Psychology AS Biological/Physiological Studies: Dement and Kleitman

Measuring sleep

• Brainwave activity can be measured by an EEG (electroencephalogram). This provides the summary of electrical activity in the brain
• Electrical activity of the muscle is measured by an EMG (electromyogram)
• Eye movement is recorded via an EOG (electro-oculogram)

Stages of Sleep

• Stage 1+2 Brain waves slow down, amplitude increases. This is very light sleep.
• Stage 3+4 Deeper sleep characterised by delta waves. Difficult to wake someone up.
• REM sleep - measured by EOG. Associated with dreaming. Fast brain pattern. 

• To discover if there is a link between REM sleep and dreaming.

• Nine adults, 7 males, 2 females. 5 studiede intensively.
• Experimental sessions were repeated many times.
• The pps reported to the sleep lab just before their usual bedtime. They had been told to eat normally but abstain from alcohol and caffine.
• Electrodes were attached around the pps eyes (EOG) and scalp (EEG). The participant then went to sleep in a quiet darkened room.
• At various time during the night pps were woken by a bell placed by their beds, These were done during REM or varying time periods after REM had stopped. On average they were woken 5.7 times a night.
• Used different patterns for the 5 pps to avoid unintentional pattter. With 2 pps they used a table of random numbers. 1 pp was awoken during 3 REM periods and then 3 NREM periods. One was told he would be awoken during REM, but was actually awoken randomly.
• None of the pps were told whether they had been having REM activity.
• Ths pps were instructed to speak into a recording machine near their bed stating a) whether they had been dreaming b) describing the content of the dream and c) whether they were dreaming for 5 or 15 minutes.
• An investigator was listening outside the room and occasionally entered the room to further question the participant.

• This is a lab experiment because it takes place in laboratory conditions - where extranoeous variables were controlled.

• The occurence of REM activity
• Eye movement periods and accuracy of dream recall
• Length of REM periods and subjective dream duration
• Eye movement patterns and visual imagery of the dream

• Whether the participant was awoken during REM or NREM sleep.

• All pps had REM every night and was accompanied with a fast EEG patterns
• Where REM activity was absent there were periods of deeper sleep
• No REM activity occured during the initial onset of sleep
• REM periods lasted between 3 and 50 minutes, with a mean of 20 minutes. The REM tended to be longer the later in the night it occured.
• REM occured at fairly regular intervals. The average was an REM episode every 92 minutes.
• If a pp was awoken during an REM period during the final hours of sleep, they often went back into REM sleep.
• For all pps there was a high incidence of recall of dreams during REM periods and a low incidence of recall during NREM regardless of pattern
• There were times when REM activity was not associated with a coherent dream and times when NREM did produce coherent dream recall.
• Some participants were better at recalling their dreams
• Most of the instances when dreams couldn't be recalled during REM occured in the early hours of the night
• The overwhelming majority of pps were accurate in estimating the length of their dream in relation to REM activity
• There appeared to be a positive link beween the type of eye movement and the content of the dream. One mainly horizontal dream recalled two people throwing tomatoes at each other. One mainly vertical dream recalled climbing ladders.
• Participant did not recall more dreams as the study went on, so they did not become 'practiced'

• Dreaming is accompanied by REM activity.
• It cannot be stated with complete certainty that dreaming cannot occur at other times
• An objective measurement of dreaming may be accomplished by recording REMs during sleep.