Mismatch Negativity in Children with Autism and Typical Development

Children with autism are often characterized as having abnormalities in auditory processing. This study examined automatic and active processing of simple auditory stimuli in children using a component of event related potentials, the mismatch negativity (MMN). Amplitude of MMN in children with autism was significantly smaller than in children with typical development in unattended conditions. However, children with autism exhibited a typical amplitude MMN when attending to the stimuli. Receptive language and MMN were not related in children with autism. Findings support the idea of abnormal automatic auditory processing by children with autism. Auditory discrimination of infrequent changes in streams of sounds appears to be accomplished through a different mechanism than in typical children, specifically through the investment of attention.     

Tactile intensity and population codes

An important question in neuroscience is how different aspects of a stimulus are encoded at different stages of neural processing. In this review, I discuss studies investigating the peripheral neural code for perceived intensity in touch. One of the recurrent themes in this line of research is that information about stimulus intensity is encoded in the activity of populations of neurons. Not only is information integrated across afferents of a given type, but information is also combined across submodalities to yield a unified percept of stimulus intensity. The convergence of information stemming from multiple submodalities is particularly interesting in light of the fact that these are generally thought to be parallel sensory channels with distinct sensory functions and little cross-channel interactions. I discuss implications of a recently proposed model of intensity coding for psychophysical functions and for the coding of intensity in cortex. I also briefly review the peripheral coding of intensity in other sensory modalities.     

Double peak sensory responses: effects of capsaicin

The aim of this study is to verify whether degeneration of skin receptors or intradermal nerve endings by topical application of capsaicin modifies the double peak response obtained by submaximal anodal stimulation. Five healthy volunteers topically applied capsaicin to the finger-tip of digit III (on the distal phalanx) four times daily for 4–5 weeks. Before and after local capsaicin applications, we studied the following electrophysiological findings: compound sensory action potential (CSAP), double peak response, sensory threshold and double peak stimulus intensity. Local capsaicin application causes disappearance or decrease of the second component of the double peak, which gradually increases after the suspension of capsaicin. Conversely, no significant differences were observed for CSAP, sensory threshold and double peak stimulus intensity. This study suggests that the second component of the double peak may be a diagnostic tool suitable to show an impairment of the extreme segments of sensory nerve fibres in distal sensory axonopathy in the early stages of damage, when receptors or skin nerve endings are impaired but undetectable by standard nerve conduction studies.     

Basal ganglia physiology and pathophysiology: a reappraisal

Current theories of basal ganglia (BG) function based on suppression of activity in the ventrolateral thalamic-cortical circuits by the globus pallidus internal segment are inconsistent with accumulating evidence, demonstrating the need for reconsideration. Changes in busting, oscillatory and synchronous neuronal activities have been indicted as pathophyisological mechanisms but they are unaccompanied by any mechanistic explanatory theory and rely on the same basic assumptions as previous theories now suspect. These notions and theories are reviewed and an alternative is proposed. The systems oscillators theory presented here proposes that the BG is a network of sets of interconnected closed neural loops functioning as oscillators. Its unique physiological and pathophysiological mechanisms are explored.     

On the Interaction Between Perceptual and Response Selection: Neuropsychological Evidence

We examined the relations between selection for perception and selection for action in a patient FK, with bilateral damage to his temporal and medial frontal cortices. The task required a simple grasp response to a common object (a cup) in the presence of a distractor (another cup). The target was cued by colour or location, and FK made manual responses. We examined the effects on performance of cued and uncued dimensions of both the target and the distractor. FK was impaired at perceptually selecting the target when cued by colour, when the target colour but not its location changed on successive trials. The effect was sensitive to the relative orientations of targets and distractors, indicating an effect of action selection on perceptual selection, when perceptual selection was weakly instantiated. The dimension-specific carry-over effect on reaching was enhanced when there was a temporal delay between a cue and the response, and it disappeared when there was a between-trial delay. The results indicate that perceptual and action selection systems interact to determine the efficiency with which actions are selected to particular objects.     

Neurophysiological findings in long-term survivors of acute lymphoblastic leukaemia in childhood treated with the BFM protocol 81 SR-A/B

Monitoring of therapy-related late effects after acute lymphoblastic leukaemia (ALL) therapy in childhood has become an increasingly important field in posttherapeutic patient surveillance. The usefulness of neurophysiological investigations (e.g. EEG, evoked potentials (EP)) as part of these attempts is controversial. The present report focuses on this problem and the question whether and to what extent routinely performed EEG recordings and visual evoked potentials (VEP) were correlated with further measures of CNS integrity. EEGs and VEPs were recorded in 163 asymptomatic long-term survivors of ALL in childhood during a large retrospective multicentre study evaluating CNS late sequelae following antileukaemic therapy. Fifty-two ALL long-term survivors (4.5–10.6 years after end of therapy, median: 8.8 years), who had been treated according to BFM-81 SR-A (n=30) or SR-B (n=22) were selected for this analysis focusing on therapy-related CNS late effects. Therapy protocols differed with regard to the mode for CNS prophylaxis: SR-A, cranial irradiation with intrathecal methotrexate; SR-B, intrathecal and iv methotrexate. Neurophysiological findings were correlated with illness- and treatment-related parameters, as well as with data on the morphological, neurological and psychological status of the CNS. At the time of follow-up neurophysiological measures were abnormal in 28/52 cases (53.8%). Neither illness- nor therapy-specific differences in CNS prophylaxis showed any relationship to EEG/VEP outcome any relationship to EEG/VEP outcome in this reduced group of the whole study population. Children with EEG/VEP abnormalities showed a significantly higher incidence of structural CNS disturbances compared to those with inconspicuous neurophysiological recordings (60.9% vs 31.8%). However, in this special subject group there was no specific neurophysiological finding for a specific morphological substrate, neurological or psychological deficiency and vice versa. Conclusion Routinely performed EEG/VEP investi gations are not very helpful measures to predict the presence or degree of behavioural deficiencies, neuro‐logical disturbances, or morphological CNS abnor‐malities. Patients who received cranial irradiation or systemic methotrexate applications showed the same incidence of neurophysiological disturbances without evidence for specific neurotoxic correlates. Received: 29 March 1996 / Accepted: 9 December 1996     

