This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will support a twenty-four-month research fellowship by Dr. Neel T. Dhruv to work with Dr. Matteo Carandini at University College London, in the UK.
Nerve cells in the brain receive information from an extensive network of connections. For a given cell, these connections could originate from distant parts of the brain as well as from within a neuron?s local neighborhood. For example, neurons in primary visual cortex (V1) receive feed-forward inputs from thalamus and lateral connections from within V1. However, the relative influence of these two inputs in driving V1 responses remains unknown and is the subject of much current debate. In this project, the PI will investigate how the relative contributions of feed-forward connections and lateral connections shape the responses and contribute to the variability of neurons in V1. He hypothesizes that V1 can operate in two regimes ? one that is dominated by feed-forward connections (a ?receptive-field? regime) and another that is dominated by cortical connections (a ?connection-field? regime). Furthermore, he hypothesizes that the dominant mode is determined by a number of intrinsic factors, including cell type, laminar location and stimulus attributes such as contrast. He will perform experiments in anesthetized mice by combining single-unit electrophysiology with optical imaging (using voltage-sensitive dyes) or ?electrical imaging? (with multi-electrode arrays). The stimuli are random sequences of gratings that are varied in phase, orientation and spatial frequency with each stimulus ensemble presented at multiple contrast levels. He thus can simultaneously measure the spike train of a single neuron and the activity of its cortical neighborhood, and to relate both of these to the visual stimulus history.
The PI?s experiments will help to reveal how different inputs are weighted by V1 neurons and how this might differ for different cell classes or for cells in different lamina. In addition, this research will serve to advance the mouse as an experimental model for vision research, thereby reducing the future need for primate-based research.
