Nathan D. Maxfield

Cognitive training and selective attention in the aging brain: An electrophysiological study

OBJECTIVE Age-related deficits in selective attention are hypothesized to result from decrements in inhibition of task-irrelevant information. Speed of processing (SOP) training is an adaptive cognitive intervention designed to enhance processing speed for attention tasks. The effectiveness of SOP training to improve cognitive and everyday functional performance is well documented. However, underlying mechanisms of these training benefits are unknown. METHODS Participants completed a visual search task evaluated using event-related potentials (ERPs) before and after 10 weeks of SOP training or no contact. N2pc and P3b components were evaluated to determine SOP training effects on attentional resource allocation and capacity. RESULTS Selective attention to a target was enhanced after SOP training compared to no training. N2pc and P3b amplitudes increased after training, reflecting attentional allocation and capacity enhancement, consistent with previous studies demonstrating behavioral improvements in selective attention following SOP training. CONCLUSIONS Changes in ERPs related to attention allocation and capacity following SOP training support the idea that training leads to cognitive enhancement. Specifically, we provide electrophysiological evidence that SOP training may be successful in counteracting age-related declines in selective attention. SIGNIFICANCE This study provides important evidence of the underlying mechanisms by which SOP training improves cognitive function in older adults.

Auditory evoked response to gaps in noise: Older adults

Abstract Objective: The objective of this study was to describe the auditory evoked response to silent gaps for a group of older adults using stimulus conditions identical to those used in psychophysical studies of gap detection. Design: The P1-N1-P2 response to the onsets of stimuli (markers) defining a silent gap for within-channel (spectrally identical markers) and across-channel (spectrally different markers) conditions was examined using four perceptually-equated gap durations. Study Sample: A group of 24 older adults (mean age = 63 years) with normal hearing or minimal hearing loss participated. Results: Older adults exhibited neural activation patterns that were qualitatively different and more frontally oriented than those observed in a previous study (20) of younger listeners. Older adults showed longer P2 latencies and larger P1 amplitudes than younger adults, suggesting relatively slower neural travel time and altered auditory inhibition/arousal by irrelevant stimuli. Conclusion: Older adults appeared to recruit later-occurring T-complex-like generators for gap processing, compared to earlier-occurring T-complex-like generators by the younger group. Early and continued processing of channel cues with later processing of gap cues may represent the inefficiency of the aging auditory system and may contribute to poor speech understanding in noisy, real-world listening environments. Sumario Objetivo: El objetivo de este estudio fue describir las respuestas evocadas auditivas ante brechas de silencio para un grupo de adultos mayores utilizando condiciones de estimulación idénticas a aquellas usadas en estudios psico-fisiológicos de detección de brechas. Diseño: Se examinaron las respuestas P1-N1-P2 ante los inicios de estímulos (marcadores) que definen una brecha de silencio en condiciones dentro del canal (marcadores espectralmente idénticos) y entre canales (marcadores espectralmente diferentes), usando cuatro brechas de duración perceptualmente ecualizada. Muestra del Estudio: Participó un grupo de 24 adultos mayores (edad media = 63 años) con audición normal o con una pérdida auditiva mínima. Resultados: Los adultos mayores exhibieron patrones de activación neural que fueron cuantitativamente diferentes y más frontalmente orientados que aquellos observados en un estudio previo (20) con oyentes más jóvenes. Los adultos más viejos mostraron latencias más prolongadas de P2 y amplitudes mayores de P1 que los adultos jóvenes, sugiriendo un tiempo de tránsito en el nervio relativamente más lento y una alteración de la inhibición-estimulación auditiva para estímulos no relevantes. Conclusion: Los adultos mayores parecen reclutar generadores tipo complejo T de aparición tardía para procesamiento de brechas, comparado con los generadores tipo complejo T de aparición más temprana de los adultos jóvenes. Es posible que el procesamiento temprano y complejo de claves por canal, con el procesamiento tardío de claves de brecha, pueda representar la ineficiencia del sistema auditivo que envejece y que contribuye a una pobre comprensión del lenguaje en ambientes de escucha ruidosos del mundo real.

Cortical evoked response to gaps in noise : Within-channel and across-channel conditions

