Anterior Cruciate Ligament Stability in Soft-Embalmed Cadaver vs In vivo Knee: Alternative Approaches to Medical Education.

Introduction: Soft-embalmed cadavers have been used in medical education with a variety of success in different curriculum objectives. In the United States, the ACL is the most commonly injured ligament. Yet, there has been little focus on the stability of the knee in the sagittal plane provided by the anterior cruciate ligament within the soft-embalmed cadaver model. If the soft-embalmed cadaver ligaments contain similar elastic properties as an in-vivo knees, this will offer yet another means for further advancements in medical education to detect and assess musculoskeletal injuries. Purpose: Evaluate how similarly the anterior tibial translation of soft-embalmed cadaver anterior cruciate ligaments compares to in-vivo tissue. Methods: The KT-1000 arthrometer was used to assess the laxity of the anterior cruciate ligament of thirteen soft-embalmed cadavers consisting of five females and eight males with a mean age of 79.3 years and duration of time since embalming ranging from 250 to 1156 days. Anterior displacement of the tibia in relation to the femur was registered at 67N and 89N. The soft-embalmed cadaver measurements were compared against twenty-one healthy uninjured individuals whose anterior tibial translation was measured using the same process. Data sets were analyzed using a welch two-sample t-test to determine the similarity between the means of the data sets. Results: The t-tests proved a significant difference between live and soft-embalmed cadaver knees. The anterior tibial translation in the set of healthy live knees directly compared to the soft-embalmed cadaver group for 67N depicts an average difference of 1.76mm. The same comparison at 89N depicts an average difference of 2.12mm. Conclusion: While soft-embalmed cadavers may not directly replicate ATT to an exact number to that of in vivo tissue, they still allow the perception of the tibial translation against a stationary femur. The difference is less than 2.5 mm in both data sets when compared to an in-vivo knee, equivalent to one-tenth of an inch. Suggesting the viability of soft-embalmed cadavers ATT and should not exclude their use in medical education.

Performance Monitoring and Cognitive Inhibition during a Speech-in-Noise Task in Older Listeners.

The goal of this study was to examine the effect of hearing loss on theta and alpha electroencephalography (EEG) frequency power measures of performance monitoring and cognitive inhibition, respectively, during a speech-in-noise task. It was hypothesized that hearing loss would be associated with an increase in the peak power of theta and alpha frequencies toward easier conditions compared to normal hearing adults. The shift would reflect how hearing loss modulates the recruitment of listening effort to easier listening conditions. Nine older adults with normal hearing (ONH) and 10 older adults with hearing loss (OHL) participated in this study. EEG data were collected from all participants while they completed the words-in-noise task. It hypothesized that hearing loss would also have an effect on theta and alpha power. The ONH group showed an inverted U -shape effect of signal-to-noise ratio (SNR), but there were limited effects of SNR on theta or alpha power in the OHL group. The results of the ONH group support the growing body of literature showing effects of listening conditions on alpha and theta power. The null results of listening condition in the OHL group add to a smaller body of literature, suggesting that listening effort research conditions should have near ceiling performance.

Impact of Effortful Word Recognition on Supportive Neural Systems Measured by Alpha and Theta Power.

