Abstract
Subtypes of acquired prosopagnosia have long been proposed, including apperceptive, associative and amnestic variants. The relation of functional subtype to underlying variations in lesion anatomy is an area of study. The recent development of fMRI localizers that reliably identify regions of the core face-processing network (FFA, OFA, and STS) in single subjects allows us to transform structure-function questions into investigations of the relation between behaviour and the status of face networks. Here we describe two paradigmatic patients with acquired prosopagnosia:
BP had had herpes encephalitis causing a right anterior temporal lesion, with fMRI showing an intact core network, but most likely loss of aIT. Neuropsychological testing showed sparing of other perceptual and memory functions, with deficits on the face component of the Warrington Recognition Test and the Cambridge Face Memory Test. She was impaired on the Famous Faces test, but had normal semantic knowledge of people. She was normal on many face perception tasks, including face detection, gender perception, expression perception, discrimination of facial features and configuration, and view-invariant face discrimination. She was impaired on face imagery, however.
RG had a right medial occipitotemporal stroke that destroyed the FFA but spared OFA and STS. Neuropsychological tests showed sparing of other perceptual and memory functions, and he too was impaired on the Famous Faces test, but had normal semantic knowledge of people. Unlike BP, RG showed widespread impairments on many face perception tests, including face detection, gender perception, discrimination of facial features and configuration, and view-invariant face discrimination. Imagery of global facial properties was normal, in contrast to BP.
We conclude that BP has an amnestic variant of prosopagnosia associated with right anterior temporal damage, likely including aIT, but sparing OFA and FFA, and that RG has an apperceptive variant, from right fusiform damage and loss of the FFA.
ESRC (RES-061-23-0040), CIHR (MOP-77615), Michael Smith Foundation for Health Research, Canada Research Chairs Program.