Memory in the Brain
Mt. San Antonio College
Dr. John Pellitteri
Memory in the Brain
According to recent studies examining memories of highly arousing real-life events, such
as the 9/11 terrorist attacks, memories of emotional events differ from everyday events in their
ratings of vividness, recollection, and belief in accuracy (Sharot et al., 2004). This composes a
“subjective sense of remembering” because the objective accuracy of these memories are the
same regardless of emotion. To further examine this occurrence, Sharot, Delgado, and Phelps
(2004) conducted a study that utilized event-related functional magnetic resonance imaging
(fMRI) to explore blood oxygen level dependent (BOLD) signal changes associated with the
subjective feeling of remembering emotional and neutral photos.
For this study, Sharot et al. (2004) utilized a controlled laboratory paradigm known as the
‘remember’/’know’ procedure. The dual process theory of recognition states that ‘remember’ and
‘know’ responses are two different memory processes. Thus, the participants in this study had to
assign previously-experienced stimuli as either ‘remembered’ or ‘known.’ Remembered stimuli
is based on recollection, or recognition supplemented with associative information, whereas
known stimuli is based on familiarity, or memory without contextual information (Sharot et al.,
There were a total of 13 healthy right-handed subjects (5 male and 8 female) included in
this study’s analysis. Sharot et al. (2004) selected 75 negatively arousing photos and 75 neutral
photos from the International Affective Photo Series (IAPS) to be used as the stimuli presented
to the participants. They classified these two categories by examining each photo’s standard
scores for emotional arousal and emotional valence.
The participants first completed an incidental encoding task consisting of 120 trials. Each
trial included the showing of either an emotional or neutral image for two seconds, presentation
of a rating task judging the visual complexity of the photo for two seconds, and lastly fixation for
ten seconds (Sharot et al., 2004). An hour later, the fMRI scanning session began with a
structural scan and then six functional scans. Each of the functional scans consisted of 25 trials,
which included viewing the photo for two seconds, making recognition judgments for two
seconds by indicating ‘remember’ or ‘know’ after the photo disappears, and looking at the
fixation cross for ten seconds (Sharot et al., 2004).
After analyzing the patterns of BOLD activation, Sharot et al. (2004) concluded that
depending on the level of emotionality of a stimuli, distinct subregions of the medial temporal
lobe have different influences on recognition judgments. The researchers found that in regards to
emotional material, the heightened feeling of remembering is associated with increased activity
in the amygdala (Sharot et al., 2004). When making a ‘remember’ judgment for an emotional
photo, an individual depends on the feeling of arousal signals and intensified perceptual fluency
associated with the amygdala. This enhances the subjective experience of retrieval without
necessarily increasing accuracy (Sharot et al., 2004). Meanwhile, when a participant makes a
‘remember’ judgment for neutral photos, they rely on recognizing visual details, which
corresponds to increased activity in the parahippocampal cortex (Sharot et al., 2004).
While Sharot et al. (2004) utilized a typical artificial laboratory stimulation, Frings,
Mader, and Hüll (2010) conducted a study assessing memory-related fMRI activation with the
natural and ecologically valid stimulation of watching television news. By developing a
paradigm that closely mimics everyday life situations of information encoding and acquisition,
the researchers aimed to test brain activation during more complex, real-life stimulation (Frings
et al., 2010). Furthermore, the researchers believed that the natural, real-life paradigm would
create a more comfortable environment which would decrease possible anxiety effects on the test
performance (Frings et al., 2010).
The participants in this study were 17 neurologically healthy subjects (9 females and 8
males) ranging from 22 years to 70 years old. The natural stimuli chosen for the memory task
were six clips from a German daily TV news show called ‘Tagesschau.’ Each clip contained a
complete news story in 20-30 seconds. For the control condition, Frings et al. (2010) took the
same six news clips but reversed its audio and randomly rearranged its visual pixels. Thus, its
sound and visual presentation were no longer distinguishable nor meaningful. Additionally, the
researchers randomly distributed a fixation cross baseline condition.
Before the memory task and MR scanning was conducted, the subjects were asked to
listen and watch carefully as they would be asked to recall the six news clips in as much detail as
possible. During the memory paradigm, “208 BOLD-sensitive echo planar images of the entire
cerebrum were acquired using a 3 Tesla Siemens TIM-Trio” (Frings et al., 2010, p. 2).
Afterward, the researchers contrasted brain activity (regional BOLD response) during the
episodic memory task that required semantic processing to the control condition that did not need
semantic or episodic memory processing (Frings et al., 2010).
