The Hemispheres

Common phrases overheard these days are right-brained and left-brained. These phrases refer to the primary location for specific mental activities within the brain structure (see Figure 25). The left hemisphere communicates with and controls the right side of the body, while the right hemisphere communicates with and controls the left side of the body. Although both hemispheres communicate with each other and share some functions, one hemisphere is considered dominant. The dominant hemisphere is the site for thought processes more involved in detailed and sequential analysis.

Thalamus

Thalamus

Figure 2-5 Basic structure of the brain

Whichever hemisphere is dominant, it is the other hemisphere that holds appreciation of forms and humor, mental arousal, physiological readiness to respond, orientation in space, recognition of voice timbre, musical talent, and appreciation of things that do not lend themselves to verbal descriptions.12 This hemisphere is considered to be the home site for global thought processes that can be described as the "Aha!" response, which is exhibited when a sudden understanding of a concept occurs without the ability to describe how the understanding was achieved. It often is assumed that the left hemisphere controls the verbal and analytical processes, while the right hemisphere handles the artistic, emotional, abstract relationships. This is true for only a portion of the population.

There are some clues, however, as to which hemisphere is dominant. Approximately 99 percent of the right-handed population and 56 percent of the left-handed population write with the hand in a noninverted position. One percent of the right-handed population and 44 percent of the left-handed population write with the hand in an inverted position (see Figure 2-6). Dr. Jerre Levy performed experiments that revealed that the inverted hand position is a biological marker indicating that the hemisphere considered dominant for analytical specialization is on the same side as the writing hand. For those people who write with the hand in a noninverted position, the hemisphere opposite that hand is dominant. For discussion purposes, and because it is the case for most of the population, we will consider the left hemisphere of the brain to be the site for verbal and analytical abilities for the rest of this text.

We have all heard jokes regarding the differences between men and women. There is a biological basis for many of the qualities men and women find confusing about each other. For example, men and women differ at a very basic level from the description just given for the dominant hemisphere. While men's verbal abilities are predominantly

Figure 2-6 Hand position as a marker for hemisphere dominance

stored in a centralized location in the left hemisphere, a woman's verbal abilities are more diffusely located on both sides of the brain. This might explain why men have a slightly more difficult time expressing their emotions. They have to get the emotional information from the right hemisphere across the primary bridge (corpus callosum) to their verbal abilities in the left hemisphere, whereas women have some verbal abilities already located on the same side as their emotions.13 See Chapter 3, "Teach Your Brain Agility," for more details of gender differences.

Each hemisphere is further divided into lobes.

Each lobe has generalized functions. The frontal lobes have the capability to plan for the future, control movement, integrate emotional responses, and produce speech. The parietal lobes receive and process information received from the senses—such as pain, taste, and smell—and are involved with logic and mathematical processes. The occipital lobes handle vision. The temporal lobes hear and interpret language, tones, sound patterns, and music; and participate in emotion. The limbic lobe is responsible for sexual, emotional, and memory processing14 (see Figure 2-7).

Researchers at the University of Toronto's Baycrest Center for Geriatric Care announced that the frontal lobes are where humor is processed. People with a brain injury to a frontal lobe don't get punch lines. They prefer slapstick

Figure 2-7 Side and central cross sectional views of the lobes

humor! The people with damage to that area had difficulty selecting the correct response to a joke similar to this one:

A teenager is being interviewed for a summer job.

"You'll get $50 a week to start off," says his boss. "Then after a month, you'll get a raise to $75 a week."

Punch-line selection:

A. "I'd like to take the job. When can I start?" (straightforward logical choice)

B. "That's great! I'll come back in a month." (correct funny choice—original punch line)

C. "Hey boss, your nose is too big for your face!" (slapstick ending—right-frontal damaged patients are likely to choose this one)15

Now that we have led you through a discussion of the brain's general anatomy and structure, let's talk about the brain, learning, and intelligences so that we can apply this information to our learning capability. You know your abilities and talents. Maybe you are talented at fixing things, cooking, writing, solving crossword puzzles, cheering other people up, or gardening. Before you begin reading about intelligences (and all these "talents" are actually forms of intelligence), review your skills and abilities. Then see whether you recognize yourself in any of these intelligences. The following facts and figures will provide you with some interesting information if you have ever dealt with someone who has had a stroke or other brain injury.

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