Agnosia

AGNOSIA (from the Greek a- negative particle, and gnosis-knowledge), a disorder of recognition. In agnosia, the patient hears, sees, and touches, but does not recognize what they hear or see or touch, while being well-oriented in all other respects. In connection with this, auditory, visual, and tactile agnosia are distinguished, sometimes inappropriately called mental deafness, mental blindness, or tactile paralysis. In auditory agnosia, patients do not recognize sounds and noises that were previously familiar to them. A special case of auditory agnosia is verbal or, better, speech deafness (see Aphasia). It is caused by a focus in the first temporal gyrus on the left. In visual agnosia, the patient does not recognize objects or their individual qualities, for example, color, shape. A special case is verbal or, better, speech blindness, or alexia (see). It is caused by a focus in the occipital lobe (field 19 according to Brodmann or OA and possibly OB according to Economo). In tactile agnosia, patients by touch, which is normal in them, do not recognize objects, their shape (astereognosis). It is caused by a focus in the parietal gyrus. See also Anosognosia and Autotopagnosia.