State-dependent cortical processing: Cholinergic modulation of visual responses
The nucleus basalis of the basal forebrain is an essential component of the neuromodulatory system controlling the behavioral state of an animal, and it is thought to play key roles in regulating arousal and attention. However, the effect of NB activation on sensory processing remains poorly understood. Using polytrode recording in rat visual cortex, we show that NB stimulation causes prominent decorrelation between neurons and marked improvement in the reliability of neuronal responses to natural scenes. The decorrelation depends on local activation of cortical muscarinic acetylcholine receptors, while the increased reliability involves distributed neural circuits, as evidenced by NB-induced changes in thalamic responses. Further analysis showed that the decorrelation and increased reliability improve cortical representation of natural stimuli in a complementary manner. Thus, the basal forebrain neuromodulatory circuit, which is known to be activated during aroused and attentive states, acts through both local and distributed mechanisms to improve sensory coding.