Understanding the processes, practices and influences of calibration on feedback literacy in higher education marking: A qualitative study

BACKGROUND

In the University setting, striving for consistency and reliability of assessment evaluation is essential to reducing the impact of marking variations. Marking processes such as consensus calibration have the potential to reduce issues which arise from the influence of markers professional knowledge and experience, as well as fixed and acquired marking habits. Furthermore, the influence of marker feedback which supports learning development is associated with the feedback literacy of both the teacher and the student. A gap is currently present in the literature as these practices are not discussed together.

OBJECTIVES

To explore how nursing academics perceive and understand calibration practices and associated feedback literacy.

DESIGN

Theoretical underpinnings in participatory and person-centred research methodology supported the critical ontological perspective of this study where the intent of the research was to explore the reality that exists within the context where the research was conducted.

SETTING

A single School of Nursing in an Australian University with six campuses spanning metropolitan, regional and rural sites.

PARTICIPANTS

Nursing academics and casual tutors with various levels of experience in assessment marking and feedback.

METHODS

Semi-structured group interviews that were analysed using reflexive thematic analysis.

RESULTS

Four overarching themes were identified; rubrics, calibration, feedback and justice.

CONCLUSION

Calibration improves staff cohesion, fosters better practices and consistency, and permits nuanced interpretation of assessments while maintaining uniformity. Enhanced feedback literacy that integrates principles of equity, justice, and learner-centeredness is required. Fundamentally calibration guides educators toward holistic approaches that foster consistency, equity, and thorough feedback practices.

Effects of simulation-based education module on delirium care in undergraduate nursing students: A quasi-experimental study

AIM

To examine the effects of a delirium education module on undergraduate nursing students' knowledge of and perceived confidence and competence in delirium care.

BACKGROUND

Delirium is common in intensive care units (ICUs) and leads to poor clinical outcomes. The under recognition of delirium is a major problem in ICU medicine. Nurses, as first-line health care providers, can address this by recognizing patients who are experiencing delirium. Since undergraduate nursing students will be the future ICU nurses, it is important to deliver the knowledge regarding delirium care. However, education about assessing delirium in ICUs among undergraduate nursing students is lacking.

DESIGN

Quasi-experimental study.

METHODS

A total of 74 undergraduate students were divided into an intervention group (n=34) and a comparison group (n=40). A 2-hour simulation-based delirium education module integrated into a critical care curriculum was delivered to the intervention group only. The classroom-based intervention was administered at a medical university in northern Taiwan. Study outcomes were measured using a structured survey including (1) a 16-item delirium care knowledge quiz, (2) confidence in delirium care scale and (3) competence in delirium care scale. The survey was distributed to students before and after the module in December 2020. The Mann-Whitney U test, chi-square test and Fisher's exact test were adopted to test the differences of all variables between groups. A generalized estimating equation model was used to investigate the adjusted treatment effects.

RESULTS

The participants had a median age of 22 years and 81% were female. The delirium education module yielded greater knowledge (B = 3.04, 95% confidence interval = 2.20-3.88), confidence (B = 4.20, 95% confidence interval = 2.67-5.73) and competence (B = 4.82, 95% confidence interval = 3.33-6.30) in delirium care when the treatment and control groups were compared.

CONCLUSIONS

For undergraduate nursing students, simulation-based education module is effective in improving the knowledge of and confidence and competence in delirium care. It is recommended that this be included in critical care nursing curricula.

Nursing students' attitudes, behaviour, and knowledge toward smoking cessation: Results from a descriptive survey at a regional university

BACKGROUND

Smoking is the largest single cause of lifestyle-related preventable morbidity and mortality. Nurses form the largest cohort of health professionals and are strategically placed to implement smoking cessation interventions. However their capacity is underutilised, particularly in rural and remote areas in countries such as Australia where the incidence of smoking in is higher than average and access to healthcare is limited. One strategy to address the underutilisation of nurses in smoking cessation interventions is to include training in the university/college nursing curriculum. To effectively implement this training, it is vital to have an in-depth knowledge of student nurses' attitudes towards smoking including the role of healthcare professionals in smoking cessation, their smoking behaviour and that of their peers, and knowledge regarding smoking cessation techniques and resources.

OBJECTIVES

Investigate nursing students' attitudes, behaviour, and knowledge towards smoking cessation, determine the impact of demographics and educational experienced on these, and develop recommendations for future research and educational practice.

DESIGN

Descriptive survey.

PARTICIPANTS

Non-probability sample of undergraduate nursing students (n = 247) from a regional Australian university.

RESULTS

Significantly more participants had tried smoking cigarettes than had not (p = 0.026). There were no significant relationships between gender and smoking (p = 0.169) or e-cigarette use (p = 0.200), but a significant relationship was found between age and smoking status where older participants (48-57 years) were more likely to smoke (p < 0.001). Most participants (70 %) were supportive of public health measures to reduce cigarette smoking but felt that they lacked specific knowledge to assist their patients to cease smoking.

CONCLUSIONS

Within education there needs to be an emphasis on the central role that nurses play in smoking cessation with a greater focus on training nursing students about smoking cessation strategies and resources. There is also a need to ensure that students know it falls within their duty of care to address smoking cessation with patients.

The influence of engaging authentically on nurse-patient relationships: A scoping review

The current international healthcare focus on ensuring the perspectives and needs of individual persons, families or communities are met has led to the core tenet of person-centred care for all. The nurse-patient relationship is central to the provision of care, and enhancing this relationship to ensure trust and respect supports optimal care outcomes for those accessing healthcare services. Engaging authentically is one of the recognised key approaches in person-centred practice, and this scoping review of the literature aims to gain an understanding of the role this process plays in developing effective relationships between nurses and the people they care for. A systematic search of databases and grey literature was undertaken, and twenty-one research papers met the inclusion criteria. A thematic analysis revealed four themes: 'getting to know the patient as a person', 'the complexity of relationship building-it takes time', 'the nurse: characteristics and behaviours that support the nurse-patient relationship' and 'the patient voice'. Nurses and patients both benefit from effective relationships, feeling valued and experiencing greater satisfaction with care. Key elements of engaging authentically were revealed as a nurse-patient relational process through this literature review; however, further research is needed to gain a greater understanding of this concept.

