Reweighting Of Cues Research Articles

Apparent-time variation in the use of multiple cues for perception of anticipatory nasal coarticulation in California English

This study examines apparent-time variation in the use of multiple acoustic cues present on coarticulatorily nasalized vowels in California English. Eighty-nine listeners ranging in age from 18-58 (grouped into 3 apparent-time categories based on year of birth) performed lexical identifications on syllables excised from words with oral and nasal codas from six speakers who produced either minimal (n=3) or extensive (n=3) anticipatory nasal coarticulation (realized by greater vowel nasalization, F1 bandwidth, and diphthongization on vowels in CVN contexts). Results showed no differences across listeners’ identification for Extensively coarticulated vowels, as well as oral vowels by both types of speakers (all at-ceiling). Yet, performance for the Minimal Coarticulators’ nasalized vowels was lowest for the older listener group and increased over apparent-time. Perceptual cue-weighting analyses revealed that older listeners rely more on F1 bandwidth, while younger listeners rely more on acoustic nasality, as coarticulatory cues providing information about lexical identity. Thus, there is evidence for variation in apparent- time in the use of the different coarticulatory cues present on vowels. Younger listeners’ cue weighting allows them flexibility to identify lexical items given a range of coarticulatory variation across (here, younger) speakers, while older listeners’ cue weighting leads to reduced performance for talkers producing innovative phonetic forms. This study contributes to our understanding of the relationship between multidimensional acoustic features resulting from coarticulation and the perceptual re-weighting of cues that can lead to sound change over time.

How prior experience with pitch accents shapes the perception of word and sentence stress

ABSTRACT Listeners perceive high or rising pitch as stressed – at the word and sentence level (high-pitch bias). Since stressed syllables can also be low-pitched, this bias may lead to misinterpretations of word and sentence stress and thus slow down speech comprehension. We investigate the effect of immediate exposure with high- vs. low-pitched stressed syllables on the identification of word and sentence stress. Participants were exposed to utterances containing only high- vs. low-pitched stressed syllables. In experimental trials, they then heard either trisyllabic words with word stress on the second syllable (Experiment 1) or three-word-sentences with sentence stress on the second word (Experiment 2) and indicated the position of word/sentence stress. Stimuli were presented in three intonation conditions (high-pitched first, second, or third syllable/word). Both experiments endorsed the high-pitch bias, with an increase after high-pitch exposure. Our results suggest a speaker-independent re-weighting of acoustic cues to stress, which is driven by experience.

Dynamic re-weighting of acoustic and contextual cues in spoken word recognition.

Listeners integrate acoustic and contextual cues during word recognition. However, experiments investigating this integration disrupt natural cue correlations. It was investigated whether changes in correlational structure affect listeners' relative cue weightings. Two groups of participants engaged in a word recognition task. In one group, acoustic (voice onset time) and contextual (lexical bias) cues followed natural correlations; in the other, cues were uncorrelated. When cues were correlated, cue weights were stable throughout the experiment; when cues were uncorrelated, contextual cues were down-weighted. Listeners thus can re-weight cues based on their statistical structure. Studies failing to account for re-weighting risk over/under-estimating cue importance.

Silencing cortical activity during sound-localization training impairs auditory perceptual learning

The brain has a remarkable capacity to adapt to changes in sensory inputs and to learn from experience. However, the neural circuits responsible for this flexible processing remain poorly understood. Using optogenetic silencing of ArchT-expressing neurons in adult ferrets, we show that within-trial activity in primary auditory cortex (A1) is required for training-dependent recovery in sound-localization accuracy following monaural deprivation. Because localization accuracy under normal-hearing conditions was unaffected, this highlights a specific role for cortical activity in learning. A1-dependent plasticity appears to leave a memory trace that can be retrieved, facilitating adaptation during a second period of monaural deprivation. However, in ferrets in which learning was initially disrupted by perturbing A1 activity, subsequent optogenetic suppression during training no longer affected localization accuracy when one ear was occluded. After the initial learning phase, the reweighting of spatial cues that primarily underpins this plasticity may therefore occur in A1 target neurons.

