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The amygdala is a deep brain structure the size and shape of an almond - from which it gets its name. It is commonly described as a center for detecting environmental threats and processing fear and other emotions.
Researchers studying the region argue that its function is broader — and that it plays a crucial role in autism.
"Emotions are such an important part of social functioning," he saysWei Gao, Associate Professor of Biomedical Sciences at Cedars-Sinai Medical Center in Los Angeles, California. "So I think the amygdala has to play a big role in the emergence or development of autism-related traits."
The amygdala is the brain's alert center: it's involved in recognizing when someone is approaching with an angry face and hostile body language, sounding the alarm when a bee buzzes by, and paying attention when your mother is teaching you how crossing the street safely and pointing back. which direction the traffic will come from - i.e. things to avoid, but also things to look at, pay attention to and remember.
In that sense, the researchers say, this tiny knot of brain tissue shows how closely intertwined emotions and social behavior are for humans. "Significant events tend to be emotional in nature," like most aspects of social behavior, he says.John Herrington, Assistant Professor of Psychiatry at Children's Hospital of Philadelphia, Pennsylvania.
As a result, the amygdala has been the focus of autism research, but its exact role in the condition remains unclear.
To understand how this tiny structure contributes to autism, researchers may need to take a broader look - how the amygdala evolves over time; their connections to larger brain networks; and its role in other conditions, in particularAngstthat are often associated with autism.
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As early as the 1950s, studies in primates suggested that the amygdala is a key element of social behavior. When the most dominant ape in a social group suffers damage to its amygdala, its rank in the hierarchy quickly plummets.
People with amygdala damage have social behaviors reminiscent of autism, such as avoiding eye contact and difficulty judging facial expressions, butdo not meet the diagnostic criteriafor the condition. Altered amygdala structure or function has been linked to almost every neuropsychiatric disorder, from anxiety and bipolar disorder toschizophrenia, making it difficult to say how the region may uniquely explain autistic traits.
Beginning in the 2000s, post-mortem studies of autism have shown that autistic people have fewer neurons in their amygdala than controls.1. And some imaging studies have shown that the structure in the brain of autistic people is extraordinarily small.2. But others suspect that children with the condition often have an enlarged amygdala.3.
These seemingly contradictory results may be due to differences in the age of the study participants.
"A lot of the structural imaging studies show amygdala enlargement in young children, but not in older children," he says.Christine Wu Nordahl, Associate Professor of Psychiatry and Behavioral Sciences at the University of California, Davis MIND Institute.
In normal people, the amygdala grows longer than other brain regions into adulthood. In people with autism, on the other hand, it grows faster than normal in early childhood until around age 12, and then gradually decreases and may even decrease.
“It's not necessarily a single different point in time in people with autism; it's really more of a growth trajectory," saysCynthia Schumann, Associate Professor of Psychiatry at the University of California, Davis.
Schumann's studies of postmortem brain tissue show the same pattern: the amygdala in autistic childrencontains more neuronsthat make more connections than controls; this excess disappears in older children.
EmotionAttention:
In 2000, the British researcherSimon Baron-Cohenpublished an influential article on his "Amygdala Theory of Autism".4.
But the picture soon became more complex. For example, a 2005 study showed that when assessing facial expression, autistic people show less activation in their amygdala than controls. However, when they gaze into the eye region of a face, their amygdala glows brighter than that of the controls. In fact, there is evidence that your difficulty interpreting emotions may be due to thisexcessive amygdala activation.
However, the amygdala is not the only center for processing emotions. “More and more evidence suggests it doesn't work on its own; In fact, it acts as a hub for a large distributed network,” says Gao.
For example, the amygdala is connected to the hippocampus to mark emotionally important events in memory, to the brainstem to coordinate fight-or-flight responses to dangerous situations, and to theprefrontal cortexto modulate and control emotional responses.
make connections:
Some studies suggest that weak connections between these regions may explain social difficulties in autistic people.
For example, in a 2016 publication, Nordahl and colleagues reported that autistic boys with the weakest connectivity between these regions also have themmore severe autism features. In a follow-up study published this year, they showed that altered amygdala connectivity is more pronounced in autistic girls than in autistic boys.5.
