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J Camosun Psyc Res. (2019). Vol. 1, pp. 37-42.
Submitted April 2019; accepted 12 July 2019.

The effect of memory encoding on neural activity.
Author: Kara Solecki*
Supervising Instructor: Michael Pollock, Psyc 215 (“Biological Psychology”)
Department of Psychology, Camosun College, 3100 Foul Bay Road, Victoria, BC, Canada V8P 5J2
*Corresponding author email: ksolecki5@gmail.com

ABSTRACT
The present study was undertaken in order to investigate the underlying neural mechanisms of
associative memory encoding. Both nonexperimental (i.e., baseline) and experimental methods
were used to study variations in associative memory encoding levels, using the method of loci,
on high frequency neural activity (HFA) (measured using EEG gamma activity) and low
frequency neural activity (LFA) (measured using EEG theta activity). It was hypothesized that
successful memory encoding would lead to a decrease in LFA and an increase in HFA. The
baseline methods found a strong correlation between memory encoding and HFA, but not with
LFA. Ultimately, the present experimental results did not support these hypotheses. These results
are contrary to other studies, though the present study is limited in both the number of
participants and number of trials. It is suggested that more research is necessary in order to
determine reliability.
1. Introduction
Every day people use retrieval cues to
recall previously encoded information.
Retrieval cues are created by associating
information with people, places, cognitive
and emotional states, among others. This
association enhances memory recall,
because they now have something else to
remind them of this new information
(Greenberg et al., 2015). An example of a
specific associative technique that makes
memory recall easier for many people is the
method of loci (MoL) (McCabe, 2015). The
MoL is a mnemonic technique in which
locations are used as the association with
information that is to be remembered. The
technique is used by imagining the new
information in specific locations along a
well-known route. To then retrieve this

information from memory, one only has to
mentally walk this path and imagine what
was “placed” at each location (McCabe,
2015).
There is empirical evidence that
techniques, such as the MoL, significantly
improve memory recall (McCabe, 2015). In
addition to this, it is fairly well understood
which anatomical locations in the brain are
most associated with this type of memory
(including the hippocampus and peripheral
cortex) (Greenberg et al., 2015, p. 257).
However, the underlying neural mechanisms
that account for this associative memory is
less understood.
Using associative memory
techniques, and measured with an
electroencephalography (EEG) device,
Greenberg et al. (2015) found that successful
encoding of words is associated with a
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decrease in low frequency activity (LFA)
and an increase in high frequency activity
(HFA) in the brain. The present study aimed
to replicate these findings.
The present study involved baseline
measurements and an experimental study.
During the baseline period, correlations
were measured between the number of
words successfully recalled using the MoL
and HFA, which was measured using the
average score of Muse EEG gamma activity
during an encoding period. Similarly, a
correlation was measured between word
recall and LFA. The present experiment
compared the average score of HFA,
measured using gamma activity, using a
procedure in which words were recalled
using the MoL, as compared to words
recalled when non-associative mental
repetition was used. Based on previous
research demonstrating changes in neural
frequency, during the baseline methods, it
was hypothesized that as memory increased
using an associative technique, HFA would
increase while LFA would decrease. In the
present experiment, it was expected that
successful memory encoding using the MoL
would cause an increase in gamma activity.
2. Methods
2.1 Participants
A single participant was used for both the
baseline methods and the experiment. This
participant was a 24-year old female
psychology student from Camosun College.
2.2 Materials and Apparatus
The materials used for both the baseline
study and the experimental study included
the “freerecall” battery from the PEBL
Launcher 2.0 (Mueller and Piper, 2014) and

