Optimal (‘Wiener’) digital filtering of auditory evoked potentials: use of coherence estimates

Auditory evoked potentials (AEPs) to 40 Hz clicks and amplitude-modulated 500 Hz tones in human subjects were digitally filtered using an optimal (‘Wiener’) filter uniquely determined for each AEP. Use of coherence functions to compute coefficients appropriate for filtering grand average AEPs or subsets such as split-half averages is described. Wiener-filtered AEPs correlated better than unfiltered AEPs with split-half replicates and with references AEPs (obtained with long data collection periods). Visual detection thresholds were lower (more sensitive) for the Wiener-filtered AEPs, but not as low as objectively determined thresholds using coherence values.     

The lateral line mechanoreceptive mesencephalic,diencephalic, and telencephalic regions in the thornback ray,Platyrhinoidis triseriata (Elasmobranchii)

Central lateral line pathways were mapped in the thronback ray, Platyrhinoidis triseriata, by analyzing depth profiles of averaged evoked potentials (AEPs), multiunit activity (MUA), and single unit recordings. Neural activity evoked by contra- or ipsilateral posterior lateral line nerve (pLLN) shock is restricted to the tectum mesencephali, the dorsomedial nucleus (DMN) and anterior nucleus (AN) of the mesencephalic nuclear complex, the posterior central thalamic nucleus (PCT), the lateral tuberal nucleus of the hypothalamus, and the deep medial pallium of the telencephalon (Figs. 2, 3, 4, 6, 7). Neural responses (AEPs and MUA) recorded in different lateral line areas differ with respect to shape, dynamic response properties, and/or latencies (Figs. 9, 10 and Table 1). Ipsilaterally recorded mesencephalic and diencephalic AEPs are less pronounced and of longer latency than their contralateral counterpart (Fig. 9 and Table 1). In contrast, AEP recorded in the telencephalon show a weak ipsilateral preference. If stimulated with a low amplitude water wave most DMN, AN, and tectal lateral line units respond in the frequency range 6.5 Hz to 200 Hz. Best frequencies (in terms of least displacement) are 75-150 Hz with a peak-to-peak water displacement of 0.04 micron sufficient to evoke a response in the most sensitive units (Fig. 11A, B, C). DMN and AN lateral line units have small excitatory receptive fields (RFs). Anterior, middle, and posterior body surfaces map onto the rostral, middle, and posterior brain surfaces of the contralateral DMN (Fig. 12). Some units recorded in the PCT are bimodal; they respond to a hydrodynamic flow field--generated with a ruler approaching the fish--only if the light is on and the eye facing the ruler is left uncovered (Fig. 13).     

Physiology of lateral line mechanoreceptive regions in the elasmobranch brain

The physiology of mechanoreceptive lateral line areas was investigated in the thornback guitarfish, Platyrhinoidis triseriata, from medulla to telecephalon, using averaged evoked potentials (AEPs) and unit responses as windows to brain functions. Responses were analysed with respect to frequency sensitivity, intensity functions, influence of stimulus repetition rate, response latency, receptive field (RF) organization and multimodal interaction. 1. Following a quasi-natural vibrating sphere stimulus, neural responses were recorded in the medullary medial octavolateralis nucleus (MON), the dorsal (DMN) and anterior (AN) nucleus of the mesencephalic nuclear complex, the diencephalic lateral tuberal nucleus (LTN), and a telencephalic area which may correspond to the medial pallium (Figs. 2, 3, 13, 14, 15, 16). 2. Within the test range of 6.5-200 Hz all lateral line areas investigated responded to minute water vibrations. Best frequencies (in terms of displacement) were between 75 and 200 Hz with threshold values for AEPs as low as 0.005 microns peak-to-peak (p-p) water displacement calculated at the skin surface (Fig. 6). 3. AEP-responses to a vibrating sphere stimulus recorded in the MON are tonic or phasic-tonic, i.e., responses are strongest at stimulus onset but last for the whole stimulus duration in form of a frequency following response (Fig. 3). DMN and AN responses are phasic or phasic-tonic. Units recorded in the MON are phase coupled to the stimulus, those recorded in the DMN, AN or LTN are usually not (Figs. 5, 8, 9). Diencephalic LTN and telencephalic lateral line responses (AEPs) often are purely phasic. However, in the diencephalic LTN tonic and/or off-responses can be recorded (Fig. 11). 4. For the frequencies 25, 50, and 100 Hz, the dynamic intensity range of lateral line areas varies from 12.8 to at least 91.6 dB (AEP) respectively 8.9 and 92 dB (few unit and single unit recordings) (Fig. 7). 5. Mesencephalic, diencephalic, and telecephalic RFs, based on the evaluation of AEPs or multiunit activity (MUA), are usually contralateral (AN and LTN) or ipsi- and contralateral (telencephalon) and often complex (Figs. 10, 12, 16). 6. In many cases no obvious interactions between different modalities (vibrating sphere, electric field stimulus, and/or a light flash) were seen. However, some recording sites in the mesencephalic AN and the diencephalic LTN showed bimodal interactions in that an electric field stimulus decreased or increased the amplitude of a lateral line response and vice versa (Fig. 13 B).     

