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Joan Liu-Shuang, Katrien Torfs, Bruno Rossion; Rapid and objective quantification of perceptual deficits in acquired prosopagnosia with fast periodic oddball stimulation . Journal of Vision 2016;16(12):1254. doi: 10.1167/16.12.1254.
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© 2017 Association for Research in Vision and Ophthalmology.
Perceptual deficits are common in many neurological conditions, but their assessment can be hindered by various unrelated factors (e.g. attention, comprehension, motor impairments…). Hence, a method allowing for an objective, sensitive, and efficient quantification of perception without requiring explicit behavioural output would be highly valuable. In the recently developed fast periodic oddball paradigm, base stimuli appear at a fixed rate (F Hz) with oddball stimuli, differing on a dimension of interest, inserted at regular intervals (every nth stimulus, or F/n Hz; Liu-Shuang et al., 2014, Neuropsychologia, 52, 57-72). Periodic EEG responses at the F/n Hz oddball frequency and harmonics (2F/n Hz, 3F/n Hz…) reflect the perceptual discrimination between base and oddball stimuli. We tested this approach with PS, a well-described patient who is specifically impaired at face individualisation following brain damage (acquired prosopagnosia). PS was first presented with sequences of base "object" stimuli at 6 Hz with periodically interleaved oddball "face" stimuli at 1.2 Hz (every 5th stimulus; sequence structure: ObjObjObjObjFaceObjObjObjObjFace…). In line with her preserved ability to detect faces, PS showed periodic oddball responses within the normal range. However, when face identity discrimination was tested with "different" oddball face identities (B, C, D…) inserted into sequences containing a repeated "same" base face identity (A; sequence structure: AAAABAAAACAA…, Liu-Shuang et al., 2014), significant oddball responses were found in all control (young and age-matched) participants but were absent for patient PS. These observations were obtained within 8 and 12 min of recording, respectively. Overall, our findings underline the value of the fast periodic oddball paradigm as a diagnostic tool for the rapid and objective characterisation of visual discrimination in neuropsychology and difficult to test populations.
Meeting abstract presented at VSS 2016
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