Implicit and explicit memory in the patient with amnestic mild cognitive impairment
- VernacularTitle:遗忘型轻度认知损伤患者的内隐和外显记忆
- Author:
Wei WANG
;
Luning WANG
;
Bo ZHOU
;
Xiaohong ZHANG
- Publication Type:Journal Article
- From:
Chinese Journal of Tissue Engineering Research
2005;9(40):145-148
- CountryChina
- Language:Chinese
-
Abstract:
BACKGROUND: Patients with amnestic mild cognitive impairment (MCI)were considered to be going to develop into Alzheimer disease, and were the high-risk group of Alzheimer disease.OBJECTIVE: To study the implicit and explicit memory in the patient with amnestic MCI. DESIGN: Homochronous and controlled observation.SETTING: Neurological Department of the Southern Building of General Hospital of Chinese PLA.PARTICIPANTS: The research was carried out at Neurological Department of the Southern Building of General Hospital of Chinese PLA from January to June 2003. Totally 20 male patients with amnestic mild MCI,with the average age of (78.7±4.9) years and the average educational time of (8.2±1.0) years, selected from neurological out-patient clinic and ward of southern building of General Hospital of Chinese PLA, Complaint memory losing and confirmed by the relatives and close friends of the patients, Mini-mental state examination (MMSE) ≥24, activity of daily living (ADL)＜26, and clinical dementia rating equal to 0.5, Objective memory examination score reduced compared to the examiners' educational background,the memory quotient recorded by clinical memory sheet to be 63-77 (lower than the normal value with 1.5-2.5 standard deviation), were accepted, and determined as experiment group.Totally 20 healthy male veterans selected from Beijing area, with the average age of(77.9±4.7) years and the average educational time (8.1±1.1) years were selected as control group. All subjects volunteered to take part in_the examination.METHODS: Explicit memory included word free recall and re-recognition task. The Chinese characters were selected from the 1000 most commonly used ones in the books of primary and middle schools. The 30 double characters-words were chosen and randomly divided into two tasks. Recall task included 10 double character words that were target words. Re-recognition task included 20 double character words, of which one half were target words, and the other half were interfering words. Implicit memory included word free recall and character-root-complementary task. The Chinese characters were from the same source as mentioned before. Thirty Chinese characters were chosen in free recall task at beginning. These Chinese characters at least had possibility of composing over 4 commonly used double character-words in primary and middle school books. One double-Chinese character-word in four possibilities was randomly selected and the total was 30 words. Then these 30 words were divided into two groups, one was target group and the other was interfering word. All selected Chinese characters were composed either up-down structure or right-left structure. Taking a part of the Chinese character would leave a characterroot. There were 30 character-roots and they were never the same each other.There were at least four possibilities to form a Chinese character for each root as properly matching among 1000 commonly used Chinese characters.At first, the subjects were asked to read the target words loudly for 3 times in 4 tasks and tried to remember all the target words (characters) and were told to test their memorization later on. The target words (or characters)would appear in one-minute interval. The subjects were asked to repeat the words (or characters) appeared before as many as possible based on their memory in free recall task and they did not have to remember the words (or characters) in order. The correct recall rate for 10 target words was calculated. In re-recognition task, the target words and interfering words were mixed up and appeared one by one in random order and the subjects were asked to tell if the words appeared before. The correct rate of 20-word rerecognition was calculated. In free recall task, the first character in target words was mixed with the first character in interfering words and they appeared one by one in random order. The subjects were asked to form any two-character-word with appeared Chinese characters and wrote down the first word thought of in test sheet. The hitting rate of target words and interfering words were calculated. t-test for independent samples was carried 9ut respectively between the two groups.MAIN OUTCOME MEASURES: ① Semantic priming effect (the hitting rate of target words in word free recall task and the hitting rate of interfering words) and apperception priming effect (the hitting rate of target words in character-root-complementary task and the hitting rate of interfering words) in the two groups. ② Difference of explicit memory (correct rate of free recall and correct rate of re-recognition) and difference of semantic and apperception priming effect in the two groups.RESULTS: All subjects in the two groups completed the test and entered the final analysis. ① Results of inner-group analysis: In the group of MCI,the hitting rate (0.41±0.15) of target words in word free recall task was significantly higher than that of interfering words (0.31±0.12, P ＜ 0.01),suggesting that there existed semantic priming effect in the patients with amnestic MCI as completing this task. In the character-root-complementary task, the hitting rate of target words (0.17±0.10) was significantly higher than that of the hitting rate of interfering words (0.10±0.07, P ＜ 0.05), suggesting that there existed perceptional priming effect in the patients with amnestic MCI as completing this task. In the control group, the hitting rate of target words (0.45±0.11) was significantly higher than that of the interfering words (0.33±0.10, P ＜ 0.01), suggesting that there existed semantic priming effect in the elderly with normal perception as completing this task as well. In the character-root-complementary task, the hitting rate of target characters (0.18±0.08) was higher than that of interfering characters (0.13±0.07, P ＜ 0.05), suggesting that there existed perceptional priming effect in the elderly with normal perception as completing this task as well. ② Results of inter-groups analysis: Correct rates of free recall and re-recognition in the MCI group was decreased (0.10±0.09, 0.45±0.13,t=9.858, P=0.000; 0.69±0.14, 0.83±0.08, t=3.685, P=0.000). There was not significantly different in Sementic priming effect and perceptional priming effect both in the MCI group and the control group.CONCLUSION: Sementic priming effect and perceptional priming effect were existed both in the MCI experiment group and the control group, but the implicit memory was not significantly different in the two groups. However, the patients with forgetful style MCI were exhibited a decline in explicit memory. Memory function of mild MCI patients was shown double characteristics, i.e. damage of explicit memory and preservation of implicit memory. The double character in memorial function provided theoretical basis for the rehabilitative training of MCI patients.
