Week 6 - Autism characteristics, diagnosis and prevalence Flashcards
What is meant by the term neurodiversity?
A term used to reflect the range of individual differences in brain function and behavioural traits which is used particularly in the context of autism
What type of condition is autism considered to be?
A neurodevelopmental condition
What is meant by the term neurodevelopmental condition?
A condition which reflects atypical development of the nervous system
What are the two core areas of difficulties used in the current framework for diagnosing autism?
- Social communication
- Non-social aspects of thinking and behaviour
What are the four types of conditions which are often co-morbid with autism?
- Medical
- Genetic
- Neuro-developmental
- Mental health
What medical conditons are often co-morbid with autism?
- Gastrointestinal problems
- Sleep disorders
In autistic people what is the prevalence of co-morbid medical conditions?
Around 30-50%, especially common in people with more severe autism
In autistic people, what is the most common co-morbid genetic condition?
Fragile X Syndrome
In autistic people, what is the prevalence of those with co-morbid neurodevelopmental conditions?
30-80% of autistic children also meet ADHD diagnostic criteria
What are the most common co-morbid neurodevelopmental conditions with autism?
- ADHD
- Dyslexia
- Language difficulties
- Intellectual disability
What are the most common co-morbid mental health conditions with autism?
- Bipolar disorder
- Schizophrenia
- Depression
- Anxiety
What is meant by the term biomarker?
A measurable genetic, biological, pathological or physical characteristic by which a particular disorder or condition can be reliably identified
Are there consistent and/or universal biomarkers for autism?
No
What is the ICD (International Classification of Diseases)?
A global classification system of all medical conditions based on symptoms and other criteria, as developed by the World Health Organisation
What is the purpose of the ICD?
To be a core reference for research, diagnosis and healthcare
What is the one overarching criterion which can be used for any and all autisim diagnoses?
If the observed symptoms are sufficient to undermine the individual’s functioning in everday life
What is meant by the term receptive language?
The process of receiving and understanding language which is spoken or written by othersq
What is meant by the term expressive language?
Language that a person produces, in either written or spoken form
In what year was autism first formally identified?
1944
What is an epidemiological study?
A study which is large-scale and designed to investigate the prevalence, distribution and/or causes or a health problem in one or more populations
Does an increase in the prevalence of autism mean that more people have the condition now?
No - it could just mean that we are diagnosing people who would have gone undiagnosed in the past
Is the prevalence of autism similar across cultures?
No, it varies widely
As prevalence rates for autism vary across countries, what could be a reason for this?
In some countries there may be fewer diagnoses due to the stigma surrounding it
What factors may account for why more boys are diagnosed with autism than girls?
It’s possible that current diagnostic criteria are more readily applied to male behaviour, or that autism in girls is less overtly expressed
What is a systematic review?
A research method involving evaluation of existing evidence for a particular topic or theory
How is a systematic review conducted?
Critical review of all relevant findings by other researchers
What is a meta-analysis?
A research method involving evaluation of existing evidence for a particular topic or theory
How is a meta-analysis conducted?
By pooling and stastically analysing the pooled findings from all relevant research by other researchers
What is a psychometric test?
A test which provides quantitative data of intellectual ability, language skills and other cognitive and behavioural traits
What kind of test is an example of a psychometric test?
An IQ test
What is meant by the term extraneous variables?
All variables that are present in an experimental study that are not the variables under investigation or being measured
What is meant by the term confounding variables?
These are extraneous variables in experiments which may affect the dependent variable, such that clear conclusions about the relationship between the independent and dependent variables cannot be drawn
What is meant by the term theory of mind (ToM)?
The ability to understand other people’s mental states, including the ability to understand that another person’s belief about an aspect of reality may be different from one’s own
In the field of psychology, what is meant by the term false belief?
A belief or representation about the world that may contrast with reality
Which researcher devised the “Sally-Anne” test and when?
- Simon Baron-Cohen
- in the 1980s
What was the “Sally-Anne” test investigating?