Objectives: The objective of this study was to describe the cortical evoked response to silent gaps in a group of young adults with normal hearing using stimulus conditions identical to those used in psychophysical studies of gap detection. Specifically, we sought to examine the P1-N1-P2 auditory evoked response to the onsets of stimuli (markers) defining a silent gap for within-channel (spectrally identical markers) and across-channel (spectrally different markers) conditions using four perceptually-equated gap durations. It was hypothesized that (1) P1, N1, and P2 would be present and consistent for 1st marker (before the gap) onsets; (2) for within-channel markers, P1, N1, and P2 would be present for 2nd marker (after the gap) onsets only when the gap was of a duration equal to or larger than the behaviorally measured gap detection threshold; and (3) for the across-channel conditions, P1, N1, and P2 would be present for 2nd marker onsets regardless of gap duration. This is expected due to the additional cue of frequency change following the gap. Design: Twelve young adults (mean age 26 years) with normal hearing participated. Within-channel and across-channel gap detection thresholds were determined using an adaptive psychophysical procedure. Next, cortical auditory evoked potentials (P1-N1-P2) were recorded with a 32-channel Neuroscan™ electroencephalogram system using within-channel and across-channel markers identical to those used for the psychophysical task and four perceptually weighted gap durations: (1) individual listeners gap detection threshold; (2) above gap detection threshold; (3) below gap detection threshold; and (4) a 1-ms gap identical to the gap in the standard interval of the psychophysical task. P1-N1-P2 peak latencies and amplitudes were analyzed using repeated-measures analyses of variance. A temporal-spatial principal component analysis was also conducted. Results: The latency of P2 and the amplitude of P1, N1, and P2 were significantly affected by the acoustic characteristics of the 2nd marker as well as the duration of the gap. Larger amplitudes and shorter latencies were generally found for the conditions in which the acoustic cues were most salient (e.g., across-channel markers, 1st markers, large gap durations). Interestingly, the temporal-spatial principal component analysis revealed activity elicited by gap durations equal to gap detection threshold in the latency regions of 167 and 183 ms for temporal-parietal and right-frontal spatial locations. Conclusions: The cortical response to a silent gap is unique to specific marker characteristics and gap durations among young adults with normal hearing. Specifically, when the onset of the 2nd marker is perceptually salient, the amplitude of the P1-N1-P2 response is relatively larger and the P2 latency is relatively shorter than for nonsalient 2nd marker onsets, providing noninvasive, nonbehavioral indicators of the neural coding of this important temporal cue in the thalamic-cortical region of the central auditory system. Gap duration appears to be most clearly indicated by P1 and T-complex amplitude.

Brain responses to filled gaps

An unresolved issue in the study of sentence comprehension is whether the process of gap-filling is mediated by the construction of empty categories (traces), or whether the parser relates fillers directly to the associated verbs argument structure. We conducted an event-related potentials (ERP) study that used the violation paradigm to examine the time course and spatial distribution of brain responses to ungrammatically filled gaps. The results indicate that the earliest brain response to the violation is an early left anterior negativity (eLAN). This ERP indexes an early phase of pure syntactic structure building, temporally preceding ERPs that reflect semantic integration and argument structure satisfaction. The finding is interpreted as evidence that gap-filling is mediated by structurally predicted empty categories, rather than directly by argument structure operations.

Neural correlates of semantic activation spreading on the path to picture naming in adults who stutter.

OBJECTIVE On the path to picture naming, words that relate semantically to the pictured object become activated in the mental lexicon. We used a neuroscientific approach to investigate this semantic activation spreading process in adults who stutter (AWS). METHODS Fourteen AWS and 14 adults who do not stutter (AWNS) completed a picture-word priming task. On each trial, a picture was named at a delay. On some trials, an unattended auditory probe word was presented after the picture, before naming commenced. Event-related potentials recorded to probe words Semantically-Related to the picture labels, and to probe words Semantically- and Phonologically-Unrelated to the picture labels, were compared using spatial-temporal principal component analysis. RESULTS Posterior N400 amplitude was attenuated for Semantically-Related versus Unrelated probes in AWNS, while in AWS posterior N400 amplitude was enhanced for Semantically-Related versus Unrelated probes. Marginal albeit potentially relevant group differences in the morphology of other ERP components were also observed. CONCLUSIONS The posterior N400 results point to a strategic, inhibitory influence on semantic activation spreading in AWS on the path to naming. Group differences in the amplitude of other ERP components tentatively suggest that AWS allocated attentional resources differently than the AWNS during the task. Preliminary ERP evidence of intact conceptual (as opposed to lexical-semantic) priming in the AWS is also discussed. SIGNIFICANCE This study contributes to a growing body of research describing linguistic performance in AWS.

Exploring semantic and phonological picture-word priming in adults who stutter using event-related potentials

OBJECTIVE Our aim was to investigate how semantic and phonological information is processed in adults who stutter (AWS) preparing to name pictures, following-up a report that event-related potentials (ERPs) in AWS evidenced atypical semantic picture-word priming (Maxfield et al., 2010). METHODS Fourteen AWS and 14 typically-fluent adults (TFA) participated. Pictures, named at a delay, were followed by probe words. Design elements not used in Maxfield et al. (2010) let us evaluate both phonological and semantic picture-word priming. RESULTS TFA evidenced typical priming effects in probe-elicited ERPs. AWS evidenced diminished semantic priming, and reverse phonological N400 priming. CONCLUSIONS Results point to atypical processing of semantic and phonological information in AWS. Discussion considers whether AWS ERP effects reflect unstable activation of target label semantic and phonological representations, strategic inhibition of target label phonological neighbors, and/or phonological label-probe competition. SIGNIFICANCE Results raise questions about how mechanisms that regulate activation spreading operate in AWS.

