The Nervous System 219There is great hope that such discoveries will lead
to effective treatments for these and other degen-
erative neurologic conditions.
Other research focuses on replacing lost or
damaged nervous system tissue. STEM CELLtrans-
plantation, still experimental, shows promise for
treating conditions such as Parkinson’s disease,
Alzheimer’s disease, MULTIPLE SCLEROSIS, AMY-
OTROPHIC LATERAL SCLEROSIS(ALS), and spinal cord
injury. Researchers are also combining GENEand
molecular technologies to cultivate neurons in the
laboratory with the hope of providing additional
sources of transplantable cells.
Other breakthroughs involve new understand-
ing about how the brain functions. Highly sophis-
ticated imaging technologies such as POSITRON
EMISSION TOMOGRAPHY(PET) SCANandSINGLE PHOTON
EMISSION COMPUTED TOMOGRAPHY(SPECT) SCANallow
researchers to observe changes in the brain during
brain activity. Such observations have provided
insights into the processes of memory and cogni-
tive function and offer an objective means for
assessing the effectiveness of therapeutic
approaches for neurologic disorders such as
Alzheimer’s disease, Parkinson’s disease, and
seizure disorders.
In the 1980s scientists discovered the brain has
the ability to reorganize the way it functions to
some degree, allowing different areas of the brain
to take over for certain areas that become dam-
aged. Whether this process permits the brain to
default to abandoned pathways or to create new
pathways remains unknown. Researchers con-
tinue to explore the mechanisms of this reorgani-
zation, hopeful that further discoveries will lead to
therapies to retrain the brain after stroke or trau-
matic brain injury and perhaps to compensate for
functional losses due to disease processes such as
those that occur with multiple sclerosis and
Alzheimer’s disease.