The complexity of signals in the brain seems to decrease as the nervous system develops in fetuses and babies 鈥� and does so significantly faster in males compared with females.
at the University of T眉bingen in Germany and his colleagues used an imaging technique called magnetoencephalography (MEG) to measure the magnetic fields produced by the brain鈥檚 electrical currents聽in 43 third-trimester fetuses and 20 babies, aged between 13 and 59 days old, to sound stimuli. Of the babies, 16 had also been recorded as fetuses.
The stimuli consisted of various arrangements of beeps. One sequence was made up of four beeps, each lasting 200 milliseconds and separated by 400-millisecond intervals. A 鈥渂lock鈥� of stimuli was defined as 180 sequences, played one after the other with a 1.7-second interval between them. This was played to the fetuses via a 鈥渟ound balloon鈥� squeezed between the pregnant person鈥檚 abdomen and the MEG sensors.
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First, each fetus and baby heard 30 of these blocks, as a sort of training. The researchers then recorded their magnetic brain activity upon hearing two blocks.
The team calculated several different measures that reflect the complexity of the MEG signal, using algorithms that determine, for example, how difficult it is to process.
In adults with no known health conditions, in various executive functions, such as planning and decision-making. Low levels are associated with states in which the capacity for information-processing is reduced, such as and .
Frohlich and his colleagues therefore hypothesised that MEG signal complexity would rise among the fetuses as gestation progressed and among the babies as they aged. But they were surprised to find that this actually fell with time, with the decrease occurring significantly faster among the male fetuses and babies than the female ones.
The reason for this decrease is unclear, but one possible explanation is that neural complexity measures different processes as the brain develops.
鈥淭he developing brain eliminates cells and connections that are unnecessary, constraining the number of ways in which the brain can respond to a stimulus,鈥� says Frohlich. 鈥淎s the brain matures, it moves toward ordered patterns of neural connections, which tell it how to respond to stimuli, such as the beeps in our experiment. A more developed brain has fewer ways of responding to that stimulus, and thus lower complexity. If we were to look at spontaneous activity, we might see something different.鈥�
Frohlich suspects the variation between the sexes might be due to 鈥渦nderlying differences in how the nervous system develops in boys and girls鈥�. The researchers didn鈥檛 follow the babies beyond the end of the study and it is therefore unclear whether this variation persists.
A study in 2018 suggested that the complexity of signals obtained from infants using the imaging technique electroencephalography .
鈥淎utism is diagnosed four times more often in boys,鈥� says Frohlich. If it were possible to identify a developmental variable that could detect autism at birth or even earlier, that could allow for potential interventions to start earlier for those infants, which might help with symptoms, he says.
快猫短视频s could measure neural complexity in fetuses who have an older sibling with autism and are therefore more likely to have the condition themselves, says Frohlich. 鈥淲e could follow these children up to their third birthday and see if neural complexity measured in the womb is useful for predicting which children go on to develop autism.鈥�
Speaking of predicting the condition, at the National Autistic Society charity in the UK, says: 鈥淎utism can only be identified accurately from a thorough clinical assessment by an experienced team of qualified professionals. Autistic people should receive the support that meets their specific needs and any 鈥榠nterventions鈥� for autistic people should centre the individual and not make any attempt to reduce autistic characteristics.鈥�
Nature Mental Health
