5,095 research outputs found
Coping with speaker-related variation via abstract phonemic categories
Listeners can cope with considerable variation in the way that different speakers talk. We argue here that they can do so because of a process of phonological abstraction in the speech-recognition system. We review evidence that listeners adjust the bounds of phonemic categories after only very limited exposure to a deviant realisation of a given phoneme. This learning can be talker-specific and is stable over time; further, the learning generalizes to previously unheard words containing the deviant phoneme. Together these results suggest that the learning involves adjustment of prelexical phonemic representations which mediate between the speech signal and the mental lexicon during word recognition. We argue that such an abstraction process is inconsistent with claims made by some recent models of language processing that the mental lexicon consists solely of multiple detailed traces of acoustic episodes. Simulations with a purely episodic model without functional prelexical abstraction confirm that such a model cannot account for the evidence on lexical generalization of perceptual learning. We conclude that abstract phonemic categories form a necessary part of lexical access, and that the ability to store talker-specific knowledge about those categories provides listeners with the means to deal with cross-talker variation
Perceptual learning in speech
Definition Perceptual learning in speech describes a change in the mapping from acoustic cues in the speech signal to abstract linguistic representations. Learning leads to a lasting benefit to the listener by improving speech comprehension. The change can occur as a response to a specific feature (such as a talker- or accent idiosyncrasy) or to a global degradation of the signal (such as in synthesized or compressed speech). In perceptual learning, a top-down process is involved in causing the change, whereas purely bottom-up, signal-driven phenomena are considered to be adaptation
Lexically-guided perceptual learning in speech processing
During listening to spoken language, the perceptual system needs to adapt frequently to changes in talkers, and thus to considerable interindividual variability in the articulation of a given speech sound. This thesis investigated a learning process which allows listeners to use stored lexical representations to modify the interpretation of a speech sound when a talker's articulation of that sound is consistently unclear or ambiguous. The questions that were addressed in this research concerned the robustness of such perceptual learning, a potential role for sleep, and whether learning is specific to the speech of one talker or, alternatively, generalises to other talkers. A further study aimed to identify the underlying functional neuroanatomy by using magnetic resonance imaging methods. The picture that emerged for lexically-guided perceptual learning is that learning occurs very rapidly, is highly specific, and remains remarkably robust both over time and under exposure to speech from other talkers
Interferometric science results on young stellar objects
Long-baseline interferometry at infrared wavelengths allows the innermost
regions around young stars to be observed. These observations directly probe
the location of the dust and gas in the disks. The characteristic sizes of
these regions found are larger than previously thought. These results have
motivated in part a new class of models of the inner disk structure, but the
precise understanding of the origin of these low visibilities is still in
debate. Mid-infrared observations probe disk emission over a larger range of
scales revealing mineralogy gradients in the disk. Recent spectrally resolved
observations allow the dust and gas to be studied separately showing that the
Brackett gamma emission can find its origin either in a wind or in a
magnetosphere and that there is probably no correlation between the location of
the Brackett gamma emission and accretion. In a certain number of cases, the
very high spatial resolution reveals very close companions and can determine
their masses. Overall, these results provide essential information on the
structure and the physical properties of close regions surrounding young stars
especially where planet formation is suspected to occur.Comment: 18 pages, 6 figures, invited lecture at the VLTI school on
"Astrometry and Imaging with the Very Large Telescope Interferometer", 2-13
June 2008, Keszthely, Hungary. v2: typos corrected; v3: reference adde
Perceptual learning in speech: Stability over time (L)
Contains fulltext :
128203.pdf (publisher's version ) (Open Access)Perceptual representations of phonemes are flexible and adapt rapidly to accommodate idiosyncratic articulation in the speech of a particular talker. This letter addresses whether such adjustments remain stable over time and under exposure to other talkers. During exposure to a story, listeners learned to interpret an ambiguous sound as [f] or [s]. Perceptual adjustments measured after 12 h were as robust as those measured immediately after learning. Equivalent effects were found when listeners heard speech from other talkers in the 12 h interval, and when they had the opportunity to consolidate learning during sleep
Giant capacitance of a plane capacitor with a two-dimensional electron gas in a magnetic field
If a clean two-dimensional electron gas (2DEG) with small concentration
comprises one (or both) electrodes of a plane capacitor, the resulting
capacitance can be larger than the "geometric capacitance" determined
by the physical separation between electrodes. A recent paper [1] argued
that when the effective Bohr radius of the 2DEG satisfies , one
can achieve at low concentration . Here we show that even
for devices with , including graphene, for which is effectively
infinite, one also arrives at at low electron concentration if there
is a strong perpendicular magnetic field.Comment: 6 pages, 5 figures; updated discussion about bilayer systems; added
discussion of fractional quantum Hall state
A little more conversation, a little less action: Candidate roles for motor cortex in speech perception
The motor theory of speech perception assumes that activation of the motor system is essential in the perception of speech. However, deficits in speech perception and comprehension do not arise from damage that is restricted to the motor cortex, few functional imaging studies reveal activity in motor cortex during speech perception, and the motor cortex is strongly activated by many different sound categories. Here, we evaluate alternative roles for the motor cortex in spoken communication and suggest a specific role in sensorimotor processing in conversation. We argue that motor-cortex activation it is essential in joint speech, particularly for the timing of turn-taking
When brain regions talk to each other during speech processing, what are they talking about? Commentary on Gow and Olson (2015).
This commentary on Gow and Olson [2015. Sentential influences on acoustic-phonetic processing: A Granger causality analysis of multimodal imaging data. Language, Cognition and Neuroscience. Advance online publication. doi:10.1080/23273798.2015.1029498] questions in three ways their conclusion that speech perception is based on interactive processing. First, it is not clear that the data presented by Gow and Olson reflect normal speech recognition. Second, Gow and Olson's conclusion depends on still-debated assumptions about the functions performed by specific brain regions. Third, the results are compatible with feedforward models of speech perception and appear inconsistent with models in which there are online interactions about phonological content. We suggest that progress in the neuroscience of speech perception requires the generation of testable hypotheses about the function(s) performed by inter-regional connection
Water for utilities: climate change impacts on water quality and water availability for utilities in Europe
This report provides an assessment of the consequences of changing water availability for production of drinking water, the manufacturing industry and power production in Europe, due to climate change and socio-economic developments. The report is based up on projections of demographic and socio-economic trends and climate change impacts, according to the SRES A2 and B1 scenarioâs also used by IPC
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