Middle Latency Response Research Articles

Distinct Features of Auditory Steady-State Responses as Compared to Transient Event-Related Potentials

Transient event-related potentials (ERPs) and steady-state responses (SSRs) have been popularly employed to investigate the function of the human brain, but their relationship still remains a matter of debate. Some researchers believed that SSRs could be explained by the linear summation of successive transient ERPs (superposition hypothesis), while others believed that SSRs were the result of the entrainment of a neural rhythm driven by the periodic repetition of a sensory stimulus (oscillatory entrainment hypothesis). In the present study, taking auditory modality as an example, we aimed to clarify the distinct features of SSRs, evoked by the 40-Hz and 60-Hz periodic auditory stimulation, as compared to transient ERPs, evoked by a single click. We observed that (1) SSRs were mainly generated by phase synchronization, while late latency responses (LLRs) in transient ERPs were mainly generated by power enhancement; (2) scalp topographies of LLRs in transient ERPs were markedly different from those of SSRs; (3) the powers of both 40-Hz and 60-Hz SSRs were significantly correlated, while they were not significantly correlated with the N1 power in transient ERPs; (4) whereas SSRs were dominantly modulated by stimulus intensity, middle latency responses (MLRs) were not significantly modulated by both stimulus intensity and subjective loudness judgment, and LLRs were significantly modulated by subjective loudness judgment even within the same stimulus intensity. All these findings indicated that high-frequency SSRs were different from both MLRs and LLRs in transient ERPs, thus supporting the possibility of oscillatory entrainment hypothesis to the generation of SSRs. Therefore, SSRs could be used to explore distinct neural responses as compared to transient ERPs, and help us reveal novel and reliable neural mechanisms of the human brain.

Serial Auditory-Evoked Potentials in the Diagnosis and Monitoring of a Child with Landau-Kleffner Syndrome

A boy, aged 2 1/2 yr, experienced sudden deterioration of speech and language abilities. He saw multiple medical professionals across 2 yr. By almost 5 yr, his vocabulary diminished from 50 words to 4, and he was referred to our speech and hearing center. The purpose of this study was to heighten awareness of Landau-Kleffner syndrome (LKS) and emphasize the importance of an objective test battery that includes serial auditory-evoked potentials (AEPs) to audiologists who often are on the front lines of diagnosis and treatment delivery when faced with a child experiencing unexplained loss of the use of speech and language. Clinical report. Interview revealed a family history of seizure disorder. Normal social behaviors were observed. Acoustic reflexes and otoacoustic emissions were consistent with normal peripheral auditory function. The child could not complete behavioral audiometric testing or auditory processing tests, so serial AEPs were used to examine central nervous system function. Normal auditory brainstem responses, a replicable Na and absent Pa of the middle latency responses, and abnormal slow cortical potentials suggested dysfunction of auditory processing at the cortical level. The child was referred to a neurologist, who confirmed LKS. At age 7 1/2 yr, after 2 1/2 yr of antiepileptic medications, electroencephalographic (EEG) and audiometric measures normalized. Presently, the child communicates manually with limited use of oral information. Audiologists often are one of the first professionals to assess children with loss of speech and language of unknown origin. Objective, noninvasive, serial AEPs are a simple and valuable addition to the central audiometric test battery when evaluating a child with speech and language regression. The inclusion of these tests will markedly increase the chance for early and accurate referral, diagnosis, and monitoring of a child with LKS which is imperative for a positive prognosis.

Gain modulation of the middle latency cutaneous reflex in patients with chronic joint instability after ankle sprain

ObjectiveTo investigate the neural alteration of reflex pathways arising from cutaneous afferents in patients with chronic ankle instability. MethodsCutaneous reflexes were elicited by applying non-noxious electrical stimulation to the sural nerve of subjects with chronic ankle instability (n=17) and control subjects (n=17) while sitting. Electromyographic (EMG) signals were recorded from each ankle and thigh muscle. The middle latency response (MLR; latency: 70–120ms) component was analyzed. ResultsIn the peroneus longus (PL) and vastus lateralis (VL) muscles, linear regression analyses between the magnitude of the inhibitory MLR and background EMG activity showed that, compared to the uninjured side and the control subjects, the gain of the suppressive MLR was increased in the injured side. This was also confirmed by the pooled data for both groups. The degree of MLR alteration was significantly correlated to that of chronic ankle instability in the PL. ConclusionsThe excitability of middle latency cutaneous reflexes in the PL and VL is modulated in subjects with chronic ankle instability. SignificanceCutaneous reflexes may be potential tools to investigate the pathological state of the neural system that controls the lower limbs in subjects with chronic ankle instability.

