New methods devised specify the size and color of the spots monkeys see when striate cortex (area V1) is electrically stimulated

Abstract

Creating a prosthetic device for the blind is a central future task. Our research examines the feasibility of producing a prosthetic device based on electrical stimulation of primary visual cortex (area V1), an area that remains intact for many years after loss of vision attributable to damage to the eyes. As an initial step in this effort, we believe that the research should be carried out in animals, as it has been in the creation of the highly successful cochlear implant. We chose the rhesus monkey, whose visual system is similar to that of man. We trained monkeys on two tasks to assess the size, contrast, and color of the percepts created when single sites in area V1 are stimulated through microelectrodes. Here, we report that electrical stimulation within the central 5°of the visual field representation creates a small spot that is between 9 and 26 min of arc in diameter and has a contrast ranging between 2.6% and 10%. The dot generated by the stimulation in the majority of cases was darker than the background viewed by the animal and was composed of a variety of low-contrast colors. These findings can be used as inputs to models of electrical stimulation in area V1. On the basis of these findings, we derive what kinds of images would be expected when implanted arrays of electrodes are stimulated through a camera attached to the head whose images are converted into electrical stimulation using appropriate algorithms. electrical brain stimulation | prosthetics | perception

Microstimulation in the primary visual cortex: activity patterns and their relation to visual responses and evoked saccades

“…ICMS and small visual stimuli activated V1 region extending over tens of mm 2 and in both cases we observed lateral propagation of neural activation, suggesting the involvement of horizontal connections (Fehérvári et al, 2015;Slovin et al, 2002). Interestingly, it was previously reported that ICMS stimulation in V1 of NHPs within the central visual field generates the perception of small phosphenes with an estimated size of 0.17-0.5 o in diameter (Schiller et al 2011). These values are in accordance with our neurophysiological results that the spatial spread of electrically evoked activity is within the range or smaller than the area activated by a visual stimulus size of 0.5 o .…”

“…The ICMS parameters we used ( Fig. 1B middle; see Methods) were previously shown to be highly effective in evoking neural activity in visual cortices as well as in generation of saccades directed to the RF of the stimulated neurons and affect behavioral responses or visual perception (Bradley et al 2005;Davis et al 2012;Schiller et al 2011). We then used VSDI to measure and characterize the ICMS or visually ( Fig.…”

Restoring the sense of touch with a prosthetic hand through a brain interface

“…brain-machine interface | brain-computer interface | macaque A lthough it has been shown that percepts can be elicited with intracortical microstimulation (ICMS) of primary somatosensory cortex (S1) (1-7), a major challenge in developing approaches to convey sensory feedback using ICMS in animal models is to assay the evoked sensations (8). One way to circumvent this obstacle is to train animals to discriminate sensory stimuli along a dimension of interest, and then to assess whether the animals can perform the task when physical stimuli are replaced with ICMS (2,3).…”

Optical imaging of cortical networks via intracortical microstimulation

“…However, the fact that we observe different effects across layers (different magnitudes of response both at the site of stimulation and in local patches away from the stimulation site) suggests that there is some laminar specificity with respect to electrical microstimulation. This could be attributed to many aspects of laminar specificity, including differential cytoarchitecture or myeloarchitecture (Brodmann 1909;Rockel et al 1980), different laminar compositions that exhibit differential sensitivities to electrical stimulation (Histed et al 2009;Schiller et al 2011), and different tangential laminar circuitries (Callaway 1998;Sincich and Blasdel 2001). As well, there are documented laminar differences in energy demands.…”