The Theory of Mind (ToM)
What is protodeclarative pointing?
The use of pointing to draw someone else’s attention to an object or item of interest, enabling an individual to share their interest with another
What is meant by the term executive function?
Mental processes that control behaviour - including initiating and planning actions, using working memory to implement actions in sequence, sustaining attention and context switching
What are the tasks which executive function is responsible for?
- Initiating and planning actions
- Using working memory to implement actions in sequence
- Sustaining attention to the task in hand
- Context switching
Are executive function difficulties unique to autism?
No
Which other condition encompasses difficulties with executive function?
ADHD
In the field of psychology, what is meant by the term systemising?
A flair for, or strong interest in, approaching fields or topics in a systematic or rule-following way
What is monotropism?
A trait in autism in which an individual focuses their attention on objects and topics that are of particular interest to the individual
What might be an unfortunate consequence of monotropism?
Highly selective learning
What is meant by the term twin method?
A research method used to investigate the relative importance of genetic and environmental factors to traits and conditions in human populations
What is meant by the term concordance rate?
It is the probability that pairs of individuals with shared genes will have the same trait or condition under investigation
In what year, and by which researchers, was the first twin study into autism published?
- 1978
- Folstein & Rutter
What did Folstein & Rutter’s 1978 study find?
A higher concordance rate of autism for identical twins compared to fraternal twins
What is meant by the term broader autism phenotype?
Milder manifestation of traits typical for autism, but not to the extent of meeting the diagnostic criteria
What is the broadly estimated rate of concordance rate for autism in identical twins today?
Identical twin concordance is estimated to be around 77%
What is the broadly estimated rate of concordance rate for autism in non-identical twins today?
Non-identical twin concordance is estimated to be around 36%
What is meant by the term sibling recurrence rate?
The probability of a child having or developing a condition when one or more of their siblings has that condition
Is there a specific gene related to autism?
No
Roughly how many regions of the genome have autism-linked variants?
14 regions
Are all the genetic mutations associated with autism equally ‘harmful’?
No, mutations can be either harmful or benign, depending on how many cells they affect in the body and how much they alter the corresponding protein’s function
What is a mosaic mutation?
One which affects only some of the cells in the body
Are the amount of genetic mutations associated with autism the same in both sexes?
No
What is an SNP?
Single Nucleotide Polymorphism - variations in individual nucleotides within a DNA sequence
What is a CNV?
Copy Number Variation - alterations in the number of copies of a larger DNA segment, potentially spanning multiple genes
What is the main difference between a SNP and a CNV?
SNPs affect single DNA bases whereas CNVs are mutations involving changes to whole sequences of bases
What is meant by the term de novo mutation?
It is a mutation which affects the offspring alone (i.e. was not inherited from a parent)
What is meant by the term candidate genes?
Genes whose functions, or locations on particular chromosomes, indicate that they might be associated with a condition or disorder
What is the most notable candidate gene with regards to autism?
CHD8
What does the CHD8 gene code for?
Gene expression by chromatin remodelling
What is chromatin remodelling?
The reararangement of chromatin from a condensed state to a transcriptionally accessible state
What is the purpose of chromatin remodelling?
To allow transcription factors, or other DNA binding proteins, to access DNA and control gene expression
What genes are the CHD8 gene thought to affect the expression of?
Those involved in fetal brain development
Are CHD8 mutations present in all people with autism?
No
What is meant by the term polygenic?
Mutations in multiple genes
What does the term heterogenous mean?
Different combinations of gene mutations between different individuals and groups
What rare, single-gene condition, is the most commonly co-morbid medical condition to autism?
Fragile X Syndrome
Which gene is associated with Fragile X Syndrome?
FMR1
Mouse models and post-mortem studies of patients with Fragile X Syndrome have discovered what changes?
Abnormal structure and number of dendritic spines
What are dendritic spines?
Neuronal protrusions which recive input from excitatory synapses
What is meant by the term non-syndromic autism?
