Optogenetic micro-electrocorticography for modulating and localizing cerebral cortex activity.
OBJECTIVE
Spatial localization of neural activity from within the brain with electrocorticography (ECoG) and electroencephalography remains a challenge in clinical and research settings, and while microfabricated ECoG (micro-ECoG) array technology continues to improve, complementary methods to simultaneously modulate cortical activity while recording are needed.


METHODS
We developed a neural interface utilizing optogenetics, cranial windowing, and micro-ECoG arrays fabricated on a transparent polymer. This approach enabled us to directly modulate neural activity at known locations around micro-ECoG arrays in mice expressing Channelrhodopsin-2. We applied photostimuli varying in time, space and frequency to the cortical surface, and we targeted multiple depths within the cortex using an optical fiber while recording micro-ECoG signals.


RESULTS
Negative potentials of up to 1.5 mV were evoked by photostimuli applied to the entire cortical window, while focally applied photostimuli evoked spatially localized micro-ECoG potentials. Two simultaneously applied focal stimuli could be separated, depending on the distance between them. Photostimuli applied within the cortex with an optical fiber evoked more complex micro-ECoG potentials with multiple positive and negative peaks whose relative amplitudes depended on the depth of the fiber.


CONCLUSIONS
Optogenetic ECoG has potential applications in the study of epilepsy, cortical dynamics, and neuroprostheses.
Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
Thomas J
TJ
Richner
Sanitta
S
Thongpang
Sarah K
SK
Brodnick
Amelia A
AA
Schendel
Ryan W
RW
Falk
Lisa A
LA
Krugner-Higby
Ramin
R
Pashaie
Justin C
JC
Williams
D000818:Animals; D062207:Brain-Computer Interfaces; D002540:Cerebral Cortex / Q000502:physiology*; D000075402:Channelrhodopsins; D020099:Coated Materials, Biocompatible; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods*; D005071:Evoked Potentials / Q000502:physiology; D005336:Fiber Optic Technology; D006801:Humans; D007094:Imides; D007834:Lasers; D051379:Mice; D062308:Optogenetics / Q000379:methods*; D010775:Photic Stimulation; D011108:Polymers; D011474:Prosthesis Design; D012815:Signal Processing, Computer-Assisted; D013238:Stereotaxic Techniques; D014992:Xylenes
D000075402:Channelrhodopsins; D020099:Coated Materials, Biocompatible; D007094:Imides; D011108:Polymers; D014992:Xylenes; C011055:parylene