Impaired attentional modulation of auditory evoked potentials in N-methyl-D-aspartate NR1 hypomorphic mice

In human neurophysiology, auditory event-related potentials (AEPs) are used to investigate cognitive processes such as selective attention. Selective attention to specific tones causes a negative enhancement of AEPs known as processing negativity (PN), which is reduced in patients with schizophrenia. The evidence suggests that impaired selective attention in these patients may partially depend on deficient N-methyl-D-aspartate receptor (NMDAR)-mediated signaling. The goal of this study was to corroborate the involvement of the NMDAR in selective attention using a mouse model. To this end, we first investigated the presence of PN-like activity in C57BL/6J mice by recording AEPs during a fear-conditioning paradigm. Two alternating trains of tones, differing in stimulus duration, were presented on 7 subsequent days. One group received a mild foot shock delivered within the presentation of one train (conditioning train) on days 3-5 (conditioning days), while controls were never shocked. The fear-conditioned group (n= 9) indeed showed a PN-like activity during conditioning days manifested as a significant positive enhancement in the AEPs to the stimuli in the conditioning train that was not observed in the controls. The same paradigm was then applied to mice with reduced expression of the NMDAR1 (NR1) subunit and to a wild-type control group (each group n= 6). The NR1 mutants showed an associative AEP enhancement, but its magnitude was significantly reduced as compared with the magnitude in wild-type mice. We conclude that electrophysiological manifestations of selective attention are observable yet of different polarity in mice and that they require intact NMDAR-mediated signaling. Thus, deficient NMDAR functioning may contribute to abnormal selective attention in schizophrenia.     

Otoacoustic emissions,auditory evoked potentials and self-reported gender in people affected by disorders of sex development (DSD)

Both otoacoustic emissions (OAEs) and auditory evoked potentials (AEPs) are sexually dimorphic, and both are believed to be influenced by prenatal androgen exposure. OAEs and AEPs were collected from people affected by 1 of 3 categories of disorders of sex development (DSD) — (1) women with complete androgen insensitivity syndrome (CAIS); (2) women with congenital adrenal hyperplasia (CAH); and (3) individuals with 46,XY DSD including prenatal androgen exposure who developed a male gender despite initial rearing as females (men with DSD). Gender identity (GI) and role (GR) were measured both retrospectively and at the time of study participation, using standardized questionnaires. The main objective of this study was to determine if patterns of OAEs and AEPs correlate with gender in people affected by DSD and in controls. A second objective was to assess if OAE and AEP patterns differed according to degrees of prenatal androgen exposure across groups. Control males, men with DSD, and women with CAH produced fewer spontaneous OAEs (SOAEs) – the male-typical pattern – than control females and women with CAIS. Additionally, the number of SOAEs produced correlated with gender development across all groups tested. Although some sex differences in AEPs were observed between control males and females, AEP measures did not correlate with gender development, nor did they vary according to degrees of prenatal androgen exposure, among people with DSD. Thus, OAEs, but not AEPs, may prove useful as bioassays for assessing early brain exposure to androgens and predicting gender development in people with DSD.     

