Biopsychology Exam 2 9 25 9 30 10 2 10 7 Why do we sleep Recuperation Theories of Sleep needed for our bodies to function properly Restoration Theory we sleep to repair and regenerate the body necessary for optimal function of physiological systems o During sleep there is an increase in growth hormone released by the pituitary gland It promotes muscle growth tissue repair and protein synthesis o Chronic sleep depravation can cause anxiety depression fatigue changes in attention and memory weakened immune system Elimination Theory rid the body and brain of excess sensory information shed things that are not important or necessary to strengthen things that are important o Certain synaptic connections are strengthened and others are weakened or not established during sleep Adaptation Circadian Theories of Sleep sleep in general is something that developed or evolved based on time of day survival necessities and became a pattern of behavior not something critical for the brain or body Immobilization Theory sleep is an innate response with species very specific pattern of sleep within species Keeps one inactive and safe during least efficient part of the light dark cycle Energy Conservation Theory following periods of survival activities hunting gathering preparing food periods of inactivity are a good way to conserve energy o In order to conserve energy there needs to be periods of sleep Information Consolidation Theory purpose of sleep is to enable formation of memories and consolidation of information there is increased neuronal activity during REM following enriched or novel experience in a person s life o Dreams may be evidence of cortical activation o More activity in the hippocampus during both non REM and REM sleep hippocampus is critical for information processing and memory formation o REM sleep nondeclarative memory consolidation memory for tasks behaviors motor skills things you can t necessarily talk about o SWS slow wave sleep non REM sleep declarative memory consolidation information you can talk about or declare facts dates information 3 Physiological Measures of Arousal Sleep Electroencephalogram EEG electrical potential recorded from larger electrodes placed on the scalp brain waves can indicate what stage of sleep someone is in Electrooculogram EOG measure eye movements during sleep SWS rolling eye movements REM rapid eye movements left right Electromyogram EMG electrical potential recorded from an electrode placed on muscle usually face and neck because it s easily accessible during sleep Measure changes in muscle tensions activity particularly in facial and neck muscles Level of atonia loss of muscle tone that happens during sleep it happens gradually as you fall asleep and then you lose all muscle tone during REM sleep Mentalis muscle between lower lip and chin seems to indicate sleep onset it loses its muscle tone as soon as you fall asleep Theories of Sleep Passive or Active Passive theory of sleep Bremer s Passive theory of sleep 1936 proposed that sleep was passive and occurred because lack of sensory input stopped the brain from being stimulated lack of motion noise sight ect o Experimented on cats to determine mechanisms involved in sleep severed their brains to study it cerveau isole isolated forebrain found that the sleep wake pattern in the cats changed dramatically and they tended to sleep all the time in continuous SWS encephale isole separating the entire brain at the spinal cord he saw the sleep wake cycle didn t change and cats slept at a normal cycle even though they were paralyzed o Bremer still held onto idea that sleep was passive and that taking out most of the sensory input will cause sleep Active theory of sleep Moruzzi and Magoun 1949 identified a group of neurons in the pons called the reticular activating system part of the reticular formation that is the ascending pathway from the pons to the cortex o The ascending pathway was severed in Bremer s experiment without the reticular activating system the cat slept all the time o Determined that sleep is a very active process you are not unconscious or inactive the brain is extremely active to keep you in sleep Sleep Wake Cycle REM sleep Emergent Stage 1 sleep We spend less and less time in deep stages of sleep over the course of the night most stage 3 4 sleep occurs early in the night The longer you sleep the longer your periods of REM sleep get and the more frequently they occur A typical cycle of sleep is all of the possible stages of sleep and one o Early in the night it s stages 1 4 and a period of REM about 90 o Later in the night a complete cycle may just include stage 2 and Alert wakefulness most people wake at some point through out the night During wakefulness there are two types of patterns that are likely o Fully awake alert and actively thinking beta wave Beta waves tend to be somewhat irregular low amplitude height up to about 30 microvolts and high frequency usually 13 30 Hz o Relaxed stage inactive drowsy just before sleep alpha wave Alpha wave activity increases as your brain shuts down before sleep also during meditation or day dreaming period of REM minutes REM going to occur Low amplitude but higher than beta waves 10 20 microvolts frequency 8 12 Hz Stage 1 the transitional stage of sleep initial stage 1 is when you re moving in and out of wakefulness and emergent stage 1 is REM sleep We spend very little time in stage 1 it s a way to get to other stages only 5 of our sleep time 1 7 minutes each time you re in stage 1 Theta waves higher amplitude waves that are of a mixed frequency o Amplitude up to 50 microvolts frequency of 4 7 Hz Very easy to wake from this stage if you wake from stage 1 perception is that you haven t slept at all Stage 2 slightly deeper sleep spend increasingly more time in stage 2 as the night goes on stay in stage 2 anywhere from 10 25 minutes at a time 45 of sleep time is in stage 2 sleep Primary wave activity is also theta waves Two unique characteristics of stage 2 sleep waves o Sleep spindles very short bursts of waves that have a very low amplitude and high frequency we experience 2 5 sleep spindles per minute throughout stage 2 o K complexes larger amplitude waves with low frequency we experience about 1 per minute o Outside stimulation or changes in physical muscle tension outside sound muscle twitches your cat steps on you etc causes sleep spindles and k complexes these are mechanisms that prevent us from wakening by reducing cortical