Schizophrenia
For the nation's one million schizophrenics, the extravagant
delusions that come with the territory are as real as the perceptions of
you and me. After all, they originate in the same place-the labyrinthine
loops of the brain's neuronal networks.
Since 1809, when doctors first described schizophrenia,
psychiatrists and neuroanatomists have searched for clues to explain why
and how the disease occurs. But only recently have researchers discovered
distinctive patterns of metabolic activity in the brains of
schizophrenics. Using a scanning technique called positron emission
tomography, or PET, they are glimpsing the brain in exquisite anatomic
detail once thought unimaginable.
The kaleidoscopic images on PET scans suggest that there are
structural defects in certain regions of schizophrenic brains which may
lead them to process and retain information differently from healthy
brains. Such alterations can produce behavior from the extravagantly
bizarre to intense withdrawal, prolonged apathy, and other emotional or
affective disturbances.
o In the brain's frontal lobes, PET scans show that the
front-to-back ratio of blood is much lower in schizophrenic brains than
in normal brains. Because these regions are vital in processing abstract
thought, planning, and judgment, investigators believe this frontal lobe
dysfunction may underlie the typical feelings of disorganization that
often characterize schizophrenia.
o Abnormalities newly found in neural pathways that control memory
and emotion may contribute to the troubles schizophrenics have retrieving
information and linking the proper emotion to the proper circumstance.
Carol A. Tamminga, M.D., and colleagues at the University of Maryland
detected in schizophrenics greatly reduced metabolism of glucose, the
brain's main fuel, in two structures--the subcortical hippocampus and the
cingulate gyrus of the cortex.
Because the sea-horse shaped hippocampus is involved in memory
function and the cingulate gyrus controls the body's emotions, neuronal
underfunction here could explain, for example, why schizophrenics laugh
at funerals or cry at inappropriate times, Dr. Tamminga and company
report in Archives of General Psychiatry (Vol. 49, No. 7).
o The Maryland researchers also found that in certain types of
schizophrenia, additional areas of the brain may also have lower levels
of glucose metabolism. Schizophrenics with deficit symptoms such as
reduced social interaction and thought paucity, for example, had
significantly less glucose activity in the thalamus, and in the frontal
and parietal cortex, compared to people with nondeficit
schizophrenia.
Because the thalamic and cortical areas are integrally involved in
accepting and processing sensory input from the environment, Dr. Tamminga
and other scientists believe that abnormalities in these regions may
alter or blunt the impact of external stimuli as they travel the pathway
through the thalamus and into the cortex. As a result, deficit
schizophrenics may actually experience a different world than the
nondeficit or normal individual.
While the findings lend weight to the biological underpinnings of
the disease, the diversity of the metabolic disarray has left scientists
baffled. "No one knows for sure if schizophrenia is one illness, like
diabetes, or a multiple illness like epilepsy and mental retardation,"
says Dr. Tamminga.
PARIETAL CORTEX
Regulates sensory function. Abnormalities here alter interpretation
of external stimuli.
FRONTAL CORTEX
Key to abstract thought. Abnormalities here linked to schizophrenic
feelings of disorganization.
CINGULATE GYRUS
The emotional center. Schizophrenic brains have trouble linking
feelings to circumstances. Part of limbic system.
THALAMUS
Processes sensory input. Defects here blunt impact of external
stimuli
HIPPOCAMPUS
Regulates memory function. Defects here hinder information
retrieval. Part of limbic system.
DIAGRAM: The anatomy of madness (SCOTT MACNEILL)
Tags:
abstract thought,
brain,
brains,
cingulate gyrus,
delusions,
distinctive patterns,
emission tomography,
frontal lobe,
frontal lobes,
illness,
kaleidoscopic images,
metabolic activity,
neural pathways,
neuronal networks,
PET scan,
pet scans,
scanning technique,
schizophrenia,
subcortical,
symptom
