EVENT-RELATED BOLD ACTIVATION OF THE OPTICAL RADIATION
Society for Neuroscience San Diego, November 10-15, 2001 J-R. Duann, T-P. Jung, W.-J. Kuo, T.-C. Yeh,
Scott Makeig, J.-C. Hsieh, T. J. SejnowskiThe Salk Institute and Swartz Center for Computational Neuroscience Institute for Neural Computation University of California San Diego IBRU, Taipei-Veterans General Hospital, Taipei, Taiwan, R.O.C.
Independent Component Analysis (ICA) was applied to the fMRI BOLD time series obtained in event-related fMRI studies (Bruker 3T MR imager, TR=500 ms, TE=70 ms, flip angle = 90 degrees; matrix = 64x64; FOV = 250x250 mm; slice thickness = 5 mm with 2-mm gaps). Six subjects (2 males and 4 females, aged 22 +/- 3 yr) participated in 2 separate sessions each comprising ten 30-sec epochs. Eight-Hz bursts of flickering-checkerboard visual stimulation was presented during the first 0.5 s of each epoch. The obtained event-related fMRI time series data were first subjected to slice-timing adjustment, off-brain removal and principal subspace dimension reduction (to 100 dim.). Infomax ICA (http://www.sccn.ucsd.edu/~scott/ica.html) was then used to segregate the resultant fMRI BOLD signals into task-related brain responses, other brain processes, and machine/environmental noise. For each subject, ICA returned a component active in the optical radiation of the visual pathway, plus one or more components active in the V1 cortices. The time courses of these two component types had different onset latencies and waveforms. The event-related activation of the optical radiation led the activation of the V1 cortices. In addition, optical radiation time course had larger peak-to-peak amplitudes and longer duration, compared to the V1 area. ICA appears to be a powerful and sensitive tool for separating event-related activations in brain processes within small brain areas from complex fMRI time series data.