Electrophysiological Measures of Swallowing Functions: A Systematic Review.

The purpose of this systematic review was to examine the application of event-related potentials (ERPs) to investigate neural processes of swallowing functions in adults with and without dysphagia. Computerized literature searches were performed from three search engines. Studies were screened using Covidence (Cochrane tool) and followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards (PRISMA-2009). A total of 759 studies were initially retrieved, of which 12 studies met inclusion criteria. Electrophysiological measures assessing swallowing functions were identified in two major ERP categories: (1) sensory potentials and (2) pre-motor potentials. Approximately 80% of eligible studies demonstrated strong methodological quality, although most employed a case series or case-control study design. Pharyngeal sensory-evoked potentials (PSEPs) were used to assess pharyngeal afferent cortical processing. The temporal sequence of the PSEP waveforms varied based on the sensory stimuli. PSEPs were delayed with localized scalp maps in patients with dysphagia as compared to healthy controls. The pre-motor ERPs assessed the cortical substrates involved in motor planning for swallowing, with the following major neural substrates identified: pre-motor cortex, supplementary motor area, and primary sensorimotor cortex. The pre-motor ERPs differed in amplitude for the swallow task (saliva versus liquid swallow), and the neural networks differed for cued versus non-cued task of swallowing suggesting differences in cognitive processes. This systematic review describes the application of electrophysiological measures to assess swallowing function and the promising application for furthering understanding of the neural substrates of swallowing. Standardization of protocols for use of electrophysiological measures to examine swallowing would allow for aggregation of study data to inform clinical practice for dysphagia rehabilitation.

A Preliminary Exploration of Pitch Discrimination, Temporal Sequencing, and Prosodic Awareness Skills of Children Who Participate in Different School-Based Music Curricula.

Musical training has been shown to have a positive influence on a variety of skills, including auditory-based tasks and nonmusical cognitive and executive functioning tasks; however, because previous investigations have yielded mixed results regarding the relationship between musical training and these skills, the purpose of this study was to examine and compare the auditory processing skills of children who receive focused, daily musical training with those with more limited, generalized musical training. Sixteen typically developing children (second-fourth grade) from two different schools receiving different music curricula were assessed on measures of pitch discrimination, temporal sequencing, and prosodic awareness. The results indicated significantly better scores in pitch discrimination abilities for the children receiving daily, focused musical training (School 1) compared to students attending music class only once per week, utilizing a more generalized elementary school music curriculum (School 2). The findings suggest that more in-depth and frequent musical training may be associated with better pitch discrimination abilities in children. This finding is important given that the ability to discriminate pitch has been linked to improved phonological processing skills, an important skill for developing spoken language and literacy. Future investigations are needed to determine whether the null findings for temporal sequencing and prosodic awareness can be replicated or may be different for various grades and tasks for measuring these abilities.

P300 Event-Related Potentials Differentiate Better Performing Individuals With Traumatic Brain Injury: A Preliminary Study of Semantic Processing.

OBJECTIVE: To measure the effect of traumatic brain injury on the cognitive processing of words, as measured by the P300, in a semantic categorization task. PARTICIPANTS: Eight adults with a history of moderate to severe traumatic brain injury and 8 age- and gender-matched controls. DESIGN: A pilot study measuring cognitive event-related potentials in response to word pairs that were either in same or different semantic categories. MAIN MEASURES: The P300 (P3b) component of the auditory event-related potential and neuropsychological assessment. RESULTS: Two patterns of P300 amplitude related to brain injury were observed. Participants with poorer performance on neuropsychological tests exhibited reduced P300 amplitude as compared to controls but showed the typical P300 parietal scalp distribution. In contrast, better performing participants demonstrated robust P300 amplitude but a substantially altered scalp distribution, characterized by the recruitment of anterior brain regions in addition to parietal activation. CONCLUSIONS: The recruitment of frontal areas after traumatic brain injury may represent compensatory neural mechanisms utilized to successfully maximize task performance. The P300 in a semantic processing paradigm may be a sensitive marker of neural plasticity that could be used to improve functional outcomes in cognitive remediation paradigms.

The effect of middle age on the late positive component of the auditory event-related potential.

