Abnormal Psychology

Schizophrenia and Other Psychotic Disorders 543

Biological marker

A neurological, bodily, or behavioral

characteristic that distinguishes people with

a psychological disorder (or a fi rst-degree

relative with the disorder) from those

without the disorder.

her pregnancy, Maud Genain had such bad nausea that her weight dropped from

150 pounds before her pregnancy to 117 pounds a few months into her pregnancy

(Rosenthal, 1963). However, we must note that the research results are based on

data from many people, and thus we must always be careful when applying data

from a group (the members of which varied) to specifi c individuals (the Genains).

Maternal Illness and Stress A second possible cause of brain abnormalities is

maternal illness (Brown et al., 2004; Buka et al., 1999; Ellman, 2008; Mednick et al.,

1998). Maternal illness during the 6th month of pregnancy is of particular concern.

During fetal development, neurons travel to their fi nal destination in the brain and

establish connections with other neurons (this process is called cell migration). If

the mother catches the fl u or another viral infection in the second trimester, this may

disrupt cell migration in the developing fetus’s brain, which causes some neurons to

fall short of their intended destinations. Because the neurons are not properly po-

sitioned, they form different connections than they would have formed if they had

been in the correct locations—leading to abnormal neural communication (Arnold

et al., 1991; David, 1994; Green, 2001; McGlashan & Hoffman, 2000). The cogni-

tive defi cits associated with schizophrenia could be related to such abnormalities

in cell migration: Various brain areas may not be set up properly to allow smooth

communication within and among them. However, among those who have no fam-

ily history of schizophrenia or related disorders, maternal malnutrition or illness

accounts for only a small percentage of cases of schizophrenia (Green, 2001).

Signifi cant maternal stress in the fi rst trimester (such as the death of the mother’s

parent) has also been associated with higher rates of schizophrenia in the children

(Ellman, 2008; Khashan et al., 2008).

Oxygen Deprivation Another possible source of the abnormal brain structure and

function found in schizophrenia is prenatal or birth-related medical complications that

lead to oxygen deprivation (Cannon, 1997, 1998; Geddes & Lawrie, 1995; McNeil,

Cantor-Graae, & Weinberger, 2000; Zornberg, Buka, & Tsuang, 2000). Studies have

shown that people with schizophrenia who did not receive enough oxygen at specifi c

periods before birth have smaller hippocampi than do people with schizophrenia who

were not deprived of oxygen during or before birth (van Erp et al., 2002). As noted

earlier, the hippocampus plays a role in memory, and thus a reduced size of this brain

structure may help explain some of the problems with working memory that

can arise in people with schizophrenia.

Although inadequate oxygen before or during birth may contribute to

making a person vulnerable to schizophrenia, it does not cause the disorder.

A relatively large number of infants experience this problem during birth and

do not go on to develop schizophrenia (Clarke, Harley, & Cannon, 2006).

Biological Markers

People with schizophrenia, and even some of their unaffected family mem-

bers, may exhibit distinctive behaviors in specifi c situations or when per-

forming specifi c tasks—behaviors that are not displayed by other people.

When a neurological, bodily, or behavioral characteristic distinguishes

people with a psychological disorder (or people with a fi rst-degree rela-

tive with the disorder) from people who do not have the disorder, it is

said to be a biological marker for the disorder. One biological marker

for schizophrenia, but not other psychological disorders, is diffi culty in

maintaining smooth, continuous eye movements when tracking a light as

it moves across the visual fi eld—such tracking is called smooth pursuit eye

movements (Clementz & Sweeney, 1990; Holzman et al., 1984; Iacono et al.,

1992). This diffi culty refl ects underlying neurological factors, and is associ-

ated with irregularities in brain activation during motion processing (Hong

et al., 2005). Although it is not clear exactly why people with schizophrenia

and their family members have this specifi c diffi culty (Holzman et al., 1988),

researchers believe that it can help to identify people who are vulnerable for

developing schizophrenia. Figure 12.4 shows the results of smooth pursuit

eye movement recordings for the Genain sisters.

12.4 • Genain Sisters’ Smooth

Pursuit Eye Movements The Genain

sisters completed this test in 1981. The

results show that Nora and Hester had more

irregularities in their eye movements and they

also performed more poorly on some of the

neuropsychological tests, indicating that they

were more neurologically impaired.

Figure 12.4

Nora

1 sec

Myra

Iris

Hester

Dr. Deborah Levy of Mclean Hospital in Massachusetts obtained this data.