Structural and functional changes of deep layer pyramidal neurons surrounding microelectrode arrays implanted in rat...

Area of Science:

• Neuroscience
• Biomaterials Science
• Neural Engineering

Background:

• Implanted electrodes are crucial for understanding brain function and treating neurological disorders.
• The foreign body response to implanted electrodes can compromise device efficacy and signal integrity.
• Previous research has explored device-tissue interactions, but direct functional assessments of surrounding neurons are limited.

Purpose of the Study:

• To investigate the structural and functional alterations in deep layer pyramidal neurons adjacent to implanted silicon or polyimide electrodes in the rat motor cortex.
• To correlate observed neuronal changes with potential mechanisms for signal degradation in chronically implanted brain-computer interfaces.

Main Methods:

• Whole-cell electrophysiology and 2-photon imaging were used to assess individual neurons in 300 µm thick tissue slices.
• Neurons surrounding electrodes implanted 1 or 6 weeks prior were analyzed for structural and functional properties.
• Both silicon and polyimide-based electrode materials were evaluated.

Main Results:

• Neurons near implanted electrodes exhibited disrupted dendritic arbors and reduced spine density.
• A decrease in spontaneous excitatory postsynaptic current frequency and reduced sag amplitude were observed.
• Increased spike frequency adaptation and filopodia density were noted in surrounding neurons.

Conclusions:

• Implanted electrodes induce significant structural and functional changes in nearby neurons.
• These neuronal alterations may explain signal loss and instability common with chronic electrode use.
• This study provides novel insights into electrode-tissue interactions, impacting neural implant design and performance.