17 Oct
2005
17 Oct
'05
1 p.m.
*Előadás a BME Kognitív Tudományi Központ*
*házi kollokvium sorozata keretében:*
*Előadó: Zsóri Adrienn, *Magdeburgi Egyetem, Németország
*Cím:* Temporal dynamics of visual processing during binocular rivalry
* *
During binocular rivalry different images simultaneously presented to
both eyes compete for perceptual dominance. The result of this competition
is an unstable, changing percept that offers a unique opportunity to
investigate the neural correlates during conscious and unconscious
perception. In a combined MEG/EEG-study subjects were presented with a
squared aperture in which 100 red dots moved coherently to the left while
other 100 blue dots moved rightwards thereby defining two transparent
surfaces. The subjects viewed the stimuli through red-blue glasses
guaranteeing that each transparent surface was seen by a different eye and
were instructed to press a button to indicate which percept (left or right
moving surface) was dominant. Small vertical translations of the dots
served as a probe and randomly occurred in either the leftwards or the
rightwards moving surface. The event-related electric (ERP) and magnetic
(ERF) responses to the probes on each surface were compared as a function
of whether the surface on which the probe occurred was the dominant
percept or not. This made it possible to compare ERP and ERF responses
elicited by exactly the same physical stimulus in two different states of
awareness. This comparison revealed a significant difference in the
electrophysiological responses starting at 110 ms post-stimulus.
Source analysis of this difference indicated that the earliest sources
were located in the medial superior occipital cortex. At 130 ms estimates
of activity could also be observed in the primary visual cortex around the
occipital pole. Importantly, the source strength of the superior medial
occipital cortex was higher during unconscious than during conscious
perception. This temporal pattern of activation is consistent with the
idea of top-down control of the primary visual cortex by higher order
extrastriate regions. The higher strength of the superior medial occipital
sources during unconscious perception suggests that the top-down is of
inhibitory nature.
*Idő:* 2005 október 24, 17 óra
*Hely:* BME, St. épület 320
Minden érdeklődőt szeretettel várunk.
Jakab Zoltán