功能性磁振造影對於偵測血動力學反應有很高的空間及時間解析度，功能性磁振造影和心理物理學上的參數作相關聯將更有能力了解神經活動過程。本研究的目的是為了要觀察檢驗功能性磁振造影反應的參數是如何隨著行為結果的測量值( 例如: 反應時間) 而改變。我們利用兩種不同頻率的真字及假字作為材料來進行字彙判斷作業，造成不同的反應時間，去探討其中的關係。在左腦下額葉區域，對於高頻字其活化體積小於低頻字與假字(587 ±261 vs. 3280 ±822立方厘米, 587 ±261 vs. 2025 ±548 立方厘米 )，和反應時間有很好的相關性(417 ±9 vs. 631 ±22 毫秒, 417 ±9 vs. 658 ±15 毫秒 )。在左腦下額葉區域，觀察到反應時間和功能性磁振造影反應中的全寬半高有線性關係(p<0.001)。而在反應時間和血動力學反應的起始時間並沒有顯著的相關性。這個發現意味著當執行字彙判斷作業時，左腦下額葉區域在反應時間中持續地活化。相對地，在作業結束後，與按鈕動作反應相關的左腦主要運動皮質區，其功能性磁振造影反應中的全寬半高和反應時間並無相關性。我們的結果也與字彙判斷作業的功能模式相符。因此，在認知過程中不同的神經活動可以經由功能性磁振造影血動力學反應被偵測到而加以區別。在此次研究中，我們證明了時間解析的功能性磁振造影技術的能力，即使反應時間在數百毫秒的認知事件，也能藉由追蹤功能性磁振造影反應而加以探討開發。

Functional magnetic resonance imaging (fMRI) detects hemodynamic responses with high spatial and temporal resolution. Capabilities of correlating psychophysical parameters with fMRI allow a better understanding of the neuronal processes. The objective of this study is to examine how fMRI BOLD response parameters vary with behavioral outcome measures (e.g. reaction time). We utilized a lexical decision task with two character-frequency levels and pseudocharaters. In the left inferior frontal lobe, the activation volumes were smaller to high-frequency characters than to low-frequency characters and pseudocharacters (587±261 vs. 3280±822 mm3, 587±261 vs. 2025±548 mm3 ), which is correlated well with the reaction times (417±9 vs. 631±22 ms, 417±9 vs. 658±15 ms ). The linear correlation between the measured reaction times and FWHM (full width half maximum) of the fMRI responses was also observed in the left inferior frontal lobe (p＜0.001). There was no significant correlation between reaction time and onset time of the hemodynamic response. These findings imply left inferior frontal lobe is active during the entire reaction time when executing the lexical decision task. Conversely, the FWHM of fMRI responses in the left primary motor cortex (M1) related to pressing a button for responding at the end of task is not correlated to reaction time. Our results are also coherent with respect to a functional model of lexical decision task. Thus, the different patterns of neuronal activity during the cognitive process could be detected and distinguished through the fMRI hemodynamic responses. In this study, we have demonstrated that the time-resolved fMRI technique has the capacity to exploit the cognitive events by tracing in the temporal responses of fMRI, even if the reaction time is at the time scale of hundred milliseconds.

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