Lecture 9 - neuronal oscillations Flashcards
What are neuronal oscillations?
the rhythmic or repetitive patterns of neural activity in the CNS
What is an MEG and what does it measure?
- magnetoencephalogram
- measures the magnetic field rather than electrical field
What does an MEG do in terms of temporal and spatial resolution?
keeps temporal resolution but improves spatial resolution
What type of oscillation frequency and amplitude is seen when there is active sensory processing, attention and memory active?
- low amplitude, high frequency
- small and fast
What type of oscillation frequency and amplitude is seen when there is inactive quiescence and sleep?
- high amplitude, low frequency
- big and slow
What are theta oscillations?
increased theta (4-8Hz) in the hippocampus
When do theta oscillations occur?
during goal-directed navigation but not during aimless movement.
What experiment/task showed the increased theta oscillations?
- MEG study with a virtual water maze task
- using a joystick to navigate to a hidden platform
What does the local field potential reflect?
the average behaviour of a large number of interacting neurons.
What channel responds to blue light (optogenetics)?
- ChR2 channel lets positive charge in, depolarising the cell.
What channel responds to yellow light (optogenetics)?
- NpHR halorhodopsin is a Cl- channel.
- Hyperpolarises the cell and stops it from firing.
How do basket cells produce rhythm?
-inhibitory
- fast spiking
- 200-300Hz
- identified by calcium binding protein parvalbumin
How does GABA inhibition produce rhythm?
- interneurons depolarised, coupled together = slow firing as one neuron inhibited by the other
- interneurons depolarised, not coupled together = fast firing
When is beta-gamma coupling increased in the entorhinal cortex-hippocampus?
during a learning task
How does the brain conduct and learn different tasks?
oscillations synchronising activity across regions and groups
Name 3 diseases that deficits in gamma activity is linked too.
- Alzheimer’s
- Schizophrenia
- Autism
Describe abnormal parvalbumin interneurons.
- Nav 1.1 is a sodium channel expressed on PV interneurons.
- Decreased Nav 1.1 expression suggests decreased PV interneurons.
What does restored Nav 1.1 function lead to?
- increased interneuron activity
- increased gamma activity
- increased memory function
- decreased hyper synchrony
What could indicate activity-dependent GABA dysfunction on an EEG?
decreased spontaneous IPSCs
What does stimulating the brain at gamma frequency activity do?
reduces the levels of beta amyloid pathology
re-sets the E-I balance and prevents disease progression
What are the stages of sleep?
- light sleep - stage 1 and 2
- slow wave sleep (SWS) - stage 3 and 4
- rapid eye movement sleep (REM) and non-REM
Describe the 2-phase consolidation period.
- during consolidation newly encoded memory traces are reactivated in the fast learning store.
- this drives the slow learning store.
- representations in the slow learning store are gradually strengthened.
What does boosting oscillations during sleep do?
potentiates declarative memory performance
