Previous studies from this lab provided evidence that postnatal brain development in olfactory and somatosensory cortices is mainly constructive, and that neural activity foments postnatal elaboration of circuitry. The present proposal addresses the question of why the brain adds enormous numbers of neuronal branches and synapses postnatally in an activity-dependent manner, especially since this entails jeopardy from the effects of deprivation. A review of the evidence in anthropoid primates suggests that the expression of ocular dominance columns in visual cortex is related to animal size.
The first aim of the study is to confirm the validity of this 'size' principle among several carnivores and prosimians.
The second aim i s to determine whether the size principle results from differences in the duration of asynchronous binocular activity during development. This will be tested by 1) attempting to generate ocular dominance columns in animals which normally do not express them; and 2) directly following the formation and modulation of ocular dominance columns with optical imaging during development.
A third aim will be to explore in humans the hypothesis the activity-dependent construction of the visual world serves to establish neural associations that allow a correct interpretation of an inherently ambiguous visual world (the consensus at the present is that activity acts primarily to validate and refine receptive field properties). This will entail an analysis of 1) the perception of transparent 3-D objects; and 2) the relationship between biases in the perception of oriented contours and the prevalence of differently oriented contours in the visual world. The results of these several projects should indicate whether the prolonged postnatal period of activity-dependent plasticity in mammals plays a largely permissive role, or whether it enables experience to make the visual associations that allow us to see normally.
| Lotto, R Beau; Purves, Dale (2002) A rationale for the structure of color space. Trends Neurosci 25:84-8 |
| Lotto, R B; Purves, D (2001) An empirical explanation of the Chubb illusion. J Cogn Neurosci 13:547-55 |
| Yang, Z; Shimpi, A; Purves, D (2001) A wholly empirical explanation of perceived motion. Proc Natl Acad Sci U S A 98:5252-7 |
| Nundy, S; Lotto, B; Coppola, D et al. (2000) Why are angles misperceived? Proc Natl Acad Sci U S A 97:5592-7 |
| Purves, D; Williams, S M; Lotto, R B (2000) The relevance of visual perception to cortical evolution and development. Novartis Found Symp 228:240-54; discussion 254-8 |
| Lotto, R B; Purves, D (2000) An empirical explanation of color contrast. Proc Natl Acad Sci U S A 97:12834-9 |
| Purves, D; Lotto, B; Polger, T (2000) Color vision and the four-color-map problem. J Cogn Neurosci 12:233-7 |
| Andrews, T J; Coppola, D M (1999) Idiosyncratic characteristics of saccadic eye movements when viewing different visual environments. Vision Res 39:2947-53 |
| White, L E; Bosking, W H; Williams, S M et al. (1999) Maps of central visual space in ferret V1 and V2 lack matching inputs from the two eyes. J Neurosci 19:7089-99 |
| Halpern, S D; Andrews, T J; Purves, D (1999) Interindividual variation in human visual performance. J Cogn Neurosci 11:521-34 |
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