Attention modulates synchronized neuronal firing in primate somatosensory cortex

A potentially powerful information processing strategy in the brain is to t ake advantage of the;temporal structure of neuronal spike trains. An increa se in synchrony within the neural representation of an object or location i ncreases the efficacy of that neural representation at the next synaptic st age in the brain; thus, increasing synchrony is a candidate for the neural correlate of attentional selection(1). We investigated the synchronous firi ng of pairs of neurons in the secondary somatosensory cortex (SII) of three monkeys trained to switch attention between a visual task and a tactile di scrimination task. We found that most neuron pairs in SII cortex fired sync hronously and, furthermore, that the degree of synchrony was affected by th e monkey's attentional state. In the monkey performing the most difficult t ask, 35% of neuron pairs that fired synchronously changed their degree of s ynchrony when the monkey switched attention between the tactile and visual tasks. Synchrony increased in 80% and decreased in 20% of neuron pairs affe cted by attention.