Inferior frontal oscillations reveal visuo-motor matching for actions and speech: evidence from human intracranial recordings

The neural correspondence between the systems responsible for the execution and recognition of actions has been suggested both in humans and non-human primates. Apart from being a key region of this visuo-motor observation-execution matching (OEM) system, the human inferior frontal gyrus (IFG) is also important for speech production. The functional overlap of visuo-motor OEM and speech, together with the phylogenetic history of the IFG as a motor area, has led to the idea that speech function has evolved from pre-existing motor systems and to the hypothesis that an OEM system may exist also for speech. However, visuo-motor OEM and speech OEM have never been compared directly. We used electrocorticography to analyze oscillations recorded from intracranial electrodes in human fronto-parie-to-temporal cortex during visuo-motor (executing or visually observing an action) and speech OEM tasks (verbally describing an action using the first or third person pronoun). The results show that neural activity related to visuo-motor OEM is widespread in the frontal, parietal, and temporal regions. Speech OEM also elicited widespread responses partly overlapping with visuo-motor OEM sites (bilaterally), including frontal, parietal, and temporal regions. Interestingly a more focal region, the inferior frontal gyrus (bilaterally), showed both visuo-motor OEM and speech OEM properties independent of orolingual speech-unrelated movements. Building on the methodological advantages in human invasive electrocorticography, the present findings provide highly precise spatial and temporal information to support the existence of a modality-independent action representation system in the human brain that is shared between systems for performing, interpreting and describing actions. (C) 2015 Elsevier Ltd. All rights reserved.

Fully automated modulation of virtual-body ownership supresses fronto-parietal mu rhythm

Olaf Blanke, Nathaniel Evans

After continuously applying spatially and temporally congruent visuo-tactile stimulation to external, body-like objects, healthy humans feel the fake part to be the origin of the touch sensations and feel it to be their own. Incongruent stimulation nullifies both illusory changes. This Rubber Hand Illusion (RHI) is the most used paradigm to experimentally investigate healthy humans’ bodily self-consciousness and the extension of body ownership to foreign objects [1]. Standard RHI setups are limited by physical constraints and suffer the disadvantage of imprecise temporo-spatial stimulus control. Further, little is known about the neural and electrophysiological mechanisms associated with the crossmodal conflict and the induced changes in body ownership during the RHI. Here we recorded 64-channel electroencephalography (EEG) to investigate the electrophysiological changes while exposed to a carefully controlled, bilateral RHI induced by haptics and virtual reality (VR) technology. Methods Participants (n=8) sat at a table with a chin rest. Arms were placed (palms up) underneath the table to rest on the legs. A virtual scene depicting the real-world experimental scene was displayed on an immersive Head Mounted Display (HMD). We employed a 2x2 factorial design (Object, Stroking). Participants saw either two arms or two non-body cylinders (Object) projecting from their shoulders onto a virtual table, seeing the virtual arms or cylinder in a position ~20cm above their real arms. Visuo-tactile stimulation was provided by four vibration motors affixed to the palms of the (unseen) left and right hands and by animation of corresponding virtual motors on the virtual hands. Two visuo-tactile modes were defined (Stroking): 1) synchronous: virtual visual motors were shown to vibrate in temporal and spatial synchrony with the tactile vibration motors and 2) asynchronous: virtual visual motors were shown to vibrate with a temporal delay (100±50ms) and a randomly selected spatial direction with respect to the tactile vibration motor pattern. Two additional baseline conditions were recorded (no visual animation of the virtual motors and no tactile stimulation; no visual animation of the virtual motors with tactile stimulation). Subjective experience of the illusion was gauged by a questionnaire. 64-channel EEG was sampled at 2048Hz. Bipolar electrooculograms were recorded for later artifact removal. EEG analysis consisted of breaking 30s of spontaneous EEG data per condition into epochs of 2s. Epochs contaminated with eye blink artifacts or transient changes in electrode-to-scalp conductance were removed. Spectral power changes were computed in three frequency bands: alpha (8-13 Hz), beta (14-30 Hz) and gamma (30-100 Hz). Statistical analysis was performed at the scalp level and included a suprathreshold cluster permutation test to control for Type I errors. The generators of the significant scalp maps were localized with an inverse solution (sLORETA) [2]. Results Repeated ANOVA analysis of the questionnaire indicated a significant interaction between synchrony and question (F=1.65, p=0.03), and a main synchrony effect (F=40.29, p

2010

Action prediction based on anticipatory brain potentials during simulated driving

Ricardo Andres Chavarriaga Lozano, Lucian Andrei Gheorghe, Zahra Khaliliardali

Objective. The ability of an automobile to infer the driver's upcoming actions directly from neural signals could enrich the interaction of the car with its driver. Intelligent vehicles fitted with an on-board brain–computer interface able to decode the driver's intentions can use this information to improve the driving experience. In this study we investigate the neural signatures of anticipation of specific actions, namely braking and accelerating. Approach. We investigated anticipatory slow cortical potentials in electroencephalogram recorded from 18 healthy participants in a driving simulator using a variant of the contingent negative variation (CNV) paradigm with Go and No-go conditions: count-down numbers followed by 'Start'/'Stop' cue. We report decoding performance before the action onset using a quadratic discriminant analysis classifier based on temporal features. Main results. (i) Despite the visual and driving related cognitive distractions, we show the presence of anticipatory event related potentials locked to the stimuli onset similar to the widely reported CNV signal (with an average peak value of −8 μV at electrode Cz). (ii) We demonstrate the discrimination between cases requiring to perform an action upon imperative subsequent stimulus (Go condition, e.g. a 'Red' traffic light) versus events that do not require such action (No-go condition; e.g. a 'Yellow' light); with an average single trial classification performance of 0.83 ± 0.13 for braking and 0.79 ± 0.12 for accelerating (area under the curve). (iii) We show that the centro-medial anticipatory potentials are observed as early as 320 ± 200 ms before the action with a detection rate of 0.77 ± 0.12 in offline analysis. Significance. We show for the first time the feasibility of predicting the driver's intention through decoding anticipatory related potentials during simulated car driving with high recognition rates.

Institute of Physics2015

Distinct vestibular effects on early and late somatosensory cortical processing in humans

Fosco Bernasconi, Olaf Blanke, Christian Pfeiffer, Michiel van Elk

In non-human primates several brain areas contain neurons that respond to both vestibular and somatosensory stimulation. In humans, vestibular stimulation activates several somatosensory brain regions and improves tactile perception. However, less is known about the spatio-temporal dynamics of such vestibular-somatosensory interactions in the human brain. To address this issue, we recorded high-density electroencephalography during left median nerve electrical stimulation to obtain Somatosensory Evoked Potentials (SEPs). We analyzed SEPs during vestibular activation following sudden decelerations from constant-velocity (90 degrees/s and 60 degrees/s) earth-vertical axis yaw rotations and SEPs during a non-vestibular control period. SEP analysis revealed two distinct temporal effects of vestibular activation: An early effect (28-32 ms post-stimulus) characterized by vestibular suppression of SEP response strength that depended on rotation velocity and a later effect (97-112 ms post-stimulus) characterized by vestibular modulation of SEP topographical pattern that was rotation velocity-independent. Source estimation localized these vestibular effects, during both time periods, to activation differences in a distributed cortical network including the right postcentral gyrus, right insula, left precuneus, and bilateral secondary somatosensory cortex. These results suggest that vestibular-somatosensory interactions in humans depend on processing in specific time periods in somatosensory and vestibular cortical regions. (C) 2015 Elsevier Inc. All rights reserved.