Autism and ADHD as opposites based on fly models?

Drosophila melanogaster egg. Source: my person...
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Regular readers of this blog will know my fascination with autism and psychosis as opponents on a continuum theory . I have already been privately speculating that ADHD in childhood may be a risk factor for Psychosis in later adolescence, especially as both are supposed to have underling dopamine abnormalities, so this new study by Brembs et al caught my attention.

Recently I came cross this paper by Bjorn Brembs et al that investigated attention-like processes in mutant fly models that showed memory deficits. They weer aqble to show that despite overt similar olfactory memory deficits, the attention-like processes worked in opposite ways in the two mutant models. In the rutabaga/dunce model, the atention ws hyperfocussed , resembling human autism; while in radish models , attention was flexible and distract-able resembling human ADHD.

It is increasingly apparent that many classical Drosophila learning and memory mutants are also defective in short-term processes relevant to selective attention. Previous studies have shown that short-term memory as well as long-term memory mutants display attention-like defects (van Swinderen, 2007; van Swinderen et al., 2009), and the current study reveals radish mutants to be defective as well, albeit with distinctly different symptoms. The Drosophila mutants dunce1, rutabaga2080, and radish1 share olfactory memory defects but differ conspicuously for short-term processes relevant to visual attention. Whereas the more persistent optomotor behavior of dunce1 and rutabaga2080, both affecting the cAMP-associated pathways (Davis et al., 1995), are reminiscent of the persistent preoccupation of some patients afflicted with autism, the phenotype of radish mutant flies described here is similar to some of the symptoms of patients with ADHD.

They further speculate as o why these two phenotypes may be present and relate it to exploit/explore conundrum.

Attaining the right balance between persistence and flexibility is a crucial feature of adaptive behavior, because it reflects the balance between exploration and exploitation of natural resources. It is tempting to speculate that radish and dunce/rutabaga may constitute the two respective extremes of this balance. Recent work investigating torque behavior of wild-type flies (similar to our shorter experiments here) has shown that, during extended flights, the occurrence of turning maneuvers can be described by a Le´vi distribution (Maye et al., 2007). Such distributions of behavioral output, seen in foraging behavior in many animals, are characteristically long-tailed. This means that animals may occasionally persist with one behavioral choice for unusually long, but most often choices alternate at a more regular, normally distributed rate. The advantage of allowing for occasional long forays into one direction is presumably to chance on a new resource away from the proximal search space. Such behavior has been found to be ecologically advantageous, but mechanisms driving such alternation tendencies have not been documented in the Drosophila brain. One interpretation of our results is that the mushroom body circuits defined by dunce/ rutabaga/radish expression are involved in establishing the balance between persistence and flexibility [i.e., the explore/exploit dilemma (Daw et al., 2006)]. A separate set of results has independently also arrived at a similar conclusion, suggesting that the mushroom bodies could be involved in maintaining a period of behavioral flexibility (i.e., attention-like processes) before a longer-term transition to habit formation or motor learning
(Brembs, 2009).

To me, this research adds another intriguing possibility to the autism-psychosis dimension, that of ADHD as a childhood phenotype/risk factor for later psychosis.

van Swinderen, B., & Brembs, B. (2010). Attention-Like Deficit and Hyperactivity in a Drosophila Memory Mutant Journal of Neuroscience, 30 (3), 1003-1014 DOI: 10.1523/JNEUROSCI.4516-09.2010

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3 thoughts on “Autism and ADHD as opposites based on fly models?

  1. PanManiac

    Everyone Ive known who had Aspergers was also dxd ADHD but thats the overfocused type. I have the other type the distractible type and possibly chronic hypomania which is rare enough that its called Bipolar NOS(even though it doesnt involve a depressive state at all). Its a common dx where I live and its an unspoken but open secret that its because of the chemical plant upstream(my town’s just like the “valley” in Oblongs). Usually comes with cluttered speech(have that too and used to be self-conscious about how I talked but now I dont care). But also this is usually manageable without medication(other than the ordinary studying stimulants for comorbid ADHD).

