Seeing, since childhood, without ventral stream: a behavioural study.
We report the case of a 30-year-old man (S.B.) who developed visual agnosia following a meningoencephalitis at the age of 3 years. MRI disclosed extensive bilateral lesions of the occipital temporal visual pathway (ventral stream) and lesions in the right dorsal pathway, sparing primary visual cortices. S.B. showed a severe visual recognition deficit (texture, colour, objects, faces and words), although movement and space perception were largely preserved. His remaining visual capacities illustrate the competence of an isolated dorsal system which essentially functions on the sole basis of magnocellular afferents (low spatial resolution, high sensitivity to low contrast and moving stimuli). Patient S.B. also shows remarkable visuomotor competences, despite his perceptual limitations. It is suggested that his perceptual capacities correspond to the visual processing limitations of the dorsal visual stream, which in this patient have become accessible to perceptual awareness.
Lê
Sandra
S
INSERM U455 and Federation of Neurology, CHU Purpan, Toulouse, France. sandrale@purpan.inserm.fr
Cardebat
Dominique
D
Boulanouar
Kader
K
Hénaff
Marie-Anne
MA
Michel
François
F
Milner
David
D
Dijkerman
Chris
C
Puel
Michèle
M
Démonet
Jean-François
JF
D000293:Adolescent; D000328:Adult; D000377:Agnosia / Q000473:pathology / Q000503:physiopathology*; D002648:Child; D003867:Depth Perception; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008590:Meningoencephalitis / Q000150:complications*; D009483:Neuropsychological Tests; D011597:Psychomotor Performance; D014793:Visual Cortex / Q000473:pathology; D014795:Visual Pathways / Q000473:pathology / Q000503:physiopathology*; D014796:Visual Perception / Q000502:physiology*