Banca de QUALIFICAÇÃO: LUÃ CARLOS DE SOUZA

Uma banca de QUALIFICAÇÃO de MESTRADO foi cadastrada pelo programa.
DISCENTE : LUÃ CARLOS DE SOUZA
DATA : 06/03/2017
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: 100
GRANDE ÁREA: Ciências Biológicas
ÁREA: Fisiologia
RESUMO:

Neurons in cat primary visual cortex (area 17 and 18) respond selective to certain parameters of a stimulus. Contrast, contours of the same orientation and direction of movement are some of these parameters. In addition, spatial frequency (SF) is also a selectivity parameter. 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 these 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 this type of influence for stimuli presented in different SFs 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 during reversible thermal deactivation of the contralateral visual cortex, overall, rates decreased, mainly during monocular stimulation of the ipsilateral eye. 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 suggest that fibers conducting information from 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 and thus build together a complex image rich in detail of a visual scene. 

MEMBROS DA BANCA:
Presidente - 1871878 - KERSTIN ERIKA SCHMIDT
Interno - 1842426 - SERGIO TULIO NEUENSCHWANDER MACIEL
Interno - 1976236 - EMELIE KATARINA SVAHN LEÃO