Autism and Smell

Greetings Earthlings! 🙂

As I mentioned in last weeks post on taste sensitivity, this week we’re going to discuss sensitivity to smell in autism.

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As with other senses we have discussed, autists can be either hyposensitive or hypersensitive to odours. One autist may enter a malodorous environment without noticing anything amiss, another autist may wretch, or worse!

As a child, my nose was particularly sensitive to my environment (although judging by how I could taste the beer my friends were drinking yesterday evening from the fumes alone, this may still be the case on occasion 😛 ). Bad smells were especially trying- the smell of salads, fish, cigarette smoke, incense, even something so simple as a bag of popcorn could easily turn my stomach.

But it wasn’t all bad- this sensitivity comes with a heightened appreciation for pleasant smells too 🙂

Baking, chocolate, nice perfumes, the outdoors, the smell of metal (don’t ask me why I love this one so much- must be something to do with my taste in music! 😛 😉 )- in fact, such smells are not only a sensory sensation, but can also be used to help calm an autist.

As easily as an unpleasant smell could unsettle me, the right smell could calm me back down again as a child.  I always kept a teddy or a blanket near at hand that I could smell to help soothe and calm me and to lull me off to sleep- I couldn’t sleep without one particular teddy until I was 16!

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^^^^My teddy was a lot more raggedy than this…😬

So why does smell affect autists so much?

Interestingly, some studies indicate that there are no differences in sensitivity to smell between autists and their neurotypical peers, however, much research points to the cortex of the brain. This region is heavily involved in smell processing, and yep, you guessed it- the autistic brain shows signs of dysfunction in this region. In fact, the pre-frontal cortex shows signs of overgrowth and excessive linkage in the neurons (just like an overloaded plug), so no wonder sensory perception is altered in autists! This region is also associated with the formation and retrieval of long term memories, which could also explain why smells are often tied to memory recall in autists (which I will explore in more detail at a later stage 🙂 ).

One study also shows that autists may not inhale smells in the same way to their neurotypical peers. Evidence suggests that autists inhale deeply and intensely for both pleasant and unpleasant smells, whereas neurotypicals will tentatively sniff in the presence of an offending odour, which could further explain differences in scent processing.

In addition to this, research suggests that alterations in smell can influence social behaviours. A recent study in fact suggest that autists cannot smell fear and that there is a reversal in their response to fear. In this study, a group of autists were calm when presented with a sample of sweat from a skydiver, whereas their neurotypical peers exhibited classic signs of fear. In contrast, their fear levels increased when presented with the sweat sample from a calm individual!

In other words, an autists social behaviour may be affected by an inability to interpret social cues carried in odours- the mind boggles!

So there we have it dear Earthlings- hope this post didn’t ‘stink’ too badly 😛 😉

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Enjoy the weekend everyone! 🙂

Aoife

Autism and Taste

Greetings Earthlings! 🙂

As we have discussed in previous posts (such as sensory issues, light sensitivity and sound sensitivity), people with autism are highly sensitive on a sensory level, so naturally, taste is no exception.

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Many autists have highly sensitive taste buds wherein we find a number of flavours and foods too strong and overpowering to tolerate. This sensitivity to tastes can make life very difficult when it comes to taking medicines, food selection (which we will discuss in greater detail at a later stage) and maintaining a somewhat neutral expression when put in awkward public tasting scenarios (perhaps one of my biggest personal challenges 😛 ).

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On the other hand, some autists can in fact be hyposensitive to taste, often preferring foods with stronger flavours

So what’s causing these alterations in tongue sensitivity?

The research into this aspect of autism is currently quite limited, however, some neurological studies indirectly suggest that there is evidence of taste dysfunction in autism.

Many studies have shown evidence of brainstem dysfunction in the neurodiverse brain such as hypoplasia, or under development of the facial nerve nucleus (a collection of neurons in the brainstem that innervate the face). This nerve network carries taste information from the tongue and relays it to the brain. Any dysfunction or damage to this pathway can affect a persons ability to detect tastes.

Furthermore, the ability to identify tastes and flavour perception is controlled by a complex nerve network involving several different brain regions such as the thalamus, insula/operculum, the orbitofrontal cortex (OFC) and our old friend the amygdala. Many of these regions have been implicated in autism, suggesting that dysfunctions in these regions may influence an autists taste buds.

