Cortical evoked potentials to an auditory illusion: Binaural beats

ObjectiveTo define brain activity corresponding to an auditory illusion of 3 and 6 Hz binaural beats in 250 Hz or 1000 Hz base frequencies, and compare it to the sound onset response.MethodsEvent-Related Potentials (ERPs) were recorded in response to unmodulated tones of 250 or 1000 Hz to one ear and 3 or 6 Hz higher to the other, creating an illusion of amplitude modulations (beats) of 3 Hz and 6 Hz, in base frequencies of 250 Hz and 1000 Hz. Tones were 2000 ms in duration and presented with approximately 1 s intervals. Latency, amplitude and source current density estimates of ERP components to tone onset and subsequent beats-evoked oscillations were determined and compared across beat frequencies with both base frequencies.ResultsAll stimuli evoked tone-onset P₅₀, N₁₀₀ and P₂₀₀ components followed by oscillations corresponding to the beat frequency, and a subsequent tone-offset complex. Beats-evoked oscillations were higher in amplitude with the low base frequency and to the low beat frequency. Sources of the beats-evoked oscillations across all stimulus conditions located mostly to left lateral and inferior temporal lobe areas in all stimulus conditions. Onset-evoked components were not different across stimulus conditions; P₅₀ had significantly different sources than the beats-evoked oscillations; and N₁₀₀ and P₂₀₀ sources located to the same temporal lobe regions as beats-evoked oscillations, but were bilateral and also included frontal and parietal contributions.ConclusionsNeural activity with slightly different volley frequencies from left and right ear converges and interacts in the central auditory brainstem pathways to generate beats of neural activity to modulate activities in the left temporal lobe, giving rise to the illusion of binaural beats. Cortical potentials recorded to binaural beats are distinct from onset responses.SignificanceBrain activity corresponding to an auditory illusion of low frequency beats can be recorded from the scalp.     

Binaural interaction in the brain-stem auditory evoked potential: evidence for a delay line coincidence detection mechanism.

The binaural interaction component (BIC) of the brain-stem auditory evoked potential (BAEP) was studied in 13 normally hearing adults by subtracting the response to binaural clicks from the algebraic sum of monaural responses. Eight or 16 electrodes on the head and neck were referred to a non-cephalic site, the binaural stimuli were delivered either simultaneously or with an inter-aural time difference (delta t) of 0.2-1.6 msec, and masking noise was presented to the non-stimulated ear. With simultaneous binaural clicks a BIC was identifiable in every subject, the most consistent peaks being a scalp-positive potential (P1) peaking approximately 0.2 msec after wave V and a scalp negativity (N1) 0.7 msec later. Similar potentials were identifiable in 6/7 subjects with delta t of 0.4 msec, 5/7 at 0.8 msec but only 1/7 at 1.2 msec. This suggests that the BIC may be associated with sound localization mechanisms which are sensitive to a similar range of delta t. On increasing delta t from 0.0 to 0.8 msec, the BIC was progressively delayed by approximately half the inter-aural time difference, with no suggestion of increasing temporal dispersion. This supports the notion of a 'delay line coincidence detection' mechanism in which the BIC represents the output of binaurally responsive neurones, probably in the superior olivary complex, which are 'tuned' to a particular delta t by the relative lengths of presynaptic axons relaying input from either ear. The distribution of the BIC in sagittal and coronal electrode chains was compared with that of binaural BAEP components I-VI and found to bear the closest resemblance to wave IV. It is suggested that both components may originate largely in the lateral lemnisci.     

The nature of auditory discrimination problems in children with specific language impairment: an MMN study

Many children with specific language impairment (SLI) show impairments in discriminating auditorily presented stimuli. The present study investigates whether these discrimination problems are speech specific or of a general auditory nature. This was studied using a linguistic and nonlinguistic contrast that were matched for acoustic complexity in an active behavioral task and a passive ERP paradigm, known to elicit the mismatch negativity (MMN). In addition, attention skills and a variety of language skills were measured. Participants were 25 five-year-old Dutch children with SLI having receptive as well as productive language problems and 25 control children with typical speech- and language development. At the behavioral level, the SLI group was impaired in discriminating the linguistic contrast as compared to the control group, while both groups were unable to distinguish the non-linguistic contrast. Moreover, the SLI group tended to have impaired attention skills which correlated with performance on most of the language tests. At the neural level, the SLI group, in contrast to the control group, did not show an MMN in response to either the linguistic or nonlinguistic contrast. The MMN data are consistent with an account that relates the symptoms in children with SLI to non-speech processing difficulties.     

