244 research outputs found
Figure-ground processing in the auditory cortex of the macaque monkey
Ph. D. Thesis.Natural sensory scenes are often very complex, with a multitude of overlapping
objects in space and time. In order to direct behaviour, a critical aspect of everyday
perception is the segregation and grouping of relevant features from those scenes,
known as figure-ground segregation. The neurobiological basis of auditory figureground processing is poorly understood. To gain insights into different aspects of this
process, I have investigated the behavioural, systemic and neuronal mechanisms the
brain uses to segregate and group temporally coherent elements from a complex
acoustic scene in macaque monkeys.
This thesis presents the result of this research in five chapters: Chapter 1
reviews the fundamental basics of auditory scene analysis and the auditory system.
Chapter 2, 3 and 4 present experimental work and cover figure detection behaviour
(Chapter 2), systemic organisation of figure-ground analysis (Chapter 3) and the
underlying neuronal mechanisms (Chapter 4). Finally, Chapter 5 discusses and
interprets the results in the context of previous research.
In summary, this work establishes that macaques are an excellent animal
model for auditory scene analysis and provides new evidence of the cortical response
mechanisms during auditory figure-ground segregation. I show that macaques have
not only similar detection performance to humans but that the areal organisation
measured with fMRI is comparable. Furthermore, I demonstrate robust effects on
neuronal firing rates in response to auditory figures across the cortical hierarchy.
Lastly, this thesis establishes neuronal differences in figure processing between
anterior and posterior auditory cortical fields
From the Richness of the Signal to the Poverty of the Stimulus: Mechanisms of Early Language Acquisition
1.1 The poverty of stimulus argument and the learnability of lan-guage................................ 12 1.1.1 The induction problem.................. 1
Prediction-driven computational auditory scene analysis
The sound of a busy environment, such as a city street, gives rise to a perception of numerous distinct events in a human listener--the 'auditory scene analysis' of the acoustic information. Recent advances in the understanding of this process from experimental psychoacoustics have led to several efforts to build a computer model capable of the same function. This work is known as 'computational auditory scene analysis'. The dominant approach to this problem has been as a sequence of modules, the output of one forming the input to the next. Sound is converted to its spectrum, cues are picked out, and representations of the cues are grouped into an abstract description of the initial input. This 'data-driven' approach has some specific weaknesses in comparison to the auditory system: it will interpret a given sound in the same way regardless of its context, and it cannot 'infer' the presence of a sound for which direct evidence is hidden by other components. The 'prediction-driven' approach is presented as an alternative, in which analysis is a process of reconciliation between the observed acoustic features and the predictions of an internal model of the sound-producing entities in the environment. In this way, predicted sound events will form part of the scene interpretation as long as they are consistent with the input sound, regardless of whether direct evidence is found. A blackboard-based implementation of this approach is described which analyzes dense, ambient sound examples into a vocabulary of noise clouds, transient clicks, and a correlogram-based representation of wide-band periodic energy called the weft. The system is assessed through experiments that firstly investigate subjects' perception of distinct events in ambient sound examples, and secondly collect quality judgments for sound events resynthesized by the system. Although rated as far from perfect, there was good agreement between the events detected by the model and by the listeners. In addition, the experimental procedure does not depend on special aspects of the algorithm (other than the generation of resyntheses), and is applicable to the assessment and comparison of other models of human auditory organization
Effects of errorless learning on the acquisition of velopharyngeal movement control
Session 1pSC - Speech Communication: Cross-Linguistic Studies of Speech Sound Learning of the Languages of Hong Kong (Poster Session)The implicit motor learning literature suggests a benefit for learning if errors are minimized during practice. This study investigated whether the same principle holds for learning velopharyngeal movement control. Normal speaking participants learned to produce hypernasal speech in either an errorless learning condition (in which the possibility for errors was limited) or an errorful learning condition (in which the possibility for errors was not limited). Nasality level of the participants’ speech was measured by nasometer and reflected by nasalance scores (in %). Errorless learners practiced producing hypernasal speech with a threshold nasalance score of 10% at the beginning, which gradually increased to a threshold of 50% at the end. The same set of threshold targets were presented to errorful learners but in a reversed order. Errors were defined by the proportion of speech with a nasalance score below the threshold. The results showed that, relative to errorful learners, errorless learners displayed fewer errors (50.7% vs. 17.7%) and a higher mean nasalance score (31.3% vs. 46.7%) during the acquisition phase. Furthermore, errorless learners outperformed errorful learners in both retention and novel transfer tests. Acknowledgment: Supported by The University of Hong Kong Strategic Research Theme for Sciences of Learning © 2012 Acoustical Society of Americapublished_or_final_versio
Neural and computational approaches to auditory scene analysis
Our perception of the world is highly dependent on the complex processing of the sensory inputs by the brain. Hearing is one of those seemingly effortless sensory tasks that enables us to perceive the auditory world and integrate acoustic information from the environment into cognitive experiences. The main purpose of studying auditory system is to shed light on the neural mechanisms underlying our hearing ability. Understanding the systematic approach of the brain in performing such complicated tasks is an ultimate goal with numerous clinical and intellectual applications.