Age-related reweighting of visual and vestibular cues for vertical perception.

As we age, the acuity of our sensory organs declines, which may affect our lifestyle. Sensory deterioration in the vestibular system is typically bilateral and gradual, and could lead to problems with balance and spatial orientation. To compensate for the sensory deterioration, it has been suggested that the brain reweights the sensory information sources according to their relative noise characteristics. For rehabilitation and training programs, it is important to understand the consequences of this reweighting, preferably at the individual subject level. We psychometrically examined the age-dependent reweighting of visual and vestibular cues used in spatial orientation in a group of 32 subjects (age range: 19-76 yr). We asked subjects to indicate the orientation of a line (clockwise or counterclockwise relative to the gravitational vertical) presented within an oriented square visual frame when seated upright or with their head tilted 30° relative to the body. Results show that subjects' vertical perception is biased by the orientation of the visual frame. Both the magnitude of this bias and response variability become larger with increasing age. Deducing the underlying sensory noise characteristics, using Bayesian inference, suggests an age-dependent reweighting of sensory information, with an increasing weight of the visual contextual information. Further scrutiny of the model suggests that this shift in sensory weights is the result of an increase in the noise of the vestibular signal. Our approach quantifies how noise properties of visual and vestibular systems change over the life span, which helps to understand the aging process at the neurocomputational level. NEW & NOTEWORTHY Perception of visual vertical involves a weighted fusion of visual and vestibular tilt cues. Using a Bayesian approach and experimental psychophysics, we quantify how this fusion process changes with age. We show that, with age, the vestibular information is down-weighted whereas the visual weight is increased. This shift in sensory reweighting is primarily due to an age-related increase of the noise of vestibular signals.

Critical Role of Somatosensation in Postural Control Following Spaceflight: Vestibularly Deficient Astronauts Are Not Able to Maintain Upright Stance During Compromised Somatosensation.

The free-fall of orbital spaceflight effectively removes the gravitational vector used as a primary spatial orientation reference on Earth. Sustained absence of this reference drives adaptive changes in the internal perception-action models of the central nervous system (CNS), most notably in the processing of the vestibular otolith inputs. Upon landing, the return of the gravitational signal triggers a re-adaptation that restores terrestrial performance; however, during this period, the individual suffers from a functional vestibular deficiency. Here we provide evidence of a transient increase of the weighting of somatosensory inputs in postural control while the CNS resolves these vestibular deficiencies. Postural control performance was measured before and after spaceflight in 11 Shuttle astronauts and 11 matched controls and nine elderly who did not experience spaceflight. A quiet-stance paradigm was used that eliminated vision, modulated the lower extremity somatosensory cues by subtly modulating the orientation of the support surface beneath feet of subjects in all groups. Additionally, in astronauts and matched controls, we challenged the vestibular system with dynamic head tilts. Postural stability on the landing day (R+0) was substantially decreased for trials with absent visual and altered somatosensory cues, especially those also requiring dynamic head tilts ( ± 5° @ 0.33 Hz) during which 20/22 trials ended prematurely with a fall. In contrast, none of the astronauts fell during eyes-closed, dynamic head tilt trials with unaltered somatosensory cues, and only 3/22 trials resulted in falls with eyes-closed and altered somatosensory cues, but static upright head orientation. Furthermore, postural control performance of astronauts was either statistically not different or worse than that of healthy elderly subjects during the most challenging vestibular conditions on R+0. Overall, our results demonstrate a transient reweighting of sensory cues associated with microgravity-induced vestibular deficiencies, with a significant increase in reliance on somatosensory cues, which can provide an effective reference even without vision and with dynamic vestibular challenges. The translation of these results to aging population suggests that elderly individuals with visual and vestibular deficits may benefit from therapeutic interventions enhancing sensorimotor-integration to improve balance and reduce the risk of falling.

