Presentations

Abstract

When talking, speakers continuously monitor and use the auditory feedback of their own voice to control and inform speech production processes. Auditory feedback processing has been studied using perturbed auditory feedback. When speakers are provided with auditory feedback that is perturbed in real time, most of them compensate for this by opposing the feedback perturbation. For example, when speakers hear themselves at a higher pitch than intended, they would compensate by lowering their pitch. However, sometimes speakers follow the perturbation instead (i.e., raising their pitch in response to higher-than-expected pitch). Although most past studies observe some following responses, current theoretical frameworks cannot account for following responses. In addition, recent experimental work has suggested that following responses may be more common than has been assumed to date.
In the current study, we performed two experiments (N = 39 and N = 24) to investigate whether the state of the speech production system at perturbation onset may determine what type of response (opposing or following) is given. Participants vocalized while they tried to match a target pitch level. Meanwhile, the pitch in their auditory feedback was briefly (500 ms) perturbed in half of the vocalizations, increasing or decreasing pitch by 25 cents. None of the participants were aware of these manipulations. Subsequently, we analyzed the pitch contour of the participants’ vocalizations.
The results suggest that whether a perturbation-related response is opposing or following unexpected feedback depends on ongoing fluctuations of the production system: It initially responds by doing the opposite of what it was doing. In addition, the results show that all speakers show both following and opposing responses, although the distribution of response types varies across individuals.
Both the interaction with ongoing fluctuations of the speech system and the non-trivial proportion of following responses suggest that current production models are inadequate: They need to account for why responses to unexpected sensory feedback depend on the production-system’s state at the time of perturbation. More generally, the current study indicates that looking beyond the average response can lead to a more complete view on the nature of feedback processing in motor control. Future work should explore whether the direction of feedback-based control in domains outside of speech production will also be conditional on the state of the motor system at the time of the perturbation.

Abstract

One of the most daunting tasks of a listener is to map a continuous auditory stream onto known speech sound categories and lexical items. A major issue with this mapping problem is the variability in the acoustic realizations of sound categories, both within and across speakers. Past research has suggested listeners may use various sources of information, such as lexical knowledge or visual cues (e.g., lip-reading) to recalibrate these speech categories to the current speaker. Previous studies have focused on audiovisual recalibration of consonant categories. The present study explores whether vowel categorization, which is known to show less sharply defined category boundaries, also benefit from visual cues.
Participants were exposed to videos of a speaker pronouncing one out of two vowels (Dutch vowels /e/ and /ø/), paired with audio that was ambiguous between the two vowels. The most ambiguous vowel token was determined on an individual basis by a categorization task at the beginning of the experiment. In one group of participants, this auditory token was paired with a video of an /e/ articulation, in the other group with an /ø/ video. After exposure to these videos, it was found in an audio-only categorization task that participants had adapted their categorization behavior as a function of the video exposure. The group that was exposed to /e/ videos showed a reduction of /ø/ classifications, suggesting they had recalibrated their vowel categories based on the available visual information. These results show that listeners indeed use visual information to recalibrate vowel categories, which is in line with previous work on audiovisual recalibration in consonant categories, and lexically-guided recalibration in both vowels and consonants.
In addition, a secondary aim of the current study was to explore individual variability in audiovisual recalibration. Phoneme categories vary not only in terms of boundary location, but also in terms of boundary sharpness, or how strictly categories are distinguished. The present study explores whether this sharpness is associated with the amount of audiovisual recalibration. The results tentatively support that a fuzzy boundary is associated with stronger recalibration, suggesting that listeners’ category sharpness may be related to the weight they assign to visual information in audiovisual speech perception. If listeners with fuzzy boundaries assign more weight to visual cues, given that vowel categories have less sharp boundaries than consonants, there ought to be audiovisual recalibration for vowels as well. This is exactly what was found in the current study.

Abstract

The classroom is designed to teach children cultural inventions for which the brain is not evolutionary designed. Hence the
classroom environment has to implement cultural reycling of neuronal maps. To do this effectively it has to recruit existing neural
infrastructure. Therefore, teaching programmes have to be tailored to the possibilities and limitations of available neural architecture.
An example in case is reading, a cultural invention of a few thousand years old. Orthographies and reading methods need
to use visual cortex areas in the most optimal way. I will discuss how the characteristics of different orthographies are tailored
to the possibilities of complex cells in visual cortex. In addition, different reading methods will be evaluated in the light of our
understanding of human brain organization. I will argue that a systematic investigation of culture-brain relations is much needed
for optimizing the optimal environment.

