Middle Latency Auditory Evoked Potentials Research Articles

Prognostication after cardiac arrest: how EEG and evoked potentials may improve the challenge.

About 80% of patients resuscitated from CA are comatose at ICU admission and nearly 50% of survivors are still unawake at 72h. Predicting neurological outcome of these patients is important to provide correct information to patient's relatives, avoid disproportionate care in patients with irreversible hypoxic-ischemic brain injury (HIBI) and inappropriate withdrawal of care in patients with a possible favorable neurological recovery. ERC/ESICM 2021 algorithm allows a classification as "poor outcome likely" in 32%, the outcome remaining "indeterminate" in 68%. The crucial question is to know how we could improve the assessment of both unfavorable but also favorable outcome prediction. Neurophysiological tests, i.e., electroencephalography (EEG) and evoked-potentials (EPs) are a non-invasive bedside investigations. The EEG is the record of brain electrical fields, characterized by a high temporal resolution but a low spatial resolution. EEG is largely available, and represented the most widely tool use in recent survey examining current neuro-prognostication practices. The severity of HIBI is correlated with the predominant frequency and background continuity of EEG leading to "highly malignant" patterns as suppression or burst suppression in the most severe HIBI. EPs differ from EEG signals as they are stimulus induced and represent the summated activities of large populations of neurons firing in synchrony, requiring the average of numerous stimulations. Different EPs (i.e., somato sensory EPs (SSEPs), brainstem auditory EPs (BAEPs), middle latency auditory EPs (MLAEPs) and long latency event-related potentials (ERPs) with mismatch negativity (MMN) and P300 responses) can be assessed in ICU, with different brain generators and prognostic values. In the present review, we summarize EEG and EPs signal generators, recording modalities, interpretation and prognostic values of these different neurophysiological tools. Finally, we assess the perspective for futures neurophysiological investigations, aiming to reduce prognostic uncertainty in comatose and disorders of consciousness (DoC) patients after CA.

Etiology matters for neuroprognostication: A multimodal electrophysiological investigation in a case of Bickerstaff's brainstem encephalitis

We report the case of a 19-year-old patient with an acute-onset non-traumatic coma. Brain MRI scan was normal, CSF showed mild pleocytosis and moderately elevated protein, and continuous EEG-monitoring was compatible with spindle-coma. Cortical somatosensory evoked potentials (SSEPs) and middle-latency auditory evoked potentials (MLAEPs) were bilaterally absent, and brainstem auditory evoked potentials suggested a brainstem dysfunction. Serum anti-GQ1b and anti-GT1a IgG antibodies positivity suggested Bickerstaff's brainstem encephalitis (BBE). The clinical and functional outcomes were favorable and normal cortical SSEPs/MLAEPs reappeared in a few weeks. Based on this report, in cases of unexplained MRI-negative coma with neurophysiological evidence of brainstem dysfunction, BBE should be eliminated before considering withdrawal of life-sustaining therapy (WLST).

Longitudinal auditory pathophysiology following mild blast-induced trauma.

Blast-induced hearing difficulties affect thousands of veterans and civilians. The long-term impact of even a mild blast exposure on the central auditory system is hypothesized to contribute to lasting behavioral complaints associated with mild blast traumatic brain injury (bTBI). Although recovery from mild blast has been studied separately over brief or long time windows, few, if any, studies have investigated recovery longitudinally over short-term and longer-term (months) time windows. Specifically, many peripheral measures of auditory function either recover or exhibit subclinical deficits, masking deficits in processing complex, real-world stimuli that may recover differently. Thus, examining the acute time course and pattern of neurophysiological impairment using appropriate stimuli is critical to better understanding and intervening in bTBI-induced auditory system impairments. Here, we compared auditory brainstem response, middle-latency auditory-evoked potentials, and envelope following responses. Stimuli were clicks, tone pips, amplitude-modulated tones in quiet and in noise, and speech-like stimuli (iterated rippled noise pitch contours) in adult male rats subjected to mild blast and sham exposure over the course of 2 mo. We found that blast animals demonstrated drastic threshold increases and auditory transmission deficits immediately after blast exposure, followed by substantial recovery during the window of 7-14 days postblast, although with some deficits remaining even after 2 mo. Challenging conditions and speech-like stimuli can better elucidate mild bTBI-induced auditory deficit during this period. Our results suggest multiphasic recovery and therefore potentially different time windows for treatment, and deficits can be best observed using a small battery of sound stimuli.NEW & NOTEWORTHY Few studies on blast-induced hearing deficits go beyond simple sounds and sparsely track postexposure. Therefore, the recovery arc for potential therapies and real-world listening is poorly understood. Evidence suggested multiple recovery phases over 2 mo postexposure. Hearing thresholds largely recovered within 14 days and partially explained recovery. However, midlatency responses, responses to amplitude modulation in noise, and speech-like pitch sweeps exhibited extended changes, implying persistent central auditory deficits and the importance of subclinical threshold shifts.

