The relation between working memory capacity and auditory lateralization in children with auditory processing disorders

Numerous studies reported a strong link between working memory capacity (WMC) andfluid intelligence (Gf), although views differ in respect tohow close these two constructs are related to each other. In the present study,we used a WMC task with five levels of task demands to assess the relationshipbetween WMC and Gf by means of a new methodological approachreferred to as fixed-links modeling. Fixed-links models belong to the family ofconfirmatory factor analysis (CFA) and are of particular interest forexperimental, repeated-measures designs. With this technique, processessystematically varying across task conditions can be disentangled from processesunaffected by the experimental manipulation. Proceeding from the assumption thatexperimental manipulation in a WMC task leads to increasing demands on WMC, theprocesses systematically varying across task conditions can be assumed to beWMC-specific. Processes not varying across task conditions, on the other hand,are probably independent of WMC. Fixed-links models allow for representing thesetwo kinds of processes by two independent latent variables. In contrast totraditional CFA where a common latent variable is derived from the differenttask conditions, fixed-links models facilitate a more precise or purifiedrepresentation of the WMC-related processes of interest. By using fixed-linksmodeling to analyze data of 200 participants, we identified a non-experimentallatent variable, representing processes that remained constant irrespective ofthe WMC task conditions, and an experimental latent variable which reflectedprocesses that varied as a function of experimental manipulation. This lattervariable represents the increasing demands on WMC and, hence, was considered apurified measure of WMC controlled for the constant processes. Fixed-linksmodeling showed that both the purified measure of WMC (β = .48) as well as theconstant processes involved in the task (β = .45) were related toGf. Taken together, these two latent variables explainedthe same portion of variance of Gf as a single latent variableobtained by traditional CFA (β = .65) indicating that traditional CFA causes anoverestimation of the effective relationship between WMC andGf. Thus, fixed-links modeling provides a feasible method for amore valid investigation of the functional relationship between specificconstructs.

Is the n-back task a measure of unstructured working memory capacity? Towards understanding its connection to other working memory tasks

It is well established that measures of reasoning ability and of working memory capacity (WMC) correlate positively. However, the question of what explains this relationship remains open. The purpose of this study was to investigate the capacity hypothesis, which ascribes causality to WMC. This hypothesis holds that people high in WMC are more successful in capacity-demanding cognitive tasks than people lower in WMC because they can temporarily maintain more information in the form of sub-goals, hypotheses, and partial solutions. Accordingly, this hypothesis predicts that the correlation between WMC and reasoning performance should increase as the capacity demands of the reasoning items increase. We tested this prediction using items from Raven's Progressive Matrices and two measures of WMC, complex span and the k estimate from the Visual Arrays task. Neither WMC measure showed the effect predicted by the capacity hypothesis. Furthermore, the results cannot be attributed to restriction of range in performance on the individual reasoning items. This finding adds to existing evidence calling into question the capacity hypothesis, and, more generally, the view that WMC has a causal influence on fluid intelligence.

The purposes of the study were to investigate (a) the task-specific differences in short-term memory (STM) and working memory capacity (WMC) in individuals with mild cognitive impairment (MCI) and normal elderly adults (NEAs), (b) the Stroop interference and facilitation effects, and (c) the relationship of STM and WMC to the Stroop effects. Thirty-two individuals participated in the study (n = 16 for each group). WMC demands were increased using a computerized Stroop-like token task to add more linguistic units. Six STM and WMC measures were administered overall. Digit-related tasks and an alphabet span task sensitively differentiated individuals with MCI from the NEA group. The group with MCI exhibited greater Stroop interference effects than the NEA group, but the 2 groups did not exhibit different Stroop facilitation effects. WMC significantly predicted performance on the response time analyses but not on the error rate analyses. Task-specific differences emerged in the group with MCI, and a reduced WMC accounts for the impaired inhibitory and goal maintenance processes. It is critical that WMC demands be systematically manipulated to tax individuals' WMC in a way that can clearly demonstrate their deficits, especially in individuals who are at risk for clinically demented states.

