Welcome the Hegdé Lab Web Page!

Welcome the Hegdé Lab Web Page! Jay Hegdé, Ph.D.

Brain and Behavior Discovery Institute, Department of Ophthalmology, and Vision Discovery Institute
Medical College of Georgia
Augusta, GA

[For contact information, scroll down to the bottom of this page.]

OUR RESEARCH INTERESTS: VISION AS INFERENCE

In my laboratory, we study how we see. Specifically, we are interested in understanding visual perception as statistical inference.

The rationale behind studying vision as inference is this: The visual world is more complex, ambiguous and noisy than we generally realize. This means that the brain cannot afford to construct an internal replica of the external world we see. Instead, brain has to ‘make do’ with the available ambiguous information. Thus, what we think of seeing is really the brain’s best guess as to what is out there.

Recent studies show that in order to come up with this inference about the world, the brain must evaluate the ambiguous sensory information together with what it knows about the nature of the visual world and about the task at hand. The goal of my laboratory is to study how this decision-making process works.

Visual inference is not a special case scenario, but rather is part and parcel of visual perception under any circumstance. In other words, there is no visual perception without inference.

An obvious illustration of this is 3-D vision. The retinal image is a flat, 2-D image; it contains no unambiguous 3-D information whatsoever. This means that the third dimension, or depth, has to be inferred from the cues to depth (such as stereoscopic disparity, motion, occlusion, etc) implicit in the image. Since each depth cue by itself is ambiguous, the visual system must combine ambiguous information from multiple depth cues to infer depth. Thus, there is no 3-D vision without inference. Given that there are many additional sources of ambiguity in the visual image, there is no vision, 3-D or otherwise, without inference.

Indeed, recent computational and psychophysical studies indicate that studying vision as inference, especially as Bayesian inference, provides a far-reaching framework for understanding not only how we see but, in good measure, how the brain works.

RESEARCH METHODOLOGIES WE USE

We use a variety of advanced research methods, including multi-electrode recording in awake, behaving monkeys, functional magnetic resonance imaging (fMRI) in humans and monkeys, psychophysics in humans and monkeys, and modeling. Thus, my laboratory offers an excellent opportunity to learn a diverse set of advanced research methodologies while addressing many questions in the forefront of Systems Neuroscience.

LABORATORY PERSONNEL
[These web pages are coming soon.]

COLLABORATORS

We are proud to collaborate with (in alphabetical order) Dr. Eugene Bart of Xerox Palo Alto Research Center (Palo Alto, CA), Dr. Mark Brady of North Dakota State University (Fargo, ND), and Dr. Jeffrey Odel of of Columbia University College of Physicians and Surgeons (New York, NY).

AND IF YOU ARE LOOKING TO HIRE.....
In this section, we'll list those folks who have applied to my lab (and/or who have worked in my lab) whom I'd have hired if I had the necessary resources. If you are looking to hire, you really should give these folks a consideration:

Mr. Karin Hauffen, programmer. Proficient in C, C++, Matlab and many other languages. A quick study, and a good guy.
[More names to be added soon.]

Note: We plan to eventually develop this section as a separate webite of its own, where folks in science, especially students and postdocs, can post free ads, notes, commentaries, reviews, etc absolutely free of charge.

RELATED LINKS

We also invite you to check out two of our webpages under construction: Our camouflage challenge webpage features online 'experiments' under development that deal with how we recognize camouflaged objects and how we learn to recognize them.

Our digital embryo webpage describes an interesting class of naturalistic, novel objects that we use in many of our research projects, including our research on camouflage, perceptual learning, object recognition, etc.

Digital embryos were originally developed by Dr. Mark Brady as a graduate student in the laboratory of Dr. Daniel Kersten at the University of Minnesota (Brady and Kersten, 2003). Jay Hegdé, Eugene Bart and Dan Kersten subsequently devised an evolution-based algorithm for creating natualistic categories of these naturalistic objects Hegdé, Bart and Kersten, 2008).

SELECTED PUBLICATIONS
Original Research Papers

Note: Most of the publications that are out in print can downloaded from this page as PDF files.
If you are interested in manuscripts in press, in revision, in review, or in preparation on a specific topic,
please contact me.

Hegdé, J. and Kersten, D. A linke between visual diambiguation and visual memory. Journal of Neurophysiology (In revision).

Hegdé, J. How reliable is pattern adaptation? A modeling study. Journal of Neurophysiology102(4):2245-52 (2009).

