Gating of the Auditory Evoked Potential in Children and Adults

Auditory evoked potentials were recorded from 163 subjects, aged IS months to 55 years. A conditioning-testing paradigm was used to assess sensory gating. In this paradigm, click stimuli are presented in pairs to the subjects with a 0.5-second intrapair interval. In normal adults, the first stimulus activates or “conditions” sensory gating mechanisms. The strength of these mechanisms is “tested” by the second stimulus, which produces a response whose amplitude is significantly suppressed. This aspect of sensory gating was not reliably observed in our subjects until age 18 years. Younger subjects varied widely in their ability to demonstrate sensory gating. Mean levels of suppression increased during late childhood and adolescence, with no relationship to other changes in evoked potential amplitude and latency. Sensory gating would appear to be a late developing aspect of human sensory physiology.     

Effects of Methylphenidate on Hyperactive Children's Evoked Responses During Passive and Active Attention

Eighteen hyperactive clinical responders to methylphenidate were taken off medication and tested in two sessions during which they received an acute dose of methylphenidate and placebo in counterbalanced order. Seventeen normal boys of comparable age were tested without drugs. For both samples, evoked potentials were recorded during a Continuous Performance Test. Normal children made fewer errors of commission and omission and displayed faster reaction times than hyperactives tested under placebo. In addition, under active attention, the late positive component (LPC) of placebo-treated hyperactive boys' evoked responses exhibited smaller amplitude than normal controls'. Methylphenidate increased the amplitude of hyperactive patients' LPC and generally ameliorated their performance, especially commission errors and reaction times. The results confirmed previous findings of attentional disturbance in hyperactivity and normalization by methylphenidate of these patients' performance and electrophysiological activity during sustained attention.     

Directing Attention Toward Stimuli Affects the P300 But Not the Orienting Response

Whether attending to stimuli affects the orienting response and its habituation is not yet clear. EEG alpha suppression responses, electrodermal responses, and EEG evoked potential responses of two groups of subjects were compared. The Attend group was given instructions to pay attention to and count the 59 moderate intensity clicks (interstimulus interval = 15 sec). The Ignore group was instructed to “try not to let the clicks disturb your relaxed state.” Separate ANOVAs with repeated measures were used to evaluate all measures, and all showed significant effects for click repetition (habituation). Alpha suppression and change in log conductance showed no differences related to group. The P300 component of the average evoked potentials was significantly larger for the Attend group. We concluded that attending to, versus ignoring, stimuli does not have an appreciable effect on these two traditional measures of the orienting response, but it does affect the evoked potentials. The relationship between attention and “significance” is discussed.     

Effects of reward and methylphenidate on heart rate response morphology of augmenting and reducing children

In a group of attention and/or learning disordered children referred for a trial on methylphenidate, beat-to-beat analysis of heart rate (HR) to auditory stimuli showed the response to be affected by stimulus intensity, reward level, and drug condition (placebo or active). When the children were classified as augmenters or reducers on the basis of their event-related potentials to the 4 intensity levels, the reducers had significantly higher pretreatment HR response levels as well as quicker latencies to reach deceleration trough (anticipatory component) and acceleratory peak (rebound rise to the tones). The clinically titrated methylphenidate dosage levels for the subjects were related both to the augmenter-reducer classification and to pretreatment HR levels; that is, subjects who were ERP reducers and/or had higher HR levels, especially under reward conditions, were blindly titrated at higher levels than those who were augmenters and/or had lower HR levels.     

Normalizing Effects of Methylphenidate on Hyperactive Children's Vigilance Performance and Evoked Potentials

Evoked potentials during the × and B-X versions of the Continuous Performance Test (CPT) were evaluated in 29 hyperactive children after ingestion of placebo or methylphenidate (0.3 mg/Kg). Twenty-one age matched normal children were also assessed twice but without any drugs. In both tests, placebo-treated hyperactives made more omission and commission errors and displayed smaller late positive components (LPC) of the evoked response to salient experimental cues. Methylphenidate ameliorated hyperactives’ performance in both tasks and enlarged their LPCs in CPT-X. Several of these drug effects and diagnostic differences were absent for older hyperactive subjects, probably because some of the procedures were too easy for them. For younger patients the present tasks were sufficiently challenging, and the results reflect normalization of their deficits in sustained attention.     

