Frontal lobes
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The frontal lobe is an area in the brain of mammals. It is located at the front of each cerebral hemisphere and positioned anterior to (in front of) the parietal lobes and above and anterior to the temporal lobes. It is separated from the parietal lobe by the primary motor cortex, which controls voluntary movements of specific body parts associated with the precentral gyrus.
The frontal lobe reaches full maturity around age 25, marking the cognitive maturity associated with adulthood. Arthur Toga, UCLA, found increased myelin in the frontal lobe white matter of young adults compared to that of teens. A typical onset of schizophrenia in early adult years correlates with poorly myelinated and thus inefficient connections between cells in the fore-brain.
The frontal lobe contains most of the dopamine-sensitive neurons in the cerebral cortex. The dopamine system is associated with reward, attention, long-term memory, planning, and drive. 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.
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[edit] Anatomy
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.
[edit] Function
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.
[edit] Executive control
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).
The 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.Therefore, it is involved in higher mental functions.
[edit] Memory
The frontal lobes also play an important part in retaining longer term memories which are not task-based. These are often memories associated with emotions derived from input from the brain's limbic system. The frontal lobe modifies those emotions to generally fit socially acceptable norms.
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.
[edit] Role in mental health
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.
[edit] Other
Frontal lobes have been found to play a part in impulse control, judgment, language, memory, motor function, problem solving, sexual behavior, socialization and spontaneity.
[edit] Developmental aspects
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.
[edit] Assessment of function
Psychological tests that measure frontal lobe function include Finger Tapping, Wisconsin Card Sorting, and measures of verbal and figural fluency.
[edit] Theories of function
Theories of frontal lobe function can be differentiated into four categories:
- Single-process theories. Posit "that damage to a single process or system is responsible for a number of different dysexecutive symptoms” (Burgess, 2003, p. 309).
- Multi-process theories. Propose “that the frontal lobe executive system consists of a number of components that typically work together in everyday actions [(heterogeneity of function)]“ (Burgess, 2003, p. 310).
- Construct-led theories. Assume “that most if not all frontal functions can be explained by one construct (homogeneity of function) such as working memory or inhibition” (Stuss, 1999, p. 348; cf. Burgess & Simons, 2005).
- Single-symptom theories. Suggest that a specific dysexecutive symptom (e.g., confabulation) is related to the processes and construct of the underlying structures (cf. Burgess & Simons, 2005)
Stuss (1999) suggests a differentiation into two categories according to homogeneity and heterogeneity of function.
Further theoretical approaches to frontal lobe function include:
- Grafman's managerial knowledge units (MKU) / structured event complex (SEC) approach (cf. Wood & Grafman, 2003)
- Miller & Cohen's integrative theory of prefrontal functioning (e.g. Miller & Cohen, 2001)
- Rolls's stimulus-reward approach and Stuss's anterior attentional functions (Burgess & Simons, 2005; Burgess, 2003; Burke, 2007).
It may be highlighted that the theories described above differ in their focus on certain processes/systems or construct-lets. Stuss (1999) remarks that the question of homogeneity (single construct) or heterogeneity (multiple processes/systems) of function “may represent a problem of semantics and/or incomplete functional analysis rather than an unresolvable dichotomy” (p. 348). However, further research will show if a unified theory of frontal lobe function that fully accounts for the diversity of functions will be available.
[edit] Studies of frontal lobe damage
- Main article: Studies of frontal lobe damage
[edit] Psychosurgery
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.
[edit] Additional images
Illu cerebrum lobes.jpg
Lobes |
 Base of brain. |
BrainLobesLabelled.jpg
Human brain showing the four major lobes of the cerebrum. Beneath the cerebral cortex are the cerebellum, pons, olive, and medulla oblongata |
 Drawing to illustrate the relations of the brain to the skull. |
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| This page uses content from the English-language version of Wikipedia. The original article was at Frontal Lobes. The list of authors can be seen in the page history. As with Psychology Wiki, the text of Wikipedia is available under the GNU Free Documentation License. |
