title: A robust and representative lower bound on object processing speed in humans.
abstract: How early does the brain decode object categories? Addressing this question is critical to constrain the type of neuronal architecture supporting object categorization. In this context, much effort has been devoted to estimating face processing speed. With onsets estimated from 50 to 150 ms, the timing of the first face-sensitive responses in humans remains controversial. This controversy is due partially to the susceptibility of dynamic brain measurements to filtering distortions and analysis issues. Here, using distributions of single-trial event-related potentials (ERPs), causal filtering, statistical analyses at all electrodes and time points, and effective correction for multiple comparisons, we present evidence that the earliest categorical differences start around 90 ms following stimulus presentation. These results were obtained from a representative group of 120 participants, aged 18-81, who categorized images of faces and noise textures. The results were reliable across testing days, as determined by test-retest assessment in 74 of the participants. Furthermore, a control experiment showed similar ERP onsets for contrasts involving images of houses or white noise. Face onsets did not change with age, suggesting that face sensitivity occurs within 100 ms across the adult lifespan. Finally, the simplicity of the face-texture contrast, and the dominant midline distribution of the effects, suggest the face responses were evoked by relatively simple image properties and are not face specific. Our results provide a new lower benchmark for the earliest neuronal responses to complex objects in the human visual system.
authors.affiliation: Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, 58 Hillhead Street, Glasgow, G12 8QB, UK.
authors.forename: Magdalena M
authors.initials: MM
authors.lastname: Bieniek
authors.affiliation: Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Bennett
authors.affiliation: Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada.
authors.forename: Allison B
authors.initials: AB
authors.lastname: Sekuler
authors.affiliation: Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, 58 Hillhead Street, Glasgow, G12 8QB, UK.
authors.forename: Guillaume A
authors.initials: GA
authors.lastname: Rousselet
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000254:growth & development / Q000502:physiology; D005071:Evoked Potentials; D000066499:Facial Recognition; D006801:Humans; D008875:Middle Aged; D011930:Reaction Time
keywords: ageing; face processing; object processing; processing speed; visual evoked potentials