Unit on Neurons, Circuits and Behavior

National Institute Of Mental Health

Investigators

Linked publications & trials

Abstract

During the past year we have published our methodological advances in developing chronically implantable LED arrays for high throughput optogenetic perturbation of the cortex in large brains. On four project fronts, we have finished the data collection phase and we are at different stages of preparation for publication. Following, I briefly review each one of these studies: 1. Stimulus dependence of the perceptual events induced by stimulation of high-level visual cortex: This study is the corner stone of our research program. Here, we showed that behavioral detection of cortical stimulation highly depends on the visual characteristics of the visual stimuli entering the visual system at the time of stimulation. This is very important as the interaction of brain stimulation with the visual stimulus provides a unique opportunity; one can perturb the visual stimulus in order to understand the characteristics of the perception induced by local stimulation in the cortex (inferior temporal cortex in this case). The paper is written and currently under review. 2. The magnitude of the perceptual events induced by brain stimulation depend on the size of the viewed objects: This study is a sequel to a very important observation established in the first study, that the size of the viewed objects determines behavioral detectability of cortical stimulation. In simple words, detection of cortical stimulation is much easier when looking at a large visual stimulus comparing to small stimuli. This counter-intuitive finding is reported in a separate paper, currently under review. 3. Perceptography: We have established a novel approach to the study of visual perception following brain stimulation. We have combined high-throughput optogenetic brain stimulation (via chronically implanted LED arrays) with machine learning methods in order to evolve specific image perturbations that would be mistakenly taken by the animal as the state of brain stimulation. We call such perturbed images perceptograms as the state of looking at them is indistinguishable for the animals from the state of being cortically stimulated. Perceptograms provide for the first time, direct pictorial evidence of the shape and quality of the perceptual hallucinations induced by brain stimulation in high level visual areas. We have prepared the manuscript of this study and we are ready to submit it for review. 4. The effect of cortical perturbation on free eye movements: We have finished data collection of a large study, measuring the effect of artificial silencing of face-selective neurons in the inferior temporal cortex on free eye movements. The pattern of eye movements contains rich information about the viewed objects. In this study we have shown that the brain circuits involved in object recognition (e.g., face selective neurons) are part of the causal chain that determines the pattern of eye movements while looking at objects. We have finished data collection and analysis for this study and are currently in the process of writing the manuscript. In summary, during the last year we made significant progress in establishing quantitative and causal links between neural activity in the inferior temporal cortex (high level visual area associated with object recognition) and different measures of visual perception.