Early visual areas encode detailed visual input through feature-based coding, thereby providing an ecient code for representing ne-grained dierences between visual stimuli. For example, neurons in V1 respond selectively to particular retinotopic locations, orientations, spatial frequencies, colors, motion directions, and binocular dis- parities. We have learned a great deal regarding these feature-tuning properties from neurophysiology studies. More recently, fMRI studies utilizing pattern classication techniques have allowed for the examination of feature- tuning properties in the human visual system. In these studies, researchers train a classier on fMRI activity to discriminate between activity patterns associated with a small set of stimulus conditions, and discrimination accuracy provides a measure of how much information those areas convey about the stimulus conditions. For example, it is possible to discern which of eight orientations a participant is viewing from fMRI activity patterns in V1, and similar approaches have been successful in identifying other feature-based response patterns. However, the stimulus dimensions of interest, such as orientation, motion or color are typically continuous variables that can take on any value within some range. Moreover, the cortical response patterns associated with these stimulus variables likely vary on a continuum. The goal of this proposal is to develop methods that account for relationships between fMRI activation patterns and the actual value of a feature experienced on some dimension, rather than discriminating between a small set of values. The existence of such continuous decoding methods will provide for a far richer set of experimental paradigms than are currently possible, allowing for novel investigations into how features are represented in visual cortex. The goal of Aim 1 is to use continuous decoding to extract ne-grained information about orientation-selective responses from the human visual cortex. The goal of Aim 2 is to inves- tigate the relationship between these orientation-selective responses and perceptions of orientation by applying continuous decoding during experiences of visual illusions. The goal of Aim 3 is to study relationships between behavioral performance on a working memory task and cortical representations of the remembered features in the absence of visual stimulation. The overall objective of this fellowship is to train the applicant in the use o fMRI, with an emphasis on decoding methods. In addition, the applicant will be trained in the eld of vision science through directed reading, weekly seminars, and course work taught by faculty in the Vanderbilt Vision Research Center. This training will make possible the applicant's long-term goal of becoming an independent researcher, developing novel analytic techniques for functional imaging data and using them to further our understanding of the neural bases of visual perception and higher-order cognition.
The goal of this research training plan is to develop and apply novel methods for studying relationships between visual feature perception and brain activity. Such advancements are critical for understanding how processes such as vision and working memory depend on the central nervous system, and how these functions may be impaired by disease, aging, or neurological disorders.
|Pratte, Michael S; Tong, Frank (2014) Spatial specificity of working memory representations in the early visual cortex. J Vis 14:22|
|Lorenc, Elizabeth S; Pratte, Michael S; Angeloni, Christopher F et al. (2014) Expertise for upright faces improves the precision but not the capacity of visual working memory. Atten Percept Psychophys 76:1975-84|
|Pratte, Michael S; Ling, Sam; Swisher, Jascha D et al. (2013) How attention extracts objects from noise. J Neurophysiol 110:1346-56|