Thalamus/EEG Flashcards
what is slow wave sleep
one of phases of sleep characterized by pattern of slow wave oscillation of the EEG at frequency called the delta wave (~3 Hz)
Absence epilepsy
type of epilepsy prevalent in kids. Child has sudden staring spells. Child will stop activity, stare briefly ( a few seconds) and then resume
Thalamic relay neurons
cells lin thalamus receiving input from sensory system and relay the information to cortex via excitatory glutamatergic synapses onto pyramidal cortical neurons with soma in layer IV of cortex
How do thalamic relay neurons act when person is awake
TR neurons receive little inhibitory input – membrane potential at ~-55 mV. Upon depolarization, they fire series of APs at high frequency
how do thalamic relay neurons act when person is asleep
when in slow wave phase, thalamic reticular neurons inhibit TR neurons by releasing GABA. Resting membrane potential ~-85 mV and fire bursts of APs riding on top of Ca spike. Ca spike happens with frequency of `3 Hz–same as delta freq for slow wave discharge in EEG
channel responsible for slow Ca spike
T type Ca channel. It doesn’t operate at depolarized resting potentials (i.e. -55 mV for awake state)– inactivated by depolarization. when hyperpolarized by action of thalamic reticular cells, inactivation gate opens and Ca channel generates Ca spikes at frequency of 3 Hz. Several fast APs ride on top of Ca spike
what happens when T type Ca channel hyperpolarizes
when hyperpolarized by action of thalamic reticular cells, inactivation gate opens and Ca channel generates Ca spikes at frequency of 3 Hz. Several fast APs ride on top of Ca spike. Since thalamic relay neuron’s axon connects to cortical pyramidal cell, burst of firing APs in TR cell elicits firing of cortical pyramidal cell at a delta frequency –elicits slow wave EEG recorded in slow wave sleep
how is thalamocrotical circuit activity regulated?
Regulated by axons ascending from brain stem from cholinergic, noradrenergic and serotonergic neurons. When sleeping, stimulation of cholinergic neurons in reticular activating system results in awakening of he animal and interruption of slow waves in EEG.
where are the cholinergic, noradrenergic, and serotonergic neurons coming from/what are they releasing
These are ascending to thalamus from brainstem.
Cholinergic- from reticular activating system releasing ACh
Noradrenergic– from locus coeruleus releasing noradrenaline in thalamus (in fight or flight)
Serotonergic neurons from raphe nuclei release serotonin