电刺激大鼠下丘脑和不定带引起的脊髓平均诱发电位

形态学已证实下丘脑-脊髓直接投射。本实验试对这一投射的电刺激反应作一些探讨。在刺激下丘脑时可在脊髓记录到一些尖锋样平均诱发电位(AEPs)。这些AEPs可以跟随200Hz 以上的高频双刺激,对窒息的耐受性较强。有效刺激点主要分布在下丘脑中部穹窿周围以及不定带。我们认为这些 AEPs可能代表沿下丘脑-脊髓直接投射通路传导的兴奋。对不定带-脊髓投射所作同样的实验,结果与前者相似。     

Single-trial latency variability does not contribute to fast habituation of the long-latency averaged auditory evoked potential in the albino rat

Fas habituation (FH) is defined as a general reduction in long-latency, vertex-recorded, averaged auditory evoked potential (AEP) amplitude that occurs in response to the second of a pair of acoustic stimuli. Our laboratory has been studying FH in a variety of human populations with different paradigms and has interpreted it to be a measure of neural attentional mechanism(s) and/or resource allocation related to the processing of cognitive information. We have also reported an analogous phenomenon in the rat. In the present investigation, we examined the relationship between FH (viz., averaged AEP component amplitude decrement) and the single-trial latency variability of the AEP peaks comprising that component. Specifically, AEPs were obtained to 60 paired-tone stimuli from unanesthetized and restrained albino rats previously implanted with chronic skull electrodes. Using a template-matching algorithm similar to that used by Michalewski et al. (Electroenceph. clin. Neurophysiol., 1986, 65:59–71), the latency variability for each animal was computed for the N1 and P2 peaks of the single-trial AEPs that were used to compose the averaged wave form. Findings indicated that (a) there was no difference in single-trial latency variability for these peaks either within or across tones, and (b) there was no relationship between single-trial latency variability for either the N1 or the P2 peaks and the overall peak-to-peak amplitude (N1-P2) of the averaged wave form in response to the second tone. Thus, FH of the N1-P2 (i.e. Peak 2) amplitude in the rat is not due to an increase in latency variability across tones.     

Tree-based ensembles unveil the microhabitat suitability for the invasive bleak (Alburnus alburnus L.) and pumpkinseed (Lepomis gibbosus L.): Introducing XGBoost to eco-informatics

Random Forests (RFs) and Gradient Boosting Machines (GBMs) are popular approaches for habitat suitability modelling in environmental flow assessment. However, both present some limitations theoretically solved by alternative tree-based ensemble techniques (e.g. conditional RFs or oblique RFs). Among them, eXtreme Gradient Boosting machines (XGBoost) has proven to be another promising technique that mixes subroutines developed for RFs and GBMs. To inspect the capabilities of these alternative techniques, RFs and GBMs were compared with: conditional RFs, oblique RFs and XGBoost by modelling, at the micro-scale, the habitat suitability for the invasive bleak (Alburnus alburnus L.) and pumpkinseed (Lepomis gibbosus L.). XGBoost outperformed the other approaches, particularly conditional and oblique RFs, although there were no statistical differences with standard RFs and GBMs. The partial dependence plots highlighted the lacustrine origins of pumpkinseed and the preference for lentic habitats of bleak. However, the latter depicted a larger tolerance for rapid microhabitats found in run-type river segments, which is likely to hinder the management of flow regimes to control its invasion. The difference in the computational burden and, especially, the characteristics of datasets on microhabitat use (low data prevalence and high overlapping between categories) led us to conclude that, in the short term, XGBoost is not destined to replace properly optimised RFs and GBMs in the process of habitat suitability modelling at the micro-scale.     

Sensitivity of bioelectrical impedance to detect changes in human body composition

The purpose of this study was to compare the estimates of lean body mass (LBM) and percent body fat (%BF), as predicted by bioelectrical impedance (BIA) and sum of skinfolds (SF), with those derived by hydrostatic weighing (HW) obtained before and after a 10-wk diet and exercise regimen. The experimental (E) group consisted of 17 healthy male subjects; 20 healthy males served as the control (C) group. Post hoc Scheffé contrasts computed on E group data indicated that, for both LBM and %BF, the Lukaski and Segal BIA equations, as well as the Durnin SF equation, derived mean values that were not significantly different (0.05 significance level) from HW in both pre- and postregimen conditions. For LBM, the same equations derived the following significant (P less than 0.01) correlation coefficients for both pre- and postregimen data: Lukaski, 0.87 and 0.85; Segal, 0.89 and 0.87; and Durnin, 0.90 and 0.88. For %BF, the correlation coefficients were slightly lower but remained statistically significant (P less than 0.01). The findings of this study suggest that the BIA method, by use of either the Lukaski or Segal prediction equations, is a valid means of predicting changes in human body composition as measured by the Siri transformation of body density.     

