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Rebecca E Hailperin-Lausch, Elizabeth B daSilva, Bennett I Bertenthal; Alpha Desynchronization is Modulated by Kinematic and Contextual Properties of the Observed Reach. Journal of Vision 2019;19(10):276b. doi: https://doi.org/10.1167/19.10.276b.
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Considerable neurophysiological, neuropsychological, and behavioral evidence suggests that the observation of goal-directed actions is mapped to the motor cortex. Less clear is whether this neural processing is modulated by kinematic and contextual properties. In this study, we test whether EEG alpha desynchronization (8 – 12 Hz oscillations recorded from scalp regions overlying the sensorimotor cortex) is modulated by reach type (ipsilateral vs contralateral) or by the affordances of the object serving as the goal of the reach. Stimuli (Figure 1A) consisted of a 2,000 ms video of an adult male facing the observer and reaching for a cup (1,000 ms) and then holding it (1,000 ms). Twenty-four participants were tested with eight conditions:actor reaching ipsilaterally or contralaterally (hand crossing the body midline); cup oriented either upright or inverted; location of the cup’s handle either congruent or incongruent with the reach. There were a total of 408 trials that included 24 probe trials for checking attention. EEG was recorded using an EGI 64-electrode Hydrocel Geodesic Sensor Net, sampled at 1,000 Hz, and segmented into 3,800-ms epochs (beginning 500 ms before and ending 3,300 ms after the onset of the stimulus). Time-frequency analyses were performed on each artifact-free trial with Morelet wavelets at 1-Hz intervals. EEGs from anterior, central, and posterior electrode clusters were analyzed from both hemispheres. The results revealed significantly greater desynchronization (stimulus event – baseline) from central electrodes in the left hemisphere with significant differences as a function of reach type and reach congruency for upright cups only (Figures 1B-C). Observing the video depicting the most discrepant stimulus - incongruent, ipsilateral reaches - resulted in the greatest desynchronization (Figure 1D). These results suggest that alpha desynchronization in the sensorimotor cortex is sensitive to not only goal-directed actions, but also to the reach type and affordance associated with the action.
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