106 research outputs found
Recommended from our members
Auditory, Visual, and Speech Category Learning in the Same Individuals
Category learning is a fundamental process in human cognition. Recent efforts have attempted to adapt theories developedin vision to the auditory domain. However, no study has directly compared auditory and visual category learning in thesame individuals. Using a fully within-subjects approach, we trained participants on non-speech auditory, visual, andnon-native speech categories in a single day. By comparing category learning behavior, the ability to generalize to novelcategory exemplars, and leveraging decision bound computational models, we found that while individuals demonstratedsimilar learning across the auditory and visual modalities, there were distinct perceptual biases that influenced learning ofnon-speech auditory categories. Further, there were substantial individual differences in performance across the three tasks.This study presents a novel comparison of category learning across modalities in the same individuals and demonstratesthat although commonalities exist, there is some domain-specificity to category learning
Bayesian Mixed Multidimensional Scaling for Auditory Processing
The human brain distinguishes speech sound categories by representing
acoustic signals in a latent multidimensional auditory-perceptual space. This
space can be statistically constructed using multidimensional scaling, a
technique that can compute lower-dimensional latent features representing the
speech signals in such a way that their pairwise distances in the latent space
closely resemble the corresponding distances in the observation space. The
inter-individual and inter-population (e.g., native versus non-native
listeners) heterogeneity in such representations is however not well
understood. These questions have often been examined using joint analyses that
ignore individual heterogeneity or using separate analyses that cannot
characterize human similarities. Neither extreme, therefore, allows for
principled comparisons between populations and individuals. The focus of the
current literature has also often been on inference on latent distances between
the categories and not on the latent features themselves, which are crucial for
our applications, that make up these distances. Motivated by these problems, we
develop a novel Bayesian mixed multidimensional scaling method, taking into
account the heterogeneity across populations and subjects. We design a Markov
chain Monte Carlo algorithm for posterior computation. We then recover the
latent features using a post-processing scheme applied to the posterior
samples. We evaluate the method's empirical performances through synthetic
experiments. Applied to a motivating auditory neuroscience study, the method
provides novel insights into how biologically interpretable lower-dimensional
latent features reconstruct the observed distances between the stimuli and vary
between individuals and their native language experiences
Context-Dependent Encoding in the Human Auditory Brainstem Relates to Hearing Speech in Noise: Implications for Developmental Dyslexia
SummaryWe examined context-dependent encoding of speech in children with and without developmental dyslexia by measuring auditory brainstem responses to a speech syllable presented in a repetitive or variable context. Typically developing children showed enhanced brainstem representation of features related to voice pitch in the repetitive context, relative to the variable context. In contrast, children with developmental dyslexia exhibited impairment in their ability to modify representation in predictable contexts. From a functional perspective, we found that the extent of context-dependent encoding in the auditory brainstem correlated positively with behavioral indices of speech perception in noise. The ability to sharpen representation of repeating elements is crucial to speech perception in noise, since it allows superior âtaggingâ of voice pitch, an important cue for segregating sound streams in background noise. The disruption of this mechanism contributes to a critical deficit in noise-exclusion, a hallmark symptom in developmental dyslexia
Examining cortical tracking of the speech envelope in post-stroke aphasia
IntroductionPeople with aphasia have been shown to benefit from rhythmic elements for language production during aphasia rehabilitation. However, it is unknown whether rhythmic processing is associated with such benefits. Cortical tracking of the speech envelope (CTenv) may provide a measure of encoding of speech rhythmic properties and serve as a predictor of candidacy for rhythm-based aphasia interventions.MethodsElectroencephalography was used to capture electrophysiological responses while Spanish speakers with aphasia (nâ=â9) listened to a continuous speech narrative (audiobook). The Temporal Response Function was used to estimate CTenv in the delta (associated with word- and phrase-level properties), theta (syllable-level properties), and alpha bands (attention-related properties). CTenv estimates were used to predict aphasia severity, performance in rhythmic perception and production tasks, and treatment response in a sentence-level rhythm-based intervention.ResultsCTenv in delta and theta, but not alpha, predicted aphasia severity. Neither CTenv in delta, alpha, or theta bands predicted performance in rhythmic perception or production tasks. Some evidence supported that CTenv in theta could predict sentence-level learning in aphasia, but alpha and delta did not.ConclusionCTenv of the syllable-level properties was relatively preserved in individuals with less language impairment. In contrast, higher encoding of word- and phrase-level properties was relatively impaired and was predictive of more severe language impairments. CTenv and treatment response to sentence-level rhythm-based interventions need to be further investigated
Internal Flow Choking in Cardiovascular System: A Radical Theory in the Risk Assessment of Asymptomatic Cardiovascular Diseases