Intelligence is one of the most studied constructs in psychological research and fascinates scientists and the general public alike. Accordingly, researchers have spent decades trying to identify the processes underlying individual differences in intelligence, eventually proposing two widely accepted candidates: the information processing speed (IPS; also referred to as mental speed) and the working memory capacity (WMC). Research consistently shows that higher intelligence is associated with greater speed of information processing on the one hand, and higher WMC on the other. While this nomological network is well established, recent findings on the measurement of WMC and IPS suggest that further research could refine our understanding of this relationship. Thus, the central aim of this dissertation is to gain insights into the processes underlying individual differences in intelligence by integrating recent findings from different streams of cognitive psychology, neuroscience, and intelligence research. I propose that, in order to gain new insights, we must first improve our understanding of the measures used, in particular WMC and IPS, and secondly examine the boundary conditions under which the respective correlations occur. In line with this agenda, three central research approaches are outlined as part of this dissertation: 1) First, to enhance our understanding of the processes involved in WM, I examined the neurophysiological representation of WM tasks commonly used to measure WMC. 2) Second, to improve the measurement of IPS, I investigated the conditions under which researchers may obtain reliable and valid neurophysiological indicators of IPS. 3) Third, I tested the boundary conditions of the relationship between IPS, WMC, and intelligence. Together, this dissertation provides guidance for intelligence research and allows conclusions to be drawn about the nature of the mechanisms underlying intelligence. In particular, the findings suggest that a) general short-term maintenance may account for the relationship between WMC and intelligence, b) analytical decisions affect the validity and reliability of neurocognitive IPS measurements, supporting the use of latent modeling, and c) the speed of decision-related processes is most likely the driver of the relationship between IPS and intelligence.

There is a history of debate and controversy about the assessment and intervention of children diagnosed with auditory processing disorder (APD). Professionals in communication sciences and disorders view APD from different perspectives. Speech-language pathologists (SLPs) tend to view APD from the language and literacy perspective, or a top-down model, whereas audiologists tend to view APD from an auditory perception perspective, or a bottom-up model. Professionals who assess and treat children with APD need to bridge the gap and merge their different perspectives to plan effective intervention for children with APD. A panel of audiologists who demonstrated expertise in the area of Central Auditory Processing Disorders (CAPDs) developed The American Speech-Language-Hearing Association's (ASHA's) technical report on APDs (ASHA, 2005). This report was approved by ASHA's Executive board in 2005. In this report, central auditory processing refers to the efficiency and effectiveness by which the central nervous system uses auditory information. Central auditory processing includes the auditory mechanisms underlying the skills of sound localization and lateralization; auditory discrimination; auditory pattern recognition; temporal aspects of audition, including temporal integration, temporal discrimination, temporal ordering, and temporal masking; auditory performance in competing acoustic signals; and auditory performance with degraded acoustic signals (ASHA, 1996; Bellis, 2003; Chermak & Musiek, 1997; Jerger, 2009). A CAPD is a deficit in processing auditory input that is not due to higher-order language, cognitive, or related factors (Musiek, Bellis, & Chermak, 2005; Musiek & Chermak, 2007). However, children diagnosed with CAPD may experience difficulties in academic learning, speech, language, social skills, and literacy (e.g., encoding, decoding, reading comprehension, reading fluency, and written language).

Introduction: Working memory is assumed to play a major part in hearing and communication in everyday listening situations. Our working memory stores information, but in suboptimal listening conditions, interfering stimuli can lead to information only being partially stored, or even missed. Research suggests that a high working memory capacity (WMC) might not just be a result of a large store, but in addition good inhibitory control can facilitate working memory, and therefore aid in situations where focus on a target stimulus while ignoring distractors is needed.Objective: The aim of the present study was to investigate how individual WMC, cognitive inhibition, and lexical decision relate to listening to speech under adverse conditions in two separate groups: 46 young normally hearing (NH) and 40 elderly hearing-impaired (HI) individuals.Results: It showed that lexical access was of little importance for young NH individuals in a speech-in-noise test, but that high lexical decision-making was associated with lower signal-to-noise ratios for the elderly HI individuals. The results also showed that WMC was of importance for word recognition in a speech-in-noise test for elderly participants, when the 80% word recognition criterion was targeted, but not for the young NH individuals. Finally, results suggest that cognitive inhibition, as measured with the Hayling task, was important for young NH individuals when listening conditions are suboptimal.Conclusion: In conclusion, hearing loss is a strong contributing factor to declines in the ability to recognize speech in noise, and in order to assess speech-recognition-in-noise performance, individual differences in WMC and cognitive inhibition should be taken into consideration. Future research should include various age groups, with and without hearing loss, as well as measures of WMC, cognitive inhibition, and lexical access when assessing the ability to listen to speech under adverse conditions.

