The human globus pallidus internus is sensitive to rewards – Evidence from intracerebral recordings

Background The globus pallidus internus (GPi) is the final output relay of the basal ganglia for the control of movements but has also been shown to belong to a second pathway projecting to the lateral habenula. This latter pathway is related to reward processing. Method This prompted us to record, in eight patients receiving deep brain stimulation of the GPi for the alleviation of various movement disorders, local field potentials (LFP) while these patients performed a lottery task. The task entailed choosing between a higher and a lower number, which changed their color after the patient's choice with red (green) signaling a loss (win, in Euro cents) corresponding to the chosen number. Results Surface recordings showed a feedback related negativity from a frontal midline site, while time domain averages in the GPi showed differential modulation depending on the valence of the stimulus with polarity inversion indicating that this reward-modulated activity was indeed generated locally. Furthermore, wavelet decomposition of the LFP showed a reward-related response in the high beta/low gamma range. Conclusion We conclude that human GPi is involved in reward processing, possibly in relation to the lateral habenula.