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?