OBJECTIVES: The goal of this study was to use theta and alpha electroencephalography (EEG) frequency power and self-report measures to examine performance monitoring, cognitive inhibition, and perceived effort required for speech understanding in noise. It was hypothesized that with a linear increase in word recognition task difficulty, there would be a linear increase in listening effort and word recognition performance would decrease in the challenging conditions. In addition, theta and alpha power would have an inverted U-shape across easy to challenging listening conditions. The inverted U-shape would reflect the neural underpinnings of listening effort that cannot be measured by task performance alone. DESIGN: EEG data were collected in 34 normal-hearing adults (18 to 33 years old) during the Words-In-Noise (WIN) test, which was presented in sound field. EEG frequency data were averaged and analyzed at three frontal channels for theta power (4 to 8 Hz), which is thought to reflect performance monitoring, and three parietal channels for alpha power (8 to 12 Hz), which is thought to reflect cognitive inhibition. A ten-point visual analog scale was administered after each WIN signal-to-noise ratio (SNR) condition to capture self-reported required and invested listening effort (RLE and ILE, respectively). The WIN SNR conditions were presented in descending and random order. RESULTS: The SNR presentation (descending or random SNR) had a null effect on word recognition performance; however, presentation did have an effect on theta power, alpha power, and ILE. When controlling for presentation, there were significant effects of SNR and presentation on both theta and alpha frequency power. Theta and alpha power had an inverted U-shape as a function of SNR from easy to challenging, with peak power in the moderate SNR conditions. RLE and ILE both significantly increased as task difficulty increased as expected; however, RLE showed a stronger relation to task performance than ILE. Alpha power was a significant predictor of RLE, ILE, and WIN performance when controlling for SNR. CONCLUSIONS: The elevated theta and alpha power in the easy to moderate SNRs and alpha power predicting self-reported listening effort suggest the activation of supportive neural systems during word recognition that could be considered a marker of listening effort. Moreover, the measures of neural support systems and listening effort were independent from task performance, which is a key element to further understanding the neural bases for listening effort. In the context of the broader literature, these results are consistent with (1) a parietal alpha role in supporting inhibitory control to suppress irrelevant information and (2) a frontal theta role in supporting performance monitoring in difficult listening conditions where speech recognition is feasible.

Controlling for Lexical Factors in the Word Auditory Recognition and Recall Measure.

PURPOSE: The purpose of this study was to confirm that lexical factors associated with the Word Auditory Recognition and Recall Measure (WARRM) items have minimal impact WARRM scores. As the WARRM test was designed to minimize the impact of lexical factors, we hypothesized that lexical factors would have no effect on WARRM recognition or recall. METHOD: This report provides a complementary analysis to the original study. Generalized linear mixed models were applied to examine the effects of lexical factors (frequency, neighborhood density, neighborhood frequency) on the WARRM recognition and recall scores. RESULTS: There were no significant effects of lexical factors on WARRM recognition or recall. These null effects were attributed to selection and distribution of words on the WARRM, and the balancing of lexical factors for each set size. CONCLUSIONS: Word selection and test design of the WARRM successfully controlled for potential effects of lexical factors on recognition and recall.

Development of Abbreviated Versions of the Word Auditory Recognition and Recall Measure.

OBJECTIVES: The objective of this study was to develop and evaluate abbreviated versions of the Word Auditory Recognition and Recall Measure (WARRM) as part of an iterative process in the development of a feasible test for potential future clinical use. DESIGN: The three original WARRM (O-WARRM) randomizations were modified by altering the presentation paradigm. Instead of presenting 5 trials per set size with set size increasing from 2 to 6 as in the O-WARRM (n = 100 words), the experimental WARRM (E-WARRM) paradigm consisted of one trial from each of set sizes 2 to 6 to create a "run" (n = 20 words) with each randomization consisting of 5 runs (n = 100 words). A total of 24 younger listeners with normal hearing and 48 older listeners with hearing loss (OHL) were administered 1 randomization of the O-WARRM and 1 different randomization of the E-WARRM. RESULTS: The recognition and recall performances on the O-WARRM and all versions of the E-WARRM (five individual runs and overall) were similar within each listener group, with the younger listeners with normal hearing outperforming the OHL listeners on all measures. Correlation analyses revealed moderate to strong associations between the abbreviated WARRM runs and the O-WARRM for the OHL listener group. Hierarchical regression modeling suggested that run 1 of the E-WARRM was a good predictor of O-WARRM performance and that adding additional runs did not improve the prediction. Taken together, these findings suggest that administering one run from the E-WARRM warrants further examination for clinical use. Additional analyses revealed equivalent scores on all five runs from the three E-WARRM randomizations for both listener groups. CONCLUSIONS: Abbreviated versions of the O-WARRM were developed as part of this study. This was accomplished by modifying the original presentation paradigm and creating 15 unique "runs" among the original 3 randomizations. The resulting 15 runs could be considered 15 unique and abbreviated WARRM lists that have potential, in the future after further studies are conducted to establish important properties, for clinic use. The abbreviated WARRM lists may be useful for quantifying auditory working memory of listeners with hearing loss during the audiologic rehabilitation process.

Evaluating Brain-Computer Interface Performance in an ALS Population: Checkerboard and Color Paradigms.

