Tracking Brain Plasticity in Cochlear Implant Patients Using the Event-Related Optical Signal (EROS)

Chun-Yu TSE PhD

Department of Psychology

The Chinese University of Hong Kong (CUHK)

Introduction

• Hearing ability deteriorates with age

– Loss of hair cells in the cochlea diminishes the transduction of auditory signals

• Cochlear implants by-pass the transduction process by stimulating the auditory nerve

– Induce changes in the auditory cortex

Cochlear Implant

© Mayo Foundation for Medical Education and Research

External component

Internal component

Monitoring of Brain Plasticity in Cochlear Implant Patients

• MRI

– Safety issue

• EEG/ERP

– with artifact correction methods (e.g., ICA; Gilley et al., 2006; Debener et al., 2008; Viola et al.,

2011)

Aim

• Using the Event-related Optical Signal (EROS), an imaging method without interference from electrical stimulation, to track brain plasticity in cochlear implant patients prior to and after the implantation

Intrinsic Optical Signals

Fast optical signal Neuronal signal

Event-related Optical Signal (EROS)

Time 0

40-80ms

Stimulus presented

Intrinsic Optical Signals

Fast optical signal Neuronal signal

Event-related Optical Signal (EROS)

Time 0

40-80ms

Stimulus presented

Active Rest

More light scattering Less light scattering

Intrinsic Optical Signals

Fast optical signal Neuronal signal

Event-related Optical Signal (EROS)

Time 0

40-80ms

Stimulus presented

Slow optical signal Hemodynamic signal

Near Infra-Red Spectroscopy (NIRS)

Oxygen

Deoxy Hb Oxy Hb 0.5-4sec 2-12sec

Active Rest

More light scattering Less light scattering

Intrinsic Optical Signals

Fast optical signal Neuronal signal

Event-related Optical Signal (EROS)

Time 0

Deoxy Hb Oxy Hb 0.5-4sec 2-12sec 40-80ms

EROS and NIRS can be measured simultaneously

Stimulus presented

Slow optical signal Hemodynamic signal

Near Infra-Red Spectroscopy (NIRS)

(Huettel, Song, & McCarthy, 2009)

Non-invasive Functional Brain Imaging Methods

EEG, MEG

fMRI

Temporal localization

Spatial localization

Millisecond (High)

Second (Low)

Event-Related Optical Signal (EROS)

Millimeter (High)

Centimeter (Low)

NIRS

Recording Optical Signals

Source Optical Fiber (e.g., 830nm)

Detector Optical Fiber

The “banana

-shaped” path

followed by light

that reaches the

detector.

Scattering in the Brain

Locating Optical Signals

Detector

Source

Recording Optical Signals

Recording System Recording Montage

Source Fibers

Detector Fibers Optical Imaging Machine

Methods

• Six cochlear implant patients with profound hearing loss in the high frequency range (>1000 Hz )

– onset after 45 years of age

• Three brain imaging (EROS and EEG/ERP) sessions

– pre-surgery

– 1-month post-surgery

– 6-months post-surgery

Low Frequency Auditory Block (LA): Tones with frequency within the audible range

High Frequency Auditory Block (HA): Tones with frequency above the audible range of individual patients prior to implant

Task: Classifying the long and short tones by button press

100ms (80%)

50ms (20%)

Methods

Active Oddball Paradigm

Results - All Participants

Behavioral Results

d’ (

Z Sc

ore

)

1 2 30

1

2

3

4

5

Pre-implant 1 Month 6 Months

Low Frequency High Frequency

Low Frequency High Frequency

1 2 30

1

2

3

4

5

1 2 30

1

2

3

4

5

Slow Recovery

Fast Recovery

Pre-implant 1 Month 6 Months

Behavioral Results - Individual Participants

Low Frequency

Pre-implant 1 Month 6 Months

High Frequency

1 2 30

1

2

3

4

5

Pre-implant 1 Month 6 Months

Both Frequencies

d’ (

Z Sc

ore

)

Each colored line represents reponses of one participants

Single Subject – Fast Recovery d

’ (Z

Sco

re)

Behavioral Results

Correct-standard

Incorrect-standard

Miss-standard

Correct-deviant

Incorrect-deviant

Miss-deviant

Pre-implant 1 Month Post-implant 6 Months Post-implant

Low Frequency

High Frequency

ERP Results - Pz (µV)

1 2 30

1

2

3

4

5

1 2 30

1

2

3

4

5

Pre-implant 1 Month 6 Months

Low Frequency High Frequency

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

(ms)

Single Subject – Slow Recovery d

’ (Z

Sco

re)

Behavioral Results

Pre-implant 1 Month Post-implant 6 Months Post-implant

Low Frequency

High Frequency

ERP Results - Pz

(ms)

Low Frequency High Frequency

1 2 30

1

2

3

4

5

1 2 30

1

2

3

4

5

(µV)

Pre-implant 1 Month 6 Months

Low Frequency High Frequency

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

0 500 1000

-10

0

10

20

Correct-standard

Incorrect-standard

Miss-standard

Correct-deviant

Incorrect-deviant

Miss-deviant

Summary

• The results revealed a correspondence between EROS/ERP and the behavioral response

• This study demonstrated

• the possibility of applying EROS to monitor the reorganization of brain responses associated with recovery of hearing ability

• optical imaging is useful for recoding brain signals during electrical stimulation

Acknowledgments

University of Illinois at Urbana-Champaign

• Monica Fabiani

• Gabriele Gratton

• Ed Maclin

• Chin-Hong Tan

• Benjamin Zimmerman

Carle Foundation Hospital

• Michael A. Novak

• Jennifer Black

Washington University in St. Louis

• Brian A. Gordon

Funding supports

• Beckman Institute, University of Illinois at Urbana-Champaign

• The Carle Foundation

Questions and Answers

Tracking Brain Plasticity in Cochlear Implant Patients Using the Event-Related Optical Signal (EROS)

Chun-Yu TSE PhD

Department of Psychology

The Chinese University of Hong Kong (CUHK)

Recording Optical Signals