Real-time processing in picture naming in adults who stutter: ERP evidence

OBJECTIVE The aim was to compare real-time language/cognitive processing in picture naming in adults who stutter (AWS) versus typically-fluent adults (TFA). METHODS Participants named pictures preceded by masked prime words. Primes and target picture labels were identical or mismatched. Priming effects on naming and picture-elicited ERP activity were analyzed. Vocabulary knowledge correlations with these measures were assessed. RESULTS Priming improved naming RTs and accuracy in both groups. RTs were longer for AWS, and correlated positively with receptive vocabulary in TFA. Electrophysiologically, posterior-P1 amplitude negatively correlated with expressive vocabulary in TFA versus receptive vocabulary in AWS. Frontal/temporal-P1 amplitude correlated positively with expressive vocabulary in AWS. Identity priming enhanced frontal/posterior-N2 amplitude in both groups, and attenuated P280 amplitude in AWS. N400 priming was topographically-restricted in AWS. CONCLUSIONS Results suggest that conceptual knowledge was perceptually-grounded in expressive vocabulary in TFA versus receptive vocabulary in AWS. Poorer expressive vocabulary in AWS was potentially associated with greater suppression of irrelevant conceptual information. Priming enhanced N2-indexed cognitive control and visual attention in both groups. P280-indexed focal attention attenuated with priming in AWS only. Topographically-restricted N400 priming suggests that lemma/word form connections were weaker in AWS. SIGNIFICANCE Real-time language/cognitive processing in picture naming operates differently in AWS.

Intense piano training on self-efficacy and physiological stress in aging

The aim of this study was to evaluate the effects of an intense piano training program on general self-efficacy, musical self-efficacy, and physiological stress in older adults. Self-efficacy refers to perceived beliefs regarding the performance of domain-specific tasks or activities, which contribute to psychological and physical health. A key challenge is to identify activities that promote self-efficacy in the aging population. Seventeen healthy community-dwelling older adults (60–85 years) with little to no previous musical training participated in a within subjects experimental design. Measures of self-efficacy and cortisol levels were administered over three time points: an initial pre-testing session, a second pre-testing following a two-week no treatment control period, and a post-testing session upon the completion of piano training. Intense piano training consisted of 30 hours of training (3 hours per day) in which high levels of achievement were required. Results of a three-way Repeated Measures ANOVA over all time points with pairwise comparisons revealed significantly (p < .05) enhanced musical self-efficacy post-training, F (2, 32) = 11.5, p < .001, d = .79. No significant changes in general self-efficacy or cortisol levels were found. These results suggest that domain-specific self-efficacy may increase as a result of short-term intense music training; however, short-term music training may not be sufficient to transfer to general self-efficacy.

Attention demands of language production in adults who stutter

OBJECTIVE We investigated whether language production is atypically resource-demanding in adults who stutter (AWS) versus typically-fluent adults (TFA). METHODS Fifteen TFA and 15 AWS named pictures overlaid with printed Semantic, Phonological or Unrelated Distractor words while monitoring frequent low tones versus rare high tones. Tones were presented at a short or long Stimulus Onset Asynchrony (SOA) relative to picture onset. Group, Tone Type, Tone SOA and Distractor Type effects on P3 amplitudes were the main focus. P3 amplitude was also investigated separately in a simple tone oddball task. RESULTS P3 morphology was similar between groups in the simple task. In the dual task, a P3 effect was detected in TFA in all three distractor conditions at each Tone SOA. In AWS, a P3 effect was attenuated or undetectable at the Short Tone SOA depending on Distractor Type. CONCLUSIONS In TFA, attentional resources were available for P3-indexed processes in tone perception and categorization in all distractor conditions at both Tone SOAs. For AWS, availability of attentional resources for secondary task processing was reduced as competition in word retrieval was resolved. SIGNIFICANCE Results suggest that language production can be atypically resource-demanding in AWS. Theoretical and clinical implications of the findings are discussed.

Stress effects on bilingual language professionals' performance

The work of bilingual language professionals (e.g., translators, diplomats, intelligence analysts) involves substantial use of two or more languages, and often, as well, substantial amounts of stress. This stress can come from many sources, including the language tasks themselves and difficult working conditions. Yet, little is known about how the stressors that bilingual language professionals (BLPs) face influence their language performance or affect their daily lives. Here, we present pertinent psychological concepts of stress and coping, suggesting a schema for how they may interact with language performance. We then review what is known about how certain stressors influence language performance and the cognitive factors linked to language performance (attention, memory, self-monitoring), concluding with suggestions for research directions that should enable us better to understand and mitigate the negative effects of stress for BLPs.