Banca de QUALIFICAÇÃO: DARDO NAHUEL FERREIRO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : DARDO NAHUEL FERREIRO
DATA : 29/01/2018
HORA: 13:30
LOCAL: INSTITUTO DO CÉREBRO
TÍTULO:

Study of a big Amazonian rodent visual cortex: spatial clustering of orientation preference in the agouti

PALAVRAS-CHAVES:

visual cortex, agouti, cat, electrophysiology, functional anatomy, orientation map

PÁGINAS: 50
GRANDE ÁREA: Ciências Biológicas
ÁREA: Fisiologia
RESUMO:

So far, there is no evidence of a columnar orientation preference map in rodent primary visual cortex, such as commonly observed in carnivores and primates. At the same time, orientation selective neurons have been found in all rodent species investigated, though interspersed. This opens up the question whether the connectivity underlying the emergence of selective cortical response properties in animals with interspersed as compared to columnar maps follows a different blueprint. Rodent data are so far mainly available for species with nocturnal or crepuscular habits and small brain size, two factors that could also contribute to develop a different functional architecture.

Therefore, we set out to compare the functional architecture of the primary visual cortex of carnivores with that of a big rodent with diurnal habits, and a V1 size comparable to cats and small primates. To this end, we performed multi-site electrophysiological recordings using spatial arrays from both anesthetized cats’ (Felis catus) and agoutis’ (Dasyprocta aguti) visual cortex. Visual stimuli consisted of oriented gratings of several spatial and temporal frequencies.

Although we detected a similar ratio of orientation selective neurons in both species (58% for cats and 62% for agoutis), overall, agoutis presented much smaller orientation selectivity indices (median OSI = 0.10) than cats (median OSI = 0.19). In order to describe the functional architecture based on the electrophysiological data, we quantified the orientation preference difference between neurons according to the cortical distance between them. As expected, this analysis revealed a characteristic slow decrease in neuronal orientation preference similarity for cats. No such “classical” modularity was found for agoutis, but a clustering of neurons with similar orientation preferences was observed for short ranges (< 250um).

 Overall, our results are consistent with recent literature reporting ‘mini-columns’ of orientation preference in mice, and therefore further prove that the rodents’ interspersed maps are not random, as previously assumed. We cannot confirm, however, recent theoretical literature suggesting that agoutis might have “classical” columnar orientation preference maps. Future research should focus to understand the circuits, which lead to small selective receptive fields in agoutis and great visual performance while adopting a different functional architecture.

MEMBROS DA BANCA:
Interno - 2069422 - DIEGO ANDRES LAPLAGNE
Presidente - 1871878 - KERSTIN ERIKA SCHMIDT
Interno - 1842426 - SERGIO TULIO NEUENSCHWANDER MACIEL