Dominic Valentino

Comparison of QEEG and response accuracy in good vs poorer performers during a vigilance task

Subjects performed an auditory continuous performance test requiring them to detect targets in a series of letters presented at a rate of 2/s. 2-min samples of EEG were obtained from eight bipolar sites during a resting condition and during early and late (7-10 min) test performance. EEG power spectra from 27 subjects whose performance accuracy decreased between these latter periods (LoVig group) were compared with those from 27 subjects who maintained a constant level of performance (HiVig group). In both groups EEG power changed significantly between resting and test conditions for all frequency bands: beta power increased, especially in fronto-temporal and temporal left-hemisphere sites; alpha and posterior theta decreased; anterior theta and delta increased. Significant changes also were found between early and late test performance: anterior theta and delta power decreased in both groups; temporal beta power decreased in the LoVig group only, and is thus considered the best indicator of performance changes. Other differences found between groups were across conditions. The HiVig group had more anterior beta and less posterior alpha and theta than the LoVig group. EEG results are discussed in relation to an explanation of vigilance errors based on signal detection theory.

A guide for applying principal-components analysis and confirmatory factor analysis to quantitative electroencephalogram data

Principal-components analysis (PCA) has been used in quantitative electroencephalogram (qEEG) research to statistically reduce the dimensionality of the original qEEG measures to a smaller set of theoretically meaningful component variables. However, PCAs involving qEEG have frequently been performed with small sample sizes, producing solutions that are highly unstable. Moreover, solutions have not been independently confirmed using an independent sample and the more rigorous confirmatory factor analysis (CFA) procedure. This paper was intended to illustrate, by way of example, the process of applying PCA and CFA to qEEG data. Explicit decision rules pertaining to the application of PCA and CFA to qEEG are discussed. In the first of two experiments, PCAs were performed on qEEG measures collected from 102 healthy individuals as they performed an auditory continuous performance task. Component solutions were then validated in an independent sample of 106 healthy individuals using the CFA procedure. The results of this experiment confirmed the validity of an oblique, seven component solution. Measures of internal consistency and test-retest reliability for the seven component solution were high. These results support the use of qEEG data as a stable and valid measure of neurophysiological functioning. As measures of these neurophysiological processes are easily derived, they may prove useful in discriminating between and among clinical (neurological) and control populations. Future research directions are highlighted.

Validation of a right hemisphere vigilance system as measured by principal component and factor analyzed quantitative electroencephalogram

Arruda and colleagues [Arruda, J.E., Weiler, M.D., Valentino, D.A. et al., 1996. A guide for applying principal-component analysis and confirmatory factor analysis to qEEG data. Int. J. Psychophysiol. 23, 63-81.] recently described seven neurophysiological measures that were previously derived and confirmed using factor analytic procedures and the quantitative electroencephalogram (EEG) sampled from 208 normal controls during an auditory continuous performance test (CPT). The purpose of the present investigation was to further test the validity of these empirically derived measures by examining each measures relationship with CPT-related declines in performance. Participants were 48 right-handed men (n = 13) and women (n = 35) who reported being free of any neurological condition, birthing complications, or loss of consciousness greater than 2 min. After completing an eyes-closed resting condition, participants performed a 23-min CPT while both quantitative EEG and behavioral performance were measured at 45, 405, 765 and 1125 s into the CPT. Bipolar recordings were gathered using the International 10-20 system, from eight sites: frontal, fronto-temporal, temporal and temporal-occipital. Multivariate and follow-up univariate tests suggest the existence of a neurophysiological system located within the right temporal region that appears essential for the maintenance of a sustained attentional state. If confirmed, the further quantification of this neurocognitive system may prove useful as part of a clinical diagnostic workup.

Enhancement of morphine analgesia after acute and chronic haloperidol

Abstract In the male rats haloperidol pretreatment caused an enhancement of morphine analgesia. After chronic haloperidol the analgesia enhancing effect of haloperidol was observed up to 10 days after its discontinuation. No analgesia was present in the haloperidol treated rats not given morphine.

Attention tasks and EEG power spectra

The authors attempted to observe differences in alpha and beta hemispheric asymmetry during a task in which attention was directed toward input from the environment (intake task) as opposed to tasks that required that environmental events be excluded from the focus of attention (rejection tasks). In comparison to resting, both attention tasks caused a shift in alpha asymmetry ratios toward increased power on the right, with the greatest effect at temporal leads. The only significant difference between attention tasks was a finding of higher alpha power during intake than during rejection. Some characteristics of the EEG during attention indicate potential clinical utility.

Chronic desipramine attenuates morphine analgesia.

