Biological Psychology Flashcards
Electro-encephalogram (EEG)
measures brain activity
many electrodes placed on the scalp
signals are a summation of the activity of many neurons close to the electrode
synchronised activity = large deflections
Hertz (Hz)
measure of how many times something happens in 1 second
Why is there EEG wave classification?
Exact frequencies of the waves are not consistent so they are grouped into different classes which represent the different states in sleep
beta waves classification
13-30 Hz
alpha waves frequency
8-13 Hz
theta waves frequency
3.5-7.5 Hz
delta waves frequency
<4 Hz
REM sleep
brain is very active - theta and beta activity
Rapid Eye Movements
loss of muscle tone: paralysis
clear, narrative dreams
(also called paradoxical sleep)
what are the effects of sleep deprivation?
compensate by more sleep later (mostly slow wave sleep and REM sleep)
no effect on ability to exercise
clear effect on concentration and cognitive abilities
clear effect on emotional control
evolutionary theory of sleep
sleep to conserve energy during the least productive parts of the day
for example humans sleep at night
some species like ducks can sleep one hemisphere at a time to keep a look out for predators
brain recovery theory of sleep
which is specifically to explain slow wave sleep
the idea that metabolic breakdown products are cleared during slow wave sleep
so it is the resting and recovery of the brain
memory consolidation theory sleep
the idea that the brain needs to do two mutually-exclusive functions so sleep is needed to be able to store memories for the longer term
this is not possible during wakefulness as the brain needs to be aware of its environment at all times so can’t also process memories
REM on brain area
Sublaterodorsal Nucleus (SLD) in dorsal pons
REM off brain area
Ventrolateral Peri-aqueductal Gray matter (vlPAG) in midbrain
what is the fastest classification of brain waves?
beta
what is the slowest classification of brain waves?
delta
which stages of sleep are delta waves seen most in?
stage 3 and 4 (slow wave sleep)
which brain waves are seen in REM sleep?
theta and beta
what type of brain waves are seen in stage 1 sleep?
theta
what brain waves are most associated with being awake?
alpha and beta
what is a sleep spindle on an EEG?
is a distinctive pattern of brain activity that is observed on an electroencephalogram (EEG) during stage 2 of non-rapid eye movement (NREM) sleep. Sleep spindles are characterized by a burst of high-frequency (12-15 Hz) oscillations that last for a brief period of time (usually around 0.5-2 seconds)
what have sleep spindles been said to define?
being asleep
is there obvious large deflections on an EEG during REM sleep?
NO
what stage of sleep has obvious frequent deflections (where neurons are firing synchronously)?
stage 4
how does increase in temperature effect slow wave sleep?
it increases slow wave sleep that night if the brain temperature has been higher
- heat increases metabolism in the brain
- study with hair dryer showed more SWS after participants had had head warmed with hair dryer
is the brain affected by ‘mental exercise’?
yes, it increases slow wave sleep
what is a study that supports the brain recovery theory of sleep?
study in mice found during slow wave sleep the space between cells in the brain increases which helps the brain to metabolise things
according to the memory consolidation theory of sleep why is sleep needed?
in order to block out external stimuli so that the brain can focus on storing memories into LTM
what is REM sleep required for according to the memory consolidation theory of sleep?
the consolidation of procedural memories and/or emotional memories
what is slow wave sleep required for according to the memory consolidation theory of sleep?
consolidation of explicit (consciously recalled - factual and experience based) memories
support for the memory consolidation theory of sleep
- there is more REM sleep during early development (when infants are learning how to do a new of things)
study example that supports the purpose of REM according to the memory consolidation theory?
people performed a visual discrimination task (procedural) and then they found:
- people that did not sleep got worse
- people that slept but no REM sleep stayed the same
- people that got REM sleep improved
study example that supports the purpose of slow wave sleep according to the memory consolidation theory?
They let some people go to sleep and half of the people stayed awake, none got to REM sleep, they found:
- people got better in the word pair task after having SWS (semantic memory)
- but that they did not get better in the mirror drawing task (supports it is not needed for procedural memory)
what is the activation-synthesis hypothesis (Hobson)?
suggests that dreams are a by-product of REM sleep as they brain is replaying things that have happened so it is your consciousness interpreting them
why do we forget dreams?
some parts of the brain are suppressed during REM sleep
for example the inferior frontal cortex which is involved in memory
people who have damage in this area of the brain have reported life feeling like a dream
if you see glutamate what should be assumed?
excitation
if you see GABA what should be assumed?
inhibition
what neurotransmitters are in the monoamine category?
