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Comparison of the spatial matrix of facilitatory subfields between multiple V2 neurons in infant monkeys



Conference Title

Society of Neuroscience Annual Meeting


Society of Neuroscience


New Orleans, Louisiana / October 13-17, 2012

Publication Date / Copyright Date



Our recent anatomical study with a tracer (CTB) injection method showed that the projection fibers from V1 to V2 and the intrinsic connections of V2 in macaque monkeys are relatively immature during the first 4 postnatal weeks, but become qualitatively adult-like by 8 weeks of age (Baldwin et al, 2012). In this study we explored the physiological correlates of these immature connections by comparing the spatial organization of subunits within the receptive fields of several V2 neurons that were recorded simultaneously with a single microelectrode. Recordings were made in anesthetized and paralyzed macaque monkeys ranging in age between 4 and 16 weeks. The responses of each unit were isolated using the unit sorting software in our system. We employed dynamic two dimensional noise stimuli and a reverse correlation (LSRC) method to reveal subfields within the receptive field of each neuron and the spatial matrix of these subfields were compared between multiple neurons with respect to their preferred orientations, spatial frequencies, maximal strengths (Zmax) of responses. We found the following. 1) In 4-week-old infants, the preferred orientation of a neuron determined by the weighted sum of the preferred orientations of all facilitatory subfields within the spatial matrix substantially differed between units at a given recording site, but the differences become less in 8-week-old infants. The comparable data from 16-week-old infants were indistinguishable from those in adults. 2) The homogeneity of subfields between the units at a given recording site showed similar developmental changes; the average orientation difference between a pair of facilitatory subfields in different units at a given recording site was largest in 4-week-old infants and became progressively less with age. The present results dovetail nicely with the anatomical study showing that the feed forward connections from V1 to V2 and the intrinsic connections of V2 are relatively diffuse during the first 4 weeks of monkey’s life and that this immaturity becomes far less obvious in 8-week-old infants.



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