Bernal S D_2010.pdf - University of Plymouth

2,1. OBJECT RECOGNITION
ihe principles underlying object recognition in the visual cortex, which can be understood as
the initial feedforward processing stage leading to fast object categorization and identification
(Serre et al. 2007b),
Note this section includes a general description of all the different areas involved in visual pro­
cessing and an overview of the interactions which lead to an integrated percept. However, the
section focuses on the feedforward processing strategies which lead to rapid object categoriza­
tion, while Section 2.2 below deals specifically with feedback and the integration of information
across the visual system.
2.1.1.1 Hierarchical distributed organi/ution.
The visual system is capable of transforming light falling on the retina into neuronal electrical
signals, which give rise lo subjective visual perceplion. This is usually achieved in time periods
measured in milliseconds, bm requires complex information processing and encompasses sev­
eral stages of analysis across many different regions. The macaque visual system, for example,
has been classified into 32 distinct areas interconnected via over 300 reciprocal anatomical path­
ways (Felleman and Van Essen 1991), shown in Figure 2.1a. These areas have a hierarchical
organization starting at the lateral geniculate nucleus (LGN), ascending through primary visual
cortex (VI) and finishing in higher cortical structures. Kach of these areas is considered to be
functionally specialized, and embodies in itself a set of subdivisions (e.g. 6-layer cortical struc­
ture). Two major parallel processing streams have been identified in the visual hierarchy: Ihe
dorsal or where stream, and the ventral or w/wi/ stream, schematically represented in F-igure 2.1b
(Van lissen and Gallant 1994).