Head Injury Exposure in Veterans Presenting to Memory Disorders Clinic: An Observational Study of Clinical Characteristics and Relationship of Event-Related Potentials and Imaging Markers.

Objective: Traumatic brain injury (TBI) and repetitive head impacts (RHI) related to blasts or contact sports are commonly reported among military service members. However, the clinical implications of remote TBI and RHI in veterans remains a challenge when evaluating older veterans at risk of neurodegenerative conditions including Alzheimer's disease (AD) and Chronic Traumatic Encephalopathy (CTE). This study aimed to test the hypothesis that veterans in a memory disorders clinic with remote head injury would be more likely to have neurodegenerative clinical diagnoses, increased rates of amyloid PET positivity, higher prevalence of cavum septum pellucidi/vergae, and alterations in event-related potential (ERP) middle latency auditory evoked potentials (MLAEPs) and long latency ERP responses compared to those without head injuries.Methods: Older veterans aged 50–100 were recruited from a memory disorders clinic at VA Boston Healthcare system with a history of head injury (n = 72) and without head injury history (n = 52). Patients were classified as reporting prior head injury including TBI and/or RHI exposure based on self-report and chart review. Participants underwent MRI to determine presence/absence of cavum and an ERP auditory oddball protocol.Results: The head injury group was equally likely to have a positive amyloid PET compared to the non-head injury group. Additionally, the head injury group were less likely to have a diagnosis of a neurodegenerative condition than those without head injury. P200 target amplitude and MLAEP amplitudes for standard and target tones were decreased in the head injury group compared to the non-head injury group while P3b amplitude did not differ.Conclusions: Veterans with reported remote head injury evaluated in a memory disorders clinic were not more likely to have a neurodegenerative diagnosis or imaging markers of neurodegeneration than those without head injury. Decreased P200 target and MLAEP target and standard tone amplitudes in the head injury group may be relevant as potential diagnostic markers of remote head injury.

Using the Perfusion Index to predict changes in the depth of anesthesia in children compared with the A-line Autoregression Index: an observational study

BackgroundWe investigated the performance of the Perfusion Index (PI) derived from pulse oximetry waveform as a tool for assessment of anesthetic depth in comparison with A-line Autoregression Index (AAI) derived from analysis of Middle-Latency Auditory Evoked Potentials (MLAEP) waveform integrated by aepEXplus monitor in children receiving sevoflurane anesthesia for tonsillectomy. MethodsForty-one patients (4–12 years old) were included in this study. The PI and AAI were recorded simultaneously every minute during different stages of anesthesia delivery. The statistical tests included descriptive analysis, significance tests, correlation tests, and Receiver Operating Characteristic (ROC) curve. The AAI served as a reference. ResultsThe PI significantly decreased during light anesthesia and recovery, and significantly increased during deeper planes of anesthesia, with an inverse mirror-image relationship with the AAI. A negative correlation of low to moderate degree was detected between PI and AAI during the study (p > 0.05), that reached a statistical significance at the 5th minute during sevoflurane mask induction (r = −0.457, p = 0.008). ROC analysis at an AAI < 25 extracted the best cut-off value for PI before intubation as 1.48 (AUC = 0.698 [0.537–0.859], 94.4% sensitivity, 44.5% specificity) and at 10-minute intraoperatively as 2.4 (AUC = 0.537 [0.354–0.721], 91.7% sensitivity, 31% specificity). During recovery, at an AAI ≥ 50, the best cutoff was 1.82 (AUC = 0.661 [0.46–0.863], 100% sensitivity and 50% specificity) 2 minutes before spontaneous eye opening. ConclusionsCompared with the AAI, the PI can track changes in depth of anesthesia in pediatric patients undergoing tonsillectomy under sevoflurane anesthesia. Trial registrationClinical Trials. Gov. Identifier: NCT03412214.

