טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentLevi Vered
SubjectThe Importance of Associations in Lexical Memory of an
Unknown Language,and Examples of EEG Patterns of
Three Participants During Encoding,
Sorted by Levels of Recall
DepartmentDepartment of Education in Science and Technology
Supervisor Professor Miriam Reiner


Abstract

Much of the published research on verbal memory focuses on associations, the role of rehearsal, classification and their role in the enhancement of verbal memory. However, the importance of association in lexical memory in the first stages of lexical learning is not clear. Also research on the neural patterns in the preliminary stages of associative lexical learning is in dispute and scarce. The aim of this study was to examine the importance of associations in memory as expressed in memory tests. In addition this study brings EEG scalp distributions of three participants, that differ by levels of memory of words of unknown language and number of associations.

This study of primary acquisition of words in young adults, used the method of acquisition of words in an unknown language that has no shared characters with the participants' language. Twenty-four young adults participated. They were shown 12 videos with pictures and words' pronunciations and were instructed to generate associations to the words. The Mitsar-202 EEG device was used to register brain activity while participants encoded the words. Participants' recall was tested after a short time delay and after a long time delay. Participants also reported the associations they had used. EEG signal of visual control task was also recorded.

The statistics on the relation between associations and recall as well as EEG patterns of the sample of three participants was calculated. A significant higher (92%) average of associations for the higher group than the lower recall group was found. The correlation that was found between the recall scores and associations scores was high (0.88) and significant. Significantly higher recall(?%) mean difference was found in favor of the association based words in comparison to recall of words without associations. 52% of the zero associations based words had very low recall scores - between 0 to 0.125 out of one point. 80% of zero associations based words scored also low -between zero and 0.355 out of one point. These analyses lead to the conclusion that generating associations is a critical factor in the recall of lexical memory. We also compared the correlation between recall scores and associations number in the short time delayed test and in the long time delayed test. Results were significant and similar.

Comparisons between EEG bands spectral power for each word across participants (high recall, medium recall and low recall) show that Delta spectral power is the predominant frequency for all levels of recall. Recent research is in line with our findings and indicates that Delta spectral power is related to memory and executive memory functions. A comparison of the frontal electrodes Delta spectral power and the Delta central pariental electrodes spectral power did not yield a statistically significant difference. Focal Delta spectral power analysis identified the Z-axis electrodes. The Delta spectral power on frontal, central pariental and focal electrodes was directly related to higher recall.

The report concludes with the possible value of these findings that might be imperative for verbal rehabilitation along better understanding of initial stages of language acquiring.