Global brain activity Flashcards
What are the four types of brain rythyms
Sleeping/waking
Breathing cycles
Steps of walking
Stages of night
What is an EEG?
Electroencephalogram: set of electrodes that sample activity of neurons in brain via generation of small fields in pyramidal cells
What are the 2 requirements for an EEG signal?
- whole population of neurons must be active in synchrony to generate large enough electrical field to detect.
- population of neurons must be aligned in parallel orientation so they summate not cancel out
What does the amplitude of the EEG signal depend on?
Synchrony of neuron activity and number of active cells.
What are the 2 ways in which synchronous rhythms can be generated?
- Main leader and other signals follow. pacemaker gives rhythm input.
- timing arises from collective behaviour of neurons themselves all reacting to incoming signals
How do thalamic cells assist when absence of external inputs?
Thalamic cells have set of voltage gated ion channels. Allow each cell to generate rhythmic self-sustaining discharge patterns in absence of external input. Rhythmic activity of each thalamic pacemaker neuron becomes synchronised with other thalamic cells
What are the behavioural criteria for sleep?
decreased motor activity
decreased response to stimulation
stereotypic postures
relatively easy reversability
What are some of the functions of sleep
Conversing metabolic energy
Cognition- to consolidate information
Thermoregulation
Neural maturation and mental health
What are the features of the Awake brain state?
increased frequency of waves with decreased amplitude.
alpha rhythm when eyes closed and beta rhythm when eyes open.
What are the features of the non-REM brain state
Deep sleep. Increased synchrony of brain rhythm. Delta waves. Dominated by thalamus
What are the features of the REM brain state
Rapid eye movements.
Active hallucinating brain, paralysed body. Dreaming with eyes moving but closed
Beta rhythms
How are neurotransmitters and the thalamus involved in sleep-wake states?
Modulatory neurotransmitter systems originate in brainstem
Brainstem controls firing of thalamus
Thalamus coordinates firing and activity in cerebral cortex that seems to create basic dimensions of sleep-awake states
Main neurotransmitters in awake vs sleep states are norepinephrine and serotonin
What does structural imaging measure?
Measures of spatial configuration of types of tissue in the brain
What does functional imaging measure?
Measures moment to moment variable characteristics of the brain that may be associated with changes in cognitive processing
What are the features of CT scans?
Based on amount of xray absorption of different tissues
Bone appears white as absorbs most
CSF appears black as absorbs least
Gives little detail
Used in clinical settings to diagnose tumours/haemorrhages
