Planum temporale: characteristics and functions of this part of the brain.

A summary of the characteristics of the planum temporale, a part of the brain.

The brain is the most important organ at our disposal and, curiously, the most mysterious. To this day there are still many unknowns related to this gelatinous collection of neurons.

The planum temporale is one of the areas of the brain that still provides us with more unknowns than answers. than answers. We have two of them, and they are characterized by being very strikingly asymmetric 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.

What is the planum temporale?

The planum temporale (plural plana temporalis), also called the temporal plane of the brain, is a cortical area located close to the auditory cortex (Heschl's gyrus) in the a cortical area located 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 marked interhemispheric asymmetry, being up to ten times larger in the left temporal gyrus than in the right temporal gyrus.It is up to ten times larger in the left hemisphere than in the right hemisphere. It must be said that this statement has been debated in recent years, since, as it has not been precisely delimited where this region begins and ends, it is not known to what extent it is possible to compare the right and left planum temporale.

Its characteristic asymmetry

As mentioned, the most striking feature 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 a more developed right planum temporale.while only 11% have a more developed right planum temporale. As it has not been precisely defined where this region begins and ends, in many cases it is not possible to establish which of the two plana temporalis is more developed, or they are directly symmetrical.

The interhemispheric asymmetry of this region is very large, with cases in which the left planum temporale is between five and ten times larger than the right one. 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 most asymmetrical in the whole brain. These differences are not only human, as they have also been found in large primates.

It seems that this asymmetry this asymmetry already begins to develop in utero.. Differences between the plana temporalis can be found in the human fetus as early as the 31st week of gestation. This has given strength to the hypothesis that there is a genetic predisposition to this brain asymmetry, although environmental explanations, such as the influence of certain maternal hormones, have also been considered.

Function

The planum temporale presents interhemispheric asymmetry as we have mentioned, besides being a markedly lateralized structure. It is involved with the capacity for language, an ability traditionally associated with the left hemisphere, the same hemisphere in which the planum temporale is located.The planum temporale is more developed in the left hemisphere, the same one in which the planum temporale is more developed in most people.

It has also been shown to be involved in musical ability and echolocation. In people with absolute hearing, i.e., who are able to identify a musical note without the need to listen to a note as a reference, the asymmetry between the plana temporalis is more pronounced than in most people. In these people something quite striking happens, since it is not that there is more development in the left planum, but that the right one is less developed than normal.

Attempts have been made to find out to what extent the asymmetry between the plana temporalis may be related to manual laterality, i.e., being right-handed, right-handed, right-handed, right-handed, right-handed or right-handed.that is, being right-handed, left-handed or ambidextrous. It is not common to find people with a more developed right planum and, apparently, the asymmetry would not be the reverse in the case of left-handed people, but something less. That is, in this population there would be less asymmetry, but the left planum temporale would still be more developed.

Sex differences

There are sex differences in the planum temporale. In males, the left planum temporale has a larger surface area, whereas no major sex differences have been seen in the right planum temporale.

It seems that these sex differences already begin to occur in the earliest stages of development, starting in the prenatal stages. These differences would be associated with environmental factors in utero, especially testosterone levels..

Controversy over asymmetry

Although the scientific community agrees that there is some asymmetry between the left and right planum temporale, there is also controversy as to whether this could actually be significant. As we have mentioned, this region has not yet been precisely delimited, which means that, sometimes it is not possible to compare with certainty between the two plana temporalis and the right plana temporalis..

It could be the case that the left planum temporale is smaller than is believed, and that in the comparison with the right one, close regions have actually been inadvertently incorporated.

Another criticism that has been made regarding this asymmetry is the use of somewhat antiquated 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 more slight, even negligible. In any case, this debate is still open.

Developmental problems

Research has tried to see if less interhemispheric asymmetry of the planum temporale is related to psychological disorders, especially developmental ones, and this seems to be the case.

Unlike what is preferred elsewhere in the body, it is normal and healthy in the brain for its two plana temporalis to be asymmetrical. There is symmetry in people with dyslexiaThis symmetry has been related to a low specialization of the left hemisphere in language skills, 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 stutter.although it must be said that there are those who present the same asymmetry as people with no language problems at all. One of the hypotheses to explain the language problems when there is interhemispheric symmetry in this region is that, since the left hemisphere, where Wernicke's and Broca's areas are located, has less strength, its linguistic capacity is interfered by the functioning of the right hemisphere, resulting in disorders in this function.

Symmetry has also been found in the planum temporale of people with schizophrenia.. Less lateralization in the brains of these patients seems to correlate with the presence of positive symptomatology, such as hallucinations.

Bibliographical references:

• Kolb B, Whishaw IQ (2003). Fundamentals of human neuropsychology (5th ed.). [New York]: Worth. p. 495. ISBN 0-7167-5300-6.
• Jill B. Becker (2002). Behavioral Endocrinology 2e. MIT Press. pp. 103-. ISBN 978-0-262-52321-9. Retrieved 4 January 2013.
• Carroll, S. B. (2003). "Genetics and the Making of Homo sapiens". Nature. 422 (6934): 849-857. doi:10.1038/nature01495. PMID 12712196