A tale of two agnosias: distinctions between form and integrative agnosia.
The performance of two patients with visual agnosia was compared across a number of tests examining visual processing. The patients were distinguished by having dorsal and medial ventral extrastriate lesions. While inanimate objects were disadvantaged for the patient with a dorsal extrastriate lesion, animate items are disadvantaged for the patient with the medial ventral extrastriate lesion. The patients also showed contrasting patterns of performance on the Navon Test: The patient with a dorsal extrastriate lesion demonstrated a local bias while the patient with a medial ventral extrastriate lesion had a global bias. We propose that the dorsal and medial ventral visual pathways may be characterized at an extrastriate level by differences in local relative to more global visual processing and that this can link to visually based category-specific deficits in processing.
Riddoch
M Jane
MJ
School of Psychology, University of Birmingham, Birmingham, UK. M.J.Riddoch@bham.ac.uk
Humphreys
Glyn W
GW
Akhtar
Nabeela
N
Allen
Harriet
H
Bracewell
R Martyn
RM
Schofield
Andrew J
AJ
D000369:Aged, 80 and over; D000377:Agnosia / Q000175:diagnosis* / Q000503:physiopathology / Q000523:psychology; D001288:Attention / Q000502:physiology; D001931:Brain Mapping; D015350:Contrast Sensitivity / Q000502:physiology; D003867:Depth Perception / Q000502:physiology; D004193:Discrimination Learning; D004410:Dyslexia / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D005260:Female; D005364:Field Dependence-Independence; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D020238:Prosopagnosia / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology; D012858:Size Perception / Q000502:physiology; D020521:Stroke / Q000150:complications / Q000503:physiopathology; D014792:Visual Acuity / Q000502:physiology; D014793:Visual Cortex / Q000503:physiopathology; D014795:Visual Pathways / Q000503:physiopathology