Cortical states

Question 1

What is a circadian rythm?

Answer 1

A 24 hour cycle that induces physical, mental, and behavioral changes.

Question 2

What are external cues that help your body form it’s circadian rythm?

Answer 2

Light and absence of light and daily routines such as meal times and social interaction.

Question 3

How is the cycle kept to 24 hours?

Answer 3

Our internal biological clock that works as homeostatic regulation with temperature and levels of hormones and operates even in the absence of external information.

Question 4

What part of the brain regulates these cyclical changes?

Answer 4

Hypothalamus.

Question 5

What is the pathway that allows light to regulate the circadian rhythm?

Answer 5

Absence of light -> Intrinsically photosensitive ganglion (melanopsin) stop being inhibited -> retinohypothalamic tract -> suprachiasmatic nucleus (master clock) -> Paraventricular nucleus -> spinal chord intermediolateral cells -> superior cervical ganglion -> Pineal gland –> synthesis of melatonin

Question 6

How does the cyrcadian affect learning and mood?

Answer 6

Light also signals directly to the thalamic perihabenular nucleus, which sends signals to N. Accumbens and medial Prefrontal Cortex which regulate mood.

Question 7

What is sleep behaviorally?

Answer 7

• reversible state of disengagement from and unresponsiveness to the outside environment
• postural recumbence, behavioral quiescence and closed eyes
• a normal suspension of consciousness

Question 8

What is sleep electrophysiologically?

Answer 8

Specific brain waves - specific patterns of electrical activity.

Question 9

Why do we sleep?

Answer 9

• To conserve energy by replenishing brain glycogen levels and decreasing the metabolism
• Sleep allows us to restore ourselves while it is dark and our primary sensory system (visual) is not very
  effective
• To consolidate memory as it has been shown that sleeping soon after learning increases recall and that
  sleep closes the gap between short term and long term memory stores
• To clear the brain of metabolic waste by an increase in the flow of cerebral spinal fluid.

Question 10

What are the 4 stages of sleep?

Answer 10

N1: - drowsiness/transition to sleep
- Waves start to have lower frequency and higher amplitude
N2: - Periodic bursts of activity of about 10-12 Hz that last 1-2 seconds and are called sleep spindles
- Even lower frequency and higher amplitude
N3: - Number of sleep spindles decreases
- slow-wave sleep
REM: - EEG similar to an awake state

Question 11

What are the physiological changes that happen in the N1 stage of sleep?

Answer 11

• low arousal threshold
• slow rolling eye movements
• the start of a decrease in muscle tone, body movements, heart rate, blood pressure, metabolic rate and temperature

Question 12

What are the physiological changes that occur in the N2 stage of sleep?

Answer 12

• more intense stimuli required to produce arousal
• stimuli that might have produced arousal in N1 now produce a sleep spindle
• the presence of K complexes
• progression of the decrease in muscle tone, body movements, heart rate, blood pressure, metabolic rate, and temperature

Question 13

What are the physiological changes present in stage n3 of sleep?

Answer 13

• Highest arousal threshold

- muscle tone, body movements, heart rate, blood pressure, metabolic rate, and temperature reach their lowest values

Question 14

What are the physiological changes present in the rem stage of sleep?

Answer 14

• rapid ballistic eye movement
• increase in muscle tone, body movements, heart rate, blood pressure, metabolic rate, and temperature
• pupillary constriction
• paralysis of large muscle groups and twitching of small muscle groups
• spontaneous penile erection
• greater prevalence of dreaming

Question 15

When do dreams occur?

Answer 15

Both in rem and non rem sleep,

Question 16

What is the difference between rem and non rem dreams?

Answer 16

Rem dreams tend to be longer, somewhat emotional, and disconected from the dreamers current life while non rem dreams tend to be shorter, less emotional and more conceptual and somewhat connected to the dreamers current life

Question 17

How does sleep change over the course of a life?

Answer 17

You need much less sleep as you get older with a marked drop in rem sleep in the transition out of infancy.

Question 18

What part of the brain when electrically stimulated causes wakefulness and arousal?

Answer 18

the midbrain pons junction

Question 19

What part of the brain when stimulated with what kind of electrical stimulation causes slow wave sleep?

Answer 19

Low frequency stimulation to the thalamus.

Question 20

What are 2 features of the neural circuits of sleep?

Answer 20

• A patterened interaction between the brainstem (reticular activating system), the thalamus and the cortex
• regulated by the hippocampus

Question 21

What is the REM Saccades circuit?

Answer 21

The pontine reticular formation (brainstem) signals to the superior colliulus which sends input to the paramedian pontine reticular formation which sends input to the rostral interstitial nucleus which generates eye movements

Question 22

What are the Pontine geniculate occipital (PGO) waves?

Answer 22

A phasic bursts of action potentials occur throughout the borebrain in association with rapid eye movements that are regulated by the pontine reticular formation.

Question 23

What is the circuit of the hyperpolarization of spinal cord motor neurons?

Answer 23

Pontine inhibitory area sends inhibitory inputs through the medulla to the spinal cord in order that we do not make large movements in our sleep.

Question 24

What is the reticular activation system?

Answer 24

A group of nuclei in the brainstem that operate with distinct neurotransmitters that project to thalamocortical neurons. Responsible for activating the cortex.

Question 25

What are the nuclei in the reticular activation system?

Answer 25

Chinergic nuclei, locus coeruleus, and the raphe nulei.

Question 26

What is the cholinergic nuclei?

Answer 26

• Part of the reticular activation system
• Houses choinergic neurons
• Desyncronizes the EEG
• Regulates REM sleep

Question 27

What is the the locus coeruleus?

Answer 27

• Part of the reticular activation system
• Houses noradrenergic neurons
• Positively modulated by the tuberomillary nucleus of the hypothalamus when it recives histamine or when activated by the lateral hypothalamus when it has orexin

Question 28

what is the Raphe nuclei?

Answer 28

• Part of the reticular activation system
• Houses serotoninergic neurons
• Positively modulated by the tuberomillary nucleus of the hypothalamus when it recives histamine or when activated by the lateral hypothalamus when it has orexin

Question 29

Why do anti-histamines make you drowsy?

Answer 29

Becuase the locus coeruleus and raphe nuclei both rely on the tuberomamillar nucleus in order to activate which in turn is activated by histamine.

Question 30

What is the system that periodically inhibits your reticular activation system?

Answer 30

The ventrolateral preoptic (VPLO) nucleus of the hypothalamus. Inhibits both the tuberomamillar nucleus and the nuclei in the reticular activation system directly though GABA.

Question 31

How does acetylcholine affect the sleep cycle?

Answer 31

When levels of acetylcholine go up in the brain you enter into REM sleep and when it goes down you exit REM sleep.

Question 32

In what cortical regions does activity increase during sleep?

Answer 32

The amygdala, para hippocampus, pontine tegmentum, anterior cingulate cortex (lymbic system leading to high emotionality)

Question 33

In what cortical regions does activity decrease during sleep?

Answer 33

Dorsolateral prefrontal and posterior cingulate cotex (leading to inappropriate socail content)

Question 34

What does it mean for thalamocortical neurons to be tonically active?

Answer 34

• neurons are depolarized
• sensory input and encoding of peripheral stimuli
• wakefulness

Question 35

What does it mean for thalamocortical neurons to be in an intrinsic bursting state?

Answer 35

• neurons in a oscillatory state
• synchronised with the cortex
• disconnected from the outside world