Click vs. click-click vs. blink-click:
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Click vs. click-click vs. blink-click: Factors influencing human sound localization in the horizontal plane. Norbert Kopčo TU Košice Dept. of Cybernetics and AI Boston University Hearing Research Center Dartmouth College Center for Cognitive Neuroscience. Intro: Sound localization.

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Norbert kop o

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 CenterDartmouth College Center for Cognitive Neuroscience


Intro sound localization

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


Effect of additional stimuli

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


Effect of additional sounds

Effect of additional sounds

  • Temporal relations studied previously:

  • Extra sound precedes target by:

    • 10 secs to minsAdaptation/Repulsion

    • 50 msecs to 1 secAdaptation/ reflections

    • 4 – 40 msecs Precedence

    • Concurrent soundsAdaptation/Repulsion

    • Inverse orderBackward masking


Auditory pathway and spatial hearing

Auditory Pathway and Spatial Hearing

  • Cochlea – 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


Current goal

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)


Norbert kop o

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


Exp 1 preceding distractor intro

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


Exp 1 preceding distractor hypotheses

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


Exp 1 preceding distractor methods

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


Exp 1 preceding distractor results

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


Exp 1 preceding distractor results bias 1

Exp 1 - Preceding distractor: Results – Bias 1

  • ROOM

  • Largest effect

  • Strongest at

  • short SOAs

  • No comparable

  • effect of frontal

  • distractor


Exp 1 preceding distractor results bias 11

Exp 1 - Preceding distractor: Results – Bias 1

  • ANECHOIC

  • ROOM

  • Effect eliminated in anechoic room  has to do with reverberation.

  • Acoustic or neural interaction?


Exp 1 bias 1 perceptual organization

Exp 1 – Bias 1: Perceptual organization

  • ROOM: Click-click

  • ROOM: click-click-click-click … click

  • Effect not due to acoustics because correct representation is available


Exp 1 bias 1 standard deviation

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?


Exp 1 preceding distractor results bias 2

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)


Exp 1 preceding distractor results bias 3

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.


Exp 1 preceding distractor context

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


Exp 1 preceding distractor context1

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 context

  • Contextual plasticity on time scale of minutes

  • Similar to effects of long-term exposure

  • Either due to bottom-up factors (distribution of stimuli) or top-down factors (focusing away from distractor)

Contextual bias


Exp 1 preceding distractor summary

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


Norbert kop o

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 Bernát

  • Perception and Cognition Lab

  • Technical University, Košice


Exp 2 uni cross modal attention intro

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


Exp 2 uni cross modal attention hypotheses

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)


Exp 2 uni cross modal attention methods

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


Exp 2 uni cross modal attn results bias

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


Exp 2 uni cross modal attn results bias1

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


Exp 2 uni cross modal attn results s d

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


Norbert kop o

Experiment 3Behavioral examination of the auditory spatial coordinate system using the ventriloquism effect

  • Collaboration

  • Jennifer Groh

  • Center for Cognitive Neuroscience, Dept of Psychological and Brian Sciences, Dartmouth College

  • Barbara Shinn-Cunningham, I-Fan Lin

  • Boston University


Exp 3 coordinate system of auditory space intro

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


Exp 3 coordinate system of auditory space intro1

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:

  • Induce a local shift in the auditory spatial map for a fixed eye position.

  • Move eyes to a new position.

  • If the region of the shift doesn’t change  head-centric

  • Otherwise, eye-centric coordinate system


Exp 3 coordinate system of auditory space method

Exp 3 – Coordinate system of auditory space: Method

  • Study performed in humans and in monkeys

  • Monkey data here


Exp 3 coordinate system of auditory space results preliminary

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


Overall summary

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


Norbert kop o

Acknowledgements

  • US National Institutes of Health (PIs: Shinn-Cunningham and Groh)

  • US National Academy of Sciences (Shinn-Cunningham, Kopčo)

  • Slovak Scientific Grant Agency (Kopčo)


Norbert kop o

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


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