Episodic and Source Memory in Autism

1. Episodic and Source Memory in Autism Tanuja Poorun MSc Research Methods Supervised by Prof. Paul W. Burgess With G. G. Yaacovi & H. Sugarman

2. Outline • Literature Review • Hypotheses • Participants • Procedure • Possible Results • Questions

3. Remembering & Knowing Awareness of Memory Autonoetic Consciousness: [Contextual details of previous events] Remembering = Episodic Memory Noetic Consciousness: [Abstract awareness of knowledge] Knowing = Semantic Memory

4. 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)

5. 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)

6. 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)

7. 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

8. 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)

9. 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

10. 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)

11. 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)

12. 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.

13. Participants • 40 participants in total • 20 HFA adults • 20 control • IQ measures • National Adult Reading Test • Advanced Progressive Matrices • Autism Questionnaire

14. 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

15. 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

16. Procedure • Instructions for Remember/Know Task

17. Procedure

18. 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

19. Analysis • Encoding Phase • Latencies & Pleasantness ratings • Remember/Know Task • Latencies • Accuracy • Remember or Know responses • Temporal Order Judgement Task • Latencies • Accuracy

20. 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 context-specific information

21. References • 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

22. Questions?