Two experiments were conducted to explore the effects of chronic antidepressant treatment on endogenous opioid systems. In the first study, mice received desipramine for 21 days, a regimen which down-regulates beta-adrenergic receptors [13]. Subsequently, hotplate jump latencies were measured after acute saline, morphine or naloxone, to test for dynamic changes in endogenous opioid systems. Chronic desipramine treatment resulted in a significant attenuation of morphine analgesia, but had no effect on latencies of saline and naloxone treated mice. In the second experiment, naltrexone or propranolol were given with desipramine for 21 days, in an attempt to block the development of subsensitivity to morphine. Naltrexone had no effect on desipramine attenuation of morphine analgesia. Propranolol given with desipramine slightly lowered jump latencies of acute saline controls, resulting in a significant analgetic effect of morphine. These data suggest that attenuation of morphine analgesia by chronic desipramine treatment may be mediated by actions on noradrenergic systems, rather than direct effects on opioid receptors.

Rhythmic oscillations in the performance of a sustained attention task

Attempts to sustain a narrow focus of attention over a long period of time are effortful and are punctuated by lapses. Most studies of sustained attention performance obscure the presence and pattern of lapses by reporting measures that are summed across the entire period of an individuals performance, or that are average scores for blocks of trials across many participants. In the present study we attempted to explore fluctuation in the attention of individual participants over the course of a vigilance task and to quantify its periodicity, if any exists. Normal university students listened to letters of the alphabet, arranged randomly and presented at a rate of 2 per second for 20 min. They were instructed to press a hand-held button when they detected a target (two consecutive identical letters). Continuous estimates of performance accuracy (correctly detected targets) at regularly spaced time intervals were created for each participant using a moving time window. The resulting functions were analyzed in order to detect and quantify periodicity using a Fast Fourier Transform (FFT). The most often observed rhythms for those participants with adequate FFT power congregated at 1–2 min, 4–7 min and greater than 10 min. Performance functions from 36 of the 40 subjects displayed at least two of these frequencies. Other studies have identified cycles in performance during similar vigilance challenges, but without particular rhythms or with no particular shared frequencies amongst participants. The possible sources of these fluctuations and the differences in the findings of these studies and the present study are discussed.

Measures of Variations in Performance During a Sustained Attention Task

In this study the authors developed and explored measures of short-term variations in accuracy on a test of sustained attention, a departure from traditional measures of average performance over long periods. The study participants were normal young adults, actively engaged in a continuous performance test (CPT). Both correct (hits) and incorrect (misses) responses to CPT targets appeared to aggregate in runs (2 or more consecutive hits or misses). Results of a Monte-Carlo procedure indicated that these runs were longer and fewer than would occur if hits and misses were randomly distributed. Average accuracy decreased between the first and second 5-min quarter of the test, then remained level. The length of hit runs followed the same pattern. However, other aspects of performance continued to change. The amount of time participants spent in miss runs began to increase significantly in the third quarter, and the frequency of miss runs did not increase until the fourth quarter. Explanations of these findings based upon changes in perceptual sensitivity or upon phasic increases in arousal caused by hits were rejected by further analysis. There was evidence that the length of miss runs was limited by a target-expectancy effect created by the specific parameters of our CPT. The authors conclude that measures of variations in performance reveal aspects of vigilance that are not tapped by traditional measures, and that factors that initiate, sustain and terminate both hit and miss runs are important targets of future research. Additional research is needed to determine whether or not the particular measures developed in this study may contribute to the understanding of attention problems in clinical populations.

Chronic DMI reduces thresholds for brain stimulation reward in the rat.

The authors sought a demonstration of the validity of brain stimulation reward (BSR) models of depression. It was predicted that chronic, but not acute antidepressant treatment would enhance BSR responding. Rats with medial forebrain bundle electrodes were separated into 4 groups that received either saline or desmethylimipramine at 5, 10, or 20 mg/kg daily. A rate-free, threshold measure that has not previously been employed in studies of BSR and antidepressants was used. BSR thresholds were monitored every 3rd day over a 9-day baseline period and an 18-day drug treatment period, and after 12 days of drug withdrawal. Groups did not differ from one another till the 15th and 18th day of drug treatment. The greatest effects were seen in the 10 and 20 mg groups. The 20 mg group returned to baseline after drug withdrawal, but the 10 mg group did not. The absolute size of the effect was considered to be small, leading the authors to speculate that antidepressants act on homeostatic mechanisms that stabilize BSR substrates, only indirectly enhancing transmission of the reward signal.

Attenuation of morphine analgesia by lesions of the preoptic forebrain region in the rat.

Abstract Latency to tail withdrawal from hot water was measured as a pain response before and after morphine injection in female rats. Morphine increased the withdrawal latency. Lesions in the preoptic forebrain region attenuated morphine analgesia.