Planum Temporale: Characteristics And Functions Of This Part Of The Brain
The brain is the most important organ we have and, curiously, the most mysterious. To this day there are still many unknowns related to this gelatinous set of neurons.
The planum temporale is one of the areas of the brain that still offers us the most unknowns what answers. We have two of them, and they are characterized by being very strikingly asymmetrical with respect to each other.
Let’s find out where this brain region is located, how its interhemispheric asymmetry occurs, what its functions are, the controversy behind it and the problems related to it.
The planum temporale (plural plana temporalis), also called the temporal plane of the brain, is a cortical area that is close to the auditory cortex (Heschl’s gyrus), in the Sylvian fissure It is triangular in shape and is located in the center of Wernicke’s area in the left hemisphere, one of the most important areas for language processing. It is located on the superior surface of the superior temporal gyrus, touching the parietal lobe.
The planum temporale is a region well known for its pronounced interhemispheric asymmetry , being up to ten times larger in the left hemisphere than in the right. It should be said that this statement has been debated in recent years, since, as it has not been precisely delimited where this region begins and where it ends, it is not known to what extent it is possible to compare the right temporal planum with the left.
Its characteristic asymmetry
As we mentioned, the most striking characteristic of the planum temporale is its significant interhemispheric asymmetry. About 65% of people have a more developed and larger left planum temporale , while only 11% have the most developed right planum temporale. As it has not been precisely defined where this region begins and where it ends, in many cases it is not possible to establish which of the two plana temporalis is the most developed, or directly presents symmetry.
The interhemispheric asymmetry of this region is very great, there are cases in which the left planum temporale is between five and ten times larger than the right. It is for this reason that this structure is among the most asymmetrical in the brain and, it has even been suggested that it is actually the one with the most asymmetry in the entire brain. These differences are not only human, since they have also been found in large primates.
It seems that this asymmetry already begins to develop in the womb Differences between the plana temporalis can be found in the human fetus from the 31st week of gestation. This has given strength to the hypothesis that there would be a genetic predisposition to this cerebral asymmetry, although environmental explanations have also been considered, such as the influence of certain maternal hormones.
Function
The planum temporale presents interhemispheric asymmetry as we have mentioned, in addition to being a markedly lateralized structure. It is involved with language ability, a skill traditionally associated with the left hemisphere the same one in which the planum temporale is most developed in most people.
It has also been seen that it could be involved in musical ability and echolocation. In people with absolute hearing, that is, they are able to identify a musical note without having to listen to a note as a reference, the asymmetry between the plana temporalis is more pronounced than in most people. Something quite striking happens in these people, since it is not that there is more development in the left planum, but rather that the right one is less developed than normal.
An attempt has been made to find out to what extent the asymmetry between the plana temporalis can be related to manual laterality , that is, being right-handed, left-handed or ambidextrous. It is not common to find people who have a more developed right planum and, apparently, it would not be that the asymmetry was reversed in the case of left-handed people, but rather something minor. That is, in this population there would be less asymmetry, but the left planum temporale would continue to be more developed.
Differences between sexes
There are sex differences in the planum temporale. In men, the left planum temporale has a larger surface area, while no major differences have been seen between sexes in the right planum temporale.
It seems that these sexual differences already begin to occur in the earliest phases of development, beginning in the prenatal stages. These differences would be associated with environmental factors in the uterus, especially testosterone levels
Asymmetry controversy
Although the scientific community agrees that there is a certain asymmetry between the left and right planum temporale, there is also controversy about whether this could really be something significant. As we have mentioned, this region has not yet been precisely delimited, which means that, Sometimes, it is not possible to safely compare between the two plana temporalis
It could happen that the left planum temporale is smaller than is believed, and that in the comparison with the right, nearby regions have actually been incorporated, unintentionally.
Another criticism that has been made regarding this asymmetry is the use of somewhat outdated neuroimaging techniques It is believed that they could have exaggerated the differences between the plana temporalis, since in more modern and precise neuroimaging techniques the interhemispheric differences in this region are milder, even negligible. In any case, this debate remains open.
Research has tried to see if a lower interhemispheric asymmetry of the planum temporale is related to psychological disorders, especially development, and it seems to be the case.
Unlike what is preferred in any other part of the body, what is normal and healthy in the brain is for its two plana temporalis to be asymmetrical. There is symmetry in people with dyslexia which has been related to a low specialization of the left hemisphere in language ability, especially in reading and writing.
This symmetry has also been found in people who stutter , although it must be said that there are those who present the same asymmetry as people without any language problem. One of the hypotheses to explain language problems due to interhemispheric symmetry in this region is that, since the left hemisphere, where Wernicke’s and Broca’s areas are located, is less strong, its linguistic capacity is interfered with by the functioning of the left hemisphere. right hemisphere, giving rise to disorders in this function.
Symmetry has also been found in the planum temporale of people with schizophrenia Less lateralization in the brain of these patients seems to correlate with the presence of positive symptoms, such as hallucinations.
