Toward a Taxonomy of Autonomic Sleep Patterns with Electrodermal Activity
Akane Sano and Rosalind W. Picard, Massachusetts Institute of Technology
Media LabAffective Computing Group
What is Electrodermal Activity?•Electrical measures of sweat gland activity
• Index of sympathetic nervous activation
•Classically, has been measured with wired and gelled electrodes on the skin
•Our research group developed a dry electrode, wearable sensor for long-term ambulatory measurement
Electrodermal Activity (EDA) during sleepQ:Sympathetic nervous activity goes up
during a day and goes down and get silent during sleep?
A: No!!!
High frequency “storm” patterns during sleep
Why these storm patterns happen?
Measurement of SleepPolysomnography (PSG)
+ measures EEG and more, provides 30 s epochs labeled as: Wake, NonREM (stage 1-3), and REM
- expensive and obtrusive
Actigraphy
+ less invasive than PSG, low cost
- only measures movement
Our EDA sensor
+ comfortable, same or lower cost than actigraphy
+ measures EDA, skin temperature and actigraphy
-+ measures different patterns than traditional
Objectives•Evaluate EDA sleep patterns
quantitatively from healthy groups
•Understand what the changing patterns of EDA mean in terms of traditional PSG.
ExperimentsCollected EDA+motion during sleep from healthy adults
Total: 168 nights
0
Mot
ion
1 2 3 4 5 6 7 8
SWS
N-REM2
N-REM1
REM
W
Time [hr]
Analysis: sleep vs. wakeSleep and wake are discriminated from accelerometer data with standard zero-crossing and Cole’s function
wake
Analysis: EDA storms during sleep• After low-pass filtering (0.4 Hz, 32nd order FIR filter), we detected
“storm” regions during sleep, regions of EDA with a burst of peaks
Storm epoch: > 3 peaks / 30-sec with the slope of each peak > 0.09 micro Siemens/s
Storm: Storm epochs that are adjacent or within 5 minutes of each other
Example: 6 storms in one night of sleep
*
* wake
EDA Storm
Raw EDA
0
1
2
3
ED
A [m
icro
Sie
men
s]
0
Mot
ion
0
2
4
6
# of
S
torm
Pea
ks
1 2 3 4 5 6 7 8
SWSN-REM2N-REM1
REMW
Time [hr]
EDA vs. sleep stages from PSG
EDA raw data
Motion data
EDA peaks
Sleep Stage
Wake is red
More than 90 % of EDA Storms occurred in SWS and NREM2 (N=7,
one night each) One subject had storms below the threshold
Portion of storm epochs in each category of sleep.
0 3 6 9 12 15 180
10
20
30
40
50
60
# of Storms
Fre
qu
en
cy
Histogram of # of storms over night (168 nights)
2/3 of nights had >= 1 storm 1/2 of nights had >= 2
storms
Summary• We analyzed electrodermal activity from healthy subjects
over 150 nights
• More than 90 % of EDA storms occurred in SWS and NREM2 (N=7, one night each)
• 2/3 of nights showed more than 1 EDA storm
1/2 of nights had more than 2 storms
Next Steps
• Needs more detail analysis with EEG and heart rates
• Are they related with sleep quality/ Sleep disorders
or Memory consolidation?