Children With Phenylketonuria Treated Early

Individuals with phenylketonuria (PKU) can exhibit deficits in executive functions, intelligence, attention, visual-spatial processing abilities, and efficiency stemming presumably from deficient neurotransmitter synthesis, even when the disorder is diagnosed and treated early. Basic audiological and electrophysiological evaluations were used to examine the peripheral and central auditory pathways of children with early-treated PKU, who followed adequate versus inadequate diets. Results were compared with those of age-matched children without PKU. The control group included 35 children aged 5 to 16 years, and the experimental group included 25 children with classic PKU, all of whom were diagnosed and treated early. The experimental group comprised children of two subgroups, divided according to their dietary control, as follows: 8 children aged 6 to 13 years with adequate diets (group A); 17 children ages 6 to 15 years demonstrating inadequate diets (group B). All participants underwent auditory evaluations, including otoscopy, pure-tone and speech audiometry, immittance testing (tympanometry and assessment of contralateral stapedial reflex thresholds), and evaluations of auditory brainstem and middle latency responses. The demographic variables and audiological examination results were analyzed for all groups. Results among groups and subgroups were compared using analysis of variance with repeated measures to test statistical significance across factors and measures at the p = 0.05 level. Audiometric evaluation revealed results within normal limits for all groups, except for one child from the inadequate diet group, who showed a mild bilateral conductive hearing loss. Results of speech and immittance audiometry suggested the children in group B as having poorer average speech-discrimination scores and higher stapedial reflex thresholds at 4000 Hz. Auditory brainstem response results revealed longer average latencies for waves III and V and greater interaural differences for wave V in group B, although both groups A and B showed longer average latencies for the interpeak interval I-V, compared with the control group. Middle latency responses showed no significant differences in the latencies of the Na and Pa waves or the Na-Pa amplitude for the experimental group, but electrode or ear effects were present in 87.5% of group A and 58.8% of group B. Overall, differences observed tended to be small (by clinical diagnostic standards), yet suggest that children with PKU exhibit some effect of this disorder on the pontine auditory pathway, even when diagnosed/treated early and independent of the appropriateness of diet. It thus seems prudent to follow PKU children with auditory processing assessments to evaluate functional implications of these findings.

Prior experience does not alter modulation of cutaneous reflexes during manual wheeling and symmetrical arm cycling

Previous research has reported that training and experience influence H-reflex amplitude during rhythmic activity; however, little research has yet examined the influence of training on cutaneous reflexes. Manual wheelchair users (MWUs) depend on their arms for locomotion. We postulated that the daily dependence and high amount of use of the arms for mobility in MWUs would show differences in cutaneous reflex modulation during upper limb cyclic movements compared with able-bodied control subjects. We hypothesized that MWUs would demonstrate increased reflex response amplitudes for both manual wheeling and symmetrical arm cycling tasks. The superficial radial nerve was stimulated randomly at different points of the movement cycle of manual wheeling and symmetrical arm cycling in MWUs and able-bodied subjects naive to wheeling. Our results showed that there were no differences in amplitude modulation of early- or middle-latency cutaneous reflexes between the able-bodied group and the MWU group. However, there were several differences in amplitude modulation of cutaneous reflexes between tasks (manual wheeling and symmetrical arm cycling). Specifically, differences were observed in early-latency responses in the anterior and posterior deltoid muscles and biceps and triceps brachii as well as in middle-latency responses in the anterior and posterior deltoid. These data suggest that manual wheeling experience does not modify the pattern of cutaneous reflex amplitude modulation during manual wheeling. The differences in amplitude modulation of cutaneous reflexes between tasks may be a result of mechanical differences (i.e., hand contact) between tasks.

