Global Brain Activity Flashcards
1
Q
What is EEG?
A
- An electroencephalogram (EEG) is a recording of brain activity.
- Used clinically to study physiology of sleep and epilepy
2
Q
- An electroencephalogram (EEG) is a recording of brain activity.
- Used clinically to study physiology of … and also …
A
- An electroencephalogram (EEG) is a recording of brain activity.
- Used clinically to study physiology of sleep and epilepy
- Non invasive - children and adults
- Electrodes applied - standard positions - study activity of neurons - good temporal resolution
- Poor spatial resolution - cant tell a signal apart if too close
- Surface of cerebral cortex mainly
- Electrodes named depending on location on scalp
3
Q
Generation of small fields in pyramidal cells
- It takes many thousands of underlying neurons, activated together, to generate an … signal big enough to see at all.
A
- It takes many thousands of underlying neurons, activated together, to generate an EEG signal big enough to see at all.
4
Q
The Electroencephalogram (EEG)
- Basic requirements for signal detection:
- A whole population of neurons must be active in … to generate a large enough electrical field at the level of the scalp
- This population of neurons must be aligned in a … orientation so that they can summate rather than cancel out.
A
- Basic requirements for signal detection:
- 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 can summate rather than cancel out.
5
Q
The Electroencephalogram (EEG)
- Basic requirements for signal detection:
- A whole population of … 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 can … rather than cancel out.
A
- Basic requirements for signal detection:
- 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 can summate rather than cancel out.
6
Q
Synchronous activity
- The amplitude of the EEG signal partly depends on how … the activity of the underlying neurons is.
- Number of active cells, total amount of …, timing of activity.
A
- The amplitude of the EEG signal partly depends on how synchronous the activity of the underlying neurons is.
- Number of active cells, total amount of excitation, timing of activity.
7
Q
EEG / brain rhythms correlate with pathology & behavioural states
- Left - EEG during … … - higher amplitude signal along all electrodes - large signal starts at ends at same time
- Right - … EEG - based on whether they are awake with eyes closed - left, or awake with eyes open - right
- … sleep - beta rhythms - dreaming and mental activity
- Non … - deep stage - higher amplitude signal
A
- Left - EEG during epileptic seizure - higher amplitude signal along all electrodes - large signal starts at ends at same time
- Right - normal EEG - based on whether they are awake with eyes closed - left, or awake with eyes open - right
- REM sleep - beta rhythms - dreaming and mental activity
- Non Rem - deep stage - higher amplitude signal
8
Q
Generation of synchronous rhythms
- 2 mechanisms:
- … neuron - gives pace
- OR … - interact dynamically
- Right picture - thalamus sends specific signals out - rhythm inputs towards cortex - large network of cells fire same frequency - synchronous activity
A
- 2 mechanisms:
- Pacemaker neuron - gives pace
- OR improvisation - interact dynamically
- Right picture - thalamus sends specific signals out - rhythm inputs towards cortex - large network of cells fire same frequency - synchronous activity
- Generated - pacemaker cells in thalamus
9
Q
Generation of synchronous rhythms
- A one neuron oscillator
- … cells have a set of voltage-gated ion channels that allow each cell to generate rhythmic, self-sustaining discharge patterns, even in the absence of external inputs.
- The rhythmic activity of each … pacemaker neuron then becomes synchronised with many other … cells via a hand-clapping kind of collective interaction
A
- A one neuron oscillator
- Thalamic cells have a set of voltage-gated ion channels that allow each cell to generate rhythmic, self-sustaining discharge patterns, even in the absence of external inputs.
- The rhythmic activity of each thalamic pacemaker neuron then becomes synchronised with many other thalamic cells via a hand-clapping kind of collective interaction
10
Q
Functions of Brain Rhythms?
- Theories:
- Sensory input – thalamus – cortex
- Activity … (binding) of different cortical regions (synchrony, oscillations)
- OR
- … by-product of feedback circuits and connections
- Overall - … rhythms give us a window of the functional states of the brain
A
- Sensory input – thalamus – cortex
- Activity coordination (binding) of different cortical regions (synchrony, oscillations
- Meaningless by-product of feedback circuits and connections
- Overall - EEG rhythms give us a window of the functional states of the brain
11
Q
Sleep: behavioural criteria
- … motor activity
- … response to stimulation
- Stereotypic …
- Relatively easy …
- About 1/… of life sleeping
A
- Reduced motor activity
- Decreased response to stimulation
- Stereotypic postures
- Relatively easy reversibility
- About 1/3 of life sleeping
12
Q
Sleep: behavioural criteria
- Reduced … activity
- Decreased response to …
- … postures
- Relatively … reversibility
- About 1/… of life sleeping
A
- Reduced motor activity
- Decreased response to stimulation
- Stereotypic postures
- Relatively easy reversibility
- About 1/3 of life sleeping
13
Q
Three functional states of sleep
- 3 functional states:
- … - low amplitude signal, high frequency
- …-… - 4 stages
- Stage 1 - move and change posture but brain largely not connected to environment, thalamic activity dominates cortical activity
- Stage 2 onwards – more synchronous - More deep sleep - more dominated by thalamic inputs
- Stage 3 and 4 – … rhythms
- … – active hallucinating brain, paralysed body (lucid dream) exception of breathing muscles and some small muscles and eyes
A
- 3 functional states:
- Awake - low amplitude signal, high frequency
-
Non-REM - 4 stages
- Stage 1 - move and change posture but brain largely not connected to environment, thalamic activity dominates cortical activity
- Stage 2 onwards – more synchronous - More deep sleep - more dominated by thalamic inputs
- Stage 3 and 4 – delta rhythms
- REM – rapid eye movement - active hallucinating brain, paralysed body (lucid dream) exception of breathing muscles and some small muscles and eyes
14
Q
Three functional states of sleep
- 3 functional states: these are…
A
- 3 functional states:
- Awake - low amplitude signal, high frequency
-
Non-REM - 4 stages
- Stage 1 - move and change posture but brain largely not connected to environment, thalamic activity dominates cortical activity
- Stage 2 onwards – more synchronous - More deep sleep - more dominated by thalamic inputs
- Stage 3 and 4 – delta rhythms
- REM – rapid eye movement - active hallucinating brain, paralysed body (lucid dream) exception of breathing muscles and some small muscles and eyes
15
Q
Summary scheme of sleep-wake states
A
22
Q
Sequence of events in the acquisition of an MRI scan
A
24
Q
PET image
A
measures change of blood flow to a region
25
Q
fMRI
A
- sensitive to the concentration of oxygen in the blood
28
Q
- … signal: blood oxygen-level-dependent contrast, is the signal measured in fMRI that relates to the concentration of oxy- and deoxyhaemoglobin in the blood.
- HRF - Haemodynamic response function, describes the changes of the … signal over time
A
- BOLD signal: blood oxygen-level-dependent contrast, is the signal measured in fMRI that relates to the concentration of oxy- and deoxyhaemoglobin in the blood.
- HRF - Haemodynamic response function, describes the changes of the BOLD signal over time
30
Q
Spatial and temporal resolution
A