BACKGROUND: We recently described a research study in which age-related changes in interaural asymmetry were elicited using the N400 of the auditory event-related potentials (AERP) (Davis et al, 2013). The N400 was the primary focus due to its sensitivity to various aspects of semantic processing (Kutas and Hillyard, 1984), which we measured using a quasi-dichotic semantic category judgment task in competing speech. In this article, we describe age-related changes that occurred in the late positive component (LPC) of the AERP in the same study. The LPC peak occurs subsequent to the N400 peak on the AERP waveform and has been associated with context updating and further evaluation and processing of stimulus meaning (Juottonen et al, 1996). Neither age group showed significant interaural asymmetry in the LPC. However, a robust age-related difference in LPC scalp topography was observed. PURPOSE: The LPC of the auditory event-related potentials was utilized to evaluate age-related differences in language processing in a quasi-dichotic competing speech task. RESEARCH DESIGN: Electrophysiological responses were obtained on a word-pair semantic categorization task presented through a front loudspeaker while ignoring competing speech that was presented through either left (competition left [CL]) or right (competition right [CR]) loudspeakers. The LPC was compared between young and middle-aged groups in three conditions: side of competition, semantic judgment, and electrode position. STUDY SAMPLE: Twenty young (18-24 yr) and twenty middle-aged (44-57 yr) females with normal hearing sensitivity participated in this study. DATA COLLECTION AND ANALYSIS: Individual, as well as grand-averaged, AERP waveforms and scalp topographies were analyzed in response to the word pairs. The LPC component was subjected to a mixed design analysis of variance (ANOVA) for peak latency and amplitude measures in the latency range of 700-800 msec. Since statistical analyses showed little difference in the LPC component as a function of side of competition, the AERP data were collapsed for the CL and CR conditions. The LPC was analyzed in two ways: first at mid-parieto-central electrode locations, second across midline electrodes from PZ to FZ. RESULTS: Analysis of the mid-parieto-central electrodes showed no amplitude or latency differences for either group or side of competition. The second analysis (across midline electrodes), however, showed a significant amplitude interaction between electrode position and group, indicating that the two age groups were equivalent in the posterior region of the scalp but divergent as electrode site moved frontally. Significant age-related scalp topography differences were found in both semantic judgment conditions. No significant latency differences were found in any condition. CONCLUSIONS: The middle-aged group showed substantially greater LPC peak amplitude in the frontal regions of the scalp than young adults. These results were in concert with N400 results, which suggested that the middle-aged group required more attentional/cognitive resources than young adults in order to maintain a high performance level on a linguistic task in the presence of competing linguistic stimuli (Davis et al, 2013).

Electrophysiological evidence of augmented interaural asymmetry in middle-aged listeners.

BACKGROUND: Various dimensions of auditory processing, especially the perception of speech in the presence of background competition, have been shown to deteriorate with age. A persistent problem in the assessment of these age-related changes has been the high prevalence of age-related high-frequency hearing loss in elderly persons. Some investigators have suggested that a more fruitful approach to the study of age-related decline might be to study middle-aged, rather than elderly, persons, where confounding high-frequency hearing loss is less prevalent. PURPOSE: To determine whether an increase in the left-ear disadvantage (LED) in dichotic listening could be demonstrated in a group of middle-aged persons. RESEARCH DESIGN: The N400 component of the auditory event-related potential (AERP) was utilized to evaluate interaural asymmetry in a quasi-dichotic competing speech task. Electrophysiological responses were obtained on a word-pair semantic categorization task presented through a front loudspeaker while the listener ignored competing speech presented through either left (competition left [CL]) or right (competition right [CR]) loudspeakers. Study Samples: Twenty young (18-24 yr) and 20 middle-aged (44-57 yr) females with normal hearing sensitivity. DATA COLLECTION AND ANALYSIS: Individual, as well as grand-averaged, AERP waveforms and scalp topographies were analyzed for the word pairs. Peak amplitude and latency measures of the N400 component were subjected to a mixed design analysis of variance (ANOVA). RESULTS: No significant interaural asymmetry was found in the AERP waveform for the reference word condition in either age group. In response to the second word of the pair, however, middle-aged females showed significantly greater N400 negativity in the CR condition than in the CL condition. No significant laterality effect was found in the young females. CONCLUSIONS: The study of young versus middle-aged participants may be an effective way of avoiding the confound of high-frequency hearing loss in elderly persons when studying age effects on auditory processing.