Modulation of auditory temporal processing, speech in noise perception, auditory-verbal memory, and reading efficiency by anodal tDCS in children with dyslexia

Explaining the high working memory capacity of gifted children: Contributions of processing skills and executive control

The theoretical issues surrounding central auditory processing disorders (CAPD) are reviewed here, especially with reference to the central auditory behavioral processes and the auditory test measures as prescribed in the ASHA (1996, American Journal of Audiology, 5(2), 41-54) statement on CAPD. A simplified nomenclature is recommended that directly relates process and test measure to facilitate the diagnostic process in CAPD. This new terminology closely follows the ASHA (1996, American Journal of Audiology, 5(2), 41-54) document, but provides some refinement based on recent research in CAPD. To support this recommendation, a confirmatory factor analysis (CFA) was applied to the findings of Domitz and Schow (2000, American Journal of Audiology), who proposed use of a battery of CAPD tests, the Multiple Auditory Processing Assessment (MAPA) for testing school children. The CFA was found to reinforce the four-factor model, which clearly emerged in the exploratory factor analysis of Domitz and Schow. The model was found to be reasonably consistent even when subtests from the SCAN were included in the analysis. Refinement and revision of ASHA (1996, American Journal of Audiology, 5(2), 41-54) is recommended to facilitate diagnosis, subclassification, and intervention for CAPD.

Purpose Evaluate and compare the performance of cognitive functions between elderly with and without auditory processing disorders. Methods Twenty-eight healthy elderly (14 Control group and 14 Auditory Processing Disorder group - APD group) participated in the study. All elderly were submitted to (central) auditory processing evaluation, P300 event-related potential and brief cognitive battery (BCB). In the comparison between subjects, the Mann-Whitney test was applied and in the intra-subjects comparison, the Wilcoxon signed rank test was used. To verify if there was an association between the performance of the PAC and the cognitive variables, Spearman's correlation was used. Results There were no statistically significant differences between the Control and APD groups for the cognitive abilities assessed by BCB, as well as for the P300 cognitive potential variables. Conclusion Elderly with auditory processing disorders do not seem to show greater cognitive difficulties compared to elderly of the same age group without auditory processing disorders, exception of the clock drawing test, whose task involves multiple cognitive functions, including visuospatial processing, executive function, semantic memory, and planning.

To identify the factors that may underlie the deficits in children with listening difficulties, despite normal pure-tone audiograms. These children may have auditory processing disorder (APD), but there is no universally agreed consensus as to what constitutes APD. The authors therefore refer to these children as children with suspected APD (susAPD) and aim to clarify the role of attention, cognition, memory, sensorimotor processing speed, speech, and nonspeech auditory processing in susAPD. It was expected that a factor analysis would show how nonauditory and supramodal factors relate to auditory behavioral measures in such children with susAPD. This would facilitate greater understanding of the nature of listening difficulties, thus further helping with characterizing APD and designing multimodal test batteries to diagnose APD. Factor analysis of outcomes from 110 children (68 male, 42 female; aged 6 to 11 years) with susAPD on a widely used clinical test battery (SCAN-C) and a research test battery (MRC Institute of Hearing Research Multi-center Auditory Processing "IMAP"), that have age-based normative data. The IMAP included backward masking, simultaneous masking, frequency discrimination, nonverbal intelligence, working memory, reading, alerting attention and motor reaction times to auditory and visual stimuli. SCAN-C included monaural low-redundancy speech (auditory closure and speech in noise) and dichotic listening tests (competing words and competing sentences) that assess divided auditory attention and hence executive attention. Three factors were extracted: "general auditory processing," "working memory and executive attention," and "processing speed and alerting attention." Frequency discrimination, backward masking, simultaneous masking, and monaural low-redundancy speech tests represented the "general auditory processing" factor. Dichotic listening and the IMAP cognitive tests (apart from nonverbal intelligence) were represented in the "working memory and executive attention" factor. Motor response times to cued and noncued auditory and visual stimuli were grouped in the "processing speed and alerting attention" factor. Individuals varied in their outcomes in different tests. Poor performance was noted in different combinations of tests from the three factors. Impairments solely related to the "general auditory processing" factor were not common. The study identifies a general auditory processing factor in addition to two other cognitive factors, "working memory and executive attention" and "processing speed and alerting attention," to underlie the deficits in children with susAPD. Impaired attention, memory, and processing speed are known to be associated with poor literacy and numeracy skills as well as a number of neurodevelopmental disorders. Individuals with impairments in the "general auditory processing" tests along with tests from the other two cognitive factors may explain the co-occurrence of APD and other disorders. The variation in performance by individuals in the different tests noted was probably due to a number of reasons including heterogeneity in susAPD and less-than ideal test-retest reliabilities of the tests used to assess APD. Further research is indicated to explore additional factors, and consensus is needed to improve the reliability of tests or find alternative approaches to diagnose APD, based on the underlying factors.