Effect of caffeinated gum on a battery of rugby-specific tests in trained university-standard male rugby union players

Background

Caffeine has been shown to enhance strength, power and endurance, characteristics that underpin performance in rugby. Caffeinated gum has attracted interest as a novel vehicle for delivering caffeine, because absorption of caffeine from gum is quick. Rapid absorption of caffeine may be useful during rugby matches when there is limited time for supplementation such as at half-time or when substitutes enter play. The purpose of this study was to determine whether a low dose of caffeine in gum improves performance in a battery of rugby-specific tests.

Methods

In a double-blind, randomized, placebo-controlled, crossover design, 17 male university-standard rugby players (mass: 85.6 ± 6.3 kg; height: 179.4 ± 6.2 cm; age: 20.4 ± 1.2 years) chewed caffeinated gum (200 mg caffeine) or a placebo gum on two occasions separated by a week. After a standardized warm-up, gum was chewed for 5 min. Subsequently, participants performed three countermovement jumps, followed by an Illinois agility test, 6 × 30 m repeated sprints, and the Yo-Yo IR-2 test; each test was separated by short rest periods.

Results

Caffeinated gum enhanced countermovement jump by 3.6% (caffeine: 43.7 ± 7.6 cm vs. placebo: 42.2 ± 6.2 cm; d = 0.22, 95% CI [0.006, 0.432]; p = 0.044). There was a greater resistance to fatigue during the 6 × 30 m repeated sprint test (fatigue index caffeine: 102.2 ± 0.9% vs. placebo: 103.3 ± 1.2%; d = 1.03, 95% CI [0.430, 1.613]; p = 0.001), and performance on the Yo-Yo IR2 was improved by 14.5% (caffeine: 426 ± 105 m, placebo: 372 ± 91 m; d = 0.55, 95% CI [0.130, 0.957]; p = 0.010). Caffeine gum had no significant effect on the Illinois agility test (caffeine 16.22 ± 1.08 s vs. placebo 15.88 ± 1.09 s; d = − 0.31, 95% CI [− 0.855, 0.240]; p = 0.271).

Conclusions

In university-standard rugby players, a low dose of caffeine (200 mg) supplied in chewing gum enhanced performance on the Yo-Yo IR-2 test and the countermovement jump test and reduced fatigue index during repeated sprints. These improvements in a battery of rugby-specific tests may transfer to enhanced performance in rugby matches.

Dynamic changes in upper limb short latency somatosensory-evoked potentials following stroke in the dominant hemisphere

Repeated upper limb short latency somatosensory-evoked potential (USSEP) studies were performed in 19 post-stroke patients and correlated with the clinical evaluation. Examinations were performed on admission to the rehabilitation centre, and again about 10 weeks later. Data analysis focused on the temporal changes occurring in each patient, and the relationship of these changes to the patient's clinical condition. In seven of the 19 patients, no cortical potentials could be detected on admission or follow-up. These patients had the worst clinical outcome. Whenever a cortical potential was found in the first examination, it was also detected in the second. Dynamic changes between examinations were mainly seen in the central conduction time (CCT) and showed an opposite trend in each hemisphere. In the second examination, the average CCT lengthened over the damaged hemisphere ( p < 0.03) but shortened (insignificantly) over the nonaffected hemisphere, relative to the CCT in the first test. A positive correlation ( p < 0.03) was found between the increase in NI/PI amplitude - measured peak-to-peak between the major negative component (NI) of the cortical response and the subsequent positive wave (PI)-and improvement in communication ability, especially comprehension.

The USSEP can serve as an auxiliary tool in monitoring the recovery process of stroke patients. Changes in USSEP components occur over both hemispheres and may serve as markers of brain plasticity.

Comprehensive analysis suggests simple processes underlying EEG/ERP - demonstration with the go/no-go paradigm in ADHD

BACKGROUND

Current basic or more advanced methods for analysis of averaged EEG/ERP are based on assumptions on the underlying processes, which are not necessarily precise.

NEW METHOD

In this work we present the findings of a method which obviates such assumptions and aims at a comprehensive analysis of the averaged EEG/ERP signal.

RESULTS

For the sake of demonstration we chose the established go/no-go paradigm in the context of ADHD. Our analysis method characterized two spatiotemporally distinct neurophysiologic processes which underlie the sampled signal: one which may be related to attention and the other which may be more related to perception.

COMPARISON WITH EXISTING METHOD(S)

We show how these processes accord with and provide insight on the waveforms reported in the literature.

CONCLUSIONS

Finally we suggest that application of our method on averaged EEG/ERP data sampled from other paradigms may point at a similarly parsimonious set of underlying neurophysiologic processes which underlie the signal.

The effects of subjectively significant stimuli on subsequent cognitive brain activity

OBJECTIVE

To study brain activity modulation by preceding subjectively significant stimuli. Brain activity related to emotional and cognitive processing has been typically traced with fMRI's temporal resolution of seconds. In this study, the time course of activation in the brain areas involved was traced with millisecond temporal resolution.

METHODS

Electrophysiological brain activity was recorded while 12 normal subjects performed an auditory cued attention task, with subjectively significant verbal distracters. Verbal distracters, administered at different times between the cue and the target in one third of the trials, were first names, whose subjective significance was individually assessed after the experiment using a validated questionnaire. Intracranial sources of scalp-recorded electrical activity were estimated and statistical comparisons were conducted to assess the effects and interactions of (1) cue validity; and (2) subjective significance of distracters, on brain activity evoked by the targets.

RESULTS

Significant cue validity effects were found. Language-related areas were most involved following neutral distracters. Emotion-related areas were most involved following subjectively significant distracters. Thus, cue validity and distracter effects seem to have distinct effects.

SIGNIFICANCE

The results indicate an effect of subjectively significant distracters on subsequent brain activity with an interaction between cognitive and emotional processes.

