Written by Nancy Jo Melucci, Santa Monica College

3. Hemispheric Activity Interferes With Ability to Work a Counter

Here is a classroom exercise that proves to be both very enjoyable and very informative about the functioning of the two sides of the brain. The only equipment you will need is a simple counter, the kind used at stadiums to count people as they pass through the gate.

Recruit a volunteer and have her sit in front of the class. She should hold the counter in her right hand, and when you say, “Go!” press it as fast as she can. Stop her after about 30 seconds and record the number of presses; this number will be your baseline level for the right hand. Reset the counter and repeat the procedure for the left hand to get a left hand baseline.

During the next phase of your experiment, the subject should again perform with the right and left hands but this time should do so while reciting a poem or speech (the Pledge of Allegiance works well). These two bits of data are your right and left “oral data.” In the next phase, the subject should perform with the right and left hands but this time should do so while humming a familiar tune. Encourage the students to hum and not to worry about the words. These two bits of data are your left and right “music data.”

The hypothesis in this experiment is that talking will interfere more with right-hand pressing, whereas humming will interfere more with left-hand pressing, due to the hemispheric specializations involved in these tasks.

Written by Nancy Jo Melucci, Santa Monica College

B. Promoting Discussion

1. Neurogenesis Alcohol

The Crews & Nixon (2003) article “Alcohol, Neural Stem Cells, and Adult Neurogenesis” discusses both genetic and environmental contribution on the process of neurogenesis. A “quick” definition of neurogenesis is the development of new cells in the brain. Previously it was thought that we are born with all of the neurons that we will ever have. Recent research suggests that certain parts of the brain do in fact “replace” or “grow” new neurons. Here are a few quotes from the Crews and Nixon (2003) article on this process:

Stem cells are cells that can divide indefinitely, renew themselves, and give rise to a variety of cell types. … Multipotent stem cells, including neural stem cells (NSCs), are more restricted in the types of cells they are capable of producing or becoming.

The discovery of NSCs and adult neurogenesis provides a new theoretical framework for understanding processes regulating brain plasticity.

Genetics influences the three main components of neurogenesis: NSC proliferation, cell survival, and cell differentiation into neurons and other types of brain cells.

We see neurogenesis in two areas of the brain:

1) Subventricular zone (SVZ) of the anterior lateral ventricles (this location is the origin for olfactory bulb neurons)

2) Dentate gyrus of the hippocampus (part of the brain that is involved with learning and memory) [neurogenesis for this part of the brain has been confirmed in rodents and in humans].

This is one of the main points Crew and Nixon make: “Interesting, genetics and specific environmental factors play an important role in regulating neurogenesis, and these same environmental factors … are key factors in the risk of developing alcoholism.”

Discussion Points:

• What are the different ways in which there is plasticity in the brain?

• Plasticity in the brain is due to a number of different factors. These can include neuronal growth (neurogenesis), changes in dendritic connections among neurons, and changes in chemicals bonds.

• In addition to alcohol, name other potential environmental factors that many influence neurogenesis.

• Researchers have been able to culture neural stem cells (NSCs) from a number of different regions in the brain. Ask students what are the implications for this. Two important points:

• The ability to do so, suggests that a variety of regions of the brain have the potential for neurogenesis.

• However, in most areas these cells are suppressed from dividing.

• What are the contributions of nature and nurture on neurogenesis?

• An enriched environment is a factor that tends to promote neurogenesis. Physical activity in particular seems to be helpful.

• Stress is an environmental factor that reduces neurogenesis.

• Alcohol decreases the proliferation of neural stem cells. However, the effect (at least in rats) is not seen until several weeks later.

• Serotonin is known to influence the neural stem cell proliferation in adults. Depression is associated with a decrease in the amount of serotonin released. The mechanism behind selective serotonin reuptake inhibitors (SSRIs) (an antidepressant), according to some researchers, is that is increases neurogenesis.

• Neurogenesis is seen in the hippocampus. What are the implications of neurogenesis in this particular region of the brain?

• The hippocampus in involved in learning and memory. Lack of neurogenesis in this particular part of the brain would have an impact on our ability to form new memories.

• What are the implications of the extent to which environmental stimuli can have an impact on cognitive functions?

• Alcohol can have an impact on brain functioning (physiological functioning that in turn can have an impact on psychological functioning)—this may potentially impact a number of different processes (e.g., perception, memory, attention, neuro-plasticity)

Written by Michael Bendele, Indiana University-Purdue University Fort Wayne