The Use of Middle Latency Auditory Evoked Potentials (MLAEP) as Methodology for Evaluating Sedation Level in Propofol-Drug Induced Sleep Endoscopy (DISE) Procedure.

To analyze the middle latency auditory evoked potential index (MLAEPi), compared to the standard bispectral index (BIS), as a method for evaluating the sedation level in drug-induced sleep endoscopy (DISE). In this controlled clinical study on a sample of 99 obstructive sleep apnea (OSA) or snoring patients, we compared the MLAEPi with the BIS after propofol infusion during the standard DISE technique in order to define the MLAEPi values within the observational window of the procedure. The DISE procedure was divided into eight steps, and we collected both MLAEPi and BIS data values from the same patient in every step. The MLAEPi showed a faster response than the BIS after propofol infusion during DISE. Therefore, the clinical use of the MLAEPi in evaluating the sedation level seems to be a good alternative to the current technological standards.

A New Technological Advancement of the Drug-Induced Sleep Endoscopy (DISE) Procedure: The "All in One Glance" Strategy.

To illustrate a new technological advance in the standard drug-induced sleep endoscopy (DISE) model, a new machine was used, the Experimental 5 Video Stream System (5VsEs), which is capable of simultaneously visualizing all the decisional parameters on a single monitor, and recording and storing them in a single uneditable video. The DISE procedure was performed on 48 obstructive sleep apnea (OSA) or snoring patients. The parameters simultaneously recorded on a single monitor are (1) the pharmacokinetics and pharmacodynamics of propofol (through the target controlled infusion (TCI) pump monitor), (2) the endoscopic upper airway view, (3) the polygraphic pattern, and (4) the level of sedation (through the bispectral index (BIS) value). In parallel to the BIS recording, the middle latency auditory evoked potential (MLAEP) was also recorded and provided. Recorded videos from the 5VsEs machine were re-evaluated six months later by the same clinician and a second clinician to evaluate the concordance of the therapeutic indications between the two. After the six-month period, the same operator confirmed all their clinical decisions for 45 out of 48 videos. Three videos were no longer evaluable for technical reasons, so were excluded from further analysis. The comparison between the two operators showed a complete adherence in 98% of cases. The 5VsEs machine provides a multiparametric evaluation setting, defined as an “all in one glance” strategy, which allows a faster and more effective interpretation of all the simultaneous parameters during the DISE procedure, improving the diagnostic accuracy, and providing a more accurate post-analysis, as well as legal and research advantages.

Auditory Evoked Potentials P50: Pure-tones vs Clicks. There is a Similar Supression?

Objective: Clinical application of middle-latency auditory evoked potential (MLAEPs) has been increasing, highlighting the importance of understanding the nature of P50, a component of middle-latency auditory evoked potential. We manipulated stimulus frequency bands in auditory stimuli in order to investigate the nature of P50 in human auditory evoked potentials.&#x0D; Methods: Two paradigms have been used to obtain P50: one is a conditioning /testing paradigm in which paired of pure tone (1000Hz) are delivered, and the other was presented paired of clicks, both with an intensity of 60 dB sound pressure level above the auditory threshold. A total of 30 healthy volunteers were recruited for this study among Center of genetic engineering (fifteen man and fifteen women, mean age of 36, 5). All without consumption of caffeine, cigarettes and drugs.&#x0D; Results: No statistically significant differences occurred between the P50 amplitudes and latencies for the pure tone and those for the clicks.&#x0D; Conclusions: Our present results indicate that P50 in humans may reflect a feed-forward mechanism of the brain where a preceding stimulus drives sensory gating mechanisms in preparation for a second stimulus, but the contained frequency doesn't influence on the P50. Both types (tones or clicks) can be used in the exploration of patient with this evoked potential.

