SAVANT SYNDROME

What is Savant Syndrome?

“Persons with obvious mental [disability] who are capable of performing remarkable feats in sharply circumscribed areas at a remarkably high level”

Grossman 1983

intellectual deficit is marked and broad

remarkable behaviour is extraordinary in normal context

What is Savant Syndrome?

Rare

Severe mental disability

“Island of genius” involving increased memory skills

Link to autism:

10% people with autism have savant syndrome

50% people with savant syndrome have autistic spectrum disorder

Also present in other developmental disabilities or CNS injury/disease

What is Autism?

pervasive developmental disorder

presence of abnormal/impaired development before aged 3 years

abnormal functioning in the three areas of psychopathology:

reciprocal social interaction

communication

restricted, stereotyped, repetitive behaviour

phobias, sleep disorders, eating disorders, temper tantrums and self-directed aggression are all also common

ICD-10 Classification

What is Autism?

ICD-10 uses secondary behaviours

Young et. al., developed the Flinders Observation Schedule of Pre-verbal Autistic Characteristics (FOSPAC):

focussed on pre-verbal behaviour

not dependant on receptive language

objectively measurable

focussed on core deficit-linked behaviours

poor interaction

bizarre responses to external stimuli

repetitive movements

(Young 2001)

Autism Diagnoses

Why Savant Syndrome?

Relevant to psychiatry:

Responsible for increasing awareness of Autism

“Training the talent” as a “Conduit towards normalisation”

Brain function models must include this coexistence of mental disability and exceptional mental ability

Ethical issues surrounding search for a cure

Savant Skills Always related to incredible memory

very deep and narrow, associated with particular skill

Most commonly only one skill

Multiple skills more common in autistic savants

Classification of savant skills

Splinter Skills

most common

obsessions with/memorisation of music, trivia, maps etc.

Talented Savants

ability that is abnormally high in view of cognitive impairment

Prodigious Savants

very rare; <50 currently living

ability considered extraordinary even if viewed in a non-impaired person

Savant Skills

Typically found in the following areas:

musical ability

art

calendar calculating/mathematics

mechanical/spatial skills

Rarer skills:

polyglot

abnormal sensory discrimination

ability to know how much time has elapsed

outstanding knowledge in particular fields

Usually right hemisphere in type

Kim Peek

Macrocephaly, cerebellar damage, agenisis of corpus callosum

First steps aged 4 years

Motor difficulties

Photographic memory

Reading

10 seconds/page

recall 12,000 books

Calendar calculation skills

Learning piano

Sense of humour developing

Daniel Tammet

Autistic savant

Congenital childhood epilepsy

Mathematics, sequence memory, language skills

Synesthesia

π recalled to 22,514 digits

English, French, Spanish, German, Finnish, Lithuanian, Estonian, Icelandic and Esperanto

Created Mänti language

Alonzo Clemons

Head injury as a toddler

Limited language

Clay sculpting talent

20 mins observation of TV image

45 mins per sculpture

Highly accurate

Vocabulary increasing

Improving social competence

More independent

Derek Paravicini

Born 15 weeks premature

0.5 Kg

Oxygen therapy

bind

development affected

Self taught piano

Instantly recall thousands of pieces

Can play in any key

Jazz, Pop & Classical

Improvisation and performance

How does it work?

Numerous theories

None are complete

Eidetic imagery (photographic memory)

not present in all savants

may be simply a marker of brain damage

Inherited skills

not enough evidence for skills in relatives

Rote memory

memory cannot totally explain savant skills (Hermelin 2001)

How does it work?

savant skills tend to be right hemisphere in type

left brain dysfunction : right brain activity in autism

PET scans have shown ↓5-HT synthesis in left hemisphere in autism

(DeLong 1999)

Numerous case examples:

9 year old boy

gun shot wound to left hemisphere

mute, deaf and paralysed

subsequent savant mechanical skill (Brink 1980)

Right hemisphere compensation following left hemisphere injury

How does it work?

Two studies by Miller and Hou:

5 Frontotemporal Dementia patients acquired artistic skills: (Miller 1998)

dominant left hemisphere injury

“Loss of function in the left anterior temporal lobe may lead to the ‘paradoxical functional facilitation’ of artistic and musical skills”

SPECT imaging of 9 year old autistic savant: (Hou 2000)

bilateral ↑frontal lobe perfusion

bilateral ↓anterior temporal lobe perfusion

worse on the left

“The anatomic substrate for the savant syndrome may involve loss of function in the left temporal lobe with enhanced function of the posterior cortex”

How does it work?

rTMS investigations: (Snyder & Mitchell 1999)

used to temporarily halt left hemisphere functioning

5/17 saw ↑in savant-type skills

savant-type skill possible for some, not all

savant processes in the brain occur in everyone but are drowned out by higher functioning cognition

savant syndrome individuals have “privileged access to lower levels of information not normally available through introspection”

How does it work?

However, some argue against this hypothesis:

prosodic features of speech (usually right hemisphere mediated) may be absent in savants

melody recall is associated with left hemisphere

absolute pitch associated with larger planum temporale in left hemisphere

Multiple-site model of autism

autism shows several sites of pathology

one of these sites is the basis for savant skill

temporal and parietal polysensory areas

preservative attention and expanded primary pattern extraction

modality-specific information

predicts only some people with autism will develop savant skills

Savant Syndrome

rare

intellectual deficit

“island of genius”

link to autism

right hemisphere compensation following left hemisphere injury

multiple-site model of autism

possible future advances in our knowledge and understanding

“acquired” savant syndrome

hidden potential in us all?

www.savantsyndrome.com

Darold A. Treffert, MD

ReferencesTreffert, D.A. Savant Syndrome: An Extraordinary Condition – A Synopsis: Past, Present, Future.

Hermelin, B. (2001). Bright Splinters of the Mind. London: Jessica Kingsley Publishers.

Young, R. (2001). Current research in the area of Autism and Savant Syndrome. International Education Journal, 2(4):329-333.

Hou, C., Miller, B.L., Cummings, J. (2000). Artistic savants. Neuropsychiatry Neuropsychol. Behav. Neurol., 13:29-38.

DeLong, R. (1999). Autism: new data suggests a new hypothesis. Neurology, 52:911-916.

Miller, L.K. (1999) The Savant Syndrome: Intellectual Impairment and Exceptional Skill. Psychological Bulletin, 125(1): 31-46.

Snyder, A., Mitchell, D. (1999). Is integer arithmetic fundamental to mental processing? Proc. Royal Soc. London Biol. Sci., 266:587-592.

Miller, B.L., Cummings, J., Mishkin, F. (1998). Emergence of artistic talent in fronto-temporal dementia. Neurology, 51:978-982.

Rimland, B., Fein, D.A. (1988) Special Talents of autistic savants. In: The Exceptional Brain: Neurophysiology of Talent and Special Abilities. Obler, L.K., Fein, D.A., eds. New York: Guilford Press.

Grossman, H. (1983) Classification in mental retardation. Washington, DC: American Association on Mental Deficiency: 179.

Brink, T. (1980). Idiot savant with unusual mechanical ability. Am. J. Psychiatry, 137:250-251.

Giray, E.F., Barclay, A.G. (1977). Eidetic imagery: longitudinal results in brain-damaged children. Am. J. Ment. Defic., 82:311-314.

Acknowledgements

http://www.wisconsinmedicalsociety.org

http://www.derekparavicini.net

Autism graph: www.fightingautism.org

Alonzo Clemons Photos: http://artsales.com/ARTists/Alonzo_Clemons/index.html

http://en.wikipedia.org/wiki/Image:Rain_Man_poster.jpg