UC Davis

Selective attention helps us to make sense of noisy sensory environments by prioritizing representation of stimuli relevant to behavioral demands while ignoring a wide array of distractors. Yet, the neural mechanisms that underlie attention remain poorly understood. In the following studies, we aim to assess how selective attention effects encoding of amplitude modulated noise (AM) in single neurons from primary (A1) and secondary (middle lateral belt, ML) auditory cortex of Rhesus macaques. We assess two different forms of attention – feature-selective attention and intermodal attention – and compare to previous task-engagement studies to probe distinctions between arousal and selective attention effects on neural activity. Further, we assess choice-related activity during these behavioral tasks and how such activity is modulated by attentional contexts. We found that feature-selective attention did not significantly affect the encoding of AM in either A1 or ML neurons. However, choice-related activity did shift between attentional conditions in both A1 and ML, suggesting that choice-related activity cannot be reflective of motor preparation alone. During a novel intermodal attentional task, we found that AM discrimination was significantly improved when animals were presented with unimodal auditory stimuli, compared to bimodal audiovisual stimuli. However, there were few differences in AM discrimination between bimodal conditions when subjects were attending to the auditory component of the stimulus rather than ignoring it to attend the visual component. These findings suggest that the effects seen are largely an effect of distracting stimuli, rather than selectively attending to auditory stimuli over visual stimuli. Finally, we found that choice-related activity was stronger on trials when audiovisual stimuli provided congruent evidence towards a response rather than when information from the two modalities was in conflict, suggesting that choice-related activity is modulated by reward-expectation.