Jerker Rönnberg

The Ease of Language Understanding (ELU) model: theoretical, empirical, and clinical advances

Working memory is important for online language processing during conversation. We use it to maintain relevant information, to inhibit or ignore irrelevant information, and to attend to conversation selectively. Working memory helps us to keep track of and actively participate in conversation, including taking turns and following the gist. This paper examines the Ease of Language Understanding model (i.e., the ELU model, Rönnberg, 2003; Rönnberg et al., 2008) in light of new behavioral and neural findings concerning the role of working memory capacity (WMC) in uni-modal and bimodal language processing. The new ELU model is a meaning prediction system that depends on phonological and semantic interactions in rapid implicit and slower explicit processing mechanisms that both depend on WMC albeit in different ways. It is based on findings that address the relationship between WMC and (a) early attention processes in listening to speech, (b) signal processing in hearing aids and its effects on short-term memory, (c) inhibition of speech maskers and its effect on episodic long-term memory, (d) the effects of hearing impairment on episodic and semantic long-term memory, and finally, (e) listening effort. New predictions and clinical implications are outlined. Comparisons with other WMC and speech perception models are made.

Cognition counts: a working memory system for ease of language understanding (ELU).

A general working memory system for ease of language understanding (ELU, Rönnberg, ) is presented. The purpose of the system is to describe and predict the dynamic interplay between explicit and implicit cognitive functions, especially in conditions of poorly perceived or poorly specified linguistic signals. In relation to speech understanding, the system based on (1) the quality and precision of phonological representations in long-term memory, (2) phonologically mediated lexical access speed, and (3) explicit, storage, and processing resources. If there is a mismatch between phonological information extracted from the speech signal and the phonological information represented in long-term memory, the system is assumed to produce a mismatch signal that invokes explicit processing resources. In the present paper, we focus on four aspects of the model which have led to the current, updated version: the language generality assumption; the mismatch assumption; chronological age; and the episodic buffer function of rapid, automatic multimodal binding of phonology (RAMBPHO). We evaluate the language generality assumption in relation to sign language and speech, and the mismatch assumption in relation to signal processing in hearing aids. Further, we discuss the effects of chronological age and the implications of RAMBPHO.

Cognition in the hearing impaired and deaf as a bridge between signal and dialogue: a framework and a model

This paper focuses on the role of cognition in visual language processing in the deaf and hard of hearing. Although there are modality-specific cognitive findings in the literature on comparisons across speech communication modes and language (sign and speech), there is an impressive bulk of evidence that supports the notion of general modality-free cognitive functions in speech and sign processing, A working-memory framework is proposed for the cognitive involvement in language understanding (sign and speech). On the basis of multiple sources of behavioural and neuro-science data, four important parameters for language understanding are described in some detail: quality and precision of phonology, long-term memory access speed, degree of explicit processing, and general processing and storage capacity. Their interaction forms an important parameter space, and general predictions and applications can be derived for both spoken and signed language conditions. The model is mathematically formulated at a general level, hypothetical ease-of-language-understanding (ELU) functions are presented, and similarities and differences from current working-memory and speech perception formulations are pointed out.

Cognition and hearing aids

The perceptual information transmitted from a damaged cochlea to the brain is more poorly specified than information from an intact cochlea and requires more processing in working memory before language content can be decoded. In addition to making sounds audible, current hearing aids include several technologies that are intended to facilitate language understanding for persons with hearing impairment in challenging listening situations. These include directional microphones, noise reduction, and fast-acting amplitude compression systems. However, the processed signal itself may challenge listening to the extent that with specific types of technology, and in certain listening situations, individual differences in cognitive processing resources may determine listening success. Here, current and developing digital hearing aid signal processing schemes are reviewed in the light of individual working memory (WM) differences. It is argued that signal processing designed to improve speech understanding may have both positive and negative consequences, and that these may depend on individual WM capacity.

Computerized training of working memory in a group of patients suffering from acquired brain injury

Objective: Study short- and long-term transfer effects of a computerized working memory (WM) training programme for patients suffering from working memory deficits after acquired brain injury. Research design: A controlled experimental study with a cross-over design. Methods: A consecutive sample of 21 subjects. Mean age 43.2 years, time since injury/illness onset 37 months (median). The subjects were randomly selected into two groups where one group served as controls. All subjects trained daily for 5 weeks in a computer WM task program. They were followed-up at 4 and 20 weeks after the training. Results: A significant improvement in the trained WM tasks, significant improvements in neuropsychological WM-test results at 4 and 20 weeks after training compared to baseline. Improvement in the subjects’ rated occupational performance and satisfaction with performance in pre-defined occupational problems. Rated quality-of-life did not change. However, rated overall health increased 20 weeks after training. Conclusions: Structured and intense computerized WM training improves subjects’ cognitive functioning as measured by neuropsychological WM-demanding tests, rated occupational performance, satisfaction with performance and rated overall health. The training probably has an impact on the rehabilitation outcome, returning to work, as well as on daily activities for individuals with verified WM impairments.

