What are the methods for measuring electrical activity?
- Extracellular recording (1928)
- Intracellular voltage recoding with glass micro- electrodes (1949)
- Voltage clamp recording of currents (1952)
- Patch clamp (1976)
What are the different ways we can apply a tracer in electrophysiology?
- Pressure injection (tracer expelled by pressure from pipette)
- Iontophoresis (electrically charged tracers expelled from pipette)
- Insertion of dye crystals down concentration gradient
How are tracers distributed?
- Active transport in vesicles
- lateral diffusion within the cellular membrane
- viral transporters
What are the different directions of tracer movement?
Anterograde (cell body to axon terminal)
Retrograde (axon terminal to cell body)
How can we establish anatomical reorganizations of neuronal networks?
By combining both anterograde and retrograde movement.
How are viral tracers different to non viral tracers?
- Viral tracer signals are amplified rather than diluted.
Give an example of viruses binding to receptors on neurons
Rabies virus binds to cellular receptors via its external glycoprotein.
How does viral tracing work?
- Insert TVA and RVG (rabies virus glycoprotein) genes
- Apply pseudotypes virus containing EGFP and not RVG (enveleoped in EnvA protein)
- Only TVA’s containing RVG will be infected, allowing these cells to spread to pre-synaptic neurones.
What is TVA and what is it for?
It is the gene for receptors, so the virus can enter
What is RV-G and what is it for?
It is the gene for rabies virus glycoprotein, so the virus can spread to synaptically coupled cells
Listen to recording for slide 7
listen to recording for slide 7
What are the functions of the amygdala?
hormonalsecretion,
emotional responses, control of autonomic functions.
What are the functions of the hypothalamus?
- homeostasis
- hunger and thirst - regulation, heart rate (through regulation of the pituitary gland)
How can we demonstrate different types of cells respond different types of food even in the same brain region
- Single neurones stimulated in different brain areas in moving hungry rats
- During hunger/satiety, different pathways are activated to regulate homeostasis and weight
- These results show diff types of cells in the same region respond differently to food.
How can we study brain rhythms and the sleep cycle?
Using EEG
Give examples of functional imaging
PET (position emission tomography)
fMRI (Functional magnetic resonance imaging)
What is functional imaging
Techniques to measure changes in metabolism, blood flow, chemical composition and absorption during brain activity.
What is part of our brain’s rhythmic environment?
Temperature, day and night
What makes up our brain rhythms
- Sleep and waking
- Breathing cycles
- Walking
- Stages of night sleep.
What do EEG’s (Electroencephalography) measure?
Voltage changes in the cortex. Displays the difference in electrical potentials between two different sites on the head.
What are EEG’s used for?
- Diagnosis of disease such as epilepsy
- Diagnosis of conditions such as: Coma, encephalopathy, brain death
- Studies of sleep
What are the basic requirements for signal detection for EEG?
- A whole population of neurons must be active in synchrony to generate a large enough electrical field at the level of the scalp.
- This population of neurons must be aligned in a parallel orientation so that they summate rather than cancel out.
What is EPP?
A current that flows from extracellular to intracellular
What is IPP?
A current that flows from intracellular to extracellular
