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A neural network model can explain ventriloquism aftereffect and its generalization across sound frequencies.

Magosso E, Cona F, Ursino M - Biomed Res Int (2013)

Bottom Line: Exposure to synchronous but spatially disparate auditory and visual stimuli produces a perceptual shift of sound location towards the visual stimulus (ventriloquism effect).The model provides a coherent theoretical framework to explain the apparently contradictory results found in the literature.Model mechanisms and hypotheses are discussed in relation to neurophysiological and psychophysical data.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, Via Venezia 52, 47521 Cesena, Italy.

ABSTRACT
Exposure to synchronous but spatially disparate auditory and visual stimuli produces a perceptual shift of sound location towards the visual stimulus (ventriloquism effect). After adaptation to a ventriloquism situation, enduring sound shift is observed in the absence of the visual stimulus (ventriloquism aftereffect). Experimental studies report opposing results as to aftereffect generalization across sound frequencies varying from aftereffect being confined to the frequency used during adaptation to aftereffect generalizing across some octaves. Here, we present an extension of a model of visual-auditory interaction we previously developed. The new model is able to simulate the ventriloquism effect and, via Hebbian learning rules, the ventriloquism aftereffect and can be used to investigate aftereffect generalization across frequencies. The model includes auditory neurons coding both for the spatial and spectral features of the auditory stimuli and mimicking properties of biological auditory neurons. The model suggests that different extent of aftereffect generalization across frequencies can be obtained by changing the intensity of the auditory stimulus that induces different amounts of activation in the auditory layer. The model provides a coherent theoretical framework to explain the apparently contradictory results found in the literature. Model mechanisms and hypotheses are discussed in relation to neurophysiological and psychophysical data.

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Activation of auditory neurons (at steady state) in response to spatially disparate visual auditory stimulation (the same stimuli position as in Figure 5) using auditory stimulus intensity E0a = 17 (a) and E0a = 20 (b).
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fig6: Activation of auditory neurons (at steady state) in response to spatially disparate visual auditory stimulation (the same stimuli position as in Figure 5) using auditory stimulus intensity E0a = 17 (a) and E0a = 20 (b).

Mentions: Different sound intensities may produce different ventriloquism effects, due to the different activation in the auditory area. Figure 6(a) shows the steady-state response of the auditory layer to a spatially disparate visual-auditory stimulation as in Figure 5 (that is the visual stimulus was applied at 100° and the auditory stimulus was applied at 80° and 1.1 kHz), using an intensity of 17 (E0a = 17), instead of 20, for the auditory stimulus. To facilitate comparison, the last panel of Figure 5 is reported in Figure 6(b) too. In case of higher auditory stimulus intensity, (cf. Figures 6(a) and 6(b)) the auditory neurons are on the overall more activated. It is interesting to note that the amount of perceptual sound shift was lower in case of the higher stimulus intensity (3.6° at E0a = 20 versus 4.7° at E0a = 17): this was due to the higher and wider activation in the region left of 90° that strongly influenced the barycenter computation.


A neural network model can explain ventriloquism aftereffect and its generalization across sound frequencies.

Magosso E, Cona F, Ursino M - Biomed Res Int (2013)

Activation of auditory neurons (at steady state) in response to spatially disparate visual auditory stimulation (the same stimuli position as in Figure 5) using auditory stimulus intensity E0a = 17 (a) and E0a = 20 (b).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3818813&req=5

fig6: Activation of auditory neurons (at steady state) in response to spatially disparate visual auditory stimulation (the same stimuli position as in Figure 5) using auditory stimulus intensity E0a = 17 (a) and E0a = 20 (b).
Mentions: Different sound intensities may produce different ventriloquism effects, due to the different activation in the auditory area. Figure 6(a) shows the steady-state response of the auditory layer to a spatially disparate visual-auditory stimulation as in Figure 5 (that is the visual stimulus was applied at 100° and the auditory stimulus was applied at 80° and 1.1 kHz), using an intensity of 17 (E0a = 17), instead of 20, for the auditory stimulus. To facilitate comparison, the last panel of Figure 5 is reported in Figure 6(b) too. In case of higher auditory stimulus intensity, (cf. Figures 6(a) and 6(b)) the auditory neurons are on the overall more activated. It is interesting to note that the amount of perceptual sound shift was lower in case of the higher stimulus intensity (3.6° at E0a = 20 versus 4.7° at E0a = 17): this was due to the higher and wider activation in the region left of 90° that strongly influenced the barycenter computation.

Bottom Line: Exposure to synchronous but spatially disparate auditory and visual stimuli produces a perceptual shift of sound location towards the visual stimulus (ventriloquism effect).The model provides a coherent theoretical framework to explain the apparently contradictory results found in the literature.Model mechanisms and hypotheses are discussed in relation to neurophysiological and psychophysical data.

View Article: PubMed Central - PubMed

Affiliation: Department of Electrical, Electronic, and Information Engineering "Guglielmo Marconi", University of Bologna, Via Venezia 52, 47521 Cesena, Italy.

ABSTRACT
Exposure to synchronous but spatially disparate auditory and visual stimuli produces a perceptual shift of sound location towards the visual stimulus (ventriloquism effect). After adaptation to a ventriloquism situation, enduring sound shift is observed in the absence of the visual stimulus (ventriloquism aftereffect). Experimental studies report opposing results as to aftereffect generalization across sound frequencies varying from aftereffect being confined to the frequency used during adaptation to aftereffect generalizing across some octaves. Here, we present an extension of a model of visual-auditory interaction we previously developed. The new model is able to simulate the ventriloquism effect and, via Hebbian learning rules, the ventriloquism aftereffect and can be used to investigate aftereffect generalization across frequencies. The model includes auditory neurons coding both for the spatial and spectral features of the auditory stimuli and mimicking properties of biological auditory neurons. The model suggests that different extent of aftereffect generalization across frequencies can be obtained by changing the intensity of the auditory stimulus that induces different amounts of activation in the auditory layer. The model provides a coherent theoretical framework to explain the apparently contradictory results found in the literature. Model mechanisms and hypotheses are discussed in relation to neurophysiological and psychophysical data.

Show MeSH
Related in: MedlinePlus