Related Experiment Video
Updated: Mar 29, 2026
Multiscale Investigations of Cortical Processing by Integrating Laminar Polytrodes and Optogenetics with Micro Electrocorticography in Rodents
Published on: May 23, 2025
Intracortical Microstimulation Parameters Dictate the Amplitude and Latency of Evoked Responses
Meghan Watson1, Numa Dancause2, Mohamad Sawan3
1Polystim Neurotechnologies, Institute of Biomedical Engineering, Polytechnique, Montreal, Quebec, Canada; Département de Neurosciences, Faculté de Médecine, Université de Montréal, Montreal, Quebec, Canada.
Background:
Microstimulation of brain tissue plays a key role in a variety of sensory prosthetics, clinical therapies and research applications. However, the effects of stimulation parameters on the responses they evoke remain widely unknown.
Objective:
We aimed to investigate the contribution of each stimulation parameter to the response and identify interactions existing between parameters.
Methods:
Parameters of the constant-current, biphasic square waveform were examined in acute terminal experiments under ketamine anaesthesia. The motor cortex of 7 Sprague-Dawley rats was stimulated while recording motor evoked potentials (MEP) from the forelimb. Intracortical microstimulation (ICMS) parameters were systematically tested in a pair-wise fashion to observe the influence of each parameter on the amplitude and latency of the MEP.
Results:
The amplitude of the MEP increased continually with stimulus amplitude (p < 0.001) and pulse duration (p = 0.001) throughout the range tested. Increases were also observed when stimuli were raised from low to moderate values of frequency (p = 0.022) and train duration (p = 0.045), after which no further excitation occurs. The latency of MEP initiation decreased when stimulus amplitude (p = 0.037) and frequency (p = 0.001) were raised from low to moderate values, after which the responses plateaued. MEP latencies were further reduced by increasing the pulse duration (p = 0.011), but train duration had no effect.
Conclusions:
Our data indicate that MEP amplitude and onset latency can be modulated by alterations to a number of stimulus parameters, even in restrictive paradigms, and suggest that the parameters of the standard ICMS signal used for evoking movements from the motor cortex can be further optimized.
