Role of rat medial prefrontal cortex in time interval estimation
시간측정에 있어서 쥐 내측 전전두피질의 역활
- 주제(키워드) time perception , interval timing , mPFC , rat
- 발행기관 아주대학교
- 지도교수 정민환
- 발행년도 2013
- 학위수여년월 2013. 2
- 학위명 박사
- 학과 및 전공 일반대학원 의학과
- 실제URI http://www.dcollection.net/handler/ajou/000000013825
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
Several lines of evidence suggest the involvement of prefrontal cortex in time interval estimation. The underlying neural processes are poorly understood, however, in part because of the paucity of physiological studies. The goal of this study was to test the requirement of intact medial prefrontal cortex (mPFC) for performing the task and to find the mechanism of time interval estimation. In Experiment 1, I established a temporal discrimination procedure using six different time intervals ranging from 3018 to 4784 ms that needed to be discriminated as either long or short. Bilateral infusions of muscimol (GABAA receptor agonist) into the mPFC significantly impaired animal’s performance in this task, even when the animals were required to discriminate between only the longest and shortest time intervals. These results show the requirement of intact mPFC in rats for time interval discrimination in the range of a few seconds. In Experiment 2, I then recorded neuronal activity in the mPFC of rats performing the same temporal discrimination task. The recorded neuronal ensemble transmitted a significant amount of information on the elapse of time, suggesting that the mPFC might function as an internal clock. Also, a large fraction of recorded neurons conveyed temporal information by logarithmically changing activity profiles, so that the largest amount of variance in neuronal activity was account for by a logarithmic rather than a linear function, which is more consistent with logarithmic than linear encoding of time. When the range of time interval discrimination varied, activity profiles of mPFC neurons tended to vary according to the range of time interval discrimination, arguing against the possibility that seemingly timing-related neural activity might actually represent sensory response- or motor preparation-related one. These results suggest the rodent mPFC represents the elapse of time based on linearly changing neuronal activity on a logarithmic scale, which might be the reason why the precision of time interval discrimination is lowered in proportion to its duration according to Weber’s law.
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TABLE OF CONTENTS
ABSTRACT i
TABLE OF CONTENTS iii
LIST OF FIGURES v
LIST OF TABLES viii
Ⅰ. INTRODUCTION 1
Ⅱ. MATERIALS AND METHODS 7
A. EXPERIMENT 1 7
1. Subjects 7
2. Behavior task 7
3. Training procedure 9
4. Testing with drug infusions 13
5. Surgery 14
6. Drug infusions 15
7. Histology 15
8. Data analysis 15
B. EXPERIMENT 2 17
1. Behavior task 17
2. Unit recording 18
3. Analysis 19
Ⅲ. RESULTS 26
A. EXPERIMENT 1 26
1. Performance in the random-trial task 26
2. Effects of mPFC inactivation on time interval discrimination task 26
B. EXPERIMENT 2, 3 36 26 DISCRIMINATION 26
1. Behavior 36
2. Temporal information 36
3. Principal component analysis 48
4. Multiple linear regression analysis 57
5. Temporal information after sample interval offset 58
6. Temporal discrimination with variable temporal range 59
Ⅳ. DISCUSSION 75
A. ESSENTIOL ROLE OF PFC IN INRTVAL TIMING 75
B. TEMPORAL INFORMATION PROCESSING IN THE mPFC 77
C. LOGARITHMIC VS. LINEAR ENCODING OF TIME 79
C. IMPLICATIONS TO THEORIES OF INTERVAL TIMING 80
Ⅴ. CONCLUSION 83
REFERENCES 84
국문요약 95
