Cortical signatures of vicarious tactile experience in four-month-old infants.

The human brain recruits similar brain regions when a state is experienced (e.g., touch, pain, actions) and when that state is passively observed in other individuals. In adults, seeing other people being touched activates similar brain areas as when we experience touch ourselves. Here we show that already by four months of age, cortical responses to tactile stimulation are modulated by visual information specifying another person being touched. We recorded somatosensory evoked potentials (SEPs) in 4-month-old infants while they were presented with brief vibrotactile stimuli to the hands. At the same time that the tactile stimuli were presented the infants observed another person's hand being touched by a soft paintbrush or approached by the paintbrush which then touched the surface next to their hand. A prominent positive peak in SEPs contralateral to the site of tactile stimulation around 130 ms after the tactile stimulus onset was of a significantly larger amplitude for the "Surface" trials than for the "Hand" trials. These findings indicate that, even at four months of age, somatosensory cortex is not only involved in the personal experience of touch but can also be vicariously recruited by seeing other people being touched.

High-Frequency Transcranial Random Noise Stimulation Enhances Perception of Facial Identity.

Recently, a number of studies have demonstrated the utility of transcranial current stimulation as a tool to facilitate a variety of cognitive and perceptual abilities. Few studies, though, have examined the utility of this approach for the processing of social information. Here, we conducted 2 experiments to explore whether a single session of high-frequency transcranial random noise stimulation (tRNS) targeted at lateral occipitotemporal cortices would enhance facial identity perception. In Experiment 1, participants received 20 min of active high-frequency tRNS or sham stimulation prior to completing the tasks examining facial identity perception or trustworthiness perception. Active high-frequency tRNS facilitated facial identity perception, but not trustworthiness perception. Experiment 2 assessed the spatial specificity of this effect by delivering 20 min of active high-frequency tRNS to lateral occipitotemporal cortices or sensorimotor cortices prior to participants completing the same facial identity perception task used in Experiment 1. High-frequency tRNS targeted at lateral occipitotemporal cortices enhanced performance relative to motor cortex stimulation. These findings show that high-frequency tRNS to lateral occipitotemporal cortices produces task-specific and site-specific enhancements in face perception.