Week 6 Summary - Brain and Behaviour PDF

WEEK 6: Consciousness, sleep and dreams Objective 1: Describe the functions of consciousness and levels of conscious experience • • • Consciousness can be defined as awareness of your thoughts, actions, feelings, sensations, perceptions and other mental processes. This definition suggests that con...

WEEK 6: Consciousness, sleep and dreams Objective 1: Describe the functions of consciousness and levels of conscious experience • • • Consciousness can be defined as awareness of your thoughts, actions, feelings, sensations, perceptions and other mental processes. This definition suggests that consciousness is not itself a mental process but rather an aspect of many mental processes. For example, memories can be conscious, but consciousness is not just memory. However, we still don’t have a fully integrated theory, let alone a testable model, of conscious experience. Functions of consciousness: • Monitoring mental events: variations in quantity – that is, in the degree to which one is aware of mental events – result in different levels of consciousness. When you are alert and aware of your mental activity and of incoming sensations, you are fully conscious. At the same time, however, there is other mental activity taking place in your brain at varying ‘distances’ from your conscious awareness. These activities are occurring at other levels of consciousness. It is when your experience of yourself varies in focus and clarity – as when you sleep or are under the influence of a mindaltering drug – that there are variations in your state of consciousness. • Regulating thought and behaviour: one function of consciousness is to provide the best current interpretation of sensory information in light of past experience and to make this interpretation available to the parts of the brain that can act on it. Consciousness helps you engage in the most adaptive and efficient blending of your brain’s sensory input, motor responses and knowledge resources. Three levels of consciousness: 1. Conscious level - the level at which mental activities that people are normally aware of occur. 2. Non-conscious level – a level of mental activity that is inaccessible to conscious awareness. For example, you are not directly aware of your brain regulating your blood pressure. 3. Preconscious level - a level of mental activity that is not currently conscious but of which we can easily become conscious. For example, what did you have for dinner last night? The information you needed to answer this question was probably not at a conscious level, but it was at a preconscious level and ready to be brought into awareness. Objective 2: Describe how consciousness is assessed and analysed 1. Cognitive science or cognitive neuroscience - when advanced brain-imaging techniques began to appear in the latter part of the 20th century, psychologists had the tools necessary to explore the relationship between conscious experience and brain activity. Most cognitive psychologists who study memory, reasoning, problem solving and decision making can be described as studying various aspects of consciousness. 2. Dualism - sees the mind and brain as different. This idea was championed in the 1600s by the French philosopher René Descartes. Descartes claimed that a person’s soul, or consciousness, is separate from the brain but can ‘view’ and interact with brain events through a small brain structure called the pineal gland. Once a popular point of view, dualism has virtually disappeared from psychology. 3. Materialism - suggests that mind and brain are one and the same. Materialists argue that complex interactions among the brain’s nerve cells create consciousness, much as hardware and software interact to create the image that appears on a computer screen. A good deal of support for the materialist view comes from case studies in which damage to the brain causes disruptions in consciousness. 4. Theatre - consciousness is a single phenomenon, a kind of ‘stage’ on which all the various aspects of awareness converge to ‘perform’ before the ‘audience’ of your mind. Those adopting the theatre view see support for it in the fact that the same psychophysical laws govern our subjective experience of the intensity of light, sound, weight and other stimuli. It is as if each sensory system passes its information to a single ‘monitor’ that coordinates the experience of stimulus magnitude. 