Friday, May 29, 2009

Frontal Lobe

The frontal lobe is the anterior portion of the cerebral cortex of humans. It is largest lobe of each cerebral hemisphere and is separated from the parietal lobe by the central sulcus of Rolando and from the temporal lobe by the lateral sulcus. The frontal lobe is responsible for the control of skilled motor activity, including speech.

In the frontal lobe, there are four important gyri. Roughly parallel and anterior to the central sulcus is the Precentral Gyrus, which is also called the motor strip. The precentral gyrus represents the primary motor cortex. This motor cortical area contains motor neurons whose axons extend to the spinal cord and brain stem and synapse on motor neurons in the spinal cord. Besides the roughly vertical Precentral Sulcus (anterior to the precentral gyrus), there are two additional sulci that are sort of diagonal. These sulci provide boundaries for important frontal gyri: the Superior Frontal Gyrus, the Middle Frontal Gyrus, and the Inferior Frontal Gyrus. The most anterior region of the frontal lobe is called the prefrontal cortex and includes all three of these gyri.

The frontal lobe integrates and coordinates all the other regions of the cerebral cortex and is the emotional control center and home to our personality. Injuries sustained by the frontal lobe can cause a wide variety of symptoms. The frontal lobe is involved in motor function, problem solving, spontaneity, memory, language, initiation, judgement, impulse control, and social and sexual behavior. The frontal lobes are extremely vulnerable to injury due to their location at the front of the cranium, proximity to the sphenoid wing and their large size. MRI studies have shown that the frontal area is the most common region of injury following mild to moderate traumatic brain injury.

There are asymmetrical differences between the two frontal lobes. The left frontal lobe is involved in controlling language related movement, while the right frontal lobe plays a role in non-verbal abilities. The executive functions of the frontal lobes include the capacity to recognize future consequences resulting from current actions, to suppress unacceptable social responses, choose between good and bad actions, and determine similarities and differences between things or events. In other words, it is involved in higher mental functions.

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. The frontal lobe reaches full maturity around age 25, marking the cognitive maturity associated with adulthood. It has been 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 nerve cells in the fore-brain. The frontal lobe of the brain acts like a cerebral projecting lens as mind that governs brain. When the lens-like frontal function fails, as in schizophrenia, the mind disintegrates.