There is evidence that this efferent control may play a role in extracting signals from noise and the detection of target sounds. Here we evaluated the role of attention on the auditory efferent control of the brainstem (using auditory brainstem responses; ABRs) and the cochlear gain (using otoacoustic emissions; OAEs) during passive listening and a task of variable difficulty. We hypothesized that both the ABRs and OAEs would be modulated by attention and that the degree of suppression of OAEs (relative to the passive condition) would increase with task difficulty.

1. Continuous Click-Evoked OAEs
How far down does the top down control of speech processing go?
Heivet Hernandez-Perez 1,2, Jessica Monaghan 1, Sumitrajit Dhar 3, Sriram Boothalingam 3, David Poeppel 4,
Catherine McMahon 1,2
1 Macquarie University, Department of Linguistics, 2 The HEARing Cooperative Research Centre, 3 Northwestern University, Department of Communication
Sciences and Disorders, 3 New York University, Department of Psychology.
Introduction
Methods
Behavioral Results.
creating sound value www.hearingcrc.org
Table 1. Lexical decision tasks d’ values
2. Passive listening: Relax and watch a movie
Experimental conditions
1. Active Listening: Press a button when hearing a
non-word
The perception of speech
sounds in humans requires a fast
and accurate integration of both
bottom-up and top-down
information carried by the auditory
afferent and efferent pathways
respectively (Figure on the right).
However, it remains poorly
understood whether, during
speech perception, the top-down
control reaches the level of the
brainstem or even the cochlea via
the auditory efferent pathway.
Participants: Healthy adults (20-35 y.o.), native Australian-
English speakers
200 words/non words per block
30 sec
Baseline
(silence)
Attended segment
“real word”/“non-word”
0.5 sec
Baseline
(silence)
30 sec
Lexical decision
2 sec
Ear 1
Ear 2
Electrophysiological Results. ERPs
P1
N1
P2
Block 1: Natural spoken words/non words
Block 2 :16 channels vocoded words/non words (Voc16)
Block 3 :12 channels vocoded words/non words (Voc12)
Block 4 : 8 channels vocoded words/non words (Voc8)
• 4 blocks per
experimental condition
• Randomized
presentation of blocks
Words/non-words onset-ERPs components.
• Lexical decision difficulty increases as the number of
speech vocoded channels decreases.
• P1, N1 and P2 differ
between blocks during
active listening (p<0.05)
Electrophysiological Results. ABRs
Wave V, Auditory Brainstem Responses
There is evidence that this efferent control may play a
role in extracting signals from noise and the detection of
target sounds. Here we evaluated the role of attention on
the auditory efferent control of the brainstem (using auditory
brainstem responses; ABRs) and the cochlear gain (using
otoacoustic emissions; OAEs) during passive listening and
a task of variable difficulty. We hypothesized that both the
ABRs and OAEs would be modulated by attention and that
the degree of suppression of OAEs (relative to the passive
condition) would increase with task difficulty.
• Attentional effect:
active condition
showed a decrease in
amplitude and a
significant shift in
phase.
Active listening
uV
t (msec)
Passive listening
Trends:
• Wave V latency shorter in the active condition
• Wave V amplitude smaller in the passive condition
Click-Evoked OAEs Results.
Conclusions
• The experimental protocol and set up is suitable for exploring attention and
task difficulty effects at cortical, brainstem and inner ear levels.
• Our data suggest that the accurate classification of speech sounds engage
not only bottom-up processing but also top-down control mechanisms.
Passive Condition
Active Condition
Click-Evoked OAEs effect
Interval of confidence
Natural spoken block
8 channels vocoded block
• Task difficulty effect:
Voc 8 block showed
a decrease in
amplitude and a
significant shift in
phase.
Natural Voc16 Voc12 Voc 8