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| PERSONAL
PROFILE |
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I grew up in
Auckland, New Zealand, and most recently lived with my family in
Orewa Beach, a small community on the sub-tropical Pacific coast
north of Auckland. I completed my B.A. in Psychology and History
and my M.A. in Psychology at the University of Auckland. In 2001,
I was awarded a Canadian Commonwealth Scholarship to pursue my PhD
at the University of Toronto.
I am based
both at Toronto Western Hospital with co-supervisor Dr. Mary Pat
McAndrews, and the Human Neuropsychology and Cognitive Science Lab
with co-supervisor Dr. Morris Moscovitch. I decided to attend the
University of Toronto not only because of the reputation of my department
and my supervisors, but also because of the chance to use medical
imaging techniques, such as fMRI. Here, I am continuing with research
into autobiographical memory with an investigation of the role of
the hippocampus in autobiographical memory retrieval.
My experience
in Toronto so far has been incredible. It is an exciting and diverse
city, and I have had a lot of fun meeting new people from many different
places around Canada and the world.
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| RESEARCH
INTERESTS |
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| Autobiographical
Memory |
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My research
centres on autobiographical memory (AM): memory for both personally
experienced events (personal episodic memory) and facts about oneself
(personal semantic memory). I am interested in investigating not
only in the structure of AM, but the neural regions and networks
supporting retrieval, the impairment of AM in diseases such as Alzheimer's
disease and temporal lobe epilepsy, and the interactions between
AM and other cognitive and social cognitive processes, such as identity.
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| The
Role of the Hippocampus in Autobiographical Memory Retrieval |
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neuroimaging studies report preferential hippocampal engagement during
AM retrieval. Although the basis of this preferential activation remains
unclear, it may be related to the temporal specificity, recency or
recollective qualities of AMs, such as detail, emotionality and personal
significance. Typically, however, these variables are confounded,
and thus we sought to investigate the contributions of each to hippocampal
activation during AM retrieval. Thus, we have conducted an fMRI study
which examined the contributions of these different variables to hippocampal
engagement during AM retrieval. Briefly, no differences in hippocampal
activation was evident between specific and general AM retrieval,
suggesting temporal specificity, on its own, is not a key modulator
of hippocampal activation. Activation of the left hippocampus during
specific AM retrieval did vary with the level of detail, personal
significance, and at a subthreshold level, emotionality, when the
effect of recency was covaried out. Further, during general AM retrieval,
all three recollective qualities modulated activity in the right hippocampus.
Although the recency of specific AMs modulated hippocampal activation
bilaterally, this effect dissipated in the left hippocampus when detail
or emotionality was included as a covariate, and was no longer present
in either hippocampus when personal significance was taken into account.
Our results suggest that recollective qualities are important predictors
of hippocampal engagement during AM retrieval independent of factors
such as recency. |
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| Neural
Networks Supporting Autobiographical Memory |
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further interrogate the data collected in the above study, we are
currently conducting multivariate partial least squares (PLS) analyses
(McIntosh et al., 1996). This will enable us to determine whether
different functional networks are engaged during the retrieval of
general and semantic AMs, as well as AMs which are high and low in
recollective qualities. Further, we can also examine whether there
are networks which correlate specifically with the hippocampus during
AM retrieval. |
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| Autobiographical
Memory and Identity in Alzheimer's Disease |
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a number of theories posit a relationship between autobiographical
memory and identity, this has not been investigated directly. In collaboration
with Lynette Tippett at the University of Auckland, we assessed the
status of autobiographical memory and identity in individuals with
Alzheimer's disease (AD) and age-matched controls, and investigated
whether degree of autobiographical memory impairment was associated
with changes in identity. We used two tests of autobiographical memory
(Autobiographical Memory Interview, autobiographical fluency) and
two measures of identity (Twenty Statements Test, identity items of
the Tennessee Self Concept Scale) were administered. AD participants
exhibited significant impairments on both memory tests, and changes
in the strength, quality, and direction of identity relative to controls.
Impairments of some components of autobiographical memory, particularly
autobiographical memory for childhood and early adulthood, were related
to changes in the strength, quality and complexity of identity. These
findings support the critical role of early adulthood autobiographical
memories (16-25 years) in identity (e.g. Fitzgerald, 1998, 1996),
and suggest autobiographical memory loss affects identity. We are
currently conducting a follow-up study with Honours student, Sharon
Buxton. |
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PUBLICATIONS |
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| Addis,
D.R., McIntosh, A.R., Moscovitch, M., Crawley, A.P. & McAndrews,
M.P. (2004). Characterizing spatial and temporal features of autobiographical
memory retrieval networks: A partial least squares approach. Neuroimage,
23, 1460-1471. |
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| Addis,
D.R., Moscovitch, M., Crawley, A.P. and McAndrews, M.P. (2004).
Qualities of autobiographical memory modulate hippocampal activation
during retrieval: Preliminary findings of an fMRI study. Brain
and Cognition, 54, 145-147. |
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| Addis,
D.R., Moscovitch, M., Crawley, A.P. & McAndrews, M.P. (2004).
Recollective qualities modulate hippocampal activation during autobiographical
memory retrieval. Hippocampus, 14, 752-762. |
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| Addis,
D.R. & Tippett, L.J. (2004). Memory of myself: Autobiographical
memory and identity in Alzheimer's disease. Memory, 12, 56-74. |
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| Moscovitch,
M., Westmacott, R., Gilboa, A., Addis, D.R., Rosenbaum, R.S.,
Viskontas, I., Priselac, S., Svoboda, E., Ziegler, M., Black, S.,
Gao, F., Grady, C.L., Freedman, M., Köhler, S., Leach, L., Levine,
B., McAndrews, M.P., Nadel, L., Proulx, G., Richards, B., Ryan, L.,
Stokes, K., & Winocur, G. (in press). Hippocampal complex contribution
to retention and retrieval of recent and remote episodic and semantic
memories: Evidence from behavioural and neuroimaging studies of healthy
and brain-damaged people. |
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| Moscovitch,
M., Rosenbaum, R.S., Gilboa, A., Addis, D.R., Westmacott, R.,
Grady, C., McAndrews, M.P., Levine, B., Black, S.E., Winocur, G. &
Nadel, L. (2005). Functional neuroanatomy of remote episodic, semantic
and spatial memory: A unified account based on multiple trace theory.
Journal of Anatomy, 207, 35-66. |
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| UNPUBLISHED
THESES |
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| Addis,
D.R. (2001). Memory of myself: Autobiographical memory and personal
identity in Alzheimer's disease. Unpublished Master's thesis, University
of Auckland. |
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| PRESENTATIONS |
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Addis,
D.R. and Tippett, L.J.* Memory of myself: Autobiographical memory
and identity in Alzheimer's disease. International Society for
Behavioural Neuroscience Tenth Annual Meeting (May 18-22, 2002),
Quebec, Canada.
(*Presenting author) |
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| ABSTRACTS
& POSTERS |
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| Addis,
D.R., Moscovitch, M., Crawley, A.P. and McAndrews, M.P. (in press).
Attribute-based modulation in medial temporal activation during recollection
of personal experiences. Journal of Cognitive Neuroscience.
(Supplement). |
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