Interrogating the Nervous System

Question 1

Fluid will be ________ in a T2-weighted MRI.

Answer 1

white

Question 2

Describe the physics of PET scanning.

Answer 2

Patients are given radioactive water intravenously. The water sends out a positron when the additional neutron decays. The positron impacts with an electron and sends out two photons in diametrically opposed directions. The capture of those photons, and the time difference between their impacts, can tell you where a water molecule was.

Question 3

What is the resolution of PET and CT scanning of the brain?

Answer 3

2-3 mm squared

Question 4

There are two main categories of scanning the living brain: ________________.

Answer 4

electrophysiologic (electroencephalogram and magnetoencephalogram) and metabolic (PET, MRI)

Question 5

The cerebral cortex is a layer of gray matter consisting of __________ sheets of cells.

Answer 5

six

Question 6

The summation of electrical signals in the cerebral cortex occurs mostly at _________ cells.

Answer 6

pyramidal

Question 7

Describe the layout of pyramidal cells in relation to the six layers of the cerebral cortex.

Answer 7

The dendrites are usually near the surface – around layer 1 – while the soma is deeper – around layer 5 or 6.

Question 8

It is important to note that EEG and MEG sense ____________.

Answer 8

populations of partially synchronized neurons – not individual neurons

Question 9

What are event-related potentials?

Answer 9

ERPs are EEG signals for repeated stimuli. For instance, if you and I listen to an auditory click and we are wearing EEG monitors, then we will display similar wave patterns over the auditory cortex.

Question 10

What is the basis of diffusion tensor imaging?

Answer 10

MRIs sense the Brownian movement of water. Water is impeded by lipid (such as would be found around white matter tracts) and so the movement of water molecules can illustrate the tracts of the deep brain – the connectome.