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.
Visual agnosia
Magnetic Resonance Imaging (MRI) showed bilateral thinning of C.K.’s Occipital Lobe which resulted in associative visual agnosia. Patients that suffer from visual agnosia are unable to identify visually presented objects. They can identify these objects through other modalities such as touch but if presented visually, they are unable to. Associative Agnosic patients cannot create a detailed representation of the visual world in their brains, they can only perceive elements of whole objects. They also cannot form associations between objects or assign meaning to objects.