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Recent evidence also suggests that autists may be more sensitive to bitter tastes due to genetic mutations in the TAS2R38 taste receptor. Alterations in the TAS2R38 gene can cause autists to perceive bitter tastes differently to their neurotypical peers which could explain why our taste buds are so sensitive (and why alcohol makes me gag 😛 )

Finally, an increased sensitivity to smell also feeds into these alterations in taste which I will examine next week 🙂

Until next time Earthlings! 🙂

Aoife

 

Autism 101-Sensory Processing

Greetings Earthlings! 🙂

So today I’m going to briefly introduce you to the issue of sensory processing for people on the spectrum. This is a very broad topic, but I’ll expand on the issues in more detail at a later stage 🙂

Many individuals on the autistic spectrum struggle to process every day sensory information. Sounds, textures, smells, lights, even colours (boys in particular struggle to process the colour yellow) can overload the nervous system and greatly upset us, effect our behavior or even trigger a meltdown.

But why?

In autism, our senses can be either hyper or hypo sensitive (sometimes even both) to stimuli at different times. Our senses are heightened- smells are stronger, sounds are louder. As a result of this, stimuli reverberate all the more intensely in our brains.

Think of the brain as a computer server at exam time where everyone is logging in at once. Too much information has been entered into the system, but the server can only cope with so much. The entire system becomes overwhelmed and the server crashes.

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Here’s just a quick video simulation of sensory overload.

Warning for those on the spectrumthis video contains flashing lights, bright colours and loud, sudden noises

For me personally, I have many (mild) issues with sensory processing. Smells, tastes and textures are a daily struggle. For example, I don’t think I’ll ever be able to eat a salad as the smell alone makes me want to throw up- I’m dreading what pregnancy may one day bring! 😛 😉

Loud or irritating  noises, (especially repetitive ones), too can be a challenge. Don’t get me started on the shock I get when a passing bus makes that giant hiss/woosh sound or a car honks the horn unexpectedly!! 😛

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Most days, you’re lucky and the offending stimulus passes quickly, but other times it can get the better of you. I recently had a near meltdown on holiday from a cocktail of excessive heat, hunger, exhaustion and social frustration.

Top Tip– Keep on top of your hunger/thirst. I’ve discovered this past year that an excess of either will make me act really loopy! 😛

When you’re hit by sensory overload, it feels as though your head is caught in a vice grip. Your mind is screaming, unable to focus on anything else but the source of discomfort.

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The worst part of it I find is coming across as a complete basket case when overloaded. You don’t get the most sympathetic of looks when you complain about a persistent noise- few can understand how it’s making your brain hurt.

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So what does science have to say about sensory processing?

Sensory integration involves three basic sensory systems:

  • The tactile system (touch)- comprises a series of nerves passing information from the skin to the brain
  • The vestibular system (sound)- comprises a series of structures in the inner ear involved in movement detection
  • The proprioceptive system-a series of receptors in the muscle (proprioreceptors) which feed information to the brain about the body’s position

These three systems share a close but complicated relationship which allow us to experience, process and respond to different stimuli. Dysfunction in this network can cause hyper/hypo sensitivity, in addition to problems with coordination, behavior and academic issues.

Evidence from brain imaging studies has also shown that autists experience stronger responses in the brain to sensory stimuli in areas that process sensory information and the amygdala- an area that is involved in attention, emotional reactions and threat response.

But why is this?

Several studies have found evidence of hyper-excitability and hyper-connectivity in the autistic brain.

Evidence shows that in many cases of autism, the neurons located in the sensory cortex of the brain are more sensitive and excitable than others. This is kind of like how a person can be more ticklish in some parts of the body than another- the nerves in the underarm are more excitable than those of the arm.

The autistic brain has also shown signs of hyper-connectivity, where regions of the brain are excessively connected- like an overloaded plug!

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This amplifies memory formation, sensory processing and causes an autist to be hyper-emotional, which can make the world painfully intense. Scientists have theorized that autists prefer safe, controlled and predictable environments as a coping mechanism to actively avoid this pain.

Finally, studies have indicated that sensory issues, in addition to a number of other autistic behaviors, may be linked to neurotransmitter (chemical messengers between body and brain) levels in the body. As previously discussed, some neurotransmitters are dysregulated in autism. Evidence suggests that in cases of autism, there are higher levels of excitatory neurotransmitters, and lower levels of inhibitory (i.e. calming) neurotransmitters. These high levels of excitatory neurotransmitters cause neurons to fire excessively, which can influence sensory perception and processing.

I’ll expand a little bit more on the individual sensory issues at a later stage 🙂

Enjoy your week everyone 🙂

Aoife

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