Activation of duration-sensitive auditory cortical fields in humans

The influence of stimulus duration on auditory evoked potentials (AEPs) was examined for tones varying randomly in duration, location, and frequency in an auditory selective attention task. Stimulus duration effects were isolated as duration difference waves by subtracting AEPs to short duration tones from AEPs to longer duration tones of identical location, frequency and rise time. This analysis revealed that AEP components generally increased in amplitude and decreased in latency with increments in signal duration, with evidence of longer temporal integration times for lower frequency tones. Different temporal integration functions were seen for different N1 subcomponents. The results suggest that different auditory cortical areas have different temporal integration times, and that these functions vary as a function of tone frequency.     

A worldwide analysis of AG molecular diversity inferred from serology.

Ten population samples from different geographic origins were tested serologically for the AG polymorphism of human beta-lipoproteins. Their haplotype frequencies were used with previously published data to perform a wide analysis of AG genetic differentiations throughout the world. Coancestry coefficients were computed from weighted F(ST)s among populations by using a matrix of molecular distances among AG haplotypes, which is here determined on the basis of DNA studies. Coancestry coefficients derived from unweighted F(ST)s and more classical Prevosti distances were computed on the same data and used for a comparison. In all cases a highly significant correlation was found between genetics and geography on a worldwide scale, while the significance of the correlation with linguistics differed. A test of significance of the pairwise F(ST)s among populations also gave different results depending on whether the molecular distance matrix among AG haplotypes was included. Globally, this study shows that in spite of being highly significantly correlated to each other, different genetic distance measures can lead to different interpretations of the same data set. Moreover, the elucidation of the molecular models related to the presently known serological polymorphisms may represent an additional tool for analyzing such polymorphisms in human population genetics studies.     

Immediate expansion of receptive fields of neurons in area 3b of macaque monkeys after digit denervation.

The short-term effect of total or partial single-digit denervation on receptive fields (RFs) of neurons in somatosensory cortex (area 3b) was examined in five macaque monkeys. In two animals, after denervation by amputation, it was found that electrode positions that initially recorded neurons with RFs on the amputated digit had new RFs extending from the wound. Often the new fields were on adjacent digits. Neurons with initial RFs that were partially amputated, or in some cases close to but not on the amputated digit, showed considerable expansion of the remaining RF. In three monkeys local anesthesia was used to provide a temporary denervation. In these experiments electrodes were placed in equivalent positions in both cortices. The effect on cortex contralateral to the denervation was similar to that seen with amputation. However, after anesthesia returned to the digit, the expanded RFs contracted. In cortex ipsilateral to the denervation, RFs were on the opposite unaffected hand. These also rapidly expanded and then contracted, with the same time course as their counterparts in cortex contralateral to the denervation. Because of the rapidity of the expansion and its temporary nature with short-term denervation, the basis of the effect is probably an unmasking of existing but normally unexpressed connections, which are normally inhibited by the intact output from the denervated area. The wide arborization fields of thalamocortical afferents provide a potential source for the unmasked sensitivity. A mechanism for the inhibition that normally suppresses the expression of large RFs is not readily apparent. However, work in other species suggests that peripheral C fibers provide the primary source of input to central inhibitory circuits.     

Characteristics of the receptive fields of neurons of the posterior temporal area of the cortex of the cat

In records of 219 single units in the posterotemporal cortical area (field 21) of nonanaesthetized cats, 51% of cells reacted to visual stimulation. The neurones had receptive fields (RFs) with central (0-10 degrees) or peripheral (10-52 degrees) localization in the visual field, their size increasing with eccentricity. Carting of RFs by a light bar scanning the visual field revealed a considerable variability of RFs shape, size and orientation in different cells. RFs sizes of the majority of recorded cells (100-1000 grad) were very large and exceeded the size of large RFs of neurones in the primary projection zone of the visual cortex.     