Suicide risk in adolescents with chronic illness: implications for primary care and specialty pediatric practice: a review

Suicide in adolescents is a global tragedy. Research-identified correlates of suicide in youth include depression, academic failure, loss of friends, social isolation, and substance abuse, among others. This review focuses on the potential link between chronic illness in adolescents and increased suicide risk. Research suggests that chronic illness is a risk factor for depression in adolescents that may induce suicide ideation and attempts; however, this risk may be increased even more in young adulthood if the underlying causes of depression are not resolved. This risk needs to be considered against the research data noting an increase in suicide attempts and completions, in each decade of life from adolescence into adulthood. Although more research is clearly needed, it can be concluded that suicide risks are seen in adolescents with chronic illness and all of these young people should be screened for depression and other risk factors for suicide on a regular basis.

The prevalence of congenital and early-onset hearing loss in Jordanian and Israeli infants

The objective of the study was to investigate the prevalence of congenital and early-onset hearing loss, and the influence of the known risk factors for hearing loss on infants in Jordan and Israel. Subjects were a total of nearly 17,000 infants from both countries, including infants with and without risk factors for hearing loss. The hearing screening protocol included distortion product otoacoustic emission, followed in case of repeated OAE referral or high risk (HR) infant by diagnostic auditory brainstem responses. The results indicate that the prevalence and severity of hearing loss amongst Jordanian infants (1.37%) is remarkably higher as compared to the Israeli infants (0.48%). The overall prevalence of bilateral SNHL was seven times more in the Jordanian infants, 18 times in non-risk, and three times in the HR infants relative to the Israeli infants. Risk factors including family history, hyperbilirubinemia, bacterial meningitis, and associated syndromes were more prevalent amongst Jordanian infants. This unique study underscores the importance of sharing and exchanging information to create empirical data to guide health-care providers in adapting protocols to the local constraints in developing countries.

Neurophysiological correlates of subjective significance

OBJECTIVE

The neural substrates of emotional response have traditionally been studied using universal sets of emotionally loaded stimuli, regardless of their subjective significance for the individual subject. Related brain activity has been typically traced with fMRI's temporal resolution of seconds. In this study, unique brain responses to subjectively significant stimuli were analyzed and traced with millisecond temporal resolution.

METHODS

Electrical brain activity (event related potentials) was recorded from 16 normal subjects, to subjectively significant auditory stimuli and its brain sources were imaged. Subjective significance of the stimuli was individually assessed for each subject.

RESULTS

Unique and significant brain activity to subjectively significant stimuli began as early as 200 ms after stimulus onset, with increased brain activity in the vicinity of several brain areas, including frontal gyri, Broca's area, Wernicke's area, insula, precuneus and cingulate gyri. The time course of activity in these areas was traced and found concurrent.

CONCLUSIONS

Although the subjectively significant stimuli of this study were not divided according to their positive or negative affective valence, they elicited a distinct brain response compared to neutral stimuli, with a uniform pattern across subjects.

SIGNIFICANCE

These results demonstrate that subjectively significant stimuli are associated with characteristic brain activity, that studying the neural substrate and time course of processing subjectively significant stimuli is feasible and that the neurophysiological manifestations of emotions are attainable.

Does a nurse-led mental health liaison service for older people reduce psychiatric morbidity in acute general medical wards? A randomised controlled trial

OBJECTIVE

To determine the clinical effectiveness of a nurse-led mental health liaison service in managing mental health problems in older physically ill inpatients.

DESIGN

Randomised controlled trial.

SETTING

Four general medical wards in a district general hospital in a northern UK town.

PARTICIPANTS

153 medically ill older people (aged 65 or over) who scored above the threshold for depression and/or cognitive impairment on a brief screening instrument (4-item geriatric depression scale and 6-item orientation-memory-concentration test): 77 were randomised to a nurse-led intervention and 76 to usual care. Included in the analysis were 120 participants who completed 6-8 week follow-up assessments.

INTERVENTION

Multi-faceted intervention led by a mental health liaison nurse.

MAIN OUTCOME MEASURES

Scores on the Health of the Nation Outcome Scale 65+, the geriatric depression scale, and the Standardised Mini-Mental State Examination.

RESULTS

No significant differences were found between groups on the total Health of the Nation Outcome Scale 65+ scores (11.5 versus 11.5, adjusted mean difference -0.04, 95% CI-1.4 to 1.3, P = 0.96) nor on the Standardised Mini-Mental State Examination (20.3 versus 21.8, adjusted mean difference -0.4, 95% CI-2.1 to 1.3, P = 0.63). Subjects randomised to the intervention arm had significantly lower Geriatric Depression Scale scores at 6-8 week follow-up than those receiving usual care (12.2 versus 14.0, adjusted mean difference -2.0, 95% CI-4.0 to -0.1, P = 0.043).

CONCLUSIONS

Nurse-led mental health liaison services which accept all screened cases from acute medical wards are unlikely to be effective in reducing general psychiatric morbidity. Services which focus on the prevention of delirium and target particular patient groups or disorders such as depression are more likely to be effective.

Validation of short screening tests for depression and cognitive impairment in older medically ill inpatients

OBJECTIVE

To investigate the criterion validity of the four-item Geriatric Depression Scale (GDS4) and the six-item Orientation-Memory-Concentration-test (OMC) against longer widely used screening instruments.

METHOD

Participants were 153 patients (aged 65 or over) admitted to four acute medical wards of a northern UK town. The validity of the GDS4 was determined using the 30-item geriatric depression scale (GDS30) as the comparator; the validity of the OMC was determined using the standardised mini-mental state examination (MMSE) as the comparator. For both screens, the area under receiver operating characteristic (ROC) curve was calculated in addition to the number of true and false positives and the sensitivity and specificity for various cut-off points.

