The title refers to one of Sacks's patients who had
visual agnosia - a neurological condition that left him unable to recognise even familiar faces and objects.
A significant reduction in visual-perceptual and visual-constructive abilities and different modalities of visual gnosis (
visual agnosia for colors, objects and numbers) were recorded.
Kluver-Bucy syndrome (KBS) is characterized by psychic blindness or
visual agnosia, hypersexuality, emotional behavioral changes, especially placidity (decreased motor and verbal reaction against conditions that cause fear and anger), hyperorality, and hypermetamorphosis (increased interest in every object that enters the visual field) (1,2).
The term 'agnosia' literally means 'without knowledge.'
Visual agnosia describes the situation in which patients are unable to recognise stimuli visually; however, they may be able to use other senses or logical reasoning to aid identification.
Specifically, they address integrative
visual agnosia, picture identification, visual search and stimulus similarity, orthographic processing in visual word identification, non-spatial extinction following lesions of the parietal lobe, visual marking, action-based effects on object selection, theory of mind, memory-based guidance on visual selection, the salience of stimuli in selecting visual information, learned conjunctive relations, social attention, and cognition and stroke.
The man who mistook his wife for a hat was a musician who was developing
visual agnosia: a difficulty in recognizing by sight common objects or faces.
Humphreys, "A case of integrative
visual agnosia," Brain, vol.
(2) Clinical features of PCA constitute a wide variety of signs and symptoms; nevertheless, the most frequent include hemiagnosia (deficit in awareness of one side of space), optic ataxia (lack of coordination between visual inputs and hand movements, resulting in inability to reach and grab objects),
visual agnosia (an impairment in recognition of visually presented objects), alexia (difficulty to understand written words), acalculia (difficulty with simple mathematical tasks), and agraphia (loss in the ability to communicate through writing).
A case study in
visual agnosia revisited; to see but not to see, 2d ed.
Anecdotal cases have been published referring to acute aphasia (Devere, Trotter, & Cross, 2000), alexia with agraphia (Day, Fisher, & Mastaglia, 1987), alexia without agraphia (Dogulu, Kansu, & Karabudak, 1996; Mao-Draayer & Panitch, 2004),
visual agnosia (Okuda et al., 1996) and patients with more than one severe cognitive symptom, with criteria for dementia (Staff et al., 2009; Stoquart-ElSankari, Perin, Lehmann, Gondry-Jouet, & Godefroy, 2010).
Visual agnosia is a modality-specific disorder of object recognition caused by a lesion involving the visual cortex [1].