Bernal S D_2010.pdf - University of Plymouth

2.2. HIGH-LEVEL FEEDBACK
activity generated by feedforward hottom-up implicit processing should be driven by stimuli,
kicalized and automalic. This will give rise to the first vision ai a glance high-level percept
which mi[ihl in lum activate serial search or vision with scrutiny mechanisms. As a consequence
later activity in lower-levels will reflect feedback lop-down effects such as those associated with
spatial and object allention, matching the functional temporal evolution proposed by Lee (2003).
2.2.2.4 Corlical representations of conscious visual perception.
It may be inappropriate lo refer to consciousness, as ii is a highly controversial concept which
is not well defined or understood. However, for the purpose of this section it will be interpreted
as referring to the exphcil visual perception previously described, sometimes also denoted as
visual awareness. Which area.s of the visual system are actually involved in representing the
explicit or conscious visual percept? The hypothesis til" a dislribuled representation of explicit
perception is gradually gaining favour over the traditional strictly high-level cortical reprcsen-
taiion. For the authors of the RHT, explicit perception begins a( high cortical levels and then
proceeds in a lop-down fiishion, strongly influenced by attention, to gradually incorporate more
detailed information from lower levels. It seems a reasonable assumption given that we are able
to explicitly perceive high-resolution details which can only be accurately encoded by lower-
level regions.
Supporting ihis argument, experiments based on perceptual rivalry conclude Ihat it would be
more appropriale to begin thinking of consciousness as "a characteristic of extended neural
circuits comprising several cortical levels throughout the brain" (Wilson 2(K)3). Along the
same lines, several studies conclude unstimulated areas of VI can represent illusory contours
(Maertenset al. 2008), or the illusory perception of apparent motion (Sterzereial, 2006), which
corroborates the notion that subjective perceptual activity can be closely related to neural ac­
tivity in V l. Overall, evidence seems to indicate an important role for feedback connections in
mediating explicit visual perception or awareness (Leo}X)ld and Logoiheiis 1996).
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