RESULTS

The area under ROC curve was 0.80 for the GDS4 and 0.90 for the OMC. Using a cut-off of 0/1, the GDS4 correctly classified 78.2% of participants, using the GDS30 as the standard. This cut-off gave a sensitivity of 90.1% and specificity of 55.3%. With a cut-off of 1/2 the GDS4 correctly classified 76.8% of participants and had sensitivity and specificity of 78% and 74.5% respectively. The GDS4 and GDS30 were highly correlated (rho=0.63, p < 0.0005). A cut-off of 10/11 on the OMC gave optimum performance. With this cut-off, it correctly classified 85.9% of participants, and had 85.6% sensitivity and 86.8% specificity. There was a significant correlation between the OMC and the SMMSE (rho = -0.827, p < 0.0005).

CONCLUSION

The GDS4 and OMC appear to be useful instruments for screening for depression and cognitive impairment among older medical inpatients.

Ear advantage and attention: an ERP study of auditory cued attention

The neurophysiological manifestations of left ear advantage to tonal stimuli and its interaction with attention have rarely been studied. Cued attention is a behavioral paradigm to assess the behavioral benefits and costs of allocating attention. In this task a cue predicts the location of a subsequent target to which the subject responds. In most cases the cue correctly predicts the target (valid cues) but at times it does not (invalid cues). Cued attention is a spatial paradigm with stimuli presented to either side. The objectives of this study were: (1) to find the neurophysiological correlates of the ear advantage phenomenon and (2) to assess the interaction of the stimulated side (right vs. left ear advantage) with attention, in a cued attention task. Significant effects on event-related potentials (ERPs) in the cued attention task indicated left ear and right hemisphere advantage. Effects were mostly confined to the right hemisphere. The results indicate interactions among left ear advantage, attention and dominant hand utilization. Ear advantage and attention may involve the same neural mechanisms. In spite of the left ear advantage effect on ERP components, hand dominance determines the final behavioral results (reaction times).

Correlations between audiogram and objective hearing tests in sensorineural hearing loss

Owing to its subjective nature, behavioral pure-tone audiometry often is an unreliable testing method in uncooperative subjects, and assessing the true hearing threshold becomes difficult. In such cases, objective tests are used for hearing-threshold determination (i.e., auditory brainstem evoked potentials [ABEP] and frequency-specific auditory evoked potentials: slow negative response at 10 msec [SN-10]). The purpose of this study was to evaluate the correlation between pure-tone audiogram shape and the predictive accuracy of SN-10 and ABEP in normal controls and in patients suffering from sensorineural hearing loss (SNHL). One-hundred-and-fifty subjects aged 15 to 70, some with normal hearing and the remainder with SNHL, were tested prospectively in a double-blind design. The battery of tests included pure-tone audiometry (air and bone conduction), speech reception threshold, ABEP, and SN-10. Patients with SNHL were divided into four categories according to audiogram shape (i.e., flat, ascending, descending, and all other shapes). The results showed that ABEP predicts behavioral thresholds at 3 kHz and 4 kHz in cases of high-frequency hearing loss. Also demonstrated was that ABEP threshold estimation at 3 kHz was not affected significantly by audiogram contour. A good correlation was observed between SN-10 and psychoacoustic thresholds at 1 kHz, the only exception being the group of subjects with ascending audiogram, in which SN-10 overestimated the hearing threshold.

Time course of motor excitability before and after a task-related movement

AIMS OF THE STUDY

The time course of motor excitability during a task-related unilateral right thumb movement was studied using sub-threshold transcranial magnetic stimulation (TMS) to the contralateral left motor cortex. The level of stimulation evoked a motor evoked potential (MEP) in the thumb when the subject was at rest in approximately 10% of the trials.

METHODS

Subjects made a brief right thumb movement to the predictable omission of regularly presented tone bursts allowing experimental definition of TMS relative to the cue to move. Motor cortical excitability was characterized by amplitude and/or probability of eliciting MEPs.

RESULTS

There were four periods of altered motor excitability during task performance compared to a control resting state: a first period of weak facilitation before movement between -500 to -200 ms, a second period without increased excitability approximately 150 ms before movement onset when MEPs amplitude was below that seen in rest, a third period of strong facilitation between -100 ms before movement and +200 ms after facilitation and a fourth period of weak facilitation between +200 to +500 ms.

CONCLUSION

These results show that during performance of a task requiring a motor response, motor cortical excitability is increased above resting for hundreds of millisecond before and after the response, except for a transient period between 75 and 150 ms prior to movement onset. The temporal pattern of these excitability changes is compatible with multiple excitatory and inhibitory inputs interacting on motor cortex.

Otoacoustic emissions and brainstem evoked potentials in compound carriers of connexin 26 mutations

This study compares the effects of mutations in the gap junction protein connexin 26 (Cx26), on outer hair cells (OHCs), inner hair cells (IHCs) and auditory nerve/brainstem among carriers of these mutations. One hundred and twenty eight individuals, from a village with widespread consanguinity and congenital deafness, due to three Cx26 mutations, were selected among relatives of deaf persons, and divided into non-carriers, carriers of one mutation, homozygous to one mutation, or compound heterozygous carriers of two different mutations. Distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABRs) and audiometric evaluation were compared in these genetic groups. Hearing loss among homozygotes and compound heterozygotes was comparable and ranged from mild to profound. Most ABRs from these groups showed no responses or partial responses (peaks III, V) with prolonged latencies, but some individuals had all peaks at normal latencies. DPOAEs were absent, except sporadic responses. Carriers of one mutation had significantly smaller DPOAEs compared to non-carriers, although normal pure tone audiograms and ABRs were found in these groups. In conclusion, based on DPOAEs, Cx26 mutations may impact OHC function among carriers of one or two Cx26 mutations. IHC/nerve impairment among homozygotes and compound heterozygotes is variable. OHCs may be more susceptible to Cx26 mutations compared to IHCs and the auditory nerve and brainstem pathway activated by them.

Preparatory slow potentials and event-related potentials in an auditory cued attention task

OBJECTIVES

To examine reaction times and event-related potentials (ERPs) in an auditory cued attention task varying motor requirements, cue validity, and cue location.