Autism which is not associated with any non-autism condition
In people with autism, mutations in which genes other than CHD8 have been discovered?
- NRXN1
- NLGN3
- NLGN4
- SHANK3
Roughly, what is the function of the SHANK3 gene?
It plays a scaffolding function within cells and indirectly binds to neuroligin
What is neuroligin?
A protein on the postsynaptic membrane which mediates the formation and maintenance of synapses between neurons
Neurons in which region of the brain synthesise serotonin?
The Raphe nuclei
Roughly, what are the processes that serotonin influences?
- Regulating mood
- Emotions
- Aggression
- Sleep
- Body temperature
Which part of the brain is serotonin critical in the development of?
The cortex
What change has been noted in around 25% of children with autism’s blood?
Unusually high serotonin levels
What protein does the SLC6A4 gene code for?
The serotonin transporter protein
Where does the serotonin transporter protein transport serotonin from and to?
From the presynaptic cleft to the presynaptic neuron
What is the end result of the action of serotonoin transporter protein?
Transporting serotoinin from the presynaptic cleft to the presynaptic neuron terminates the action of serotonin at the synapse
Which protein terminates the action of serotonin at the synapse?
SLC6A4 - Serotonin transporter protein
What is a key function of GABA?
GABA has the primary inhibitory effect in the brain
What is a key function of glutamate?
It has an excitatory effect on post-synaptic neurons and is considered crucial in neural plasticity and cognitive functions such as learning and memory
Which neurotransmitter is considered crucial in neural plasticity and cognitive functions such as learning and memory?
Glutamate
Which neurotransmitter has the primary inhibitory effect in the brain?
GABA
Abnormal levels of GABA and glutamate have been reported in persons with which condition?
Autism
An atypical trajectory of brain growth has been noted in persons with which condition?
Autism
Roughly what percentage of children with autism were noted to have an aytpical brain growth trajectory?
20%
What is the approximate age range for when excess brain growth may be observed in children who are later diagnosed with autism?
From six months to four years
Which areas of the brain has excess brain growth in perons with autism especially noticeable in?
Frontal and temporal lobes
As well as the frontal and temporal lobes, atypical brain growth in persons with autism has also been found in which other areas?
- Amygdala
- Cerebellum
The amygdala forms an integral part of which system?
The limbic system
The amygdalae play a key role in what functions?
Forming and storing memories associated with emotional events
As well as movement, what other functions is the cerebellum involved in?
- Language
- Attention
- Mental imagery
Dendritic pruning failing to occur, or being substantially reduced during a critical period of development has been found in persons with which condition?
Autism
What is the effect of reduced or absent dendritic pruning?
Excess neurons and neuronal connections, meaning that circuits which operate in an inefficient way
In some autistic children, the prefrontal cortex shows how much more brain tissue?
67%
What are the four brain regions in which excess brain growth in patients with autism is especially marked?
- Frontal lobes
- Temporal lobes
- Amygala(e)
- Cerebellum
Higher neuronal hyperconnectivity in persons with autism are associated with what problem?
Greater daily living challenges
What is the association cortex?
The regions located in all lobes of the cortex that, through their interlinking, support high level integrative activites (eg comparing sensory inputs to stored memories)
Which part of the brain is associated with comparing sensory inputs to stored memories?
The association cortex
Limbic structures support which key functions?
- Emotional recognition and expression
- Memory
- Motivation
- Olfaction
What are the structures which form the limbic system?
- Amygala
- Hippocampus
- Thalamus
- Hypothalamus
What is the core structure of the paralimbic system?
The amygdala
What functions are controlled by the orbitofrontal cortex?
- Decision making
- Processing the emotional aspects of decision making
- Understanding other people’s emotions
Where is the orbitofrontal cortex located?
Within the frontal lobes
What does the left hemispheric gyrus play a key role in?
The processing of speech, language and gesture
Altered function of the inferior frontal gyrus is implicated in what type of problems?
