區辨性增強低頻反應作業 (differential reinforcement of low-rate responding task, DRL task) 為一與時間相關聯之操作式制約行為作業，該作業常用於計時行為、行為抑制功能、或抗焦慮與抗憂鬱症等藥物之行為藥理研究的探討。雖然DRL作業是一種實驗室常用的動物行為模式，但是對於上述行為或藥理機制的探討往往缺乏一致性的解釋，其中可能的原因為DRL作業的行為同時包含了計時與行為抑制的成份。針對上述問題，本研究將以DRL行為作業為研究主題，探討作業習得歷程之神經機制。首先根據DRL作業之行為內涵，將作業的習得分為行為抑制與計時先後表現的兩個階段；並依據過去的研究文獻整理出的八個與行為抑制和計時表現相關之大腦區塊，以c-Fos免疫組織化學染色法探討行為抑制和計時的神經機制。實驗結果發現受試於行為抑制的表現階段，其眶眼皮質、內側前額葉皮質、與海馬CA1區域的c-Fos表現量較高；而在計時行為的表現階段，除了和行為抑制有關的三個大腦區塊外，尚有前扣帶迴、紋狀體、與齒狀迴呈現c-Fos表現量增加的現象。綜合以上結果，DRL-10秒作業於學習初期所進行的行為抑制可能和前額葉皮質與海馬體的神經互動有關；而學習較末階段的計時表現，則可能需要前額葉皮質、紋狀體、與海馬等三處較多的次級區域的組織加入，形成神經網路的方式支援之。 / Differential reinforcement of low-rate responding (DRL) task was an operant conditioned behavior based on temporal contingency. This task has been widely used to investigate the behavioral components of timing and behavioral inhibition, which is frequently used for pharmacological screening of anxiolytic and antidepressant drugs. Despite of being widely used as an animal behavioral model in the laboratory, but the performance of the DRL task was varied and inconsistent when the drug test conducted. One way to encounter this problematic issue is to differentiate the distinct behavioral components of DRL task and correlate the involved neural substrates, which was the theme investigated in the present study. This study first characterized the acquisition process of the DRL-10 sec task into behavioral inhibition and the timing stages, and then assessed the c-Fos levels by immunohistochemistry in the eight brain areas that potentially involved in behavioral inhibition and the timing processes. Regarding the stage of behavioral inhibition, significant increases in c-Fos-positive neurons were observed in the orbitofrontal cortex (OFC), the medial prefrontal cortex (mPFC), and the hippocampal CA1 area. At the stage of the timing being acquired, c-Fos immunohistochemical activity was highly expressed in the anterior cingulated cortex (ACC), OFC, mPFC, the dorsolateral striatum (dlS), the dentate gyrus (DG), and the hippocampal CA1 area. Together, these results showed that the functioning dual paths between the hippocampus CA1 and the prefrontal cortex (OFC and mPFC) are critically essential for developing the appropriate performance via behavioral inhibition in the early-stage of the DRL task and with three other areas (ACC, dlS, and DG) being recruited, an anatomical circuitry connecting prefrontal/striatal/hippocampal structures were involved in the acquisition of interval timing toward the later establishment of the DRL behavior.

本研究利用兩種時間關聯之操作式制約行為作業探討韁核的行為功能，一為區辨性增強低頻反應作業（簡稱DRL作業），另一為固定時距作業（簡稱FI作業）。本研究以神經毒素鵝膏蕈酸（ibotenic acid）破壞韁核的方式來測試大白鼠受試在上述行為作業之不同歷程的影響效果，包含習得歷程、行為表現階段以及已習得後轉換得酬賞之反應標準等三個階段。實驗一的結果顯示破壞韁核對於DRL作業的習得歷程具有明顯的影響，其影響效果在DRL短時距作業中造成無法以有效率的壓桿反應模式獲得酬賞；反之，破壞操弄的效果並不影響FI長與短時距作業的習得歷程。實驗二的結果顯示破壞韁核並不影響已習得的DRL作業與FI作業的行為表現，兩項作業的實驗組受試皆能維持穩定的行為反應模式且與控制組無明顯差異。實驗三對已習得的DRL行為進行時距參數的轉換（含調高及降低兩部份），結果顯示破壞韁核之操弄並未明顯的影響這項轉換新的時距之作業要求，但實驗組受試的確比控制組較遲緩達到新的時距要求。綜合而言，本研究以專屬性較高的神經毒素破壞韁核，用較多元指標的行為分析方式探討韁核的行為功能；其結果發現韁核參與DRL行為內含的區辨學習與對於錯誤偵測的負向迴饋，這些功能是需要透過韁核與其他中腦及邊緣系統的組織互動。 / This study examined the function of habenula (Hb) by two kinds of operant conditioned behavior tasks based on temporal contingency, including the differential reinforcement of low-rate responding (DRL) task and fixed-interval (FI) task. The effects of Hb lesion induced by neurotoxin ibotenic acid were examined at the different stages of operant conditioned behavior, including acquisition, performance, and transition stages. The results showed that bilateral lesions of Hb did not affect the locomotor activity and the basic lever-pressing. In Experiment 1, Hb lesion group had less reinforced responses and lower peak time indicating the deficits of acquisition of the DRL task. In contrast, the same lesion manipulation on the FI task did not produce any difference between the lesion group and the control group. The data of Experiment 2 showed that Hb lesion did not significantly affect the learned behavior maintained on DRL-10s or FI-30s schedule. In Experiment 3, Hb lesion produced a subtle, but not significant, impairment on behavioral transition from a learned interval to a newly-set interval (upward or downward). The lesioned subjects made a slower transition than the controls. In conclusion, these data suggest that the function of habenula is involved in discrimination learning and error detection for acquiring DRL behavior. However, it is likely that these Hb functions have to rely upon dynamic relationship between Hb and other midbrain limbic systems.