Does the duration of mobile phone usage affect the human auditory system? A middle latency auditory-evoked potential study in young adults

Background: Mobile phones emit microwave range of electromagnetic radiations. The human auditory cortex has a greater chance of being affected by these radiations due to the close proximity during usage. Middle latency auditory-evoked potential (MLAEP) recording helps in testing the integrity of the thalamo-cortical pathway of the human auditory system. Aims and Objectives: The aims and objectives are (1) to compare the latencies of MLAEPs in short- and long-term mobile phone users based on years of usage and (2) to compare the latencies of MLAEPs in mobile phone users grouped based on the duration of usage per day. Materials and Methods: MLAEP recording was done in 20 short- and long-term mobile users described as the history of usage of mobile phone less than and more than 1 year, respectively. Further, the group was categorized based on the duration of usage per day. Mean latencies of the MLAEP waves Na, Pa, and Nb were measured and compared statistically using Student’s t-test (two tailed, independent) and Mann–Whitney U test. Results: The mean latencies of MLAEP waveforms in both the ears were found to be significantly increased in long-term mobile phone users and in individuals who use mobile phones for more than 1 h per day. Conclusion: The study shows that long-term usage, as well as longer duration of usage of mobile phones, significantly affects the nerve conduction velocity in the thalamo-cortical region of the human auditory pathway.

Middle latency auditory evoked potential index for prediction of post-resuscitation survival in elderly populations with out-of-hospital cardiac arrest

Background. Out-of-hospital cardiac ar-rest (OHCA) is associated with a high mortality rate in the elderly. Although most reports have investigated among el-derly patients with OHCA until 1990s, non-invasive monitorings cannot pres-ently predicted cerebral resuscitation dur-ing cardiopulmonary resuscitation (CPR). Findings of a previous study suggest that monitoring of middle latency auditory evoked potentials (MLAEP) during CPR could provide an indicator of effective post-resuscitation survival.Objectives. We speculated that the MLAEP index (MLAEPi), measured in an emer-gency room, can predict post-resuscita-tion survival among elderly patients with OHCA. Methods. This prospective study included 31 elderly patients aged ≥65 years with OHCA who received basic life support (BLS) and did not achieve restoration of spontaneous circulation (ROSC) until ar-rival at the emergency center between December 2010 and December 2011. All patients were administered advanced car-diac life support (ACLS) in the emergency room. Initial MLAEPi was measured using an MLAEP monitor (aepEX plus®, Audi-omex, UK) during the first cycle of ACLS. Prediction of the post-resuscitation sur-vival was investigated. Results. Eight patients who achieved ROSC were admitted to our hospital and 23 did not achieve ROSC in the emergency room. Initial MLAEPi was significantly higher in patients with than without ROSC (median, 33 vs. 26, p = 0.02). Three survivors, among patients with ROSC, were discharged from our hospital (survivors) and 5 died dur-ing hospitalization (non-survivors). Initial MLAEPi was significantly higher in sur-vivors than in non-survivors (median, 35 vs. 28, p = 0.03) or patients without ROSC (median, 35 vs. 26, p < 0.01). Conclusions. MLAEPi satisfactorily de-notes cerebral function and predicts post-resuscitation survival in elderly popula-tions.

The early component of middle latency auditory-evoked potentials in the process of deviance detection.

The aim of the present study was to investigate both the encoding mechanism and the process of deviance detection when deviant stimuli were presented in various patterns in an environment featuring repetitive sounds. In adults with normal hearing, middle latency responses were recorded within an oddball paradigm containing complex tones or speech sounds, wherein deviant stimuli featured different change patterns. For both complex tones and speech sounds, the Na and Pa components of middle latency responses showed an increase in the mean amplitude and a reduction in latency when comparing rare deviant stimuli with repetitive standard stimuli in a stimulation block. However, deviant stimuli with a rising frequency induced signals with smaller amplitudes than other deviant stimuli. The present findings indicate that deviant stimuli with different change patterns induce differing responses in the primary auditory cortex. In addition, the Pa components of speech sounds typically feature a longer latency and similar mean amplitude compared with complex tones, which suggests that the auditory system requires more complex processing for the analysis of speech sounds before processing in the auditory cortex.

