Central thalamic contributions to arousal regulation and neurological disorders of consciousness

This review focuses on the contributions of the central thalamus to normalmechanisms of arousal regulation and to neurological disorders of consciousness. Forebrain arousal is regulated by as-cending influences from brainstem/basal forebrain neuronal populations (“arousal systems”) and control signals descending from frontal cortical systems. These subcortical and cortical systems have converging projections to the central thalamus that emphasize their role in maintaining or-ganized behavior during wakefulness. Central thalamic neurons appear to be specialized both anatomically and physiologically to support distributed network activity that maintains neuronal firing patterns across long-range cortico–cortical pathways and within cortico–striatopallidal– thalamocortical loop connections. Recruitment of central thalamic neurons occurs in response to increasing cognitive demand, stress, fatigue, and other perturbations that reduce behavioral performance. In addition, the central thalamus receives projections from brainstem pathways evolved to rapidly generate brief shifts of arousal associated with the appearance of salient stimuli across different sensory modalities. Through activation of the central thalamus, neurons across the cerebral cortex and striatum can be depolarized and their activity patterns selectively gated by descending or ascending signals related to premotor attention and alerting stimuli. Direct injur