Disorders of memory made simple

John O’Donovan

Functional anatomy of cognitive functions

Distributed• Consciousness • Memory • Higher order intellectual

functions, personality and executive functioning

Focal• Dominant versus non

dominant hemisphere

Attention

• ARAS• Thalamus • Hypothalamus • Multimodal association

cortex • Right parietal cortex

Tests of attention

• Orientation • Digit span • Recitation of months of

year or days of weeks • Words forwards and

backwards • Serial 7s

• Remember, if attention does not work then neither does anything else.

Memory

• Very messy-need to know it inside out. • You will have questions on memory as it

covers psychology, neurology and psychiatry.

Episodic

Episodic

Semantic

Memory divisions

Explicit or declarative • Available to conciousness

Implicit or procedural• Not available to

consciousness

Explicit memory

Epidodic• Personal events • Autobiographical events

• Birthday last year?• First kiss?• First job?• What was on TV last night?

Semantic • General knowledge

• Capital of France?• Who wrote War and Peace?• Distance from Exeter to

Plymouth?

Memory divisions

Episodic• Hippocampal formation• Limbic system • Diencephalic system: basal

forebrain and thalamus.

Semantic • Temporal neocortex with

perhaps more verbal semantic memory on left and more visual semantic memory on right.

Implicit

• Motor skills • Basal ganglia • Cerebellum • Riding a bike, car, playing the piano, motor

skills.

Short versus long term memory

• Avoid the term short term memory, it’s a mess.

• Think instead in terms of working memory and long term memory.

• Simple concept of working memory, remembering information for 5-30 minutes

• Working memory is better as a concept.

Working memory and loops

• Central executive probably based in frontal lobes

• Phonological loop to verbal area in dominant hemisphere and visuospatial loop to non dominant loop

• Ongoing simultaneously and not completely independent of long term memory

Retrograde and anterograde memory

• Retrograde: recall of previously learnt material.

• Anterograde: acquisition of new memories.

Where is memory stored?

• Seems that verbal memory is dominant hemisphere

• Seems that visual memory also known as iconic memory is non dominant.

The amnesic syndrome

• Pure deficit in memory. • All other areas more or less intact.

Amnesic syndrome

Acute and transient• TGA• Epilepsy • Closed head injury • Drugs• Psychogenic

Chronic• Hippocampal• Herpes simplex • Anoxia • Surgical resection of temporal lobes• Bilateral posterior cerebral artery

occlusion• Closed head injury • Alzheimer’s disease

• Diencephalic• Korsakoff’s • 3rd ventricle tumours • SAH-ACAM anuerysm

Amnesic syndrome

• 1 generally preserved IQ. • 2 preserved short term/working memory for

example digit span. • 3 anterograde amnesia • 4 retrograde amnesia which is generally more

severe in diencephalic amnesia • 5 preserved procedural/implicit memory

Amnesic syndrome

Diencephalic• Problems with encoding• Problems with retrieval of

memory from long term storage

Hippocampal• The main problem is either

encoding or consolidation, unlikely to be retrieval.

Memory MCQs

Semantic memory• Is constantly acquired • Is intact in Korsakoff’s • Is intact in Alzheimer’s

Disease• Is intact in semantic

dementia • Non dominant temporal

lobe lesions can result in prosopagnosia for famous faces

Episodic memory• Is impaired in Alzheimer’s. • Is the same as

autobiographical memory. • Is normal in poorly

controlled epilepsy• Is intact in Korsakofff’s • Is normal in psychogenic

fugue.

Memory MCQs

Implicit memory• If brought into

consciousness, is then explicit.

• Is affected by cerebellar disease.

• Also has an autobiographical element.

• Is intact in the amnesic syndrome

• Cannot be tested

Short term memory• Has a time limit of 30

minutes• Is the same as working

memory• Is intact in Korsakoff’s • Is a term best avoided due

to imprecision. • Is intact in Alzheimer’s

disease.