Effects of Unilateral Hearing Loss: From the Brain to Behavior Jill B. Firszt, Ph.D. Professor; Director, Cochlear Implant Program
Ruth Symposium, Harrisonburg, VA, October 9, 2015
Disclosures • Financial: — Employed by WUSM—salary — NIH (research funds) — Cochlear Americas, Advanced Bionics (consulting relationship and audiology advisory board member, research funds)
— Honorarium from JMU for 2015 Ruth Symposium
• Nonfinancial: —Serve as treasurer for the American CI Alliance (ACIA)
Overview of Presentation • •
Case study Unilateral hearing loss (UHL)
— Hemispheric activation patterns — Study in Adults with UHL—No CI — Study in Children with UHL—No CI — Study of effects of unilateral input and mode of hearing from the listener perspective
Individual Subject (S11) •
Hearing history
– Mumps age 7 yrs, profound HL (LE) – Acoustic neuroma age 47, profound HL (RE) – 1 mo later, CI in LE, the ear without direct peripheral stimulation for 40 years
Word and Sentence Recognition In Quiet
100% 90%
Percent Correct
80% 70% 60% CUNY Q HINT Q CNCW
50% 40% 30% 20% 10% 0% S07
S01
S03
S06
S10
S05
S02
S11
S09
S08
S04
Subjects Word and Sentence Recognition In Noise
100%
CUNY N HINT N SPIN
90% Percent Correct
80% 70% 60% 50% 40% 30% 20% 10% 0% S07
S01
S03
S06
S10
S05 Subjects
S02
S11
S09
S08
S04
Firszt et al, 2002
EABR El #1 100% of DR All subjects
Firszt et al, 2002
EMLR El #1 100% of DR All subjects
Firszt et al, 2002
El N1‐P2 El #1 100% of DR All subjects
Firszt et al, 2002
Individual Subject (S11) •
Did having sound in one ear help to maintain the opposite ear for a good outcome?
•
Was having hearing in both ears until age 7 and establishing binaural pathways the main reason?
Introduction • Sound stimulation is necessary for normal • •
development and function of the central auditory system (CAS) Hearing loss affects the representation of sound to the CAS Consequences of hearing loss depend on whether the loss is:
– Bilateral or unilateral – Total (profound) or partial
Normal Auditory System •
Is characterized by hemispheric asymmetry
– Acoustic stimulation in one ear produces activation that is stronger in the contralateral compared to ipsilateral hemisphere (Wolpaw & Henry 1977; Shtyrov et al., 1999; Khosla et al., 2003; Loveless et al., 1994; Sheffler et al., 1998; Jancke et al., 2002)
–Even with bilateral stimulation, activation is still asymmetric, with greater activation in the left hemisphere
Normal Hearing Acoustic stimulation in each ear produces • Stronger contralateral activation (darker colors) • Weaker ipsilateral activation cochlear nucleus (lighter colors)
Auditory Cortex
medial geniculate body
medial geniculate body
inferior colliculus
inferior colliculus
superior olive
superior olive
cochlear nucleus
But What is the Functional Significance of Hemispheric Asymmetry •
Association between clinical disorders and atypical hemispheric dominance
– Children with learning problems (Mattson et al 1992) – Individuals with language impairment, including dyslexia (Leonard et al 1993; Galaburda et al., 1994) – Continued need for investigation of functional significance of asymmetries
Animal Studies: Bilateral HL vs UHL
•
Some animal studies have shown that (Silverman & Clopton, 1977; Clopton & Silverman 1977)
– With bilateral auditory deprivation • the projections between ears (or sides) maintain •
balance, although activity was reduced less effect on binaural interactions
– With monaural auditory deprivation • loss of balance in neural activity • binaural interactions were altered • effect was greater than bilateral deprivation
Symmetric HL Acoustic stimulation produces
• Reduced overall activation • Asymmetric balance remains —Stronger contralateral —Weaker ipsilateral
cochlear nucleus
Auditory Cortex
medial geniculate body
medial geniculate body
inferior colliculus
inferior colliculus
superior olive
superior olive
cochlear nucleus
Unilateral HL Acoustic stimulation produces • Loss of balance • Altered binaural interactions • Stronger ipsilateral cochlear nucleus
Auditory Cortex
medial geniculate body
medial geniculate body
inferior colliculus
inferior colliculus
superior olive
superior olive
cochlear nucleus
Human Studies: NH vs UHL •
Some human studies have shown that:
• When the intact ear (good ear) is evoked by sounds, hemispheric activation patterns differ in UHL compared to normal hearing (NH)
• Using MEG (Vasama et al, 1994; 1995; 1997) • Using EEG (Hanss et al, 2009; Khosla et al 2003; Ponton et al, 2001)
• Using fMRI (Burton et al, 2012; Scheffler et al, 1998)
Activation lateralization in human core, belt and parabelt auditory fields with unilateral deafness compared to normal hearing Harold Burton, Jill Firszt, Tim Holden, Alvin Agato, Rosalie Uchanski Brain Research, 2012, 1454; 33‐47
Methods Acoustic stimulus
EPI
Silent Event Related Design
Delayed BOLD response
Amaro, E., Jr., Barker, G.J. 2006. Study design in fMRI: basic principles. Brain Cogn 60: 220-232.
