Engaging in an auditory task suppresses responses in auditory cortex

Although systems involved in attentional selection have been studied extensively, much less is known about non-selective systems. To study these preparatory mechanisms, we compared activity in auditory cortex elicited by sounds while rats performed an auditory task (“engaged”) with activity elicited by identical stimuli while subjects were awake but not performing a task (“passive”). Surprisingly, we found that engagement suppressed responses, an effect opposite in sign to that elicited by selective attention. In the auditory thalamus, however, engagement enhanced spontaneous firing rates but did not affect evoked responses. These results demonstrate that in auditory cortex, neural activity cannot be viewed simply as a limited resource allocated in greater measure as the state of the animal passes from somnolent to passively listening to engaged and attentive. Instead the engaged condition possesses a characteristic and distinct neural signature in which sound-evoked responses are paradoxically suppressed.