#synaptic pruning

[jadefarringtonlaunceston]

This probably won't come as news to most people following me, but research confirms that autistic people have unique brain wiring.

Some people consider autism to be a set of difficulties, characterised only by a list of behaviours in the Diagnostic and Statistical Manual of Mental Disorders (DSM) and similar.

Being autistic isn't a disorder or condition. The way autistic people's brains are wired exists independently of any decision to reduce it to a list of distressed behaviours and supposed 'deficits' and put these in a manual. It's a naturally occurring neurotype and autistic people have different social and communication styles and sensory experiences.

People are born autistic and that cannot be changed or cured. Nor do most autistic people want it to be. No one can become autistic at a later stage - though many autistics are only identified in adulthood or not at all.

Trauma Geek - Trauma and Neurodiversity Education has written about how being autistic or ADHD results in differences in the way synaptic pruning occurs. These differences in wiring have been found to show up in scans.

Autism research is still heavily biased towards searching for causes and cures, despite the fact that surveys of autistic people show their priority for research is mental health and wellbeing. This latest research highlights the need to stop wasting huge amounts of time and money on the former and shift to what autistic people actually want. It could also have big implications for diagnostic procedures.

Read more:

Autism research finds autistic brains are wired differently

What is a neurotype?

Trauma Geek on synaptic pruning differences in autistics and ADHDers

The research paper, TW for disorder language

Do autistic researchers focus on the things autistic people want them to?

Why I choose not to use the terms ASD or ASC

[neuroscience-corner]

The most puzzling question about schizophrenia is why it typically occurs during late adolescence and early adulthood (earlier in men and later in women). This is where the second period of synaptic pruning was discovered to happen. Structural neuroimaging studies indicate that persons with schizophrenia show prominent progressive brain changes at this time. The decrease in white and grey matter volume was found in patients with schizophrenia, most pronounced 2 years after their first episode. The researchers hypothesise that schizophrenic brains are “over-pruned,” and this over-pruning is caused by genetic mutations that affect the synaptic pruning process. There is some evidence for that in other disorders - for instance, it was found that people with mental disorders had fewer synapses in the prefrontal region compared to the brains of people without mental disorders. Post-mortem brain tissue and DNA from more than 100,000 people was analysed and it was found that people with schizophrenia have a specific gene variant that may be associated with an acceleration of the process of synaptic pruning. Neuropathologic studies in persons with schizophrenia, however, indicate that there is no actual loss of neurons but that alterations in neuronal density and decreased neuronal size may account for the reductions in grey matter in persons with the disorder. It also may be related not to the syndrome itself but to the medication used to treat it - synaptic pruning might be a side effect of that.

[aeontimaeuscrux]

Cognitive Pruning

Definition: Cognitive pruning is a cognitive phenomenon in which the human brain selectively eliminates or weakens less relevant or less frequently accessed memories and information to make room for the retention and consolidation of more important or frequently used knowledge and experiences. It is an adaptive process that helps optimize memory resources and prioritize information based on its significance and utility.

Cognitive Pruning aligns with the concept of “Epistemic Relevance” in epistemology, the branch of philosophy concerned with knowledge and belief. Epistemic relevance explores how individuals determine which information is relevant to their beliefs and understanding of the world. Cognitive pruning can be seen as a practical manifestation of this philosophical concept, as it reflects the brain’s innate ability to discern and prioritize information deemed relevant to one’s cognitive processes.

“In the labyrinthine meadows of memory, the mind becomes an efficient gardener, trimming away the overgrown vines of trivial recollections to nurture the blooming roses of knowledge. Cognitive pruning, the brain’s art of forgetting, is the sculptor of our mental landscape, ensuring that the most meaningful and useful memories take root and flourish.”

-Me. Today. Just Now

[sciencymemes]

[bpod-bpod]

Sluggish Cells

Autism spectrum disorder (ASD) has a wide-range of severities and symptoms – including problems with social interactions, communication and learning – and a similarly wide range of genes are linked to the condition. But, researchers have observed one fairly common pathology: a lack of synaptic pruning in the brain – a normal process in child development in which certain brain cell connections are eliminated, and others strengthened. And now, studies of mice carrying ASD-linked mutations have suggested a possible cause. In the animals’ brains, microglial cells, which are responsible for pruning, grew to such enormous sizes (right) compared to normal (left) that they were too big and sluggish to do their job. Curiously, the oversized cells and resulting pruning problems were only seen in male mice. While these animals may provide hints as to why ASD is more common in boys, for now the reason female mice were unaffected remains a mystery.

Written by Ruth Williams

Image adapted from work by Zhi-Xiang Xu and colleagues

Department of Neuroscience, The Scripps Research Institute Florida, Jupiter, FL, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, April 2020

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[neuroscience-corner]

Neuroplasticity is the process by which our brains adapt to changes in the environment. One of the ways that our brains change is through the creation of neural networks. This happens because of long-term potentiation, or the repeated firing of neurons. This leads to an increase in dendritic branching which leads to an increase in the number of synapses. Synapses are brain structures that allow the neurons to transmit an electrical or chemical signal to another neuron. Another way that our brain can change is through synaptic pruning - which is a decrease in the number of synapses as a result of the removal of dendritic branches. Pruning can be the result of neuron cell death, hormones such as cortisol or the lack of use of a neural pathway. It is a natural process that occurs in the brain between early childhood and adulthood. Synaptic pruning is believed to be a viral process that increases efficiency of the brain as we get older and learn new complex information. 

The exact mechanism of neural pruning is not yet fully understood. But what can be seen is that during infancy, our brain creates an immense number of new synapses (synaptogenesis). This rapid period of synaptogenesis plays a vital role in learning, memory formation, and adaptation early in life. At 2-3 years old the number of synapses are at its peak. Shortly after that, unused synapses are being removed. Synapses weaken and strengthen depending on how often they are used. According to new research, synaptic pruning continues through adolescence to young adulthood. During young adulthood the pruning mostly occurs in the brain’s prefrontal cortex, which is the part of the brain heavily involved in the decision-making processes, personality development, and critical thinking. 

[neurosciencenews]

Excess Immune Pruning of Synapses in Neural Cells Derived From Patients with Schizophrenia

A new study finds evidence that the process of synaptic pruning, a normal part of brain development during adolescence, is excessive in individuals with schizophrenia.

The research is in Nature Neuroscience. (full access paywall)

[neurosciencenews]

Helping the Brain Prune Bad Habits

A drug that stimulates neuron pruning can nudge mice away from habit-driven behaviors when combined with retraining, neuroscientists have found.

The research is in Nature Communications. (full open access)