Brain damage can produce horrific effects, including paralysis, sensory loss, memory loss, and personality deterioration. When such damage occurs, can the brain recover some or all of its functions? Recovery from brain damage varies considerably from one case to another, depending on the age of the individual and the extent of the damage.

The human brain shows the most plasticity in young children before the functions of the cortical regions become entirely fixed (Kolb, 1989). For example, if the speech areas in an infant's left hemisphere are damaged, the right hemisphere assumes much of this language function. However, after age 5, permanent damage to the left hemisphere can permanently disrupt language ability.

A key factor in recovery is whether some, or all, of the neurons in an affected area are just damaged or are completely destroyed. If the neurons have not been destroyed, brain function often is restored over time.

The damaged brain has three methods of repair:

• Collateral sprouting. The axons of some healthy neurons adjacent to damaged cells may grow new branches.
• Substitution of function. The damaged region's function may be taken over by another area, or areas, of the brain.
• Neurogenesis. New neurons may be generated. Neuroscientists long believed that all of the neurons an individual will ever have are present soon after birth. However, they have recently found that human adults can generate new neurons (Kempermann & Gage, 1999). Researchers also discovered that adult monkeys' brains can create thousands of new neurons each day (Gould & others, 1999). There now is good evidence that neurogenesis is much more pervasive than previously thought. If researchers can discover how new neurons are generated, possibly the information can be used to fight degenerative diseases of the brain, such as Alzheimer's disease and Parkinson's disease (Gage, 2000).

1		A PET scan of the brain of a young woman whose temporal lobe has been damaged shows a high level of glucose in an adjacent area of the occipital lobe while she is listening to music. This finding may indicate that the brain is repairing itself by
			A)	collateral sprouting
			B)	substitution of function
			C)	neurogenesis
			D)	brain grafting
2		The generation of new neurons is called .
3		If a 6-year-old child and 40-year-old adult suffer the same amount of damage to the same area of the brain, the child is most likely to acquire or reacquire the functions controlled by the damaged area.
			A)	TRUE
			B)	FALSE