Abstract
Understanding the neural basis of behaviour requires studying brain activity in behaving subjects using complementary techniques that measure neural responses at multiple spatial scales, and developing computational tools for understanding the mapping between these measurements. Here we report the first results of widefield imaging of genetically encoded calcium indicator (GCaMP6f) signals from V1 of behaving macaques. This technique provides a robust readout of visual population responses at the columnar scale over multiple mm(2) and over several months. To determine the quantitative relation between the widefield GCaMP signals and the locally pooled spiking activity, we developed a computational model that sums the responses of V1 neurons characterized by prior single unit measurements. The measured tuning properties of the GCaMP signals to stimulus contrast, orientation and spatial position closely match the predictions of the model, suggesting that widefield GCaMP signals are linearly related to the summed local spiking activity.
Highlights
Understanding the contribution of a particular cortical area to mental phenomena such as perception necessitates analysis of neural activity across multiple spatial and temporal scales and over broad regions of cortical surface
To advance our understanding of the neural basis of behavior, we need to (i) complement techniques that provide single-neuron access over a limited region with techniques that capture neural population responses over a large region, and (ii) develop computational tools that describe the mapping between neural signals measured using different techniques and combined across different spatial scales
Initial injections were performed with enhanced green fluorescent protein (EGFP) to test recombinant adenoassociated virus serotypes and promoters that have proven effective in the rodent
Summary
Understanding the contribution of a particular cortical area to mental phenomena such as perception necessitates analysis of neural activity across multiple spatial and temporal scales and over broad regions of cortical surface. In primate primary visual cortex (V1), the smallest localized stimulus activates an area of multiple mm (Hubel and Wiesel, 1974; Palmer et al, 2012; Van Essen et al, 1984), a region containing millions of neurons. To advance our understanding of the neural basis of behavior, we need to (i) complement techniques that provide single-neuron access over a limited region with techniques that capture neural population responses over a large region, and (ii) develop computational tools that describe the mapping between neural signals measured using different techniques and combined across different spatial scales. There is a growing need to translate advanced optical-genetic techniques to primates and other higher mammals
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