Correlation of evoked potentials in the frontal cortex and hippocampus of cats in emotional stress

Averaged auditory evoked potentials (AEPs) were recorded in symmetric points of the frontal cortex and dorsal hippocampus of cats performing acquired conditioned food-procuring reaction reinforced in 100% cases, urgent transition to 30%-reinforcement, and return to 100%-reinforcement. Emotional stress estimated by a heart rate rise developed during increased food motivation of a cat as well as during change in ordinary food-procuring stereotype. The emotional stress was accompanied by a high positive correlation of cortical and hippocampal AEPs. Decrease in the stress level led to a drop between AEP correlations and appearance of their negative values. In emotional stress, the interactions between the frontal cortex and dorsal hippocampus were asymmetric: right-side correlations were higher.     

Representing three-dimensional objects by sets of activities of receptive fields

Idealized models of receptive fields (RFs) can be used as building blocks for the creation of powerful distributed computation systems. The present report concentrates on investigating the utility of collections of RFs in representing three-dimensional objects under changing viewing conditions. The main requirement in this task is that the pattern of activity of RFs vary as little as possible when the object and the camera move relative to each other. I propose a method for representing objects by RF activities, based on the observation that, in the case of rotation around a fixed axis, differences of activities of RFs that are properly situated with respect to that axis remain invariant. Results of computational experiments suggest that a representation scheme based on this algorithm for the choice of stable pairs of RFs would perform consistently better than a scheme involving random sets of RFs. The proposed scheme may be useful under object or camera rotation, both for ideal lambertian objects, and for real-world objects such as human faces.     

The function of sensory information from the first somatosensory cortex for facial movements during ingestion in cats

The aim of the present study was to investigate the relationship between the facial region of the first somatosensory cortex (facial SI) and facial region of the motor cortex (facial MI), as the basis of orofacial behaviors during ingestion of fish paste. Area M in the ventral cortex of the cruciate sulcus that was defined as part of the facial MI by and, showed various facial twitches evoked by intracortical microstimulation (ICMS) and recorded many mastication-related neurons (MRNs). Many MRNs in area M had receptive fields (RFs) in lingual, perioral and mandibular regions. The 60% value of activity patterns of MRNs (n = 124) recorded in area M of normal cats, were the pre-SB type (the sustained and pre-movement type) that showed increased firing prior to the start of mastication and then tonic activity during the masticatory period. MRNs recorded in area M of cats with the facial SI lesion, showed a noticeable decrease in MRNs with RFs in the perioral and mandibular regions and with activity of the pre-SB type. These results strongly suggest that blocking facial SI sensory inputs evoked by mastication interferes with the relay of important facial sensory information to area M required for the appropriate manipulation of food during mastication.     

Sustained potential shifts,alterations in acoustic evoked potential amplitude and bradycardiac responses to the onset of illumination in the goldfish (Carassius auratus)

Sustained potential shift's (SPSs) and changes in acoustic evoked potential (AEP) amplitudes were recorded from medullary and mid-brain regions in restrained goldfish (Carassius auratus) in response to the onset of illumination against a sensory background restricted to repetitive (1/s) acoustic stimulation. At the tectal surface, a long duration negative SPS, significant 5–10 s after the onset of illumination, was recorded with a maximum negativity of ca. 145 V. Changes in acoustic responsiveness were also most apparent in the mid-brain where attenuations in AEP amplitude of ca. 15% were recorded.In general, AEPs exhibited attenuated amplitudes in response to the onset of illumination, perhaps reflecting attentional rather than arousal processes, arousal generally being associated with heightened sensory responsiveness. Changes in the amplitude of the medullary AEPs were directly related to the magnitude of bradycardiac responses such that lesser attenuations of the medullary AEP were associated with greater magnitude bradycardiac responses, suggesting a possible interaction of attentional and arousal processes.In response to repeated onset of illumination, SPSs tended towards increasing positivity (increasing in positivity at the medullary surface; decreasing in negativity at the tectal surface). The attenuation of AEPs recorded from the medulla and mid-brain habituated in response to stimulus repetition.Changes in amplitude of AEPs (AEP) recorded from the telencephalon and the torus semicircularis region of the mid-brain were correlated with locally recorded SPSs. At the telencephalon, this correlation was inverse; enhanced AEP amplitudes being associated with SPS negativity, attenuated AEP amplitudes with SPS positivity. In the torus semicircularis, experiential changes in SPS and AEP were directly correlated. As the SPS is considered to reflect glial redistribution of [K⁺]_e (Roitbak 1983), glia may contribute to changes in measures of sensory responsivity, such as the AEP, during changes in behavioural state.Abbreviations AEP Acoustic Evoked Potential - AEP Event-related change in amplitude of AEP following onset of illumination - SPS Sustained Potential Shift - [K⁺]_e Extracellular concentration of K⁺     

