Functional differentiation in the visual cortex: Basis for motor activation by not consciously perceived stimuli?

Author(s): Ansorge, U., Klotz, W.

Journal/Book: Psychol Rundsch. 1998; 49: Rohnsweg 25, D-37085 Gottingen, Germany. Hogrefe & Huber Publishers. 185-196.

Abstract: For about half a century, studies of ''subliminal perception'' have been besieged by two problems. First, the very existence of the phenomenon has been doubtful, and second, it was - if it existed - difficult to integrate into a theoretical framework. We argue that the situation is presently changing in both respects. There are now various observations from neuropsychology demonstrating that sensory information can be processed and used in the control of behavior without being represented in consciousness (e.g., blindsight, visual form agnosia). A similar dissociation (the Metacontrast Dissociation) can be induced in healthy people when a visual stimulus is masked by metacontrast. Under appropriate masking conditions, both behavioral (RT, error rate) and EEG data (lateralized readiness potentials) indicate that the masked stimulus affects motor activation although it cannot be consciously perceived according to the strictest criterion (a d' of zero). At a theoretical level, the Metacontrast Dissociation may be viewed as an example of the more general phenomenon of direct parameter specification (Neumann, 1989, 1990 a); and it could in part be related to the functional differentiation between a dorsal and a ventral stream of visual processing (Milner & Goodale, 1995).

Note: Article Neumann O, Univ Bielefeld, Psychol ABT, Postfach 10 01 31, D-33501 Bielefeld, GERMANY

Keyword(s): consciousness; direct parameter specification; dorsal stream; motor activation; lateralized readiness potential; unconscious perception; ventral stream; DIRECT PARAMETER SPECIFICATION; POSTERIOR PARIETAL CORTEX; UNILATERAL NEGLECT; REACTION-TIME; FORM AGNOSIA; INFORMATION; PERCEPTION; DISSOCIATION; DISCRETE; VISION

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