Anesthetic manipulations provide much-needed causal evidence for neural correlates of consciousness, but nonspecific drug effects complicate their interpretation. Evidence suggests that thalamic deep brain stimulation (DBS) can either increase or decrease consciousness, depending on the stimulation target and parameters. The putative role of the central lateral thalamus (CL) in consciousness makes it an ideal DBS target to manipulate circuit-level mechanisms in corticostriatothalamic (CST) systems, thereby influencing consciousness and related processes. We used multimicroelectrode DBS targeted to CL in macaques while recording from frontal, parietal, and striatal regions. DBS induced episodes reminiscent of absence epilepsy, here termed absence-like activity (ALA), with decreased behavior and vacant staring coinciding with low-frequency oscillations. DBS modulated ALA likelihood in a frequency-specific manner. ALA events corresponded to decreases in measures of neural complexity (entropy) and integration (Phi*), an index of consciousness, and substantial changes to communication in CST circuits. During ALA, power spectral density and coherence at low frequencies increased across CST circuits, especially in thalamoparietal and corticostriatal pathways. Decreased consciousness and neural integration corresponded to shifts in corticostriatal network configurations that dissociated parietal and subcortical structures. Overall, the features of ALA and implicated networks were similar to those of absence epilepsy. As this same multimicroelectrode DBS method, but at different stimulation frequencies, can also increase consciousness in anesthetized macaques, it can be used to flexibly address questions of consciousness with limited confounds, as well as inform clinical investigations of absence epilepsy and other consciousness disorders.
Thalamic deep brain stimulation as a paradigm to reduce consciousness: implications for cortico-striatal dynamics, absence epilepsy and consciousness studies