In this thesis, we take advantage of various experimental and computational approaches to understand the functionality of the brain in analyzing complex auditory scenes. We first focus on investigating the behavioral and neural mechanisms underlying auditory sound segregation, also known as auditory streaming. Employing an informational masking paradigm, we explore the interaction between stimulus-driven and task-driven attentional process in the auditory cortex using magnetoencephalography (MEG) recordings from the human brain. The results demonstrate close links between perceptual and neural consequences of the auditory stream segregation, suggesting the neural activity to be viewed as an indicator of the auditory streaming percept.
We examine more realistic auditory scenarios consisted of two speakers simultaneously present in an auditory scene and introduce a novel computational approach for decoding the attentional state of listeners in such environment. The proposed model focuses on an efficient implementation of a decoder for tracking the cognitive state of the brain, inspired from neural representation of auditory objects in the auditory cortex. The structure is based on an state-space model with the recorded MEG signal and individual speech envelopes as the input and the probability of attending to the target speaker as the output of the model. The proposed approach benefits from accurate and highly resolved estimation of attentional state in time as well as the inherent model-based dynamic denoising of the underlying state-space model, which makes it possible to reliably decode the attentional state under very low SNR conditions.
As part of this research work, we investigate the neural representation of ambiguous auditory stimuli at the level of the auditory cortex. In perceiving a typical auditory scene, we may receive incomplete or ambiguous auditory information from the environment. This can lead to multiple interpretations of the same acoustic scene and formation of an ambitious perceptual state in the brain. Here, in a series of experimental studies, we focus on a particular example of ambitious stimulus (ambitious Shepard tone pair) and investigate the neural correlates of the contextual effect and perceptual biasing using MEG. The results from psychoacoustic and neural recordings suggest a set of hypothesis about the underlying neural mechanism of short-term memory and expectation modulation in the nervous system
A primate model of human cortical analysis of auditory objects
PhD ThesisThe anatomical organization of the auditory cortex in old world monkeys is similar to that in humans. But how good are monkeys as a model of human cortical analysis of auditory objects? To address this question I explore two aspects of auditory objectprocessing: segregation and timbre. Auditory segregation concerns the ability of animals to extract an auditory object of relevance from a background of competing sounds. Timbre is an aspect of object identity distinct from pitch. In this work, I study these phenomena in rhesus macaques using behaviour and functional magnetic resonance imaging (fMRI). I specifically manipulate one dimension of timbre, spectral flux: the rate of change of spectral energy.I present this thesis in five chapters. Chapter 1 presents background on auditory processing, macaque auditory cortex, models of auditory segregation, and dimensions of timbre. Chapter 2 presents an introduction to fMRI, the design of the fMRI experiments and analysis of fMRI data, and macaque behavioural training techniques employed. Chapter 3 presents results from the fMRI and behavioural experiments on macaques using a stochastic figure-ground stimulus. Chapter 4 presents the results from the fMRI experiment in macaques using spectral flux stimulus. Chapter 5 concludes with a general discussion of the results from both the studies and some future directions for research.In summary, I show that there is a functional homology between macaques and humans in the cortical processing of auditory figure-ground segregation. However, there is no clear functional homology in the processing of spectral flux between these species. So I conclude that, despite clear similarities in the organization of the auditory cortex and processing of auditory object segregation, there are important differences in how complex cues associated with auditory object identity are processed in the macaque and human auditory brains.Wellcome Trust U
Model of models -- Part 1
This paper proposes a new cognitive model, acting as the main component of an
AGI agent. The model is introduced in its mature intelligence state, and as an
extension of previous models, DENN, and especially AKREM, by including
operational models (frames/classes) and will. This model's core assumption is
that cognition is about operating on accumulated knowledge, with the guidance
of an appropriate will. Also, we assume that the actions, part of knowledge,
are learning to be aligned with will, during the evolution phase that precedes
the mature intelligence state. In addition, this model is mainly based on the
duality principle in every known intelligent aspect, such as exhibiting both
top-down and bottom-up model learning, generalization verse specialization, and
more. Furthermore, a holistic approach is advocated for AGI designing, and
cognition under constraints or efficiency is proposed, in the form of
reusability and simplicity. Finally, reaching this mature state is described
via a cognitive evolution from infancy to adulthood, utilizing a consolidation
principle. The final product of this cognitive model is a dynamic operational
memory of models and instances. Lastly, some examples and preliminary ideas for
the evolution phase to reach the mature state are presented.Comment: arXiv admin note: text overlap with arXiv:2301.1355
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