Connections between the amygdala and the prefrontal cortex, a region involved in orchestrating complex tasks, appear to be particularly important in regulating emotions and are weaker in people with autism.6.Kevin Pelphreyand his team are investigating whether cognitive behavioral therapystrengthen these connections.
The connections between the amygdala and the prefrontal cortex likely have roots in childhood and early childhood. In newborns, the amygdala has strong connections to the sensory and motor regions of the brain. This is a surprising finding since there are relatively few long-distance connections in the newborn brain, Gao says.
But during the first two years of life, the amygdala's connections to these sensory and motor areas decrease and the amygdala forms.Connections to the prefrontal cortexthat look like the circuits responsible for regulating emotions in adults. "This may be the critical period for this ability to emerge," says Gao. It is also the time when the first signs of autism appear.
connect fear:
Some researchers are studying connections between the amygdala and disorders that often coexist with autism. But the growing recognition that autism often isaccompanied by fearpresents a new puzzle for scientists studying the amygdala: Social difficulties in autistic people are associated with decreased activity in the amygdala, but anxiety is associated with increased activity in the region.
In a 2016 imaging study, Herrington and colleagues found that the amygdala appears to be more involved in anxiety than social difficulties in people with autism.7. The following year they showed that children whoautism and anxietyhave a smaller amygdala than controls, but this region is average in size only in autistics.
"Perhaps the amygdala does something different in these children," says Nordahl.
Nordahl's studies suggest that gender could also be a factor. Under 3-year-olds with autism,girl with fearthere is aenlarged right amygdala, but boys with fear don't. (In boys, part of the prefrontal cortex appears to be associated with fear.)
To uncover the connections between autism, anxiety, and other emotions, it may be necessary to take a closer look at the amygdala. Although the amygdala is a small structure, it is made up of subunits, each with different cell types, chemistry, and connections. "It could be that a part of the amygdala involved in social behavior is distinct from a part of the amygdala involved in emotional processes," says Herrington.
Researchers have been working to develop techniquesdistinguish different partsof the amygdala in imaging and other studies that could help separate their different functions. One such study suggests that a piece of the amygdala called the basolateral nucleus may beassociated with feareDepressionin autistic children.
But analyzing these amygdala subunits is difficult, Herrington says: "It's very challenging and at the very extreme limit of what technology can offer us at this point — which sucks if you're someone like me."
FAQs
Does the amygdala play a role in autism? ›
The amygdala — a brain structure enlarged in two-year-old children diagnosed with autism spectrum disorder (ASD) — begins its accelerated growth between 6 and 12 months of age, suggests a study funded by the National Institutes of Health.
What part of the brain controls autism? ›The prefrontal cortex is part of the brain's outermost cortical layer, comprising roughly one-third of all cortical gray matter. It is the part of the brain involved in social, language, communication, affective and cognitive functions – functions most disrupted in autism.
What is the role of the amygdala? ›The amygdala is commonly thought to form the core of a neural system for processing fearful and threatening stimuli (4), including detection of threat and activation of appropriate fear-related behaviors in response to threatening or dangerous stimuli.
Is the amygdala responsible for threat? ›The amygdala is the part of the brain responsible for this reaction. When a person feels stressed or afraid, the amygdala releases stress hormones that prepare the body to fight the threat or flee from the danger. Common emotions that trigger this response include fear, anger, anxiety, and aggression.
Does the amygdala control sensory signals? ›The amygdala combines many different sensory inputs. Like the hippocampus it combines external and internal stimuli. Every sensory modality has input. These are integrated with somatosensory and visceral inputs—this is where you get your “gut reaction”.
How does amygdala dysfunction explain ASD? ›Given that the amygdala is a component structure of the “social brain,” several theoretical explanations compatible with amygdala dysfunction have been proposed to account for socio-emotional impairments in ASDs, including abnormal eye contact, gaze monitoring, face processing, mental state understanding, and empathy.
Is autism detected in the brain? ›About 1 in 44 children are diagnosed with autism by the time they are 8 years old. Researchers say MRI scans can identify differences in the brains of fetuses that could be early indicators that a child will be diagnosed with autism spectrum disorder.
What happens in the brain to cause autism? ›Deviant brain growth in autism occurs at the very time when the formation of cerebral circuitry is at its most exuberant and vulnerable stage, and it may signal disruption of this process of circuit formation. The resulting aberrant connectivity and dysfunction may lead to the development of autistic behaviors.
