Abstract The study compares the effects of auditory masking and auditory distortion on memory for... more Abstract The study compares the effects of auditory masking and auditory distortion on memory for words in younger and older adults. Partially masking words by a babble noise has an age-dependent, adverse effect on memory. On the other hand, temporally distorting the words, so that they are equally-often misheard as when they were partially masked, has no effect on memory unless the words are presented at high-intensity levels.
A number of factors could explain the adverse effect that babble noise has on memory for spoken w... more A number of factors could explain the adverse effect that babble noise has on memory for spoken words . Babble could degrade the perceptual representation of words to such an extent that it compromises their subsequent processing, or the presence of speech noise in the period between word presentations could interfere with rehearsal. Thirdly, the top-down processes needed to extract the words from the babble could draw on resources that otherwise would be used for encoding. We tested all these hypotheses by presenting babble either only during word presentation or rehearsal, or by gating the babble on and off 500 ms before and after each word pair. Only the last condition led to a decline in memory. We propose that this decline in memory occurred because participants were focusing their attention on the auditory stream (to enable them to better segregate the words from the noise background) rather than on remembering the words they had heard. To further support our claim we show that a similar memory deficit results when participants perform the same memory task in quiet together with a nonauditory attention-demanding secondary task.
We examined the neural correlates associated with a short gap between two identical pure tones (w... more We examined the neural correlates associated with a short gap between two identical pure tones (within-channel) and between two di¡erent tones (between-channel) in an odd-ball paradigm. Gap durations were selected such that a gap between identical tones was as discriminable as a gap between two di¡erent tones. Spatio-temporal dipole source modeling of electrophysiological data revealed a signi¢cant di¡erence between standard and deviant gap stimuli, with mismatch negativity responses that were comparable in amplitude and latency for within-and betweenchannel conditions.Therefore, the ability to automatically register discontinuity (i.e., gap) within and between channels is comparable despite signi¢cant di¡erences in gap size.The dipole source modeling suggests that both within-and between-gap signals are represented in or near the primary auditory cortex. NeuroReport
& We used functional magnetic resonance imaging to study the neural processing of vowels whose pe... more & We used functional magnetic resonance imaging to study the neural processing of vowels whose perception depends on the continuity illusion. Participants heard sequences of twoformant vowels under a number of listening conditions. In the ''vowel conditions,'' both formants were always present simultaneously and the stimuli were perceived as speech-like. Contrasted with a range of nonspeech sounds, these vowels elicited activity in the posterior middle temporal gyrus (MTG) and superior temporal sulcus (STS). When the two formants alternated in time, the ''speech-likeness'' of the sounds was reduced. It could be partially restored by filling the silent gaps in each formant with bands of noise (the ''Illusion'' condition) because the noise induced an illusion of continuity in each formant region, causing the two formants to be perceived as simultaneous. However, this manipulation was only effective at low formant-to-noise ratios (FNRs). When the FNR was increased, the illusion broke down (the ''illusion-break'' condition). Activation in vowel-sensitive regions of the MTG was greater in the illusion than in the illusion-break condition, consistent with the perception of Illusion stimuli as vowels. Activity in Heschl's gyri, the approximate location of the primary auditory cortex, showed the opposite pattern, and may depend instead on the number of perceptual onsets in a sound. Our results demonstrate that speech-sensitive regions of the MTG are sensitive not to the physical characteristics of the stimulus but to the perception of the stimulus as speech, and also provide an anatomically distinct, objective physiological correlate of the continuity illusion in human listeners. &
The Journal of the Acoustical Society of …, Jan 1, 2006
Pure tone gap stimuli with identical (within-channel) or dissimilar (between-channel) marker freq... more Pure tone gap stimuli with identical (within-channel) or dissimilar (between-channel) marker frequencies of 1 and 2 kHz were presented to young and old listeners in a two-interval forced choice gap detection task. To estimate the influence of extraneous duration cues on gap detection, thresholds in the between-channel conditions were obtained for two different sets of reference stimuli: reference stimuli that were matched to the overall duration of the gap stimulus, i.e., two markers plus the gap, and reference stimuli that were fixed at the combined duration of the two markers excluding the gap. Results from within-channel conditions were consistent with previous studies, i.e., there were small but highly reliable age differences, smaller gap thresholds at longer marker durations, and an interaction between the two variables. In between-channel conditions, however, age differences were not as clear cut. Rather, the effect of age varied as a function of duration cue and was more pronounced when stimuli were matched for overall duration than when the duration of the reference tone was fixed.