Relação entre potenciais evocados auditivos de média latência e distúrbio de processamento auditivo: estudo de casos

O Potencial Evocado Auditivo de Média Latência é um teste objetivo promissor na audiologia na pesquisa neuro-diagnóstica das disfunções do sistema auditivo. Tem como vantagens a precisão e objetividade na avaliação e por isso é útil em crianças. O presente estudo teve como objetivo analisar os potenciais evocados auditivos de média latência em dois pacientes com distúrbio de processamento auditivo e relacionar as medidas objetivas e comportamentais. Para tanto foi realizado estudo de caso de dois pacientes (P1= feminino, 12 anos; P2= masculino, 17 anos), ambos com ausência de alterações sensoriais, distúrbios neurológicos, neuropsiquiátricos. Ambos foram submetidos à anamnese, inspeção do meato acústico externo, avaliação audiológica e avaliação do exame de potencial evocado auditivo de média latência. Houve associação significante entre os resultados dos exames comportamentais e objetivos. Na anamnese, houve queixas referentes à dificuldade de escuta em ambiente ruidoso, localização sonora, desatenção, além de trocas fonológicas na escrita e na fala. Foram observadas alterações no processo de decodificação auditiva à direita em ambos os casos na avaliação comportamental do processamento auditivo e no exame de potencial evocado auditivo de média latência a resposta da via contralateral direita foi deficitária, confirmando as dificuldades dos pacientes estudados na atribuição de significado às informações acústicas em condição de competição sonora à direita nos dois casos. Para os casos estudados comprovou-se à associação entre os resultados, porém há necessidade de novos estudos com maior amostra para confirmação dos dados.

The Efficacy of Red Ginseng in Type 1 and Type 2 Diabetes in Animals

Diabetes mellitus (DM) is one of the most modern chronic metabolic diseases in the world. Moreover, DM is one of the major causes of modern neurological diseases. In the present study, the therapeutic actions of Korean red ginseng were evaluated in type 1 and type 2 diabetic mouse models using auditory electrophysiological measurement. The comprehensive results from auditory brainstem response (ABR), auditory middle latency response (AMLR), and transient evoked otoacoustic emission (TEOAE) demonstrate auditory functional damage caused by type 1 or 2 DM. Korean red ginseng improved the hearing threshold shift, delayed latencies and signal intensity decrease in type 2 diabetic mice. Type 1 diabetic mice showed a partial improvement in decreasing amplitude and signal intensity, not significantly. We suggest that the Korean red ginseng has a more potent efficacy in hearing loss in insulin resistance type 2 diabetes than in type 1 diabetes.

Two Sequential Processes of Change Detection in Hierarchically Ordered Areas of the Human Auditory Cortex

Auditory deviance detection occurs around 150 ms after the onset of a deviant sound. Recent studies in animals and humans have described change-related processes occurring during the first 50 ms after sound onset. However, it still remains an open question whether these early and late processes of deviance detection are organized hierarchically in the human auditory cortex. We applied a beamforming source reconstruction approach in order to estimate brain sources associated with 2 temporally distinct markers of deviance detection. Results showed that rare frequency changes elicit an enhancement of the Nbm component of the middle latency response (MLR) peaking at 43 ms, in addition to the magnetic mismatch negativity (MMNm) peaking at 115 ms. Sources of MMNm, located in the right superior temporal gyrus, were lateral and posterior to the deviance-related MLR activity being generated in the right primary auditory cortex. Source reconstruction analyses revealed that detection of changes in the acoustic environment is a process accomplished in 2 different time ranges, by spatially separated auditory regions. Paralleling animal studies, our findings suggest that primary and secondary areas are involved in successive stages of deviance detection and support the existence of a hierarchical network devoted to auditory change detection.

From otoacoustic emission to late auditory potentials P300: the inhibitory effect.

