Autism Spectrum Disorder

Autistic DisorderAsperger’s DisorderPervasive Developmental Disorder Not Otherwise Specified

(PDD-NOS)

ASD {

Pervasive Developmental Disorder (PDD)

Deficits in social relatedness, communication and restricted interests/behaviours

Non-clinical Severe

Background

Autism Spectrum Disorder (ASD)

SPECTRUM

-Highly heritable-3-4 males for every female-1/110 estimated prevalence

Domains of Impairment in ASD

Domain Autism Asperger's PDD-NOS ASD

social communication required required required  

language required   variable  

repetitive, restrictive behaviours required required variable  

sensory abnormalities >90% 80% variable 94%

developmental regression 15-40% ? ? 15-40%

motor signs 60-80% 60% 60% 60-80%

gross motor delay 10% ? ? 5-10%

sleep disturbance 55% 5-10% 40% 50%

gastrointestinal disturbance 45% 4% 50% 4-50%

epilepsy 10-60% 0-5% 5-40% 6-60%

comorbid psychiatric diagnosis 70% 60% >25% 25-70%

Geschwind, Ann Rev Med (2009)

Comorbidity in ASD

Disorder %Depression 19.6

Generalized Anxiety Disorder 14.3Social Phobia 10.7

Obsessive Compulsive Disorder 3.6Panic Disorder 3.6Agoraphobia 3.6

ADHD 16.1Oppositional Defiant Disorder 10.7

Tics/Tourette's 1.8Catatonia 1.8

Autism SPECTRUM Disorder

SocialAloofPrefers to be aloneDifficult to engage

Likes to interactWants friendsDoesn’t “get” social rules

CommunicationLimited communicationUses only physical means

Conversational languageOne sided conversations

Restricted Activities/InterestsSensory/Motoric(e.g. spinning, tapping)

Routines/focused interests(e.g. obsession with calendars)

Brain Size

(Mraz et al. 2007)

Accelerated rates of brain growthduring early development

Result: An increase in the ratio oflocal relative to long distanceconnections

Areas most affected:Frontal and Temporal Lobes

ASD: 3 stages of brain growthovergrowth, arrest, decline

Sensory Systems - Visual

CC

CC+

Ashwin et al. (2009)

Freiburg Visual Acuity and Contrast Test-gaps 0.4 mm to 25 mm-use arrow keys to indicate location of gap

-visual acuity expressed in the form 20:x-average vision is 20:20 or the detail that one can see from 20 feet away

Sensory abnormalities and/or sensory hypersensitivity in ASD

Documentation of both superior and inferior sensory processing

(Ashwin et al. 2009)

AVG = 2.79

AVG = 1.44

-ASD group 2.79 times better than average-Visual Acuity Controls: 20:13-Visual Acuity ASD: 20:7

ASD group can see detail of an object 20 feet away as a person with average vision would see from 7 feet away!

ASD visual acuity approximates thatof birds of prey.

Results:

Sensory Systems – Visual

Sensory Systems - Auditory

Also …People with ASD have

normal to superior performance in pitch

discrimination and music abilities

Increased perception of loudness in ASD

(Khalfa et al. 2004)

Sensory Systems

-Abnormalities in the integration of parts and wholes -Local range over-connectivity-Sensory hypersensitivity

-could affect information processing that could cause distressbut could also predispose to unusual talent

Theories?

-a subgroup of those with ASD with profound expertise or ability

-more prevalent in ASD than any other neurological group

Savantism

The Extreme Male Brain Theory

(Falter et al. 2008)

ASD group preformed betteroverall as compared to controls

Females good at empathizingMales good at systemizing

Men out preform women on tasks requiring systemizinge.g. visuospatial tasks

ASD brain believed to be anexaggerated form of the male brain

Recall the mental rotation task:

Face ProcessingPierce et al. 2001

Face Perception Task

Fusiform gyrus, superior temporal sulcus and amygdala activation in controls.Lack of this activation in the ASD group.

Conclusion: Face processing occurs outside the FFA in ASD

Face ProcessingPierce et al. 2004

Face Processing Task Amended-used stranger AND familiar faces

Results:With familiar faces, normal FFAactivity was found in the ASD group

ASD group showed similar network activation to controls only to familiar faces

Amygdala can be responsive in ASD in the presence of stimuli that is of highemotional value

Conclusion:ASD related FFA dysfunction may reflect deficitsin systems that modulate the FFA rather thanthe FFA itself.

LanguageLanguage and communication deficits a core feature of ASD

Difficulties with:Pragmatics – problems using language within a social contextArticulation - poor oro-motor controlProsody – speaking with monotone or an exaggerated singing prosodySemantics – difficulty understanding the meanings of wordsGrammar – pronoun reversal; speaking in grammatical sentences

Echolalia: repetition of another person’s spoken words

Language

Broca’s Area: production of speech

(Fosse et al. 2004)

Reversed asymmetry of Broca’s area(R>L) in language-impaired ASD and those with a specific language impairment

Volumetric Analysis of Broca’s area

Symmetry reversal of Broca’s Area is more closely related to a languageimpairment than to a diagnosis of ASD

LanguageHarris et al. 2006

Semantic Processing Task-Subjects indicated whether a word was +/- (Semantic) or whether a word was in upper/lower case (Perceptual)

ResultsReduced Broca’s area activation for ASD group during semantic processing

Conclusion

Autism…. It is complex and complicated

Just trying to put the puzzle together one piece at a time!