In:
Acta Neurobiologiae Experimentalis, The Nencki Institute of Experimental Biology, Polish Academy of Sciences, Vol. 64, No. 2 ( 2004-06-30), p. 239-252
Abstract:
This is a review of our work on multiple microelectrode recordings from the visual cortex of monkeys and subdural recordings from humans - related to the potential underlying neural mechanisms. The former hypothesis of object representation by synchronization in visual cortex (or more generally: of flexible associative processing) has been supported by our recent experiments in monkeys. They demonstrated local synchrony among rhythmic or stochastic γ-activities (30-90 Hz) and perceptual modulation, according to the rules of figure-ground segregation. However, γ-synchrony in primary visual cortex is restricted to few millimeters, challenging the synchronization hypothesis for larger cortical object representations. We found that the spatial restriction is due to γ-waves, traveling in random directions across the object representations. It will be argued that phase continuity of these waves can support the coding of object continuity. Based on models with spiking neurons, potentially underlying neural mechanisms are proposed: (i) Fast inhibitory feedback loops can generate locally synchronized γ-activities; (ii) Hebbian learning of lateral and feed forward connections with distance-dependent delays can explain the stabilization of cortical retinotopy, the limited size of synchronization, the occurrence of γ-waves, and the larger receptive fields at successive levels; (iii) slow inhibitory feedback can support figure-ground segregation; (iv) temporal dispersion in far projections destroys coherence of fast signals but preserves slow amplitude modulations. In conclusion, it is proposed that the hypothesis of flexible associative processing by γ-synchronization, including coherent representations of visual objects, has to be extended to more general forms of signal coupling.
Type of Medium:
Online Resource
ISSN:
1689-0035
,
0065-1400
DOI:
10.55782/ane-2004-1509
Language:
Unknown
Publisher:
The Nencki Institute of Experimental Biology, Polish Academy of Sciences
Publication Date:
2004
detail.hit.zdb_id:
2053509-0
detail.hit.zdb_id:
184409-X
SSG:
12
Permalink
