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| 題名: | 以毛筆筆刷、手掌觸摸、和指尖輕點的觸覺刺激探討情動觸摸所引 發的theta 頻段腦波強度變化;The Changes in EEG Theta Oscillation Induced by Affective Touch: Comparing Brush Stroke, Hand Stroke, and Massage-like Tapping |
| 作者: | 王永安;Wang, Yung-An |
| 貢獻者: | 認知與神經科學研究所 |
| 關鍵詞: | 情動觸摸;社會觸摸;按摩;社會互動;體感覺皮質區;theta 頻段;affective touch;social touch;massage;social interactions;somatosensory;theta oscillation |
| 日期: | 2023-05-12 |
| 上傳時間: | 2024-09-19 16:55:40 (UTC+8) |
| 出版者: | 國立中央大學 |
| 摘要: | 本研究利用不同的觸摸變項（毛筆筆刷、手掌觸摸、和指尖輕點的情動觸摸），探討情動神經傳導（affective/CT afferent）是否僅回應緩慢而輕柔（slow, gentle, and lowforce）的毛刷觸碰（stroke with brush），進而產生愉悅感（hedonic feeling）；以及透過腦電波在不同觸摸條件操弄前後，所產生不同頻段的神經電生理變化。在過往研究中，多
數使用fMRI 造影方法來探討情動神經傳導的活化腦區，發現情動神經傳導（affective/CT afferent）的活化路徑包含了眼窩前額皮質（orbitofrontal cortex）或腦島皮質（insular cortex）區域、但卻排除了體感覺皮質區（primary somatosensory cortex，SI）及次級體感覺皮質區（secondary somatosensory cortex， SII）的活化，進而確立情動觸摸（affectivetouch/CT touch）係透過CT 神經傳導路徑來建構愉悅的感覺。然而，近年透過脊髓切斷術（cordotomy）進行情動觸覺刺激的愉悅評分，發現術前術後以及與對照組比較，並沒有愉悅度的改變。因此情動傳導（affective/CT afferent）或許並非如二分化神經傳導路徑（dual pathway）推論，擁有與辨識性傳導（A-beta afferent）不同的傳導路徑，而是中繼在（rely）與體感體相關的辨識性傳導路徑，並針對刺激本身進行愉悅度的判斷。有鑑於此，我們欲探討情動觸摸與辨識性觸摸所引發的theta 頻段腦波強度變化，比較兩者神經傳導路徑與愉悅度的不同。
本次實驗中包含了一個學習閉眼按鍵評分與三個觸摸實驗。在學習階段，受試者允許睜開眼睛，練習記憶按鍵位置，評分文字描述的觸覺速度與觸摸方式。在測試階段，我們分別測試了三種不同的觸摸條件─毛筆筆刷、手掌觸摸、指尖輕點，測試受試者在閉眼情況下，其主觀愉悅評分與其電生理的EEG 反應。三個不同的觸摸實驗分別以兩種不同的刺激速度（5 cm/s CT-optimal velocity 與18 cm/s CT-suboptimal velocity）進行。在各種不同的刺激條件之後，我們分別對愉悅程度進行評分，並以雙因子變異數分析及事後檢定加以分析。結果發現刺激的速度並沒有顯著影響愉悅程度，而觸摸方式間，則存在顯著的愉悅程度差異，其中以手掌慢摸是最愉悅的觸摸方式。神經電生理的部份我們利用時頻分析(time-frequency analysis)的方式，找出刺激前後具有顯著差異的通道位置及頻段，再透
過濾波—希爾伯特轉換(filter-Hilbert transform)，我們對theta 波段進行了有與無考量時序列的統計比較。僅有考量時間序列的統計結果顯著，並且我們發現了與過往實驗相似的結果，進一步找出手掌撫摸不僅在FP1 電極位置具有顯著刺激前後theta 波段的增強，同時在CP4 電極位置也發現了刺激前後具有顯著theta 波段的增強。相對而言，毛筆輕刷僅有
在FP1 電極位置有顯著的theta 強度變化，在反應體感覺相關皮質區的電極位置則沒有找到任何顯著的跡象；手指點摸在較多的電極位置上，呈現theta 頻段的顯著變化，包含接近前額皮質（frontal cortex）的FP1 電極位置在內，可能也包括了CT 神經傳導活化的觸發。
綜合本次實驗內容與近年的情動觸摸研究成果顯示，典型情動觸摸的二分化神經傳導路徑理論，或許已不足以清楚的區別情動傳導與辨識性傳導。同時，我們的研究結果發現，機械性的手指輕點也可能同時活化代表CT 神經傳導路徑的FP1 電極位置以及代表體感覺皮質區的CP4 電極位置，但愉悅的反應卻是幾種不同刺激手法中最低的；與毛筆筆刷同屬情動觸摸的手掌觸摸，確實能夠引發略高於毛筆筆刷的愉悅反應，卻也同時活化代表體感覺皮質區的CP4 電極位置。由此結果，我們推論情動觸摸的反應，可能是自上而下（top-down）的認知機制優先於機械性的輸入特性，並對該觸摸進行愉悅評斷。;This study compares psychophysical and EEG responses to 3 types of tactile stimulation (brush stroke, hand stroke, and massage-like tapping) to investigate whether affective afferent only response to slow, gentle brush stroke. The classical definition of affective touch involves CT afferent and A-beta afferent pathways, with the CT pathway characterized by activation in the orbitofrontal and insular cortex and deactivation in the primary (SI) and secondary
somatosensory cortex (SII). However, recent evidence showed that the spinothalamic ablation in humans does not make difference in rating the pleasantness of the CT touch paradigm before and after cordotomy, and even, compared to the control groups (Marshall et al., 2019). Therefore, the
