Ismail, Kartina
(2021)
Neural signature on easy to difficult level of N-back working memory load tasks in healthy subjects - a study of cognitive processing using EEG.
Masters thesis, Universiti Sains Malaysia.
Abstract
INTRODUCTION: Issue in cognitive process is linked with deficit of working memory.
The purpose of this study is to assess the neural processing during easy to difficult level
of n-back working memory load task in healthy subjects from EEG data.
METHODOLOGY: 28 healthy subjects (25 male, 3 female) who have completed at
least nine years of education were involved in the experiment. They were required to
complete four level of working memory load task which level as easy (0-back to 1back),
moderate (2-back) and difficult (3-back). Instructions were provided before each task
start. Cross-sectional design with convenient sampling was applied in the study. EEG was
recorded using ANT Neuro 64-channel. Data was collected with participant consent form
and pre-processing was done in Besa Research 6.1 software. The processed data then
analyse with one-way ANOVA and Friedman test where p < 0.05.
RESULTS: Theta oscillation shows it was statistically difference in frontal [F (3,108) =
10.91, p = 0.000], central [F (3,108) = 14.11, p = 0.000], left temporal [F (3,108) = 5.24,
p = 0.002], right temporal [F (3,108) = 4.09, p = 0.009], parietal [F (3,108) = 3.83, p =
0.012] and occipital [F (3,108) = 4.40, p = 0.026]. Additionally, central theta indicated 0-
back was statistically significant difference in all conditions of n-back working memory
load task (p < 0.05). There was only certain n-back working memory load task show
statistically mean difference in another region. Gamma shows statistically difference
between 0-back and the increase level of n-back working memory load tasks, 2(23)
296.962, p <0.000. Bonferroni correction revealed that gamma was statistically difference
in the right temporal on 0-back with 1-back (p=0.016), 2-back (p = 0.023) 3-back (p=0.030) and left temporal on 0-back with 3-back (p=0.009). All other regions do not
show any significant finding for gamma oscillations apart from the two regions of left
and right temporal.
CONCLUSION: The EEG results generally indicated that increase of working memory
load influences the decline of theta oscillatory whereas gamma oscillation occurs in two
regions with specified working memory load task condition. Thus, the study presented
the role of WM component such as attention, inhibition and recall in healthy adults.
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