Binaural interaction of the auditory brain-stem potentials and middle latency auditory evoked potentials in infants and adults

Binaural interactions in brain-stem auditory evoked potentials and in middle latency auditory evoked potentials were studied in 18 normal hearing adults and 10 normal term infants. Binaural interactions at the times of ABR waves V and VI were comparable in term infants and adults. Binaural interaction during the time domain of the middle latency auditory evoked potentials was the greatest at N20 in term infants and at N40 in adults. Measurement of binaural interaction during maturation may be a useful tool in assessing neurologically affected infants.     

Memory impairment and auditory evoked potential gating deficit in schizophrenia

Impaired sensory gating and memory function were reported in a study of 10 schizophrenic patients and 10 age- and sex-matched normal subjects. The P50 component of the auditory evoked potential was used as an index of gating. Explicit memory was tested with the Wechsler Memory Scale and implicit memory by artificial grammar learning. The schizophrenic patients showed deficits in both verbal paired associate and visual reproduction tasks. They demonstrated impaired implicit learning in color patterns but not letter strings. They also showed impaired P50 sensory gating. Three-dimensional brain mapping revealed a differential distribution of brain potentials in the processing of S1 and S2 at either P50 or N100 in both groups. However, the group difference was not statistically confirmed. In the controls, both implicit letter-string learning and explicit verbal paired associates were positively correlated with N100 gating, suggesting an association of the early attentive component with lexicons. In the schizophrenic patients, color-pattern implicit learning was positively correlated with P50 gating. The modality-specific impairment of implicit learning in schizophrenia may reflect a failure of adaptive filtering on the flooding input from color patterns.     

Binaural interaction in auditory brain-stem responses: effects of masking

Binaural interaction (BI) in auditory brain-stem responses (ABRs) can be shown by comparing a binaurally elicited ABR to the algebraic sum of monaurally elicited ABRs. Subtracting the summed monaural ABR from binaural ABR yields a wave form assumed to contain response components attributable to BI. It has been suggested that acoustic crosstalk accounts for some of the 'BI' seen with this technique and that contralateral masking should be used during monaural stimulation to eliminate crosstalk. However, this practice might in itself confound the results, even if the masking noise were not intense enough to affect the opposite ear, by 'central masking' of brain-stem neural activity. We studied the effects of contralateral wide-band masking on BI/ABR in 10 normal adult subjects. Clicks were presented at levels from 55 to 115 dB peSPL, at 10 dB intervals. Masking was presented at 73 dB SPL (47 dB effective masking level); based on pilot studies of interaural attenuation, this was a level expected to be at, or just below, the threshold of audibility in the contralateral ear. BI/ABR wave forms were not noticeably affected by the addition of contralateral noise in the monaural trials. In addition, BI/ABR was seen (as previously reported) at levels well below any possibility of crossover artifact. Thus, BI/ABR is not simply attributable to crossover. Contralateral masking is not necessary in recording BI/ABR, within the limits of the stimuli and transducers used in this study.     

Binaural vs. monaural auditory evoked potentials in rat neocortex

High spatial resolution epicortical recording techniques and numerical modeling were used to investigate laterality effects on the middle latency auditory evoked potential (MAEP) complex. Our data confirm previous reports that auditory stimulus laterality has a consistent effect on the amplitude, timing, and spatial distribution of the MAEP complex. The earliest temporal components (P1a, P1b and N1) show the greatest sensitivity, and are absent during ipsilateral stimulation. The later positive slow wave (P2) is present at the same amplitude during all stimulation conditions. Generation of the P2 appears to be independent of prior activation of areas 36 and 41 reflected in the early components, suggesting its generation by a more diffuse thalamocortical pathway, possibly from the medial division of the medial geniculate. Serial vs. parallel activation of rodent auditory cortex is discussed in the context of laterality-sensitive MAEP components.     

Individual differences in auditory processing in specific language impairment: a follow-up study using event-related potentials and behavioural thresholds

It has frequently been claimed that children with specific language impairment (SLI) have impaired auditory perception, but there is much controversy about the role of such deficits in causing their language problems, and it has been difficult to establish solid, replicable findings in this area. Discrepancies in this field may arise because (a) a focus on mean results obscures the heterogeneity in the population and (b) insufficient attention has been paid to maturational aspects of auditory processing. We conducted a study of 16 young people with specific language impairment (SLI) and 16 control participants, 24 of whom had had auditory event-related potentials (ERPs) and frequency discrimination thresholds assessed 18 months previously. When originally assessed, around one third of the listeners with SLI had poor behavioural frequency discrimination thresholds, and these tended to be the younger participants. However, most of the SLI group had age-inappropriate late components of the auditory ERP, regardless of their frequency discrimination. At follow-up, the behavioural thresholds of those with poor frequency discrimination improved, though some remained outside the control range. At follow-up, ERPs for many of the individuals in the SLI group were still not age-appropriate. In several cases, waveforms of individuals in the SLI group resembled those of younger typically-developing children, though in other cases the waveform was unlike that of control cases at any age. Electrophysiological methods may reveal underlying immaturity or other abnormality of auditory processing even when behavioural thresholds look normal. This study emphasises the variability seen in SLI, and the importance of studying individual cases rather than focusing on group means.     