猫纹状皮层神经元整合野的形状和范围

用正弦调制的移动光栅测量了１２０个猫纹状皮层神经元在长度和宽度方向上的空间整合特性。结果表明：（１）大多数细胞的传统感受野具有长宽相近的结构,然而它们的整合野多数是宽而短或者窄而长的长条形。（２）整合野大小为传统感受野的２—７倍,平均为３．７倍。简单细胞与复杂细胞整合野的大小没有显著差别。（３）随着感受野的视网膜偏心度的增加,整合野大小有逐渐增大的趋势。（４）感受野靠近视网膜垂直中线的细胞,其整合野可以跨越中线进入同侧视野;在两半视野中整合野的范围没有显著差异,但是同侧视野整合野的作用强度明显弱于对侧视野。以上结果提示,初级视皮层神经元能够对大范围内的图形特征进行整合,这种整合作用来自两侧视野。     

Auditory evoked potentials for the assessment of depth of anaesthesia: different configurations of artefact detection algorithms.

Monitoring the depth of anaesthesia has become an important research topic in the field of biosignal processing. Auditory evoked potentials (AEPs) have been shown to be a promising tool for this purpose. Signals recorded in the noisy environment of an operating theatre are often contaminated by artefacts. Thus, artefact detection and elimination in the underlying electroencephalogram (EEG) are mandatory before AEP extraction. Determination of a suitable artefact detection configuration based on EEG data from a clinical study is described. Artefact detection algorithms and an AEP extraction procedure encompassing the artefact detection results are presented. Different configurations of artefact detection algorithms are evaluated using an AEP verification procedure and support vector machines to determine a suitable configuration for the assessment of depth of anaesthesia using AEPs.     

Sensory-Motor Interactions for Vocal Pitch Monitoring in Non-Primary Human Auditory Cortex

The neural mechanisms underlying processing of auditory feedback during self-vocalization are poorly understood. One technique used to study the role of auditory feedback involves shifting the pitch of the feedback that a speaker receives, known as pitch-shifted feedback. We utilized a pitch shift self-vocalization and playback paradigm to investigate the underlying neural mechanisms of audio-vocal interaction. High-resolution electrocorticography (ECoG) signals were recorded directly from auditory cortex of 10 human subjects while they vocalized and received brief downward (−100 cents) pitch perturbations in their voice auditory feedback (speaking task). ECoG was also recorded when subjects passively listened to playback of their own pitch-shifted vocalizations. Feedback pitch perturbations elicited average evoked potential (AEP) and event-related band power (ERBP) responses, primarily in the high gamma (70–150 Hz) range, in focal areas of non-primary auditory cortex on superior temporal gyrus (STG). The AEPs and high gamma responses were both modulated by speaking compared with playback in a subset of STG contacts. From these contacts, a majority showed significant enhancement of high gamma power and AEP responses during speaking while the remaining contacts showed attenuated response amplitudes. The speaking-induced enhancement effect suggests that engaging the vocal motor system can modulate auditory cortical processing of self-produced sounds in such a way as to increase neural sensitivity for feedback pitch error detection. It is likely that mechanisms such as efference copies may be involved in this process, and modulation of AEP and high gamma responses imply that such modulatory effects may affect different cortical generators within distinctive functional networks that drive voice production and control.