P300 in multiple sclerosis: a preliminary report.

The P300 component of the event-related brain potential (ERP) elicited with auditory stimuli and pattern-shift visual evoked potentials (VEPs) was obtained from 16 patients with multiple sclerosis (MS) and 16 matched control subjects. P300 latency was significantly longer and component amplitude relatively depressed in the MS patients compared to control subjects. The P100 potential of the VEP also was delayed for both full-field and half-field stimulus conditions in the patients compared to control subjects. The findings suggest that the P300 ERP may reflect the cognitive decline associated with MS.     

Short-Term Habituation and Dishabituation of the Mismatch Negativity of the ERP

Standard tones of 1000 Hz and deviant tones of 1250 Hz were presented in random order, 1 stimulus/second. The probabilities of the standards and deviants were 90% and 10%, respectively. In one condition the subject counted the deviant stimuli and in the other condition he/she read a comic book. ERPs were separately averaged to 1) the standard preceding the deviant, 2) the “first deviant” preceded by at least 4 standards, 3) the “second deviant” (an occasional deviant immediately following the “first deviant”), 4) the first and 5) the second standard following the “first deviant,” 6) the first and 7) the second standard following the “second deviant.” It was found that the mismatch negativity evoked in both conditions by the first deviant was considerably larger than to the second deviant. Also the first standard following the first deviant evoked the mismatch negativity. The results are discussed in terms of parallel neuronal models of the stimuli as reflected by the mismatch negativity.     

Construct validity of the WCST in normal elderly and persons with Parkinson's disease

Separate principle component analyses of the WCST were conducted on 187 normal elderly and 181 persons with Parkinson's disease (PD). Adequate construct validity was found for “conceptualization/problem solving” and “failure to maintain set” factors in both groups. Perseverative and nonperseverative errors were related for the normal group, but not for the PD subjects. This may reflect the frontal systems deficit observed in PD. Additional principle component analyses were conducted with the WCST and measures of memory and attention. In neither the normal nor the PD group did the WCST significantly load with the memory and attention measures. This suggests that the WCST provides information about problem solving relatively independent of memory and attention functions for elderly persons.     

Effects of Methylphenidate on Young Adults'' Performance and Event-Related Potentials in a Vigilance and a Paired-Associates Learning Test

Twenty-two normal young men received a counterbalanced and double blind administration of 20 mg methylphenidate and placebo. Two tasks were administered in counterbalanced order: an uninterrupted 45-min vigilance test and a paired-associates learning test. As previously reported, under placebo, accuracy and speed decreased monotonically over the course of the vigil. This degradation of performance was significantly reduced by the stimulant drug. Event-related potentials (ERPs) were derived for correctly detected targets and nontargets. The most salient pharmacologic effects involved a late positive wave (P464) identified as P3b. Methylphenidate reversed or reduced the decrease in amplitude and increase in latency of P464 present over phases of the placebo session. The results suggest that the stimulant-induced improvement in performance may be mediated by enhancement of evaluation processes. In the paired-associates test there were no pharmacologic effects. Instead there was an unexpected, pronounced improvement in learning in the second session, irrespective of the substance administered. However, the ERP evoked by the “stimulus” cue of each pair was systematically related to the achievement of learning criteria. A late positive was identified as P3b (P555) increased significantly in amplitude following the attainment of learning. There were no amplitude changes among ERPs evoked in the early post-criterion, late post-criterion, or overlearning “phases.” Nor were there amplitude changes between early and late pre-criterion categories. Thus, ERP amplitude displayed a binary association with the achievement of learning.     

