International Journal of Bioelectromagnetism www.ijbem.org Vol. 9, No. 4 pp.245 - 248, 2007 Visual Field Influences Functional Connectivity Pattern in a Face Affect Recognition Task Lichan Liu a , Konstantinos Arfanakis b and Andreas A. Ioannides a a Lab. For Human Brain Dynamics, RIKEN Brain Science Institute, 2-1 Hirosawa, Wakoshi, Saitama, Japan 3510198 b Department of Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, USA Correspondence: Lichan Liu. E-mail: lichan@brain.riken.jp, phone +81 48 467 7218, fax +81 48 467 9731 Abstract. We studied MEG responses in humans to centrally and peripherally presented face stimuli to test the hypothesis that different visual field locations may be associated with different types of processing, possibly utilizing different white matter pathways between striate and extrastriate areas. Functional and structural connectivity between V1/V2 and the fusiform area specializing for faces were examined using mutual information and diffusion tensor imaging. We observed distinct connectivity patterns when facial images were presented at the fovea or one of the quadrants and demonstrated early extrastriate activation leading striate activation for upper visual field stimulation. Keywords: MEG; Connectivity; Face Processing; Fusiform; V1/V2; Mutual Information; Diffusion Tensor Imaging 1. Introduction It is well established that visual stimuli presented in one part of the visual field are projected to the contralateral part of the visual cortex such that images presented in the right visual field are projected to the left visual cortex. It is however unclear whether stimuli presented in different parts of the visual field are processed differently in extrastriate areas and whether different white matter pathways between striate and extrastriate areas are involved when stimuli are presented to different quadrants. Here we studied MEG responses in humans to centrally and peripherally presented face stimuli to contrast the processing of faces when the images are presented at the center and periphery of the visual field. 2. Material and Methods Seven healthy right-handed male subjects (mean age 32) participated in a face-affect recognition experiment in which they viewed stimuli of happy, fearful and neutral faces selected from Ekman and Friesen’s Pictures of Facial Affect. We used a block design for presenting the images in different parts of the visual field: the images appeared at one of the five positions (center or quadrants) on the screen, fixed for each run. Each run consisted of 30 images. Each image was shown for 500 ms and one second later an option list of the emotions was shown for three seconds. Subjects named the emotion verbally as soon as the list appeared. Three runs for each of the five image positions were recorded. The run order was randomized and counter-balanced across subjects. Two baseline runs were also recorded for each subject, one before and one after the task runs. In these two control runs, subjects were in place with the same luminosity and fixation cross on the screen as in the task runs. We recorded MEG signals using the CTF/VMS whole head 151-channel system. The MEG signal was recorded in epoch mode as a 5-second segment beginning from 500 ms before to 4.5 sec after each image onset. The recording was made with a low-pass filtering at 200 Hz and sampling at 625 Hz. The MEG signal was filtered in the 3-200 Hz band. To capture early fast responses, we used a 200 Hz upper bound, considerably higher than that in most MEG and EEG studies of face processing. We used magnetic field tomography (MFT) [Ioannides et al., 1990], a non-linear distributed source method, to extract tomographic estimates of brain activity millisecond by millisecond from the MEG signal. We then used statistical parametric mapping (SPM) to identify brain areas and latencies when the activity was significantly different between task and control conditions. Finally, we examined functional and anatomic connectivity between brain regions using mutual information [Ioannides et al., 245