73 research outputs found
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Reduced benefit from regularities in language among Dyslexics
No full textThe ”Anchoring Deficit” hypothesis (Ahissar et al., Nat Neurosci. 2006) proposed that Dyslexics have a difficultyin automatic extraction of simple stimulus regularities in sound sequences. JaffeDax et al. (J Neurosci. 2015) modelled thesedifficulties as yielding noisy priors.The current study was aimed to assess the impact of long-term regularities in language, which listeners had life long experi-ence with. Our assumption was that this familiarity would enhance Controls’ performance more than Dyslexics’ due to a noisierprior formation among Dyslexics. This question was addressed in a series of experiments - in each there was one condition forwhich information accumulated over the life span could be utilized.In all three experiments Dyslexics did not benefit as much as Controls from the long term statistics associated with the input.These results suggest that Dyslexics could not compensate for the deficit despite multiple exposures to lingual input with thesame statistics
Parameter Estimation of Linear Sensorimotor Synchronization Models: Phase Correction, Period Correction, and Ensemble Synchronization
No full text<p>Linear models have been used in several contexts to study the mechanisms that underpin sensorimotor synchronization. Given that their parameters are often linked to psychological processes such as phase correction and period correction, the fit of the parameters to experimental data is an important practical question. We present a unified method for parameter estimation of linear sensorimotor synchronization models that extends available techniques and enhances their usability. This method enables reliable and efficient analysis of experimental data for single subject and multi-person synchronization. In a previous paper (Jacoby et al., 2015), we showed how to significantly reduce the estimation error and eliminate the bias of parameter estimation methods by adding a simple and empirically justified constraint on the parameter space. By applying this constraint in conjunction with the tools of matrix algebra, we here develop a novel method for estimating the parameters of most linear models described in the literature. Through extensive simulations, we demonstrate that our method reliably and efficiently recovers the parameters of two influential linear models: Vorberg and Wing (1996), and Schulze et al. (2005), together with their multi-person generalization to ensemble synchronization. We discuss how our method can be applied to include the study of individual differences in sensorimotor synchronization ability, for example, in clinical populations and ensemble musicians.</p>
<p><strong>Implementation of the bGLS Method</strong><br>For more information see in <em>Timing & Time Perception</em>, Special issue on Rhythm Production and Perception (RPPW):<br>Jacoby, N., Tishby, N., Repp, B. H., Ahissar, M., & Keller, P. E. (2015). Parameter estimation of linear<br>sensorimotor synchronization models: Phase correction, period correction and ensemble synchronization. <em>Timing Time Percept.</em>, 3, 52-87.<br>and<br>Jacoby, N., Keller, P. E., Repp, B. H., Ahissar, M., & Tishby, N. (2015). Lower bound on the accuracy<br>of parameter estimation methods for linear sensorimotor synchronization models. <em>Timing Time</em><br><em>Percept.</em>, 3, 32-51.</p>
<p><br>[email protected]<br>Please cite this paper if you are using this package:<br>Nori Jacoby, Naftali Tishby, Bruno H. Repp, Merav Ahissar and Peter E. Keller (2015)</p>
<p><br>IMPORTANT: This code is currently (12/14) in beta.<br>Critical updates will be forthcoming.</p>
<p><br>ALL CODE BY: Nori Jacoby ([email protected])</p>
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Widespread shorter cortical adaptation in dyslexia
No full textAbstractStudies of dyslexics’ performance on perceptual tasks suggest that their implicit inference of sound statistics is impaired. In a previous paper (Jaffe-Dax, Frenkel, & Ahissar, 2017), using 2-tone frequency discrimination, we found that the effect of previous trial frequencies on dyslexics’ judgments decayed faster than the effect on controls’ judgments, and that the adaptation of their ERP responses to tones recovered faster. Here, we show the cortical distribution of this abnormal dynamics of adaptation using fast acquisition fMRI. We find that dyslexics’ faster decay of adaptation is widespread, though the most significant effects are found in the left superior temporal lobe, including the auditory cortex. This broad distribution suggests that dyslexics’ faster decay of implicit memory is a general characteristic of their cortical dynamics, which also encompasses the sensory cortices.</jats:p
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Practicing an auditory working memory task recruits lower-level auditory areas ina task-specific manner
