Biomedical Engineering Reference
In-Depth Information
receptor binding; (b) functional differences in responses to normative stimuli
(i.e., pictures of emotional faces that are rapidly masked in an effort to present
them subconsciously); (c) volumes of brain structure,; or (d) quantifiable chemi-
cal signatures of neuronal integrity. In Figure 12, anxiety disorders (1), major
depressive disorder (2), and addiction (3) are displayed along a potential contin-
uum along the left side of the figure. Behavioral disorders (4) and schizophrenia
(5) are segregated on the right side of the figure. The studies compiled for anxi-
ety disorder (1) focused on post-traumatic stress disorder, social phobia, and
simple phobia; this compilation included symptom provocation studies that were
compared across illness category but not to a healthy control group (211,212,
225,226). The studies compiled for major depression (2) were focused on (a)
recurrent depression with strong familial loading (i.e., familial pure depressive
disorder), (b) primary depression with and without obsessive-compulsive disor-
der and without manifested familial connections, and (c) primary and secondary
depression in older subjects studied postmortem (30,39,40,81-84,90,141,161,
181,193,209,210,219,223). These studies are compiled together in Figure 12,
and segregated for 1-3 in Figure 13. Multiple stimulant addictions were grouped
for addiction (3) (55,94,100,104,107,151,256-259). The studies compiled for
behavioral disorders (4) were grouped following more recent suggestions that
place obsessive-compulsive disorder (OCD) on a continuum with tics
(Tourette's), attention-deficit hyperactivity disorder, and other behavioral prob-
lems such as conduct disorder, oppositional behavior, and learning disabilities
(130). For this particular metaanalysis, the focus was on studies of OCD
(13,14,36,92,108,185,199,222,223,244). Lastly, the studies compiled for schizo-
phrenia (5) used subjects who were not actively psychotic, and included studies
with relevance to negative symptomatology such as amotivation, avolition, and
anhedonia (8,63,103,115,162,163).
In sum, the studies compiled for anxiety disorder, major depressive disor-
der, addiction, behavioral disorders, and schizophrenia reveal differences be-
tween patient and control groups primarily in the subcortical gray matter and
paralimbic cortices illustrated in Figure 11. These brain regions mediate sub-
processes such as reward/aversion assessment, which are fundamental to emo-
tional function and the generation of motivated behavior (1,7,23,33,38,73,
147,174,215,227,238,263,266). Dysfunction of these brain regions has been
previously hypothesized to be responsible for a variety of psychiatric symptoms
such as olfactory or gustatory hallucinations, autonomic discharges, episodic
amnesias, depersonalizations, avolition (or lack of motivation), abulia (or lack of
will), anaffectiveness (or affective flattening), asociality, as well as delusion,
hallucinations, thought disorder, and bizarre or disorganized behavior (276,277).
A circuitry-based nosology for neuropsychiatric illnesses would facilitate
the identification of endophenotypes for these disorders (4,81,101,149,161),
particularly as morphometric MRI studies allude to the heritability of structural
alterations (179,248). Disorders such as depression have been hypothesized to
