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frontal_lobe

Frontal lobe

brainmadesimple.com_uploads_7_8_8_5_7885523_1124705.jpg The frontal lobe is located at the front of each cerebral hemisphere and positioned anterior to (in front of) the parietal lobe and superior and anterior to the temporal lobes.

It is separated from the parietal lobe by the central sulcus, and from the temporal lobe by the Sylvian fissure.

The precentral gyrus, forming the posterior border of the frontal lobe, contains the primary motor cortex.

The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system is associated with reward, attention, short-term memory tasks, planning, and motivation. Dopamine tends to limit and select sensory information arriving from the thalamus to the fore-brain. A report from the National Institute of Mental Health says a gene variant that reduces dopamine activity in the prefrontal cortex is related to poorer performance and inefficient functioning of that brain region during working memory tasks, and to slightly increased risk for schizophrenia.

see Left frontal lobe

Classification

Traditional classification systems divide the frontal lobes into the precentral gyrus

Prefrontal cortex (extending from the frontal poles to the precentral cortex and including the frontal operculum, dorsolateral, and superior mesial regions), orbitofrontal cortex (including the orbitobasal or ventromedial and the inferior mesial regions), and superior mesial regions (containing, primarily, the anterior cingulate gyrus). Each of these areas has widespread connectivity.


The frontal lobe bottom can also be divided into a lateral, polar, orbital (above the orbit; also called basal or ventral), and medial part. Each of these parts consists of particular gyri:

Lateral part: Precentral gyrus, lateral part of the superior frontal gyrus, middle frontal gyrus, inferior frontal gyrus.

Polar part: Transverse frontopolar gyri, frontomarginal gyrus.

Orbital part: Lateral orbital gyrus, anterior orbital gyrus, posterior orbital gyrus, medial orbital gyrus, gyrus rectus.

Medial part: Medial part of the superior frontal gyrus, cingulate gyrus.

The gyri are separated by 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 around the late 20s, marking 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 MRI (magnetic resonance imaging). Their results were compared to those of 122 participants with Alzheimer’s disease. The participants returned one year later, and the researchers noted that although volumetric decline was clearly evident in large amounts in the AD participants, it was also evident in small quantities in the healthy individuals. A decline in frontal lobe volume of approximately 0.5% over that year seemed to be average.

These findings corroborate those of Coffey, who in 1992 indicated that the frontal lobe decreases in volume approximately 0.5%-1% per year.

The frontal lobes of the brain are notoriously “silent”: Benign tumors such as meningiomas that compress the frontal lobes from the outside may not produce any symptoms other than progressive change of personality and intellect until they are large 1)

see Frontal lobectomy.

see Frontal lobe epilepsy

1)
Yakhmi S, Sidhu BS, Kaur J, Kaur A. Diagnosis of frontal meningioma presenting with psychiatric symptoms. Indian J Psychiatry. 2015 Jan-Mar;57(1):91-3. doi: 10.4103/0019-5545.148534. PubMed PMID: 25657465; PubMed Central PMCID: PMC4314926.
frontal_lobe.txt · Last modified: 2016/11/29 14:11 (external edit)