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Neuronal loss due to prolonged controlled-current stimulation with chronically implanted microelectrodes in the cat
Douglas McCreery1, Victor Pikov, Philip R Troyk
1Neural Engineering Program, Huntington Medical Research Institutes, Pasadena, CA 91105, USA. dougmc@hmri.org
Journal of Neural Engineering
|May 13, 2010
Summary
High electrical stimulation from iridium microelectrodes can cause neuronal loss in the cat sensorimotor cortex. Lower stimulation or intermittent pulsing reduces this effect, but mechanical injury from electrode implantation also contributes to neuron loss.
Area of Science:
- Neuroscience
- Biomedical Engineering
- Materials Science
Background:
- Long-term implantation of neural electrodes is common in research and clinical applications.
- Understanding the impact of electrical stimulation parameters on neural tissue is crucial for safe and effective device design.
Purpose of the Study:
- To investigate the effects of chronic electrical stimulation via activated iridium microelectrodes on neuronal density in the feline sensorimotor cortex.
- To determine the influence of stimulation parameters, including charge density and duty cycle, on neural tissue response.
Main Methods:
- Activated iridium microelectrodes were implanted in the sensorimotor cortex of seven adult cats for extended periods (450-1282 days).
- Electrodes were subjected to pulsed electrical stimulation at various charge densities (100-200 microC cm(-2)) and duty cycles (100% and 50%) for 240 hours.
- Neuronal density was assessed in the tissue surrounding the microelectrode tips.
Main Results:
- Continuous stimulation at 2 nC/phase (100 microC cm(-2)) did not alter neuronal density.
- Higher stimulation (4 nC/phase, 200 microC cm(-2)) with a 100% duty cycle caused neuronal loss within 150 microm of the electrode tips.
- A 50% duty cycle reduced the radius of neuronal loss to approximately 60 microm, but mechanical injury from electrode implantation also contributed significantly to observed neuronal loss.
Conclusions:
- Electrical stimulation parameters, specifically charge density and duty cycle, critically influence neuronal survival around implanted iridium microelectrodes.
- While high stimulation can induce neuronal loss, mechanical trauma from long-term implantation also poses a significant risk to surrounding neural tissue.
- Optimizing stimulation protocols and considering mechanical effects are essential for minimizing tissue damage in neural implant applications.
