How the Brain Learns by David A. Sousa

Author:David A. Sousa
Language: eng
Format: epub, pdf
Publisher: SAGE Publications
Published: 2018-02-28T14:49:43.727886+00:00

Structural and Developmental Differences

Males have a higher percentage of gray matter (the thin cortex layer containing mostly dendrites) in the left hemisphere than do females. In females, the percentage of gray matter is the same in both hemispheres. However, females have a higher percentage of total gray matter, whereas males have a higher percentage of white matter (mainly myelinated axons below the cortex layer) and cerebral spinal fluid. The corpus callosum (cable connecting the hemispheres) is proportionately larger and thicker in females than in males (Gur et al., 1999; Ingalhalikar et al., 2014). All of these differences could be further evidence to support the idea that female brains are better at communicating between hemispheres and male brains within those hemispheres.

For most right-handed males and females, the language areas are in the left hemisphere. But females also have an active language processor in the right hemisphere (see Figure 5.2). Females possess a greater density of neurons in the language areas than males (Burman, Bitan, & Booth, 2008; Gazzaniga, Ivry, & Mangun, 2002; Gur et al., 2000; Shaywitz, 2003). These differences may explain why females recover better than males from verbal impairment due to stroke.

The amygdala (which responds to emotional stimulation), loaded with testosterone receptors, grows more rapidly in teenage boys than in teenage girls, and its final size is larger in men than in women. This is at least a partial explanation of why males tend to demonstrate more overt aggressive behavior than do females. PET scans reveal that during emotional stimulation, females tend to activate the amygdala only in the left hemisphere while males tend to activate the amygdala only in the right hemisphere. Follow-up studies noted that females remembered the details of an emotional event (a typical left-hemisphere function) better than did males, whereas the males remembered better the central aspects, or gist, of the situation (Cahill, 2005; Kreeger, 2002).

Meanwhile, the hippocampus (responsible for memory formation and consolidation), filled with estrogen receptors, grows more rapidly in girls than in boys during adolescence (Ingalhalikar et al., 2014; Kreeger, 2002). This could explain why preadolescent girls are generally better at language, arithmetic computations, and tasks involving sequence because all these depend on efficient memory processing.

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