We investigated the importance of phonetic information in preceding syllables for the intelligibi... more We investigated the importance of phonetic information in preceding syllables for the intelligibility of minimal-pair words containing /r/ or /l/. Target words were cross-spliced into a different token of the same sentence (match) or into a sentence that was identical but originally ...
We describe objective measures of two aspects of auditory scene analysis (ASA). We show that the ... more We describe objective measures of two aspects of auditory scene analysis (ASA). We show that the build-up of auditory streaming can be measured using a behavioural task-detection of a temporal shift of one tone relative to another-that is easiest when the two tones are part of the same stream. This paradigm is used to show that performance can be improved by requiring participants to briefly divert their attention away from the tones, a manipulation that has previously been shown to increase the number of “one stream” judgements in a ...
■ We investigate whether the neural correlates of the continuity illusion, as measured using fMRI... more ■ We investigate whether the neural correlates of the continuity illusion, as measured using fMRI, are modulated by attention. As we have shown previously, when two formants of a synthetic vowel are presented in an alternating pattern, the vowel can be identified if the gaps in each formant are filled with bursts of plausible masking noise, causing the illusory percept of a continuous vowel ("illusion" condition). When the formant-to-noise ratio is increased so that noise no longer plausibly masks the formants, the formants are heard as interrupted ("illusion break" condition) and vowels are not identifiable. A region of the left middle temporal gyrus (MTG) is sensitive both to intact synthetic vowels (two formants present simultaneously) and to illusion stimuli, compared to illusion Break stimuli. Here, we compared these conditions in the presence and absence of attention. We examined fMRI signal for different sound types under three attentional conditions: full attention to the vowels; attention to a visual distracter; or attention to an auditory distracter. Crucially, although a robust main effect of attentional state was observed in many regions, the effect of attention did not differ systematically for the illusory vowels compared to either intact vowels or to the illusion break stimuli in the left STG/MTG vowel-sensitive region. This result suggests that illusory continuity of vowels is an obligatory perceptual process, and operates independently of attentional state. An additional finding was that the sensitivity of primary auditory cortex to the number of sound onsets in the stimulus was modulated by attention. ■
In particular, this thesis investigated two possible ways in which background babble (several peo... more In particular, this thesis investigated two possible ways in which background babble (several people talking simultaneously) may adversely affect memory performance. The babble could mask the stimulus and degrade the perceptual representation of words to such an extent ...
A loss of speech intelligibility at high presentation levels is called rollover. It is a phenomen... more A loss of speech intelligibility at high presentation levels is called rollover. It is a phenomenon that increases in prevalence as people age. Whether the adverse effect of high presentation levels extends to processes subsequent to speech intelligibility, such as memory, is unknown. The present study examined this question on the basis of the previous finding that older but not younger adults showed memory impairment when acoustically distorted words were presented at 50 dB SL compared with an undistorted baseline presented at 65 dB SPL. One question investigated in the present study was whether a presentation level of 50 dB SL put older listeners at the cusp of rollover and whether this subsequently impaired memory. Moreover, we wanted to know whether and at what level it was possible to induce a similar impairment in younger listeners.
Bien comprendre les panneaux de signalisation est critique pour bien conduire aun véhicule, réagi... more Bien comprendre les panneaux de signalisation est critique pour bien conduire aun véhicule, réagir aux avertissements, et s'orienter. Les aînés qui comprennent mal un panneau routier risquent davantage de subir un accident et de voir leur indépendance compromise. La présente étude visait à déterminer le degré de compréhension des pictogrammes par des aînés en bonne santé et des aînés souffrant de déficience. De plus, nous nous sommes demandé si l'ajout de texte aux pictogrammes permettrait aux aînés de les mieux comprendre. Lors de l'Expérience 1, nous avons demandé à des jeunes adultes, à des adultes plus âgés en bonne santé et aussi à des aînés souffrant de déficience cognitive à divers degrés, la signification de 65 panneaux routiers visant la conduite, les avertissements, et l'orientation. Les adultes plus âgés en bonne santé comprenaient bien la signalisation en général, mais avaient de la difficulté à déterminer ce que signifiait le panneau d'orientation. Les aînés souffrant de déficience cognitive comprenaient en général moins bien les panneaux routiers et en particulier les icô nes d'orientation et les panneaux avec seulement un pictogramme. Au cours de l'Expérience 2, nous avons demandé à des aînés en bonne santé la signification de panneaux comportant seulement des icô nes ou des icô nes avec du texte. La compréhension était améliorée de façon importante lorsque le panneau comportait du texte. Ce travail a démontré que l'évaluation de la compréhension des panneaux de signalisation doit porter sur un vaste échantillon hétérogène d'adultes plus âgés dans l'échelle de capacités perceptuelles et cognitives représentées dans la population.
