Dr Maxwell: methods of investigating the nervous system

Question 1

why are methods important

Answer 1

Neuroscience is an experimental science. In all experimental sciences, knowledge is created by applying methods.
• “A science is only as good as its methods” : scientific “truths” have to be
constantly revised -new methods provide new information.
• Neuroscience uses methods borrowed from several disciplines, e.g. physiology,
anatomy, biochemistry, psychology, molecular biology.

Question 2

Foundations of neuroscience: disection

Answer 2

The Flemish anatomist, Vesalius (1543) made some of the first accurate drawings of the brain. The Latin and Greek names for structures in the CNS originate from this time, e.g. hippocampus = sea horse.

Question 3

Foundations of neuroscience: light microscope

Answer 3

By 1900 many of the microscopic features and connections of CNS cell groups were known.

Question 4

microscopic features were studies by:

Answer 4

• Golgi method-silver stain- stains cell bodies and dendrites.
• Nissl staining- labels cell bodies (why?)
• Myelin staining- myelinated axons
The 6 layers of the human cerebral cortex were determined by these methods.

Question 5

connections were studied by:

Answer 5

cutting axons which form tracts and allowing them or their cells of origin to degenerate.
• Cell bodies degenerate- retrograde degeneration
• Axons degenerate- anterograde degeneration

Question 6

foundations of neuroscience: electron microscope

Answer 6

During the 1950s EM methods were developed to examine CNS tissue. Subcellular elements of neurons could be investigated for the fist time, e.g. synapses.

Question 7

foundations of neuroscience: lesion studies

Answer 7

There are two types of lesion study:
1. Observe functional disturbances following experimental lesions in animals.
2. Relate disorders in man to lesions of the CNS e.g. language areas of the brain
However this type of approach is crude. Lesions are seldom specific and compensation may occur.

Question 8

foundations of neuroscience: electrical stimulation

Answer 8

Electrical stimulation has often been applied to tracts or nuclei of the CNS; e.g. stimulation of the motor cortex results in contraction of muscles on the opposite side of the body.
• This method showed that the body is represented by ‘maps’ in sensory and motor
regions of the Cortex - these are sometimes called the Homunculus
• However this approach is limited and reveals nothing about the complex
connections of the CNS