#10619 - Introduction To Amnesia. Lec 1docx - Neuropsychology of Memory

Introduction to Amnesia

• Patient H.M. – Scoville & Milner(1957)

• Long history of major + minor seizures + uncontrollable by multiple forms of medication – intractable epilepsy

• Radical bilateral medial temporal lobe resection

• After – incidence + severity of seizures dramatically reduced

• Anterograde memory almost entirely absent + some retrograde loss

• His RA extended approx. between 3+ 11 yrs

Measuring Anterograde Amnesia (AA)

• Wechsler Memory scale personal + current info/ mental control (recite alphabet etc) / logical memory (recall short story)/digit span/paired associate learning/visual reproduction – rey osterrieth figure - draw from memory (potentially dissociable)

• HM memory quotient = 67 – v. deficient

• Rivermead behavioural memory test practical test of everyday memory

• Remembering – name from photo/hidden belonging

• Recognition – 10 line drawings over 5 mins / 10 faces over 5mins

Measuring Retrograde Amnesia (RA)

• Test for public events + famous faces over diff time periods – before onset of amnesia – uncover the extent of the temporal gradient e.g. Squire et al (1989)

• Autobiographical Memory Interview (AMI)

• Assesses recall of facts from person’s life (personal semantic) – standardised e.g. school

• Recall of specific incidents in patients life – episodic – verified by family

• Assesses 3 broad time spans : childhood/early adult life/recent facts + incidents enables you to gauge the temporal gradient

• Advantantages easy to administer / not dependent on level of patient interest in current affairs / does not require regular updating BUT - difficult to know the accuracy of incidents

Spared abilities in amnesia

1. Intellectual abilities – speech + IQ

2. STM/WM

• Baddeley & Warrington (1970) – compared performance of amnesic patients + control ptp’s on immediate and delayed free recall

• Peterson short term forgetting task, paired associate learning , digit span , Hebb digit sequence technique

• Amnesic ptp’s have normal STM but defective LTM

3. Conditioning

• Warrington & Weitkrantz – conditioned eye blink responses in 2 severe amnesics – tone and puff of air conditioned an eye blink in them

4. Priming

• Warrington & Weizkrantz (1970) Gollins incomplete pictures test – line/dot to dot drawings – increasing to full drawings – remember

• Primed and then tested an hour later –could not explicitly remember the image

• Repetition priming – Graf et al. (1984)

• First shown full list of words

• Free recall / cued recall – complete with word from study list / word stem completion with first word come to mind

• Compare free recall to word stem completion – priming effect

• Amnesic poor fee recall – but better than controls on word completion therefore they do remember in a sense

5. Tower of Hanoi (Cohen, 1984)

• Get start position – then target position – have to move the 3 blocks around to get desired pattern

• Amnesics improve over time – normal pattern – no memory of completing task

How do you explain these spared abilities?

• May be skills gained early in life

• Other memory systems affected – taxonomy of memory – Tulving

• Amnesics good non-declarative memory BUT bad declarative

• Is that restricted to episodic or semantic as well ?

Can amnesics learn new semantic info?

• HM used a 1950’s vocabulary – it failed to update – could not define new bords such as biodegradable attempts to teach him 8 new words failed (Gabrieli, Cohen & Corkin, 1983)

• Kitchner et al (1998) case study densly amnesic patient can remember some recent famous faces, + can define somerecently introduced vocab + knowledge of recent events BUT did not acquire semantic info in the normal fashion – slow + laborious – man repetitions - maybe deficit in EM impacting SM (e.g. remember where you were when something happened etc)

• Some semantic knowledge can be acquired in the absence of EM

• But many patients have impairments in acquiring both EM + SM

• Semantic problems may remain unnoticeable in adults – as little semantic info is learned in adulthood

• EM + SM deficits don’t nec have to co-occur – but they usually do

Developmental Amnesia

• Vargha-Khadem et al (1997)

• 3 patients with amnesia resulting from early events

• Profound amnesia for episodic materials

• Still progressing through school – normal IQ + ACADEMIC ACHEIVEMENT

• Able to comprehend passages + could acquire knowledge about the world

• Seems semantic memory can develop in the absence of EM

• SM may develop normally in developmental amnesia – may be an adaptive thing able to cope + adapt – but adults have more difficulties in SM due to EM impairments – more reliant on EM to form SM whereas children adopt coping strategies

Dissociation of Epidosic Memory + Semantic Memory in childhood amnesia: (Vicari et al, 2007)

• C.L 8 yr old child, surgical removal of an ependymoma from left cerebral ventricle at 4yrs

• Found patient who despite being impaired on ability to recollect new episodic info –still demonstrates preserved abilities to acquire new semantic knowledge

• Suggests that neural circuits implicated in the memorisation of autobiographical events + factual info, do not overlap completely

• Functional dissociations in healthy subjects +...