Perceptual learning of faces: a rehabilitative study of acquired prosopagnosia

Abstract

Background: Despite many studies of acquired prosopagnosia, there have been only a few attempts at its rehabilitation, all in single-cases, with a variety of mnemonic or perceptual approaches, and of variable efficacy. Method: In a cohort with acquired prosopagnosia, we evaluated a perceptual learning program that incorporated variations in view and expression, which was aimed at training perceptual stages of face processing with an emphasis on ecological validity. Ten patients undertook an 11-week face training program and an 11-week control task, as well as functional MRI resting state scans at three time-points: baseline, after training, and after a control task. Training required shape discrimination between morphed facial images, whose similarity was manipulated by a staircase procedure to keep training near a perceptual threshold. Training progressed from blocks of neutral faces in frontal view through increasing variations in view and expression. Results: While the control task did not change perception, training improved perceptual sensitivity for the trained faces and generalized to new untrained expressions and views of these faces. There was also a significant transfer to new faces. Benefits were maintained over a 3-month period. Training efficacy was greater for those with more perceptual deficits at baseline. There was increased functional connectivity between the left OFA and bilateral STS after training but not after the control task. Conclusion: We conclude that perceptual learning can lead to persistent improvements in face discrimination in acquired prosopagnosia, and that training faces at the level of three-dimensional expression-invariant representations results in increased connectivity between OFA and STS in acquired prosopagnosics.

Meeting abstract presented at VSS 2017