Difficulties with both verbal and non-verbal communication
What functions does the posterior parietal cortex play a role in?
- Spatial awareness (e.g. perceiving and remembering where objects are located)
- Controlling eye movements
- Maintaining attention
Enhanced skills in visual tasks in persons with autism may be as a consequence of atypical activation in which brain region?
Posterior parietal cortex
Around which other structure of the brain does the cingulate gyrus wrap around?
The corpus callousm
What does the anterior part of the cingulate gyrus play a role in?
- Coordinating sensory stimuli with emotions
- Emotional expression and bonding
- Regulating aggressive behaviour
- Decision making
What is the posterior part of the cingulate gyrus involved in?
- Processing the spatial orientation of objects
- Mediating between emotions and memories
Altered function of the cingulate gyrus may lead to what symptoms in those with autism?
- Social and emotional challenges
- Repetitive behaviour
Behind which other structures does the anterior cingulate cortex lay?
The frontal lobes
What functions is the anterior cingulate cortex involved in?
- Coordinating sensory stimuli with emotions
- Emotional expression and bonding
- Regulating aggressive behaviour
- Decision making
Where is the superior temporal sulcus located?
Within the outer surface of each temporal lobe
The anterior part of the superior temporal sulcus is involved in which function?
Processing speech
The posterior part of the superior temporal sulcus is involved in which function?
- Processing faces
- Movement
- Direction of gaze
- Integrating audio and visual information
Atypical function of the superior temporal sulcus has been implicated in which type of difficulties in autism?
Social and theory-of-mind difficulties
The fusiform gyrus spans the lower part of which parts of the brain?
- Temporal lobes
- Occipital lobes
Atypical function of the fusiform gyrus is linked with which two neurological conditions?
- Prosopagnosia
- Synaesthesia
Within which brain structure is the amygdala located?
The medial temporal lobe
Which system of the brain is the amygdala integral to?
The limbic system
Through which structures does the amygdala coordinate its activities?
- Prefrontal cortex
- Cingulate gyrus
- Thalamus
- Hypothalamus
- Hippocampus
What difficulties in autism have been linked to atypical function of the amygdala?
- Anxiety
- Emotional regulation
What region of the brain is adjacent to the amygdala?
The bilateral hippocampus
The hippocampus works as part of which system of the brain?
The limbic system
What does the hippocampus play a key role in?
Storing and retrieving memories for personal experiences and factual information
Atypical function of the hippocampus may lead to what difficulties in autism?
Recalling or acting upon peronally salient events
Which structure lies below the thalamus?
The hypothalamus
The hypothalamus is part of which brain system?
The limbic system
The hypothalamus is involved in the release of which pituitary hormones?
- Oxytocin
- Vasporessin
What is the role of the hypothalamus?
Controlling emotional expression
Atypical function of the hypothalamus may lead to what difficulties in autism?
- Social interaction
- Emotional
Which structure does the bilateral thalamus lay close to?
The amygdala
What is the role of the thalamus?
- Processing and relaying sensory information to cortical areas
- Relaying cortical feedback to movement areas
- Controlling attention
- Sleep
- Wakefulness
Atypical function of the thalamus may lead to which difficulties in autism?
- Regulation of social behaviour
- Sensory hyper/hypo-sensitivity
- Sleep disturbances
What structures does the cerebellum lay below?
- Temporal lobes
- Occipital lobes
The cerebellum lays posterior to which other brain structure?
The brain stem
What is the function of the cerebellum?
- Generating and controlling motor movements
- Vocalising sounds
- Attention
- Mental imagery
What is atypical function of the cerebellum linked with in autism?
Compromised development of social communication skills and executive function
The pons is part of which structure of the brain?
Brain stem
The pons relays information from where to where in the brain?
To and from the cerebellum, cerebrum and spinal cord
The basal ganglia are structures in which area of the brain?
The mid-brain
Atypical function of the basal ganglia in autism may lead to what difficulties?
Impeded action selection and difficulty in engaging with others
