Warren, Scott2017-10-092017-10-092017-06https://hdl.handle.net/11299/190444University of Minnesota Ph.D. dissertation.June 2017. Major: Neuroscience. Advisors: Geoffrey Ghose, Stephen Engel. 1 computer file (PDF); vi, 106 pages.A wide variety of different forms of attention have been described in the human and non-human literature, however the recently developed Input Gain Model of visual attention proposes that a simple neural mechanism, multiplicative gain, may be employed to explain much of the available data on visual attentional modulations. On this basis, we hypothesized that a better explanation for distinct forms of attention may be that this simple attentional mechanism is in fact highly specific: attentional modulations are only present within task-appropriate neurons or neuron groups, and it is the location (and not nature) of these modulations which defines the observer’s current attentive state. We present the results of two orthogonal attention tasks, both targeting distinct but specific and well defined sub-populations of primary visual cortical (V1) neurons. In both experiments we observe that attentional modulations are grossly targeted to neural populations that are selectively tuned for the cue. When humans attend to one orientation, voxels reflecting orientation selective neurons tuned toward that orientation are selectively enhanced. When monkeys were trained to attend to a very small region of space, attention modulated the V1 representation of stimulus elements near that location in space. In both studies, these modulations are predictive of observer behavior, providing evidence that attentional modulation of V1 meaningfully impacts the perceptibility of the attended stimuli. Systematic imprecision in these modulations suggest that attentional modulations of V1 are mediated through corticocortical feedback, hypothetically from secondary visual cortex. This provides a strong constraint for further refinement of general models of attention.enAttentionFlavoproteinfMRIMacaqueV1VisionThesis or Dissertation