542 CHAPTER 12
A Frontal Lobe Defect?
Many studies have set out to discover whether people with schizophrenia have im-
paired frontal lobe functioning. The root of such impairment may lie in the fact that
the brain has too many connections among neurons at birth, and part of normal
maturation is the elimination, or pruning, of unneeded connections (Huttenlocher,
2002). Results suggest that an excess of such pruning takes place during adoles-
cence for people who develop schizophrenia: Too many of the neural connections in
the frontal lobes are eliminated, which may account for some of the neurocognitive
defi cits that typically accompany this disorder (Keshavan, Anderson, & Pettegrew,
1994; Pantelis et al., 2003; Walker et al., 2004).
In addition, some symptoms of schizophrenia are associated with abnormal activity
in specifi c brain areas; for example, people with schizophrenia often have too little
activity in part of the left frontal lobe, a lack that is associated with avolition. More-
over, studies have shown that disorganized symptoms are associated with abnormal
activity in the right frontal lobe (Liddle et al., 1992; Perlstein et al., 2001).Impaired Temporal Lobe and Thalamus?
Enlarged ventricles are associated with decreased size of the temporal lobes. This is sig-
nifi cant for people with schizophrenia because the temporal lobes process auditory infor-
mation, some aspects of language, and visual recognition (Levitan, Ward, & Catt, 1999;
Sanfi lipo et al., 2002). Abnormal functioning of the temporal lobes may underlie some
positive symptoms, notably auditory hallucinations, in people with schizophrenia.
The thalamus, which transmits sensory information to other parts of the brain,
also appears to be smaller and to function abnormally in people with schizophrenia
(Andreasen et al., 1994; Andrews et al., 2006; Konick & Friedman, 2001). Abnor-
mal functioning of the thalamus is associated with diffi culties in focusing attention,
in distinguishing relevant from irrelevant stimuli, and in particular types of memory
diffi culties, all of which are cognitive defi cits that can arise with schizophrenia.Abnormal Hippocampus?
The hippocampus—a subcortical brain structure crucially involved in storing new
information in memory—has also been a focus of schizophrenia research. Studies
have found that the hippocampi of people with schizophrenia and their fi rst-
degree relatives (parents and siblings) are smaller than those of control participants
(Nelson et al., 1998; Seidman et al., 2002; Vita et al., 2006), which may contrib-
ute to the defi cits in memory often experienced by some people with schizophrenia
(Holthausen et al., 2003; Olson et al., 2006; Yoon et al., 2008).Interactions Among Brain Areas
Some researchers propose that schizophrenia arises from disrupted interactions
among the frontal lobes, the thalamus, and the cerebellum—which may act as a time-
keeper, synchronizing and coordinating signals from many brain areas (Andreasen,
2001; Andreasen et al., 1999). According to this theory, the thalamus fails to screen
out sensory information, which overwhelms subsequent processing, and the form
and content of the person’s thoughts become confused. In addition, many patients
with schizophrenia have abnormal interconnections between the anterior cingu-
late cortex in the frontal lobe (which is involved in attention) and the hippocampus
(Benes, 2000), which may contribute to some of the disrupted cognitive functions.Possible Causes of Brain Abnormalities
How might these brain abnormalities arise? Researchers have identifi ed several possible
causes. Some researchers have focused on factors that could affect the developing brain
of a fetus or a newborn. The growing fetus can be affected if the mother is malnour-
ished. Similarly, development of the brain can be disrupted if the mother is signifi cantly
ill during her pregnancy. In addition, the brain can become impaired if oxygen is cut off
from the infant before or during birth. Let’s consider each of these possible causes.Maternal Malnourishment One possible cause of brain abnormalities is maternal
malnourishmentduring pregnancy, particularly during the fi rst trimester (Brown
et al., 1999; Wahlbeck et al., 2001). It is possible, for example, that Mrs. Genain’s
poor diet contributed to the quads’ schizophrenia: During the first trimester of