ABSTRACT In a previous study, we exploited the Gestalt principle of closure to create illusory vo... more ABSTRACT In a previous study, we exploited the Gestalt principle of closure to create illusory vowel sounds and examined the neural correlates of their perception using fMRI. When two formants of a synthetic vowel are presented in an alternating pattern, filling the gaps in each formant with bursts of noise causes the formants to be heard as continuous and more vowel-like. When this "Illusion" condition was modified by increasing the formant-to-noise ratio (FNR), the formants were heard as interrupted ("Illusion Break" condition) and less vowel-like. BOLD signal in the Middle Temporal Gyrus (MTG) was greater for Illusion than for Illusion-Break stimuli, reflecting the difference in speechlikeness. Primary auditory areas (PAC) exhibited the opposite pattern, probably because Illusion-Break stimuli contain more perceived sound onsets than the Illusion stimuli. In the current study we examine whether the neural activation to illusory vowels and sound onsets is modulated by attention. Participants were scanned while listening to Illusion, Illusion Break, and two types of intact vowels and simultaneously directing their attention either to the vowel stimuli or to auditory or visual distractors. Preliminary analyses suggest that activation to intact and illusory vowels in MTG, and to sound onset in PAC, is modulated by attention.
Zusammenfassung: Wächst das Allgemeinwissen mit dem Lebensalter, so dass ältere Menschen in einem... more Zusammenfassung: Wächst das Allgemeinwissen mit dem Lebensalter, so dass ältere Menschen in einem Wissenstest bes-ser abschneiden als jüngere? Oder wissen jüngere Menschen am meisten, da sie in der Schule und im Studium mit den verschiedensten Unterrichtsfächern ...
Abstract The study compares the effects of auditory masking and auditory distortion on memory for... more Abstract The study compares the effects of auditory masking and auditory distortion on memory for words in younger and older adults. Partially masking words by a babble noise has an age-dependent, adverse effect on memory. On the other hand, temporally distorting the words, so that they are equally-often misheard as when they were partially masked, has no effect on memory unless the words are presented at high-intensity levels.
A number of factors could explain the adverse effect that babble noise has on memory for spoken w... more A number of factors could explain the adverse effect that babble noise has on memory for spoken words . Babble could degrade the perceptual representation of words to such an extent that it compromises their subsequent processing, or the presence of speech noise in the period between word presentations could interfere with rehearsal. Thirdly, the top-down processes needed to extract the words from the babble could draw on resources that otherwise would be used for encoding. We tested all these hypotheses by presenting babble either only during word presentation or rehearsal, or by gating the babble on and off 500 ms before and after each word pair. Only the last condition led to a decline in memory. We propose that this decline in memory occurred because participants were focusing their attention on the auditory stream (to enable them to better segregate the words from the noise background) rather than on remembering the words they had heard. To further support our claim we show that a similar memory deficit results when participants perform the same memory task in quiet together with a nonauditory attention-demanding secondary task.
