ERP face sensitivity onset in a sample of 115 subjects = 92 ms [86, 98] M Bieniek, G Rousselet |
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Institute of Neuroscience and Psychology, University of Glasgow, United Kingdom
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| When does the human visual system detect faces? Several scalp and intracranial recording studies have suggested that activity ~100 ms post-stimulus differentiates between faces and other object categories. However, these results could be compromised by three problems: high-pass filtering at 1 Hz and above, which can smear the onsets back in time (Rousselet, 2012, Frontiers in Psychology, 3:131); lack of control for multiple comparisons; group statistics, which ignore individual differences. Here, we addressed these problems by measuring onsets in every subject after applying a causal Butterworth high-pass filter, which does not distort onsets, and a spatial-temporal percentile-t bootstrap correction for multiple comparisons. A large sample of subjects (n=115), spanning a wide age spectrum (18-81 years old), viewed images of faces and phase-scrambled noise textures. The first significant ERP differences between faces and textures had a median of 92 ms and 95% confidence interval = [86, 98]. These onsets were reliable (test-retest in 80 subjects), without significant group differences between sessions: difference = 2 ms [-11, 14]. These onsets did not change with age, were not affected by low-pass filtering, and were not over-estimated due to possible outliers, as demonstrated by similar results obtained by testing trimmed means instead of means. |
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