Attention-related, cross-modality modulation of somatosensory neurons in primate ventrobasal (VB) thalamus

Attention-related modulation (AM) of the somatosensory responses of single neurons has been demonstrated in the cerebral cortex and medullary dorsal h orn, but not in the ventrobasal thalamus. The somatically evoked activity w as recorded of single units in the ventral posterior lateral thalamus (VPL) of awake monkeys while they detected the termination of task-relevant soma tic or visual stimuli. Eighteen of 56 somatically responsive VPL neurons ar e reported that were recorded for enough time for a complete analysis of th eir responses during both the visual and somatic attention tasks. All neuro ns were spontaneously active and responded either to innocuous cutaneous (1 3/18) or deep (5/18) stimuli. Seven neurons (7/18, 38.8%) showed AM of soma tosensory responsiveness. Two cells (2/7, 28.6%) showed AM only during the visual task, two others (2/7, 28.6%) only during the somatosensory task, an d three cells (3/7, 42.8%) showed AM during both tasks. All five cells show ing AM during the somatosensory task had enhanced responses to the task-rel evant somatic stimulus. In contrast, the somatosensory responses of all fiv e cells showing AM during the visual task were reduced. It is concluded tha t selective attention is associated with a modality specific modulation of the somatosensory responses of a sub-population of neurons within the prima te VPL nucleus.