Assessment of aversion and unconsciousness during exposure to carbon dioxide at high concentration in lambs

AbstractThe most widely used stunning method in sheep is electrical. However, in lambs, this method leads to rupture of the blood vessels, provoking ecchymoses. In pigs (Sus scrofa), the use of CO2-stunning systems has increased in popularity due to positive effects on meat quality and animal welfare (movement of animals in groups). The aim here was to assess the effectiveness of a progressive exposure to 90% carbon dioxide (CO2) in inducing unconsciousness in lambs (Ovis aries) through changes in the middle latency auditory-evoked potentials (MLAEP) of the central nervous system (CNS), blood parameters (pH, carbon dioxide partial pressure (pCO2), oxygen partial pressure (pO2), oxygen saturation (SatO2) and bicarbonate (HCO3J, behaviour (head-shaking, sneezing, gasping and gagging) and physiological reflexes (corneal reflex, breathing and sensitivity to pain). Fourteen male lambs of the Ripollesa breed, weighing between 19 and 25 kg were progressively exposed to an atmosphere of 90% CO2 over 66 s. All blood parameters changed between 23 and 43 s after the onset of the immersion. The MLAEP did not decrease significantly until after 48 s exposure to CO2, suggesting an absence of auditory-evoked brain activity. Before that, lambs exhibited head-shaking and sneezing starting at 10.6 (± 0.77) s, and gasping starting at 20.6 (± 1.36) s. After exposure, all animals showed absence of breathing and sensibility to pain, and 36% of them absence of corneal reflex. The pH and pCO2 recovered basal values at 90 and 120 s, respectively, after the end of the exposure. The burst suppression index (BS%) and the A-Line ARX index (AAI) recovered basal levels at 116 and 159 s, respectively. Exposure to CO2 at high concentration induces effective stunning in sheep for a period of 124 s. However, during exposure, the animals exhibited signs of aversion and breathlessness.

Middle latency auditory-evoked potential index monitoring of cerebral function to predict functional outcome after emergency craniotomy in patients with brain damage.

BackgroundAt present, no satisfactory reports on the monitoring of cerebral function to predict functional outcomes after brain damage such as traumatic brain injury (TBI) and stroke. The middle latency auditory-evoked potential index (MLAEPi) monitor (aepEX plus®, Audiomex, UK) is a mobile MLAEP monitor measuring the degree of consciousness that is represented by numerical values. Hence, we hypothesized that MLAEPi predicts neurological outcome after emergency craniotomy among patients with disturbance of consciousness (DOC), which was caused by brain damage.MethodsThe afore-mentioned patients who underwent emergency craniotomy within 12 h of brain damage and were subsequently monitored using MLAEPi were enrolled in this study. DOC was defined as an initial Glasgow Coma Scale score < 8. MLAEPi was measured for 14 days after craniotomy. Neurological outcome was evaluated before discharge using a cerebral performance category (CPC) score and classified into three groups: favorable outcome group for a CPC score of 1 or 2, unfavorable outcome group for a score of 3 or 4, and brain dead (BD) group for a score of 5.ResultsThirty-two patients were included in this study (17 with TBIs and 15 with acute stroke). Regarding outcome, 10 patients had a favorable outcome, 15 had an unfavorable outcome, and 7 were pronounced BD. MLAEPi was observed to be significantly higher on day 5 than that observed immediately after craniotomy in cases of favorable or unfavorable outcome (63 ± 3.5 vs. 36 ± 2.5 in favorable outcome; 63 ± 3.5 vs. 34 ± 1.8 in unfavorable outcome). MLAEPi was significantly lower in BD patients than in those with a favorable or unfavorable outcome on day 3 (24 ± 4.2 in BD vs. 52 ± 5.2 and 45 ± 2.7 in favorable and unfavorable outcome, respectively) and after day 4. MLAEPi was significantly higher in patients with a favorable outcome than in those with a favorable or unfavorable outcome after day 6 (68 ± 2.3 in favorable outcome vs. 48 ± 2.3 in unfavorable outcome).ConclusionWe believe that MLAEPi satisfactorily denotes cerebral function and predicts outcomes after emergency craniotomy in patients with DOC, which was caused by acute brain damage.

English

BACKGROUND: Totally blind individuals are often considered to be compensated for their visual loss by augmentation in the auditory and tactile perceptions as compared to normal subjects. The objective of the present work was to study the Middle Latency Auditory Evoked Potential (MLAEP) component of the Auditory Evoked Potentials (AEP) in the totally blind and the normal subjects. METHODS: MLAEP was recorded in 20 totally blind females and compared with 20 age matched normal females. Latency and amplitude of the waveforms Na, Pa, Nb of MLAEP were measured and analyzed statistically using Student t test. RESULTS: The latencies of all the waveforms were significantly reduced in the blind individuals compared to normal subjects. The amplitudes of the waveforms Na, Pa, Nb did not show any significant changes between the two groups. CONCLUSION: The present study suggests that the totally blind individuals demonstrate remarkable neuroplastic changes and there is neuro physiological evidence of much better information processing in the auditory system in the totally blind compared to normal subjects.