Emitted and Evoked P300 Potentials and Variation in Stimulus Probability

There have been a number of reports of a cerebral potential occurring at about the time of an expected but absent stimulus when absence provided significant information for the subject. This potential consists primarily of a positive peak occurring with a latency of about 300 msec with respect to the time of stimulus absence and is referred to as an emitted P300 potential. It has been conjectured that the emitted P300 is a manifestation of the same process that underlies the evoked P300 . Evidence supporting this hypothesis is provided by demonstrating that both the evoked and emitted P300 potentials are similarly affected by variation in event probability. A paradigm was used in which click presence and absence provided information. The relative probability of click presence and absence was experimentally manipulated. Both evoked and emitted p300 amplitude responded in the same way to event probability, larger for the less frequent event and smaller for the more frequent event.     

Recruitment properties and significance of short latency reflexes in neck and eye muscles evoked by brief lateral head accelerations

Short lateral head accelerations were applied to investigate the recruitment properties of the reflexes underlying the earliest ocular and cervical electromyographic reflex responses to these disturbances. Components of both reflexes are vestibular dependent and have been termed “ocular vestibular evoked myogenic potentials” and “cervical vestibular evoked myogenic potentials”, respectively. Previous investigations using a unilateral vestibular stimulus have indicated that some but not all these vestibular-dependent reflexes show a simple power law relationship to stimulus intensity. In particular, crossed otolith-ocular reflexes showed evidence of an inflection separating two types of behaviour. The present stimulus acts bilaterally, and only the earliest crossed otolith-ocular reflex, previously shown to have a strictly unilateral origin, showed evidence of an inflection. Reflex changes in ocular torsion could, in principle, correct for the changes associated with translation for an elevated eye, but our findings indicated that the responses were consistent with previous reports of tilt-type reflexes. For the neck, both vestibular and segmental (muscle spindle) reflexes were evoked and followed power law relationships, without any clear separation in sensitivity. Our findings are consistent with previous evidence of “tilt-like” reflexes evoked by lateral acceleration and suggest that the departure from a power law occurs as a consequence of a unilateral crossed pathway. For the neck, responses to transients are likely to always consist of both vestibular and non-vestibular (segmental) components. Most of the translation-evoked ocular and cervical reflexes appear to follow power law relationship to stimulus amplitude over a physiological range.     

The correlation between cerebrospinal fluid findings and evoked potentials during an acute MS attack

Clinically definite Multiple Sclerosis (MS) cases have an index greater than 0.7. Evoked potentials using geometrical patterns and click stimuli respectively and electrical stimulation of mixed nerve trunks evokes low level electrical impulses along a nerve. Prolonged latencies and changes in amplitude in these evoked potentials are thought to reflect sensory loss. This study is performed to determine whether there is a correlation between cerebrospinal fluid (CSF) findings and evoked potentials in MS during an acute MS attack. 10 male and 10 female patients' (20-55) mean (37.75) were included in to the study. They were diagnosed as definite MS with their clinical and MRI findings. During the acute attack 10 (50%) patients out of 20 had high Ig G index and one (10%) had oligoclonal band positivity. Of these 10 patients 8 (4 M, 4 F) had pathology in their evoked potentials while two had normal evoked potential findings. 8 of (80%) 10 patients whom had normal Ig G index during the acute attack had evoked potential pathology while (20%) had normal Ig G index and evoked potentials during the acute attack. Of the 8 patients which had high Ig G index and pathological evoked potential findings during acute attack were evaluated. VEP, BAEP latencies were found to be prolonged as Ig G index increased. (p < 0.05) However the same correlation can not be found with SEP parameters.     

Recovery of the cortical evoked potential from auditory stimulation in children and adults

The recovery of cortical evoked potentials to auditory stimulation was studied in a group of 12 young adults and 12 children aged 9.0–13.3 years. Subjects listened to single clicks and to pairs of clicks in which the interstimulus intervals (ISI's) varied, taking on values of 50, 100, 250, 500, 750, and 1000 msec. Average evoked potentials (AEP's) based on 50 repetitions were obtained to single clicks by coherent averaging and to the 2nd click of the pairs by automatically subtracting the evoked potential to each single click from the evoked potential to the corresponding pair and coherently averaging the remainder. In children, peak latencies of the P₁, N₁, and P₂ components of the AEP to the 2nd click of the pairs increased significantly with decreasing ISI; in adults, latencies similarly increased except in the case of the N₁ component. These increases were significantly larger in children than in adults, indicating that cortical recovery is slower in children and suggesting that cortical excitability in children may be lower. Peak latencies of the P₁, N₁, and P₂ components of the AEP to single clicks were significantly longer (16–21 msec) in the children.     

