語文笑話的認知與情緒歷程：功能性磁振造影研究

Abstract

不論是古今或中外，幽默在人類的生理健康、心理調適和社交上，皆扮演重要的角色。因此，探討幽默歷程及其神經機制的研究蔚為風氣。近年來，先進的功能性磁振造影技術已經促使研究者以更有效的方法探討幽默歷程的大腦神經機制。過去的幽默研究，發現大腦進行幽默理解和幽默欣賞時，分別對應到不同的腦區。然而上述這些研究，大多以「幽默」和「非幽默」的條件相比，故其大腦的活化同時混雜著幽默的認知和情緒歷程，無法明確區分幽默理解的認知歷程與幽默欣賞的情緒成份之神經機制。因此，本研究採用過去幽默研究從未使用的實驗設計，在笑話語句與一般句之外，加入「花園路徑句」條件，以區分幽默的「認知成份」和「情緒成份」的神經機制。 此外，幽默的認知歷程可再細分為「失諧」和「解困」的歷程，然而過去的研究囿於刺激材料和實驗設計的限制，無法明確區分失諧與解困歷程所對應的神經機制。因此，本研究採用語文笑話，並改寫關鍵語句來操弄三種刺激類型：未失諧、失諧未解困、失諧解困。經由上述三類刺激的比較，可以更精細區分「失諧」和「解困」認知歷程的神經機制。 本研究以事件關聯功能性磁振造影技術進行兩個實驗，實驗一旨在區分笑話中「認知成份」和「情緒成份」的神經機制，結果發現，幽默的認知成份引發語義統整在左側額上回和雙側的額下回有較大的活化。在故事主角的人格特質推論下有較大活化在左側角回、左側額上回、雙側顳下回和右側顳中回；在解困後，引發好笑愉悅的幽默情緒成份在海馬旁回和前扣帶回有較大的活化。 實驗二將幽默認知歷程再細分為「失諧」和「解困」，旨在探討這兩個認知歷程的神經機制。結果發現，「失諧」歷程在右側顳中回有較大的活化。「解困」歷程在左側額上回及左側頂下葉有較大的活化。 綜上所述，相較於過去的幽默研究，本研究的實驗設計有所突破，更能釐清且區分幽默的「認知成份」與「情緒成份」之神經機制，且在幽默理解可再區分出「失諧」和「解困」的歷程，對於瞭解幽默的神經機制具有重大的貢獻。未來研究可再進一步比較幽默與情緒調節的效果。其次，本研究採用二段式笑話結構，未來可直接使用三段式笑話結構，從刺激材料更能清楚區分失諧和解困的歷程。再者，本研究的參與者皆為一般正常人，未來可和不同族群進行比較，例如：比較一般生與亞斯伯格者在笑話中認知與情緒歷程之神經運作機制。 Humor plays a crucial role in the physical, psychological, and social well-being of all human beings, regardless of time and place. Consequently, extensive research and experimentation has been performed focusing on comprehending the humor process and its neural substrates. In recent years, technical advances in functional magnetic resonance imaging (fMRI) have enabled researchers to more effectively investigate the neural substrates of humor processing. Previous studies have discovered that humor comprehension and humor appreciation appear to be managed by different brain regions. However, most of the preceding studies have explored this topic by contrasting “funny” and “unfunny” conditions. These two conditions both activate brain regions involved with the processing of the cognitive and emotional aspects of humor and thus do not allow for the identification of the distinct neural substrates underlying each of these taken as separate sets of processes. To overcome this difficulty, this study was the first to adapt an experimental designed to identify the distinct neural substrates of cognitive and emotional processing. This is done through the incorporation of a “garden path sentence”. A further obstacle encountered in the previous research is that it has been difficult to clearly identify the neural substrates contributing to the subdivision of “incongruity” detection and “resolution.” To further investigate this, this present study rewrote the punch lines of verbal jokes to generate stimuli jokes of three types: incongruity-removed (unfunny), resolution-removed (nonsensical), and incongruous resolution jokes (funny). By contrasting the results from these three types, it was possible to clearly identify the neural substrates of the cognitive processes associated with incongruity detection and resolution. The purpose of experiment 1 was to identify the distinct neural substrates associated with cognitive processing and emotional processing. The comprehension-elaboration theory of humor claims that the elicitation of humor can be segregated into two stages, comprehension and elaboration. Comprehension includes detection and resolution of incongruity, and elaboration involves inferences concerning the agents and objects in the story and inducement of the experience of amusement. Previous imaging research has sought to identify the neural substrates of humor processing by comparing funny and unfunny conditions. However, such studies have not been able to segregate the comprehension and elaboration stages. The present study was designed to differentiate the respective brain areas corresponding to comprehension and elaboration with an additional condition, garden path sentences.The results suggest that the left superior frontal gyrus (SFG), bilateral inferior frontal gyri (IFG), and caudate may be associated with humor comprehension, whereas the left angular gyrus, left SFG, bilateral inferior temporal gyri (ITG), and right middle temporal gyrus (MTG) may be responsible for personality-related inferences during the elaboration process. In addition, the feeling of amusement appears to be associated with increased activity in a network of subcortical regions, including the parahippocampal gyrus and anterior cingulate cortex (ACC). The target of experiment 2 was to further distinguish neural substrates in the cognitive processing of the detection and the resolution of incongruities. The incongruity-resolution theory states that joke comprehension consists of two stages: incongruity detection and incongruity resolution. However, few fMRI studies on joke comprehension have examined the differential neurological substrates of humor processing for these two stages. The present study utilized an event-related fMRI design incorporating three conditions (funny, unfunny, and nonsensical) to examine distinct brain regions associated with the detection and the resolution of incongruities. Stimuli in the funny condition contained resolvable incongruities; stimuli in the nonsensical condition contained unresolvable incongruities; while stimuli in the unfunny condition contained no incongruities.The results showed that the detection of incongruities was associated with greater activation in the right MTG, and the resolution of incongruities with greater activation in the left SFG and left inferior parietal lobule (IPL). A parametric analysis additionally showed that the ACC was activated in relation to subjective comprehensibility, suggesting a key role in producing the experience of amusement or humor appreciation after humor comprehension. Our findings provide an advanced understanding of the neurological mechanisms of incongruity detection and resolution during humor comprehension. In summary, this study provides a breakthrough in experimental design in humor research, with the potential to allow for the identification of the neural substrates of the cognitive components and emotional components of humor, and the “incongruity” and “resolution” processes associated with humor comprehension. By comparing the neural substrates associated with the processing of jokes, this study also contributes to understanding the neural substrate of humor. It is demonstrated that humor cognition and emotion highly activate distinctive areas in the cortex and subcortex, and by observing changes in the areas activated during shifts of emotional states, we were able to associate humor comprehension and appreciation processes with different brain areas. Extended studies in this topic could be conducted by comparing the effectiveness of humor and emotion regulation. Additionally, this study adopted a two-stage joke structure in the experiment, which could also be replaced with a three-stage joke structure to clearly trace the incongruity and resolution process. Finally, the participants in this study were all ‘normal’ people. The data could thus be used as a baseline against which results from participants with Asperger’s syndrome could be compared to further investigate the neural substrates of cognitive and emotional processing of verbal jokes in different groups.