What part of the brain is affected with ADHD and autism? ›Conclusions: ASD and ADHD are functional alterations of the cerebral cortex, which present structural anomalies in the arrangement of neurons, in the pattern of connections of cortical columns and in the structure of dendritic spines. These alterations affect mainly the prefrontal cortex and its connections.
What are the 3 main thing the amygdala help us do? ›Shown to perform a primary role in the processing of memory, decision making, and emotional responses (including fear, anxiety, and aggression), the amygdalae are considered part of the limbic system.
What disorders are associated with the amygdala? ›
The amygdala collects pathological proteins, and this fact can be considered to play a big role in the progression and diagnosis of many degenerative diseases, such as Alzheimer's disease, chronic traumatic encephalopathy, Lewy body diseases, and hippocampal sclerosis.
How does the amygdala regulate emotion? ›The amygdala contributes to these fear circuits in two ways: directly, by detecting the threat on an unconscious level and regulating behavioral and physiological responses, and indirectly, through cognitive systems, in the emergence of a conscious feeling of fear.
What happens when the amygdala detects a threat? ›If the amygdala senses danger, it makes a split-second decision to initiate the fight-or-flight response before the neocortex has time to overrule it. This cascade of events triggers the release of stress hormones, including the hormones epinephrine (also known as adrenaline) and cortisol.
What part of the brain is responsible for threat detection? ›The job of the amygdala, part of the limbic system, is to assess stimuli (especially threats) and initiate an appropriate response.
Which part of the brain is responsible for fear and threat detection? ›The fear response starts in a region of the brain called the amygdala. This almond-shaped set of nuclei in the temporal lobe of the brain is dedicated to detecting the emotional salience of the stimuli – how much something stands out to us.
Does the amygdala control fear response? ›Together, these findings indicate that the amygdala plays an extensive role in regulating the fear response in humans as well as animals.
Does the amygdala control attention? ›The dual route of affective perception.
The amygdala plays a role in both early and late emotion processing. Attention has only an influence on late emotion processing and thus on amygdala activation.
Amygdala has neural circuits to carry out its different functions with two major output pathways; the Dorsal route via stria terminalis that projects to the septal area and hypothalamus, and the ventral route via the ventral amygdalofugal pathway which terminates in the septal area, hypothalamus, and the medial dorsal ...
How is the amygdala involved in the detection of fear? ›Fear stimuli engage a subcortical network of structures that is centered on the amygdala and that can activate fear responses via an automatic, subcortical, route. As a result of amygdala activation, the fear response is recruited and attention is drawn to the eliciting stimulus.
What behaviors would be affected if the amygdala was damaged? ›The amygdala in particular controls the body's response to fear and emotional and behavioral regulation. When the amygdala sustains damage, it can cause difficulty with memory processing, emotional reactions, and decision-making.
Which disorder is associated with an increase in activity in the amygdala? ›
Hyperreactivity of the amygdala has been observed in adults with posttraumatic stress disorder (PTSD) in response to reminders of traumatic events18,19 and to general negative stimuli.
What brain scan shows autism? ›Magnetic resonance imaging (MRIs) of healthy volunteers and individuals with autism show differences in the volumes of multiple brain regions including: The frontal cortex, which is involved in social and cognitive (intellectual) functions tends to be thicker.
How is autism detected? ›Diagnosing autism spectrum disorder (ASD) can be difficult because there is no medical test, like a blood test, to diagnose the disorder. Doctors look at the child's developmental history and behavior to make a diagnosis. ASD can sometimes be detected at 18 months of age or younger.
How is an autistic person's brain different? ›Others have found that autistic children have enlarged amygdalae early in development and that the difference levels off over time2,4. Autistic people have decreased amounts of brain tissue in parts of the cerebellum, the brain structure at the base of the skull, according to a meta-analysis of 17 imaging studies5.
Can autism be caused by head trauma? ›Can a brain injury cause autism? While many symptoms of TBI and autism overlap, there is currently no evidence to suggest that a brain injury causes an increased risk of autism. However, because the two conditions are similar, some of the interventions used to manage autism may also be helpful for TBI patients.