METHODS

Subjects (n=13) listened to cue-target stimulus pairs. Verbal cues (monaural, binaural) indicated the ear to receive a target tone 1.5s later. Cues correctly (valid) or incorrectly (invalid) predicted target ear, or were uninformative (neutral). In separate conditions subjects either responded by pressing one of two buttons, or did not respond to targets. ERPs for cues and targets (P50, N100, P200, late slow wave), and negative slow potentials between cues and targets were assessed.

RESULTS

Target reaction times for valid cues were significantly shorter than for invalid cues, with intermediate values for neutral cues. When no motor response was required larger ERPs were seen to both cues and targets. Negative slow potentials had larger amplitudes before target presentation when subjects responded to targets; and were larger following neutral, vs. valid/invalid, cues. ERPs (N100, P200) to invalidly cued targets were significantly larger and a subsequent late slow wave was more positive, relative to validly cued targets.

CONCLUSIONS

Expectancy for targets begins shortly after cue presentation, and is affected by both motor requirements and the information content of the cue. ERP amplitudes to targets are modulated by the correspondence between cue information and actual target location.

Echo suppression in the human cortex is affected by the spatial and temporal proximity of the primary sound and echo

Echo suppression in the human auditory cortex was studied with auditory middle latency evoked potentials (AMEP) using virtual reality acoustic stimuli, including distance and elevation cues, presented by earphones. The purpose of the study was to assess the effect of proximity of the source sound and echo on the degree of echo suppression. Sixteen subjects were presented with source-echo pairs in which the preceding source sound was always at the vertex, and the echo varied among ten positions on the coronal plane. Positions varied in elevation, distance and time lag between source and echo. The psychoacoustic location judgment of the fused source-echo pair was closer to the source sound (more echo suppression) the nearer the echo drew to the source in its elevation and time. The equivalent dipole magnitudes of the cortical components of AMEP were significantly reduced (more suppression) with shorter echo lags and when echo elevation was similar to that of the source sound. The distances used in this study did not significantly affect echo suppression. These results indicate that echo suppression in the auditory cortex is more pronounced the closer are the primary sound and echo in locational attributes and timing. As source sound and echo draw apart, echo suppression in the cortex decreases and the perceived localization of the fused source-echo is more biased toward the echo.

The effects of a connexin 26 mutation--35delG--on oto-acoustic emissions and brainstem evoked potentials: homozygotes and carriers

The purpose of this study was to examine whether outer hair cells (OHCs), inner hair cells and the brainstem auditory pathway are impaired due to a mutation in a gap junction protein, connexin 26 (Cx26), 35delG. Fifty-six individuals, from a village with widespread consanguinity and profound, non-syndromic congenital deafness, due to 35delG mutation, were selected among relatives of deaf people. The individuals were either non-carriers (n=20), heterozygous (n=20) or homozygous (n=16) for the mutation. Distortion product oto-acoustic emissions (DPOAEs) and auditory brainstem evoked potentials (ABEPs) in mutation non-carriers, in heterozygotes (carriers) and in subjects homozygous for the mutation were compared in addition to audiometric evaluation. Most deaf homozygotes had no DPOAEs, except some sporadic responses at 1000, 8000 and 10000 Hz. This was also observed in audiometry which showed profound hearing loss in most cases. Two cases were unique: one had moderate to severe hearing loss and the other had severe to profound hearing loss. A significant difference was found between non-carriers and carriers of 35delG: non-carriers had larger DPOAE responses than heterozygotes at all frequencies. The prevalence of responses got lower with higher frequencies in both groups, but between 6000 and 10000 Hz 50-70% of the carriers had no DPOAE responses, compared to 30-60% of non-carriers. In both groups responses diminished with age, but no significant interaction was found between age and the genetic group. ABEPs among homozygotes were variable: in most homozygotes ABEPs were absent or partial (waves III, V) with prolonged latencies, but two subjects had ABEPs within normal limits, in one ear. ABEPs were normal with no differences between carriers and non-carriers. We suggest that OHC function is affected by the 35delG mutation in Cx26. In addition, the hearing of carriers of this mutation may be impaired at very high frequencies (8000-10000 Hz), which are not assessed in routine audiometry or ABEP testing.

Influence of task-related ipsilateral hand movement on motor cortex excitability

OBJECTIVE

The time course of the right motor cortex excitability in relation to a task-related voluntary right thumb twitch was studied using sub-threshold transcranial magnetic stimulation (TMS) to the right motor cortex.

METHODS

Motor excitability was studied in 8 adult subjects who made a brief right thumb twitch to the predictable omission of every fifth tone in a series of tones 2.5 s apart. This paradigm avoided an overt sensory cue, while allowing experimental control of TMS timing relative to both movement and the cue to move. Motor excitability was characterized by several measures of motor evoked potentials (MEPs) recorded from the left thenar eminence in response to TMS over the right scalp with a 9 cm coil: probability of eliciting MEPs, incidence of MEPs and amplitude of MEPs.

RESULTS

All subjects showed suppression of motor excitability immediately following a voluntary right thumb twitch (ipsilateral response), and up to 1 s after it. However, two distinctly different effects on motor excitability were observed before the response: two subjects showed excitation, beginning about 500 ms before response until 300 ms after it, followed by the post-movement suppression; 6 subjects displayed pre-movement suppression, beginning about 600 ms before the response and persisting for the duration.

CONCLUSIONS

The net effect of an ipsilateral response on motor cortex can be either inhibitory or excitatory, changing with time relative to the response. These findings are compatible with two separate processes, inhibitory and excitatory, which interact to determine motor excitability ipsilateral to the responding hand.

The varieties of auditory neuropathy

Auditory neuropathy (AN) was initially described as impairment of auditory neural function, with preserved cochlear hair cell function. In this report, 67 patients with audiological and neurophysiological criteria for hearing loss due to auditory neuropathy are described. Reviewing this large body of patients, AN appears to consist of a number of varieties, with different etiologies and sites affected. All varieties share a relatively spared receptor function, and an impaired neural response, with diminished ability to follow fast temporal changes in the stimulus, but different varieties in this general scheme can be distinguished. Analyses of the clinical features indicate that auditory neuropathies vary in several measures including age of onset, presence of peripheral neuropathy, etiology, and behavioral and physiological measures of auditory function. The sites affected along the peripheral auditory pathway may include dysfunction of the outer hair cells, the synapse between hair cell and auditory nerve, and the auditory nerve fibers, with myelin as well as axonal impairments contributing to the disorder.

