PSYC2230: Chapter 3 PowerPoint
Physiological Mechanisms of Arousal [pg. 61 - 100]
Arousal Theory [pg. 62 - 65]
How does the organism become activated? Motivation may be viewed on a continuum of behavioural
activation. Continuum ranges from low levels of arousal (coma and sleep) to high levels of arousal.
Inverted U Function: behaviour most efficient at optimal level of arousal. Yerkes-Dodson Law: a
relationship between level of arousal and efficient performance.
Different tasks are related to arousal level and performance: higher arousal for simple, habitual tasks
and lower arousal for complex, cognitive tasks. Too much arousal reduces performance.
Emotion and motivation related to activation of nervous system. There are structures that come into
play in emotion and motivation:
o Separating the medulla from the spinal cord and organism goes through normal sleep-wake
cycle (encephale isole preparation).
o Separation of the colliculi from the brainstem the organism is deprived of crucial structures
(medulla, pons, and reticular activating system [RAS]) and organism sleeps constantly (cerveau
isole preparation)
Reticular Activating System: Nerve cells in central core of brain stem. Moruzzi and Magoun (1949)
stimulated RAS electrically. Changes in electrical activity of cortex were noted in EEG-brain wave
recordings.
o Synchronous-- Alpha wave activity related to a relaxed awake organism. High, slow waves.
o Desynchronous-- Beta wave activity related to alert, attentive, aroused organism. Low fast
waves. RAS receives sensory input from external sensory organs and internal organs and
muscles. Lindsley (1951) cut all structures around the RAS and sleep is preserved. He cut the
RAS and organism slept constantly. RAS sends fibres to the cortex. RAS arouses cortex. Cortex
can inhibit RAS activation.
Hebb’s Arousal Theory [pg. 65]
Sensory information serves two functions:
1. To provide information
a. A cue function
b. An arousal function; if cortex is not aroused cue function has no effect
2. Sensory stimuli sent to cortex and RAS. The stimulus effect at RAS level is to activate (“tone up”)
the cortex so that stimulus information coming from the thalamus can be processed.
Motivation for Hebb is activation of the cortex via the thalamus and RAS.
3. Cortex sends fibres down to RAS and stimulates it when internal and external stimulation is low.
4. Downstream connections from cortex to RAS may explain how thoughts, images, memories can
activate & motivate behaviour. While trying to sleep, if RAS is activated, it in turn activates the
cortex and sleep becomes difficult-- tossing and turning!
Psychophysiological Measures: Arousal Theory [pg. 67 - 68]
Measure arousal by monitoring activity of the central nervous system (CNS) and autonomic nervous
system (ANS)
, PSYC2230: Chapter 3 PowerPoint
1. Various types of arousal:
a. Behavioural as organism responds
b. Autonomic arousal by changes in bodily functioning (e.g. heart rate)
c. Cortical arousal by desynchronized, beta wave activity
2. Chemicals (e.g. atropine) produce EEG activity akin to sleep in cats & dogs, and yet animal responds
normally. And (e.g. physostigmine) produces EEG activity akin to being alert, yet animal behaves as
if drowsy. Thus, arousal is multidimensional and relies on feedback from body systems.
3. Correlation between hormones an emotion (e.g. adrenal hormone epinephrine may be related to
anger & aggression); changes in ANS activity related to disgust, anger, fear; universal facial
expressions by way of contraction of facial muscles serve as signals of emotional state.
Sleep [pg. 68 - 72]
An overpowering motive showing characteristics of motivated need state. A type of behaviour; ⅓ of
our lives spent in sleep.
1. Sleep deprivation for 48 hours leads to performance problems on complex tasks requiring attention
and cognitive processing. Sleep deprived organisms also show increased suggestibility.
2. Why sleep? It is adaptive, removing us from situations when we are least efficient.
a. Circadian rhythms on a 24-hour cycle and operate during sleep.
b. Animals who are pretty sleep less and predators sleep more.
c. Whales and some bird species have unihemispheric slow-wave sleep where one half of the
brain sleeps.
3. In humans, sleep decreases with age from 14 - 16 hours in infancy; 11 hours in 5-year-olds; 6 - 7 hours
by 20 years. Old individuals report more awakenings in the night and insomnia, shorter and more
fragmented sleep, go to sleep earlier, and break-up the 7-hour cycle into several shorter sleep periods.
Stages of Sleep [pg. 69 - 72]
Defined by electrical activity of the brain through 5 stages of sleep:
1. Alpha activity: Relaxed wakefulness occurs before Stage 1: irregular low amplitude waves for 10-15
minutes. It accounts for 5% of sleep.
2. Stage 2: Sleep spindles and K-Complexes: accounts for 50% of sleep.
3. Stage 3: Delta waves; large & slow: accounts for 6% of sleep.
4. Stage 4: Slow high-amplitude waves; accounts for 14% of sleep for 30-45 minutes.
5. Stage 5: A mix of theta, beta, & alpha waves. Muscle tone is low, and REM takes over when dreaming
occurs: accounts for 25% of sleep.
Sleep Stages 1 - 4 are NREM slow-wave sleep, and Stage 5 is correlated with dreaming
REM dreams are bizarre, emotionally loaded & lifelike, and thus there is:
o Inhibition of motor neurons and loss of muscle tone is best indication of REM/dream sleep.
REM occurs about once every 90 minutes. REM periods become longer throughout the night so
by morning REM sleep can be as long as an hour.
o Cortical activity in REM is similar to Stage 1 sleep with a mixture of theta and beta waves and
person is paralyzed even though cortical activity is as if the person is awake and this has been
called Paradoxical sleep. Newborns spend 70% of time in REM, and REM declines to about 30%
Physiological Mechanisms of Arousal [pg. 61 - 100]
Arousal Theory [pg. 62 - 65]
How does the organism become activated? Motivation may be viewed on a continuum of behavioural
activation. Continuum ranges from low levels of arousal (coma and sleep) to high levels of arousal.