Which parent carries autism gene? ›Due to its lower prevalence in females, autism was always thought to have a maternal inheritance component. However, research also suggests that the rarer variants associated with autism are mostly inherited from the father.
What has caused the increase in autism? ›Advances in diagnostic capabilities and greater understanding and awareness of autism spectrum disorder seem to be largely driving the increase, the Rutgers researchers said. But there's probably more to the story: Genetic factors, and perhaps some environmental ones, too, might also be contributing to the trend.
What part of the brain is underdeveloped with ADHD? ›Studies have found that ADHD is associated with weaker function and structure of prefrontal cortex (PFC) circuits, especially in the right hemisphere. The prefrontal association cortex plays a crucial role in regulating attention, behavior, and emotion, with the right hemisphere specialized for behavioral inhibition.
What are the two main functions of the amygdala in relationship to anxiety disorders? ›The amygdala is responsible for the expression of fear and aggression as well as species-specific defensive behavior, and it plays a role in the formation and retrieval of emotional and fear-related memories.
What happens if you don't have an amygdala? ›What happens if the amygdala is damaged? You'll probably experience irritability, strong emotions, and even confusion. Problems with the amygdala aren't as rare as you might think. If you struggle with anxiety or a stress-related clinical diagnosis, for example, your amygdala might not be as healthy as it could be.
What is the primary role of the amygdala quizlet? ›
What is the role of the amygdala? emotional regulation, Emotion and social behavior, emotions and perception, and emotions and memory.
Is the amygdala affected by ADHD? ›Conclusion: Patients with ADHD tend to have smaller amygdala volumes. ADHD patients presented less activation in the area of the left frontal pole than the controls.
What calms the amygdala? ›Mindfulness. Use meditation or controlled breathing to focus your body's energy. This will help you respond to a threat or stress in a peaceful way. It will help you stop an amygdala hijack so you can retain control.
Does amygdala trigger anxiety? ›The Chain Reaction of Anxiety
The amygdala initiates the brain processes that create both fear and anxiety. It has long been known that animals without amygdala do not make fear responses.
Autistic children with traditional anxiety had significantly larger amygdala volumes compared to the non-autistic children. The opposite was true for autistic children with autism-distinct anxieties: They had significantly smaller amygdala volumes.
Is the amygdala the fear center of the brain? ›Many of their studies begin with the amygdala, an almond-shaped structure that is considered the hub for fear processing in the brain.
Is anxiety specific to autism linked to amygdala differences? ›People who experience an autism-specific form of anxiety also tend to have an unusually small amygdala, a brain region associated with emotion processing and fear, according to a new unpublished study.
Does autism involve amygdala and hippocampal abnormalities? ›Thus, it is of great importance to identify imaging-based biomarkers for early diagnosis of ASD. Previous findings indicate that an abnormal pattern of the amygdala and hippocampal development in autism persists through childhood and adolescence.
Does amygdala development diverges in autism specific anxiety? ›The amygdala — which is involved in fear and emotion processing and comprises a small region in each brain hemisphere — develops differently in autistic children with anxiety than in either those without anxiety or non-autistic children, according to a new study.
Do people with Aspergers have smaller amygdala? ›Brain autopsy research has shown that both Asperger's people and the highest functioning people with autism have a small amygdala; in cases of low-functioning people, by contrast, the amygdala is more normal and the hippocampus more abnormal.
Why do autistic people get so anxious? ›
Difficult social situations and sensory environments can increase stress and increase anxiety for autistic people. Another significant cause of anxiety is a sense of being misunderstood and/or not accepted by non-autistic people. To 'fit in' and not be seen as different, autistic people might mask or camouflage.
What part of the brain doesn't work with autism? ›People who lack all or part of one white matter tract called the corpus callosum, which connects the brain's two hemispheres, have an increased likelihood of being autistic or having traits of the condition10.
What happens if you have a smaller amygdala? ›Conclusions: These findings suggested that the smaller volume of the amygdala may be associated with anxiety in panic disorder.
Is amygdala responsible for anxiety disorder? ›The amygdala has a central role in anxiety responses to stressful and arousing situations. Pharmacological and lesion studies of the basolateral, central, and medial subdivisions of the amygdala have shown that their activation induces anxiogenic effects, while their inactivation produces anxiolytic effects.