Banca de DEFESA: BEATRIZ CARVALHO FROTA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : BEATRIZ CARVALHO FROTA
DATE: 12/06/2023
TIME: 08:30
LOCAL: https://meet.google.com/gzz-rgnz-ssw
TITLE:

Functional characterization intra- and interhemispheric of pairs and assemblies of  neurons formed in the primary visual cortex

KEY WORDS:

callosal connections, primary visual cortex, firing neuronal activity and perceptual integration.

PAGES: 206
BIG AREA: Ciências Biológicas
AREA: Fisiologia
SUMMARY:

In the primary visual cortex, connections to the corpus callosum maintain selectivity for specific visual features in homologous regions of the hemispheres. Its central position allows comparing intra- and inter-hemispheric activities, representing movement trajectories that cross the vertical meridian of the visual field. Thus, the long-range horizontal connections allow the deduction of shapes and movements, following Gestalt principles that reflect functional architecture. To verify these interactions, neurons were recorded simultaneously with two arrays of electrodes, with sixteen channels each, implanted in homotopic parts of the visual cortex, that is, the transition zone between area 17 and 18, in cats (n = 4), selected from intrinsic signal images. Electrophysiological recordings were made before and during visual stimulation with gratings and natural scenes, designed to study this interhemispheric integration. Analysis was performed by lowgamma coherence (30-59 Hz) between pairs of neurons with overlapping receptive fields; by the Fano factor and by the identification of neuronal assemblies. Significant coherence 20% greater was found in intra-pairs than between inter-hemispheric pairs, increasing by 15% where unstimulated and evoked activity showed significant coherence, both with orientation and direction selectivity. Furthermore, the Fano factor was higher in intrahemispheric pairs and with opposite selectivity preferences, that is, with more variation than pairs with the same preference and interhemispheric. As for the neuronal assemblies, both intra- and inter-hemispheric were identified, both with directional selectivity. For gratings, there was a significant difference between the two types of assemblies in vertical conditions, with greater activity in intrahemispheric assemblies and for natural scenes, both types had similar activities, but greater activation in interhemispheric ones. In conclusion, coherences between pairs of neurons and interhemispheric assemblies were identified in V1, reflecting the selectivity of horizontal axons that link neurons with similar responses over long distances, anticipating clustering between neurons that represent the vertical meridian.

COMMITTEE MEMBERS:
Externo à Instituição - SERGIO ANDRÉS CONDE OCAZIONEZ
Interno - 1721223 - ADRIANO BRETANHA LOPES TORT
Interno - 3086031 - DANIEL YASUMASA TAKAHASHI
Presidente - 1871878 - KERSTIN ERIKA SCHMIDT
Externo à Instituição - NATANAEL ANTONIO DOS SANTOS - UFPB