We examined the neural correlates associated with a short gap between two identical pure tones (w... more We examined the neural correlates associated with a short gap between two identical pure tones (within-channel) and between two di¡erent tones (between-channel) in an odd-ball paradigm. Gap durations were selected such that a gap between identical tones was as discriminable as a gap between two di¡erent tones. Spatio-temporal dipole source modeling of electrophysiological data revealed a signi¢cant di¡erence between standard and deviant gap stimuli, with mismatch negativity responses that were comparable in amplitude and latency for within-and betweenchannel conditions.Therefore, the ability to automatically register discontinuity (i.e., gap) within and between channels is comparable despite signi¢cant di¡erences in gap size.The dipole source modeling suggests that both within-and between-gap signals are represented in or near the primary auditory cortex. NeuroReport
& We used functional magnetic resonance imaging to study the neural processing of vowels whose pe... more & We used functional magnetic resonance imaging to study the neural processing of vowels whose perception depends on the continuity illusion. Participants heard sequences of twoformant vowels under a number of listening conditions. In the ''vowel conditions,'' both formants were always present simultaneously and the stimuli were perceived as speech-like. Contrasted with a range of nonspeech sounds, these vowels elicited activity in the posterior middle temporal gyrus (MTG) and superior temporal sulcus (STS). When the two formants alternated in time, the ''speech-likeness'' of the sounds was reduced. It could be partially restored by filling the silent gaps in each formant with bands of noise (the ''Illusion'' condition) because the noise induced an illusion of continuity in each formant region, causing the two formants to be perceived as simultaneous. However, this manipulation was only effective at low formant-to-noise ratios (FNRs). When the FNR was increased, the illusion broke down (the ''illusion-break'' condition). Activation in vowel-sensitive regions of the MTG was greater in the illusion than in the illusion-break condition, consistent with the perception of Illusion stimuli as vowels. Activity in Heschl's gyri, the approximate location of the primary auditory cortex, showed the opposite pattern, and may depend instead on the number of perceptual onsets in a sound. Our results demonstrate that speech-sensitive regions of the MTG are sensitive not to the physical characteristics of the stimulus but to the perception of the stimulus as speech, and also provide an anatomically distinct, objective physiological correlate of the continuity illusion in human listeners. &
The Journal of the Acoustical Society of …, Jan 1, 2006
Pure tone gap stimuli with identical (within-channel) or dissimilar (between-channel) marker freq... more Pure tone gap stimuli with identical (within-channel) or dissimilar (between-channel) marker frequencies of 1 and 2 kHz were presented to young and old listeners in a two-interval forced choice gap detection task. To estimate the influence of extraneous duration cues on gap detection, thresholds in the between-channel conditions were obtained for two different sets of reference stimuli: reference stimuli that were matched to the overall duration of the gap stimulus, i.e., two markers plus the gap, and reference stimuli that were fixed at the combined duration of the two markers excluding the gap. Results from within-channel conditions were consistent with previous studies, i.e., there were small but highly reliable age differences, smaller gap thresholds at longer marker durations, and an interaction between the two variables. In between-channel conditions, however, age differences were not as clear cut. Rather, the effect of age varied as a function of duration cue and was more pronounced when stimuli were matched for overall duration than when the duration of the reference tone was fixed.
We investigated the importance of phonetic information in preceding syllables for the intelligibi... more We investigated the importance of phonetic information in preceding syllables for the intelligibility of minimal-pair words containing /r/ or /l/. Target words were cross-spliced into a different token of the same sentence (match) or into a sentence that was identical but originally ...
We describe objective measures of two aspects of auditory scene analysis (ASA). We show that the ... more We describe objective measures of two aspects of auditory scene analysis (ASA). We show that the build-up of auditory streaming can be measured using a behavioural task-detection of a temporal shift of one tone relative to another-that is easiest when the two tones are part of the same stream. This paradigm is used to show that performance can be improved by requiring participants to briefly divert their attention away from the tones, a manipulation that has previously been shown to increase the number of “one stream” judgements in a ...
■ We investigate whether the neural correlates of the continuity illusion, as measured using fMRI... more ■ We investigate whether the neural correlates of the continuity illusion, as measured using fMRI, are modulated by attention. As we have shown previously, when two formants of a synthetic vowel are presented in an alternating pattern, the vowel can be identified if the gaps in each formant are filled with bursts of plausible masking noise, causing the illusory percept of a continuous vowel ("illusion" condition). When the formant-to-noise ratio is increased so that noise no longer plausibly masks the formants, the formants are heard as interrupted ("illusion break" condition) and vowels are not identifiable. A region of the left middle temporal gyrus (MTG) is sensitive both to intact synthetic vowels (two formants present simultaneously) and to illusion stimuli, compared to illusion Break stimuli. Here, we compared these conditions in the presence and absence of attention. We examined fMRI signal for different sound types under three attentional conditions: full attention to the vowels; attention to a visual distracter; or attention to an auditory distracter. Crucially, although a robust main effect of attentional state was observed in many regions, the effect of attention did not differ systematically for the illusory vowels compared to either intact vowels or to the illusion break stimuli in the left STG/MTG vowel-sensitive region. This result suggests that illusory continuity of vowels is an obligatory perceptual process, and operates independently of attentional state. An additional finding was that the sensitivity of primary auditory cortex to the number of sound onsets in the stimulus was modulated by attention. ■
In particular, this thesis investigated two possible ways in which background babble (several peo... more In particular, this thesis investigated two possible ways in which background babble (several people talking simultaneously) may adversely affect memory performance. The babble could mask the stimulus and degrade the perceptual representation of words to such an extent ...