    ADHD is caused by having a brain wired too differently from the norm, consequently from the way information is presented to focus, so there’s several different ADHDs. 1(overfocused) taken to an extreme is autism, 1 to an extreme is psychotic mania(distractible), another taken to an extreme is schizophrenia(ring of fire). Another the sluggish cognitive tempo I don’t know, but that’s also based on a different brain type. It sounds like it would make you dumber but I know a guy who definitely has that one and he does everything so slow but he’s also very smart.

    Studies show schizophrenia is not solely caused by dopamine. Dopamine is a factor. NMDA receptors have been implicated. Rather than too little or too much one big risk factor is when these receptors work irregularly.

    Think about the way dopamine works, how you feel when you get a dopamine rush, the greater ability to focus and to switch focus.

    Could it be that dopamine is the chemical that stimulates the rate that the brain switches connections on and off? This would allow the brain to rapidly switch from a mode where it is zoned in on something to one where it is switching between different things. This “switching” could be involved in altering levels of other brain chemicals such as NMDA and serotonin both of which have been implicated in schizophrenia, bipolar, and autism. That would cause these chemicals to work irregularly.

    Its been speculated that babies hallucinate at first because they haven’t fully integrated the real world in with their senses. If the brain’s perception of the world was widely changing all the time (high dopamine) the person wouldn’t be able to accurately integrate their experiences.

    Ancient societies did not have mental disorders. The narrowing of acceptable human experience created mental disorders.

    If anything a person with ADHD when its not “ring of fire”(switching rapidly between overfocused and distractible) is at less of a risk for schizophrenia if unmedicated. One problem, the medication used for ADHD usually stimulates dopamine. Thats not to say it shouldn’t be used but science should investigate if these drugs are increasing the risk of psychosis later in life and doctors should introduce them slowly. Also the use of these drugs should be limited to as needed for studying or work. As someone with ADHD I rarely use them for other purposes.

    Any of these ADHDs can be linkened to a “normal”(loosely used) state of mind under the influence of a drug. Ring of fire is like being on stimulants but not having control of it and at an extreme is like when someone takes enough of a stimulant to reach psychosis(this has been known to happen even if someone takes too much caffeine). Mine, distractible is like being on acid or ecstasy(although ecstasy tends to lower irritability if it turned into a common experience this would alter it). Think about how psychedelics make new concepts and ideas just rush, while you feel so light on your feet. The point where it becomes hard to distinguish reality and hallucination is just like manic psychosis or even overlap with some forms of schizophrenia(its a varied disorder, there may be many schizophrenias). NMDA antagonists, with its bodily distortions and being able to get “sucked into” a movie or even hallucinate that you are an object would result from an intense focus on it that an autistic person whose somewhat used to it wouldn’t process as a hallucination, at a very profound level this could overlap with catatonic schizophrenia. And the sluggish cognitive tempo is like being on cannabis. Anandamide, the body’s natural cannabis has been positively linked to cellular regeneration including the brain itself. Its the homeostasis system. This would result in slower thinking because it would be necessary for any part of the body to slow down while cells are regenerated, but at the same time this would cause the way they form and wire to be based on the person’s “thoughts” at the time(this is why cannabis responds the most to the user’s mindset) and consequently the person would not lose IQ because increased accuracy and ability to direct the mind makes up for a slower thought process.

    Sorry if this is a little choppy. My mind comes up with new ideas that fit in but fit in random places and then new ideas that fit the same place. With I could make flow chart here, I think like a flow chart.

    1. sandygautam Post author

      Hi PanManiac,
      your classification of ADHd into distractible, overfocussed and ‘ring of fire’ is interesting, but I would like to know if this is based on anecdotal evidence or is there some research in line with this. I have to read in more detail the rest of your thoughts, but they do seem interesting and useful.

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