Bernal S D_2010.pdf - University of Plymouth

2.2. HIGH'LEVEL FEEDBACK
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Figure 2.8: Evolution of the compuialions performed in the different visual areas over time.
Each column represents ilie invnlvemeni of a particular region in differenl compulations
over lime. Hach row represenis parallel computations, proposed hy Marr
11982), across the multiple areas. As time progresses, the aciivily in V1 should
reflecl the inv{ilvemenl in increasingly complex computations resultin)> from reeurrenl
feedback from higher conical areas (l-ee 2CHW).
in congruence with the extra-classical receptive field idea. This information is then propagated
up the hierarchy again providing a new level of analysis which can be employed for Ihe next
stage of compulation. As time progresses, the activity in VI should rellect the involvement
in increasingly complex computations resulting from recurrent feedback from higher cortical
areas. A represenlation of the suggested temporal evolution of the functions carried out by
the different areas involved is illustrated in Figure 2.8. This challenges the classical serial
feedforward model depicted in Section 2.1.1.
2.2.2.3 Reverse Hierarchy Theory (RHT).
This theory formulated by Hochstein and Ahissar (2002), proposes an interesting thct>retical
point of view of the role of feedback connections in visual perception. Exphcit visual per­
ception is hypothesized to occur for Ihe first lime al the higher conical levels, after receiving
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