The objective of this study was to investigate the performance of 3 brain-computer interface (BCI) paradigms in an amyotrophic lateral sclerosis (ALS) population (n = 11). Using a repeated-measures design, participants completed 3 BCI conditions: row/column (RCW), checkerboard (CBW), and gray-to-color (CBC). Based on previous studies, it is hypothesized that the CBC and CBW conditions will result in higher accuracy, information transfer rate, waveform amplitude, and user preference over the RCW condition. An offline dynamic stopping simulation will also increase information transfer rate. Higher mean accuracy was observed in the CBC condition (89.7%), followed by the CBW (84.3%) condition, and lowest in the RCW condition (78.7%); however, these differences did not reach statistical significance ( P = .062). Eight of the eleven participants preferred the CBC and the remaining three preferred the CBW conditions. The offline dynamic stopping simulation significantly increased information transfer rate ( P = .005) and decreased accuracy ( P < .000). The findings of this study suggest that color stimuli provide a modest improvement in performance and that participants prefer color stimuli over monochromatic stimuli. Given these findings, BCI paradigms that use color stimuli should be considered for individuals who have ALS.

Noninvasive brain-computer interface enables communication after brainstem stroke.

Brain-computer interfaces (BCIs) provide communication that is independent of muscle control, and can be especially important for individuals with severe neuromuscular disease who cannot use standard communication pathways or other assistive technology. It has previously been shown that people with amyotrophic lateral sclerosis (ALS) can successfully use BCI after all other means of independent communication have failed. The BCI literature has asserted that brainstem stroke survivors can also benefit from BCI use. This study used a P300-based event-related potential spelling system. This case study demonstrates that an individual locked-in owing to brainstem stroke was able to use a noninvasive BCI to communicate volitional messages. Over a period of 13 months, the participant was able to successfully operate the system during 40 of 62 recording sessions. He was able to accurately spell words provided by the experimenter and to initiate dialogues with his family. The results broadly suggest that, regardless of the precipitating event, BCI use may be of benefit to those with locked-in syndrome.

Bayesian approach to dynamically controlling data collection in P300 spellers.

P300 spellers provide a noninvasive method of communication for people who may not be able to use other communication aids due to severe neuromuscular disabilities. However, P300 spellers rely on event-related potentials (ERPs) which often have low signal-to-noise ratios (SNRs). In order to improve detection of the ERPs, P300 spellers typically collect multiple measurements of the electroencephalography (EEG) response for each character. The amount of collected data can affect both the accuracy and the communication rate of the speller system. The goal of the present study was to develop an algorithm that would automatically determine the necessary amount of data to collect during operation. Dynamic data collection was controlled by a threshold on the probabilities that each possible character was the target character, and these probabilities were continually updated with each additional measurement. This Bayesian technique differs from other dynamic data collection techniques by relying on a participant-independent, probability-based metric as the stopping criterion. The accuracy and communication rate for dynamic and static data collection in P300 spellers were compared for 26 users. Dynamic data collection resulted in a significant increase in accuracy and communication rate.

A general P300 brain-computer interface presentation paradigm based on performance guided constraints.

An electroencephalographic-based brain-computer interface (BCI) can provide a non-muscular method of communication. A general model for P300-based BCI stimulus presentations is introduced--the "m choose n" or C(m (number of flashes per sequence), n (number of flashes per item)) paradigm, which is a universal extension of the previously reported checkerboard paradigm (CBP). C(m,n) captures all possible (unconstrained) ways to flash target items, and then applies constraints to enhance ERP's produced by attended matrix items. We explore a C(36,5) instance of C(m,n) called the "five flash paradigm" (FFP) and compare its performance to the CBP. Eight subjects were tested in each paradigm, counter-balanced. Twelve minutes of calibration data were used as input to a stepwise linear discriminant analysis to derive classification coefficients used for online classification. Accuracy was consistently high for FFP (88%) and CBP (90%); information transfer rate was significantly higher for the FFP (63 bpm) than the CBP (48 bpm). The C(m,n) is a novel and effective general strategy for organizing stimulus groups. Appropriate choices for "m," "n," and specific constraints can improve presentation paradigms by adjusting the parameters in a subject specific manner. This may be especially important for people with neuromuscular disabilities.