Brain state and contrast sensitivity in the awake visual thalamus.

Neuronal responses to visual stimuli depend on both the nature of the stimulus and brain state. Here we examined the contrast sensitivity of visual thalamic neurons as awake rabbits shifted between alert and nonalert states. We found that despite a large increase in response gain with alertness, contrast sensitivity remained nearly constant. This accurate scaling might be achieved through a balanced increase in excitation and inhibition with alertness.