toward a taxonomy of autonomic sleep patterns with electrodermal activity akane sano and rosalind w....
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Toward a Taxonomy of Autonomic Sleep Patterns with Electrodermal Activity
Akane Sano and Rosalind W. Picard, Massachusetts Institute of Technology
Media LabAffective Computing Group
akanes@mit.edu
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?
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