腦部影像檢查對憂鬱症的無快樂感釋出一線希望


  May 12, 2008(華盛頓特區) — 國家心智健康研究中心(NIMH)的Wayne C. Drevets醫師在美國精神醫學會第61屆年會的記者會上表示,憂鬱症病患的影像檢查確認腦部迴路異常與無快樂感的症狀有關,這對憂鬱症患者腦部迴路的可塑性帶來一線希望。
  
  他指出,憂鬱症患通常對一些喜悅的刺激不會有所反應,所以他們經常失去激勵和動力,我們有些影像資料顯示可以開始解釋這種缺乏快樂感的機轉。
  
  本研究是憂鬱治療更標靶化的第一步,但同時,我們已經有許多藥物可供使用,如抗憂鬱劑或者心情穩定劑都顯示可以藉由促進腦部的神經滋養素與神經保護因子而有重要的神經可塑效果。
  
  回顧五篇神經影像研究,約有120名憂鬱病患和同等數量的健康對照組,進行激勵處理任務,Drevets博士等人發現,憂鬱病患的酬賞學習路徑有異常(Drevets WC, Furey ML. 情緒異常:憂鬱與腦(Emotional disorders: depression and the brain);登載於Squire等人編輯的 The New Encyclopedia of Neuroscience,第4版,紐約州紐約市: Elsevier出版公司出版中);這些研究使用功能性磁振造影(fMRI)與正子放射斷層掃描(PET),顯示憂鬱病患腦部迴路的神經活動有異常模式,包括腹面紋狀體區域的多巴胺,這會影響腦部的激勵路徑。
  
  研究對象進行「金錢誘因延遲任務」,這之中可以有獲取金錢報酬的能力。
  
  Drevets博士在NIMH舉辦的記者會中表示,最後,健康者和憂鬱病患贏得同樣數量的金錢,但是憂鬱症患者仍舊感到悲傷;事實上,他們在知道要如何處理時感到更糟糕;相對的,這些資訊對健康者的心情或表現沒有影響;此外,當研究對象接受獎勵,健康者的腦部釋出多巴胺,憂鬱者則沒有。
  
  腦部掃描發現,當憂鬱病患知道他們的表現被追蹤且他們有機會贏錢時,他們做得更糟糕且杏仁核增加活性;杏仁核是腦中和恐懼等情緒有關的區域。
  
  Drevets博士表示,憂鬱病患腦中贏錢的潛在喜悅看似被忽略,而聚焦在可能失敗所引起的不悅情緒上。
  
  【作為診斷工具則為時尚早】
  Drevets博士表示,不幸的,影像檢查發現還沒有敏感性和專一性,仍無法用來作為診斷工具;舉例來說,血糖400 mg/dL很明顯超過正常範圍,而憂鬱症和雙極異常的影像檢查仍屬初步,這些疾病的正常和不正常影像還沒有明確的建立。
  
  Drevets 醫師表示他沒有資金往來需要宣告。
  
  美國精神醫學會第161屆年會:研討會 35。2008年5月3-8日。

Brain Imaging Studies Shed Lig

By Marlene Busko
Medscape Medical News

May 12, 2008 (Washington, DC) — Imaging studies of patients with depression have identified brain-circuit abnormalities that correlated with symptoms of anhedonia and have shed light on the plasticity of brain circuits in depression, Wayne C. Drevets, MD, from the National Institute of Mental Health (NIMH), in Bethesda, Maryland, said in a press conference at the American Psychiatric Association 61st Annual Meeting.

"People with depression have an inability to experience usually rewarding stimuli as being pleasurable, and so they often lose incentive and motivation, and we?.?.?.?show some imaging data that begin to account for the mechanisms that explain [this lack of pleasure, or anhedonia]," he noted.

This research is a first step in the development of more targeted treatments for depression, but in the meantime "many of the drugs that we already have available?.?.?.?as antidepressants or mood stabilizers are being shown to have important neuroplastic effects by way of enhancing neurotropic factors and neuroprotective factors in the brain," he told Medscape Psychiatry.

In a review of 5 neuroimaging studies done in about 120 depressed patients and a similar number of healthy patients while they performed reward processing tasks, Dr. Drevets and colleagues found that the depressed patients had abnormalities in their "reward-learning pathway" (Drevets WC, Furey ML. Emotional disorders: depression and the brain. In: Squire L et al, eds. The New Encyclopedia of Neuroscience. 4th ed. New York, NY: Elsevier Publishing, in press.) The studies, using functional magnetic resonance imaging (fMRI) and positive emission tomography (PET), showed that the depressed patients had abnormal patterns of neural activity in brain circuits that involve dopamine in the ventral striatal region, which has been implicated in the brain's reward pathway.

Study participants performed a "monetary incentive delay task," in which they had the ability to win money.

"In the end, healthy and depressed people won the same amounts of money, but people in the depressed group still felt bad," Dr. Drevets said in a press release issued by the NIMH. "They felt and did worse, in fact, when informed how they were doing. By contrast, such information had no effect on the mood or performance of healthy subjects. In addition, as the subjects received rewards, dopamine was released in the brains of healthy individuals, but not in depressed individuals."

Brain scans revealed that when the depressed patients knew their performance was being tracked and they had the opportunity to win money, they did worse on the tasks and had an increase in activity in the amygdala, a brain region associated with emotions such as fear.

The brains of the depressed patients "seem to pass over the potential pleasure of winning money to focus on unpleasant emotions caused by the potential for failure," said Dr. Drevets.

Too Early for Use as a Diagnostic Tool

"Unfortunately, the imaging findings typically don’t show the sensitivity and specificity that one would need to use them as a diagnostic tool," Dr. Drevets cautioned. For example, a blood sugar of 400 mg/dL is clearly outside the normal range, he added, whereas since imaging studies of depression and bipolar disorder are still in their infancy, there are no well-established normal vs abnormal imaging findings for these disorders.

Dr. Drevets has indicated that he has no significant financial relationships to disclose.

American Psychiatric Association 161st Annual Meeting: Symposium 35. May 3-8, 2008.

    
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