36 CHAPTER 2
return to baseline. The HPA axis and cortisol levels are involved in depression
and stress-related psychological disorders such as posttraumatic stress disorder
(PTSD),an anxiety disorder that can arise after a person experiences a trau-
matic event.
The other part of the ANS is the parasympathetic nervous system, which set-
tles you down after a crisis is over: The parasympathetic nervous system slows the
heart, contracts the pupils, and also increases the activity of the digestive tract. The
parasympathetic system typically counteracts the effects of the sympathetic nervous
system, and psychopathology may arise if it fails to do so effectively. In fact, dys-
functional activity in the parasympathetic nervous system has been associated with
various psychological problems, such as anxiety disorders, disruptive behavior, and
hostility (Pine et al., 1998).The Four Brain Lobes
Let’s now focus on one part of the CNS, the brain. As shown in
Figure 2.2, the brain has four major lobes: occipital lobe, parietal
lobe, temporal lobe, and frontal lobe. The brain is divided into two
hemispheres (or half-spheres), left and right, and each hemisphere
has all four lobes (although they do not have identical functions in
the two hemispheres). Let’s start with the back of the brain. When
the eyes are stimulated by light, they send neural impulses into the
brain; the fi rst area to process this information in detail is the occipi-
tal lobe, which is at the very back of the brain. This lobe is entirely
dedicated to the function of vision.
Two major neural pathways lead forward from the occipital
lobes. One extends up into the parietal lobe, at the top, back of
the brain. This lobe processes spatial information, such as the rela-
tive location of objects. The parietal lobe also has other functions,
including a role in self-awareness. The second neural pathway from
the occipital lobe leads down to the temporal lobe (so named be-
cause it lies under the temple), which stores visual memories, pro-
cesses auditory information, and decodes the meaning of speech; the
temporal lobe also contributes to conscious experience. Abnormal
functioning in the temporal lobe can produce intense emotions,
such as elation when a person is manic (Gyulai et al., 1997), and is
associated with auditory hallucinations (Plaze et al., 2006).
Both the parietal lobe and the temporal lobe send information to the frontal
lobe, which is located right behind the forehead. The frontal lobe plays crucial roles
in feeling emotions and using emotional responses in decision making, as well as in
thinking and problem solving more generally; it is also involved in programming ac-
tions and controlling body movements. Because these functions are so important to
the vital activities of planning and reasoning, the frontal lobe is sometimes referred
to as the seat of executive functioning; its role is much like that of the head of a suc-
cessful company—an executive—who plans the company’s future and formulates
responses to obstacles that arise. Abnormalities in the frontal lobe, and in execu-
tive functioning, are associated with schizophrenia, a psychological disorder char-
acterized by profoundly unusual and impaired behavior, expression of emotion, and
mental processing (Bellgrove et al., 2006; Morey et al., 2005).The Cortex and Beneath the Cortex
Thecerebral cortex is the outer layer of cells on the surface of the brain; it contains the
majority of the brain’s neurons, the cells that process information related to our physi-
cal, mental, and emotional functioning. Most of the brain functions just described are
carried out primarily in the cortex of the corresponding lobes. But many important
brain functions are carried out in subcortical areas, beneath the cortex, as shown
in Figure 2.3.Cerebral cortex
The outer layer of cells on the surface of the
brain.
Neurons
Brain cells that process information related to
physical, mental, and emotional functioning.
Figure 2.22.2 • 22 The Lobes of the Brainhbfh i
Temporal lobeFrontal lobe Parietal lobeOccipital
lobe