Middle latency auditory-evoked potential index for predicting the degree of consciousness of comatose patients in EDs

IntroductionDigitized assessment of the degree of consciousness is a universal challenge in emergency departments (EDs) and intensive care units (ICUs). The middle latency auditory-evoked potential index (MLAEPi) monitor aepEX plus (Audiomex, Glasgow, Scotland, UK) is the first mobile middle latency auditory-evoked potential monitor. We speculated that the initial MLAEPi determined on arrival at EDs could indicate cerebral function and predict the degree of consciousness of comatose patients. MethodsWe used MLAEPi-related data from 50 comatose patients with disturbance of consciousness (DOC), 50 patients with cardiopulmonary arrest (CPA), and 50 healthy volunteers (control). Comatose patients were defined as those with an initial Glasgow Coma Scale score of 8 or less. The CPA group consisted of patients who arrived at EDs without restoration of spontaneous circulation. Among the patients with DOC who underwent sedation at EDs, the change in the MLAEPi was evaluated between arrival at the ED and ICU admission. ResultsThe initial MLAEPi was significantly lower in the DOC group than in the control group but significantly higher in the DOC group than in the CPA group. Among the comatose patients, the receiver operating characteristic curve for the initial MLAEPi showed an area under the curve of 0.93 (P < .01) for the DOC group. Thirty patients with DOC underwent sedation at EDs, and the initial MLAEPi was significantly higher than those at other periods during emergency care. ConclusionThe MLAEPi (simple numerical value) may be used to evaluate the degree of consciousness in comatose patients while performing emergency care in EDs.

Brainstem auditory evoked potentials and middle latency auditory evoked potentials in young children

Measurements of brainstem auditory evoked potentials (BAEP) and middle latency auditory evoked potentials (MLAEP) are readily available neurophysiologic assessments. The generators for BAEP are believed to involve the structures of cochlear nerve, cochlear nucleus, superior olive complex, dorsal and rostral pons, and lateral lemniscus. The generators for MLAEP are assumed to be located in the subcortical area and auditory cortex. BAEP are commonly used in evaluating children with autistic and hearing disorders. However, measurement of MLAEP is rarely performed in young children. To explore the feasibility of this procedure in young children, we retrospectively reviewed our neurophysiology databank and charts for a 3-year period to identify subjects who had both BAEP and MLAEP performed. Subjects with known or identifiable central nervous system abnormalities from the history, neurologic examination and neuroimaging studies were excluded. This cohort of 93 children up to 3years of age was divided into 10 groups based on the age at testing (upper limits of: 1week; 1, 2, 4, 6, 8, 10 and 12months; 2years; and 3years of age). Evolution of peak latency, interpeak latency and amplitude of waveforms in BAEP and MLAEP were demonstrated. We concluded that measurement of BAEP and MLAEP is feasible in children, as early as the first few months of life. The combination of both MLAEP and BAEP may increase the diagnostic sensitivity of neurophysiologic assessment of the integrity or functional status of both the peripheral (acoustic nerve) and the central (brainstem, subcortical and cortical) auditory conduction systems in young children with developmental speech and language disorders.

Transcranial near infrared laser irradiation to primary auditory cortex alters auditory neural activities

