Banca de DEFESA: LUÃ CARLOS DE SOUZA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : LUÃ CARLOS DE SOUZA
DATA : 28/04/2017
HORA: 13:00
LOCAL: INSTITUTO DO CÉREBRO
TÍTULO:

THE PROCESSING OF SPATIAL FREQUENCY ACROSS THE CORPUS CALLOSUM DURING MONOCULAR AND BINOCULAR STIMULATION

PALAVRAS-CHAVES:

Primary visual cortex, spatial frequency, inter-hemispheric visual connections, monocular stimulation, binocular stimulation

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

Neurons in cat primary visual cortex (area 17 and 18) respond selectively to certain stimulus parameters. Such parameters are, for example, contrast, contours of the same orientation and direction of movement, but also the spatial frequency (SF). Differences in SF preference in areas 17 e 18 are thought to emerge from a different distribution of X and Y afferents. The transition zone (TZ), between the two areas has preferences for intermediate SFs. Apart from retino-geniculo-cortical afferents this region also receives dense visual connections through the corpus callosum. It is known that interhemispheric connections are more frequent between visual neurons with a preference for similar orientation and direction. However, data referring to SF selectivity of these connections are still scarce. The objective of the present study is to investigate the functional contribution of interhemispheric visual connections to responses evoked by different SFs in the TZ. While stimulating either monocularly or binocularly with gratings, we investigated the mean rate of neuronal firing in the TZ of anesthetized cats. We observed that, in general, during reversible thermal deactivation of the contralateral visual cortex mean firing rates decreased, but in particular during monocular stimulation of the ipsilateral eye. Moreover, in this condition, responses to the low spatial frequency of 0.15 cycles/degree and to neurons that prefer horizontal contours were more affected. In contrast, with contralateral stimulation, responses to the highest SF of 0.6 cycles/degree and to neurons that prefer vertical contours predominantly decreased their rates. These results indicate that interhemsipheric connections act SF selective. They also suggest that fibers conducting signals driven by the ipsilateral eye through the corpus callosum originate mainly from neurons dominated by Y cells. On the other hand, fibers mediating information from the contralateral eye seem to originate from neurons receiving input from X cells or a mixture of X and Y cells via the retino-geniculate-cortical pathway. The different circuits for low and high spatial frequencies may be involved in a process of binocular interaction, where responses of the ipsilateral eye and the contralateral eye complement each other.

 

MEMBROS DA BANCA:
Interno - 1976236 - EMELIE KATARINA SVAHN LEAO
Externo à Instituição - JEROME PAUL ARMAND LAURENT BARON - UFMG
Presidente - 1871878 - KERSTIN ERIKA SCHMIDT
Interno - 1842426 - SERGIO TULIO NEUENSCHWANDER MACIEL