Electrical stimulation to control feedback modulation of perception

SUMMARY Visual perception is a confluence of visual input and attentional state. How visual inputs are processed and represented in human visual cortex is being captured with increasing accuracy in the field. However, a critical gap in our understanding is how top-down inputs from higher order areas influence and sculpt sensory processing—especially an understanding grounded in direct causal manipulations. The long-term goal of the proposed research is to develop causal perturbation methods that modulate visual processing in ways that mimic attentional processes. To achieve this goal, we will use electrical stimulation to test, refine, and extend a quantitative model of feedback information flow to the ventral temporal cortex (VTC). Our research leverages a recent clinical shift in epilepsy surgery from brain surface recordings with electrocorticography to stereo-electroencephalographic (sEEG) depth electrodes: sEEG provides unique opportunities to measure VTC and electrically stimulate feedback projections from gyral and sulcal parietal, frontal and anterior temporal regions as well as the white matter pathways that connect these areas to VTC. In Aim 1, we will determine how stimulating these different feedback locations affects neuronal activity in VTC and simulate VTC signals in a model of a cortical column. VTC electrodes will be localized functionally with a scene perception task and structural connections will be identified from preoperative diffusion MRI measurements on Mayo Clinic’s novel compact 3T scanner with high performance gradients and distortion free imaging. In Aim 2, we will determine the optimal stimulation frequencies for feedback pathways to VTC. Electrodes in feedback pathways will be stimulated with different temporal frequencies and measurements in VTC will be used to characterize optimal response frequencies. In Aim 3, we will test predictions of a previously proposed model of feedforward drive and feedback modulation in VTC. We will present visual scenes while delivering electrical stimulation of feedback pathways and measure changes in sEEG neural responses and behavioral reaction times. This combination of electrical stimulation and visual perception allows us to test and refine an extant model of how interactions between VTC and the intraparietal sulcus affect visual processing and contribute to visual perception. Overall, this multidisciplinary proposal will deliver a set of empirical measurements and models that describe the causal influence of feedback pathways on human VTC. These studies will provide the groundwork for future research to design perturbation based strategies that mimic human attentional conditions.