Event Abstract Back to Event Transcranial near infrared laser irradiation to primary auditory cortex alters auditory neural activities Naoya Akiyama1, Kohta I. Kobayasi2 and Hiroshi Riquimaroux1, 2* 1 Doshisha University, Department of Biomedical Engineerling and Biomedical Infomation, Graduate School of Life and Medical Science, Japan 2 Doshisha University, Biomedical Information, Japan The laser irradiation with a near-infrared wavelength (830nm) has been recently developed to reversibly inactivate neural activities. Irradiation of near-infrared laser (NIRL) has advantages over other methods for neural suppression (i.e., physical ablation or pharmacological method). The advantages of NIRL are as follows: 1) it may irradiate a small focal area, 2) its inactivation is reversible and 3) inactivation and recovery occurs immediately. Previous studies irradiated NIRL directly to the brain with craniotomy. The NIRL irradiation through the skull without craniotomy is much less invasive and well suited for behavioral studies. The purpose of this study was to evaluate the method of reversible inhibition of neural activity by transcranial irradiation. Five male gerbils (Meriones unguiculatus) were used as subjects. Animal was anesthetized by ketamine and xylazine. We made a hole near the parietal region and silver electorode, tip of which was loop-shaped, was placed on epidula over the primary auditory cortex. We recorded auditory evoked potential (AEP) to clicks and compared the difference in potential before, during and after NIRL irradiation. In addition, we presented light flash to record visual evoked potential (VEP) from the identical location for comparison with AEP. We alternately presented clicks and light flashes to record AEP and VEP. Delay between visual and auditory stimuli was 1 s. All stimulus duration was set at 100 µs. The recordings were made in a soundproof box. Light-emitting diode (LED), loud speaker and optical fiber for laser irradiation were installed in the soundproof box. The first 10 minutes was used for recordings without irradiation. The next 10 minutes was dedicated for recordings during laser irradiation. Then, we continued recordings for 50 minutes after stopping irradiation for examining the recovery process. With irradiation level of 70 mW/mm2 or lower, AEPs did not change during laser irradiation. However, with of irradiation level of 100 mW/mm2 or more, AEP (middle latency responses) was altered. The AEP recovered within 2 minutes after laser irradiation was terminated. On the other hand, the VEP was not altered, regardless of the laser irradiation on auditory cortex. Results indicate that the middle latency AEP (10-50 ms after the sound stimulus) originated in the primary auditory cortex, was possibly suppressed by transcranial NIRL irradiation to the primary auditory cortex. Successful alteration of the AEP by tranxcranial laser irradiation suggests possible application of this methods to free moving or awake behaving animals. Keywords: auditory evoked potential (AEP), visual evoked potential (VEP) Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for participant symposium and student poster award) Topic: Novel Tools and Methods Citation: Akiyama N, Kobayasi KI and Riquimaroux H (2012). Transcranial near infrared laser irradiation to primary auditory cortex alters auditory neural activities. Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00374 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 01 May 2012; Published Online: 07 Jul 2012. * Correspondence: Prof. Hiroshi Riquimaroux, Doshisha University, Department of Biomedical Engineerling and Biomedical Infomation, Graduate School of Life and Medical Science, Kyotanabe, Kyoto, 610-0321, Japan, hrikimar@mail.doshisha.ac.jp Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Naoya Akiyama Kohta I Kobayasi Hiroshi Riquimaroux Google Naoya Akiyama Kohta I Kobayasi Hiroshi Riquimaroux Google Scholar Naoya Akiyama Kohta I Kobayasi Hiroshi Riquimaroux PubMed Naoya Akiyama Kohta I Kobayasi Hiroshi Riquimaroux Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Abstract 221: Value of Initial Middle Latency Auditory Evoked Potential Index for Cardiopulmonary Arrest Resuscitation

Introduction: Non-invasive monitoring that can indicate cerebral resuscitation in cardiac arrest patients remains unknown. In an operative setting, middle latency auditory evoked potentials (MLAEP) provide a good discrimination of consciousness and cerebral function during anesthesia. Hypothesis: We seessed the hypothesis that initial MLAEP index (MLAEPi) can predict the return of spontaneous cardiac activity (ROSC) or survival on arrival at the emergency department (ED). Methods: This was a prospective study and included 50 patients with cardiac arrest who received BLS by prehospital paramedics. The patients were then administered ACLS by an emergency medical team member on arrival at ED. Initial MLAEPi was immediately measured using an aepEX monitor (1st version; Audiomex, Glasgow, UK) during the first cycle of ACLS in ED (Figure). Results: Seventeen (34%) patients who showed ROSC were admitted to our hospital (ROSC group); however, 33 patients did not show ROSC on resuscitation at the scene (non-ROSC group). Initial MLAEPi in the ROSC group was significantly higher than that in the non-ROSC groups (39±18 vs. 27±6, p&lt;0.01). In the ROSC group, clinically significant correlations were identified between initial MLAEPi and the time to the beginning of ACLS (r=-0.57, p=0.02); time to ROSC from the beginning of BLS (r=-0.53, p=0.03); and lactate concentrations (r=-0.50, p=0.04). Eight patients were discharged from our hospital (survivors) and 4 of them had no disability as per Cerebral Performance Category 1. Initial MLAEPi of survivors was significantly higher than that of non-survivors (49±23 vs. 28±6, p&lt;0.01). The ROC curve for initial MLAEPi demonstrated that area under the curve of 0.89 (95% CI=0.77-1.01, p&lt;0.01), and MLAEPi cutoff point ≤ 33 predicted no survival with a likelihood ratio of 6.10 (sensitivity=76.2; specificity=87.5). Conclusions: In conclusion, although our sample size is small, it showed that initial MLAEPi is represented by simple numerical values for the initial evaluation of ROSC and survival in cardiac arrest patients. Alternatively, MLAEPi may help emergency medical teams as a clinical predictor for termination of resuscitative efforts in a clinical setting.

