agnosia

a disorder of the brain whereby the patient cannot interpret sensations correctly although the sense organs and nerves conducting sensation to the brain are functioning normally. It is due to a disorder of the association area in the parietal lobes. In auditory agnosia the patient can hear but cannot interpret sounds (including speech). A patient with tactile agnosia (astereognosis) retains normal sensation in his hands but cannot recognize three-dimensional objects by touch alone. In visual agnosia the patient can see but cannot interpret symbols, including letters ( see alexia ).