探討視覺區血氧訊號變化的非線性程度

Abstract

本實驗主要探討視覺皮質區血氧訊號變化的線性程度。透過不同視覺刺激長度以獲得不同的血氧訊號變化，用短刺激所誘發的血氧訊號變化來預測長刺激誘發的血氧訊號變化，藉由預測的準確度來判定視覺皮質區血氧訊號變化的線性程度。 實驗結果顯示，在刺激長度小於四秒的情況下，視覺皮質區的血氧訊號變化非線性，此一結果影響我們選擇用何種方法來分析短刺激功能性磁振造影的結果。本文也討論了血氧訊號變化在不同反應區裡有何不同。

Hemodynamic responses to visual stimulation were assessed for nonlinearity in short stimulation duration. Four stimulation durations were used (1, 2, 4, and 8 sec), and 9 subjects were scanned to verify the nonlinear BOLD responses in visual cortex. The test of nonlinearity consisted of using BOLD responses due to short stimulation durations to predict responses due to long stimulation durations. The results show the hemodynamic response is nonlinear for stimulation duration less than 4 sec in the visual cortex. In addition, the shape of hemodynamic response function influenced by the choice of region-of-interest was discussed.