Age-related changes in cognitive ERPs of attenuation

This investigation explored developmental changes in passive and effortful components of ERPs associated with a visual attention task in children, adolescents, and adults. The task was a 'go-go' version of a continuous performance task, coupled with a passive attending phase in which the subjects merely watched the stimuli of the task. The three age groups featured a constellation of ERP components that shared the same general morphological appearance and distribution, but differences were seen with respect to latencies and amplitudes. Consistent with other studies, there was an inverse relationship with respect to age and peak latencies of the major passive and effortful components. With respect to peak amplitudes, however, the most impressive changes with age were observed in the passive processing components. For example, the P150 and P250 components presented greater amplitudes in children, whereas the N200 component presented its greatest amplitude in adults. While passive in the sense that their appearances were independent of the 'decision-making' process, these components were found to be upwardly adjustable by effort. The late positive component was found to be a combination of a passive P350 and an effortful P450. The P350 component was judged to be largely passive in character as it was well developed in subjects of all age groups when passively attending to the visual stimuli. There was no marked amplitude difference between the child and adult P450 components, but the components peaked in amplitude later in the children. Finally, the children's ERPs featured a distinct frontal negativity (FN) that was present in the Passive phase, but greatly enhanced during the Effortful phase. This study, as have many others, showed that there are reliable developmental changes in the components of visual ERPs. Therefore, the characteristics of the various components of cognitive ERPs may be effective markers of neurodevelopmental status, especially of those neuronal systems vital to attentional processing and effort regulation.

Enhancement of attention processing by Kantroll in healthy humans: a pilot study

This is the first report in humans of the effects of daily ingestion of a specific amino acid mixture, Kantroll, on cognitive event-related potentials (ERPs) associated with performance. Cognitive ERPs were generated by two computerized visual attention tasks, the Spatial Orientation Task (SOT) and Contingent Continuous Performance Task (CCPT), in normal young adult volunteers, where each subject acted as his own control for testing before and after 28-30 days of amino acid ingestion. A statistically significant amplitude enhancement of the P300 component of the ERPs was seen after Kantroll for both tasks, as well as improvement with respect to cognitive processing speeds. The enhancement of neurophysiologic function observed in this study on normal controls is consistent with the facilitation of recovery of individuals with RDS (i.e., substance use disorder, ADHD, carbohydrate bingeing) following the ingestion of the amino acid supplement, Kantroll, and warrants additional placebo-controlled, double-blind, studies to confirm and extend these results.

Topographical analyses of attention disorders of childhood

Cognitive ERPs and EEG spectral differences were compared in three groups of children: nonreferred controls, those with a dominant hyperactivity/impulsivity factor (ADHD-Im), and those with a dominant inattentive factor (ADHD-Ia). The results from the ERP analyses indicated that the P250, P350, and P500 components differed between the groups. The most marked differences were seen with respect to the amplitude of the P500 components. In addition, the topographic foci of the P500 components for the CON and ADHD-Im groups were symmetrical, but the ADHD-Ia group featured P250 and P350 components that were biased away from the right hemisphere. Nevertheless, the P500 was found to be an effective discriminator between the groups. The combined spectral and ERP results suggest that the attention disordered children have difficulty adjusting their level of physiological arousal, and are defective with respect to controlled (or effortful) processing.

The gold foil electrode in pattern electroretinography

A recent study found that the gold foil electrode produces large pattern electroretinogram amplitudes, but the test-retest reliability was low. In a three-center study, we observed that 90% of 29 patients who were tested with gold foil electrodes used three times appeared to have markedly lower amplitudes than when tested with new electrodes during the same session. Across study centers, the mean of the new electrode recordings was 3.78 microV (standard deviation, 1.13 microV), versus 2.93 microV (1.29 microV) for used electrodes. This 0.85-microV reduction (22%) was statistically significant (F = 7.10 p = 0.01). Electrodes used three times demonstrated an average change in the coefficient of variation of 14% (standard deviation/mean = coefficient of variation; new, 1.13/3.78 = 30%; used, 1.29/2.93 = 44%). Two of the study sites (Houston/Indianapolis) conducted test-retest pattern electroretinograms on a total of 18 patients and found the mean evoked potential to be 3.55 microV with new electrodes and 2.82 microV with used electrodes. The coefficient of variation for the test-retest data was 30% and 47% for new and used electrodes, respectively. Light microscopy showed small cracks on the surface of the electrode, with the number and configuration of the cracks varying in each electrode. The presence of cracks is further complicated by their proximity to the tear film. These sources of variation can result in significantly different impedances. We propose that constant flexion, as a result of patient blinking, causes cracks in the thin gold surface of the electrode. Used electrodes will produce lower pattern electroretinogram amplitudes and poor test-retest reliability.(ABSTRACT TRUNCATED AT 250 WORDS)

The pattern visual-evoked potential in former preterm infants with retinopathy of prematurity

PURPOSE

Flash and pattern visual-evoked potentials (VEPs) were recorded in 89 former preterm infants (< or = 1500 g birth weight), in whom retinopathy of prematurity (ROP) developed that spontaneously regressed without macular detachment (stages 2-4a).

