© Ane Venter
Chapter 5
States of Consciousness
1
,© Ane Venter
The Nature of Consciousness
1. Variations in levels of awareness
2. The evolutionary roots of consciousness
3. Consciousness and brain activity
→ Consciousness: the awareness of internal and external stimuli
○ Includes:
Your awareness of external events
Your awareness of internal sensation
Your awareness of yourself as the unique being having these experiences
Your awareness of your thoughts about these experiences
○ It is a personal awareness
○ Consciousness is constantly moving and flowing – William James called it the Stream of
Consciousness
1. Variations in Levels of Awareness
→ According to Freud = steam of consciousness has depth – what goes on in the unconscious
→ Conscious and unconscious processes have different levels of awareness
→ Freud – one of the first theorists to recognise the consciousness is not an all-or-none phenomenon
→ People continue to maintain some awareness during sleep and anaesthesia
○ Some stimuli can still penetrate awareness
Some patients can later repeat thing the surgeon said
While people are asleep – can still register external events to some degree
Selective sensitivity to sound = some mental processes during sleep must exist
2. The Evolutionary Roots of Consciousness
→ Plenty of debate about exactly how consciousness proved to be adaptive
→ Thought that consciousness helped our ancestors to think through courses of action + their
consequences
→ Little empirical evidence to judge merits of theories
3. Consciousness and Brain Activity
→ Consciousness does not arise from any distinct structure in the brain
○ Activity in distributed networks of neural pathways
→ EEG most commonly used to record brain activity (electroencephalograph)
○ Device that monitors the electrical activity of the brain – recording electrodes attached to the scalp
○ Summarised the rhythm of cortical activity in the brain in terms of line tracings (brainwaves)
○ Tracings vary in amplitude and frequency
2
, © Ane Venter
Brain wave activity based on usually divided into 4
bands based on frequency of the brain waves:
Beta (13-24 cps) β
Normal waking thought, alert problem solving
Alpha (8-12 cps) α
Deep relaxation, blank mind, meditation
Theta (4-7 cps) θ
Light sleep
Delta (under 4 cps) Δ
Deep sleep
→ Different patterns of EEG activity = associated with different states of consciousness
Biological Rhythms and Sleep
1. The role of circadian rhythms
2. Ignoring circadian rhythms
→ Variations in consciousness – shaped in part by biological rhythms
→ Biological Rhythms: periodic fluctuations in physiological functioning
○ Organisms have “internal clocks” = monitor passage of time somehow
1. The Role of Circadian Rhythms
→ Circadian rhythms: the 24-hour biological cycles found in humans and many other species
→ In humans – circadian rhythms particularly influential in regulation of sleep
→ Daily cycles also produce rhythmic variations in:
○ Blood pressure
○ Urine production
○ Hormonal secretions
○ Other physical functions
→ Cycles also affect alertness, short-term memory, and other aspects of cognitive performance
3
Chapter 5
States of Consciousness
1
,© Ane Venter
The Nature of Consciousness
1. Variations in levels of awareness
2. The evolutionary roots of consciousness
3. Consciousness and brain activity
→ Consciousness: the awareness of internal and external stimuli
○ Includes:
Your awareness of external events
Your awareness of internal sensation
Your awareness of yourself as the unique being having these experiences
Your awareness of your thoughts about these experiences
○ It is a personal awareness
○ Consciousness is constantly moving and flowing – William James called it the Stream of
Consciousness
1. Variations in Levels of Awareness
→ According to Freud = steam of consciousness has depth – what goes on in the unconscious
→ Conscious and unconscious processes have different levels of awareness
→ Freud – one of the first theorists to recognise the consciousness is not an all-or-none phenomenon
→ People continue to maintain some awareness during sleep and anaesthesia
○ Some stimuli can still penetrate awareness
Some patients can later repeat thing the surgeon said
While people are asleep – can still register external events to some degree
Selective sensitivity to sound = some mental processes during sleep must exist
2. The Evolutionary Roots of Consciousness
→ Plenty of debate about exactly how consciousness proved to be adaptive
→ Thought that consciousness helped our ancestors to think through courses of action + their
consequences
→ Little empirical evidence to judge merits of theories
3. Consciousness and Brain Activity
→ Consciousness does not arise from any distinct structure in the brain
○ Activity in distributed networks of neural pathways
→ EEG most commonly used to record brain activity (electroencephalograph)
○ Device that monitors the electrical activity of the brain – recording electrodes attached to the scalp
○ Summarised the rhythm of cortical activity in the brain in terms of line tracings (brainwaves)
○ Tracings vary in amplitude and frequency
2
, © Ane Venter
Brain wave activity based on usually divided into 4
bands based on frequency of the brain waves:
Beta (13-24 cps) β
Normal waking thought, alert problem solving
Alpha (8-12 cps) α
Deep relaxation, blank mind, meditation
Theta (4-7 cps) θ
Light sleep
Delta (under 4 cps) Δ
Deep sleep
→ Different patterns of EEG activity = associated with different states of consciousness
Biological Rhythms and Sleep
1. The role of circadian rhythms
2. Ignoring circadian rhythms
→ Variations in consciousness – shaped in part by biological rhythms
→ Biological Rhythms: periodic fluctuations in physiological functioning
○ Organisms have “internal clocks” = monitor passage of time somehow
1. The Role of Circadian Rhythms
→ Circadian rhythms: the 24-hour biological cycles found in humans and many other species
→ In humans – circadian rhythms particularly influential in regulation of sleep
→ Daily cycles also produce rhythmic variations in:
○ Blood pressure
○ Urine production
○ Hormonal secretions
○ Other physical functions
→ Cycles also affect alertness, short-term memory, and other aspects of cognitive performance
3
