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People
Biosketch - PDF :: Search PubMed
Biosketch - PDF My research examines the neural correlates of face and object perception using a variety of techniques, including magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI). Using MEG, I have quantified the properties of the M170 response, an early "face-selective" component, both in normal adults and in developmental prosopagnosics, individuals with behavioral impairments in face recognition (in collaboration with Dr. Brad Duchaine). More recently, in my work with Dr. Geoffrey Aguirre, I have been using fMRI to explore the nature of representations within "face- selective" regions of interest (ROIs). Together, the results from these two lines of inquiry suggest that the neural encoding of faces includes not only global or holistic information about the entire face, as has been previously proposed, but also representation of individual face features or parts.
Biosketch - PDF Most of my training had been focused on assessing the effects of visual deprivation early in life by performing animal psychophysical experiments in attempts to re-create the ophthalmologic disease often visited upon human patients in childhood. During my masters studies, I showed that hamsters with experimentally-induced retinal outputs to the auditory cortex could see [PNAS (2001), 98, 11068-11073]. Additionally, during my doctoral studies, I investigated the spatial localization abilities of cats rendered amblyopic by surgically created strabismus or by imposition of various regimens of monocular deprivation. Similarly to human amblyopes, the spatial localization deficits in the amblyopic animals increased with the spatial scale of the stimuli. Moreover, these deficits could not be explained by a loss of contrast sensitivity in the deprived eye [Vision Research (2005), 45, 975-989]. In Dr. Aguirre's laboratory, I intend to pursue the same line of investigation but employing a novel experimental approach and a different clinical population. I will be investigating the visual abilities of a canine animal model of Leber's Congenital Amaurosis (LCA), a congenital retinal degeneration disorder. Using functional magnetic resonance imaging (fMRI), I will measure the cortical response functions to variation of stimulus features, and then determine if previously blind animals recover normal responses for these measures following genetic therapy. Further studies will examine the effects of age of treatment in order to optimize visual recovery.
I am broadly interested in the neural bases of object and concept similarity spaces. Currently, I am exploring the focal and distributed representations of visual similarity of parameterized shape spaces in human object recognition cortex.
I am involved in a variety of facial perception studies including the development of a neuropsychological battery of face perception and many other fMRI and behavioral studies.
I am interested in characterizing the organization of the visual system of patients with occipital cortex damage, and in establishing if remapping of retinotopic organization can occur visual cortex lesions. I have been studying the residual visual functioning, both behaviorally and on a neural level (using fMRI), of a patient with Blindsight, as well as the representation of the ipsilateral visual field in healthy control subjects. In the long run, I hope to examine ways of improving vision after stroke (eg, through perceptual training), and the neural basis of recovery.
I have a blossoming interest in higher-order visual processing. Currently, I am using functional imaging to investigating the mechanisms of cross-modal plasticity of the visual cortex in early-blind subjects. Specifically, I am assessing the relative contribution of the "visual" cortex to a spoken-language semantic categorization task. I collaborate on another project studying a subject with intact motion perception within a scotoma due to a discrete lesion of the primary visual cortex. At the completion of residency training, I will pursue a clinical neuro-ophthalmology fellowship at Penn, followed by a two-year cognitive research fellowship in Dr. Aguirre's lab.
My research involves the application of computational methods to mimic and understand visual perception and processing. I am particularly interested in describing a perceptual space of images using multidimensional scaling (MDS) and other models on reaction time data. My current projects are focused on the perception of textures and the interdependency between the many quantifiable properties of textures. Within these projects, I have also become interested in algorithms for texture generation, replication, and morphing; specifically reaction diffusion and steerable pyramids. My previous work has included the implementation of support vector machines (SVM) to fMRI to discriminate which face a subject is viewing.
Students
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Geoffrey Karl Aguirre, MD, PhD
Alison Harris, PhD
Guy Gingras, PhD
Daniel Drucker
Amy Thomas
Petya Radoeva
Sashank Prasad, MD
Wesley Kerr, MD
Ben Tseng, MD
Philip Cook, MD