Transcript Autism - UCSD Cognitive Science

No Theory of Mind
Weak Central Coherence
Executive Dysfunction
Cortical Abnormalities
• Whole Brain is heavier than expected <12 years
and lighter than expected in adults
• Structural Abnormalities
– Mini-Column abnormalities
• a basic functional unit of the brain that organizes neurons in
cortical space and are involved in sensory information
processing
• Mini column is a core line of neurons ascend vertically
between layers VI and II of the cortex
– Less GABA-ergic interneurons which are source of lateral
inhibition
– More immature dendrite arborizations and synapses
» Prefrontal and Orbitofrontal cortices
» Temporal lobe- Visual and Auditory parasensory areas
Subcortical Abnormalities
• Limbic system (amygdala, hippocampus,
and related structures)
– Smaller and more immature neurons with
reduced dendrite arbors
• More pronounced abnormalites in the
amygdala and then hippocampus
– Often find larger amygdala volumes,
suggesting incomplete neuronal pruning
– Often find smaller amygdala with age,
suggesting cell death
Role of Hippocampus
• Lesions to the hippocampus produce
deficits in declarative memory
• It is more slow to mature
• It is suggested that disruptions to the this
system could disrupt or distort acquisition
and interpretation of information
• Smaller in autistic
Motor Abnormalities
• Cerebellum and brain stem have
significant reduction in number of Purkinje
neurons
• Cerebellum involved in visuo-spatial
processing, emotional processing, and
motor processes
Neurotransmitters in Autism
• Hypo-serotonin
– 7 possible mechanism (this is for you to
study)
– Reducing serotonin results in increase in
stereotypical behaviors, but no change in
social deficits.
– Treatment with SSRIs result in reduction of
aggressive and ritualistic behaviors
– PET studies found decreased SER synthesis
in cortex and thalamus of autistic individuals
Autism
• CMI superior to desipramine in reducing ratings of
autistic symptoms of stereotype behaviors, ritualized
behaviors, anger. Both TCAs equal and superior to
placebo in reducing hyperactivity
• Haldoeridol (DA antagonist) superior to placebo in
reducing steretypy and withdrawal
-combo with BTincreased effectiveness of language
learning
• Beta blockers (NE system) decreased aggression and
levels of arousal, however, need better studies
Structural Conclusions
• Abnormalities in neuronal alignment,
elaboration, pruning, and selective elaboration of
appropriate neurons in the cerebral cortex.
• Abnormalities of dendritic and axonal
arborations in the limbic system
• Selective elimination of neurons in the
cerebellum
• Abnormalities suggest onset of abnormal brain
development during 2nd trimester of gestation
• Selective core involvement of the amygdala and
entorhinal cortex may be involved in social
deficits.
Amygdala: Functions
• Recognition of affective significance of
stimuli
• Social stimulus-reward associations
• Cross modal associations
• Long term memory (especially related to
emotion)
• Perception of body movements
• Perception of gaze direction
• Perception of emotion
Circuitry of Austim
• Cortical regions in the temporal lobe
participate in perceiving socially relevant
stimuli; Amygdala, right somatosensory
cortex, orbitofrontal cortices and cingulate
cortices participate in linking perception of
these stimuli to motivation, emotion, and
cognition.
Role of the Cortex
• Prefrontal Cortex and posterior superior
temporal sulcus are involved in
“mentalizing” which is lacking in Autistic
patients
• PFC is found to actively modulate
extinction of amygdala related aspects of
memory
Role of the Amygdala in Autism
• PET and MRI Studies
– Increase activity in normal subjects when
viewing happy, and fearful expression in
contrast to viewing neutral faces. Not found
in Autistic patients
– Autistic patients appear to not be able to
differentiate between threatening and nonthreatening stimulus
– Found smaller amygdala and hippocampus in
autistic patients