Episodic and Source Memory in Autism
Tanuja Poorun
MSc Research Methods
Supervised by Prof. Paul W. Burgess
With G. G. Yaacovi & H. Sugarman
Outline
• Literature Review
• Hypotheses
• Participants
• Procedure
• Possible Results
• Questions
Remembering & Knowing
Awareness of Memory
Autonoetic Consciousness:
Noetic Consciousness:
[Contextual details of previous
events]
[Abstract awareness of
knowledge]
Remembering =
Knowing =
Episodic Memory
Semantic Memory
Episodic Memory (EM)
• Link between EM deficits and frontal lobe (FL)
impairment
– Patients with FL damage & those with schizophrenia
experience less “remembering”
• EM may require aspects of executive control –
known cognitive deficits in ASD
• Possible impairment of autonoetic experience in
adults with ASD
– Evidence of EM deficits in adults with Asperger’s
syndrome (Bowler et al., 2000)
Source Memory (SM)
• Defined as ability to recollect contextual
information about an event
– Possibly a function of EM
• rPFC implicated in SM
– See Figure 1 (Turner et al., 2008)
• Possible SM deficits in ASD
– Evidence in adolescents & adults with Asperger’s
Syndrome (Bowler et al., 2004)
SM link to rPFC
Figure 1:
Regions of rPFC
activated in critical
contrasts.
Recollection of
perceived/imagined
and temporal
source versus new
items
(Turner et al., 2008)
Theory of Mind (ToM)
• Also known as “mentalising’: The cluster of
abilities held to be necessary to understand the
mental processes of others (Frith, 1997)
• ToM strongly associated with FL functioning
– See Figure 2
• Evidence of impaired ToM in ASD
– E.g false belief test
• Possible link to EM & SM deficits
– Inability to reflect upon subjective experience & lack of
consciousness of own knowledge
ToM linked to PFL
Figure 2:
Location of peak
activations in
medial prefrontal
regions during
tasks where
subjects think
about their own or
others' mental
states (carried out
by C. Frith, 1999)
Gateway Hypothesis
• Supervisory Attentional Gate (SAG) (Burgess et al., 2007)
– Supported by rPFC, approx. Brodmann’s Area 10
– Functional sub-division of rPFC (see Fig. 3)
– Mediates attentional switching between external stimuli
(stimulus-oriented, SO cases) and internal
representations (stimulus-independent, SI cases)
• Atypical functioning of SAG in autism
– fMRI: Atypical recruitment of rPFC in ASD (Gilbert et al., 2008)
– Impairments in mentalising (associated with mrPFC)
– Impairments in attentional switching between SO & SI
Differential activation of rPFC
Figure 3: Differential activation of the rostromedial and rostrolateral PFC
during attentional orientation to external and internal information,
respectively. Center: Brain activation map showing significantly stronger
activation of the anterior rostromedial PFC during the orientation of
attention to external as compared to internal information (blue), and
significantly stronger activation of the rostrolateral PFC during the
orientation of attention to internal as compared to external information
(red). (Henseler et al. 2010)
Central Coherence (CC) Theory
• Possible weak CC in ASD
– Failure to integrate sources of information to establish
meaning
– Possibly caused by atypical SAG
– Disproportionate attentional focus on external stimuli at
expense of attention to internal representations
• May explain difficulties in retrieving subjective
experiences in ASD, i.e. less ‘remembering” (EM)
+ difficulties in retrieving context in which
information was encoded (SM)
Hypotheses
• HFA adults will show impairments in EM & SM
• Prospective Memory (PM) Task
– PM deficits in ASD subjects who also show
impairments in EM & SM may contribute towards our
understanding of the SAG.
Participants
• 40 participants in total
– 20 HFA adults
– 20 control
• IQ measures
– National Adult Reading Test
– Advanced Progressive Matrices
• Autism Questionnaire
Procedure
• Encoding Phase
– Participants rate words according to Pleasant or
Unpleasant
– Stimuli:
• 30 words (List A) obtained from MRC Linguistic Database
• Neutral, high frequency, concrete, 4-7 letters long
• E.g. Coat, Surf, Kitchen
– Responses recorded using arrow keys
Procedure
• Remember/Know Task
– Adapted from Wheeler & Stuss (2003) memory
paradigm
– Stimuli
• 60 words = 30 words from List A + 30 matched new words
– Participants required to determine if word comes from
previous task (List A) or if word is new
Procedure
• Instructions for Remember/Know Task
Remember
Know
New Word
(Press Key 1)
(Press Key 2)
(Press Key 3)
You recognise
seeing the presented
word during the
previous task and
can remember
specific details
about it (such as
when the word
occurred or what you
thought about at the
time).
You recognise the
presented word but
can not reexperience
something specific
that is related to that
word (meaning that
you simply know or
you have a general
feeling that it
occurred earlier).
You do not
remember seeing the
presented word and
you think that it is
new (meaning that it
did not appear in the
first task), or you are
unsure whether you
saw the word or not.
Procedure
1st Encoding Phase
(List A)
2nd Encoding Phase
(List B)
1st Remember/ Know
Task
(List A + New words 1)
2nd Remember/ Know
Task
(List B + New words 2)
Temporal Order Judgement Task
(New words 1 & 2)
Procedure
• Temporal Order Judgement Task
– Adapted from Turner et al. (2008) source monitoring
paradigm
– Stimuli:
• 60 words from FOILS 1 and 2
– Participants required to determine whether the
presented word comes from the 1st R/K Task or the 2nd
R/K Task.
– Responses recorded using arrow keys
Analysis
• Encoding Phase
– Latencies & Pleasantness ratings
• Remember/Know Task
– Latencies
– Accuracy
– Remember or Know responses
• Temporal Order Judgement Task
– Latencies
– Accuracy
Possible results
• Deficits in EM in ASD:
– More “Remembering” than “Knowing” responses
• Deficits in SM in ASD:
– Lower accuracy due to problems in retrieval of contextspecific information
References
•
•
•
•
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Bowler, D. M., Gardiner, J. M., Grice, S. J. (2000). Episodic Memory and
Remembering in Adults with Asperger Syndrome. Journal of Autism and
Developmental Disorders, 30 (4), 295-304.
Burgess, P.W., Dumontheil, I. & Gilbert, S.J. (2008). The gateway hypothesis of
rostral prefrontal cortex (area 10) function. Trends in Cognitive Sciences, 11 (7),
290-298
Frith, U. (1997). The neurocognitive basis of autism. Trends in Cognitive Sciences,
1 (2), 73-77.
Gilbert, S.J., Bird, G., Brindley, R., Frith, C.D. & Burgess, P.W. (2008). Atypical
recruitment of medial prefrontal cortex in autism spectrum disorders: An fMRI
study of two executive function tasks. Neuropsychologia, 46 (9), p2281-2291.
Wheeler, M. A. & Stuss, D. T. (2003). Remembering and knowing in patients with
frontal lobe injuries. Cortex, 39, 827-846
Questions?