Integrative agnosia


Integrative agnosia

Integrative agnosia, as first defined by Riddoch and Humphreys (1987),http://pissaro.soc.huji.ac.il/~leon/mivnim/pdfs/Riddoch%20stm%20in%20integartive%20agnosia.pdf] is the disability to recognize objects due to the inability to group and integrate the component parts of the object into a coherent whole.Gazzaniga, Ivry & Mangun: "Cognitive Neuroscience", 2nd edition, 2002.] Integrative agnosia is a subtype of associative agnosia. [ [http://www.unites.uqam.ca/cnc/psy7123/objectrecognition.pdf Microsoft PowerPoint - objectrecognition ] ]

Although the grouping of local elements into perceptual wholes can be impaired in integrative agnosia, patients can still be able to perceive holistic visual representations. For example, patients can respond in a relatively normal way to global compound letters. They can match stimuli based on low spatial frequency components of shape (thick lines and gradual changes in color). Their identification of silhouettes can be at least as good as their identification of line drawings.
Patients can reproduce drawings of objects; however, what they see is isolated, unconnected parts or contours.

Riddoch and Humphreys proposed that patients could obtain global shape information from low spatial frequency components in the image and that this could contribute to performance in a variety of tasks. However, without integration from more local form elements, these global perceptual descriptions will be unelaborated. The patients don't have enough information to be able to accurately identify objects. Indeed, in many instances (e.g., with line drawings), agnosic patients can use the local line elements to divide the object they see into different objects. This demonstrates their difficulties in integrating local elements with the global form information they have available. For instance, a patient was reported as stating that he thought there were several stimuli present when given single line drawings.

References


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