A central observation that has driven modern thinking about vision is that the visual system decomposes stimuli into their constituent features, represented by neurons with different feature selectivities. How the signals carried by these feature selective neurons are integrated into coherent object representations is unknown and stands as one of the central unsolved questions in neurobiology. Insight into the mechanisms that solve this problem can be gained by carefully analyzing the temporal properties of perceptual integration at the psychophysical and neuronal levels. We will pursue this strategy, focusing on a simple and well-defined case of feature integration: the conjoining of two of the most basic and well studied features in vision: color and orientation. The central objective of the current proposal is to understand how the visual system conjoins these features. This objective will be met in the following specific aims.
Aim 1. Compare the temporal resolution of the visual system for color, orientation and conjunctions of these two features, at the perceptual level and in BOLD in humans, and at the neuronal level in monkeys.
Aim 2. Characterize the temporal dynamics of tuning for color and orientation, their dependence on luminance contrast, and quantify any changes in these properties under naturalistic visual stimulation.
Aim 3. Test whether spatial attention plays a role in the integration of color and orientation. Relevance: Our current lack of knowledge about the mechanisms of feature integration represents a significant gap in our understanding of the pathology of disorders in which the perception of objects is impaired, such as simultagnosia, prosopagnosia, integrative visual agnosia, Balint's syndrome, and object- centered impairments associated with neglect. Filling this gap will provide understanding that will help in the interpretation and treatment of these and related disorders. The proposed experiments will close this gap by (1) characterizing the temporal resolution of the neural mechanisms that mediate feature integration, (2) developing and testing mathematically rigorous models of the neural computations that mediate a simple and well defined form of feature integration, and (3) determining whether or not attention plays a role in the formation of feature conjunctions.

National Institute of Health (NIH)
National Eye Institute (NEI)
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Central Visual Processing Study Section (CVP)
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Steinmetz, Michael A
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Salk Institute for Biological Studies
La Jolla
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Mitchell, Jude F; Boisvert, Chantal J; Reuter, Jon D et al. (2014) Correction of refractive errors in rhesus macaques (Macaca mulatta) involved in visual research. Comp Med 64:300-8
Mitchell, Jude F; Boisvert, Chantal J; Reuter, Jon D et al. (2014) Correction of refractive errors in rhesus macaques (Macaca mulatta) involved in visual research. Comp Med 64:300-8
Nandy, Anirvan S; Sharpee, Tatyana O; Reynolds, John H et al. (2013) The fine structure of shape tuning in area V4. Neuron 78:1102-15
Anderson, Emily B; Mitchell, Jude F; Reynolds, John H (2013) Attention-dependent reductions in burstiness and action-potential height in macaque area V4. Nat Neurosci 16:1125-31
Sundberg, Kristy A; Mitchell, Jude F; Gawne, Timothy J et al. (2012) Attention influences single unit and local field potential response latencies in visual cortical area V4. J Neurosci 32:16040-50
Fallah, Mazyar; Reynolds, John H (2012) Contrast dependence of smooth pursuit eye movements following a saccade to superimposed targets. PLoS One 7:e37888
Anderson, Emily B; Mitchell, Jude F; Reynolds, John H (2011) Attentional modulation of firing rate varies with burstiness across putative pyramidal neurons in macaque visual area V4. J Neurosci 31:10983-92
Ciaramitaro, Vivian M; Mitchell, Jude F; Stoner, Gene R et al. (2011) Object-based attention to one of two superimposed surfaces alters responses in human early visual cortex. J Neurophysiol 105:1258-65
Khoe, Wayne; Mitchell, Jude F; Reynolds, John H et al. (2008) ERP evidence that surface-based attention biases interocular competition during rivalry. J Vis 8:18.1-11
Bodelon, Clara; Fallah, Mazyar; Reynolds, John H (2007) Temporal resolution for the perception of features and conjunctions. J Neurosci 27:725-30

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