Inhibitory circuits for visual processing in thalamus

Synapses made by local interneurons dominate the intrinsic circuitry of the mammalian visual thalamus and influence all signals traveling from the eye to cortex. Here we draw on physiological and computational analyses of receptive fields in the cat's lateral geniculate nucleus to describe how inhibition helps to enhance selectivity for stimulus features in space and time and to improve the efficiency of the neural code. Further, we explore specialized synaptic attributes of relay cells and interneurons and discuss how these might be adapted to preserve the temporal precision of retinal spike trains and thereby maximize the rate of information transmitted downstream.

► Patterns of synaptic response in thalamus optimize the efficiency of neural coding.
► Local interneurons and relay cells have push–pull excitation and inhibition.
► Push–pull drives firing between burst and tonic modes.
► Push–pull sharpens selectivity, removes redundancy and extends dynamic range.
► Receptive fields compute the 2nd (spatial) and 1st (temporal) derivative of images.