The theoretical discovery of Sanal flow choking in the cardiovascular system (CVS) demands for interdisciplinary studies and universal actions to propose modern medications and to discover new drugs to annul the risk of flow-choking leading to shock-wave generation causing asymptomatic-cardiovascular-diseases. In this chapter we show that when blood-pressure-ratio (BPR) reaches the lower-critical-hemorrhage-index (LCHI) the flow-choking could occur in the CVS with and without stent. The flow-choking is uniquely regulated by the biofluid/blood-heat-capacity-ratio (BHCR). The BHCR is well correlated with BPR, blood-viscosity and ejection-fraction. The closed-form analytical models reveal that the relatively high and the low blood-viscosity are cardiovascular-risk factors. In vitro data shows that nitrogen, oxygen, and carbon dioxide gases are predominant in fresh blood samples of the human being/Guinea-pig at a temperature range of 37â40 °C (98.6â104 °F). In silico results demonstrate the occurrence of Sanal flow choking leading to shock wave generation and pressure-overshoot in CVS without any apparent occlusion. We could conclude authoritatively, without any ex vivo or in vivo studies, that the Sanal flow choking in CVS leads to asymptomatic-cardiovascular-diseases. The cardiovascular-risk could be diminished by concurrently lessening the viscosity of biofluid/blood and flow-turbulence by increasing the thermal-tolerance level in terms of BHCR and/or by decreasing the BPR
The Derived Allele of ASPM Is Associated with Lexical Tone Perception
The ASPM and MCPH1 genes have been implicated in the adaptive evolution of the human brain [Mekel-Bobrov N. et al., 2005. Ongoing adaptive evolution of ASPM, a brain size determinant in homo sapiens. Science 309; Evans P.D. et al., 2005. Microcephalin, a gene regulating brain size, continues to evolve adaptively in humans. Science 309]. Curiously, experimental attempts have failed to connect the implicated SNPs in these genes with higher-level brain functions. These results stand in contrast with a population-level study linking the population frequency of their alleles with the tendency to use lexical tones in a language [Dediu D., Ladd D.R., 2007. Linguistic tone is related to the population frequency of the adaptive haplogroups of two brain size genes, ASPM and microcephalin. Proc. Natl. Acad. Sci. U.S.A. 104]. In the present study, we found a significant correlation between the load of the derived alleles of ASPM and tone perception in a group of European Americans who did not speak a tone language. Moreover, preliminary results showed a significant correlation between ASPM load and hemodynamic responses to lexical tones in the auditory cortex, and such correlation remained after phonemic awareness, auditory working memory, and non-verbal IQ were controlled. As in previous studies, no significant correlation between ASPM and cognitive measures were found. MCPH1 did not correlate with any measures. These results suggest that the association between the recently derived allele of ASPM is likely to be specific and is tied to higher level brain functions in the temporal cortex related to human communication
A Panorama on Multiscale Geometric Representations, Intertwining Spatial, Directional and Frequency Selectivity
The richness of natural images makes the quest for optimal representations in
image processing and computer vision challenging. The latter observation has
not prevented the design of image representations, which trade off between
efficiency and complexity, while achieving accurate rendering of smooth regions
as well as reproducing faithful contours and textures. The most recent ones,
proposed in the past decade, share an hybrid heritage highlighting the
multiscale and oriented nature of edges and patterns in images. This paper
presents a panorama of the aforementioned literature on decompositions in
multiscale, multi-orientation bases or dictionaries. They typically exhibit
redundancy to improve sparsity in the transformed domain and sometimes its
invariance with respect to simple geometric deformations (translation,
rotation). Oriented multiscale dictionaries extend traditional wavelet
processing and may offer rotation invariance. Highly redundant dictionaries
require specific algorithms to simplify the search for an efficient (sparse)
representation. We also discuss the extension of multiscale geometric
decompositions to non-Euclidean domains such as the sphere or arbitrary meshed
surfaces. The etymology of panorama suggests an overview, based on a choice of
partially overlapping "pictures". We hope that this paper will contribute to
the appreciation and apprehension of a stream of current research directions in
image understanding.Comment: 65 pages, 33 figures, 303 reference
Experience-dependent plasticity in the preattentive processing of linguistic pitch contours: Evidence from crosslanguage and crossdomain studies
Using the mismatch negativity (MMN), a cortical index of preattentive change-detection, it is well established that language experience influences the automatic cortical processing of segmental information in speech, i.e. consonants and vowels. The studies included in this dissertation shed light on the nature and limits of experience-dependent plasticity related to processing of linguistic pitch, a suprasegmental cue. Study 1 measured MMN responses from Chinese and English listeners listening to sequences of Mandarin tones in a speech context. The results suggest that cortical processing of linguistic pitch contours may be shaped by the saliency of acoustic dimensions underlying the pitch patterns of a particular language. Study 2 examined the number and relative weighting of dimensions underlying the preattentive processing of lexical tones by applying multidimensional scaling (MDS) analysis on the MMN responses from Chinese and English listeners. MDS revealed two dimensions common to Chinese and English, interpretively labeled as âheightâ and âcontour.â The âcontourâ dimension was found to be more important for Chinese than English participants suggesting that specific pitch dimensions are differentially weighted by language experience. In study 3, we examined whether experience-dependent plasticity is specific to speech by eliciting MMN responses to nonspeech iterative ripple noise (IRN) stimuli in a crosslanguage (Chinese, English) design. Results from support the notion that experience-dependent plasticity is not restricted to the speech-domain. Study 4, using a crosslanguage design, explored the extent to which acoustic versus phonetic change detection processes contribute to experience-dependent plasticity of linguistic pitch contours at attention-dependent and preattentive stages of processing. Findings suggest that acoustic features of pitch contours, regardless of their categorical status, may drive experience-dependent neural plasticity at early cortical stages of processing. At attentive stages of processing, however, perception is strongly influenced by tonal categories. Studies 5 and 6 were designed to examine whether neuroplasticity to linguistic pitch is domain-specific. The two studies examined MMN responses in a cross-domain design (Chinese, musicians) to nonspeech Mandarin linear and curvilinear pitch contours. Results show that neuroplasticity to time-varying pitch contours is highly sensitive to the context of the long-term experience (music vs. language)
- âŠ