Hegdé, J., Bart, E. and Kersten, D. Fragment-based learning of visual object categories. Current Biology 18:597-601 (2008). [Comment in: Vuong, QC. Visual categorization: when categories fall to pieces. Current Biology 18:R427-429 (2008)]

Hegdé, J., Fang, F., Murray, S.O. and Kersten, D. Preferential responses to occluded objects in the human visual cortex. Journal of Vision 8:16.1-16.16 (2008).

Hegdé, J. and Van Essen, D.C. A comparative study of form processing in primate visual areas V4, V2 and V1. Cerebral Cortex 17:1100-1116 (2007). [Cover Article] [Faculty of 1000 selection]

Hegdé, J. and Van Essen, D.C. Temporal dynamics of 2-D and 3-D shape representation in macaque visual area V4. Visual Neuroscience 23:749-763 (2006). [Cover Article]

Hegdé, J. and Van Essen, D.C. Stimulus dependence of disparity coding in primate visual area V4. Journal of Neurophysiology 93:620-626 (2005).

Hegdé, J. and Felleman, D.J. Modeling the observed center-surround summation in macaque visual area V1. Neurocomputing 63:499-525 (2005).

Hegdé, J. and Van Essen, D.C. Role of primate visual area V4 in the processing of 3-D shape characteristics defined by disparity. Journal of Neurophysiology 94:2856-2866 (2005).

Hegdé, J. and Van Essen, D.C. Temporal dynamics of shape representation in macaque visual area V2. Journal of Neurophysiology 92: 3030-3042 (2004).

Hegdé, J., Albright, T.D. and Stoner, G.R. Second-order motion conveys depth order information. Journal of Vision 4:838-842 (2004).

Hegdé, J. and Van Essen, D.C. Strategies of shape representation in macaque visual area V2. Selectivity for complex shapes in primate visual area V2. Visual Neuroscience 20:313-328 (2003). [Cover Article]

Hegdé. J. and Felleman, D.J. How selective are V1 cells for pop-out stimuli? Journal of Neuroscience 23:9968-9980 (2003). [Cover Article]

Hegdé, J. and Van Essen, D.C. Selectivity for complex shapes in primate visual area V2. Journal of Neuroscience 20:RC61-66 (2000).

Hegdé, J. and Felleman, D.J. The popout in some conjunction searches is due to perceptual grouping. NeuroReport 10:143-148 (1998). [Cover Article]

Reviews/Commentaries
Hegdé, J. Overfitting. In: Encyclopedia of Research Design, Salkind, Neil J., ed. Sage Publications, Thousand Oaks, CA. (2009). [Invited article]

Hegdé, J. Decision rule. In: Encyclopedia of Research Design, Salkind, Neil J., ed. Sage Publications, Thousand Oaks, CA. (2009). [Invited article]

Hegdé, J. Time course of visual perception: Coarse-to-fine processing and beyond. Progress in Neurobiology 84:405-439 (2008). [Invited article]

Hegdé, J. Mental time travel sickness and a Bayesian remedy. Behavioral and Brain Sciences 30:323-324 (2007).

Hegdé, J. and Felleman, D. J. Reappraising the functional implications of the primate visual anatomical hierarchy. The Neuroscientist13:416-421 (2007). [Invited article]

Hegdé, J. Search for the neural correlates of perceptual learning. Journal of Neuroscience 26:8877-8878 (2006).

Hegdé, J. and Johnson, N. A. Folk psychology meets folk Darwinism. Behavioral and Brain Sciences 29:476-477 (2006).

Boynton, G. and Hegdé, J. Visual cortex: The continuing puzzle of area V2. Current Biology 14:R523-R524 (2004). [Invited article]

Abstracts
Kromrey, S.A., Howard, S.M., Hegdé, J. Neural Mechanisms of Perception of Depth-order from Motion: A Human fMRI Study. Vision Sciences Society (Submitted).

Epting, A. and Hegdé, J. The Role of Temporal Priors in the Perception of Depth-Order from Motion: A Priming Study. Vision Sciences Society (Submitted).

Chen, X. and Hegdé, J. Implicit learning of background texture while learning to break camouflage. Vision Sciences Society (Submitted).

Kromrey, S.A., Howard, S.M., Hegdé, J. Accretion-deletion cue is insufficient for determining depth-order from motion. Society for Neuroscience Abstracts 380.3 (2009).

Howard, S.M., Kromrey, S.A., Hegdé, J. Role of accretion-deletion cue in determining depth-order from motion. GA/SC Neuroscience Consortium Meeting Abstracts, Athens, GA. (2009).

Bart, E., Hegdé, J. and Kersten, D. Fragment-based learning of visual categories. Cosyne p. 121. (2008).

