Polysomnography is the most accurate method of evaluating sleep, often referred to ask the “gold standard” of sleep research. PSG converts bodily electrical impulses into graphical representations of electroencephalography (EEG), which shows night-time brain waves, electroöculography (EOG), which shows eye movements, electromyography (EMG), which we use to measure muscle activity in the legs during sleep, electrocardiography (EKG) or heartbeat, and respiration (breathing). We use Vitaport TEMEC recorders, portable polysomnographic devices, to record these measures during sleep. While other laboratories record PSG in their lab's sleep facilities, these recordings may not be representative of typical sleep as subjects (especially children) must adapt to the unfamiliar laboratory environment. Using these portable devices, our lab is able to conduct overnight recordings in the home, giving our study more ecologically valid data. This mode of study also puts less of a burden on participants, whose daily routine is less interrupted than by in-lab recordings.
Actigraphy refers to the use of computerized wristwatch-like devices, Actiwatches, to monitor and collect activity data using a device called an “accelerometer”. Actigraphs allow sleep to be reliably recorded over an extended period of time. Actigraphy has been validated as a reliable method for recording sleep. Actigraphic sleep measures include sleep movement and fragmentation, amount of time spent awake during the night, amount of motionless sleep, sleep and wake times. Our actigraphic recordings are analyzed by sleep software which automatically calculates these measures. Along with standard actigraphy, our lab uses actiwatches which are able to detect light intensity during the day (Actiwatch-L) and caloric/energy expenditures due to physical activity (Actical).
Multiple Sleep Latency Test (MSLT)
The MSLT measures the time it takes for someone to fall asleep (sleep onset latency) under standard daytime napping conditions in order to evaluate alertness and sleepiness. On testing days, participants take several 20-minute naps at regular intervals. Using PSG, our sleep technicians record how long it takes for the participant to fall asleep. If the participant does not fall asleep after 20 minutes, the nap is be terminated and the sleep latency for that nap is be assigned a value of 20 minutes. If the participant falls asleep during the nap, they are allowed to sleep for 15 minutes whether or not REM sleep occurred. A shorter sleep latency period indicates a higher level of physiological sleepiness.
Stellate and Harmonie
These are computer programs used to score and analyze polysomnographically measured sleep. Using this software, our research assistants and sleep technicians are able to assign different sleep stages (Stage 1-4 and REM), look for potential breathing or heart problems, restless legs, and to detect and score sleep spindles. Several small programs written by local Montreal researchers and technicians allow us to easily convert PSG data into numbers in our databases, where we can easily analyze the data and make scientific statements about participants’ sleep habits and neurobehavioural function.