% MR Signal Change
Response time courses for spectral + temporal RSS trials
UHL Ipsi vs. Contra
NH Ipsi vs. Contra
-48,-30,8, A1 (BA42)
-48,-30,8, A1 (BA42)
1.0
1.0
0.5
0.5
0.0
Ipsil Contra
Stim Delay (s)
2
3
4
5
6
7
8
9
0.0
2
3
4
5
6
7
8
9
p=0.34
p=0.002
Ipsi = Contra in 11/11 Foci
Ipsi < Contra in 6/11 Foci
Burton et al, 2012
Ipsilateral RE stimulation
Contralateral
LE stimulation
RE stimulation
LE stimulation
Te1.0
UHL NH
*
1.0
*
*
0.5
Te1.0 , Te 1.1 Core, primary auditory regions
0.0
Te1.1
Average % Change in BOLD Response
1.0
*
*
0.5
0.0
Te2 1.0
*
*
Te2 , Te3, parts of Core A1, caudel belt, lateral belt regions
0.5
0.0
Te3
*
1.0
0.5
0.0
STG/STS 0.8
*
0.6
*
*
STG/STS, Lateral belt, parabelt regions
*
0.4 0.2 0.0
2
3
4
5
6
7
8
9
2
3
4
5
6
7
8
9
2
3
4
5
6
Stimulus-EPI Delay (sec)
7
8
9
2
3
4
5
6
7
8
9
Burton et al, 2012
Using fmri in UHL and NH
•
Summary of findings
– UHL RE stimulation (left ear deafness), ipsilateral
•
responses larger compared to NH in core and belt regions – UHL LE stimulation (right ear deafness), only posterior core showed larger ipsilateral responses In agreement with Khosla et al 2003 (EEG) and Hanss et al 2009 (EEG) , greater differences for left ear deafness vs right ear deafness
UHL
•
Unilateral hearing loss induces CAS reorganization in ways that are different from bilateral hearing loss
– What does this mean for patients? – What are the behavioral effects? – How are they quantified?
Studies underway at WUSM/SLCH We are studying several patient populations with varied asymmetry between ears • All have one deaf ear • All are unilateral listeners 250
500
1000
2000
4000
8000
250
0
0
20
20
500
1000
2000
40
8000
250
500
1000
2000
4000
8000
C
C
C
C
C C C
0
A
A
A
A
20
A 40
4000
A
40
A A
60
60
80
80
80
100
100
100
Normal or Near-normal hearing
Some hearing loss Uses amplification
60
Severe to profound HL Uses cochlear implant
Unilateral Hearing Loss (UHL) Study in Adults Purpose:
• • • •
Quantify auditory deficits in adults with UHL Identify sources of variability in outcomes Compare results with NH bilateral listeners Compare results with NH unilateral listeners – Introduce the condition of UHL for NH listeners that have not adapted to UHL
UHL Study Participants • Adults with UHL Tested with one NH ear
• NH matches for each UHL participant (age and gender) –
One NH match tested with one ear (other ear plugged & muffed) •
–
NH‐Plugged
One NH match tested with both ears •
NH‐Bilateral
250
500
Frequency (Hz) 1K 2K
4K
8K
O O O
O
-10 0 10
O O
O
X X
X
20
Hearing Level (dB )
–
125
30 40 50 60 70 80 90
100 110 120
X X X X
X
UHL Study – Demographics Mean (SD) Range
UHL (n=26)
NH - Plugged (n=25)
NH - Bilateral (n=23)
Age (years)
49.1 (12.9) 25 - 71
48.8 (13.7) 22 - 71
49.7 (11.6) 22 - 67
PTA (dB HL) from .25-8 kHz in ear(s) tested
PTA (dB HL) from .25-8 kHz in deaf ear
Age Onset SPHL (years)
Length of Deafness (years)
13.2 (7.1)
110.2 (10.5)
27.3 (22.7)
21.9 (21.8)
0.0 – 29.3
78.3 – 121.3+
0 - 61
