Effects Of Unitization Coding On Associative Memory In Adults And Its Age Differences

In real life,elements are rarely stored independently in events,but need to be represented by binding different elements through associative memory.Associative memory refers to the individual’s memory of two or more stimulus items or the relationship between stimulus items and their characteristics,background and other information at the same time.The unitization hypothesis holds that unitization coding can promote the efficiency of associative memory by improving the role of familiarity processing.However,previous studies have different views on whether the support of unitization coding for associative memory comes from familiarity or the joint effect of familiarity and recall.In addition,with the increase of age,the recall processing of adult individuals is gradually impaired,and the familiarity processing is relatively retained,resulting in differences in the impact of unitization coding on adult individuals of different ages.Therefore,this paper is divided into two parts to explore the neural mechanism of unitization coding on associative memory and the age difference characteristics of the effect of unitization coding on associative memory throughout adulthood.In Study 1,college students were selected as subjects to investigate the neural mechanism of unitization coding affecting associative memory by using event-related potential technology.Experiment A,the effect of unitization coding on within-domain inter-item associative memory.The behavioral results showed that: the response accuracy of relevant coding conditions was significantly higher than that of irrelevant coding conditions;The response time of relevant coding conditions was significantly shorter than that of irrelevant coding conditions.EEG results showed that:(1)the FN400 old/new effect of relevant coding conditions was significantly greater than that of irrelevant coding conditions;(2)Only the relevant coding conditions induced the LPC old/new effect;(3)For the “same” response,the ERPs evoked by relevant coding conditions at 300 ～ 500 ms and 500 ～ 700 ms were more positive than that evoked by irrelevant coding conditions;(4)Irrelevant coding conditions induced the PFC old/new effect.Experiment B,the effect of unitization coding on between-domain inter-item associative memory.The behavioral results showed that: the response accuracy of consistent coding condition was significantly higher than that of inconsistent coding condition;There was no significant difference in response time between consistent coding conditions and inconsistent coding conditions.EEG results showed that:(1)the FN400old/new effect and LPC of old/new effect of consistent coding conditions were significantly greater than those of inconsistent coding conditions;(2)For the “same” response,the ERPs evoked by consistent coding conditions at 300 ～ 500 ms and 500 ～ 700 ms were more positive than that evoked by inconsistent coding conditions(4)Inconsistent coding conditions induced the LPN old/new effect.In Study 2,young,middle-aged and old people were selected as subjects to explore whether unitization coding can promote the efficiency of associative memory and the characteristics of age differences.Experiment A,unitization coding affects the age difference characteristics of within-domain inter-item associative memory.The results showed that:(1)in terms of reaction accuracy,the young group and the middle-aged group were significantly higher than the elderly group;In terms of reaction time,the youth group was the shortest,the middle-aged group was the second,and the elderly group was the longest;(2)For the young group,the middle-aged group and the elderly group,the response accuracy of the relevant coding conditions were significantly higher than that of the irrelevant coding conditions,and the response time was significantly shorter than that of the irrelevant coding conditions;(3)The middle-aged group had the highest response accuracy effect and the response time effect.Experiment B,unitization coding affects the age difference characteristics of between-domain inter-item associative memory.The results showed that:(1)in terms of reaction accuracy,the young group and the middle-aged group were significantly higher than the elderly group;In terms of reaction time,the youth group was the shortest,the middle-aged group was the second,and the elderly group was the longest;(2)For the young group and the middle-aged group,the response accuracy of consistent coding condition was significantly higher than that of inconsistent coding condition,and the response time was significantly shorter than that of inconsistent coding condition.Only the response accuracy of the elderly group was significantly different;(3)There was no significant difference in response accuracy effect and response time effect among young group,middle-aged group and elderly group.According to the results of EEG and behavior,the following conclusions can be drawn:First,unitization coding can promote the efficiency of associative memory and improve the ability of individual associative memory;Second,unitization coding can improve the role of “familiarity” processing and “recall” processing in associative memory,but the influence mechanism of “after extraction” processing of within-domain interitem associative memory and between-domain inter-item associative memory is different;Third,the speed of associative memory in adults gradually slows down with age,while the accuracy begins to decline from old age;Fourthly,unitization coding can promote the associative memory efficiency of young people,middleaged people and the elderly;Fifthly,for within-domain inter-item associative memory,unitization coding has the largest promoting effect on middle-aged people;For between-domain inter-item associative memory,the promotion effect of unitization coding on young people,middle-aged people and the elderly is the same.