Event-related potential correlates of encoding and retrieval processes in human memory

Evoked potentials (Electrophysiology);Memory

Doyle, Hugh ; Rugg, M. D. (Michael D.) ; Rugg, M. D. (Michael D.)

University:University of St Andrews

Department:Psychology & Neuroscience (School of)

关键词: Evoked potentials (Electrophysiology);    Memory;   

Others  :  https://research-repository.st-andrews.ac.uk/bitstream/handle/10023/18389/HughDoyleMScThesis.pdf?sequence=2&isAllowed=y

来源: DR-NTU

【 摘 要 】

Inelectrophysiological research over the last few years there has beenagrowing tendency to utilise the Event-Related Potential as a tool in thestudy of cognitive processes, especially those which are well defined andunderstood. Over the last few years too, the study of encoding andretrieval processes in human memory has achieved a certain measure ofconsensus, in that many researchers have suggested that retrievalperformance depends largely upon the type of encoding process performedupon the item at presentation, in particular it is suggested that thedegree to which the physical characteristics of a stimulus item areanalysed will largely determine whether the item can later be recognisedand that the degree to which the semantic content of the item is analysedwilllargely determine whether the item can later be recalled. The presentseries of experiments sought to determine whether there existed ERPcorrelates of the twotypes of encoding process and of the two relatedretrieval processes, recognition and recall.In the first experiment, ERPs generated by words which were thought tohave been analysed at a physical level, as determined by whether they wererecognised 24 hours later, were compared with ERPs generated by wordsthought not to have received such processing, during both initial andsubsequent presentation. The ERP encoding data indicated that enhancementwas seen in late positive activity generated at Fz by words which werelaterrecognised with a high degree of confidence. This was taken to implythat the enhanced positivity was generated by elaborative encodingprocesses. The ERP retrieval data indicated: 1) that between 300-500 msecpost stimulus, words which were correctly recognised as "old" generatedpotentials of greater positivity than words which were correctly recognisedas "new". This wasinterpreted as an ERP index of a retrieval process basedonfamiliarity only. 2) Between 500-924 msec post stimulus, items whichmay have been recognised due to the retrieval of encoding context generatedgreater positivity than items recognised on the basis of familiarity alone.In experiment 2, the basic design was repeated with the exception thatacognitive task was interposed between trials to ensure that allprocessing related to subsequent memory performance was restricted to therecording epoch. ERPs were recorded only during the initial presentationof stimulusitems, and those generated by words later recognised were againcompared with those generated by items not recognised or recognised withlow confidence. The ERP data revealed the same enhanced late positivity atFzgenerated by words correctly recognised with a high degree ofconfidence, although, as in experiment 1, the effect was small.Inexperiment 3, ERPs were again only recorded to words during thefirstpresentation, but were this time compared on the basis of whetherwords had been recalled or not. It wasthought that if subsequent recallof itemsdepends on elaborative processing at presentation, thismanipulation would ensure that ERPs generated by recalled words wouldreflectactivity selective to elaborative encoding. The recording epoch wasalso lengthened in order that the ERPs might be sensitive to slow, longlatency effects. The data indicated that words which were recalledgenerated ERPs of significantly greater positivity in the region 800-1400msec at Fz than did words not recalled.Inexperiment 4, ERPs generated by words during retrieval wererecorded, and in this case ERPs generated by words whose experimentallylearned associates were recalled from memory, were compared with ERPsgenerated by words whose associates were not recalled. It was suggestedthat since recall depends upon retrieval of encoding context, ERPsgenerated by words whose learned associates were recalled, should reflectsuchprocessing. The ERP data showed that words whose associates wererecalled, generated activity of greater positivity than words whoseassociates were notrecalled, from 500 msec onwards at all three midlinesites.It is concluded from these experiments that at encoding, theactivation of elaborative processing is reflected by an enhancement of theERPactivity at Fz from approx. 500 msec onwards, and that at retrieval, 1)the activation of the "familiarity-checking" process generates enhancedpositivity at all midline sites between 300-500 msec, and 2) that the"retrieval of encoding context" process generates enhanced positivity from500 msec onwards. These data are related further in the conclusion to bothphysiological and cognitive theories of human memory.