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Vienna 4/28/2006 1
Click vs. click-click vs. blink-click: Factors influencing human sound localization in the horizontal plane
Norbert Kopčo
TU Košice Dept. of Cybernetics and AIBoston University Hearing Research Center
Dartmouth College Center for Cognitive Neuroscience
Vienna 4/28/2006 2
Intro: Sound localization
3-dimmensional: azimuth, elevation, distance
depends on:• stimulus type: spectrum, temporal aspects• environment: anechoic, reverberant• source movement: static, dynamic • presence of other stimuli (auditory or visual)• a priori knowledge / expectations about the scene
Vienna 4/28/2006 3
Effect of additional stimuli
The extra sound can act as a:
Masker – localization worse
Adaptor – localization biased (Attraction/Repulsion)
Real sound (of which the target is a reflection) – localization worse/suppressed
Perceptual stream of which the target is or is not a part
Cue – localization better (doesn’t have to be auditory)
Anchor – change localization strategy
Vienna 4/28/2006 4
Effect of additional sounds
Temporal relations studied previously:
Extra sound precedes target by:• 10 secs to mins Adaptation/Repulsion• 50 msecs to 1 sec Adaptation/ reflections• 4 – 40 msecs Precedence• Concurrent sounds Adaptation/Repulsion• Inverse order Backward masking
Vienna 4/28/2006 5
Auditory Pathway and Spatial HearingCochlea – peripheral filtering and
neural coding
Olivary complex – processing of binaural information
Thalamus (Inferior Colliculus) – integration, modulation detection
Auditory Cortex – auditory object formation, figure/ground separation, ASA
Posterior Parietal Cortex – supramodal spatial representation & attentional modulation
Vienna 4/28/2006 6
Current goal
Begin to understand auditory localization in a more complex scene:
- when target is preceded by another identical sound/s from a known location that the listener should ignore (Exp 1)
- when target is preceded by visual or auditory cue that allows the listener to direct spatial attention (Exp 2)
- when a concurrent visual stimulus induces a shift in auditory perception / ventriloquism (Exp 3)
Vienna 4/28/2006 7
Experiment 1Perceptual and central effects in sound localization
with a preceding distractor
(aka Click vs. Click-click vs. Click-click-click-click...)
Collaborators
Barbara Shinn-Cunningham, Virginia Best Hearing Research Center
Boston University
Vienna 4/28/2006 8
Exp 1 - Preceding distractor: Intro
Several preceding studies indicated that preceding stimulus influences localization at SOAs of several hundreds milliseconds (Kopco et al., 2001, Perrott and Pacheco, 1989)
Goal:- Characterize this influence (bias and std.dev. in responses)- Determine its cause. Candidates:
- short-term adaptation in brainstem representations- reverberation suppression and acoustics- strategy- perceptual organization- attention: focused away from distractor location
Vienna 4/28/2006 9
Exp 1 - Preceding distractor: Hypotheses
Peripheral factors will have short-term effects
Central factors will influence results at longer separations
Effect of reverberation can be separated by comparing performance in anechoic and echoic rooms
Effect of perceptual organization can be addressed by modifying the stimuli
Vienna 4/28/2006 10
Exp 1 - Preceding distractor: Methods
Anechoic room or a classroom
Blocks of trials with fixed distractor location
Trials with SOAs of 25,50,100,200 or 400 ms interleaved w/ no distractor trials
Seven subjects
Vienna 4/28/2006 11
Exp 1 - Preceding distractor: Results
Complex pattern of biases and standard deviation effects observed
Four main effects in terms of bias discussed
Bias 1: Lateral bias for frontal targets and lateral distractor in room
Vienna 4/28/2006 12
Exp 1 - Preceding distractor: Results – Bias 1
Largest effect
Strongest at
short SOAs
No comparable
effect of frontal
distractor
ROOM
Vienna 4/28/2006 13
Exp 1 - Preceding distractor: Results – Bias 1
Effect eliminated in anechoic room has to do with reverberation.
Acoustic or neural interaction?
ANECHOICROOM
Vienna 4/28/2006 14
Exp 1 – Bias 1: Perceptual organization
Effect not due to acoustics because correct representation is available
ROOM: click-click-click-click … click
ROOM: Click-click
Vienna 4/28/2006 15
Exp 1 – Bias 1: Standard deviation
The largest increase in standard deviation corresponds with the largest bias
Neural suppression along with reflections
BUT: Why only lateral distractor?
Vienna 4/28/2006 16
Exp 1 - Preceding distractor: Results – Bias 2
Targets in the middle of the range are attracted by the distractor, independent of:
- Environment- Distractor location- Only at short
SOAs
Interactions in low-level spatial maps (brainstem)
Vienna 4/28/2006 17
Exp 1 - Preceding distractor: Results – Bias 3
Lateral targets are repulsed by lateral distractors
- Independent of SOA- Independent of
environment
Probably central effect: e.g., change in response strategy, using distractor as an anchor w/ known location
Not in front because of higher resolution.