Abstract

Institute of Adaptive and Neural Computation, School of Informatics, University of Edinburgh, UK

Abstract

Speech production is one of the most complex motor skills, and involves close interaction between perceptual and motor systems. One way to investigate this interaction is to provide speakers with manipulated auditory feedback during speech production. Using this paradigm, investigators have started to identify a neural network that underlies auditory feedback processing and monitoring during speech production. However, to date, still little is known about the neural mechanisms that underlie feedback processing. The present study set out to shed more light on the neural correlates of processing auditory feedback. Participants (N = 39) were seated in an MEG scanner and were asked to vocalize the vowel /e/continuously throughout each trial (of 4 s) while trying to match a pre-specified pitch target of 4, 8 or 11 semitones above the participants’ baseline pitch level. They received auditory feedback through ear plugs. In half of the trials, the pitch in the auditory feedback was unexpectedly manipulated (raised by 25 cents) for 500 ms, starting between 500ms and 1500ms after speech onset. In the other trials, feedback was normal throughout the trial. In a second block of trials, participants listened passively to recordings of the auditory feedback they received during vocalization in the first block. Even though none of the participants reported being aware of any feedback perturbations, behavioral responses showed that participants on average compensated for the feedback perturbation by decreasing the pitch in their vocalizations, starting at about 100ms after perturbation onset until about 100 ms after perturbation offset. MEG data was analyzed, time-locked to the onset of the feedback perturbation in the perturbation trials, and to matched time-points in the control trials. A cluster-based permutation test showed that the event-related field responses differed between the perturbation and the control condition. This difference was mainly driven by an ERF response peaking at about 100ms after perturbation onset and a larger response after perturbation offset. Both these were localized to sensorimotor cortices, with the effect being larger in the right hemisphere. These results are in line with previous reports of right-lateralized pitch processing. In the passive listening condition, we found no differences between the perturbation and the control trials. This suggests that the ERF responses were not merely driven by the pitch change in the auditory input and hence instead reflect speech production processes. We suggest the observed ERF responses in sensorimotor cortex are an index of the mismatch between the self-generated forward model prediction of auditory input and the incoming auditory signal.

Abstract

Speakers and listeners do more than exchanging propositional content. They try to get things done with their utterances. For speakers this requires planning of utterances with knowledge about the listener in mind, whereas listeners need to make inferences that go beyond simulating sensorimotor aspects of propositional content. For example, the statement "It is hot in here" will usually not be answered with a statement of the kind "Yes, indeed it is 32 degrees Celsius", but rather with the answer "I will open the window", since the listener infers the speaker's intention behind her statement. I will discuss a series of studies that identify the network of brain regions involved in audience design and inferring speaker meaning. Likewise for indirect replies that require conversational implicatures, as in A: "Did you like my talk?" to which B replies: "It is hard to give a good presentation." I will show that in these cases the core language network needs to be extended with brain systems providing the necessary inferential machinery

Abstract

Studies of sound symbolism have shown that people can associate sound and meaning in consistent ways when presented with maximally contrastive stimulus pairs of nonwords such as bouba/kiki (rounded/sharp) or mil/mal (small/big). Recent work has shown the effect extends to antonymic words from natural languages and has proposed a role for shared cross-modal correspondences in biasing form-to-meaning associations. An important open question is how the associations work, and particularly what the role is of sound-symbolic matches versus mismatches. We report on a learning task designed to distinguish between three existing theories by using a spectrum of sound-symbolically matching, mismatching, and neutral (neither matching nor mismatching) stimuli. Synthesized stimuli allow us to control for prosody, and the inclusion of a neutral condition allows a direct test of competing accounts. We find evidence for a sound-symbolic match boost, but not for a mismatch difficulty compared to the neutral condition.

Abstract

This study aims to test recent theoretical frameworks in speech motor control which claim that speech production targets are specified in auditory terms. According to such frameworks, people with better auditory acuity should have more precise speech targets. Participants performed speech perception and production tasks in a counterbalanced order. Speech perception acuity was assessed using an adaptive speech discrimination task, where participants discriminated between stimuli on a /ɪ/-/ɛ/ and a /ɑ/-/ɔ/ continuum. To assess variability in speech production, participants performed a pseudo-word reading task; formant values were measured for each recording of the vowels /ɪ/, /ɛ/, /ɑ/ and /ɔ/ in 288 pseudowords (18 per vowel, each of which was repeated 4 times). We predicted that speech production variability would correlate inversely with discrimination performance. Results confirmed this prediction as better discriminators had more distinctive vowel production targets. In addition, participants with higher auditory acuity produced vowels with smaller within-phoneme variability but spaced farther apart in vowel space. This study highlights the importance of individual differences in the study of speech motor control, and sheds light on speech production-perception interactions.