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Ferguson M.A.,National Health Research Institute | Henshaw H.,National Health Research Institute | Clark D.P.A.,National Health Research Institute | Moore D.R.,National Health Research Institute | Moore D.R.,Medical Research Council Institute of Hearing Research
Ear and Hearing | Year: 2014

OBJECTIVES: The aims of this study were to (i) evaluate the efficacy of phoneme discrimination training for hearing and cognitive abilities of adults aged 50 to 74 years with mild sensorineural hearing loss who were not users of hearing aids, and to (ii) determine participant compliance with a self-administered, computer-delivered, home- and game-based auditory training program. DESIGN: This study was a randomized controlled trial with repeated measures and crossover design. Participants were trained and tested over an 8- to 12-week period. One group (Immediate Training) trained during weeks 1 and 4. A second waitlist group (Delayed Training) did no training during weeks 1 and 4, but then trained during weeks 5 and 8. On-task (phoneme discrimination) and transferable outcome measures (speech perception, cognition, self-report of hearing disability) for both groups were obtained during weeks 0, 4, and 8, and for the Delayed Training group only at week 12. RESULTS: Robust phoneme discrimination learning was found for both groups, with the largest improvements in threshold shown for those with the poorest initial thresholds. Between weeks 1 and 4, the Immediate Training group showed moderate, significant improvements on self-report of hearing disability, divided attention, and working memory, specifically for conditions or situations that were more complex and therefore more challenging. Training did not result in consistent improvements in speech perception in noise. There was no evidence of any test-retest effects between weeks 1 and 4 for the Delayed Training group. Retention of benefit at 4 weeks post-training was shown for phoneme discrimination, divided attention, working memory, and self-report of hearing disability. Improved divided attention and reduced self-reported hearing difficulties were highly correlated. CONCLUSIONS: It was observed that phoneme discrimination training benefits some but not all people with mild hearing loss. Evidence presented here, together with that of other studies that used different training stimuli, suggests that auditory training may facilitate cognitive skills that index executive function and the self-perception of hearing difficulty in challenging situations. The development of cognitive skills may be more important than the development of sensory skills for improving communication and speech perception in everyday life. However, improvements were modest. Outcome measures need to be appropriately challenging to be sensitive to the effects of the relatively small amount of training performed. Copyright © 2014 by Lippincott Williams & Wilkins.

Barrett D.J.K.,University of Leicester | Zobay O.,Medical Research Council Institute of Hearing Research
PLoS ONE | Year: 2014

Simultaneous search for two targets has been shown to be slower and less accurate than independent searches for the same two targets. Recent research suggests this 'dual-target cost' may be attributable to a limit in the number of targettemplates than can guide search at any one time. The current study investigated this possibility by comparing behavioural responses during single- and dual-target searches for targets defined by their orientation. The results revealed an increase in reaction times for dual- compared to single-target searches that was largely independent of the number of items in the display. Response accuracy also decreased on dual- compared to single-target searches: dual-target accuracy was higher than predicted by a model restricting search guidance to a single target-template and lower than predicted by a model simulating two independent single-target searches. These results are consistent with a parallel model of dual-target search in which attentional control is exerted by more than one target-template at a time. The requirement to maintain two targettemplates simultaneously, however, appears to impose a reduction in the specificity of the memory representation that guides search for each target. © 2014 Barrett, Zobay.

Amitay S.,Medical Research Council Institute of Hearing Research | Guiraud J.,Medical Research Council Institute of Hearing Research | Guiraud J.,Royal Holloway, University of London | Sohoglu E.,Medical Research Council Institute of Hearing Research | And 7 more authors.
PLoS ONE | Year: 2013

Perceptual decision making is prone to errors, especially near threshold. Physiological, behavioural and modeling studies suggest this is due to the intrinsic or 'internal' noise in neural systems, which derives from a mixture of bottom-up and top-down sources. We show here that internal noise can form the basis of perceptual decision making when the external signal lacks the required information for the decision. We recorded electroencephalographic (EEG) activity in listeners attempting to discriminate between identical tones. Since the acoustic signal was constant, bottom-up and top-down influences were under experimental control. We found that early cortical responses to the identical stimuli varied in global field power and topography according to the perceptual decision made, and activity preceding stimulus presentation could predict both later activity and behavioural decision. Our results suggest that activity variations induced by internal noise of both sensory and cognitive origin are sufficient to drive discrimination judgments. © 2013 Amitay et al.