The mode of short-term memory encoding as indicated by event-related potentials in a memory scanning task with distractions

OBJECTIVE

Auditory event-related potentials (ERPs) were recorded during the performance of a memory scanning task, with and without distracters between the memorized items and the probe. The effect of distracters with different phonological/semantic characteristics was tested, to indicate the encoding mode in short-term memory.

METHODS

Three types of sets ('memorized sets') were presented to the subject before the probe: 4 memorized digits, two memorized digits with two distracter digits and two memorized digits with two noise distracters. Potentials in response to the set items were averaged separately according to stimulus type and position in the set. Potentials in response to the probe were averaged according to the preceding stimulus sequence: 4 memorized digits, two distracter digits or two noise distracters.

RESULTS

The early components (N1, P2) differed between distracter items and memorized items, indicating lower attention allocation to distracter items. In contrast, the late components (N2, P3) indicated similar processing of distracters and memorized items. Behavioral measures indicated shorter scanning times of sets with distracters. The early ERP components in response to the probe (P2, N2) indicated differences among probes according to the preceding combinations of memorized items and distracters. The late component (P3) indicated different speeds (latencies) of scanning and comparison for series with compared to without distracters, but similar processing resource allocation (amplitudes). Processing was prolonged when the distracter items were phonological.

CONCLUSIONS

This study shows that distracters affect both the memorization process and the scanning and comparison in short-term memory. The stronger distraction by stimuli that are phonologically similar to the memorized items supports phonological processing in short-term memory.

Short latency visual evoked potentials in occupational exposure to organic solvents

OBJECTIVES

Short latency visual evoked potentials (SVEP), in response to high-intensity flashes from light emitting diodes (LED), were used to detect subclinical effects along the visual pathway in four groups of subjects with different levels of exposure to gasoline, all within legally acceptable limits.

METHODS

Potentials and exposure levels were obtained from 31 subjects with different occupational exposure levels to gasoline fumes, as well as from 17 non-exposed control subjects. SVEP were recorded from four electrode sites (infra-orbital, Cz, Pz, Oz), in response to flashes presented to each eye in turn from goggle-mounted LEDs. SVEP components were defined after digital filtering, which eliminated the high-frequency oscillatory potentials and accentuated five major components: a periocular P30, attributed to the retina; a fronto-central N50, attributed to the optic nerve; centro-parietal P65 and N85, attributed to the optic tracts and radiation; and an occipital, cortical P105.

RESULTS

The latencies of successive SVEP components of the exposed subjects showed a significant latency prolongation compared to controls, beginning with activity attributed to the optic nerve and increasing cumulatively with the later components. Retinal components were not affected by the exposure to organic solvents. Among the exposed groups, differences in latency prolongation corresponded to occupational exposure.

CONCLUSION

The low-frequency components of SVEP were reliably measured and proved to be sensitive to subclinical effects of organic solvents on conduction along the visual pathway. These components are likely to be sensitive to other subcortical visual pathway lesions, but their clinical promise needs further verification.

Overcoming selective ensemble averaging: unsupervised identification of event-related brain potentials

We present a novel approach to the problem of event-related potential (ERP) identification, based on a competitive artificial neural network (ANN) structure. Our method uses ensembled electroencephalogram (EEG) data just as used in conventional averaging, however without the need for a priori data subgrouping into distinct categories (e.g., stimulus- or event-related), and thus avoids conventional assumptions on response invariability. The competitive ANN, often described as a winner takes all neural structure, is based on dynamic competition among the net neurons where learning takes place only with the winning neuron. Using a simple single-layered structure, the proposed scheme results in convergence of the actual neural weights to the embedded ERP patterns. The method is applied to real event-related potential data recorded during a common odd-ball type paradigm. For the first time, within-session variable signal patterns are automatically identified, dismissing the strong and limiting requirement of a priori stimulus-related selective grouping of the recorded data. The results present new possibilities in ERP research.

Sound lateralization and interaural discrimination. Effects of brainstem infarcts and multiple sclerosis lesions

Subjects with brainstem lesions due to either an infarct or multiple sclerosis (MS) underwent two types of binaural testing (lateralization testing and interaural discrimination) for three types of sounds (clicks and high and low frequency narrow-band noise) with two kinds of interaural differences (level and time). Two major types of abnormalities were revealed in the lateralization performances: perception of all stimuli, regardless of interaural differences (time and/or level) in the center of the head (center-oriented), or lateralization of all stimuli to one side or the other of the head (side-oriented). Similar patterns of abnormal lateralization (center-oriented and side-oriented) occurred for MS and stroke patients. A subject's pattern of abnormal lateralization testing was the same regardless of the type of stimulus or type of interaural disparity. Lateralization testing was a more sensitive test than interaural discrimination testing for both types of subjects. Magnetic resonance image (MRI) scanning in three orthogonal planes of the brainstem was used to detect lesions. A semi-automated algorithm superimposed the auditory pathway onto each MRI section. Whenever a lesion overlapped the auditory pathway, some binaural performance was abnormal and vice versa. Given a lateralization test abnormality, whether the pattern was center-oriented or side-oriented was mainly determined by lesion site. Center-oriented performance was principally associated with caudal pontine lesions and side-oriented performance with lesions rostral to the superior olivary complex. For lesions restricted to the lateral lemniscus and/or inferior colliculus, whether unilateral or bilateral, just noticeable differences (JNDs) were nearly always abnormal, but for caudal pontine lesions JNDs could be normal or abnormal. MS subjects were more sensitive to interaural time delays than interaural level differences particularly for caudal pontine lesions, while stroke patients showed no differential sensitivity to the two kinds of interaural differences. These results suggest that neural processing of binaural stimuli is multilevel and begins with independent interaural time and level analyzers in the caudal pons.