No full textWe studied the impact of the trained auditory task on the pattern of behavioural improvement, and its relation tothe underlying neural mechanisms. Specifically, we asked whether training with tone retention and manipulation (workingmemory, WM) transferred to pitch discrimination and vice versa, and whether training modified the brain areas that underlietask performance. Training substantially improved performance, but did not transfer across tasks, even when using the samestimuli. Pre and post training fMRI scans revealed that WM training enhanced activity in bilateral auditory cortices, butnot in frontal areas that are initially associated with higher cognitive functions. These results suggest that training-inducedimprovement is associated with back-tracking along the reverse hierarchy in a task specific manner, as predicted by the ReverseHierarchy Theory of perceptual learning (Ahissar & Hochstein, 2004). Thus, low-level areas are recruited, but there is nogeneral upgrade in WM or in auditory skills
Reduced Benefit from Long-term Item Frequency Contributes to Short-term Memory Deficits in Dyslexia
No full textDyslexia, a specific difficulty in acquiring proficient reading, is also characterized by reduced short-term memory (STM) capacity, which is often attributed to poor phonological memory. However, while it is well established that performance in STM tasks is greatly influenced by the frequency of the comprising items, the effect of item frequency in a span task on the performance of Individuals with Developmental Dyslexia (IDDs) has not been tested until recently. Kimel and colleagues (Kimel et al. 2020; Kimel, Lieder, and Ahissar 2022) asked this question using syllables with high vs. low frequency, and found that the benefit of syllable frequency to STM is reduced among IDDs. We now test the effect of item frequency on the performance in a standard, widely used, STM assessment - the Digit Span subtest from the Wechsler Adult Intelligence Scale. The task was conducted twice: in native language and in second language. As the exposure to native language is greater than to second language, we predicted that IDDs’ performance in the task administered in native language will reveal a larger group difference as compared to second language, due to IDDs’ reduced benefit of item frequency. The prediction was confirmed, in line with the hypothesis that reduced STM in dyslexia to a large extent reflects reduced benefits from long-term item frequency and not a reduced STM per-se
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What Do We Learn from Dyslexia and Second Language Learners on theDifference Between Long-term Frequency and Short-term Sequence RepetitionEffects?
No full textDyslexia is a common learning disability, but its core deficit is still under debate. The anchoring deficit hypothesissuggests that dyslexics’ benefit from experimental stimuli statistics is impaired (e.g. Ahissar, 2007). In this study we askedwhether dyslexia is also associated with reduced sensitivity to long-term statistics. Spans for lists of syllables were measured,and indeed, dyslexics benefited less than controls from syllabic frequency. However, dyslexics’ benefit from sequence repetitionwas similar to controls’. In order to dissociate the impact of item familiarity from exposure unrelated factors, native Englishspeakers performed the experiment. They were expected to benefit from repetition, but not from syllabic frequency (in Hebrew).Indeed, that was the case. These data suggest that benefits from long-term distributional statistics are impaired in dyslexia,whereas on-line benefits from sequence repetition are adequate. Moreover, our results suggest different underlying mechanismsfor long-term distribution learning and short-term sequence learning
Learning Pop-out Detection: Specificities to Stimulus Characteristics
No full textAbstractTraining induces dramatic improvement in the performance of pop-out detection. In this study, we examined the specificities of this improvement to stimulus characteristics. We found that learning is specific within basic visual dimensions: orientation, size and position. Accordingly, following training with one set of orientations, rotating target and distractors by 30 deg or more substantially hampers performance. Furthermore, rotation of either target or distractors alone greatly increases threshold. Learning is not transferred to reduced-size stimuli. Position specificity near fixation may be finer than 0.7 deg. On the other hand, learning transfers to the untrained eye, to expanded images, to mirror image transformations and to homologous positions across the midline (near fixation). Thus, learning must occur at a processing level which is early enough to maintain fine separability along basic stimulus dimensions, yet sufficiently high to manifest the described generalizations. We suggest that the site of early perceptual learning is one of the cortical areas which receive input from primary visual cortex, V1, and where top-down attentional control is present. Copyright © 1996 Elsevier Science Ltd
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