Senior Vice Chancellor's Research Seminar

Topic Overview:

Cohen and colleagues study how visual information is encoded in the brain and used to guide behavior. One of their strategies is to use visual attention, which improves perception and also affects the activity of neurons in the visual cortex, to study the neural computations underlying visual perception. Several recent studies showed that, in addition to enhancing the responses of individual neurons, attention decreases correlations between fluctuations in the responses of pairs of neurons (termed “spike count correlation”). Spike count correlations can provide important information about neuronal mechanisms because they might affect the amount of information encoded by a group of neurons and they can constrain models of the underlying neuronal circuits.

Cohen will describe a series of studies exploring what spike count correlations can tell us about how attention affects populations of neurons within and across cortical areas. In one experiment, she and her lab members investigated whether attention–related increases in rate and decreases in correlation are fixed signatures of a single underlying mechanism or whether attention might be associated with either increases or decreases in correlation under different task demands. They showed that attention can flexibly increase or decrease correlations, depending on the role the neurons play in the task. A second set of experiments used attention to probe how visual information is combined across cortical areas. They found that attention had opposite effects on correlations within and between cortical areas, suggesting that attention may affect the transmission of sensory information between cortical areas. Consistent with this idea, they found that attention increased the extent to which electrical microstimulation in one cortical area modulated the firing rates of neurons in a downstream area. Together, their results are consistent with the hypothesis that attention affects both the way sensory information is encoded within a cortical area and the extent to which that information is communicated to downstream areas.









		Topic Overview: Cohen and colleagues study how visual information is encoded in the brain and used to guide behavior. One of their strategies is to use visual attention, which improves perception and also affects the activity of neurons in the visual cortex, to study the neural computations underlying visual perception. Several recent studies showed that, in addition to enhancing the responses of individual neurons, attention decreases correlations between fluctuations in the responses of pairs of neurons (termed “spike count correlation”). Spike count correlations can provide important information about neuronal mechanisms because they might affect the amount of information encoded by a group of neurons and they can constrain models of the underlying neuronal circuits. Cohen will describe a series of studies exploring what spike count correlations can tell us about how attention affects populations of neurons within and across cortical areas. In one experiment, she and her lab members investigated whether attention–related increases in rate and decreases in correlation are fixed signatures of a single underlying mechanism or whether attention might be associated with either increases or decreases in correlation under different task demands. They showed that attention can flexibly increase or decrease correlations, depending on the role the neurons play in the task. A second set of experiments used attention to probe how visual information is combined across cortical areas. They found that attention had opposite effects on correlations within and between cortical areas, suggesting that attention may affect the transmission of sensory information between cortical areas. Consistent with this idea, they found that attention increased the extent to which electrical microstimulation in one cortical area modulated the firing rates of neurons in a downstream area. Together, their results are consistent with the hypothesis that attention affects both the way sensory information is encoded within a cortical area and the extent to which that information is communicated to downstream areas.