RESUMEN
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
RESUMEN
We applied transcranial alternating current stimulation (tACS) to the primary motor cortex (M1) at different frequencies during an index-thumb pinch-grip observation task. To estimate changes in the corticospinal output, we used the size of motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation (TMS) of M1 using an online MRI-guided simultaneous TMS-tACS approach. The results of the beta-tACS confirm a non-selective increase in corticospinal excitability in subjects at rest; an increase was observed for both of the tested hand muscles, the first dorsal interosseous (FDI) and the abductor digiti minimi (ADM). However, during action observation of the pinch-grip movement, the increase of corticospinal excitability was only observed for the prime mover FDI muscle and took place during alpha-tACS, while gamma-tACS affected both the FDI and control muscle (ADM) responses. These phenomena likely reflect the hypothesis that the mu and gamma rhythms specifically index the downstream modulation of primary sensorimotor areas by engaging mirror neuron activity. The current neuromodulation approach confirms that tACS can be used to induce neurophysiologically detectable state-dependent enhancement effects, even in complex motor-cognitive tasks.
Asunto(s)
Potenciales Evocados Motores/fisiología , Corteza Motora/fisiología , Músculo Esquelético/fisiología , Tractos Piramidales/fisiología , Estimulación Transcraneal de Corriente Directa/métodos , Estimulación Magnética Transcraneal/métodos , Adulto , Electromiografía/métodos , Femenino , Ritmo Gamma , Humanos , Masculino , Neuronas Motoras/fisiología , Movimiento/fisiología , Corteza Sensoriomotora/fisiologíaRESUMEN
The heterogeneity of our visual environment typically reduces the speed with which a singleton target can be found. Visual search theories explain this phenomenon via nontarget similarities and dissimilarities that affect grouping, perceptual noise, and so forth. In this study, we show that increasing the heterogeneity of a display can facilitate rather than inhibit visual search for size and orientation singletons when heterogeneous features smoothly fill the transition between highly distinguishable nontargets. We suggest that this smooth transition reduces the "segmentability" of dissimilar items to otherwise separate subsets, causing the visual system to treat them as a near-homogenous set standing apart from a singleton. (PsycINFO Database Record