Bayes-Like Integration of a New Sensory Skill with Vision

Humans are effective at dealing with noisy, probabilistic information in familiar settings. One hallmark of this is Bayesian Cue Combination: combining multiple noisy estimates to increase precision beyond the best single estimate, taking into account their reliabilities. Here we show that adults also combine a novel audio cue to distance, akin to human echolocation, with a visual cue. Following two hours of training, subjects were more precise given both cues together versus the best single cue. This persisted when we changed the novel cue’s auditory frequency. Reliability changes also led to a re-weighting of cues without feedback, showing that they learned something more flexible than a rote decision rule for specific stimuli. The main findings replicated with a vibrotactile cue. These results show that the mature sensory apparatus can learn to flexibly integrate new sensory skills. The findings are unexpected considering previous empirical results and current models of multisensory learning.

Vision-induced reweighting of binaural localization cues

Normal-hearing listeners apply frequency-dependent weights when combining the two binaural cues (interaural time and level difference, ITD and ILD) to determine the perceived sound source azimuth. Cochlear-implant (CI) listeners, however, rely almost entirely on ILDs. Since current CI systems do not reliably convey ITD information, CI listeners might learn to ignore ITDs and focus on ILDs instead. We investigated whether this reweighting of binaural cues is generally possible. 20 normal-hearing participants, assigned to two groups, completed an experiment in a virtual audio-visual environment. The experiment consisted of a pre-test to establish the initial ITD/ILD weights, a seven-day training, in which visual feedback reinforced one of the cues, and a post-test to measure the effect of training on the weights. Participants’ task was to lateralize octave-wide bands of noise (centered at 2.8 kHz) containing various combinations of spatially inconsistent ITD and ILD. In both groups, the lateralization bias ...

Short-term visual deprivation reduces interference effects of task-irrelevant facial expressions on affective prosody judgments.

Several studies have suggested that neuroplasticity can be triggered by short-term visual deprivation in healthy adults. Specifically, these studies have provided evidence that visual deprivation reversibly affects basic perceptual abilities. The present study investigated the long-lasting effects of short-term visual deprivation on emotion perception. To this aim, we visually deprived a group of young healthy adults, age-matched with a group of non-deprived controls, for 3 h and tested them before and after visual deprivation (i.e., after 8 h on average and at 4 week follow-up) on an audio–visual (i.e., faces and voices) emotion discrimination task. To observe changes at the level of basic perceptual skills, we additionally employed a simple audio–visual (i.e., tone bursts and light flashes) discrimination task and two unimodal (one auditory and one visual) perceptual threshold measures. During the 3 h period, both groups performed a series of auditory tasks. To exclude the possibility that changes in emotion discrimination may emerge as a consequence of the exposure to auditory stimulation during the 3 h stay in the dark, we visually deprived an additional group of age-matched participants who concurrently performed unrelated (i.e., tactile) tasks to the later tested abilities. The two visually deprived groups showed enhanced affective prosodic discrimination abilities in the context of incongruent facial expressions following the period of visual deprivation; this effect was partially maintained until follow-up. By contrast, no changes were observed in affective facial expression discrimination and in the basic perception tasks in any group. These findings suggest that short-term visual deprivation per se triggers a reweighting of visual and auditory emotional cues, which seems to possibly prevail for longer durations.

Dynamic Reweighting of Visual and Vestibular Cues during Self-Motion Perception

The perception of self-motion direction, or heading, relies on integration of multiple sensory cues, especially from the visual and vestibular systems. However, the reliability of sensory information can vary rapidly and unpredictably, and it remains unclear how the brain integrates multiple sensory signals given this dynamic uncertainty. Human psychophysical studies have shown that observers combine cues by weighting them in proportion to their reliability, consistent with statistically optimal integration schemes derived from Bayesian probability theory. Remarkably, because cue reliability is varied randomly across trials, the perceptual weight assigned to each cue must change from trial to trial. Dynamic cue reweighting has not been examined for combinations of visual and vestibular cues, nor has the Bayesian cue integration approach been applied to laboratory animals, an important step toward understanding the neural basis of cue integration. To address these issues, we tested human and monkey subjects in a heading discrimination task involving visual (optic flow) and vestibular (translational motion) cues. The cues were placed in conflict on a subset of trials, and their relative reliability was varied to assess the weights that subjects gave to each cue in their heading judgments. We found that monkeys can rapidly reweight visual and vestibular cues according to their reliability, the first such demonstration in a nonhuman species. However, some monkeys and humans tended to over-weight vestibular cues, inconsistent with simple predictions of a Bayesian model. Nonetheless, our findings establish a robust model system for studying the neural mechanisms of dynamic cue reweighting in multisensory perception.

