Responses of Cortical Neurons to Intracortical Microstimulation in Awake Primates.

Area of Science:

• Neuroscience
• Neural Engineering

Background:

• Intracortical microstimulation (ICMS) is widely used but its precise effects on neuronal activation remain unclear.
• Understanding these effects is vital for optimizing ICMS in experimental and clinical applications.

Purpose of the Study:

• To investigate the detailed responses of cortical neurons in awake nonhuman primates to ICMS.
• To characterize the excitatory and inhibitory dynamics following electrical stimulation.

Main Methods:

• Recorded single-unit activity in the primary motor cortex (M1) of macaque monkeys during ICMS.
• Delivered single-pulse and tonic repetitive stimulation using Utah arrays.
• Varied stimulus current amplitudes (5-50 μA) and frequencies (2-20 Hz).

Main Results:

• Single ICMS pulses evoked spikes with delays up to 12 ms, followed by inhibition up to 150 ms.
• Higher currents increased spike probability and inhibition duration.
• Stimulation parameters modulated spike probability and inhibition, with high-frequency stimulation having a greater impact.
• Neural responses depended on spontaneous firing rates and spike timing relative to stimulus onset.

Conclusions:

• ICMS elicits complex excitatory and inhibitory neural dynamics.
• These dynamics are influenced by stimulation parameters and intrinsic neuronal properties.
• Findings highlight the need to consider these response complexities in ICMS applications.