Why does brain have sulci

The reason our brains have that wrinkly, walnut shape may be that the rapid growth of the brain's outer brain — the gray matter — is constrained by the white matter, a new study shows. Researchers found that the particular pattern of the ridges and crevices of the brain's convoluted surface , which are called gyri and sulci, depends on two simple geometric parameters: the gray matter's growth rate and its thickness. The development of the brain's wrinkles can be mimicked in a lab using a double-layer gel, according to the study published today Aug.

The researchers noted that along with these physical constraints, genes also have a role in determining the brain's shape, because they regulate how neurons proliferate and migrate to their destinations. All mammalian species have similar layering in the brain's outer layer — the cortex — but only larger mammals have a cortex that is folded. For example, a rat brain has a smooth surface, whereas a considerably larger brain such as a human's, has tens of gyri and sulci. Measure content performance.

Develop and improve products. List of Partners vendors. Share Flipboard Email. Regina Bailey. Biology Expert. Regina Bailey is a board-certified registered nurse, science writer and educator. Updated October 09, Key Takeaways: Brain Gyri and Sulci Gyri and sulci are the folds and indentations in the brain that give it its wrinkled appearance.

Gyri singular: gyrus are the folds or bumps in the brain and sulci singular: sulcus are the indentations or grooves. Folding of the cerebral cortex creates gyri and sulci which separate brain regions and increase the brain's surface area and cognitive ability. Gyri and sulci form boundaries within and between the lobes of the brain and divide it into two hemispheres.

We can only imagine what life was like for this person. Photographer Adam Voorhes spent a year trying to track down more information about this and nearly other human brains held in a collection at the University of Texas, Austin, to no avail. Furthermore, we sought to determine whether age-related differences in sulcal characteristics were more strongly associated with differences in local or global cortical volumes. Sulci were Differences in sulcal width were generally higher in males than females.

Differences in the width of the superior frontal and central sulci were significantly associated with differences in the volume of adjacent local gyri, while age-related differences in the width of lateral and superior temporal sulci were associated with differences in whole brain cortical volume.

These findings suggest that sulcal characteristics provide unique information about changes in local and global brain structure in aging. Biological aging is associated with brain atrophy at both the micro and macroscopic scales Esiri, At the microscopic level, neuronal death, shrinkage of dendritic trees and neuropil, as well as decrease in spine numbers are involved Murphy et al. At the macroscopic level, neuroimaging studies show that volumetric decreases occur across the whole brain with some regions more affected than others DeCarli et al.

Volumetric studies have been very effective in using magnetic resonance imaging MRI data to characterize localized patterns of cerebral atrophy across the lifespan. However, they also have some important limitations. Specifically, as MRI intensity contrast between gray matter GM and white matter WM decreases with age, estimates of cerebral atrophy tend to underestimate the actual rate of shrinkage Kochunov et al.

Moreover, volumetric measures are not very sensitive to complicated brain surface folding and thus may introduce regional bias and decrease statistical power Lemaitre et al.

Alternative measurements—which do not suffer from these limitations—could be useful to complement existing volumetric measures.

Recently, the measure of sulcal morphology has become a more accessible approach to investigate neuroanatomical variability Mangin et al. Since sulcal measures are not dependent on the accurate identification of GM and WM borders, and are more sensitive to complex folding of the cerebral surface, they may be more sensitive to detecting age-related change in cerebral structure Lamont et al.

With aging, sulci become wider and shallower Rettmann et al. These global forces are driven by the combined changes in cortical GM and WM, as well as in other subcortical structures Im et al. However, a number of questions remain unanswered. First, little is known about the magnitude and localization of sulcal changes in middle-age MA. Second, it is unclear whether sulcal changes are driven by atrophy of adjacent local structures or by change in global tissue volumes.

Third, it is not clear whether sulcal width or depth is more strongly associated with brain structural differences. The aim of this study is to address these questions by: 1 investigating how sulcal morphology differs between middle adulthood and old-age OA ; 2 determining whether the volume of local brain structures or the whole brain are more strongly associated with sulcal characteristics; and 3 investigating whether sulcal width or depth is more strongly associated with local brain volumetric differences.

It was predicted that: a sulci in MA would be narrower and deeper than in OA; b local structural characteristics would be more strongly associated with sulcal morphology in most sulci than global volumetric measures; and c sulcal width would be more strongly associated with local brain volumetric differences than sulcal depth. PATH participants were residents of the Australian Capital Territory and neighboring Queanbeyan, Australia, and were randomly recruited through the electoral roll Anstey et al.

Enrolment to vote is compulsory for Australian citizens, making this cohort representative of the population. The protocol was approved by the Australian National University Ethics Committee and all participants provided written informed consent. The selection process is summarized in Figure 1. The final sample includes MA participants and OA participants. All participants were imaged with a 1.

FreeSurfer software enables the automatic parcellation of the volumes of the cortical surface using T1-weighted images Dale et al. A model of cortical sulci was automatically produced for each participant with the standard pipeline. Based on these steps, BrainVISA generates an integrated map combining all measurable sulci with labels extracted from a brain atlas i. Average sulcal width is defined as the average span of the intra-sulcal space along the normal projections to the sulcal mesh, i.

Average sulcal depth refers to the mean distance from the cortical surface of adjoining gyri to the deepest point in the sulcus. Five sulci in each hemisphere were chosen for analysis including Figure 2 : A superior frontal sulcus, B central sulcus, C lateral sulcus, D superior temporal sulcus, and E intra-parietal sulcus. These were chosen because they are present in all individuals; they are large and relatively easy to identify with precision Liu et al. Figure 2.

The five sulci and adjoining gyri selected for investigation. Central sulcus: pre-central B1 , post-central B2. Lateral sulcus: superior temporal C. Superior temporal sulcus: superior temporal D1 , middle temporal D2. Intra-parietal sulcus: superior parietal E1 , inferior parietal E2. GM and WM volumetric estimates were produced for 34 regions in each hemisphere Liu et al. The regions adjacent to the five selected sulci were chosen as local factors LF to index local impact on sulcal changes.

They included: pre-central, post-central, superior frontal, middle frontal, superior temporal, middle temporal, superior parietal and inferior parietal Figure 2. Total cortical GM was chosen rather than whole brain GM, because the latter includes subcortical and cerebellar GM which are thought to have less impact on sulcal morphology Liu et al. For this purpose, two variables were computed, one reflecting whether participants were in the MA or OA group, and another reflecting age variance within group AgeC.

For AgeC, the age of each participant was centered on the mean of their group by subtracting the rounded minimum age of their age group 45 and 65 from their age. Demographics are shown in Table 1. The mean sulcal width of sulci investigated was 1. The left superior frontal sulcus showed the largest sulcal difference 0. In general, an anterior to posterior topographical gradient in sulcal width was observed such that sulcal widths became narrower from the frontal lobe to the occipital lobe in both age groups.

No significant association between sulcal width and age AgeC was detected within the 4-year age bands of the two age groups. Figure 3. The median, 1st and 3rd quartile range of sulcal widths and depths in MA and OA are shown. Whiskers show minimum and maximum value. Superior frontal sulcus frontal ; central sulcus central , lateral sulcus lateral ; superior temporal sulcus temporal ; intra-parietal sulcus parietal.

The mean depth of sulci investigated was The right intra-parietal sulcus showed a larger sulcal difference 0.