Semi-chronic laminar recordings in the brainstem of behaving marmoset monkeys.

Background: Chronic recordings with multi-electrode arrays are widely used to study neural networks underlying complex primate behaviors. Most of these systems are designed for studying neural activity in the cortical hemispheres resulting in a lack of devices being capable of simultaneously recording from ensembles of neurons in deep brainstem structures. However, to fully understand complex behavior, it is fundamental to also decipher the intrinsic mechanisms of the underlying motor pattern generating circuits in the brainstem.

New Method: We report a light-weight system that simultaneously measures single-unit activity from a large number of recording sites in the brainstem of marmoset monkeys. It includes a base chamber fixed to the animal's skull and a removable upper chamber that can be semi-chronically mounted to the base chamber to flexibly position an embedded micro-drive containing a 32-channel laminar probe to record from various positions within the brainstem for several weeks.

Results: The current system is capable of simultaneously recording stable single-unit activity from a large number of recording sites in the brainstem of vocalizing marmoset monkeys.

Comparison With Existing Methods: To the best of our knowledge, chronic systems to record from deep brainstem structures with multi-site laminar probes in awake, behaving monkeys do not yet exist.

Conclusions: The semi-chronic implantation of laminar electrodes into the brainstem of behaving marmoset monkeys opens new research possibilities in fully understanding the neural mechanisms underlying complex behaviors in marmoset monkeys.