The Phasic Electrodermal Response As a Differentiated Complex Reflecting Stimulus Significance

To examine the influence of stimulus significance on the shin conductance response (SCR) a 21 sec. 1000-Hz tone was sounded variously In one car or the other. A click occurred during many tones, and a light signal always followed offset by 9 sec. Four groups were studied: one was told In press a pedal immediately on hearing any click; another only on hearing the click during a tone in a specified ear: a third was also to respond only to the specified ear, but was to withhold the press until the light following tone-offset; a fourth group simply listened without and response. Each of a series of predictions regarding the incremental effect of stimulus significance on the SCR was confirmed, at each point at which information was delivered on any trial - i.e., tone-onset, click, tone-offset, light-onset. This was true for both independent as well us for within-.S (between ear) comparisons. The presence of verbally-induced “significance” as well as the complex nature of its influence indicated the presence of central mediation in the elicitation of “peripheral” SCRs. Was identified which correlated uniquel with motor reaction time, did not habituate, and did not correlate with SCRs elicited by other signals in this task. The execute SCRs did not simply reflect judgments of “significance” rather, it was qualitatively distinguished from other SCRs which, in general, were associated with stimulus “significance” There was some evidence of an alerting SCR too, hut this was less sharply defined.     

Mismatch Negativity in Evoked Brain Potentials in Adolescents in Normal Conditions and Attention Deficit in Response to Presentation of Short-Duration Acoustic Stimuli

Experiments were performed to measure the critical duration of acoustic stimuli at which the generation of mismatch negativity is still possible in auditory evoked potentials in the human brain, arising in conditions of presentation of standard and deviant stimuli differing in terms of frequency (1000 and 1200 Hz respectively). Studies were performed in two groups of adolescents (aged 11–14 years): 1) those with normal attention characteristics and 2) children with attention deficit. The results showed that normal children had the same critical duration for sound stimuli at which mismatch negativity could be generated as adults. Mismatch negativity still appeared at a stimulus duration of 50 msec, while the mechanism generating mismatch negativity did not operate at durations of 30 and 11 msec. In children with attention deficit, statistically significant mismatch negativity was not seen at all durations of short acoustic stimuli (11, 30, and 50 msec).     

The influence of stimulus orientation on the vertex positive scalp potential evoked by faces

The scalp-recorded “vertex-positive peak” (VPP) evoked by images of faces in humans has previously been shown to be delayed when an originally upright stimulus is inverted or rotated by 90° (Jeffreys 1989a). This paper describes a study of the effects on this scalp potential of smaller face orientation changes (15° increments). The results showed that, under normal viewing conditions of clearly defined facial images, the VPP latency, which was minimal for face orientations within 15° of the vertical (0°), increased almost linearly for incremental rotations from 15 up to 90°, but was relatively unchanged or decreased slightly for further rotations from 90 up to 180°. Similar results were observed for clockwise and anticlockwise rotations, and for different facial representations. These stimulus orientation changes did not change the latency of simultaneously recorded, pattern-specific potentials recorded from occipital scalp locations; nor did they greatly affect the VPP amplitude. By contrast, rotations of “Mooney figure” stimuli away from the vertical produced concurrent reductions in both the perception of a face and the amplitude of the evoked VPP. Experiments in which the orientation of both the stimulus face and the subject's head were varied further showed that minimal latency VPP responses were evoked for parallel stimulus and viewing orientations. The speed of response is thus determined by the orientation of the subtended retinal image.     

