The speed at which our neurons communicate with each other changes as we age and may increase in some regions of the brain. A better understanding of how neuron transmission speeds vary throughout a person’s life may improve our knowledge of certain neurodevelopmental conditions, such as schizophrenia.
at the Mayo Clinic in Minnesota and her colleagues measured neuron transmission speeds in 75 people, aged 4 to 51, while they had surgery to monitor their epilepsy. For these operations, which were carried out between 2008 and 2020, the participants had electrodes implanted onto various parts of their brain to assess the strength of their neuron responses. The researchers used this as an opportunity to measure neuron speeds in different parts of the participants’ brains.
Results suggest that neuron speeds during transmission from the brain’s frontal to parietal regions rise from the age of 4 to 34, before steadily declining. The same is true for transmission from the frontal to temporal regions.
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In one 4-year-old participant, signals took about 45 milliseconds (ms) to travel from the frontal to parietal regions, but just 30ms to do so in a 38-year-old. Modelling suggests this would be between 21 and 27ms at 34 years old.
Yet the modelling also indicates that transmission from the temporal to parietal brain regions gets steadily faster with age. This could partly be due to the brain eliminating excess synapses – the spaces between nerve cells where nerve impulses are exchanged – from childhood to adulthood, says at King’s College London.
In early childhood, synapse numbers rapidly rise until around 7 to 8 years old, when they start to fall, says O’Muircheartaigh. You are left with the most important synapses, he says, but whether these are also the fastest is unclear.
Myelin sheath, which surrounds nerves so impulses can be transmitted quickly, may also become thicker and more efficient in the temporal and parietal regions with age, he says.
Why the same may not occur between the frontal and parietal regions and the frontal and temporal regions is unclear, says O’Muircheartaigh.
According to the researchers, these results may improve our understanding of conditions such as schizophrenia. The exact cause of this condition is unclear, but it has been linked to problems with neuron transmission at synapses.
But at Birkbeck, University of London, says the study’s results may not apply to people without epilepsy. Those with prolonged epilepsy may have brain changes that aren’t seen in people who recently developed the condition, she says. It is unclear when the participants first developed epilepsy.
O’Muircheartaigh agrees, but says we probably couldn’t implant electrodes onto the brains of people without epilepsy due to potential side effects.
bioRxiv