Interactive graphics in the analysis of neuronal spike train data

This paper describes an interactive graphics system developed to facilitate the investigation of complex relationships between experimental and theoretical data in the neurosciences. Graphics affords unique insights into data structure and model properties which are difficult to obtain using other computational media. The data under analysis consists of trains of spike-like electrical activity recorded from single nerve cells. The complete data base is organized into modular subunits to allow flexible and rapid positioning on data of interest. The graphics system was developed utilizing three available computers, an IMLAC $\text{PDS}\text{1D}$, an IBM $\text{360}\text{91}$, and a DEC $\text{PDP}\text{12}$. The IMLAC is the focal point of system interaction and is used to control the other two computers. There is a data path between the IBM $\text{360}\text{91}$ and the $\text{PDP}\text{12}$ through the IMLAC. The $\text{PDP}\text{12}$ collects, edits, and transmits the experimental data to the auxiliary storage of the IBM $\text{360}\text{91}$. The IBM $\text{360}\text{91}$ is a host for a FORTRAN graphics program using IMGRAF subroutines. The user, at the IMLAC, controls the flow of the graphics program at the IBM $\text{360}\text{91}$ as well as the data transmission from the $\text{PDP}\text{12}$. Using appropriate commands, new data can be acquired from the $\text{PDP}\text{12}$, analyzed immediately, and the results displayed on the screen. The interactive graphics program is structured as a resident executive with a number of phases available for overlay at execution. The major phases include data base generation, modeling, optimization, data processing and validation.     

Masking and the perception of stop consonants: psychoacoustical and electrophysiological experiments

Summary Naturally spoken German words Stahl [ta:1] and Spott [ pot] were prepared with gaps (silent intervals) of different lengths between the fricative () and the corresponding stop consonant [t] or [p], and with various fricative sound pressure levels. Reduction of the normally occurring pause between the fricative and the stop consonant [t] or [p] to less than 10 ms or 20 ms, respectively, leads to suppression of the acoustically present stop, e.g. Spott [ pot] is heard as Schott [ ot]. We compare the results of single neuron recordings from animals to results from psychophysical tests on humans, since animal experiments exclude the effects of possible speech-specific perceptual processes. The animal experiments were done on anesthetized cats, from which we recorded single unit activity in the medial geniculate body (MGB). For neurons which represented the stop consonant by a discharge increase, we varied the gap between the fricative and its following stop from 0 up to 120 ms. For all neurons the responses to the stop consonant were positively correlated with gap length and always showed a minimum for gaps of 30 ms or less. This critical interval for minimum responses matches that found in the human psychophysical measurements of stop consonant suppression. The time course of the interval dependence of neural responses follows the pattern of the psychoacoustical measurements in humans. Suppression of neural responses to the stop did not depend on whether the neuron responded to either the preceding fricative or the following vowel. Neural (animal experiment) and perceptual (human experiment) responses to the stop consonant show the same dependence on the fricative sound pressure level. The results are interpreted as forward masking. The neurophysiological data correspond well to experiments in which discharge reduction is elicited with simple signals (forward masking). Our experiments are evidence that auditory masking plays a role in the suppression of stop consonants and that this phenomenon can be explained without assuming phonetic processes in speech perception at a higher level or specific for humans.     

选择性注意的神经生理学解释

本文从听觉生理学的角度对以往的选择性注意理论模型进行宏观分析，提出了选择性注意的“多重选择理论”模型，并提供了相关的神经生理学理论依据。该模型进一步确认了人类选择性注意过程既存在着初期的过滤过程．也存在着其后的选择过程。认为在信息进入感觉器官之后．衰减的过程并不明显。同时通过丘脑的网状结构上行激动系统所具有只容许的单信息通过的门控功能，排除了能量分配理论中的关于大脑的能量分配限制的说法。     

60例糖尿病患者的腓总神经电生理研究

目的：探讨糖尿病性神经病的电生理改变特征。方法：在60例Ⅱ型糖尿病患者中,有神经病学症状或体征的29例为A组,无神经病学症状或体征的31例为B组。C组为正常对照。在三组中测定腓总神经运动神经传导速度（MCV）,远端潜伏期（DPL）,复合肌肉动作电位（CMAP）的波幅、时限,检测数据进行t检验。结果：A组与B、C组分别对比,A组MCV减慢（72％）,DPL延长（55％）,CMAP波幅降低（34％）、时限延长（52％）,有显著差异（P＜0.01）。B组与C组对比,B组CMAP波幅降低,有显著差异（P＜0.05）,B组16％DPL延长,对7％CMAP时限延长。各组内远端与近端刺激引出的CMAP波幅、时限对比均无显著差异（P＞0．05）。A组电生理异常率为100％,B组为23％。A组病程长但血糖水平同B组相近。结论：了解腓总神经的电生理改变有助于评价糖尿病性远端神经病与临床病程、进展的关系。