When cognition kicks in: Working memory and speech understanding in noise

Perceptual load and cognitive load can be separately manipulated and dissociated in their effects on speech understanding in noise. The Ease of Language Understanding model assumes a theoretical position where perceptual task characteristics interact with the individuals implicit capacities to extract the phonological elements of speech. Phonological precision and speed of lexical access are important determinants for listening in adverse conditions. If there are mismatches between the phonological elements perceived and phonological representations in long-term memory, explicit working memory (WM)-related capacities will be continually invoked to reconstruct and infer the contents of the ongoing discourse. Whether this induces a high cognitive load or not will in turn depend on the individuals storage and processing capacities in WM. Data suggest that modulated noise maskers may serve as triggers for speech maskers and therefore induce a WM, explicit mode of processing. Individuals with high WM capacity benefit more than low WM-capacity individuals from fast amplitude compression at low or negative input speech-to-noise ratios. The general conclusion is that there is an overarching interaction between the focal purpose of processing in the primary listening task and the extent to which a secondary, distracting task taps into these processes.

Neuropsychological aspects of driving after a stroke : in the simulator and on the road

Thirty patients with stroke and 30 matched controls participated in the study (mean age 68 years, mean interval since stroke onset 8.6 months). The patients performed significantly worse on cogniti ...

Effects of noise and working memory capacity on memory processing of speech for hearing-aid users.

Abstract Objectives: It has been shown that noise reduction algorithms can reduce the negative effects of noise on memory processing in persons with normal hearing. The objective of the present study was to investigate whether a similar effect can be obtained for persons with hearing impairment and whether such an effect is dependent on individual differences in working memory capacity. Design: A sentence-final word identification and recall (SWIR) test was conducted in two noise backgrounds with and without noise reduction as well as in quiet. Working memory capacity was measured using a reading span (RS) test. Study sample: Twenty-six experienced hearing-aid users with moderate to moderately severe sensorineural hearing loss. Results: Noise impaired recall performance. Competing speech disrupted memory performance more than speech-shaped noise. For late list items the disruptive effect of the competing speech background was virtually cancelled out by noise reduction for persons with high working memory capacity. Conclusions: Noise reduction can reduce the adverse effect of noise on memory for speech for persons with good working memory capacity. We argue that the mechanism behind this is faster word identification that enhances encoding into working memory.

Collaboration and Memory: Effects of Dyadic Retrieval on Different Memory Tasks

Collaborative retrieval was investigated in two experiments. The experiments were explicitly designed to investigate how different types of memory tasks were affected by two individuals working together compared to individuals working on their own. A nominal group score was treated as the predicted potential a dyad could attain. In Experiment 1, semantic and episodic retrieval were employed. The episodic task was to encode and retrieve a story and the semantic task was to answer, without any encoding, 20 questions from the same history domain as the episodic task. In Experiment 2, explicit recognition and implicit retrieval of dot patterns were employed. The explicit recognition task was forced-choice, and in the implicit task, subjects were instructed to complete a pattern they saw from an incomplete pattern. The results suggest that: (1) dyads suffer from collaboration relative to the predicted potential, (2) the reduction of productivity for dyads was limited to explicit and episodic memory tasks, and (3) friends as opposed to non-friends reduced the negative effect of collaboration. The results replicate and extend the results from a previous study.

Working Memory Capacity May Influence Perceived Effort during Aided Speech Recognition in Noise

BACKGROUND Recently there has been interest in using subjective ratings as a measure of perceived effort during speech recognition in noise. Perceived effort may be an indicator of cognitive load. Thus, subjective effort ratings during speech recognition in noise may covary both with signal-to-noise ratio (SNR) and individual cognitive capacity. PURPOSE The present study investigated the relation between subjective ratings of the effort involved in listening to speech in noise, speech recognition performance, and individual working memory (WM) capacity in hearing impaired hearing aid users. RESEARCH DESIGN In two experiments, participants with hearing loss rated perceived effort during aided speech perception in noise. Noise type and SNR were manipulated in both experiments, and in the second experiment hearing aid compression release settings were also manipulated. Speech recognition performance was measured along with WM capacity. STUDY SAMPLE There were 46 participants in all with bilateral mild to moderate sloping hearing loss. In Experiment 1 there were 16 native Danish speakers (eight women and eight men) with a mean age of 63.5 yr (SD = 12.1) and average pure tone (PT) threshold of 47. 6 dB (SD = 9.8). In Experiment 2 there were 30 native Swedish speakers (19 women and 11 men) with a mean age of 70 yr (SD = 7.8) and average PT threshold of 45.8 dB (SD = 6.6). DATA COLLECTION AND ANALYSIS A visual analog scale (VAS) was used for effort rating in both experiments. In Experiment 1, effort was rated at individually adapted SNRs while in Experiment 2 it was rated at fixed SNRs. Speech recognition in noise performance was measured using adaptive procedures in both experiments with Dantale II sentences in Experiment 1 and Hagerman sentences in Experiment 2. WM capacity was measured using a letter-monitoring task in Experiment 1 and the reading span task in Experiment 2. RESULTS In both experiments, there was a strong and significant relation between rated effort and SNR that was independent of individual WM capacity, whereas the relation between rated effort and noise type seemed to be influenced by individual WM capacity. Experiment 2 showed that hearing aid compression setting influenced rated effort. CONCLUSIONS Subjective ratings of the effort involved in speech recognition in noise reflect SNRs, and individual cognitive capacity seems to influence relative rating of noise type.