Study of single and multidigit activation in monkey SI using voltage sensitive dye imaging

Roe AW, Winberry J, Friedman RM (2017) Neurophotonics, 4(3):031219.

Study of single and multidigit activation in monkey SI using voltage sensitive dye imaging.pdf

Infrared neural stimulation: a new stimulation tool for CNS applications

Chernov M and Roe AW (2014) Neurophotonics, 1(1):011011.


Infrared neural stimulation a new stimulation tool for CNS applications.pdf

Optical imaging of cortical networks via intracortical microstimulation

Understanding cortical organization is key to understanding brain function. Distinct neural networks underlie the functional organization of the cerebral cortex; however, little is known about how different nodes in the cortical network interact during perceptual processing and motor behavior. To study cortical network function we examined whether the optical imaging of intrinsic signals (OIS) reveals the functional patterns of activity evoked by electrical cortical microstimulation. We examined the effects of current amplitude, train duration, and depth of cortical stimulation on the hemodynamic response to electrical microstimulation (250-Hz train, 0.4-ms pulse duration) in anesthetized New World monkey somatosensory cortex. Electrical stimulation elicited a restricted cortical response that varied according to stimulation parameters and electrode depth. Higher currents of stimulation recruited more areas of cortex than smaller currents. The largest cortical responses were seen when stimulation was delivered around cortical layer 4. Distinct local patches of activation, highly suggestive of local projections, around the site of stimulation were observed at different depths of stimulation. Thus we find that specific electrical stimulation parameters can elicit activation of single cortical columns and their associated columnar networks, reminiscent of anatomically labeled networks. This novel functional tract tracing method will open new avenues for investigating relationships of local cortical organization.

Brock AA, Friedman RM, Fan RH, Roe AW (2013) J Neurophysiol, 110:2670-2678.

Optical imaging of cortical networks via intracortical microstimulation.pdf

Infrared neural stimulation of primary visual cortex in non-human primates

Infrared neural stimulation (INS) is an alternative neurostimulation modality that uses pulsed infrared light to evoke spatially precise neural activity that does not require direct contact with neural tissue. With these advantages INS has the potential to increase our understanding of specific neural pathways and impact current diagnostic and therapeutic clinical applications. In order to develop this technique, we investigate the feasibility of INS (λ = 1.875 μm, fiber diameter = 100–400 μm) to activate and modulate neural activity in primary visual cortex (V1) of Macaque monkeys. Infrared neural stimulation was found to evoke localized neural responses as evidenced by both electrophysiology and intrinsic signal optical imaging (OIS). Single unit recordings acquired during INS indicated statistically significant increases in neuron firing rates that demonstrate INS evoked excitatory neural activity. Consistent with this, INS stimulation led to focal intensity-dependent reflectance changes recorded with OIS. We also asked whether INS is capable of stimulating functionally specific domains in visual cortex and of modulating visually evoked activity in visual cortex. We found that application of INS via 100 μm or 200 μm fiber optics produced enhancement of visually evoked OIS response confined to the eye column where INS was applied and relative suppression of the other eye column. Stimulating the cortex with a 400 μm fiber, exceeding the ocular dominance width, led to relative suppression, consistent with involvement of inhibitory surrounds. This study is the first to demonstrate that INS can be used to either enhance or diminish visual cortical response and that this can be done in a functional domain specific manner. INS thus holds great potential for use as a safe, non-contact, focally specific brain stimulation technology in primate brains.

Cayce J, Friedman RM, Jansen D, Mahadevan-Jansen A, Roe AW (2014) Neuroimage, 84:181-190.

Infrared neural stimulation of primary visual cortex in non-human primates.pdf

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