Processing deficits for familiar and novel faces in patients with left posterior fusiform lesions.
Bottom Line: Identification of famous faces was found to be compromised in both expressive and receptive tasks.Interestingly, discrimination of faces that varied in terms of feature identity was considerably better in these patients and it was performance in this condition that was related to the size of the length effects shown in reading.These results suggest that the sequential part-based processing strategy that promotes the length effect in the reading of these patients also allows them to discriminate between faces on the basis of feature identity, but processing of second-order configural information is most compromised due to their left pFG lesion.
Affiliation: Research Centre in Brain and Behaviour, Liverpool John Moores University, UK.Show MeSH
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Mentions: The cohort comprised of nine patients recruited from local NHS speech and language therapy services in the United Kingdom (UK) and a further 10 patients through collaboration with the University of Arizona (AZ). The study was approved by the local NRES committee in the UK and Institutional Review Board of the University of Arizona, and informed consent was obtained in all cases. To explore the impact of severity upon performance, it was necessary to recruit a broad range of patients using both behavioural and lesion criteria. Therefore, inclusion was based on neuroradiological evidence of damage to left ventral occipito-temporal cortex and/or a reading deficit characterised by an abnormally strong effect of length on reading speed. There was a range of severity among the recruited patients as measured by reading speed on a subset of the 3, 4, 5, and 6 letter word lists developed by Weekes (1997). For measuring correct RTs in tasks requiring a spoken response (e.g., reading, face identification), RTs were measured in the AZ patients using a voice key. For the (typically more severe) UK patients, RTs were established offline via a digital recording of each experimental trial using WavePad software (NCH, Swiftsound: www.nch.com.au/wavepad). The reading of a number of these UK patients was characterised by overt letter-by-letter identification of some letters in the string, and hence a voicekey would have produced inaccurate reaction times corresponding to identification of first letter. The waveforms of the sound files for each patient were inspected to derive a latency from the onset of stimulus presentation (indicated by a short 50 msec beep) to the onset of the correct reading response for that word. Given that PA is characterised by the abnormal length effect as well as slow reading times, we stratified our patients with left pFG damage according to the slope of their length effect, as computed over their average correct reaction times for 3, 4, 5 and 6 letter words (after Roberts et al., 2013). The results are shown in Fig. 1A (raw individual patient RT and accuracy data are provided in Supplementary Materials). The sample was split into two severity-based subgroups on the basis of the slope of their length effect in RT: a mild-moderate group of 10 patients and a severe group of nine patients. The average reading speed as a function of word length for each group is summarised in Fig. 1B.
Affiliation: Research Centre in Brain and Behaviour, Liverpool John Moores University, UK.