Role of the midline thalamus in arousal control

Abstract

Arousal is a prerequisite for higher cognitive functions such as consciousness. Although the correlation between firing patterns of thalamus and the arousal have been reported, it has been unclear that the activities of the specific thalamic region is sufficient to induce the arousal. Here, we show that arousal can be induced by the modulation of two firing modes in the midline thalamus. The tonic activation of the midline thalamus can induce the arousal during non-rapid eye movement (NREM) sleep, and this effect can be mediated by the glu-tamatergic inputs of the brainstem arousal center, but not by cholinergic inputs. The high frequency interaction of different cortical regions is increased by tonic activation of midline thalamus during waking state. Because of the controversy about the role of the burst firings, we make a drowsiness behavioral model, a competition of the wake and sleep, to show which state involves the burst firings. Inhibition of the burst firings in the whole thalamus or midline thalamus increases the waking frequency by decreasing the duration of sleep-like behaviors during drowsiness. These results suggest the existence of specific thalamic route which can modulate the cortical arousal by changing its firing patterns.