Chapter 3 Puberty and Biological Foundations - The McGraw-Hill ...

Synaptic density
70
60
50
40
30
20
10
birth 1 year 3 years 11 years adult
0
100 200 300 400 500 600 800 1,000 1,500 2,000 3,000 4,000 6,000 8,000 10,000
FIGURE 3.10 Synaptic Density in the Human Brain from Infancy to Adulthood. The graph
shows the dramatic increase and then pruning in synaptic density for three regions of the brain: visual
cortex, auditory cortex, and prefrontal cortex. Synaptic density is believed to be an important indication
of the extent of connectivity between neurons.
to increased risk taking and the use of addictive drugs (Spear, 2000). Increases in
dopamine may also be related to an increase in the onset of schizophrenia, one of the
most debilitating mental disorders, during adolescence (Walker, 2002).
Brain Structure
Newborn
Visual cortex (vision)
Auditory cortex (hearing)
Prefrontal cortex (reasoning,
self-regulation)
Age in days (from conception)
Adolescence
Neurons do not simply float in the brain. Connected in precise ways, they form the
various structures in the brain. Among brain structures that have recently
been the focus of research in adolescent development are the
four lobes in the highest part of the brain—the cerebral cortex (see figure
3.11). The occipital lobe is involved in visual functioning, the temporal
lobe in hearing, the parietal lobe in the perception of bodily
sensations, and the frontal lobe in reasoning and personality.
One of the main reasons scientists only recently have begun to
study brain development in adolescence has been a lack of technology
to do so. However, the creation of sophisticated brain scanning devices,
such as magnetic resonance imaging (MRI), is allowing better detection
of changes in the brain during adolescence (Giedd, 2004; Nelson,
Thomas, & de Hann, 2006; Sowell & others, 2002). Magnetic resonance
imaging consists of creating a magnetic field around a person’s body
and bombarding the brain with radio waves. The result is a computerized
image of the brain’s tissues and biochemical activities.
Using MRIs, scientists have recently discovered that children’s and
adolescents’ brains undergo significant anatomical changes between 3
and 15 years of age (Thompson & others, 2000). By repeatedly scanning
the brains of the same individuals over as many as four years, they
identified rapid, distinct spurts of growth. The amount of material in
some areas of the brain nearly doubled within as little as one year of
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Frontal (voluntary
movement and
thinking)
Smell
Hearing
Temporal
(hearing)
The Brain 79
Parietal
(body sensations)
Occipital
(vision)
Cerebellum
(balance and
muscle coordination)
FIGURE 3.11 The Brain’s Four Lobes. Shown here are the
locations of the brain’s four lobes: frontal, occipital, temporal,
and parietal.