Location-Specific Facilitation in Primate Auditory Cortex

Neural responses to sensory stimuli are markedly influenced by the context in which a stimulus is preceded or embedded. Cortical and subcortical neurons typically exhibit adaptation to repetitive auditory, visual, somatosensory, and olfactory stimulation. Here, we investigated single neuron responses to sequences of sounds either repeatedly delivered from a single spatial location or randomly delivered from multiple spatial locations in the auditory cortex of awake marmosets. Instead of inducing adaptation, repetitive stimulation from a target speaker evoked long-lasting, location-specific facilitation (LSF) in many neurons, irrespective of the visibility of the target speaker. The extent of LSF decreased with decreasing presentation probability of the target speaker. Intracellular recordings showed that repetitive sound stimulation evoked sustained membrane potential depolarization which gave rise to firing rate facilitation. Computational models suggest two distinct neural mechanisms underlying LSF. Our findings revealed a novel form of contextual modulation in the auditory cortex that may play a role in auditory streaming and predictive coding.