情緒閱讀中跨左右半腦處理的電生理證據

Abstract

情緒深受情境的影響。在閱讀過程中，情緒處理是由詞彙項目與前導語境共同建構的。尤其，由語言營造出來的情緒語境會誘發額外的注意力及評估機制以處理詞彙，這超越了僅由詞彙本身情緒性所引發的即時反應。然而，不同腦區如何協同合作以產生這些情緒反應，其機制仍不甚明瞭。研究顯示，儘管左右半腦皆參與情緒處理，左半腦在擷取句子整體語境意涵並促進後續詞彙處理方面，扮演較為重要的角色。這引發一項關鍵的實證問題，即在閱讀過程中，情境化的情緒反應是如何在左右半腦產生的。為此，本研究透過操作語境與句末目標詞的情緒性，產生四種句子類型：（1）情緒語境搭配情緒詞;（2）情緒語境搭配中性詞;（3）中性語境搭配情緒詞;（4）中性語境搭配中性詞。此外，本研究採用分視野呈現法（visual hemi-field presentation method），即句子語境以逐字方式顯示於螢幕中央，而句末目標詞則呈現在右視野（RVF）或左視野（LVF），分別優先由左半腦（LH）或右半腦（RH）處理。受試者需靜默閱讀句子，然後對句子進行情緒向性（valence）的判斷。本研究於臺北招募40位臺灣華語的年輕母語者（20名男性、20名女性，平均年齡23歲，年齡範圍20-29歲），並收集其事件相關電位（Event-Related Potential, ERP）數據。行為結果顯示，無論目標詞呈現在左視野或右視野，情緒性結尾詞與情緒性語境皆提升了判斷該句子具情緒性的比率，顯示雙半腦皆參與情緒評估與情感判斷。ERP結果也支持此發現，呈現出情境化情緒處理的雙側化反應。具體而言，無論目標詞呈現於哪一視野，當情緒詞出現在情緒語境之後時，會引發較中性詞更正向的晚期正波反應（LPP，600–900 毫秒）。儘管情緒處理涉及雙半腦，我們的結果指出在情緒預期上，大腦仍展現出偏側化的功能分工。具體而言，我們的結果顯示，當目標詞出現在左視野（由右半腦優先處理）時，情緒上出乎預期的詞語會在前額區域引發比情緒預期一致的詞語更強的正向反應。整體而言，我們的發現呼應既有研究，顯示情緒是由情緒詞彙與其前導語境共同構成的，且讀者在閱讀中會主動預期即將出現的情緒。在此基礎上，我們的研究進一步擴展相關文獻，顯示左右半腦皆參與整體情緒訊息的處理，而右半腦則對情緒預期的違反更為敏銳。

Emotion is deeply influenced by context. During reading, emotional processing is co-constructed by lexical elements and their prior context. Notably, emotional context in language induces additional evaluative and attentional mechanisms during word processing, beyond the immediate effects driven solely by the emotionality of the words themselves. However, the mechanisms by which different brain systems collaborate to elicit these emotional responses remain poorly understood. Research has shown that although both hemispheres are involved in emotional processing, the left hemisphere is especially effective at extracting the overall contextual meaning of a sentence, which in turn supports subsequent lexical processing. This raises a key empirical issue about how contextualized emotional responses arise across both hemispheres during reading. Our study addressed this by varying both the emotionality of the context and the sentence-final target word, resulting in four sentence types: (1) emotional contexts concluding with emotional words, (2) emotional contexts concluding with neutral words, (3) neutral contexts concluding with emotional words, and (4) neutral contexts concluding with neutral words. Furthermore, we adopted the visual hemi-field presentation method. Sentence contexts were presented one word at a time in the center of the screen, whereas the sentence-final target words appeared either in the right visual field (RVF) or the left visual field (LVF), preferentially processed by the left hemisphere (LH) and right hemisphere (RH), respectively. Participants silently read each sentence and then rated its emotional valence. Event-related potentials (ERPs) were collected from 40 young native Taiwan Mandarin speakers in Taipei (20 males, 20 females; Mage = 23 years, age range 20–29 years). Behavioral results showed that, for both VF presentations, both the emotional ending word and the emotional leading context contributed to higher overall valence judgment rates. These results suggest bilateral involvement in emotional assessment and affective appraisal. Corroborating this finding, ERP results also showed bilateral responses to contextualized emotional processing. Specifically, with both VF presentations, emotional ending words elicited more positive LPP responses (600–900 ms) than neutral words only when following an emotional context. Despite bilateral involvement in emotional processing, our results indicated a functional asymmetry in emotion anticipation. Specifically, our results demonstrated that emotionally unpredicted words triggered more positive responses over anterior regions compared to emotionally predicted words, only with the LVF/RH presentation. Overall, these findings are in line with past findings showing that emotions are co-constructed by the emotional item and its preceding context, and that readers actively anticipate the upcoming emotion. Extending this literature, our findings demonstrated that both hemispheres contribute to processing the overall emotional message, whereas the RH is more attuned to violations of emotional predictions.