Brainstem auditory-evoked potentials in two meditative mental states.

Context:Practicing mental repetition of “OM” has been shown to cause significant changes in the middle latency auditory-evoked potentials, which suggests that it facilitates the neural activity at the mesencephalic or diencephalic levels.Aims:The aim of the study was to study the brainstem auditory-evoked potentials (BAEP) in two meditation states based on consciousness, viz. dharana, and dhyana.Materials and Methods:Thirty subjects were selected, with ages ranging from 20 to 55 years (M=29.1; ±SD=6.5 years) who had a minimum of 6 months experience in meditating “OM”. Each subject was assessed in four sessions, i.e. two meditation and two control sessions. The two control sessions were: (i) ekagrata, i.e. single-topic lecture on meditation and (ii) cancalata, i.e. non-targeted thinking. The two meditation sessions were: (i) dharana, i.e. focusing on the symbol “OM” and (ii) dhyana, i.e. effortless single-thought state “OM”. All four sessions were recorded on four different days and consisted of three states, i.e. pre, during and post.Results:The present results showed that the wave V peak latency significantly increased in cancalata, ekagrata and dharana, but no change occurred during the dhyana session.Conclusions:These results suggested that information transmission along the auditory pathway is delayed during cancalata, ekagrata and dharana, but there is no change during dhyana. It may be said that auditory information transmission was delayed at the inferior collicular level as the wave V corresponds to the tectum.

The Auditory System Involvement in Parkinson Disease: Electrophysiological and Neuropsychological Correlations

In the course of Parkinson disease (PD), apart from motor symptoms, presence of mental disturbances such as dementia and depression is common. The aims of this study were to assess the auditory system involvement in patients with PD using electrophysiological and neuropsychological tests and to correlate the cognitive impairment and the auditory evoked potentials tests results. The auditory and cognitive functions were studied in 53 patients with idiopathic PD, mean age 65.8 +/- 9.1 years; mean disease duration 7.8 +/- 5.0 years; mean motor disability score 2.5 +/- 0.8 points in Hoehn-Yahr scale compared with a control group matched for age and sex. In patients and controls, cognitive functions were analyzed electrophysiologically using middle latency auditory evoked potentials (MLAEP) and long latency (event-related potentials, P300) auditory evoked potentials. Neuropsychological testing consisted of Wisconsin Card Sorting Test (WCST). According to WCST results, patients with PD were divided into 2 subgroups: patients with normal and abnormal WCST performance (WCST(-) and WCST(+) subgroups, respectively). Sixteen of 46 patients (34.8%) showed cognitive impairment when evaluated with WCST. Statistically significant differences in middle latency auditory evoked potentials and P300 results between WCST(-) and WCST(+) groups were found consisting of P300 abnormalities in 93.8% patients in WCST(+) and 57.7% in WCST(-) group. Middle latency auditory evoked potentials were abnormal in 71.4% and 63% patients in WCST(+) and WCST(-) group, respectively. P300 was absent significantly more often (P < 0.01) in the subgroup with cognitive impairment. The difference in middle latency auditory evoked potentials results between these subgroups was statistically insignificant. The auditory evoked potentials changes were more common among patients with abnormal WCST performance. According to our results, the auditory evoked potentials of different latencies are helpful in the assessment of cognitive changes accompanying PD.