Agnosia
Agnosia is the inability to process sensory information. Often there is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or neurological illness, particularly after damage to the occipitotemporal border, which is part of the ventral stream. Agnosia only affects a single modality, such as vision or hearing. More recently, a top-down interruption is considered to cause the disturbance of handling perceptual information.
Apperceptive agnosia
Following Hermann Munk's identification of a condition he called "Seelenblindheit" (mind-blindness) Heinrich Lissauer published an exhaustive diagnostic evaluation of a patient who could not, or only with great difficulty, visually identify common objects. Because primary visual processing was intact, Lissauer considered the possible diagnostic distinction between deficits in perception (apperceptive agnosia) and in recognition (associative agnosia).