Category-related recognition defects as a clue to the neural substrates of knowledge.

Circumscribed damage to human cerebral cortex can lead to a surprisingly selective breakdown of recognition. Patients may be unable to recognize a person's identity from their face, but retain the ability to recognize identity from gait, or they may experience a disproportionate difficulty in recognizing entities belonging to certain conceptual categories, such as natural kinds, and no difficulty in recognizing man-made items. The relation between such patterns of breakdown and the underlying damage to specific cortical regions suggests a possible organization for the neural substrates of knowledge, at the level of systems. In general, it appears that different neural systems are dedicated to the processing of certain characteristics of entities and events, in certain knowledge domains, but that systems are not dedicated to the representation of particular conceptual categories.