Effects of audiovisual auditory and articulatory training on second‐language (L2) vowel category learning.

Cross‐language speech perception research has documented learners’ difficulties in using and accessing L2 durational and spectral information. This study investigated the short‐term effects of two types of audiovisual high‐variability phonetic training—auditory versus articulatory training—on the perception of the 11 English RP monophthongal vowels. Bilingual Catalan/Spanish learners of English (N=20 in each training condition) and one control group (N=20) were tested before and after training. Perceptual gains were assessed through a four‐choice categorization task with natural CVC words, a forced‐choice categorization task based on four synthesized /hVd/ continua (/i:/‐/ɪ/, /æ/‐/ʌ/, /ʌ/‐/ɑ:/ and /u:/‐/U/), and an AX discrimination task including 16 contrasting pairs. Significant perceptual accuracy gains were obtained in both auditory and audiovisual conditions. Pre‐ and postcategorization of synthesized vowels suggests that vowel perception improved, and that both training modalities had a similar positive effect on the learners’ use of spectral and duration information in vowel categorization. These results are further discussed in terms of input effects on vowel category learning and the reweighting of acoustic cues through phonetic training.

Re-weighting of somatosensory inputs from the foot and the ankle for controlling posture during quiet standing following trunk extensor muscles fatigue

The present study focused on the effects of trunk extensor muscles fatigue on postural control during quiet standing under different somatosensory conditions from the foot and the ankle. With this aim, 20 young healthy adults were asked to stand as immobile as possible in two conditions of No fatigue and Fatigue of trunk extensor muscles. In Experiment 1 (n = 10), somatosensation from the foot and the ankle was degraded by standing on a foam surface. In Experiment 2 (n = 10), somatosensation from the foot and ankle was facilitated through the increased cutaneous feedback at the foot and ankle provided by strips of athletic tape applied across both ankle joints. The centre of foot pressure displacements (CoP) were recorded using a force platform. The results showed that (1) trunk extensor muscles fatigue increased CoP displacements under normal somatosensatory conditions (Experiment 1 and Experiment 2), (2) this destabilizing effect was exacerbated when somatosensation from the foot and the ankle was degraded (Experiment 1), and (3) this destabilizing effect was mitigated when somatosensation from the foot and the ankle was facilitated (Experiment 2). Altogether, the present findings evidenced re-weighting of sensory cues for controlling posture during quiet standing following trunk extensor muscles fatigue by increasing the reliance on the somatosensory inputs from the foot and the ankle. This could have implications in clinical and rehabilitative areas.

Perceptual processing of multiple cues and contexts: effects of following vowel upon stop consonant voicing

Variations in vowel context affect values of the acoustical variables that function as perceptual cues for the voicing distinction in initial stop consonants in English. Processing these context-dependent variations is a basic problem in speech perception. Of the several acoustical correlates of voicing that may be considered cues, two major ones are examined here, previously conflated in the Voice Onset Time concept: the first is the time from the burst to the first voicing pulse and is measured as the separation of these two events; the second is the relative position in the formant transition frame at which voicing onsets and is measured as the amount of voiced first formant (F1) transition. An experiment is reported which shows that for velar stops before /a/ both cues play a role in voicing perception although the transition cue is dominant. For velar stops before /i/, where no F1 transition occurs, the separation cue appears more important than it does in /a/ context. Consideration of these results points to the need to distinguish between contextual adjustments involving a simple boundary shift and those involving a reweighting of cues according to context. The two cues used here appear to be of different types with attendant differences in the effects they generate in perception experiments. In particular a sophisticated view of the processing of different cues may be necessary to give an account of adaptation in the voicing feature in experiments where the percentage of voiced or unvoiced responses is modified following repeated exposure to a stimulus with a distinct value of the feature.