Speech perception
Agnosia is "the loss or diminution of the ability to recognize familiar objects or stimuli usually as a result of brain damage". There are several different kinds of agnosia that affect every one of our senses, but the two most common related to speech are speech agnosia and phonagnosia.
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.