自閉症患者的不正常腦迦馬振動波

Abstract

研究目的：自閉症類群障礙症或稱泛自閉症障礙是一種神經發展疾病，與γ-氨基丁酸（γ-aminobutyric acid）神經傳導功能有關。感覺處理歷程的異常現象廣泛存在自閉症類群障礙症的患者身上，尤其是在聽知覺處理歷程。γ-氨基丁酸抑制性中介神經元對於腦電圖訊號中在迦瑪頻段的振盪現象之調節及產生，扮演了至關重要的角色。本研究使用病例對照研究，比較自閉症類群障礙症患者與健康受試者，在接受不同頻段聽覺穩態刺激下所產生的腦電圖迦馬頻段的聽覺穩態反應 （auditory steady-state response，簡稱ASSR）。 研究方法：本研究納入五十位自閉症類群障礙症患者（年齡介於6歲至29歲）及四十一位健康受試者（年齡介於6歲至27歲）。受試者個別依序接受出現頻率為二十赫茲、三十赫茲、四十赫茲的單擊音序列聲音刺激。額葉及顳葉的聽覺穩態反應由32顆電極腦波儀帽記錄，並透過時頻分析計算20Hz頻段、30Hz頻段及40Hz頻段的誘發功率（evoked power）及試驗間相位同調性（inter-trial phase coherence）。 結果： 自閉症類群障礙症患者在顳葉區的20Hz頻段誘發功率顯著低於健康受試者，在額葉中線則高於健康受試者；30Hz頻段則在顳葉區域顯著低於健康受試者；但是40Hz頻段的誘發電位在兩組間無顯著差異。自閉症類群障礙症患者的20Hz及30Hz頻段試驗間相位同調性在顳葉顯著低於健康受試者組；然而，在40Hz頻段沒有顯著差異。若將受試者再區分為成人組、青少年組及兒童組，自閉症類群障礙症患者與健康受試者在30Hz頻段及40Hz頻段的誘發功率與及試驗間相位同調性的差異，在兒童組見於兩側額葉，青少年組及成人組則分布於中線或左側額葉的位置。 結論：自閉症類群障礙症患者有迦瑪頻段穩態聽覺反應的缺損，而且年齡與此缺損的腦區有關聯。這提供神經電生理學上的證據支持患者在γ-氨基丁酸神經傳導系統的發展過程有障礙。

Objective: Autism spectrum disorder (ASD) is a neurodevelopmental disorder involving γ-aminobutyric acid (GABA) neurotransmission. Sensory abnormalities, particularly in the auditory modality, are commonly seen in individuals with ASD. Since GABAergic interneurons play a fundamental role in generating neuronal gamma oscillations, this study aims to investigate whether ASD patients have altered auditory steady-state response (ASSR) in gamma-band range. Methods: We recruited 50 patients with ASD and 41 typically developing controls (TDC). The participants were presented three click trains with rates of stimulation at 20-, 30- and 40-Hz, respectively. The frontal and temporal ASSR was recorded through a 32-channel electrode cap. Evoked power and inter-trial phase coherence (ITC) were derived from the electroencephalogram (EEG) signals. Results: In response to 20-Hz click trains, the ASD group showed lower evoked power at 20-Hz band in the temporal area but higher in the midline frontal area, and lower evoked power at the 30-Hz band in the temporal area. The ASD group showed smaller ITC in the temporal area in response to both 20-Hz anda 30-Hz click trains. There were no significant group differences in the 40-Hz band evoked power and the ITC. When participants were divided into the adult, adolescent and childhood subgroups, all the three groups showed significant differences of frontal 40-Hz band evoked power and between ASD patents and TDC participants. The group differences were observed in bilateral frontal regions in childhood subgroup, but shift to the midline and left frontal regions in the adolescent and adult groups. Conclusion: Age is an important factor to be considered when investigating gamma band auditory steady-state response. Deficits in gamma-band ASSR were noted in patients with ASD, and age was related to the distribution of brain regions where these deficits were found. It provides neuroelectrophysiological evidence for the altered development of GABAergic neurotransmission in patients with ASD.