Influence of behavioral state on auditory processing in the marmoset midbrain

Abstract

Recent work shows that neurons in the inferior colliculus (IC) undergo receptive field changes during auditory behavior in ferrets (Slee & David, 2015. J. Neurosci.). In this study, we tested for similar effects in the marmoset monkey, a highly vocal primate species. We trained two marmosets to detect a pure tone target embedded in a background of random spectral shape (RSS) distractor stimuli. We recorded single-unit activity in the central nucleus of the IC (ICC). Neural responses to targets and distractors were compared between conditions when the marmoset performed the detection task or listened passively. When target frequency was near the neuronal best frequency (BF), responses to distractors were suppressed in about half of the neurons during behavior. Target responses were modulated in some neurons but suppression or enhancement was equally likely. We also measured effects of task engagement in non-central divisions of the IC (NCIC). There, target responses were strongly enhanced during behavior in about half of neurons in this region (median change = 70%). We also found a subset of NCIC neurons that responded with increased firing following the target sound, possibly encoding a reward-related signal. This study replicates our previous finding that distractor responses are suppressed during auditory behavior in the ferret IC. In addition, we found an area in the NCIC with large enhancement of target responses during behavior, suggesting that task engagement produces distinct effects across subdivisions of the IC.