This study verifies the effects of contralateral noise on otoacoustic emissions and auditory evoked potentials. Short, middle and late auditory evoked potentials as well as otoacoustic emissions with and without white noise were assessed. Twenty-five subjects, normal-hearing, both genders, aged 18 to 30 years, were tested . In general, latencies of the various auditory potentials were increased at noise conditions, whereas amplitudes were diminished at noise conditions for short, middle and late latency responses combined in the same subject. The amplitude of otoacoustic emission decreased significantly in the condition with contralateral noise in comparison to the condition without noise. Our results indicate that most subjects presented different responses between conditions (with and without noise) in all tests, thereby suggesting that the efferent system was acting at both caudal and rostral portions of the auditory system.

Auditory middle latency responses (A-MLR) in patients with dementia: A relationship between A-MLR and temporal lobe atrophy

Auditory middle latency responses (A-MLR) in patients with dementia: A relationship between A-MLR and temporal lobe atrophy

Detection of Simple and Pattern Regularity Violations Occurs at Different Levels of the Auditory Hierarchy

Auditory deviance detection in humans is indexed by the mismatch negativity (MMN), a component of the auditory evoked potential (AEP) of the electroencephalogram (EEG) occurring at a latency of 100–250 ms after stimulus onset. However, by using classic oddball paradigms, differential responses to regularity violations of simple auditory features have been found at the level of the middle latency response (MLR) of the AEP occurring within the first 50 ms after stimulus (deviation) onset. These findings suggest the existence of fast deviance detection mechanisms for simple feature changes, but it is not clear whether deviance detection among more complex acoustic regularities could be observed at such early latencies. To test this, we examined the pre-attentive processing of rare stimulus repetitions in a sequence of tones alternating in frequency in both long and middle latency ranges. Additionally, we introduced occasional changes in the interaural time difference (ITD), so that a simple-feature regularity could be examined in the same paradigm. MMN was obtained for both repetition and ITD deviants, occurring at 150 ms and 100 ms after stimulus onset respectively. At the level of the MLR, a difference was observed between standards and ITD deviants at the Na component (20–30 ms after stimulus onset), for 800 Hz tones, but not for repetition deviants. These findings suggest that detection mechanisms for deviants to simple regularities, but not to more complex regularities, are already activated in the MLR range, supporting the view that the auditory deviance detection system is organized in a hierarchical manner.

Early processing of pitch in the human auditory system

Middle-latency auditory evoked potentials, indicating early cortical processing, elicited by pitch changes and repetitions in pure tones and by complex tones with a missing-fundamental pitch were recorded in healthy adults ignoring the sounds while watching a silenced movie. Both for the pure and for the missing-fundamental tones, the Nb middle-latency response was larger for pitch changes (tones preceded by tones of different pitch) than for pitch repetitions (tones preceded by tones of the same pitch). This Nb enhancement was observed even for missing-fundamental tones preceded by repeated tones that had a different missing-fundamental pitch but included all harmonics of the subsequent tone with another missing-fundamental pitch. This finding rules out the possibility that the Nb enhancement in response to a change in missing-fundamental pitch was simply attributable to the activity of auditory cortex neurons responding specifically to the harmonics of missing-fundamental tones. The Nb effect presumably indicates pitch processing at or near the primary auditory cortex, and it was followed by a change-related enhancement of the N1 response, presumably generated in the secondary auditory cortex. This N1 enhancement might have been caused by a mismatch negativity response overlapping with the N1 response. Processing of missing-fundamental pitch was also reflected by the distribution of Nb responses. Tones with a higher missing-fundamental pitch elicited more frontally dominant Nb responses than tones with a lower missing-fundamental pitch. This effect of pitch, not seen for the pure tones, might indicate that the exact location of the Nb generator source in the auditory cortex depends on the missing-fundamental pitch of the eliciting tone.

Auditory middle latency response in children with learning difficulties.