Molloy K.,Medical Research Council Institute of Hearing Research | Moore D.R.,Medical Research Council Institute of Hearing Research | Sohoglu E.,Medical Research Council Institute of Hearing Research | Sohoglu E.,Medical Research Council Cognition and Brain science Unit | Amitay S.,Medical Research Council Institute of Hearing Research
PLoS ONE | Year: 2012

Background: The time course and outcome of perceptual learning can be affected by the length and distribution of practice, but the training regimen parameters that govern these effects have received little systematic study in the auditory domain. We asked whether there was a minimum requirement on the number of trials within a training session for learning to occur, whether there was a maximum limit beyond which additional trials became ineffective, and whether multiple training sessions provided benefit over a single session. Methodology/Principal Findings: We investigated the efficacy of different regimens that varied in the distribution of practice across training sessions and in the overall amount of practice received on a frequency discrimination task. While learning was relatively robust to variations in regimen, the group with the shortest training sessions (~8 min) had significantly faster learning in early stages of training than groups with longer sessions. In later stages, the group with the longest training sessions (>1 hr) showed slower learning than the other groups, suggesting overtraining. Between-session improvements were inversely correlated with performance; they were largest at the start of training and reduced as training progressed. In a second experiment we found no additional longer-term improvement in performance, retention, or transfer of learning for a group that trained over 4 sessions (~4 hr in total) relative to a group that trained for a single session (~1 hr). However, the mechanisms of learning differed; the single-session group continued to improve in the days following cessation of training, whereas the multi-session group showed no further improvement once training had ceased. Conclusions/Significance: Shorter training sessions were advantageous because they allowed for more latent, between-session and post-training learning to emerge. These findings suggest that efficient regimens should use short training sessions, and optimized spacing between sessions. © 2012 Molloy et al.

Maidment D.W.,Medical Research Council Institute of Hearing Research | Kang H.,Medical Research Council Institute of Hearing Research | Kang H.,Ecole Normale Superieure de Paris | Gill E.C.,Medical Research Council Institute of Hearing Research | Amitay S.,Medical Research Council Institute of Hearing Research
PLoS ONE | Year: 2015

Learning is considered to consist of two distinct phases-acquisition and consolidation. Acquisition can be disrupted when short periods of training on more than one task are interleaved, whereas consolidation can be disrupted when a second task is trained after the first has been initiated. Here we investigated the conditions governing the disruption to acquisition and consolidation during mixed-training regimens in which primary and secondary amplitude modulation tasks were either interleaved or presented consecutively. The secondary task differed from the primary task in either task-irrelevant (carrier frequency) or task-relevant (modulation rate) stimulus features while requiring the same perceptual judgment (amplitude modulation depth discrimination), or shared both irrelevant and relevant features but required a different judgment (amplitude modulation rate discrimination). Based on previous literature we predicted that acquisition would be disrupted by varying the task-relevant stimulus feature during training (stimulus interference), and that consolidation would be disrupted by varying the perceptual judgment required (task interference). We found that varying the task-relevant or -irrelevant stimulus features failed to disrupt acquisition but did disrupt consolidation, whereas mixing two tasks requiring a different perceptual judgment but sharing the same stimulus features disrupted both acquisition and consolidation. Thus, a distinction between acquisition and consolidation phases of perceptual learning cannot simply be attributed to (task-relevant) stimulus versus task interference. We propose instead that disruption occurs during acquisition when mixing two tasks requiring a perceptual judgment based on different cues, whereas consolidation is always disrupted regardless of whether different stimulus features or tasks are mixed. The current study not only provides a novel insight into the underlying mechanisms of perceptual learning, but also has practical implications for the optimal design and delivery of training programs that aim to remediate perceptual difficulties. © 2015 Maidment et al.

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