Visual Form Agnosia

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Recommended: Psychology dissertation on visual agnosia

Visual form agnosia is defined as the inability to recognize objects (Goldstein, 2010). To understand the basic concept of visual form agnosia, it is important to first understand that perception and recognition are separate processes. Perception is defined as the ability to become aware of something through our senses, and recognition is the ability to put an object in a group that gives the item meaning. When a person suffers from visual form agnosia, they are generally able to identify the item and distinguish parts of it, but are not able to perceptually accumulate every piece of the item in order to identify the item as complete (Goldstein, 2010). The following is a review of studies concerning the different aspects, theories, and characteristics in visual form agnosia.

The brain is divided into two visual streams, the ventral and the dorsal stream. Goodale and Milner (1998) have suggested that the ventral stream is dedicated to processing vision for perception, and the dorsal stream for vision and action. On the other hand, there is a possibility that the processes in the visuomotor stream can provoke perceptual processes. The propose of the visuomotor stream is that it provides signals, which enhances the person’s ability to distinguish the form of the object. This study illustrated that stimulated perceptual development vanishes if the intended objects only have a difference in respect to their shape, but not width (Goodale & Milner, 1998).

Emphasis has been placed on the disconnection of the dorsal and ventral streams, but there are also many associations between them, and the state of successful integration of their ‘complementary contributions’ can help humans with goal-directed adapted behavior (Goodale & Servos, ...

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Goodale, M.A., & Servos, P. (1995). Preserved visual imagery in visual form agnosia. Neuropsychologia, 33 (11), p. 1383-1394.

Goldstein, E.B. (2010). Sensation and perception: Eighth edition. California: Linda Schreiber.

McIntosh, R.D., Milner, A.D., Mon-Williams, M., & Tresilian, J.R. (2001). Monocular and binocular distance cues: Insights from visual form agnosia I (of III). Exp Brain Res, 139, p. 127-136

Milner, A. D., & Schenk, T. (2006). Concurrent visuomotor behaviour improves form discrimination in a patient with visual form agnosia. European journal of neuroscience, 24 (5), p. 1495-1503.

Vercera, S.P. (2001). Dissociating ‘what’ and ‘how’ in visual form agnosia: A computational investigation. Nueropsychologia, 40, p. 187-204.

Weiskrantz, L. (1997). Consciousness lost and found: A neuropsychological exploration. Oxford University Press, p. 294

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