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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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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 mins Adaptation/Repulsion
    • 50 msecs to 1 sec Adaptation/ reflections
    • 4 – 40 msecs Precedence
    • Concurrent sounds Adaptation/Repulsion
    • Inverse order Backward 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)
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 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
  • 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
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
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
  • US National Institutes of Health (PIs: Shinn-Cunningham and Groh)
  • US National Academy of Sciences (Shinn-Cunningham, Kopčo)
  • Slovak Scientific Grant Agency (Kopčo)
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