Editing Frontal lobe (section)

== Structure ==
[[File:Frontal lobe animation.gif|200px|thumb|right|Frontal lobe (red) of left cerebral hemisphere]]
The frontal lobe is the largest lobe of the brain and makes up about a third of the surface area of each hemisphere.<ref name="Carpenter"/> On the [[Anatomical terms of location|lateral]] surface of each hemisphere, the [[central sulcus]] separates the frontal lobe from the parietal lobe. The [[lateral sulcus]] separates the frontal lobe from the [[temporal lobe]].

The frontal lobe can be divided into a lateral, polar, orbital (above the [[orbit (anatomy)|orbit]]; also called basal or [[Anatomical terms of location|ventral]]), and [[Anatomical terms of location|medial]] part. Each of these parts consists of a particular [[gyrus]]:
* Lateral part: lateral part of the [[superior frontal gyrus]], [[middle frontal gyrus]], and [[inferior frontal gyrus]]
* Polar part: [[frontopolar cortex]], transverse frontopolar gyri, frontomarginal gyrus.
* [[Orbitofrontal cortex|Orbital part]]: [[Orbital gyri|Lateral orbital gyrus]], [[orbital gyri|anterior orbital gyrus]], [[posterior orbital gyrus]], [[medial orbital gyrus]], and [[gyrus rectus]]
* Medial part: Medial part of the [[superior frontal gyrus]], [[cingulate gyrus]].

The gyri are separated by [[Sulcus (neuroanatomy)|sulci]]. E.g., the precentral gyrus is in front of the central sulcus, and behind the [[precentral sulcus]]. The superior and middle frontal gyri are divided by the [[superior frontal sulcus]]. The middle and inferior frontal gyri are divided by the [[inferior frontal sulcus]].

In humans the frontal lobe reaches full maturity only after the 20s—the prefrontal cortex, in particular, continues in maturing 'til the second and third decades of life<ref>{{Cite journal |last1=Kolk |first1=Sharon M. |last2=Rakic |first2=Pasko |date=January 2022 |title=Development of prefrontal cortex |journal=Neuropsychopharmacology |language=en |volume=47 |issue=1 |pages=41–57 |doi=10.1038/s41386-021-01137-9 |issn=1740-634X |pmc=8511863 |pmid=34645980}}</ref>—which, thereafter, marks the cognitive maturity associated with adulthood. A small amount of [[atrophy]], however, is normal in the aging person's frontal lobe. Fjell, in 2009, studied atrophy of the brain in people aged 60–91 years. The 142 healthy participants were scanned using [[magnetic resonance imaging|MRI]]. Their results were compared to those of 122 participants with [[Alzheimer's disease]]. A [[clinical trial|follow-up]] one year later showed there to have been a marked volumetric decline in those with Alzheimer's and a much smaller decline (averaging 0.5%) in the healthy group.<ref>{{cite journal | vauthors = Fjell AM, Walhovd KB, Fennema-Notestine C, McEvoy LK, Hagler DJ, Holland D, Brewer JB, Dale AM | title = One-year brain atrophy evident in healthy aging | journal = The Journal of Neuroscience | volume = 29 | issue = 48 | pages = 15223–31 | date = December 2009 | pmid = 19955375 | pmc = 2827793 | doi = 10.1523/JNEUROSCI.3252-09.2009 }}</ref>  These findings corroborate those of Coffey, who in 1992 indicated that the frontal lobe decreases in volume approximately 0.5–1% per year.<ref>{{cite journal | vauthors = Coffey CE, Wilkinson WE, Parashos IA, Soady SA, Sullivan RJ, Patterson LJ, Figiel GS, Webb MC, Spritzer CE, Djang WT | title = Quantitative cerebral anatomy of the aging human brain: a cross-sectional study using magnetic resonance imaging | journal = Neurology | volume = 42 | issue = 3 Pt 1 | pages = 527–36 | date = March 1992 | pmid = 1549213 | doi = 10.1212/wnl.42.3.527 | s2cid = 20481757 }}</ref>