Locus coeruleus activation enhances thalamic feature selectivity via norepinephrine regulation of intrathalamic circuit dynamics.

We investigated locus coeruleus (LC) modulation of thalamic feature selectivity through reverse correlation analysis of single-unit recordings from different stages of the rat vibrissa pathway. LC activation increased feature selectivity, drastically improving thalamic information transmission. We found that this improvement was dependent on both local activation of α-adrenergic receptors and modulation of T-type calcium channels in the thalamus and was not due to LC modulation of trigeminothalamic feedforward or corticothalamic feedback inputs. Tonic spikes with LC stimulation carried three times the information as did tonic spikes without LC stimulation. Modeling confirmed norepinephrine regulation of intrathalamic circuit dynamics led to the improved information transmission. Behavioral data demonstrated that LC activation increased the perceptual performance of animals performing tactile discrimination tasks through LC-norepinephrine optimization of thalamic sensory processing. These results suggest a new subdimension within the tonic mode in which brain state can optimize thalamic sensory processing through modulation of intrathalamic circuit dynamics.