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Ali Hashemi, Matthew V. Pachai, Patrick J. Bennett, Allison B. Sekuler; Exploring the relationship between the N170 inversion effect and horizontal tuning. Journal of Vision 2012;12(9):624. doi: 10.1167/12.9.624.
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Recent research suggests that faces contain the most information in the horizontal orientation band (Dakin & Watt, J Vis 2009), and the size of the behavioural face inversion effect (bFIE) is correlated with changes in horizontal tuning following inversion (Pachai et al., VSS 2011). Moreover, ERP studies have shown that 1) the N170 is delayed and sometimes increased in amplitude following inversion, 2) the N170 and bFIE are correlated (Jacques and Rossion, NeuroImage 2007), and 3) the N170 inversion effect decreases when horizontal information is scrambled (Jacques et al., VSS 2011). However, the question remains whether the N170 is associated with horizontal tuning, and how that association varies with face inversion. To answer these questions, observers completed a 10AFC identification task using filtered faces. In the full-face condition, faces contained information at all orientations. In the horizontal/vertical conditions, target face information was contained only in orientations within ±35 deg of horizontal/vertical; remaining orientations contained non-informative face information, so stimuli were face-like in all conditions. Initial results from 8 observers, show a bFIE only in the full-face and horizontal conditions. N170 latency, but not amplitude, depended on both orientation filtering and face orientation. Specifically, face inversion increased latency equivalently across filter conditions, whereas latency for upright faces depended on orientation filtering, with the shortest and longest latencies occurring in the full-face and vertical conditions, respectively. When we examined the relationship between the N170 inversion effect for full-faces and the change in behavioural horizontal tuning (horizontal – vertical) following inversion, we found a positive correlation for both latency (r=0.78) and amplitude (r=0.56). To date, our findings reinforce the notion that upright face identification is driven by increased efficiency in processing horizontal face information compared to vertical, and suggest an association between changes in this efficiency following inversion with changes in the N170.
Meeting abstract presented at VSS 2012
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