Jan 28, 2024 19:00:00

The cause of the sensory characteristics of autism may be ``excessive variation in neural activity''

Approximately 90% of patients with

autism , which causes social impairment and difficulty communicating with others, have sensory disorders such as heightened sensitivity to sounds and an aversion to certain odors. It is said that there is a problem with this. A research team led by Andreas Frick , a principal researcher at France's National Institute of Health and Medicine (INSERM), said that these problems may be caused by fluctuations in noise in the electrical activity of nerve cells in the brain. showed gender.

Endogenous noise of neocortical neurons correlates with atypical sensory response variability in the Fmr1−/y mouse model of autism | Nature Communications
https://www.nature.com/articles/s41467-023-43777-z

Noisy brain may underlie some of autism's sensory features | The Transmitter: Neuroscience News and Perspectives
https://www.thetransmitter.org/spectrum/noisy-brain-may-underlie-some-of-autisms-sensory-features/

Approximately 90% of people with autism report sensory problems, such as increased sensitivity to sounds or an aversion to certain odors. Also, in order to experience these sensations, many autistic patients tend to make loud noises or rock back and forth.

On the other hand, the causes of these problems have not been clarified, and up until now, two opposing views have been mainstream: ``nervous hypersensitivity'' and ``decreased sensitivity.'' However, Frick reports, ``It is becoming clear that the factors contributing to these problems are more complex.''

Previous research on autistic patients and healthy people

has shown that there are significant differences in brain waves when watching videos. Furthermore, studies using fMRI have reported that results vary even among patients with autism. This suggests that sensory problems in people with autism may result from inconsistent brain responses.

Frick and his team conducted a study using mice that lacked

FMR1 , a gene that causes Fragile X syndrome-related disease , which is thought to be a factor in the onset of autism. The research team repeatedly applied electrical stimulation to the legs of healthy mice and mice lacking FMR1 using the patch clamp method . At that time, the research team also monitored the activity of neurons in the somatosensory area, which is the brain area where mice process the sense of touch.

The researchers found that healthy mice responded similarly whenever electrical stimulation was applied to their feet. On the other hand, it has been reported that when electrical stimulation was applied to mice lacking FMR1, there were large variations in the magnitude of the electrical stimulation and the response time.

Next, the research team measured how the electrical activity of the mouse's nerve cell membranes changed. As a result of the investigation, the research team reported that the changes in electrical activity in mice lacking FMR1 were twice as large as those in healthy mice. It has also been found that the more the neuronal noise fluctuates, the greater the variation in brain cell responses to touch. Mr. Frick says, ``This 'noise fluctuation in response to stimulus' may be linked to nervous irritability in autistic patients.''

In addition, the research team has reported that the brain waves of FMR1-deficient mice are significantly different from those of healthy mice, and that there is a correlation with fluctuations in neuronal responses. These results suggest that disturbances in brain waves contribute to the 'sensory deficits'

thought to be associated with autism.

According to the research team, the ``variability in sensory processing'' found in mouse experiments may be causing the sensory problems seen in autism patients. Flick says, ``Imagine talking to a friend at a party where music is playing.Even while the music is playing, you need to match the sound of the other person's voice to the movement of their lips, but this is due to variations in sensory processing. 'When this happens, these behaviors become difficult and, as a result, it becomes difficult for people with autism to socialize.'