Bernal S D_2010.pdf - University of Plymouth

2.3. ILLUSORY AND OCCLUDED CONTOURS
n/LOc
V2
VI
Itiput
image
1) Higher level iibject-processing regions are first lo
represeni illusory conlours. eliciting a response lo Ihc
compleicd surface of ihc object.
^(hW'S VuilU^umji-JlDDe.YlHhinsclll. 2DD6; Sltnlcv & Aullin 7001)
*2) Response to illusory contours in lower-level regions, with
no dirccl retinal stimulation. Delayed relative lo real contours.
^Egtiti^r £ vuilletimitr lOOG. Uf jm.l^ VmhiriD M al.. ;0D&)
.1) Response in VI emerges approx. 35 ms later than in V2.
*
Suggests contour completion
is driven by Tecdback
Figure 2.11: Neural correlate and timing of illustiry contour emergence along the visual system,
wilh relevant references. Higher-level iibjecl processing regions are Ihe first
to represent illusory contours after rapid object categorization. Retinotopic responses
to illu.sory contours are then observed in lower level regions such as VI
and V2, which receive no direct retinal stiinuialiori. The response in V1 emerges
later tlian in V2, Overall, the evolution of illusory mntour emergence suggests it
is driven by fi;edback connections from higher level regions.
higher level object processing regions such as monkey IT (Sary et al. 2008) and the human
equivalent, the LOC region (Halgrcn et al. 2003. Maertens el al. 2008. Murray ei al. 2(X)2.
Seghier and Vuilleumier 2006, Yoshino et al, 2006. Stanley and Rubin 2003). A subset of these
point out that high-level activity generated by objects containing illusory contours (such as the
Kanizsu triangle) is notably similar lo the activity of complete objects, despite presenting longer
latencies (Stanley and Rubin 2003, Maerlens el al. 2008. Sary el al. 2(K)8). IT cells with spe-
ciTic selectivity for illusory contour figures have been reported (Sary et al. 2008). It has been
suggested Ihat the large non-retinotopic receptive ticlds in IT/LC)C. which receive bilateral stim­
ulation from massive regions oflhe visual field, present the best subslraie to perform grouping
across large distances, such as thai required for illusory contours.
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