Do the foldings in the brain vary person to person?

Question

Can the gyri and sulcus, which are the foldings of the cerebrum, vary from person to person? If that is true, then can we say different people have different types of thinking skills? I believed that the anatomy of the brains of homo sapiens were all the same (except mentally abnormal children with Progeria like syndrome) but then, why do we all have different thinking skills, as I have observed in my surroundings? I know some depends on self created skills, but could different brain foldings be the reason?

Answer 1

The major structure is consistent but there is a lot of variation in the details, including the presence and absence of certain gyri:

• Kennedy, D. N., Lange, N., Makris, N., Bates, J., Meyer, J., & Caviness Jr, V. S. (1998). Gyri of the human neocortex: an MRI-based analysis of volume and variance. Cerebral Cortex (New York, NY: 1991), 8(4), 372-384.

• Kruggel, F. (2018). The macro-structural variability of the human neocortex. NeuroImage, 172, 620-630.

• Bartley, A. J., Jones, D. W., & Weinberger, D. R. (1997). Genetic variability of human brain size and cortical gyral patterns. Brain: a journal of neurology, 120(2), 257-269.

However, it's not so straightforward to connect these to function and thinking skills; the layout of the gyri is more like a shape of a blank canvas that cortical function is then written on. For example, the location of prefrontal regions relative to gyri/sulci varies between individuals:

• Rajkowska, G., & Goldman-Rakic, P. S. (1995). Cytoarchitectonic definition of prefrontal areas in the normal human cortex: II. Variability in locations of areas 9 and 46 and relationship to the Talairach Coordinate System. Cerebral cortex, 5(4), 323-337.

As does the primary auditory cortex:

• Leonard, C. M., Puranik, C., Kuldau, J. M., & Lombardino, L. J. (1998). Normal variation in the frequency and location of human auditory cortex landmarks. Heschl's gyrus: where is it?. Cerebral cortex (New York, NY: 1991), 8(5), 397-406.

And I'd wager most other areas, too. So you can't map the size/presence of a given macrostructural feature to a specific function. You might instead look at cortical thickness in particular functional regions, or area associated with a particular function, rather than the "phrenology" of the folds.

Answer 2

Tl;DR: The folding pattern seems consistent among human species but they are not exact match when compared person to person.

Long Answer:

The folding is not random like a crumpled piece of paper. Rather it exhibits a pattern that is consistent from person to person. Research indicates that a network of nerve fibers physically pulls the pliable cortex into shape during development in utero and holds it in place throughout life. Disturbances to this network during development or later due to stroke or injury, can have consequences for brain shape and neural communication and may lead to mental disorders.

Over the past couple of years, several research teams have reported that the brains of schizophrenic patients exhibit reduced cortical folding overall relative to the brains of normal people so they are quite certain that brain shape differs between schizophrenics and healthy people. Similarly, people diagnosed with autism also exhibit abnormal cortical convolutions. Some of their sulci appear to be deeper and slightly out of place as compared with those of healthy subjects. Researchers pointed out that it arises from the miswiring of the brain.

Mental disorders and learning disabilities can also be associated with aberrations in the composition of the cortical layers. For instance, in the late 1970s neurologist Albert Galaburda of Harvard Medical School found that in dyslexia, the pyramidal neurons that form the chief communication system of the cerebral cortex are shifted from their normal position in the layers of the language and auditory areas of the frontal cortex.

The above information is paraphrased from this article but you can read the whole to get a better understanding of the topic.

Also, you can refer to below papers:

1. Toro R, Perron M, Pike B, Richer L, Veillette S, Pausova Z, Paus T. Brain size and folding of the human cerebral cortex. Cereb Cortex. 2008 Oct;18(10):2352-7. doi: 10.1093/cercor/bhm261
2. Garcia K. E., Kroenke C. D. and Bayly P. V. 2018, Mechanics of cortical folding: stress, growth and stability, Phil. Trans. R. Soc. B3732017032120170321, DOI: 10.1098/rstb.2017.0321
3. H. de Vareilles, D. Rivière, JF Mangin, J. Dubois, Development of cortical folds in the human brain: An attempt to review biological hypotheses, early neuroimaging investigations and functional correlates, Developmental Cognitive Neuroscience, Volume 61, 2023, DOI: 10.1016/j.dcn.2023.101249