Chapter 4: The Mind and Consciousness
Consciousness = the subjective experience of the world and of mental activity.
Qualia = the properties of our subjective experiences, such as our perceptions of
Split brain = a condition in which the corpus callosum is surgically cut and the two
hemispheres of the brain do not receive information directly from each other.
Interpreter = a left hemisphere process that attempts to make sense of events.
Subliminal perception = information processed without conscious awareness;
stimuli get processed by sensory systems but, because of their short duration or
subtle forms, do not reach consciousness.
Verbal overshadowing = the performance impairment that occurs when people try
to explain verbally their perceptual experiences that are not easy to describe.
Blindsight = a condition in which people who are blind have some spared visual
capacities in the absence of any visual awareness.
E.g. a 52-year-old African physician living in Switzerland who had become blind
following two consecutive strokes was shown a series of faces. A brain scanner
shows that his amygdala became activated with emotional faces, but not with faces
showing neutral faces.
Global workspace model = consciousness arises as a function of which brain circuits
are active; you experience your brain region’s output as conscious awareness. No
single area of the brain is responsible for general “awareness”. Rather, different
areas of the brain deal with different types of information, and each of these systems
in turn is responsible for conscious awareness of its type of information.
A hemineglect patient is not aware of missing part of the visual world. The patients’
unawareness of their visual deficits supports the idea that consciousness arises
through the brain processes active at any point in time.
The relationship between consciousness and neural responses in the brain
Hypothesis: specific patterns of brain activity can predict what a person is seeing.
1) Participants were shown images with houses superimposed on faces.
2) Participants were asked to report whether they saw a house or a face.
3) Researchers used fMRI to measure neural responses in participants’ brains. Results: Activity increased in the fusiform face area when participants reported
seeing a face, but temporal cortex regions associated with object recognition
became active when participants reported seeing a house.
Conclusion: Type of awareness is related to which brain region processes the
particular sensory information.
Awake: beta waves
Relaxing: alpha waves
Stage 1: theta waves – you can be aroused easily; light sleep; fantastical images or
geometric shapes; falling sensation or jerking limbs.
Stage 2: theta waves – breathing becomes more regular; become less sensitive to
external stimulation; occasional bursts of brain activity called sleep spindles and
large waves called k-complexes.
Stages 3 and 4: delta waves – slow-wave sleep; very hard to wake.
REM sleep (aka paradoxical sleep): After about 90 minutes, the sleep cycle reverses.
At this point, the EEG shows a flurry of beta wave activity, usually indicating an
awake, alert mind. The eyes dart back and forth rapidly behind closed eyelids. Some
neurons, such as the occipital cortex and brain stem regions, are more active during
REM sleep than awake hours. Most of the body’s muscles are paralyzed. The body
shows signs of genital arousal. Dreams occur. Cerebral blood flow to prefrontal
cortex and the posterior cingulate decreases. Cerebral blood flow to the basal
forebrain, anterior cingulate and visual association areas increases.
- Insomnia – inability to sleep
- Pseudoinsomnia – they dream that they are not sleeping
- Sleep apnea – a person stops breathing while asleep
- Narcolepsy – people fall asleep during normal waking hours.
- REM behavior disorder – normal paralysis that usually accompanies REM
sleep is disabled so that people act out their dreams while sleeping
- Somnambulism – sleep walking
Three general explanations for sleep’s adaptiveness:
2) Circadian cycles
3) Facilitation of learning
1) Restorative theory >> Sleep allows the brain and body to rest and to repair themselves.
- Released during deep sleep, growth hormone facilitates the repair of
- After engaging in vigorous physical activity, people generally sleep longer
- Sleep apparently allows the brain to replenish glycogen stores and
strengthens the immune system
Microsleep = brief, unintended sleep episodes, ranging from a few seconds to a
minute, caused by chronic sleep deprivation.
Sleep deprivation may help people to overcome depression; sleep deprivation leads
to increased activation of serotonin receptors.
2) Circadian rhythm theory
>> Proposes that sleep has evolved to keep animals quiet and inactive during times
of the day when there is greatest danger, usually when it is dark.
Circadian rhythm = the regulation of biological cycles into regular patterns.
E.g. body temperature, hormone levels and sleep/wake cycles
Humans depend greatly on vision for survival, and they adapted to sleeping at night
because the lack of light increased the dangers around them.
3) Facilitation of Learning
Scientists have proposed that sleep is important because it is involved in the
strengthening of neural connections that serve as the basis of learning.
Circuits wired together during waking hours are consolidated or strengthened
Students deprived of sleep for one night showed reduced activity in the
hippocampus, the area used for memory.
Regulation of Sleep
Multiple neural mechanisms are involved introducing and maintaining circadian
rhythms and sleep.
The pineal gland, a tiny structure in the brain, secretes melatonin, a hormone that
travels through the bloodstream and affects various receptors in both the body and
the brain. Bright lights suppress the production of melatonin and vice versa. Taking melatonin
helps people to fall asleep, although it is unclear why.
A gene called sleepless regulates a protein that reduces action potentials in the
brain. Loss of protein leads to an 80% reduction in sleep.
Sleep is controlled by brain mechanisms that produce alterations in states of
Stimulating the reticular formation in the brain stem leads to increased arousal in
the cerebral cortex. If you cut the fibres from the reticular formation to the cortex,
animals fall asleep and stay asleep until they die.
Low levels of activity in the reticular formation produce sleep, and high levels lead
Evidence suggests that the basal forebrain, a small area just in front of the
hypothalamus, is involved in producing non-REM sleep. Neurons in this area
become more active during non-REM sleep, and any lesion in the area will lead to
insomnia. Once activated, the region sends inhibitory signals to the reticular
formation, thereby reducing arousal and triggering sleep.
>> The products of an altered state of consciousness in which images and fantasies
are confused with reality.
REM dreams: bizarre, involving intense emotions, visual and auditory
hallucinations, illegal contents, and uncritical acceptance of events – resulting from
activation of visual association areas
Non-REM dreams: very dull, about mundane activities such as deciding what clothes
to wear or taking notes in class.
According to Sigmund Freud:
- Manifest content = the plot of a dream; the way a dream is remembered
- Latent content = what a dream symbolizes, or the material that is disguised in a
dream to protect the dreamer.
>> A theory proposed by Alan Hobson in the 1980’s, of dreaming