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PSYCH 261 (107)
Chapter 9

Chapter 9 - Sleep.pdf

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Britt Anderson

Chapter 9Sleep and Biological Rhythms A Physiological and Behavioural Description of SleepSleep is behaviour it is not distinguished by movement Stages of Sleepbest research on human sleep is conducted in a sleep laboratorySleep laboratory experimenter prepares the sleeper for electrophysiological measurements by attaching electrodes to the scalp to monitor the electroencephalogram EEG and to the chin to monitor muscle activity recorded as the Electromyogram EMG Electromyogram EMGAn electrical potential recorded from an electrode placed on or in a muscle Electrooculogram EOGAn electrical potential from the eyes recorded by means of electrodes placed on the skin around them detects eye movementDuring the wakefulness the EEG of a normal person shows two basic patterns of activity alpha activity and beta activityAlpha activitySmooth electrical activity of 812 Hz recorded from the brain generally associated with a state of relaxation When person is not excited or aroused Although alpha waves sometimes occur when a persons eyes are open they are much more prevalent when they are closed Beta activityIrregular electrical activity of 1330 Hz recorded from the brain generally associated with a state of arousal Beta activity shows desynchrony it reflects the fact that many different neural circuits in the brain are actively processing info Desynchronized activity occurs when a person is alert and attentive to events in the environment or is thinking actively Stages of Sleep Stage 1 Theta activity EEG activity of 3575 Hz that occurs intermittently during early stages of slow wave sleep and REM sleep indicates firing of neurons in the neocortex is becoming more synchronized this stage is a transition between sleep and wakefulnessStage 2 About 10 minutes later enter this sleep stage The EEG is generally irregular but contains periods of theta activity sleep spindles and KcomplexesSleep spindles are short bursts of waves of 1214 Hz that occur between 2 and 5 times a minute during stages 14 of sleepThey play role in memory and increased sleep spindles are correlated with increased scores on test of intelligenceK complexes sudden sharp waveforms which unlike sleep spindles are usually found only during stage 2 sleep At the rate of approx one per minute but often can be triggered by noisesespecially unexpected noisesK complexes appear to be the forerunner of delta waves which appear in the deepest levels of sleep Stage 3 Delta activity Regular synchronous electrical activity of less than 4 Hz recorded from the brain occurs during the deepest stages of slowwave sleep About 15 minutes later the subject enters stage of sleep signaled by the occurrence of highamplitudeThe distinction between stage 3 and 4 is not clearcut stage 3 contains 2050 delta activity and stage 4 contains more than 50 Slowwave sleep Stage 3 and 4 of NonREM sleep characterized by synchronized EEG activity during its deeper stagesThe most important feature of slowwave activity during sleep is slow oscillations of less than 1Hz Each oscillation consists of a single highamplitude biphasic wave of slightly less than 1HzFirst Part of the Wave down statea period of inhibition during a slow oscillation during slow wave sleep neurons in the neocortex are silent and resting Second Part of the Wave up state a period of excitation during a slow oscillation during slowwave sleep neurons in the neocortex briefly fire at a high rateEach oscillation consists of an inhibitory hyperpolarizing silent phase down state followed by an excitatory depolarizing phase during which the neuron fires at a high rate up state45 minutes after the onset of Stage 4 sleep we notice an abrupt change in number of physiological measures recorded from our subject The EEG suddenly becomes mostly desynchronized with a sprinkling of theta waves similar to Stage 1Eyes rapidly dart back and forth beneath closed eyelids Person actually becomes paralyzed during REM sleep REM Sleep A period of desynchronized EEG activity during sleep at which time dreaming rapid eye movements and muscular paralysis occur also called paradoxical sleepStage 4 is the deepest stage of sleep when awakened person acts confused During REM sleep a person might not react to noises but he or she is easily aroused by meaningful stimuli such as sound of his or her nameWhen awaked from REM sleep person appears alert or attentive During the rest of the night our subjects sleep alternates between periods of REM and nonREM Sleep NonREM sleep All stages of sleep except REM sleep Each cycle is about 90 minutes long contain about 2030 minute of REM sleep 8hour sleep will contain 45 periods of REM sleep
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