Home
Bibliography
Symptoms
Role of the Dorsolateral
Prefrontal Cortex in Schizophrenia
The Frontal Cortex
The classified negative symptoms of schizophrenia are characterized similarly to the cognitive and behavioral aspects of frontal lobe disease including impaired motivation, paucity of thought, and shallow affect. Frontal lobe impairment has consistently been implicated by the characteristic pattern of cognitive impairment in schizophrenics. Clinical observations of schizophrenics and inferences made by researchers surrounding frontal lobe dysfunction have been supported by various lines of research. Studies of frontal lobe lesions (damage) and brain imaging of regional blood flow have been the significant areas of study. The frontal cortex has also been found to be a heterogeneous region in terms of cognitive and behavioral influences. Over twenty years of research has led to a more accurate focus on specific regions of the frontal cortex associated with schizophrenia. Neuroanatomic, neurochemical and neuropharmachological data, along with the characteristic defect symptoms, all point to the dorsolateral aspect of the prefrontal cortex (DLPFC).
The
DLPFC
The DLPFC is a very unique part of the frontal cortex specific to almost only humans. This would lead us to believe apart from other reasons that it is one of the more highly evolved units of the human neocortex. The DLPFC's relation to schizophrenia is supported by the fact that frontal lobe disease or damage by tumors, aneurysms, infarction or psychosurgery, produces symptoms resembling that of schizophrenia
The role of the DLPFC is considered very complex and important for higher
human brain functions like working memory and conscious control of behavior. What is
physically known about the DLPFC is extensive in
terms of its neural projections to other parts of the brain and the time period
in which these projections develop.
The DLPFC has been found to be the last brain region to complete
myelination. It is unknown just how long the DLPFC keeps developing but it has been found to still be active up into the third decade of
life. Amazingly these connections have been found to extend and act on almost
every lobe in the brain and every type of association cortex.
Sections of the brain with which the
DLPFC interacts:
·
Limbic, Diencephalic,
and Mesencephalic nucleii (important for regulation of behavior)
·
Direct projections to
the locus coeruleus and raphe nuclei of the subcortical brain. It is the only
known cortical area to do this and this suggests that it can directly control
its own neurotransmitter input.
·
It also receives input
from the substantia nigra and ventral tegmental area.
Behavioral Manifestations of DLPFC Damage
Subtle cognitive and behavioral changes have been found characteristic of
negative schizophrenic symptoms among patients who suffered brain injuries
specific to the dorsolateral prefrontal cortex. Flat affect, social withdrawal
and ineffectiveness, impairment of goal related behaviors, inattentiveness, poor
motivation, and poor insight, are just a few of the major cognitive/behavioral
traits that appear strikingly similar in both schizophrenic patients and those
with DLPCF damage.
Another particular area of cognitive
performance affected by DLPCF damage surrounds IQ levels and problem-solving
skills that rely on the information processing resource known as working
memory.