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Extrastriate feedback to primary visual cortex in primates: a quantitative analysis of connectivity
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posted on 2023-06-08, 10:57 authored by Julian M L BuddKnowledge-based or top-down influences on primary visual cortex (area V1) are believed to originate from information conveyed by extrastriate feedback axon connections. Understanding how this information is communicated to area V1 neurons relies in part on clucidating the quantitative as well as the qualitative nature of extrastriate pathway connectivity. A quantitative analysis of the connectivity based on anatomical data regarding the feedback pathway from extrastriate area V2 to area V1 in macaque monkey suggests (i) a total of around ten million or more area V2 axons project to area V1; (ii) the mean number of synaptic inputs from area V2 per upper-layer pyramidal cell in area V1 is less than 6% of all excitatory inputs; and (iii) the mean degree of convergence of area V2 afferents may be high, perhaps more than 100 afferent axons per cell. These results are consistent with empirical observations of the density of radial myelinated axons present in the upper layers in macaque area V1 and the proportion of excitatory extrastriate feedback synaptic inputs onto upper-layer neurons in rat visual cortex. Thus, in primate area V1, extrastriate feedback synapses onto upper-layer cells may, like geniculocortical afferent synapses onto layer IVC neurons, form only a small percentage of the total excitatory synaptic input.
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Publication status
- Published
Journal
Proceedings: Biological SciencesISSN
0962-8452Publisher
The Royal SocietyPublisher URL
Issue
1400Volume
265Page range
1037-1044ISBN
0962-8452Department affiliated with
- Informatics Publications
Full text available
- No
Peer reviewed?
- Yes
Legacy Posted Date
2012-02-21Usage metrics
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