Inverted U Function: behaviour most efficient at optimal level of arousal. Yerkes-Dodson Law: a
relationship between level of arousal and efficient performance.
Different tasks are related to arousal level and performance: higher arousal for simple, habitual tasks
and lower arousal for complex, cognitive tasks. Too much arousal reduces performance.
Emotion and motivation related to activation of nervous system. There are structures that come into
play in emotion and motivation:
o Separating the medulla from the spinal cord and organism goes through normal sleep-wake
cycle (encephale isole preparation).
o Separation of the colliculi from the brainstem the organism is deprived of crucial structures
(medulla, pons, and reticular activating system [RAS]) and organism sleeps constantly (cerveau
isole preparation)
Reticular Activating System: Nerve cells in central core of brain stem. Moruzzi and Magoun (1949)
stimulated RAS electrically. Changes in electrical activity of cortex were noted in EEG-brain wave
recordings.
o Synchronous-- Alpha wave activity related to a relaxed awake organism. High, slow waves.
o Desynchronous-- Beta wave activity related to alert, attentive, aroused organism. Low fast
waves. RAS receives sensory input from external sensory organs and internal organs and
muscles. Lindsley (1951) cut all structures around the RAS and sleep is preserved. He cut the
RAS and organism slept constantly. RAS sends fibres to the cortex. RAS arouses cortex. Cortex
can inhibit RAS activation.
Hebb’s Arousal Theory [pg. 65]
Sensory information serves two functions:
1. To provide information
a. A cue function
b. An arousal function; if cortex is not aroused cue function has no effect
2. Sensory stimuli sent to cortex and RAS. The stimulus effect at RAS level is to activate (“tone up”)
the cortex so that stimulus information coming from the thalamus can be processed.
Motivation for Hebb is activation of the cortex via the thalamus and RAS.
3. Cortex sends fibres down to RAS and stimulates it when internal and external stimulation is low.
4. Downstream connections from cortex to RAS may explain how thoughts, images, memories can
activate & motivate behaviour. While trying to sleep, if RAS is activated, it in turn activates the
cortex and sleep becomes difficult-- tossing and turning!
Psychophysiological Measures: Arousal Theory [pg. 67 - 68]
Measure arousal by monitoring activity of the central nervous system (CNS) and autonomic nervous
system (ANS)
, PSYC2230: Chapter 3 PowerPoint
1. Various types of arousal:
a. Behavioural as organism responds
b. Autonomic arousal by changes in bodily functioning (e.g. heart rate)
c. Cortical arousal by desynchronized, beta wave activity
2. Chemicals (e.g. atropine) produce EEG activity akin to sleep in cats & dogs, and yet animal responds
normally. And (e.g. physostigmine) produces EEG activity akin to being alert, yet animal behaves as
if drowsy. Thus, arousal is multidimensional and relies on feedback from body systems.
3. Correlation between hormones an emotion (e.g. adrenal hormone epinephrine may be related to
anger & aggression); changes in ANS activity related to disgust, anger, fear; universal facial
expressions by way of contraction of facial muscles serve as signals of emotional state.
Sleep [pg. 68 - 72]
An overpowering motive showing characteristics of motivated need state. A type of behaviour; ⅓ of
our lives spent in sleep.
1. Sleep deprivation for 48 hours leads to performance problems on complex tasks requiring attention
and cognitive processing. Sleep deprived organisms also show increased suggestibility.
2. Why sleep? It is adaptive, removing us from situations when we are least efficient.
a. Circadian rhythms on a 24-hour cycle and operate during sleep.
b. Animals who are pretty sleep less and predators sleep more.
c. Whales and some bird species have unihemispheric slow-wave sleep where one half of the
brain sleeps.
3. In humans, sleep decreases with age from 14 - 16 hours in infancy; 11 hours in 5-year-olds; 6 - 7 hours
by 20 years. Old individuals report more awakenings in the night and insomnia, shorter and more
fragmented sleep, go to sleep earlier, and break-up the 7-hour cycle into several shorter sleep periods.
Stages of Sleep [pg. 69 - 72]
Defined by electrical activity of the brain through 5 stages of sleep:
1. Alpha activity: Relaxed wakefulness occurs before Stage 1: irregular low amplitude waves for 10-15
minutes. It accounts for 5% of sleep.
2. Stage 2: Sleep spindles and K-Complexes: accounts for 50% of sleep.
3. Stage 3: Delta waves; large & slow: accounts for 6% of sleep.
4. Stage 4: Slow high-amplitude waves; accounts for 14% of sleep for 30-45 minutes.
5. Stage 5: A mix of theta, beta, & alpha waves. Muscle tone is low, and REM takes over when dreaming
occurs: accounts for 25% of sleep.
Sleep Stages 1 - 4 are NREM slow-wave sleep, and Stage 5 is correlated with dreaming
REM dreams are bizarre, emotionally loaded & lifelike, and thus there is:
o Inhibition of motor neurons and loss of muscle tone is best indication of REM/dream sleep.
REM occurs about once every 90 minutes. REM periods become longer throughout the night so
by morning REM sleep can be as long as an hour.
o Cortical activity in REM is similar to Stage 1 sleep with a mixture of theta and beta waves and
person is paralyzed even though cortical activity is as if the person is awake and this has been
called Paradoxical sleep. Newborns spend 70% of time in REM, and REM declines to about 30%
