Naslov
Onset of the fusiform area MEG activity evoked by upright and inverted faces

Autori
Sušac, Ana ; Ilmoniemi, Risto ; Ranken, Doug ; Supek, Selma

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
12th Annual Meeting of the Organization for Human Brain Mapping ; NeuroImage, Volume 31, Supplement 1 / Corbetta, Maurizio ; Nichols, Thomas ; Pietrini, Pietro - : Academic Press, 2006

Skup
12th Annual Meeting of the Organization for Human Brain Mapping

Mjesto i datum
Firenca, Italija, 11.06.2006. - 15.06.2006

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
magnetoencephalography; spatio-temporal analysis; face processing; fusiform area

Sažetak
Introduction Facial stimuli elicit an N170 ERP/ERF component. Spatio-temporal source localization of MEG data (e.g., [1, 2, 3]) confirmed the activation of the fusiform area (FFA) known from fMRI studies to be involved in face processing. While the localization of the FFA was mostly done at the peak latency around 170 ms, some results suggest that face-specific activity in FFA starts at about 140 ms [2, 3]. Our previous study identified three to four current dipoles during the first 140 ms after the onset of facial stimuli [4]. Liu et al. recently [5] reported a face-selective MEG response elicited only 100 ms after stimulus onset. Their findings were based on data analysis of the MEG responses over the sensors of interests where the magnetic fields evoked by faces were significantly larger than those by houses. The goal of this MEG study was to identify the neural substrate and the dynamics of the early face-specific response, in particular, its onset, and compare it for upright and inverted faces. Methods Eight young male subjects with MRI scans participated in the study. Measurements were carried out at the BioMag Laboratory using a 306-channel VectorView system (Elekta Neuromag Ltd., Finland). Grayscale faces were presented centrally in an oddball paradigm. We analyzed MEG responses to standards in four experimental conditions: 1) happy standard ; 2) neutral standard ; 3) inverted happy standard ; 4) inverted neutral standard. MEG data were analyzed assuming multiple dipoles in a sphere model and using the Cortical Start Spatio-Temporal (CSST) multi-start inverse procedure incorporated in MRIVIEW software [6]. Results Spatio-temporal source analysis indicated the onset of FFA activity about 120 ms and even earlier for some subjects. The reliability of this finding was confirmed by considering a range of different time windows of data submitted to the CSST inverse procedure. Upright faces activated the FFA source earlier than inverted ones. The time-courses of the activated FFA sources were similar for happy standard and neutral standard stimuli (conditions 1 and 2), whereas they were different for inverted faces. This is in agreement with the conclusion from the previous MEG/EEG study on face inversion effect [3] that differences in processing of upright and inverted faces come from temporal processing differences rather than shifts in locations of the activated brain regions. Conclusion Spatio-temporal analysis of our neuromagnetic data confirmed an early onset of the FFA source activity and its dependence on the face orientation suggesting that face processing could start as early as 100-120 ms. References [1] Linkenkaer-Hansen K, Palva JM, Sams M, Hietanen JK, Aronen HJ, Ilmoniemi RJ. Neuroscience Letters. 1998, 253:147-150. [2] Halgren E, Raij T, Marinkovic K, Jousmäki V, Hari R. Cereb Cortex. 2000, 10:69-81. [3] Watanabe S, Kakigi R, Puce A. Neuroscience. 2003, 116:879-895. [4] Susac A, Ilmoniemi RJ, Supek S. Proceedings of Biomag 2004, 445-446. [5] Liu J, Harris A, Kanwisher N. Nature Neuroscience 2002, 5:910-916. [6] Ranken DM, Best ED, Stephen JM, Schmidt DM, George JS, Wood CC, Huang M. Proceedings of Biomag 2002, 785-787.

Izvorni jezik
Engleski

Znanstvena područja
Fizika

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