Traditional visual cortical prosthetics based on electrical stimulation have induced percepts low in spatial resolution and devoid of rich visual features. Here, using pulsed infrared neural stimulation (INS), a method that evokes perceived phosphenes in alert monkeys, we have developed an approach with the submillimeter spatial precision needed for interfacing with cortical columns. We delivered INS through a linear optic fiber array in anesthetized cat visual cortex and monitored effects by optical imaging in contralateral visual cortex. INS modulation of response to ongoing visual oriented gratings produced enhanced responses in orientation-matched domains and reduced response in non-matched domains. This oriented response is a higher order, integrated effect. Controls included dynamically applied speeds, directions and patterns of multipoint stimulation. This provides groundwork for a conceptually and technologically new generation of BMI, one based in the columnar code of visual featural perception.
Significance: Current approaches to stimulating and recording from the brain have combined electrical or optogenetic stimulation with recording approaches, such as two-photon, electrophysiology (EP), and optical intrinsic signal imaging (OISI). However, we lack a label-free, all-optical approach with high spatial and temporal resolution.
Aim: To develop a label-free, all-optical method that simultaneously manipulates and images brain function using pulsed near-infrared light (INS) and functional optical coherence tomography (fOCT), respectively.
Approach: We built a coregistered INS, fOCT, and OISI system. OISI and EP recordings were employed to validate the fOCT signals.
Results: The fOCT signal was reliable and regional, and the area of fOCT signal corresponded with the INS-activated region. The fOCT signal was in synchrony with the INS onset time with a delay of ∼30 ms. The magnitude of fOCT signal exhibited a linear correlation with the INS radiant exposure. The significant correlation between the fOCT signal and INS was further supported by OISI and EP recordings.
Conclusions: The proposed fiber-based, all-optical INS-fOCT method allows simultaneous stimulation and mapping without the risk of interchannel cross-talk and the requirement of contrast injection and viral transfection and offers a deep penetration depth and high resolution.
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