Complete or partial loss of the ability to recognise familiar objects or stimuli (including faces), usually as a result of brain damage, mostly to the parietal or occipital cortex. In addition to visual agnosia, there is auditory agnosia, an inability to recognise or understand the meaning of spoken words, and olfactory agnosia, an inability to recognise smells. Then there is position agnosia: the failure to recognise the posture of an extremity. Agnosia, which does not involve significant memory loss, occurs in neurological disorders such as strokes and dementia.
See Cerebral cortex (disorders), Cerebral (or intracerebral) hemorrhage, Cortical lobes, Double dissociation, Experimental method, Face recognition, Inferior temporal cortex, Occipital cortex (or lobe), Parietal cortex, Prosopagnosia