Summary Introduction: This is an objective laboratory assessment of the central auditory systems of children with learning disabilities. Aim: To examine and determine the properties of the components of the Auditory Middle Latency Response in a sample of children with learning disabilities. Methods: This was a prospective, cross-sectional cohort study with quantitative, descriptive, and exploratory outcomes. We included 50 children aged 8–13 years of both genders with and without learning disorders. Those with disorders of known organic, environmental, or genetic causes were excluded. Results and Conclusions: The Na, Pa, and Nb waves were identified in all subjects. The ranges of the latency component values were as follows: Na = 9.8–32.3 ms, Pa = 19.0–51.4 ms, Nb = 30.0–64.3 ms (learning disorders group) and Na = 13.2–29.6 ms, Pa = 21.8–42.8 ms, Nb = 28.4–65.8 ms (healthy group). The values of the Na-Pa amplitude ranged from 0.3 to 6.8 ìV (learning disorders group) or 0.2–3.6 ìV (learning disorders group). Upon analysis, the functional characteristics of the groups were distinct: the left hemisphere Nb latency was longer in the study group than in the control group. Peculiarities of the electrophysiological measures were observed in the children with learning disorders. This study has provided information on the Auditory Middle Latency Response and can serve as a reference for other clinical and experimental studies in children with these disorders.

Frequency Dependence of Binaural Interaction in the Auditory Brainstem and Middle Latency Responses

The primary purpose of this investigation was to determine the relative frequency representation of binaural function in the brainstem and cortex of adults. The secondary purpose was to compare adult responses to previously reported infant responses. Simultaneous auditory brainstem responses and auditory middle responses were recorded monaurally and binaurally in 20 young women. The binaural (BIN) response was subtracted from the summed monaural waves (L+R) to obtain the binaural interaction components (BIC) from waves V (peak A) and Pa (BIC-Pa). Amplitude ratios were calculated as BIC/L+R. Repeated-measures analyses of variance evaluated responses to frequency (500 Hz vs. 4000 Hz), wave condition (L+R vs. BIN), and wave class (auditory brainstem response vs. auditory middle response). Waveforms were present for all conditions. The L+R responses were larger than the BIN responses, 500 Hz produced larger amplitudes than 4000 Hz, and Pa was larger than wave V. The largest response, overall, was the Pa(L+R) response to 500 Hz. For amplitude ratios, BIC-Pa/Pa(L+R) was larger than Peak A/[V(L+R)]. More neural resources are devoted to binaural function in the cortex than in the brainstem, and more resources are devoted to lower frequencies than to higher frequencies. The adult data confirm that previously recorded infant data reveal binaural immaturity. Longitudinal data should characterize developmental characteristics of binaural function.

Ear and electrode effects reduce within-group variability in middle latency response amplitude measures

Objectives: To establish normative amplitude values for relative difference measurements of the middle latency response (MLR) in normal-hearing pediatrics and to determine if these measurements provided a significant reduction of within-group variability when compared to raw, absolute amplitude measures. A relative amplitude difference is defined in the present paper as the difference in Na-Pa amplitude between two electrodes (e.g. |Na-Pa at C3 minus Na-Pa at C4|, or electrode effects) or between two ears (e.g. |Na-Pa on left ear stimulation minus Na-Pa on right ear stimulation|, or ear effects). In contrast, an absolute amplitude is defined as a single Na-Pa measurement made at one electrode for stimulation of one ear (e.g. Na-Pa measured at C3 on left ear stimulation). Design: Cross-sectional study. Study sample: 155 pediatrics with normal peripheral and central hearing, and no history of psychological, neurological, or learning disability issues. Results: Within-group variability was significantly smaller for relative differences when compared to absolute amplitude measures. Electrode effects showed significantly less variability than ear effects. Normative values for ear and electrode effects were reported. Conclusions: Relative differences may provide better utility in the clinical diagnosis of central auditory pathology in pediatrics when compared to absolute amplitude measures because these difference measures show significantly lower variability when examined across subjects.