A loss of speech intelligibility at high presentation levels is called rollover. It is a phenomen... more A loss of speech intelligibility at high presentation levels is called rollover. It is a phenomenon that increases in prevalence as people age. Whether the adverse effect of high presentation levels extends to processes subsequent to speech intelligibility, such as memory, is unknown. The present study examined this question on the basis of the previous finding that older but not younger adults showed memory impairment when acoustically distorted words were presented at 50 dB SL compared with an undistorted baseline presented at 65 dB SPL. One question investigated in the present study was whether a presentation level of 50 dB SL put older listeners at the cusp of rollover and whether this subsequently impaired memory. Moreover, we wanted to know whether and at what level it was possible to induce a similar impairment in younger listeners.
Bien comprendre les panneaux de signalisation est critique pour bien conduire aun véhicule, réagi... more Bien comprendre les panneaux de signalisation est critique pour bien conduire aun véhicule, réagir aux avertissements, et s'orienter. Les aînés qui comprennent mal un panneau routier risquent davantage de subir un accident et de voir leur indépendance compromise. La présente étude visait à déterminer le degré de compréhension des pictogrammes par des aînés en bonne santé et des aînés souffrant de déficience. De plus, nous nous sommes demandé si l'ajout de texte aux pictogrammes permettrait aux aînés de les mieux comprendre. Lors de l'Expérience 1, nous avons demandé à des jeunes adultes, à des adultes plus âgés en bonne santé et aussi à des aînés souffrant de déficience cognitive à divers degrés, la signification de 65 panneaux routiers visant la conduite, les avertissements, et l'orientation. Les adultes plus âgés en bonne santé comprenaient bien la signalisation en général, mais avaient de la difficulté à déterminer ce que signifiait le panneau d'orientation. Les aînés souffrant de déficience cognitive comprenaient en général moins bien les panneaux routiers et en particulier les icô nes d'orientation et les panneaux avec seulement un pictogramme. Au cours de l'Expérience 2, nous avons demandé à des aînés en bonne santé la signification de panneaux comportant seulement des icô nes ou des icô nes avec du texte. La compréhension était améliorée de façon importante lorsque le panneau comportait du texte. Ce travail a démontré que l'évaluation de la compréhension des panneaux de signalisation doit porter sur un vaste échantillon hétérogène d'adultes plus âgés dans l'échelle de capacités perceptuelles et cognitives représentées dans la population.
ABSTRACT In a previous study, we exploited the Gestalt principle of closure to create illusory vo... more ABSTRACT In a previous study, we exploited the Gestalt principle of closure to create illusory vowel sounds and examined the neural correlates of their perception using fMRI. When two formants of a synthetic vowel are presented in an alternating pattern, filling the gaps in each formant with bursts of noise causes the formants to be heard as continuous and more vowel-like. When this "Illusion" condition was modified by increasing the formant-to-noise ratio (FNR), the formants were heard as interrupted ("Illusion Break" condition) and less vowel-like. BOLD signal in the Middle Temporal Gyrus (MTG) was greater for Illusion than for Illusion-Break stimuli, reflecting the difference in speechlikeness. Primary auditory areas (PAC) exhibited the opposite pattern, probably because Illusion-Break stimuli contain more perceived sound onsets than the Illusion stimuli. In the current study we examine whether the neural activation to illusory vowels and sound onsets is modulated by attention. Participants were scanned while listening to Illusion, Illusion Break, and two types of intact vowels and simultaneously directing their attention either to the vowel stimuli or to auditory or visual distractors. Preliminary analyses suggest that activation to intact and illusory vowels in MTG, and to sound onset in PAC, is modulated by attention.
Zusammenfassung: Wächst das Allgemeinwissen mit dem Lebensalter, so dass ältere Menschen in einem... more Zusammenfassung: Wächst das Allgemeinwissen mit dem Lebensalter, so dass ältere Menschen in einem Wissenstest bes-ser abschneiden als jüngere? Oder wissen jüngere Menschen am meisten, da sie in der Schule und im Studium mit den verschiedensten Unterrichtsfächern ...
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