After conducting a one-sample T-test analysis for this main memory task effect, Frings et
al. (2010) found a left-lateralized activation pattern that primarily involved the lateral temporal
cortex, frontal cortex, and left hippocampus. The researchers believe that this observed activation
correlates to the ventral stream brain regions that have been previously studied to be crucial in
language processing. For instance, the areas include the left temporal pole, which is known as the
semantic hub, as well as the inferior, posterior temporal activated region that is termed the basal
temporal language area (Frings et al., 2010). Therefore, Frings et al. (2010) conclude that the
majority of the observed areas of activation pertain to semantic processing of incoming
information, which is necessary for the hippocampus to encode episodic memory.
The secondary purpose of this study was to examine how age differences would affect
brain activation during information acquisition. Frings et al. (2010) performed a multiple
regression analysis to study the fMRI age effect. The analysis organized in table two of the
research article revealed a significant relation between older age and greater activation in the
superior temporal regions of the left hemisphere (Frings et al., 2010). The researchers
hypothesize that this increased activity in the left superior temporal regions for the elderly was
due to how the elderly subjects needed to increase their efforts and their attention to memory in
order to perform as well as the younger participants (Frings et al., 2010).
Frings et al. (2010) noted that another possible explanation for this observed age effect on
activation is the altered hemodynamics in elderly subjects that are not related to cognition. In
comparison to the main task effect previously detailed, the researchers claim that the age-effect
observations and analyses were considered a “secondary, preliminary result of the current study
that requires replication by studies assessing larger numbers of participants” (Frings et al., 2010,
p. 6). Thus, there is no formal, concrete conclusion for the age-effect aspect of this study as the
researchers need to conduct further studies to solidify the validity of their claims.
Due to the less controlled nature of this study that mimicked complex real-life
stimulation, there were many factors involved in the memory task. A study that focused
specifically on verbal episodic memory was conducted by Nyberg, Mclntosh, Houle, Nilsson,
and Tulving (1996). They utilized positron emission tomography (PET) to explore cerebral blood
flow associated with verbal episodic retrieval.
In the study, each of the 11 right-handed young volunteers went through an experimental
procedure consisting of “four conditions in which regional cerebral blood flow (rCBF) was
estimated from PET counts” (Nyberg et al., 1996, p. 715). The participants were auditorily
presented with two lists of 80 words. Half of the words were read by a male voice, while the
other half were read by a female voice. As stated in the article, the first condition was the visual
recognition of words following meaning-based encoding. The meaning-based encoding task
consisted of the participant deciding whether the words they heard referred to living or
non-living things. The second condition was the visual recognition of words following
perceptual encoding. In the perceptual encoding task, subjects had to decide whether the words
were read out loud by a male or female. The third and fourth conditions were visual recognition
of non-studied words and a baseline word-reading condition, respectively (Nyberg et al., 1996).
During each of the eight recognition tests for each participant, PET scans were obtained
with a GEMS-Scanditronix PC 2048-15B head scanner (Nyberg et al., 1996). Afterward, Nyberg
et al. (1996) cross-correlated the rCBF pattern during recognition performance following
meaning-based encoding with the proportion of correctly recognized items. After the correlations
were computed, they discovered a significant positive correlation between recognition
performance and brain activity in the left anterior medial temporal lobe (Nyberg et al., 1996).
Likewise, Nyberg et al. (1996) found a positive correlation between recognition performance
following perceptual encoding and activity in this same region. This further demonstrates the
reliability of this correlation in the sample.
These correlational analyses outcomes suggested a possible connection between verbal
episodic retrieval and left medial temporal lobe activity (Nyberg et al., 1996). Thus, the
researchers hypothesized that “recognition following meaning-based encoding, which resulted in
the highest memory performance, should be associated with higher activity in the left medial
temporal lobe” (Nyberg et al., 1996, p. 716).
To test this expectation, Nyberg et al. (1996) conducted a partial least squares analysis.
The analysis indicated a spatial pattern in brain areas that differentiated recognition following
meaning-based encoding from the other three conditions studied. The components with the
strongest positive weight were found to be located in the left and right medial temporal lobe
(Nyberg et al., 1996). The researchers therefore concluded that activity in the medial temporal
lobe is indeed associated with verbal and not only visual retrieval. Furthermore, the partial least
squares analysis also confirmed their hypothesis that an increase in left medial temporal activity
correlates with increased retrieval.
Frings, L., Mader, I., & Hüll, M. (2010). Watching TV news as a memory task–brain activation
and age effects. BMC Neuroscience, 11(1), 106–106.
Nyberg, L., Mclntosh, A., Houle, S., Nilsson, L., & Tulving, E. (1996). Activation of medial
temporal structures during episodic memory retrieval. Nature (London), 380(6576),
Sharot, T., Delgado, M., & Phelps, E. (2004). How emotion enhances the feeling of
remembering. Nature Neuroscience, 7(12), 1376–1380. https://doi.org/10.1038/nn1353
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