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Frontal cortex

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Brainlobes

Lobes of the human brain (Frontal Lobe is shown in red)

The frontal lobe is an area in the brain of vertebrates. Located at the front of each cerebral hemisphere, frontal lobes are positioned in front of (anterior to) the parietal lobes. The temporal lobes are located beneath and behind the frontal lobes.

Anatomy Edit

Gray729

Gray's Fig. 729 - Orbital surface of left frontal lobe.

In the human brain, the central sulcus separates the frontal lobe from the parietal lobe along the top of each cerebral cortex. The lateral sulcus separates the inferior frontal gyrus of lower frontal lobes from the temporal lobes.

The frontal lobe can be divided into a lateral, polar (frontalmost), orbital (above the orbit; also called basal), 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.

Function Edit

In the human brain, the precentral gyrus and the related cortical tissue that folds into the central sulcus comprise the primary motor cortex, which controls voluntary movements of specific body parts associated with areas of the gyrus.

Frontal lobes have been found to play a part in impulse control, judgment, language, memory, motor function, problem solving, sexual behavior, socialization and spontaneity. Frontal lobes assist in planning, coordinating, controlling and executing behavior. People that have damaged frontal lobes may experience problems with these aspects of cognitive function, being at times impulsive; impaired in their ability to plan and execute complex sequences of actions; perhaps persisting with one course of action or pattern of behavior when a change would be appropriate (perseveration).

Cognitive maturity associated with adulthood is marked by related maturation of cerebral fibers in the frontal lobes between late teenager years and early adult years. Research by Dr. Arthur Toga, UCLA, found increased myelin in the frontal lobe gray matter of young adults compared to that of teens, whereas gray matter in parietal and temporal lobes was more fully matured by teen years. Typical onset of schizophrenia in early adult years correlates with poorly myelinated and thus inefficient connections between cells in the forebrain.

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.

Dopamine-sensitive neurons in the cerebral cortex are found primarily in the frontal lobes. The dopamine system is associated with pleasure, long-term memory, planning and drive. Dopamine tends to limit and select sensory information arriving from the thalamus to the forebrain. Poor regulation of dopamine pathways has been associated with schizophrenia.

The so-called executive functions of the frontal lobes involve the ability to recognize future consequences resulting from current actions, to choose between good and bad actions (or better and best), override and suppress unacceptable social responses, and determine similarities and differences between things or events.

The frontal lobes also play an important part in retaining longer term memories which are not task-based. These are often memories with associated emotions, derived from input from the brain's limbic system, and modified by the higher frontal lobe centers to generally fit socially acceptable norms (see executive functions above). The frontal lobes have rich neuronal input from both the alert centers in the brainstem, and from the limbic regions.

Psychological tests that measure frontal lobe function include Finger Tapping, Wisconsin Card Sorting, and measures of verbal and figural fluency.

Psychosurgery Edit

In the early 20th century, a medical treatment for mental illness, first developed by Portuguese neurologist Egas Moniz, involved damaging the pathways connecting the frontal lobe to the limbic system. Frontal lobotomy (sometimes called frontal leucotomy) successfully reduced distress but at the cost of often blunting the subject's emotions, volition and personality. The indiscriminate use of this psychosurgical procedure, combined with the severe side effects and dangerous nature of the operation gained it a bad reputation and the frontal lobotomy has largely died out as a psychiatric treatment.

More precise psychosurgical procedures are still occasionally used, although are now very rare occurrences. They may include procedures such as the anterior capsulotomy (bilateral thermal lesions of the anterior limbs of the internal capsule) or the bilateral cingulotomy (bilateral thermal lesions of the anterior cingulate gyri) and might be used to treat otherwise untreatable obsessional disorders or clinical depression.

See alsoEdit

Telencephalon (cerebrum, cerebral cortex, cerebral hemispheres) - edit

primary sulci/fissures: medial longitudinal, lateral, central, parietoöccipital, calcarine, cingulate

frontal lobe: precentral gyrus (primary motor cortex, 4), precentral sulcus, superior frontal gyrus (6, 8), middle frontal gyrus (46), inferior frontal gyrus (Broca's area, 44-pars opercularis, 45-pars triangularis), prefrontal cortex (orbitofrontal cortex, 9, 10, 11, 12, 47)

parietal lobe: postcentral sulcus, postcentral gyrus (1, 2, 3, 43), superior parietal lobule (5), inferior parietal lobule (39-angular gyrus, 40), precuneus (7), intraparietal sulcus

occipital lobe: primary visual cortex (17), cuneus, lingual gyrus, 18, 19 (18 and 19 span whole lobe)

temporal lobe: transverse temporal gyrus (41-42-primary auditory cortex), superior temporal gyrus (38, 22-Wernicke's area), middle temporal gyrus (21), inferior temporal gyrus (20), fusiform gyrus (36, 37)

limbic lobe/fornicate gyrus: cingulate cortex/cingulate gyrus, anterior cingulate (24, 32, 33), posterior cingulate (23, 31),
isthmus (26, 29, 30), parahippocampal gyrus (piriform cortex, 25, 27, 35), entorhinal cortex (28, 34)

subcortical/insular cortex: rhinencephalon, olfactory bulb, corpus callosum, lateral ventricles, septum pellucidum, ependyma, internal capsule, corona radiata, external capsule

hippocampal formation: dentate gyrus, hippocampus, subiculum

basal ganglia: striatum (caudate nucleus, putamen), lentiform nucleus (putamen, globus pallidus), claustrum, extreme capsule, amygdala, nucleus accumbens

Some categorizations are approximations, and some Brodmann areas span gyri.

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