BEYOND LOCOMOTION: VOLITIONAL MODULATION OF THE MESENCEPHALIC LOCOMOTOR REGION (MLR) FOR ABSTRACT BCI CONTROL

Instrumental conditioning of neural activity through Brain-machine interfaces (BCI) has been extensively demonstrated in cortical regions, establishing them as sources of volitional signals. In contrast, the potential for volitional modulation of non-cortical structures is poorly understood. Here, we investigated whether rats could produce arbitrary neural activity patterns in the Mesencephalic Locomotor Region (MLR) to control an auditory cursor. Long-Evans rats (N=6) were implanted with a 16-channel microelectrode array in the MLR. Four single units were isolated and assigned to two opposing ensembles. The difference in ensemble firing rates controlled the auditory cursor’s frequency. To receive a sucrose reward, rats had to modulate the ensembles in opposite directions to reach a target within 30 seconds. Chance performance (30%) was established via baseline recordings. All rats successfully learned the task within a 10-day training period. Success rate significantly increased from 34.4±11.9% to 73.6±7.9% (mean±SEM), while time-to-completion decreased from 11.2±1.6s to 8.0±1.6s between the first and last two days. Modulation was independent of overt movement or auditory feedback. This goal-directed control showed rapid learning adaptation to new task contingencies within single sessions. The MLR, traditionally viewed as a hard-wired locomotor center, is capable of volitional modulation independent of overt movements. The performance metrics are comparable to those reported in cortical studies using the same task, suggesting that MLR is subject to similar reinforcement learning rules. This highlights midbrain plasticity and extends BCI potential to subcortical structures.