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Chapter 4

Chapter 4 - the mind and consciousness.docx

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Dan Dolderman

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 things. 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. Research method: 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. Sleep 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. Sleep disorders: - 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: 1) Restoration 2) Circadian cycles 3) Facilitation of learning 1) Restorative theory >> Sleep allows the brain and body to rest and to repair themselves. Evidence: - Released during deep sleep, growth hormone facilitates the repair of damaged tissue - After engaging in vigorous physical activity, people generally sleep longer than usual - 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 during sleep. 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 arousal. 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 to awakening. 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. Dreams >> 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. Activation-synthesis hypothesis >> A theory proposed by Alan Hobson in the 1980’s, of dreaming
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