AUTHOR=Borji Ali , Itti Laurent 

TITLE=Optimal attentional modulation of a neural population

JOURNAL=Frontiers in Computational Neuroscience

VOLUME=Volume 8 - 2014

YEAR=2014

URL=https://www.frontiersin.org/journals/computational-neuroscience/articles/10.3389/fncom.2014.00034

DOI=10.3389/fncom.2014.00034

ISSN=1662-5188

ABSTRACT=Top-down attention has often been separately studied in the contexts of either<br/>optimal population coding or biasing of visual search. Yet, both are intimately<br/>linked, as they entail optimally modulating sensory variables in neural populations<br/>according to top-down goals. Designing experiments to probe top-down attentional<br/>modulation is difficult because non-linear population dynamics are hard<br/>to predict in the absence of a concise theoretical framework. Here, we describe<br/>a unified framework that encompasses both contexts. Our work sheds light onto<br/>the ongoing debate on whether attention modulates neural response gain, tuning<br/>width, and/or preferred feature. We evaluate the framework by conducting simulations<br/>for two tasks: 1) classification (discrimination) of two stimuli sa and sb<br/>and 2) searching for a target T among distractors D. Results demonstrate that all<br/>of gain, tuning, and preferred feature modulation happen to different extents, depending<br/>on stimulus conditions and task demands. The theoretical analysis shows<br/>that task difficulty (linked to difference D between sa and sb, or T and D) is a<br/>crucial factor in optimal modulation, with different effects in discrimination vs.<br/>search. Further, our framework allows us to quantify the relative utility of neural<br/>parameters. In easy tasks (when D is large compared to the density of the neural<br/>population), modulating gains and preferred features is sufficient to yield nearly<br/>optimal performance; however, in difficult tasks (smaller D), modulating tuning<br/>width becomes necessary to improve performance. This suggests that the conflicting<br/>reports from different experimental studies may be due to differences in<br/>tasks and in their difficulties. We further propose future electrophysiology experiments<br/>to observe different types of attentional modulation in a same neuron.