Objective: To study motor cognition in the human motor thalamus at the single cell and population level.

Background: The motor thalamus, in particular its cerebellar-receiving area at the junction of nc. ventralis oralis posterior and nc. ventralis intermedius (VIM/VOP), is regularly approached in the context of deep brain stimulation (DBS) surgery for tremor. In contrast to its well-established clinical effect, few studies have addressed motor coding properties of VIM/VOP neurons.

Method: Here, we performed intraoperative microelectrode recordings during an externally cued force grip task in 16 patients with tremores of different etiology undergoing DBS surgery in VIM/VOP.

Results: A subset of thalamic neurons stereotypically responded to task-cues with phasic increases of their discharge rates. At a population level, thalamic LFPs showed peaks in the theta-frequency range in response to the initial instruction cues. During the preparatory phase, thalamic firing was tonically suppressed. This discharge suppression was mirrored by a stepwise, cue-dependent decrease of beta synchrony in the LFP as the go cue was approached. In contrast, gripping movements were generally associated with brisk and sustained neural activations, the strength of which correlated with the force level. At a population level, movements led to pronounced beta desynchronisation in conjunction with a marked increase of power in the gamma frequency range.

Conclusion: Different subsets of human VIM/VOP neurons are involved in cued movement preparation and movement, respectively. Our results disclose the tight interrelationship between oscillatory thalamic population dynamics and rate coding of single thalamic neurons.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cued-movement-preparation-and-movement-coding-in-human-thalamic-neurons/