Contribution of click frequency bands to the human binaural interaction components

The purpose of this study was to determine the contribution of click frequency bands (broad-band, >2000 Hz, <2000 Hz and <1000 Hz) to binaural interaction components (BICs) of the human auditory brainstem evoked potentials (ABEPs). The human BICs were studied by subtracting the potentials to binaural clicks from the algebraic sum of monaurally evoked potentials to either ear. Effective frequency bands were derived using clicks alone or clicks with ipsilateral or binaural masking noise, high- or low-pass filtered at different cut-off frequencies. Analysis included single-channel vertex-cervical spinous process VII derivation of BIC and ABEP, as well as estimating the single, centrally located dipole equivalent of the surface activity from three orthogonally positioned electrode pairs, using the three-channel Lissajous' trajectory (3-CLT) analysis. All BIC 3-CLTs included three major components (labeled BdII, BeI, and BeII) approximately corresponding in latency to IIIn, V and VI ABEP peaks. All apex latencies of BIC 3-CLT, except BeI, were longer in response to <2000 Hz and <1000 Hz (low-frequency) effective clicks. Apex amplitude of components BeI and BeII of BIC 3-CLT were smaller with low-frequency effective clicks than with broad-band or high-frequency (>2000 Hz) clicks. We suggest that binaural interaction component BeI is mainly tuned to high frequencies, showing no frequency effect on latency, and decreasing in amplitude with decreasing click high frequency content. In contrast, BdII and BeII of the human BICs are evoked more synchronously by high-frequency binaural inputs, but are also sensitive to low frequencies, increasing in latency according to the cochleotopic activation pattern. These differences between BIC components may reflect their roles in sound localization.

Auditory brain-stem evoked potentials in patients with thyroid and parathyroid dysfunction: adaptation to chronic hormonal dysequilibrium

Auditory Brainstem Evoked Potentials (ABEPs) and pure tone audiograms were obtained from 24 patients with parathyroid dysfunction (17 hypercalcemia and 7 hypocalcemia) and 12 patients with thyroid dysfunction (6 hyperthyroid and 6 hypothyroid) and from 10 control subjects. ABEPs were characterized by I-V interpeak latency difference at 10/sec click rate and by the effect of increasing stimulus rate to 55/sec. None of the ABEP measures were significantly affected by levels of serum calcium, thyroid hormones or their interactions. Moreover no correlation was found between biochemical and electrophysiological measures. This stability of ABEP measures contrasts with earlier reports on acute effects of calcium and thyroid hormonal levels on auditory brainstem evoked potentials. We propose that chronic calcium or thyroid hormonal homeostatic changes are associated with adaptive mechanisms resulting in normal function of the auditory brainstem.

'Oddball' event-related potentials and information processing during REM and non-REM sleep

Auditory stimuli consisting of the subject's own name and an irrelevant word, counterbalanced in probabilities, were presented to 15 male subjects in the awake state and during natural sleep. Potentials recorded to these stimuli, as well as to clicks presented during sleep in a preceding night, were recorded and compared. Principal component analysis (PCA) was conducted on evoked potentials to distinguish temporally overlapping components, and ANOVA was applied on the eigenvector coefficients. During non-REM sleep a parietal P450, more prominent in stage 2, was observed in addition to the prominent waveform of a K-complex, which was also recorded in response to clicks and consisted of N350, N550 and P1000. During REM sleep, a fronto-central negativity which resembled non-REM N350, a parietal positivity at about 450 ms and a large N700 were detected. ANOVA on PCA coefficients showed a significant effect of verbal-stimulus type (name/irrelevant) on an eigenvector, which included all the components observed during stage 2 sleep. Coefficients during REM sleep showed a significant effect of stimulus probability on an eigenvector consisting of a prominent P450, suggesting a resemblance to the awake P300 component. This could not be demonstrated during non-REM sleep. The results indicate continued evaluation of auditory input salience during sleep, which diminishes during deep sleep, and is replaced by evaluation of stimulus context in a train of stimuli during REM sleep.

Evidence for efferent effects on early components of the human auditory brain-stem evoked potentials

OBJECTIVES AND METHODS

Auditory brain-stem evoked potentials (ABEPs) were recorded from 10 normal hearing subjects in response to rarefaction clicks, presented at a rate of 11/s. Stimuli were binaurally symmetrical and isochronic at 75 dB peSPL or with interaural time disparities (ITDs) of +/-0.4 ms, or intensity disparities (IIDs) of +/-10 dB. Potentials were recorded from vertex-neck, as well as from 3 orthonormally positioned differential derivations. The amplified potentials were averaged over 8000 repetitions using a dwell time of 20 micros/address/channel. The effects of contralateral stimulation on neural responses of the peripheral auditory system were obtained by subtracting the binaural response from the algebraic sum of responses to left and right monaural stimuli. From the 3 orthonormal derivations, 3-channel Lissajous' trajectories (3-CLTs) to the various stimulus conditions and difference waveforms were derived.

RESULTS

The results corroborated earlier studies on binaural interaction components (BICs), which include 3 major components corresponding in latency to the vertex-mastoid peaks IV-VI of ABEP. In addition, the binaural difference waveforms included 3 earlier, low-amplitude components. Latency correspondence and comparison of difference waveform and ABEP 3-CLTs indicated that the first and third early difference waveform components corresponded to the negative peaks following I and III, respectively, of the vertex-neck ABEP to binaural clicks.

CONCLUSIONS

These results indicate that early ABEP peaks, generated peripheral to binaural convergence, may be affected by contralateral stimulation. These contralateral effects were in a pattern compatible with suppression. most probably by efferents of the olivo-cochlear bundle.