Hegdé, J., Thompson, S. K. and Kersten, D. Identifying faces in two-tone ('Mooney') images: A psychophysical and fMRI study. Journal of Vision 7:624 (2007).

Hegdé, J., Thompson, S.K. and Kersten, D. Psychophysical and fMRI studies of the role of prior knowledge in visual perception. Vision Sciences Society Abstracts/Journal of Vision 6:677a (2006).

Thompson, S., Hegdé, J. and Kersten, D. Learning novel objects in camouflage. Visual Learning and Recognition Workshop Institute of Mathematics and Its Applications, University of Minnesota, Minneapolis, MN (2006).

Hegdé, J., Thompson, S. and Kersten, D. Object recognition in cluttered visual scenes: Is it better to learn objects in the presence or the absence of clutter? Society for Neuroscience Abstracts 438.19 (2006).

Hegdé, J., Fang, F., Murray, S.O. and Kersten, D. Neural mechanisms of interpretation of occluded objects: A human fMRI study. Society for Neuroscience Abstracts 31:768.12 (2005).

Hegdé, J. and Albright, T.D. Is selective spatial frequency adaptation diagnostic of neuronal mechanisms of spatial frequency processing? A modeling study. Society for Neuroscience Abstracts 30:986.20 (2004).

Hegdé, J., Albright, T.D. and Stoner G.R. Contextual effects of binocular depth cues and shadow-based depth cues on motion interpretation. Journal of Vision 3:804a (2003).

Stoner, G.R., Albright, T.D. and Hegdé, J. Depth order perception in first- and second-order motion stimuli. Journal of Vision 3:799a (2003).

Anzai, A., Van Essen, D.C., Peng, X. and Hegdé, J. Receptive field structure of monkey V2 neurons for encoding orientation contrast. Journal of Vision 2:221a (2002).

Hegdé, J. and Van Essen, D.C. Selectivity for 3-D shape characteristics defined by stereoscopic disparity in macaque visual area V4. Society for Neuroscience Abstracts 27:165.7 (2001).

Hegdé, J. and Felleman, D.J. Linearity of center-surround summation of low contrast stimuli in primate visual area V1. Society of Neuroscience Abstracts 26:141 (2000).

Hegdé, J. and Van Essen, D.C. Selectivity for complex forms in primate visual area V1. Society for Neuroscience Abstracts 25:1548 (1999).

Hegdé, J. and Van Essen, D.C. Population analyses of selectivity for contour and grating stimuli in macaque visual area V2. Society for Neuroscience Abstracts 24:1506 (1998).

Hegdé, J. and Van Essen, D.C. Selectivity for Contours in visual area V2. Investigative Ophthalmology and Visual Science 38:4492 (1997).

Hegdé, J. and Van Essen, D.C. Selectivity for non-Cartesian and conventional gratings in visual area V2. Society for Neuroscience Abstracts 23:1395 (1997).

Hegdé, J. and Felleman, D.J. Parallel processing or perceptual grouping? Society of Neuroscience Abstract 21:512 (1996).

Hegdé, J. and Felleman, D.J. Neurons in area V1 respond similarly to pop-out and non-popout stimuli. Investigative Ophthalmology and Visual Science 37:S484 (1996).

Hegdé, J. and Felleman, D.J. Distribution of parvalbumin and SMI32 immunoreactivities in extrastriate visual cortex of the macaque. Society of Neuroscience Abstract 20:428 (1995).

Hegdé, J., Xiao, Y., Emery, J.M. and Felleman, D.J. Effects of adult onset of aphakia on the functional architecture of macaque LGN and V1. Investigative Ophthalmology and Visual Science 35:2411 (1994).

CONTACT INFO FOR JAY HEGDÉ:
MAILING ADDRESS:
Brain and Behavior Discovery Institute
CB-2803
Medical College of Georgia
1120 15th Street
Augusta, GA 30912-2697

OFFICE:
Research and Education Building (aka CB Building), Room 1601
Medical College of Georgia
Augusta, GA 30912-2697

jay AT hegde.us
jhegde AT mcg.edu
Telephone: (706)721-5129 (office)
Fax: (866)230-0486 / (706)721-3829

LABORATORY:
Human Vision Research:
Research and Education Building (aka CB Building), Room 2407. Telephone: (706)721-1205 and (706)721-1821.

All Other Research:
Research and Education Building (aka CB Building), Room 1623. Telephone: (706)721-0000 (That's right, four zeros. AT&T loves us!)
Hamilton Wing (aka CL Building), Room 3142. Telephone: (706)721-5781

[A map of the MCG campus, with arrows pointing to our lab, offices, and the nearest visitor's parking lot, can be downloaded here.]