Sensory-interference in rat primary somatosensory cortical neurons.

To study sensory interaction in the primary somatosensory cortex (SI), we registered 221 neurons in the SI of pentobarbital-anaesthetized Wistar rats. Tactile stimulation was applied in the receptive field of the SI neuron with an electronically controlled probe (20 ms duration). Tactile stimulation elicited 2.33 +/- 0.13 spikes per stimulus in SI neurons. Simultaneous application of paintbrush tickles of the contralateral limb usually decreased tactile responses (1.59 +/- 0.11 spikes per stimulus). This effect was considered a 'sensory-interference'. Light flashes applied at random did not modify tactile response. Applying atropine (1 mm), a muscarinic receptor antagonist, and bicuculline (1 mm), a GABAA receptor antagonist, to the SI cortex blocked the sensory-interference effect, while application of mecamylamine (10 mm), a nicotinic cholinergic receptor antagonist, did not affect sensory-interference. Results reveal sensory interactions in SI cortex that control tactile responses, and suggest the participation of the basal forebrain in the sensory-interference effect.