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- Face recognition ability is manifest in early dynamic decoding of face-orientation selectivity - Evidence from multi-variate pattern analysis of the neural responsePublication . Mares, Inês; Ewing, Louise; Papasavva, Michael; Ducrocq, Emmanuel; Smith, Fraser W.; Smith, Marie L.ABSTRACT: Although humans are considered to be face experts, there is a well-established reliable variation in the degree to which neurotypical individuals are able to learn and recognise faces. While many behavioural studies have characterised these differences, studies that seek to relate the neuronal response to standardised behavioural measures of ability remain relatively scarce, particularly so for the time-resolved approaches and the early response to face stimuli. In the present study we make use of a relatively recent methodological advance, multi-variate pattern analysis (MVPA), to decode the time course of the neural response to faces compared to other object categories (inverted faces, objects). Importantly, for the first time, we directly relate metrics of this decoding assessed at the individual level to gold-standard measures of behavioural face processing ability assessed in an independent task. Thirty-nine participants completed the behavioural Cambridge Face Memory Test (CFMT), then viewed images of faces and houses (presented upright and inverted) while their neural activity was measured via electroencephalography. Significant decoding of both face orientation and face category were observed in all individual participants. Decoding of face orientation, a marker of more advanced face processing, was earlier and stronger in participants with higher levels of face expertise, while decoding of face category information was earlier but not stronger for individuals with greater face expertise. Taken together these results provide a marker of significant differences in the early neuronal response to faces from around 100 ms post stimulus as a function of behavioural expertise with faces.
- Effects of expectation on face perception and its association with expertisePublication . Mares, Inês; Smith, Fraser W.; Goddard, E. J.; Keighery, Lianne; Pappasava, Michael; Ewing, Louise; Smith, Marie L.Perceptual decisions are derived from the combination of priors and sensorial input. While priors are broadly understood to refect experience/expertise developed over one’s lifetime, the role of perceptual expertise at the individual level has seldom been directly explored. Here, we manipulate probabilistic information associated with a high and low expertise category (faces and cars respectively), while assessing individual level of expertise with each category. 67 participants learned the probabilistic association between a color cue and each target category (face/car) in a behavioural categorization task. Neural activity (EEG) was then recorded in a similar paradigm in the same participants featuring the previously learned contingencies without the explicit task. Behaviourally, perception of the higher expertise category (faces) was modulated by expectation. Specifcally, we observed facilitatory and interference efects when targets were correctly or incorrectly expected, which were also associated with independently measured individual levels of face expertise. Multivariate pattern analysis of the EEG signal revealed clear efects of expectation from 100 ms post stimulus, with signifcant decoding of the neural response to expected vs. not stimuli, when viewing identical images. Latency of peak decoding when participants saw faces was directly associated with individual level facilitation efects in the behavioural task. The current results not only provide time sensitive evidence of expectation efects on early perception but highlight the role of higher-level expertise on forming priors.