current study has investigated if the properties of the tactile information were judged while relying on ascending A-beta low threshold mechanoreceptor afferent inputs in affective touch using EEG theta oscillation.
This study involved a learning phase followed by three test phases. Participants were asked to memorize button locations and practice rating hedonic responses during the learning
phase with open eyes. During the test phase, participants closed their eyes and rated with brush stroke, hand stroke, and massage-like tapping with two velocities (CT-optimal 5 cm/s and CTsuboptimal 18 cm/s, 3 styles x 2 velocities). We investigated theta oscillations in EEG analysis and replicated previous findings in affective touch. Specifically, we performed a time-frequency analysis to identify channels and frequency bands showing significant differences in power before and after each tactile stimulation style and velocity. Once we identified these frequency bands, we applied a filter-Hilbert transform to calculate the instantaneous power of the selected
bands for statistical comparison. We compared the EEG theta power before and after tactile stimulation, considering the temporal sequence of theta power bands, and found significant differences only when accounting for temporal sequence. The hand stroke with CT-optimal velocity was rated as the most pleasant touch condition. EEG analysis focused on the theta oscillation changes which were associated with the most pleasant hand stroke in both FP1 and CP4 channels. Brush stroke only showed significant theta oscillation increases in the FP1 channel, while massage-like tapping showed significant changes across most channels, including
FP1, indicating activation close to the orbitofrontal cortex.
This study, along with previous research on affective touch, suggests that the "dual pathway" theory may not provide a complete understanding of how affective and discriminative afferent respond to different types of tactile stimulation. Our results showed that changes in the
theta oscillations, resulting from the least pleasant massage-like tapping, could be found across multiple channels, including FP1 and CP4, indicating that mechanic touch may induce responses beyond the somatosensory cortex. The hand stroke condition, which facilitated comparable hedonic ratings as the brush stroke, also induced significant theta oscillations at FP1 and CP4 channels, potentially reflecting activation close to the somatosensory cortex and the orbitofrontal cortex. Together, these findings indicate that affective and discriminative touch cannot be dissociated by CT-afferent activation.
Consequently, affective touch may be primarily determined by a top-down cognitive mechanism, making it a higher-order process than just processing the mechanical characteristics of touch. |
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