- dopamine
- epinephrine
- norepinephrine
- serotonin
what class of neurotransmitter are glutamate, aspartate, glycine and GABA?
amino acids
how do hormones travel in the body?
through the bloodstream
how do neurotransmitters travel?
from one neuron to the next
can individual neurons fire spontaneously?
yes
dorsal
top
ventral
bottom
rostral
front
caudal
back
telencephalon
all of the cortex
mesencephalon
tectum and tegmentum
metencephalon
cerebellum and pons
diencephalon
thalamus and hypothalamus
myelencephalon
medulla
what is the brainstem reticular formation
dozens of nuclei running through the medulla, pons and tegmentum with lots of different groups of neurons
where is the Reticular Activating System (RAS)?
in the Brainstem Reticular Formation
what is the Reticular Activating System?
part of the brain that keeps us awake and alert
what are the 5 different neurotransmitter systems in the brain involved in the sleep-wake cycle?
acetylcholinergic
noradrenergic
serotonergic
histaminergic
hypocretinergic
levels of acetylcholine during sleep and waking?
- high in the neocortex during waking
- high during REM
- low during slow-wave sleep
what neurotransmitters are in high levels in the brain during REM sleep?
acetylcholine
are noradrenaline and norepinephrine the same thing?
yes
where is noradrenaline released from?
locus coeruleus
(in RAS in Pons)
why is noradrenaline released?
usually due to external stimuli, makes us pay attention
(cocaine, amphetamines)
where is serotonin released from?
Raphe Nucleus
(RAS in Pons and Medulla)
is serotonin sensitive to external stimuli?
no
how to the levels of serotonin fluctuate in the sleep-wake cycle?
- high when awake
- decreases until very low in REM sleep
- spikes as soon as you come out of REM sleep
what does serotonin do?
influences locomotion and cortical arousal
which two neurotransmitters are incompatible with REM sleep?
noradrenaline and serotonin
both must be very low
where is histamine released from?
in the tuberomammillary nucleus (in the hypothalamus)
how to the levels of histamine fluctuate in the sleep-wake cycle?
-high during waking
-low during sleep
why do anti-histamines put you to sleep?
if these drugs get into the brain it will interfere with the histamine from the tuberomammillary nucleus (TMN) which keeps you awake
what is another name for hypocretin?
orexin
what does hypocretin do?
responds strongly to whether you are hungry or not
used by many excitatory neurons as their neurotransmitter
all things that are only active when we are awake
how do the levels of hypocretin fluctuate in the sleep-wake cycle?
- active during active waking and exploration
where is hypocretin released from?
group of neurons in the lateral hypothalamus and has a lot of other excitatory hypocretinergic connections
which brain areas are involved in arousal/ keeping us awake?
- reticular formation
- locus coeruleus (noradrenaline)
- raphe nucleus (serotonin)
- pons (acetylcholine; serotonin)
- hypothalamus (histamine; hypocretin)
- basal forebrain (acetylcholine)
which area of the brain actively controls sleep?
ventrolateral preoptic area (vlPOA)
where is the vlPOA ?
hypothalamus
what is the vlPOA crucial for?
sleep induction
what does the vlPOA connect to?
- different brain areas that keep us awake and alert
- through GABA-ergic (inhibitory) synapses
What is the flip flop for sleep induction?
- when the flip flop is on the vlPOA is actively inhibited
- because the brain stem and forebrain arousal systems are active (awake)
- when the flip flop is off the brain stem and forebrain arousal systems are inhibited so
- the vlPOA is active (sleep)
What 3 things is the sleep-wake flip flop influenced by?
- homeostatic control
- allosteric control
- circadian control
What is an example of homeostatic control of sleep?
Adenosine
What is adenosine (in relation to sleep)?
Adenosine is produced by astrocytes (provide energy to neurons) when they use up their glycogen stores
- increased levels of adenosine cause more delta activity during slow wave sleep
- adenosine has inhibitory effects on neurons
explanations for why adenosine induces sleep?
- adenosine accumulation inhibits the basal forebrain neurons so when they stop firing it takes away the inhibition from the vlPOA, so the flip-flop will eventually flip
- the adenosine directly inhibits the lateral hypothalamus, then if the lateral hypothalamus is inhibited a lot of the other wakeful brain areas will be inhibited
how does a G/A genotype differ to a G/G genotype?
G/A genotype individuals clear adenosine more slowly
- so they need around 30 minutes more slow wave sleep
how does a G/A genotype differ to a G/G genotype?
G/A genotype individuals clear adenosine more slowly
- so they need around 30 minutes more slow wave sleep
what does the allostatic control of sleep refer to?
response to threats to promote wakefulness
hypocretin
responds to hunger - a lot released when hungry
how does hunger influence sleep? (allostatic control of sleep):
hypocretinergic neurons are inhibited by leptin, a hormone which signals full fat reserves
- so more fat reserves = less sleep-wake cycle will try to keep you awake as you are not in danger of starving
hypocretinergic neurons are stimulated by ghrelin, a hormone signalling an empty stomach
- if you an empty stomach, more likely to stay awake
- wakeful areas are stimulated, vlPOA is inhibited, making it harder to fall asleep
which areas of the stress response stimulate parts of the arousal system?
- sensory stimulation activates hypocretinergic and noradrenergic neurons
- medial prefrontal cortex has excitatory synapses on these neurons, this brain area is more active when we’re stressed
describe what is meant by the circadian control of sleep
- we sleep better at night than during the day
- sleep-wake cycles continue without access to day-night information