Pattern-reversal auditory evoked potential

The late auditory evoked potential (AEP) was studied in response to an alternatingly frequency-modulated complex tone. This 'pattern-reversal' AEP was found to be a heartier response than the more conventional tone-burst evoked potential, albeit longer in latency.     

Influence of stimulation parameters on auditory stimulus processing in schizophrenia and major depression: an auditory evoked potential study

The influence of stimulation frequency and stimulus intensity on the auditory evoked potential components N1 and P2 was investigated in schizophrenic and major depressive patients. The findings in the patients were compared with those in normal controls. At a high stimulation frequency the amplitude of N1 was enhanced in both schizophrenic and major depressive patients; the latency of N1 increased only in the schizophrenic patients. These changes may be related to impairments of auditory input control and processing in these diseases. In the schizophrenic patients, P2 latency was prolonged under treatment with high-potency neuroleptic drugs.     

Children with specific language impairment: The effect of argument-structure complexity on auditory sentence comprehension

Children with specific language impairment (SLI) demonstrate consistent comprehension problems. The present study investigated whether these problems are driven primarily by structural complexity or length. A picture-sentence matching task was presented to 30 children: (1) 10 children with SLI, (2) 10 comprehension-matched children with typical language development (TLD) and (3) 10 children with TLD matched for chronological age. Argument-structure complexity was manipulated independently of length, which was also independently varied. Results showed that argument-structure complexity had a greater influence on comprehension in children with SLI than in the comparison groups, with transitive sentences eliciting more errors than intransitive ones. This effect was not dependent on sentence length, which did not appear to affect the comprehension level. The results support the view that comprehension problems in children with SLI are principally related to the structural complexity of the sentence rather than the amount of material to be processed.     

Brainstem auditory evoked potential study in children with autistic disorder

Brainstem auditory evoked potentials were compared in 109 children with infantile autism, 38 with autistic condition, 19 with mental retardation, and 20 normal children. Children with infantile autism or autistic condition had significantly longer brainstem transmission time than normal (p<.001). Autistic features, rather than age, sex, or lower mentality, correlated with brainstem transmission time (p<.0001). The autistic characteristics may be related to dysfunction of the brainstem which affects the processing of the sensory input through the auditory pathway. The brainstem lesion may be part of a generalized process of neurological damage that accounts for the deviant language, cognitive, and social development in the spectrum of autistic disorder.We thank R. Ko and F. Pun for their scretarial assistance.     

Neurobiology of specific language impairment

This review summarizes what is known about the neurobiology of specific language impairment. Despite its name, specific language impairment is frequently not specific. It is common to find associated impairments in motor skills, cognitive function, attention, and reading in children who meet criteria for specific language impairment. There is evidence that limitation in phonologic working memory may be a core deficit in specific language impairment. Both genetic and environmental factors have been shown to be important etiologic factors in specific language impairment. Structural neuroimaging studies suggest that atypical patterns of asymmetry of language cortex, white-matter abnormalities, and cortical dysplasia may be associated with specific language impairment. Abnormalities in the later stages of auditory processing have been demonstrated using auditory event-related potentials. Functional neuroimaging may cast further light on the neurobiology of specific language impairment and serve as a means of developing and evaluating therapy. A better understanding of the neurobiology of specific language impairment is critical for the rational development of therapeutic strategies to treat this common disorder.     

Binaural voltage summation of brainstem auditory evoked potentials: an adjunct to the diagnostic criteria for multiple sclerosis

Brainstem auditory evoked potential (BAEP) amplitude is modified according to whether or not the stimulus is applied monaurally or binaurally. In normal subjects, wave V amplitude increases by an average of 68.7% upon changing stimulation from monaural to binaural. From earlier studies there is evidence that brainstem potential amplitude is reduced in patients with multiple sclerosis (MS) but none to suggest that binaural stimulation results in increased amplitude. This study evaluated the extent of binaural summation of BAEPs in patients with MS. In a large majority of patients with MS who have no hearing deficit, BAEPs showed no increase in wave V amplitude on binaural stimulation. This finding is in contrast to the normal group and thus has diagnostic importance. Measurements of binaural summation therefore might usefully be applied to the clinical assessment of disease progression, or lack of it, in individual patients.     

