PULSES TO PATTERNS: ELECTRICAL AND OPTOGENETIC STIMULATION STUDIES IN MACAQUE MONKEYS

Neurostimulation techniques like electrical and optogenetic stimulation offer precise control over neural circuits, enabling causal insights that link brain function to behavior. As a key animal model for brain stimulation, macaque monkeys have been instrumental in generating some of the most significant insights. Yet, a comprehensive overview of the specific brain regions studied and the range of stimulation settings has been lacking. We performed a systematic review of the literature and found a strong focus on regions that reliably evoke motor or oculomotor responses, like the primary motor cortex and superior colliculus, while many higher-order and multimodal areas remain underexplored. The strength of the currents of electrical stimulation depends primarily on the electrode type, and the waveform parameters depend on practical considerations. Stimulation frequencies have been explored only in a limited range, particularly in the cortex, yet their effects may be more important than previously recognized. Macaque optogenetic stimulation parameters vary widely, highlighting the need to report amplitude using consistent units. Our analysis provides a detailed overview of the brain regions studied and the stimulation parameters used in primate neurostimulation. Future studies can leverage these insights, taking advantage of recent advances in hardware, such as multi-channel probes, and software, including data-driven and adaptive stimulation algorithms.