Brady, Noeleen M. (2013) Electrophysiological and Behavioural Markers of Associative Source Memory Decline in Normal Ageing. PhD thesis, National University of Ireland Maynooth.
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Abstract
Memory is the ability to encode and subsequently recall information (Brickman & Stern,
2009) and source memory refers to the ability to recall the source of the information,
including all contextual aspects related to an event (Glisky & Kong, 2008; M. Johnson,
Hashtroudi, & Lindsay, 1993). The ageing process shows a progressive decline in
memory (Cabeza, Anderson, Locantore, & Mcintosh, 2002) which is thought to be
related to atrophy in regions of the brain which are essential for memory (Pasquier,
1999). Source memory is particularly sensitive to cognitive ageing and is one of the
first types of memory to show impairment (Jennings & Jacoby, 1997; Siedlecki,
Salthouse, & Berish, 2005). In the current thesis different aspects of memory were
measured to determine the extent of memory decline in ageing using associative,
episodic and particularly source memory tasks. Both behavioural and
electrophysiological methods were used to investigate cognitive changes in performance
due to the ageing process between young and older adults along with an intervention at
the time of acquisition to determine if source memory recall can be enhanced in older
adults.
In Chapter 3 memory retrieval was examined between young (18-30 years, n=27)
and older (55-70 years, n=25) adults at three computer-based tasks, indexing source
memory (an Opposition task), associative memory (a Visual Paired-Associates task) and
episodic memory (a False Memory paradigm). Young and older adults were matched on
estimated scores of IQ, short-term memory and self-ratings of their own memory. The
results indicated that older adults have poorer accuracy and slower response times on
memory tasks of associative and source memory, with the latter showing particularly
large decrements due to ageing. Source deficits were clear on the Opposition task but
context had little effect on accuracy on the VPAc task, while few differences were
evident on the False Memory paradigm; therefore appears that memory for temporal
context (i.e. the timing of an event) suffers more impairment in ageing. These results
suggest that aspects of memory binding may be among the first memory processes to
suffer a decline in healthy ageing.
Chapter 4 examined young (18-30 years, n = 14) and older (50-75 years, n = 14)
adults’ differences in recorded EEG for three computer-based memory tasks which
assess source, episodic/associative and false memory. Reduced scalp electrical activity
was observed in older adults on the source memory task coupled with a poorer
behavioural performance. Reduced activity in older adults was also evident for
mistaken lures and the correct identification of lures in the false memory task, but no
behavioural differences were evident. For successful trials in associative memory tasks,
increased activity was present in older adults while behavioural performance was either
equal to or poorer than that of young adults. These data are mostly consistent with the
idea that young adults show larger mean ERP amplitudes than older adults, suggesting a
reduction in cognitive functioning in older adults which may have resulted in reduced
memory accuracy capacity.
In Chapter 5 data is reported from young (18-30, n = 15) and older (55+, n = 15)
adults during behavioural measures of source memory and the associated
electrophysiology. Participants completed the Opposition task and a Where-Who-What
task. Results generally indicated that older adults displayed poorer behavioural
performance and reduced amplitude P1 and P3 components on both tasks in comparison
to young adults, which may reflect enhanced perceptual ability (linked to the P1) and
recognition of the source of information (linked to the P3) in young adults compared to
older. However, the electrophysiology predominantly showed enlarged waveform
components in older participants at approximately 200ms for source memory tasks, and
revealed more anterior positive scalp activity in the older compared to posterior
topographies in the young which may indicate an automatic compensatory function in
older adults. These patterns may reflect the recruitment of additional cortical areas
acting in a compensatory manner to alleviate the age-related impairment in source
memory tasks.
An intervention with two source memory tasks was employed in Chapter 6.
Three groups of adults, young control (18-30 years, n = 20), older control (55+ years, n
= 20) and older intervention (55+ years, n = 20), took part in the experiment. Both
control groups completed two computer-based source memory tasks without the use of
an intervention, while the older intervention group used a strategy at the time of
acquisition for both source memory tasks under two methods: firstly, sentence
generation to enhance semantic binding; and secondly, story generation to increase
contextual binding. Results indicate that the use of an intervention allowed for
enhanced source memory recall in older adults compared to both control groups. In
addition, the interventions led to faster response times compared to the older control
group but not the young control group. It is concluded that while an intervention can
alleviate the age-related deterioration of source memory accuracy, it does not entirely
counteract the impairment in speed of processing typically seen in older adults.
The behavioural results of this series of experiments indicate that source
memory is negatively affected by the ageing process and that accuracy on source
memory tasks is more affected than tasks involving associative and episodic memory.
This supports previous findings indicating that memory for source is one of the first to
decline with ageing. However, despite this discrepancy in source memory, an
intervention strategy at the time of acquisition can lead to enhanced source memory
recall in older adults compared to older and younger control adults. The
electrophysiology may suggest that older adults have a decline in the perceptual
processing of the source of information compared to young adults which may be
reflected by the poorer behavioural performance on memory tasks. Furthermore older
adults may attempt to compensate for these reductions in perceptual processing, as
reflected by enlarged components at approximately 200ms. However, this
compensation does not appear to be fully effective as the older adults retain poorer
accuracies on source memory tasks. Additionally, the electrophysiology indicates
further compensation as positive-going activity appears to occur more anteriorly in
older adults which may reflect compensation for dysfunction in regions of the brain
responsible for perceptual processing. These results provide additional support for two
models of cognitive ageing, the Compensatory Related Utilisation of Neural Circuits
Hypothesis (CRUNCH; Reuter-Lorenz & Cappell, 2008) and Posterior Anterior Shift in
Ageing (PASA) models (S. W. Davis, Dennis, Daselaar, Fleck, & Cabeza, 2008).
Item Type: | Thesis (PhD) |
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Keywords: | Electrophysiological; Behavioural; Markers; Associative Source Memory Decline; Normal Ageing; |
Academic Unit: | Faculty of Science and Engineering > Psychology |
Item ID: | 7748 |
Depositing User: | IR eTheses |
Date Deposited: | 13 Jan 2017 10:46 |
URI: | https://mu.eprints-hosting.org/id/eprint/7748 |
Use Licence: | This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here |
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