a Muse (Muse, Interaxon Inc., Toronto, ON,
Canada) EEG device.
2.3 Procedure
During the baseline study, the participant
studied a list of 20 random words which
were populated and presented using the
PEBL Launcher 2.0 “freerecall” battery,
during which time the Muse EEG device
recorded neural activity. Immediately after
presentation of the 20 words, an option
emerged onto the screen in the PEBL
software which directed the participant to
type into an available space as many of the
20 words the participant could recall. For the
purpose of this study, the participant tried to
recall as many of the words in serial orderthe order in which the words had been
presented. The “freerecall” battery
automatically assigns a “correct” score for a
word recalled and spelled correctly
regardless of order position; however, serial
recall was assessed in the resulting data,
which was the area of interest during the
baseline and experimental measurements.
The number of words recalled correctly in
the correct order position was the
independent variable score which the
participant kept track of each day by writing
in a diary.
The dependent variable was measured
using the Muse EEG device; neural activity
was monitored and recorded during the
encoding period and a score for LFA and
HFA was obtained using the Muse EEG
device by using the average score for theta
(4-8 Hz) and gamma (30-44 Hz) neural
frequency, respectively. The scores were
recorded each day in conjuction with the
corresponding number of words correctly
recalled in serial order.
For the experimental study, the order of
conditions alternated each day for a total of
12 days. The condition that was used during
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the initial trial was determined by the flip of
a coin (heads= Method of Loci condition,
tails= Mental Repetition condition).
During the experimental study, serial
word recall was manipulated on
experimental days, through the use of the
MoL to encode the words while the 20
words were presented in the “freerecall”
battery. Successful memory encoding was
indicated by the number of words recalled,
in the same order as the words were
presented, immediately after the encoding
period. High frequency neural activity was
quantitatively measured through the
measurement of the participant’s neural
activity during the encoding period using the
Muse device; the average the score of
gamma waves was used to indicate HFA.
On control days, the participant
completed the same procedure as described
above, except the method of loci was not
used during the encoding period. Instead,
during encoding, the participant used mental
repetition of the words as they appeared.

The level of significance set in this
experiment was .05. The mean HFA during
the Method of Loci condition was 0.8042
(SD = 0.26) and the mean HFA during the
Mental Repetition condition was 0.8481 (SD
= 0.24) (see Table 2). These data were
analyzed using a t-test and the results were
not statistically significant, t = 0.3, p = 0.77,
suggesting that a higher number of words
recalled using the method of loci does not
cause higher frequency neural activity (see
Figure 3).
Table 1.

Table 2.

3. Results
A strong, positive, linear relationship was
found between the amount of words
successfully encoded and HFA, measured by
gamma waves, during the baseline
measurements. The correlation for this
relationship, r = 0.77, was statistically
significant, p = 0.007, suggesting that these
two variables are strongly related (see
Figure 1 and Table 1).
A weak, positive, linear relationship
was found between the amount of words
successfully encoded and LFA, measured by
theta waves, during the baseline
measurements. The correlation for this
relationship, r = 0.40, was not statistically
significant, p = 0.265, suggesting that these
two variables are related due to chance (see
Figure 2 and Table 1).
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Figure 1. Correlation for HFA and Memory Encoding

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Figure 2. Correlation for LFA and Memory Encoding

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Figure 3. The mean HFA in the Method of Loci and Mental Repetition conditions.

4. Discussion
The hypothesis under investigation in the
current study, that as memory encoding
increases, HFA would increase was
supported in a correlational analysis, but did
not hold up in an experimental design. The
hypothesis, that as memory encoding
increases, LFA would decrease was not
supported in a correlational analysis and so
was not tested experimentally.
The current results are inconsistent with
other studies that have demonstrated an
increase in HFA and decrease in LFA that
occurs with successful associative memory
encoding (Greenberg et al., 2015).
Limitations of the current study that should
be considered include the limited number of
participants and limited number of trials.
Further research should consider such

limitations. However, it is important to
consider the inconsistency with previous
studies and for further research to be
undertaken in order to understand the
reliability of these findings.
References
Greenberg, J. A., Burke, J. F., Haque, R.,
Kahana, M. J., & Zaghloul, K. A. (2015).
Decreases in theta and increases in high
frequency activity underlie associative
Memory encoding. Neuroimage, 114,
257-263.https://doiorg.libsecure.camosun.bc.ca:2443/10.101
6/j.neuroimage.2015.03.077
McCabe, J. A. (2015). Location, location,
location! Demonstrating the mnemonic
benefit of the method of loci. Teaching of
Psychology, 42(2), 169-173. doi:
10.1177/0098628315573143
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