METHODS

Linear and stepwise regression analyses were performed to determine the correlations between transient pattern-reversal P1 VEP latency (n = 154 eyes) at a mean of 7.2 years (median, 6.9 years) postnatal age using a check size nominally equivalent to 20/100 (30 minutes) and the following nine parameters: three immaturity parameters (gestational age at birth, birth weight, and ROP zone at 1 month postnatal age); one postnatal insults parameter (worst ROP stage); two structural outcome parameters (macular ectopia and vessel traction); one functional outcome parameter (visual acuity); and two methodological parameters (postnatal age at VEP testing and VEP amplitude).

RESULTS

Linear regression analyses, with P1 VEP latency as a dependent variable, identified the worst ROP stage (r = +0.42; P < 0.0001), macular ectopia (r = +0.42; P < 0.0001), visual acuity (r = -0.40; P < 0.0001), and vessel traction (r = +0.35; P < 0.0001) as significant correlates. Stepwise regression analysis demonstrated that worst ROP stage and macular ectopia accounted for 18% and 4% of the cumulative variance, respectively.

CONCLUSIONS

P1 VEP latency correlates with postnatal insults, structural outcome, and functional outcome parameters in former preterms in whom ROP developed that spontaneously regressed without macular detachment. A permanent arrest in the development of the macula and/or prolonged traction on the incompletely developed macula may alter VEPs.

Evidence of temporal lobe activation by discriminative spatial orientation

The results from this spatial orientation, or cue priming, investigation found that targets presented to the contralateral visual fields differentially activated the temporal zones. For instance, stimulation within the right visual field lead to activation of the left temporal zones, as indexed by the relative prominence of the association negativity, N2. The converse was true for left visual field stimulation. For both visual field stimulation, the N2 component also showed an occipital and parietal distribution. The P300 component, which is presumed to be modulated by medial temporal lobe structures, showed the classic centroparietal distribution. Somewhat surprisingly, differences between the primed (e.g., 'facilitated') and 'normal' conditions for the N2 component appeared restricted to the occipital zones. Here, the significant variable was the N2 peak latency. Hence, the priming cue appears to quicken the maximal development of the N2 processing component, preferentially over the occipital cortex, and this may partially explain the faster reaction times in the 'facilitated' conditions for both visual fields.

The effect of optical defocus on the pattern electroretinogram in normal subjects and patients with Alzheimer's disease

The pattern electroretinogram, thought to originate from the spatially sensitive inner retinal layers, was recorded in 16 patients with Alzheimer's disease and 16 age- and gender-matched control subjects under the following two test conditions: (1) optical defocus or inattention, without laser pointer, and (2) optical focus or attention, with laser pointer. By correcting for optical defocus with the laser pointer, control subjects increased their pattern electroretinogram amplitudes by 8% from a mean value of 2.65 microV (standard deviation, 1.12) to 2.87 microV (standard deviation, 0.93), whereas patients with Alzheimer's disease had a 19% increase in pattern electroretinogram amplitude from 2.20 microV (standard deviation, 0.86) to 2.62 microV (standard deviation, 0.64). By controlling for optical defocus, the coefficient of variation (standard deviation/mean) was reduced by 10% (from 42% to 32%) in normal subjects and by 14% (from 39% to 25%) in patients with Alzheimer's disease. A two-way analysis of variance (ANOVA) did not show a significant difference in amplitudes between populations, which indicates that the pattern electroretinogram may not be valuable in establishing an early diagnosis of Alzheimer's disease. In a second study conducted in 20 young, healthy normal subjects, plus lenses were used to defocus the checkerboard stimuli, before recording the pattern electroretinogram. We found that the pattern electroretinogram was extremely sensitive to optical defocusing such that the response amplitude decreased by 13% at 20/25 visual acuity and 19% at 20/30. Reduction of pattern electroretinogram amplitude caused by change in visual acuity is an independent source of artifact.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrode comparison in pattern electroretinography

In recent years, there has been great interest in recording the pattern electroretinogram (PERG) in glaucomatous and diabetic populations. The Dawson, Trick, and Litzkow thread electrode (DTLTE) and the gold foil electrode (GFE), commonly used for recording PERGs, were compared for variations in amplitude of response, test-retest variability, and patient comfort. Two study centers collected data on a total of 32 normal subjects. The subjects from the London center showed a slight (but not significant) preference for the DTLTE, and the Houston subjects also found the DTLTE to be significantly more comfortable (chi-square = 39, P less than 0.001). In both study groups, the GFE was found to produce a statistically larger amplitude of response than that obtained with the DTLTE. Significant differences were found regardless of the slow (transient, 3.1 Hz; F = 6.24; P = 0.0192) or fast (steady state, 8.3 Hz; F = 18.38; P = 0.0001) stimulus-presentation rate. Larger differences between the two electrodes occurred under steady-state conditions. Although there is no consensus as to the optimum recording conditions to obtain the subtle PERG, it appears the the GFE records larger responses than the DTLTE. However, test-retest data confirmed that the GFE records twice the amplitude of the DTLTE, and it also produced twice the variability (average percent difference over time for GFE, 15%; for DTLTE, 8%).

Auricular microelectrostimulation: naloxone-reversible attenuation of opiate abstinence syndrome

This study evaluated the effects in rats of very low amplitude (10 mu amp) charge-balanced 10-Hz stimulation delivered bilaterally to low impedance points on the outer ear. This microelectrostimulation markedly and significantly reduced the number of opiate abstinence signs observed following a week of continuous morphine infusion. This effect was prevented by subcutaneous injection of 3 mg/kg naloxone, suggesting that stimulation of endogenous opioid activity plays a major role in the actions of auricular microelectrostimulation.