Comparative Study of Conditioning of Averaged Evoked Responses By Coupling Sound and Light in Normal and Autistic Children

This study compared the conditioning of averaged evoked potentials in 11 psychotic and 11 normal children (57 experiments). Evoked potentials, like the blocking of alpha rhythm, can be conditioned by coupling a short sound of low intensity with an intense light flash. In normal children, the amplitude of the potential evoked by sound at the occipital region is small and quite variable. Its amplitude increases and its variability diminishes after coupling of sound and light. Also its form may resemble the potential evoked by light, especially in its rhythmic after-effects. In psychotic children auditory evoked responses are variable and small and remain so during the coupling of sound and light. Instead, these patients respond to the sound with a late slow wave, which is strong and generalized. It is particularly prominent during conditioning and resembles the slow waves which follow the visual evoked potentials in these autistic children. This slow wave can be experimentally reproduced in normal Ss by Psilocybine. It also resembles in certain ways the slow waves provoked by movement or its anticipation in normal Ss but it appears here during sensorial conditioning which requires no movement. We suspect that this slow wave may reflect a diffuse motor component in the perceptual and associative processes of these autistic children.     

Evoked Potential, Stimulus Intensity, and Drug Treatment in Hyperkinesis

The response of hyperkinetic (HK) boys to light flashes of four different intensities were measured with averaged visual evoked potential (AVEP). Latency, amplitude and stability data, including the slope of the regression of these measures with flash intensity, were obtained in initial and replicate samples of HK and control subjects. Repeated tests were done in attending and inattending conditions in a drug-free condition, and 1 hr. 1 week, and 5 weeks after treatment with dextroamphetamine. The data failed to support the hypotheses that HK children show small response to weak stimuli and normal to increased response to strong stimuli or “hyperaugmentation.” that they show increased response to weak stimuli or “reduction” when they are treated with dextroamphetamine, and that behavioral responsiveness In this drug is related to the degree of augmentation. The data also failed to support the hypothesis that detection of AVEP abnormalities in HK subjects is enhanced by testing in an attending condition. However, a few replicated findings were obtained which suggest that some AVEP factors other than the augmentation reduction measure may be related to both the degree of initial hyperactivity and the degree of decrease of hyperactivity with dextroamphetamine.     

Electrophysiological Correlates of Connotative Meaning in Healthy Children

The affective, connotative meaning of words can be statistically quantified by the semantic differential technique. Words that are located clearly on one of the three dimensions called “Evaluation”, “Potency”, and “Activity” were used as visual stimuli in a topographic event related potential study (ERP). Stimuli had been statistically defined in a group of 249 children (Skrandies, Jpn Psychol Res 53: 65–76, 2011). We investigated electrical brain activity in 19 healthy children with normal intelligence and reading skills between 11 and 15 years of age. Words that belonged to different semantic classes were presented at random on a monitor, and EEG was measured from 30 channels. Evoked potentials were computed offline for each semantic class. In the ERP data we observed significant effects of word class on component latency, field strength and topography. Similar as with adult subjects such effects occurred at small latency of about 115 ms after word presentation. The language-evoked components in children were similar but not identical to those reported previously for various groups of adults. Our data show that visually evoked brain activity is modulated by connotative meaning of the stimuli at early processing stages not only in adults but also in children.     

Influence of Total Sleep Deprivation on Event-Related Potentials in Man

The contingent negative variation (CNV) can be spontaneously followed in psychiatric patients by a postimperative negative variation (PINV), and also in normal subjects who have undergone sufficiently intense interference during the CNV paradigm. Our hypothesis was that sleep deprivation could facilitate the induction of a spontaneous PINV which would reflect a transient psychophysiological perturbation. The present experiment investigates the influence of total sleep deprivation on event-related potentials (PINV, CNV, auditory evoked potential), behavioral performance (reaction time), and autonomic response (heart rate). Nineteen subjects participated in the experiment. The subjects were studied before and after 2 consecutive nights of total sleep deprivation. The event-related potentials resulted from the summation of 16 trials. The warning stimulus (tone burst) was followed 1.5 sec later by an imperative stimulus (continuous tone) which was stopped by the subject. After the deprivation, 6 subjects underwent the CNV paradigm with interference. None of the subjects showed a PINV after sleep deprivation either spontaneously or with an interference which had induced it under non-deprived conditions. The CNV and auditory evoked potential (AEP) amplitudes were reduced after the deprivation whereas AEP latencies increased. The unobtainable PINV after sleep deprivation and the low CNV amplitude could suggest a common neurophysiological origin for these two slow potentials.