A review of generators of the brainstem auditory evoked potential: contribution of an experimental study

The goal of this paper is to briefly review the evidence for the generator(s) of each wave of the brainstem auditory evoked potential. An experimental study is included that adds data relevant to the question of generators. Thus, the distributions of amplitude and latency are plotted throughout the scalp for each of the positive and negative waves (16) of this potential (20 normal ears). For amplitudes, seven are maximal on the midline with five on Cz (IN, IV, V, VN, and VIN) and two on FZ (I' and IIIN); two are on the ipsilateral side (II and VIIN), and seven are maximal on the contralateral side (I, IIN, III, VI, VII, VIII, and VIIIN). For latency to peak, none is earliest on the midline; only five are on the ipsilateral side (I', III, IIIN, IV, and VIIN), and all the rest are on the contralateral side. The falloff from the maximal amplitude is rectilinearly related to the square of the distance from the peak, but this relationship is not the "inverse square law." These data are then discussed with reference to the possible generators of each wave.     

Genetic effects in the cortical auditory evoked potential: a twin study.

An experiment was carried out on 40 pairs of adult male twins to investigate the extent of genetical determination in the cortical auditory evoked potential. Tonal stimuli of 1 sec duration, at an intensity of 95 dB and a frequency of 100 c/sec, were used. The inter-stimulus interval was 33 sec and the bipolar evoked potential was measured between the CZ and T3 scalp positions. The reliability of the seven latency and amplitude measures was also calculated and this was taken into account in the subsequent genetic analysis. The biometrical gentical approach, which gives maximal information particularly on small samples, was used to analyse the data. A strong genetic influence was found on all the amplitude scores. The environment made no significant contribution to these. For the latencies there was some evidence for a genetic effect; however, this was not very strong and can well be interpreted as being due to between family environmental effects.     

Binaural interaction in auditory brainstem responses of mentally retarded and nonretarded individuals

The short-latency auditory brainstem responses of institutionalized mentally retarded individuals (Down syndrome and unknown etiology) and nonretarded control persons were recorded. The results showed that retarded individuals differed in the clarity of initial auditory brainstem response waves (I and II). Down syndrome individuals had significantly smaller auditory brainstem response amplitudes (Waves II and III) when compared with retarded individuals of unknown etiology. Down syndrome individuals also had significantly shorter latencies (Waves III and V) and shorter interwave conduction times (III-I and V-I) when compared with retarded individuals of unknown etiology. Retarded individuals did not differ from control subjects when amplitudes of binaural auditory brainstem responses were compared to the computer summation of such responses evoked by left and right ear stimulation; however, there was evidence for a general binaural interaction effect.     

Visuospatial working memory in specific language impairment: A meta-analysis

We conducted a meta-analysis of the data from studies comparing visuospatial working memory (WM) in children with specific language impairment (SLI) and typically developing (TD) children. The effect sizes of 21 studies (including 32 visuospatial storage tasks and 9 visuospatial central executive (CE) tasks) were identified via computerized database searches and the reference sections of the identified studies. Meta-analyses and moderator analyses were conducted to examine the magnitude of the differences in visuospatial storage and CE, and their relation to the inclusion criteria used for SLI and the age of the children. The results showed significant effect sizes for visuospatial storage (d = 0.49) and visuospatial CE (d = 0.63), indicating deficits in both components of visuospatial WM in children with SLI. The moderator analyses showed that greater impairment in visuospatial storage was associated with more pervasive language impairment, whereas age was not significant associated with visuospatial WM. The finding of deficits in visuospatial WM suggests domain-general impairments in children with SLI. It raises questions about the language-specificity of a diagnosis of SLI. Careful attention should thus be paid to both verbal and visuospatial WM in clinical practice, and especially in those children with pervasive language impairments.     

脑干听觉诱发电位在听阈正常的语言发育迟缓患儿中的意义

目的 探讨脑干听觉诱发电位（BAEP）在听阈正常而语言发育迟缓患儿中的变化规律及应用价值.方法 分析100例听阈正常而语言发育迟缓患儿BAEP的变化规律;按年龄分组比较两个年龄段之间各波的延长时间.结果 （1）BAEP正常10例,异常90例,BAEP表现为Ⅰ、Ⅴ波潜伏期（PL）延长,Ⅲ~Ⅴ、Ⅰ~Ⅴ波峰间期（IPL）延长;（2）随着年龄增长,Ⅴ波PL与Ⅲ~Ⅴ波IPL延长时间越长.结论 Ⅰ波、Ⅴ波延长对早期诊断听阈正常而语言发育迟缓患儿具有一定的意义,说明即使听阈正常也可能存在听觉传导通路异常,且随着年龄增加,脑干上段受损越严重.