5. Parallel distributed processing (PDP) models - describe the mind as processing many parallel streams of information, whose interactions create the unitary experience we call consciousness. PDP models became influential when research on sensation, perception, memory, cognition and language suggested that components of these processes are analysed in separate brain regions. For example, our ability to perceive a visual scene requires the combined activity of many separate brain regions, some of which analyse what each object is, while others determine where it is. Scientists still do not know whether these parallel streams of information ever unite in a common brain region. Objective 3: Explain the core characteristics of the four stages of non-REM sleep and REM sleep Non-REM sleep: • • • • Stage 1—blood pressure drops, muscles relax and eye movements slow Stage 2—sleep deepens Stages 3 and 4—deep (delta wave) sleep Sleep stages 1, 2, 3 and 4 are accompanied by gradually slower and deeper breathing, a calm and regular heartbeat, reduced blood pressure and slower brain waves (Stages 3 and 4 are called slow-wave sleep). When you reach stage 4, it is quite difficult to wake up. If you were roused from this stage of deep sleep, you would be groggy and confused. Together, these four stages are called non-REM (NREM) sleep because they do not include the rapid eye movements (REM). • Most people pass through the cycle of sleep stages four to six times each night. Each cycle lasts about 90 minutes, but with a somewhat changing pattern of stages and stage duration. Early in the night, most of the time is spent in NREM sleep, with only a few minutes in REM sleep. As sleep continues, though, it is dominated by stage 2 and REM sleep, from which sleepers finally awaken. REM Sleep: • After 30 to 45 minutes in stage 4, you quickly return to stage 2 and then enter a special stage in which your eyes move rapidly beneath their eyelids. This is called rapid eye movement (REM) sleep, or paradoxical sleep. It is called paradoxical because its characteristics present a paradox, or contradiction. In REM sleep, your EEG resembles that of an awake, alert person, and your physiological arousal – heart rate, breathing and blood pressure – is also similar to when you are awake. However, your muscles are nearly paralysed. Sudden, twitchy spasms appear, especially in your face and hands, but your brain actively suppresses other movements. Objective 4: Define the two interacting processes that explain why people sleep Sleep as a circadian rhythm: • The sleep–wake cycle is one example of the rhythmic nature of life. In almost all animals, including humans, certain cycles of behaviour and physiology repeat about every 24 hours. These cyclical patterns are called circadian rhythms or human biological rhythms. • Circadian rhythm (human biological rhythm) are defined as a cycle, such as waking and sleeping, that repeats about once a day. Consolidation of memory and restoring bodily functions: • Some researchers suggest that sleep helps restore the body and the brain for future activity and helps consolidate memories of newly learned facts. In one study, people who were REM-deprived showed poorer retention of a skill learned the day before than people who were either deprived of non-REM sleep or allowed to sleep normally. Other studies have found that information, including emotional information, is remembered better and longer when followed immediately by sleep, especially REM sleep. • Memory consolidation, information processing, physical growth, muscle repair, and countless other processes are theorised to occur during sleep; sleep is also critical for strengthening the immune system and allowing the body to fight off disease. Objective 5: Evaluate the three main theories on why people dream 1. Psychodynamic view - asserts that dreams represent a window into the unconscious where latent content (meaning) can be inferred. According to Freud dreams are a disguised form of wish fulfilment, a way of satisfying unconscious urges or resolving unconscious conflicts that are too upsetting to deal with consciously. Sexual desires, for example, might appear in a dream as the rhythmic motions of a horseback ride. Conflicting feelings about a parent might appear as a dream about a fight. 2. Cognitive view - posits that dreams are constructed from the daily issues of the dreamer. Some researchers see dreaming as a process through which all mammals analyse and consolidate information that has personal significance or survival value. This view is supported by the fact that dreaming appears to occur in most mammals, as indicated by the appearance of REM sleep. For example, after researchers disabled the neurons that cause REM sleep paralysis, sleeping cats ran around and attacked, or seemed alarmed by, unseen objects, presumably the images from dreams. 3. Biological view - suggests that dreams represent the attempt by the cortex to interpret a random firing of neurons during sleep. The activation–synthesis theory describes dreams as the meaningless by-products of REM sleep. According to this theory, hindbrain arousal during REM sleep creates random messages that activate the brain, especially the cerebral cortex. Dreams result as the cortex combines, or synthesises, these random messages as best it can, using stored memories and current feelings to impose a coherent perceptual organisation on confusingly random inputs. From this perspective, dreams arise as the brain attempts to make sense of meaningless stimulation during sleep, much as it does during waking hours when trying to find meaningful shapes in cloud formations.