keeping their feet in place. To challenge the postural control system, we applied participant-specific high accelerations of the support surface such that the postural demand was low for stepping responses and high for feet-in-place responses. We expected that postural demand modulated the power of intrinsic cortical oscillations. Independent component analysis and time-frequency domain statistics revealed stronger suppression of alpha (9-13 Hz) and low-gamma (31-34 Hz) rhythms in the supplementary motor area (SMA) when preparing for feet-in-place responses (i.e., high postural demand). Irrespective of the response condition, support-surface movements elicited broadband (3-17 Hz) power increase in the SMA and enhancement of the theta (3-7 Hz) rhythm in the anterior prefrontal cortex (PFC), anterior cingulate cortex (ACC), and bilateral sensorimotor cortices (M1/S1). Although the execution of reactive responses resulted in largely similar cortical dynamics, comparison between the bilateral M1/S1 showed that stepping responses corresponded with stronger suppression of the beta (13-17 Hz) rhythm in the M1/S1 contralateral to the support leg. Comparison between response conditions showed that feet-in-place responses corresponded with stronger enhancement of the theta (3-7 Hz) rhythm in the PFC. Our results provide novel insights into the cortical dynamics of SMA, PFC, and M1/S1 during the control of human balance.

Event-related desynchronization of mu and beta oscillations during the processing of novel tool names

According to the embodied cognition framework, the formation of conceptual representations integrates the type of experience during learning. In this electroencephalographic study, we applied a linguistic variant of a training paradigm, in which participants learned to associate novel names to novel tools while either manipulating or visually exploring them. The analysis focused on event-related desynchronization (ERD) of oscillations in the mu and beta frequency range, which reflects activation of sensorimotor brain areas. After three training sessions, processing names of manipulated tools elicited a stronger ERD of the beta (18-25 Hz, 140-260 ms) and the lower mu rhythm (8-10 Hz, 320-440 ms) than processing names of visually explored tools, reflecting a possible reactivation of experiential sensorimotor information. Given the unexpected result that familiarized pseudo-words elicited an ERD comparable to names of manipulated tools, our findings could reflect a suppression of sensorimotor activity during the processing of objects with exclusively visual features.

MEG Multivariate Analysis Reveals Early Abstract Action Representations in the Lateral Occipitotemporal Cortex

Understanding other people's actions is a fundamental prerequisite for social interactions. Whether action understanding relies on simulating the actions of others in the observers' motor system or on the access to conceptual knowledge stored in nonmotor areas is strongly debated. It has been argued previously that areas that play a crucial role in action understanding should (1) distinguish between different actions, (2) generalize across the ways in which actions are performed (Dinstein et al., 2008; Oosterhof et al., 2013; Caramazza et al., 2014), and (3) have access to action information around the time of action recognition (Hauk et al., 2008). Whereas previous studies focused on the first two criteria, little is known about the dynamics underlying action understanding. We examined which human brain regions are able to distinguish between pointing and grasping, regardless of reach direction (left or right) and effector (left or right hand), using multivariate pattern analysis of magnetoencephalography data. We show that the lateral occipitotemporal cortex (LOTC) has the earliest access to abstract action representations, which coincides with the time point from which there was enough information to allow discriminating between the two actions. By contrast, precentral regions, though recruited early, have access to such abstract representations substantially later. Our results demonstrate that in contrast to the LOTC, the early recruitment of precentral regions does not contain the detailed information that is required to recognize an action. We discuss previous theoretical claims of motor theories and how they are incompatible with our data.

SIGNIFICANCE STATEMENT

It is debated whether our ability to understand other people's actions relies on the simulation of actions in the observers' motor system, or is based on access to conceptual knowledge stored in nonmotor areas. Here, using magnetoencephalography in combination with machine learning, we examined where in the brain and at which point in time it is possible to distinguish between pointing and grasping actions regardless of the way in which they are performed (effector, reach direction). We show that, in contrast to the predictions of motor theories of action understanding, the lateral occipitotemporal cortex has access to abstract action representations substantially earlier than precentral regions.

Lateralized modulation of beta-band power in sensorimotor areas during action observation

The cortical network for action observation includes areas of the visual cortex and non-visual areas, including areas of the motoric system. Parts of this network are known for their contralateral organization during motion execution, i.e., they predominantly control and respond to movements of the contralateral body side. We were interested whether this lateralized organization was also present during action observation. Human participants viewed point-light displays of human actors, where the actor was facing and moving either to the right or to the left, while participants' neuromagnetic activity was recorded using magnetoencephalography (MEG). We found that right and left facing movements elicited different activity in left and right motoric areas. This lateralization effect was found in two distinct spatio-temporal-spectral clusters: An early lateralization effect in medial sensors at 12-16 Hz and ~276-675 ms after stimulus onset, and a second cluster in more lateral sensors at 22-28 Hz and ~1275-1775 ms. Our results demonstrate that in addition to the known somatotopic organization of parts of the human motoric system, these areas also show a lateralization effect during action observation. Thus, our results indicate that the hemispheric organization of one's own body map known for motion execution extends to the visual observation of others' bodily actions and movements.

Alpha and beta band event-related desynchronization reflects kinematic regularities

The short-lasting attenuation of brain oscillations is termed event-related desynchronization (ERD). It is frequently found in the alpha and beta bands in humans during generation, observation, and imagery of movement and is considered to reflect cortical motor activity and action-perception coupling. The shared information driving ERD in all these motor-related behaviors is unknown. We investigated whether particular laws governing production and perception of curved movement may account for the attenuation of alpha and beta rhythms. Human movement appears to be governed by relatively few kinematic laws of motion. One dominant law in biological motion kinematics is the 2/3 power law (PL), which imposes a strong dependency of movement speed on curvature and is prominent in action-perception coupling. Here we directly examined whether the 2/3 PL elicits ERD during motion observation by characterizing the spatiotemporal signature of ERD. ERDs were measured while human subjects observed a cloud of dots moving along elliptical trajectories either complying with or violating the 2/3 PL. We found that ERD within both frequency bands was consistently stronger, arose faster, and was more widespread while observing motion obeying the 2/3 PL. An activity pattern showing clear 2/3 PL preference and lying within the alpha band was observed exclusively above central motor areas, whereas 2/3 PL preference in the beta band was observed in additional prefrontal-central cortical sites. Our findings reveal that compliance with the 2/3 PL is sufficient to elicit a selective ERD response in the human brain.

Beta oscillations and their functional role in movement perception

Neuronal oscillations refer to periodic changes of neuronal activity. A prominent neuronal oscillation, especially in sensorimotor areas, is the beta-frequency-band (∼ 13–29 Hz). Sensorimotor beta oscillations are predominantly linked to motor-related functions such as preparation and/or execution of movements. In addition, beta oscillations have been suggested to play a role in long-range communication between multiple brain areas. In this review, we assess different studies that show that sensorimotor beta oscillations are additionally involved in the visual perception and imagery of biological movements. We propose that sensorimotor beta oscillations reflect a mechanism of attempted matching to internally stored representations of movements. We additionally, provide evidence that beta oscillations play a role for the integration of visual and sensorimotor areas to a functional network that incorporates perceptual components at specific spatial-temporal profiles and transmits information across different areas.