SUNY Upstate Visiting Lecture Series

Daniel Y Tso, Ph.D.

Associate Professor, Neurosurgery
Ph.D.: 1987, Harvard Medical School
Postdoctoral Fellow: Rockefeller University

4111 Institute For Human Performance
Upstate Medical University
750 East Adams Street
Syracuse, NY 13210
(315) 464-5531

Lab/Professional Web Site

Research Program and Department Affiliations

Biomedical Sciences Program
Neuroscience Program
Neuroscience and Physiology
Neurosurgery
Ophthalmology

Research Interests

Neuronal mechanisms of visual perception, studied through physiological, anatomical and functional imaging techniques.

Cortical Machinery for Visual Perception

Broadly stated, our long term research interests are the neuronal mechanisms of information processing and visual perception. One approach to these goals that we have used is to investigate in detail the functional organization of the visual cortex and the relationship between receptive field properties of cortical neurons and the patterns of connectivity between these groups of neurons, both static and dynamic. Towards this end, our lab has sought to combine conventional anatomical and electrophysiological techniques with novel methods such as cross-correlation analysis and optical imaging. The studies of functional organization in visual cortex previously depended heavily on extensive single unit recordings, but now has been supplemented and greatly facilitated by the new technique of optical imaging. The studies of neuronal connectivity have employed both standard anatomical tracing methods and the physiological technique of cross-correlation analysis.

We plan to continue this line of work, with emphasis on investigating the processing of color information in visual cortex, and its interactions with the processing of other visual submodalities, such as form, motion and depth. Optical imaging is being used to localize the regions involved in color processing which are studied in greater detail with single unit recordings. Cross-correlation analysis as well as tracer injections are used to study the connectivity of these cells. One important theme concerns how groups of neurons cooperate to build increasingly sophisticated receptive field properties for extracting higher level information from more basic input. Our cross-correlation studies have already uncovered some general rules of cortical functional connectivity and these studies are being expanded to examine the influence of visual and, later, behavioral context on effective cortical connectivity.

A second new research direction is to examine the influence of behavior on the overall patterns of dynamic connectivity in the visual cortex. Of special interest to me are the characteristic temporal and spatial patterns of activity among neurons cooperating during a specific visual task. We have begun to probe these issues using the awake, behaving primate preparation, combined with optical imaging and electrophysiology. The information gathered from these studies should help expand our understanding of the neuronal computation and circuitry underlying visual perception and the influences of attention and learning. One possibility is that behavioral training and attention may alter the synaptic strengths of connections in the cortex and that these changes may be monitored by either optical imaging or cross-correlation analysis. The development of the techniques for optical imaging in chronic preparations should lead to many applications in the study of cortical plasticity and development.

We have continued to push towards a thorough understanding of the functional organization of and interactions between the visual areas V1, V2 and V4, in part because these are the initial stages of the cortical processing of visual information, and in part, as a model to better understand how several cortical areas cooperate, whether hierarchically or in parallel, to yield perception and ultimately cognitive function. Our studies of V1 and V2, combined with the work of other investigators in the field have led to significant recent advances in our knowledge of the function and structure of these areas. In contrast, our understand of area V4 is meager and we are placing an increasing effort to elucidate its role in visual perception, using the methods described above. Thus in sum, a major long-term goal is to gather sufficient data on the functional organization, response properties and functional connectivity of neurons in V1, V2 and V4 to gain a more complete understand of how these visual areas cooperate during visual perception and visually-guided behavior.

Our studies of the neuronal interactions between different cortical areas should lead to an understanding of why and how the brain is divided up into so many areas, many of which seem to have functions that overlap substantially with other areas. Although we have chosen to focus on the processing in the visual system, we believe that the mechanisms of neuronal organization, interaction and connectivity that we are studying hold broad implications for our understanding of brain in both normal and diseased states.

Figure:

1. A CCD frame/image of a 9mm by 6mm portion of primate visual cortex, including a 1.5mm strip of V2 up to the lunate sulcus (top edge), and V1, lying posterior to V2. The cortex was illuminated with green light (540nm) for this image, to enhance the contrast of the surface vasculature.
3. The optical imaging map of ocular dominance from the same portion of visual cortex. The dark bands represent columns dominated by the left eye and the light bands, the right eye. Note the absence of ocular dominance structure in the imaged strip of V2 (topmost 1.5mm). The perpendicular arrangement of the ocular dominance columns relative to the V1/V2 border is also evident.
5. A map of orientation tuning produced by vector combination of frames acquired during stimulation with four orientations: 0, 45, 90 and 135. Note that only the preferred angle is displayed (coded in color, as shown). No information of sharpness of orientation tuning nor response strength is incorporated.
6. Image of activity (darkening) due to left eye stimulation as compared to the no-stimulus condition (right eye map not shown). Without the subtraction procedure used for the ocular dominance map, patterns of increased activity are unmasked and seen in V2. These bands/patches in V2 co-localize with the cytochromeoxidase-rich V2 stripes.

Selected References

Roe, AW, and Ts'o, DY. The visual field representation of V2 in macaque visual cortex. J. Neurosci. (1995) 15:3689-3715.

Ghose, GM, and Ts'o, DY. Form processing modules in Primate Area V4. J. Neurophys. (1997) 2191-2196.

Roe, AW, and Ts'o, DY, Specificity of color connectivity between primate V1 and V2. J. Neurophys. (1999) 2719-2730.

Ts'o, DY, Roe, AW and Gilbert, CD, A hierarchy of the functional architecture for color, form and disparity in primate visual area V2 (2001) Vision Research 41: 1333-1349.

Landisman, CE and Ts'o, DY. Color Processing in Macaque Striate Cortex: Relationships to Ocular Dominance, Cytochrome Oxidase, and Orientation (2002) J Neurophysiol 87: 3126-3137.

Landisman, CE and Ts'o, DY. Color Processing in Macaque Striate Cortex: Electrophysiological Properties (2002) J Neurophysiol 87: 3138-3151.

Reviews

Ts'o, DY and Roe, AW. Functional compartments in visual cortex: segregation and interaction. The Cognitive Neurosciences, Gazzaniga, MS (ed), MIT Press (1994), Cambridge, pp. 325-337.

Ts'o, DY and Roe, AW. The functional architecture of area V2 in the macaque monkey: Physiology, topography and connectivity. Cerebral Cortex, Kass, J. and Rockland, K. (eds), Plenum Press (1998).

This profile was last updated on 09/29/2008




A short link is available for this profile: http://www.upstate.edu/faculty/?ID=tsod

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