 Retrospective Questionnaires Sleep Logs/Sleep Diaries Observer Ratings  Response to External Stimuli Movement (Actigraphy) PolysomnographyAnderson Cooper gets his sleep studied Three core measures› Electroencephalogram (EEG)› Electrooculogram (EOG)› Electromyogram (EMG)TonicAtonic EEGs placed according to the 10-20 system:› C3 & C4: ideal for detecting frequency changes associated with sleep stages› Occipital sites: helpful in detecting transition from wake into sleep (alpha activity)› Additional sites used to detect regional EEG EOG› LOC: Left Outer Canthus; placed slightly below left eye› ROC: Right Outer Canthus; placed slightly above right eye› Allows for the detection of horizontal and vertical eye movements EMG› Three chin sites: allows for bipolar recording, with an electrode to spare› Additional EMG for research, clinical purposes (e.g. corrugator, tibialis) Data typically sampled at 200Hz, higher for specific research interests Filters:› Low frequency: 0.3Hz› High frequency: 70Hz› Additional high frequency filters can be applied to the EEG channels off-line Need lots of hard drive space! Data divided into epochs› Typically 30 seconds Each epoch assigned a sleep stage EEG: Alpha Activity (8-12 Hz) EOG› Little movement if closed, voluntary control if open EMG› Tonic activity, voluntary movement EEG› Slows down; Theta activity (4-8 Hz) EOG› Slow Eye Movements (SEMs) EMG› Tonic Activity Stages three and four EEG› Delta activity (0.5-3 Hz) EOG› N/A* EMG› Low level tonic activity EEG› Theta activity› Saw-tooth waves EOG› Rapid Eye Movements (REMs) EMG› Muscle Atonia 90 minute cycle Stage 1: <10% Stage 2: 50% SWS: 15-20% REM: 20-25%