Measurement of electrical evoked middle latency response in cochlear implantation operation

To establish the method of conducting electrical evoked middle latency response (EMLR) monitoring in cochlear implantation operation and further to assess the neural response of auditory pathway under electrical stimulation. Twenty cases of cochlear implantation subjects were investigated in this study. Fourteen cases were pre-lingual deaf and 6 were post-lingual deaf. The surface recording electrodes were placed on the patients under general anesthesia, with language processor connected to the triggering port of the auditory evoked potential device. After the electrode was implanted, the electrode No.3 was selected to conduct. The electrically evoked auditory nerve compound active potentials (ECAP) were firstly tested in all patients, thereafter the EABR mode was selected, and the stimulation parameters were changed to EMLR mode with monopole biphasic, alternation stimulation, pulse width from 50 to 100 µs, the stimulation intensity decreased or increased from 20 CL above the strength of the ECAP threshold to the reaction threshold with a step of 5CL. To evaluate the correlation between the ECAP thresholds and EMLR, another 6 cases of normal hearing healthy subjects were recruited to record their short-sound evoked auditory middle-latency response (AMLR), as the control of morphology and latency of MLR by electrical stimulation. The typical AMLR waveforms could be recorded by the composition of five waves in the 6 cases of normal hearing healthy subjects, with an average response threshold of (12.5±8.6) dBnHL, close to the behavioral audiometric threshold (10.8±7.3) dBHL. The EMLR waveforms could be recorded in 20 patients, which was similar to the AMLR waveforms. However, the wave latency and wave interval shortened. There were lower volatility and longer latency in pre-lingual deaf than post-lingual deaf. The EMLR threshold (140.55±9.92) CL was significantly lower than the ECAP threshold (160.75±13.34) CL (t=10.467, P<0.01), a positive correlation between the thresholds was detected (r=0.763, P<0.01). We successfully established the method of EMLR monitoring in cochlear implantation surgery. The EMLR threshold is lower than the ECAP threshold but it is close to the behavioral audiometric threshold; EMLR can provide neural response information closer to the auditory center, and can serve as an effective objective method to evaluate the effect of hearing rehabilitation.

Auditory middle latency responses in children with specific language impairment

Auditory-evoked potentials represent the response of the auditory pathway to an auditory stimulus. Specific language impairment (SLI) children have delayed language development with difficulties in both understanding and producing spoken language. Hence, the purpose of this study was to determine whether a group of children with SLI had abnormal changes in the auditory middle latency response (AMLR). AMLR was obtained for 19 SLI children and they were studied and compared to normal. Audiological assessment and speech language tests were done for the study group. The results revealed no significant statistical differences between SLI children and the normal with regard to AMLR (P > 0.05). Our results suggest that children with SLI do not have abnormal auditory system response at the level measured by AMLR casting doubt on affection of the hypnotized origin of AMLR, mainly primary auditory cortex, as a cause for delayed language development in those children.

Methods to Eliminate Stimulus Transduction Artifact From Insert Earphones During Electroencephalography

To reduce stimulus transduction artifacts in EEG while using insert earphones. Reference Equivalent Threshold SPLs were assessed for Etymotic ER-4B earphones in 15 volunteers. Auditory brainstem responses (ABRs) and middle latency responses (MLRs)-as well as long-duration complex ABRs-to click and /dα/ speech stimuli were recorded in a single-case design. Transduction artifacts occurred in raw EEG responses, but they were eliminated by shielding, counter-phasing (averaging across stimuli 180° out of phase), or rereferencing. Clinical grade ABRs, MLRs, and cABRs can be recorded with a standard digital EEG system and high-fidelity insert earphones, provided one or more techniques are used to remove the stimulus transduction artifact.

The Importance of Right Otitis Media in Childhood Language Disorders

Studies relating chronic otitis media and language disorders in children have not reported consistent findings. We carried out the first selective study aimed at discerning the role of chronic right otitis media in children less than 3 years of age in language development. A total of 35 children were studied using a full linguistic protocol, auditory brainstem responses, and middle latency responses. Twelve children had a history of chronic exclusive right otitis media. Seventeen age-matched children were selected as controls. Also, three children having a history of chronic left otitis media were compared with three age-matched controls. Linguistic tests showed significant differences between patients and controls in phonetic, phonological, and syntax scores but not semantics. Correlation studies between linguistic scores and auditory evoked responses in the whole cohort showed a significant coefficient in phonetic and phonological domains. These results emphasize the causative effect of right ear chronic otitis media and indicate that it mainly impairs phonetic and phonological coding of sounds, which may have implications for prophylactic treatment of at-risk children.

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.