Vienna 4/28/2006 18
Exp 1 - Preceding distractor: Context
There is bias also in the no-distractor responses
The bias is always away from the non-present distractor
Because the runs were interleaved, this bias had to build up anew during each run
Vienna 4/28/2006 19
Exp 1 - Preceding distractor: Context
Difference in no-distractor responses in the frontal and lateral distractor context
- Is independent of azimuth- Grows over time- Slightly stronger for the 8-click
train contextContextual plasticity on time
scale of minutesSimilar to effects of long-term
exposureEither due to bottom-up factors
(distribution of stimuli) or top-down factors (focusing away from distractor)
Con
text
ual b
ias
Vienna 4/28/2006 20
Exp 1 - Preceding distractor: Summary
A preceding distractor coming from a known location
- Induces a complex pattern of biases - Over a range of time scales- Probably caused at different stages
in the spatial auditory processing pathway
Vienna 4/28/2006 21
Experiment 2Modality-dependant attentional control in human
sound localization
(aka Click vs. Beep-click vs. Blink-click)
In collaboration w/ students
Beáta Tomoriová, Rudolf Andoga, Martin BernátPerception and Cognition LabTechnical University, Košice
Vienna 4/28/2006 22
Exp 2 – Uni-/Cross-modal attention: Intro
Several studies explored the question whether directing automatic or strategic attention by an auditory cue can improve sound localization (Spence & Driver, 1994; Sach, 2000; Kopco & Shinn-Cunningham, 2003)
Results: improvements in RTs (Spence&Driver), but small (Sach) or no (Kopco) improvements in performance
Possible reason: the SOAs too short to orient attention
Goal:- determine whether attentional effects occur at longer SOAs- compare the effect of a visual and auditory cue
Vienna 4/28/2006 23
Exp 2 – Uni-/Cross-modal attention: Hypotheses
No effect of automatic attention (previous studies)
Strategic attention will affect performance at long SOAs
Effect modality-independent because spatial cuing very coarse (only left vs. right)
Vienna 4/28/2006 24
Exp 2 – Uni-/Cross-modal attention: Methods
Virtual auditory environment
Target – broadband click
Cue indicates side of target:- visual (arrow on a computer
screen)- auditory (monaural tone)- SOA: 400, 800, 1600 ms- Informative: 100%, 80%,
50% validity- analysis: mean and s.d. in
responses
90
45
1530
60
90
45
1530
60
Vienna 4/28/2006 25
Exp 2 – Uni-/Cross-modal attn: Results - bias
Mean effect of auditory cue (averaged across target azimuth):- Invalid cues cause medial bias, fairly independent of SOA- Valid cues cause similar medial bias
Vienna 4/28/2006 26
Exp 2 – Uni-/Cross-modal attn: Results - bias
When cue modality is visual:
- Invalid cues cause medial bias, similar to the auditory cues
- Valid cues cause lateral bias that grows with SOA
Modality through
which expectation of
the target location is
controlled influences
the perceived location
Vienna 4/28/2006 27
Exp 2 – Uni-/Cross-modal attn: Results – s.d.
Effect in terms of standard deviation:
No effect of auditory cue
Visual cue never improves performance, but invalid cue at 1600 ms increases s.d.
Summary:
Cuing doesn’t improve performance
Expectation of side of stimulus induces bias in a modality dependent way
Might have something to do with the coordinate systems in which visual and auditory space are represented
Vienna 4/28/2006 28
Experiment 3Behavioral examination of the auditory spatial
coordinate system using the ventriloquism effect
Collaboration
Jennifer GrohCenter for Cognitive Neuroscience, Dept of Psychological
and Brian Sciences, Dartmouth College
Barbara Shinn-Cunningham, I-Fan LinBoston University
Vienna 4/28/2006 29
Exp 3 – Coordinate system of auditory space: Intro
Mullette-Gillman et al. (2005):
Does the visual and auditory spatial coding have the same reference frame in the monkey parietal cortex?
Is the frame head-centered (as in auditory periphery) or eye-centered (as in visual periphery)?
This is an issue only for primates and animals that can move their eyes (not barn owls)
Result: some neurons in PPC A-only, some V-only, some AV, some head-centered, some eye-centered
Vienna 4/28/2006 30
Exp 3 – Coordinate system of auditory space: Intro
Here, use the ventriloquism effect to address a similar question behaviorally in monkeys and in humans:
Is the coordinate system at which the auditory behavioral responses are determined head- or eye-centered?
Method:
1. Induce a local shift in the auditory spatial map for a fixed eye position.
2. Move eyes to a new position.
3. If the region of the shift doesn’t change head-centric
4. Otherwise, eye-centric coordinate system
Vienna 4/28/2006 31
Exp 3 – Coordinate system of auditory space: Method
Study performed in humans and in monkeys
Monkey data here
Vienna 4/28/2006 32
Exp 3 – Coordinate system of auditory space: Results (preliminary)
Difference between positive (rightward) and negative (leftward) shifts induced in the central region with left fixation point and generalization testedwith right fixation point
Result:
Induced shift generalizes
on the right side
No shift in bias due to change
in fixation point Head-centric coordinate system
-30 -24 -18 -12 -6 0 6 12 18 24 30-6
-4
-2
0
2
4
6Diff (M+SE) between responses w/ RIGHT and LEFT shift. Trials:0-2000. 4 repeats.
FIX -8,-16
FIX 8,-16
Vienna 4/28/2006 33
Overall summary
Three experiments explored various aspects of horizontal sound localization
Understanding is limited even in the simple auditory scenes studied
Need follow-ups to clarify results
Vienna 4/28/2006 34
Acknowledgements
US National Institutes of Health (PIs: Shinn-Cunningham and Groh)
US National Academy of Sciences (Shinn-Cunningham, Kopčo)
Slovak Scientific Grant Agency (Kopčo)
Vienna 4/28/2006 35
Distance perception in reverberant environments- is consistent experience necessary for accurate distance perception?
- also, studies looking at other parameters (mono- vs. binaural, anechoic vs. reverberant, real vs. simulated environments)
“Room learning” and calibration to its acoustic properties- is localization accuracy and “room learning” affected by changes in listener
position in a room?- do speech perception mechanisms calibrate to different acoustic
environments?
Spatial release from masking- effect of signal and masker location on detectability/intelligibility of pure tones,
broadband non-speech stimuli, and speech in anechoic and reverberant environments
Overview of recent studies of binaural and spatial hearing