Flashcards in interrogating the NS Deck (20):
The idea that inferences about an individual’s brain function could be made from an analysis of the prominences that could be seen and felt on the skull. Discredited now
method of correlating brain regions with behaviors
Positive vs negative symptoms of NS disease
Negative symptoms (i.e. weakness, loss of sensation) correspond to the loss of function after a lesion interrupts or destroys a particular pathway, while positive symptoms (i.e. seizures, involuntary movements, abnormal sensations, hallucinations) result from a ‘state of overfunction’.
1. Review the differences between an EPSP, IPSP, and an action potential.
1. excitatory postsynaptic potential (EPSP) is a temporary depolarization of postsynaptic membrane potential. EPSP increases probability of action potential. 2. Inhibitory postsynaptic potential (IPSP) makes a postsynaptic neuron less likely to generate an action potential. IPSP decreases probability of action potential. EPSP and IPSPs are spatially and temporally summated to generate the all or non AP.
2. Understand the "coupling" between electrophysiologic activity in the nervous system and CNS hemodynamics.
Astrocytes form a coupling between neurons and their blood supply, and they generate local increases in blood flow to regions of the nervous system that exhibit increased synaptic and other metabolic activity associated with neurotransmission.
3. List those techniques for evaluating "brain activity" that measure the electromagnetic properties of the nervous system.
EEG, Event related potential (ERP)/evoked potentials and magnetoencephalogram
4. List those techniques for evaluating "brain activity" that measure the hemodynamic properties of the nervous system.
Functional MRI , Positron Emission Tomography (PET), and Single Photon Emission Computed Tomography (SPECT)
Discuss the layers of brain and how they coordinate with function
Deepest layers (V-VI): large dendrites, sends outgoing info. Middle layers (III-IV): take incoming info. Outer layers (I-II): communicate with other nearby neurons
What does an EEG measure?
electrical potential fluctuations at the scalp surface produced mainly by the relatively slow postsynaptic potentials (EPSPs and IPSPs) induced in neurons of the cerebral cortex. Very little contribution from the comparatively brief action potention.
Where does summation of electrical potential changes occur in the cortex
At vertically oriented neurons,pyramidal cells. The dendrites of pyramidal neurons extend through nearly all layers of cortex, guiding the flow of currents generated by postsynaptic potentials through the entire thicknes of the cortex to the cell body in the deeper layers. The current generated can penetrate the skull where it is measured by EEG
Do EEG/MEG measure synchronized or individual neurons?
synchronized - field potentials
What are evoked potentials
aka event related potentials- The EEG recording obtained during a specific task, i.e. listening to a sound,
What is electromyography
This is a study conducted by placing needle or surface electrodes in skeletal muscle, and recording the membrane properties of muscle fibers. Performed in conjuction with nerve conduction studies
How does a PET work
Inject subject with tracer labeled with positron emitting radionuclide (15 H20). Radionuclide decays, positrons annihilate with electrons producing 2 photons traveling in opposite directions that are detected by detectors.
How is PET used to study regional cerebral blood flow and what is this method called?
PET taken at rest, then PET taken during activity/behavior of interest then the control PET is subtracted from the behavior PET. The difference represents cerebral blood flow changes associated with the behavior. This is called cognitive subtraction
Describe the uses of different radioisotopes for PET scans
15 H2O shows cerebral blood flow, 18-fluorodeoxyglucose shows glucose metabolism, 18-fluorodopa shows where dopa conversion to dopamine occurs
How does a functional MRI work?
Blood oxygen level dependent (BOLD) signal- Oxyhemoglobin is diamagnetic, and does not cause distortion in a magnetic field, while deoxyhemoglobin is paramagnetic, and it does distort magnetic fields.
What is diffusion weighted imaging
MRI technique that shows the diffusivity of water molecules, which are altered in some pathological conditions
What is diffusion weighted imaging used for?
Ischemia (most common), multiple sclerosis, trauma, brain tumors