Purpose No gold standard criteria exist for diagnosing developmental auditory processing disorder (APD). This study aimed to identify APD criteria, which are consistent with that used for comorbidities, and how comorbidities predicted APD. Method A retrospective study of 167 participants (males = 105, females = 62; age: 6-16 years; nonverbal IQ > 80) with suspected APD is presented. Five SCAN-3 tests evaluated auditory processing (AP). Comorbidities included attention-deficit/hyperactivity disorder, language impairment, and impaired manual dexterity, which were identified using percentile ≤ 5 in the Swanson, Nolan and Pelham parental rating scale; Children's Communication Checklist-2; and Movement Assessment Battery for Children-2, respectively. Results Percentiles ≤ 9, ≤ 5, and < 2 in two or more AP tests had sensitivities (specificities) of 76% (70.6%), 59.3% (76.5%), and 26% (82.4%), respectively, in predicting comorbidities, which were present in 150 of the 167 participants. The criterion of "≤ 9 percentile in two or more AP tests" (Approach I) diagnosed APD in 119 participants, and criterion "≤ 5 percentile in two or more AP tests or ≤ 5 percentile in one AP plus one or more measures of comorbidities" (Approach II) diagnosed 123. The combination of approaches diagnosed 128 participants (76.6%) with APD, of which 114 were diagnosed by each approach (89%). Language impairment and impaired manual dexterity, but not attention-deficit/hyperactivity disorder, predicted APD. Conclusions "Percentile ≤ 9 in two or more AP tests" or "percentile ≤ 5 in one AP plus one or more measures of comorbidities" are evidence-based APD diagnostic criteria. Holistic and interprofessional practice evaluating comorbidities including motor skills is important for APD.

The nature of auditory processing deficits is at the heart of understanding auditory processing disorder (APD) in children. This article reviews evidence that confounding nonsensory factors, including maturation, processing efficiency, and cognition, influence auditory processing in children with APD or language learning impairment. Experimental evidence is presented to show that performance thresholds on nonspeech auditory processing (AP) tests, such as tone detection tasks in noise or in quiet, are poorer in children clinically diagnosed with APD or specific language impairment (SLI), compared to typically developing mainstream school (MS) children. However, with the exception of backward masking, these group differences disappeared for all AP tests after accounting for nonverbal IQ. Intrinsic attention, indexed by variability in AP test performance, was examined alongside AP threshold performance. Generally there was no difference in intrinsic attention across the three participant groups (MS, SLI, APD), but frequency discrimination (FD) was an exception. Thus, although reduced intrinsic attention has been shown to be a factor in the presenting symptoms of APD, including poor listening, speech intelligibility, and communication, there is, surprisingly, no robust evidence that intrinsic attention in children identified with APD or SLI is any poorer than that in typically developing children.

Phoneme discrimination tests based on presenting minimal pairs (MP) are frequently used to assess auditory processing. However test results may be influenced by other factors beside proper acoustic representation. Here we aim at determining whether working memory capacity (WMC) correlates with reproducing sets of MP. WMC was evaluated by memory span for digits in 161 preschool children. MP were either real words or non-words (logatoms). Both real word-MP and logatom-MP were presented in duplets or triplets. Children were asked to repeat what they had heard. Spearman rank correlation was used to analyse the data. All four test item blocks showed a significant positive correlation with WMC (group values). Some children with poor WMC performed sufficiently on MP discrimination and vice versa. Besides confirming the phonological similarity effect, our data indicates a significant interdependence between different processes and phonological representations. This must be taken into account when using MP tests for evaluating "auditory processing" in the clinical routine. However, poor WMC is neither necessary nor obligatory for poor phoneme discrimination.