Memory Deficits in

Alzheimer's Disease

Image: http://www.caregivingclub.com/wp-content/uploads/2012/11/Memory-Loss-dreamstime_m_15669472-2.jpg

Consumer Reports Best Buy Drugs (2012)

Alzheimers Disease Symptoms

• Earliest symptom = episodic

• Encoding new information (Delis et al, 1991)

• Delayed Recall Effects (Think Old/New effects) (Welsh et al, 1991)

• Mild Cognitive Impairment (MCI)

• Atrophy of relevant brain areas

– Responsible for consolidation and retrieval

– Mesial Temporal Regions

Image: http://arealmummydiary.files.wordpress.com/2013/08/image-3.jpg

Preclinical SymptomsSmall, Herlitz and Bäckman, 2004

• Episodic Memory Deficits

– General in Nature

• I.e. Both verbal and non verbal materials

• Across Retention Interval

• Across conditions (i.e. cued/free recall, recognition)

• Mediated by Cognitive Support

Image: http://arealmummydiary.files.wordpress.com/2013/08/image-3.jpg

Cognitive Support

• Recognition tasks have the most cognitive support

• Small et al, 1997 (See Small, Herlitz and Bäckman, 2004)

– Tested memory tasks to see which predicted onset of AD

• Significant effects in:recall of unlimited words

• Recall of organisable words

• Word and face recognition After multivariate analysis, only these two were significant predictors of a diagnosis.

Unsupported

Supported

Deficits typical of ageing

Kelle

r, M

acka

y, B

arri

ck, W

iesh

man

n, &

Ro

ber

ts, (

20

02

).

Old/New Effects

• Study context defined as ‘source’

• In healthy participants, trials may be contaminated by other recollective experiences

• However: AD begins with impaired recollection

Familiarity - NEW Recollection – OLD

Recognition without retrieval of ‘study context’ (source)

Recognition including recall of ‘study context’

Hypothesis Rationale(Tendolkar et al, 1999)

• Measured ability to recognise previously studied words and

recollect study context

• If AD patients cannot recollect contextual information, ERP

old/new effect should be less contaminated by recollective

processes than in healthy subjects.

• Therefore: ERP readings should be more purely related

to familiarity.

Methods: Study Phase

• 10 Study phases of 10 words

• 500ms duration (5.5s interval)

• Participants instructed to memorise word and presentation colour

BOOK WINDOW

Methods: Test Phase

• 50% of words OLD; 50% of words NEW

• Participants asked to respond if they had seen the word prior

• For words judged ‘old’, participants then asked to name the presentation colour

HOUSE BOOK

Results

AD Patients Controls

Impairment to recollect study context

Sustained old/new effect

Correctly recognised ‘old’ words more positive only between 300-500ms

Peaks over frontal scalp Left temporo-parietal and frontal sides

The ERP’sFAMILLIARITY = NEWRECOLLECTION = OLD

Frontal peaks should give a more pure version of familliarity…But do they?

The OLD’s in Alzheimers are wherein they have defied the nature of their illness.

(Tendolkar et al, 1999)

And Therefore..?

• Hippocampal atrophy to blame for lack of temporoparietal old/new effect?

• Symptoms typical of AD

• But… why could patients with AD still encode some things with a flat-line ERP during the encoding of OLD items?

What does the competition say?

• Debate as to whether semantic and episodic memories are tightly related (Tulving) or dissociated (Hodges & Graham)

• An episode cannot be recounted first without going through semantic memory (Tulving, 1995; Tulving & Markowitsch, 1998)

See Overman and Becker (2004)

Discussion

• Is this a ‘process based dissociation’

– What is a process based dissociation?

– What aboutthis model from Tulving that suggests it isconnected?

References

Consumer Reports Best Buy Drugs. (2012). Evaluating Prescription Drugs to Treat: Alzheimer’s

Disease. Retrieved from http://www.consumerreports.org/health/resources/pdf/best-buy-

drugs/AlzheimersFINAL.pdf

Keller, S. S., Mackay, C. E., Barrick, T. R., Wieshmann, U. C., Howard, M. A., & Roberts, N. (2002).

Voxel-based morphometric comparison of hippocampal and extrahippocampal

abnormalities in patients with left and right hippocampal atrophy. Neuroimage, 16(1), 23-

31.

Overman, A. A., & Becker, J. T. (2004). Information Processing Deficits in Episodic Memory in

Alzheimer’s Disease. In R. Morris, J. Becker (Eds.), Cognitive Neuropsychology of Alzheimer’s

Disease (pp. 120-140). New York: Oxford University Press Inc.

Small, B. J., Herlitz, A., & Bäckman, L. (2004). Preclinical Alzheimer’s Disease: Cognitive and

Memory Functioning. In R. Morris, J. Becker (Eds.), Cognitive Neuropsychology of

Alzheimer’s Disease (pp. 120-140). New York: Oxford University Press Inc.