Effects of localized pontine lesions on auditory brain-stem evoked potentials and binaural processing in humans

OBJECTIVES AND METHODS

Four sets of measurements were obtained from 11 patients (44-80 years old) with small, localized pontine lesions due to vascular disease: (1) Monaural auditory brain-stem evoked potentials (ABEPs; peaks I to VI); (2) Binaural ABEPs processed for their binaural interaction components (BICs) in the latency range of peaks IV to VI; (3) magnetic resonance imaging (MRI) of the brain-stem; and (4) psychoacoustics of interaural time disparity measures of binaural localization. ABEPs and BICs were analyzed for peak latencies and interpeak latency differences. Three-channel Lissajous' trajectories (3-CLTs) were derived for ABEPs and BICs and the latencies and orientations of the equivalent dipoles of ABEP and BICs were inferred from them.

RESULTS

Intercomponent latency measures of monaurally evoked ABEPs were abnormal in only 3 of the 11 patients. Consistent correlations between sites of lesion and neurophysiological abnormality were obtained in 9 of the 11 patients using 3-CLT measures of BICs. Six of the 11 patients had absence of one or more BIC components. Seven of the 11 had BICs orientation abnormality and 3 had latency abnormalities. Trapezoid body (TB) lesions (6 patients) were associated with an absent (two patients with ventral-caudal lesions) or abnormal (one patient with ventral-rostral lesions) dipole orientation of the first component (at the time of ABEPs IV), and sparing of this component with midline ventral TB lesions (two patients). A deviant orientation of the second BICs component (at the time of ABEPs V) was observed with ventral TB lesions. Psychoacoustic lateralization in these patients was biased toward the center. Rostral lateral lemniscus (LL) lesions (3 patients) were associated with absent (one patient) or abnormal (two patients) orientation of the third BICs component (at the time of ABEPs VI); and a side-biased lateralization with behavioral testing.

CONCLUSIONS

These results indicate that: (1) the BICs component occurring at the time of ABEPs peak IV is dependent on ventral-caudal TB integrity; (2) the ventral TB contributes to the BICs component at the time of ABEPs peak V; and (3) the rostral LL is a contributing generator of the BICs component occurring at the time of ABEP peak VI.

Binaural masking level difference in human binaural interaction components

OBJECTIVE

The purpose of this study was to compare the effects of monaural and binaural broadband masking noise on binaural interaction components (BICs) of the human auditory brain stem evoked potentials (ABEPs).

DESIGN

The BICs of the human ABEPs were studied by subtracting the potentials to binaural clicks from the algebraic sum of monaurally evoked potentials to clicks alone or to clicks with ipsilateral monaural or binaural broadband masking noise. Alternating polarity, 11/sec clicks were presented at 65 dB nHL, and noise was presented at 45 dB nHL. Analysis included peak-to-prestimulus baseline amplitudes and latencies of BICs' peaks and troughs from the vertex-mastoid (A) and vertex-neck (Z) channels. In addition, 3-channel Lissajous' trajectory (3-CLT) analysis, estimating the single, centrally located dipole equivalent of surface activity, was performed on data recorded from three orthogonally positioned electrode pairs. 3-CLT measures included apex latency, amplitude, and orientation, as well as planar segment duration, size, shape, and orientation.

RESULTS

All BICs 3-CLTs included five main components (labeled BdI, BdII, BdIII, BeI, and BeII). In general, apex latencies were longer with masking noise. However, BdII and BeI apex latencies were shorter with binaural than with ipsilateral monaural masking noise. Apex amplitude and planar segment size of component BeI, as well as P1 peak amplitude in BICs of the Z-channel records, were larger with binaural than with monaural noise. No significant difference between the monaural and binaural noise conditions was found in durations, shapes, and orientations of planar segments of BICs 3-CLT, nor in peak latency of BICs in the A- and Z-channel records.

CONCLUSIONS

We suggest that these effects on the latency and amplitude of BICs reflect binaural processing in the human brain stem. In particular, the larger amplitudes and shorter latencies of P1 and BeI with binaural than with ipsilateral monaural masking may be associated with the psychophysical effect of binaural masking level difference.

Evidence for primary auditory cortex involvement in the echo suppression precedence effect: a 3CLT study

An echo lagging shortly after a source and arising from another direction perceptually blends with the source, and the location of the fused 'source-echo' is dominated by the source location (the Precedence Effect). The neural substrates underlying the echo localization suppression are ambiguous. We recently suggested an auditory evoked potentials correlate of binaural echo lateralization suppression. A significant and specific reduction in binaural peak amplitude and area of the echo-evoked middle-latency component Pa was observed. The binaural echo-Pa suppression depended on echo lag and correlated with the psychophysical echo lateralization suppression. In this study, the echo-Pa generators were analyzed with 3CLT spatio-temporal analysis, in order to suggest the neural substrates involved in echo lateralization suppression. 3CLT enables reliable identification of components, based on rigid geometrical properties. The results suggest that the Pa1 subcomponent of Pa, associated with primary auditory cortex activity, fully accounts for the echo-Pa suppression. This physiological indication for primary auditory cortex involvement in the precedence effect is the first in humans.

The effect of binaural masking noise disparity on human auditory brainstem binaural interaction components

The binaural interaction components (BIC) of the human auditory brainstem responses have been associated with sound lateralization which involves analyzing correlated inputs from the two ears. To test the hypothesis that BIC generators are specifically sensitive to binaural, correlated sounds, the effects of monaural and binaural correlated and uncorrelated masking on BIC to clicks were compared. Analysis included peak-to-prestimulus baseline amplitudes and latencies of BIC peaks from the vertex-mastoid ('A') and vertex-neck ('Z') channels, as well as the three-channel Lissajous trajectory (3-CLT) measures. Trajectory amplitudes of BIC BdIII, BeI and BeII were significantly suppressed by correlated (but not by uncorrelated) binaural noise, when compared with the unmasked condition. Moreover, component BdIII was more affected by masking with correlated than with uncorrelated binaural noise. Overall, binaural noise was more effective in suppressing BIC then monaural noise, and interaurally correlated binaural noise was more effective than uncorrelated binaural noise. These results are compatible with BIC generation by a binaurally activated subset of central auditory neurones which is sensitive to interaurally correlated sounds. Such a subset has been associated with the superior olivary complex and is assumed to be involved in sound lateralization.