We propose experiments that would examine a fundamental issue in development: whether structure and function in a target structure is determined by intrinsic properties of the target or by its inputs during development. We nave induced, by appropriate surgery in neonatal ferrets, retinal projections into the medial geniculate nucleus (MGN), the principal auditory thalamic nucleus. The MGN with retinal input retains its projections to auditory cortex. We have shown that retinal input to the MGN in """"""""rewired"""""""" animals arises from small retinal ganglion cells with slow conduction velocities, that the pathways for visual inputs to the primary auditory cortex (AI) is from the retina via the MGN, that neurons in the MGN and AI have visual receptive fields, and that a map of visual space exists in AI. In the next grant period, we shall examine: (1) the structure of individual retinal ganglion cells that project to the MGN in rewired animals and compare the cells with ganglion cells in the normal retina; (2) the structure of single retinal axon arbors within the MGN in rewired animals, and compare the arbors with those of retinal axons in normal targets; (3) the physiological properties of visual cells and the visual field map in the MGN; (4) the physiological properties of visual cells in AI, and compare their response features with cells in primary visual cortex (VI); (5) the arbors of single thalamocortical axons that project from the MGN to AI in rewired animals; (6) the mapping of thalamocortical fibers in AI after silencing cortical cells by infusion of muscimol; (7) the spatial distribution of thalamocortical excitation and intracortical inhibition in slices of rewired and normal AI; (8) the intracortical restriction of visual receptive fields in AI by microiontophoresis of bicuculline; and (9) whether rewired ferrets perceive visual stimuli presented to the rewired pathway as visual or as auditory. The experiments follow from, and extend, our work in the previous grant period. The studies have implications not only for mechanisms of normal development but also for mechanisms underlying sparing and recovery of function after early trauma to the brain.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY007719-06
Application #
2161655
Study Section
Visual Sciences B Study Section (VISB)
Project Start
1988-07-01
Project End
1996-03-31
Budget Start
1994-04-01
Budget End
1996-03-31
Support Year
6
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Massachusetts Institute of Technology
Department
Other Basic Sciences
Type
Other Domestic Higher Education
DUNS #
City
Cambridge
State
MA
Country
United States
Zip Code
02139
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Angelucci, A; Clasca, F; Sur, M (1998) Brainstem inputs to the ferret medial geniculate nucleus and the effect of early deafferentation on novel retinal projections to the auditory thalamus. J Comp Neurol 400:417-39
Angelucci, A; Clasca, F; Sur, M (1996) Anterograde axonal tracing with the subunit B of cholera toxin: a highly sensitive immunohistochemical protocol for revealing fine axonal morphology in adult and neonatal brains. J Neurosci Methods 65:101-12
Pallas, S L; Hahm, J; Sur, M (1994) Morphology of retinal axons induced to arborize in a novel target, the medial geniculate nucleus. I. Comparison with arbors in normal targets. J Comp Neurol 349:343-62
Pallas, S L; Sur, M (1994) Morphology of retinal axon arbors induced to arborize in a novel target, the medial geniculate nucleus. II. Comparison with axons from the inferior colliculus. J Comp Neurol 349:363-76
Sur, M (1993) Cortical specification: microcircuits, perceptual identity, and an overall perspective. Perspect Dev Neurobiol 1:109-13
Roe, A W; Garraghty, P E; Esguerra, M et al. (1993) Experimentally induced visual projections to the auditory thalamus in ferrets: evidence for a W cell pathway. J Comp Neurol 334:263-80
Pallas, S L; Sur, M (1993) Visual projections induced into the auditory pathway of ferrets: II. Corticocortical connections of primary auditory cortex. J Comp Neurol 337:317-33
Roe, A W; Pallas, S L; Kwon, Y H et al. (1992) Visual projections routed to the auditory pathway in ferrets: receptive fields of visual neurons in primary auditory cortex. J Neurosci 12:3651-64
Pallas, S L; Roe, A W; Sur, M (1990) Visual projections induced into the auditory pathway of ferrets. I. Novel inputs to primary auditory cortex (AI) from the LP/pulvinar complex and the topography of the MGN-AI projection. J Comp Neurol 298:50-68

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