Search PubMed⌕ Search

Biomedical subjects

V J Knott

Publications and source records attributed to V J Knott.

At least 37 records · Page 2Linked to original sources
PubMed1990

Neuroelectrical activity related to panic disorder.

1. Quantitative electroencephalographic activity (EEG), together with bioelectric measures of the peripheral nervous system, provide us with unique non-invasive tools for investigating neurobiological issues relating to panic disorder. 2. During recordings of non-panic states, patients with panic disorder exhibit a desynchrony in autonomic vs. somatic arousal levels and also display significant EEG correlations with self-reported anxiety which are not apparent in control subjects. 3. Recordings concomitant with self-reported anxiety/panic during lactate infusions are associated with increased autonomic and somatic arousal and a paradoxical increase in slow wave EEG activity. 4. EEG recordings throughout a lactate challenge indicate that slow wave activity associated with panic does not appear to be characterized by an abrupt, sudden onset but tends to increase gradually throughout the infusion, a finding which is in disaccord with the 'spontaneity' view of panic.

Anxiety Disorders↗
PubMed1989

Effects of low-yield cigarettes on electroencephalographic dynamics.

Previous research had indicated that the smoking of medium tar and nicotine (T/N) yield cigarettes produced a psychostimulant action on electroencephalographic (EEG) activity which was apparent after a single cigarette and was evident as early as the fourth puff. The present study adopted the identical smoking and recording procedure to examine whether low-T/N yield cigarettes produced qualitatively similar EEG profiles as previously observed with medium-yield cigarettes. Although the results indicated similarities in post-smoking EEG profiles of low- and medium-yield cigarettes, discrepancies with several EEG components and temporal (puff-by-puff) EEG features suggested that low-yield cigarettes may exert less impact on brain electric activity. The results are discussed in relation to motivational theories of smoking behavior.

Adolescent↗
PubMed1989

Brain electrical imaging the dose-response effects of cigarette smoking.

Quantitative regional electroencephalographic (EEG) effects of cigarette smoking were examined within a repeated measures design which assessed, and topographically displayed, changes in power spectral estimates resulting from the smoking of low, medium and high tar/nicotine (T/N) yield cigarettes. Although intercigarette yield comparisons revealed no significant EEG differences between yields, comparison of the effects of smoking each yield with sham smoking indicated the presence of a qualitative dose-response effect whereby increasing T/N yields resulted in a progressive posterior-to-anterior spreading of significant relative power changes within both theta and alpha frequency bands. These exploratory findings are discussed in relation to smoking maintenance and working hypotheses are formulated for future testing.

Adult↗
PubMed1988

Neuropsychophysiological correlates of lactate-induced panic.

1. One of the simplest and most direct applications of neuropsychophysiological techniques is to anxiety disorders. 2. The physiological changes accompanying the lactate induction of panic appear, for most response systems, to be similar to those found spontaneously in anxious patients and are characteristic of a state of hyperarousal. 3. Patients vulnerable to lactate-induced panic exhibit higher than normal pre-panic autonomic activity, elevated autonomic-somatic activity during lactate-induced panic and an EEG response to provoked panic which appears to be comprised of a "paradoxical" shift towards slow wave delta activity and an altered brainstem evoked response. 4. Additional studies are warranted to determine the relationship of these physiological changes to the triggering of panic and preliminary attempts in this direction are discussed.

Anxiety↗
PubMed1988

Dynamic EEG changes during cigarette smoking.

Electroencephalograms were monitored before, during and after smoking a single cigarette. Quantitative analysis indicated that smoking produced a characteristic psychostimulant profile involving power reductions in delta and theta and increases in both alpha power and peak alpha frequency. Puff-by-puff analysis yielded similar patterns with the effects emerging by the fourth puff. Delta reductions were evident during the act of puffing and following inhalation. The results are discussed in relation to motivational theories of smoking.

Adult↗
PubMed1987

Electrophysiological and behavioral correlates of psychomotor responsivity in depression.

Psychomotor retardation is a frequently observed clinical feature of depressive states. This study attempted to assess the relationship between response slowness and central nervous system (CNS) activity by examining cortical evoked potentials (EPs) during psychomotor task performance. Patients consisted of 21 women who met Research Diagnostic Criteria (RDC) and exhibited a minimum Hamilton Rating Scale for Depression score of 18 at the end of a drug washout period, the scheduled time of testing. The same number of normal women with no history of psychiatric illness were employed as controls. Cortical EPs from Cz and integrated electromyogram (EMG) from the dominant forearm extensor were recorded and time-locked to warning and imperative stimuli of a standard, two-choice, fixed foreperiod reaction time (RT) task, which yielded behavioral measures of decision time (DT) and movement time (MT). Analysis focused on behavioral RTs, latency and amplitudes of EMG, sensory and slow cortical (CNV) EPs, and measures of input time (IPT), central processing time (CPT), and motor execution time (MET), derived from combinations of EP and EMG peak latencies. Patients exhibited slower DT and MT response times, delayed EMG latencies, and attenuated EP amplitudes. The derived CPT measure was also significantly longer in patients. These findings support the view that a central dysfunction is implicated in psychomotor retardation, and the results are discussed in relation to information processing theory.

Adult↗
PubMed1987

Computerized EEG correlates of depression and antidepressant treatment.

Quantitative EEG was used to examine: differences between non-medicated depressives and normal controls; chronic effects of antidepressant drug treatment. Spectral analysis of cortical EEG activity revealed: significant group differences in slow and fast wave activity and significant differences in hemispheric asymmetry; limited effects of antidepressants which were restricted to slow wave activity. Group differences are supportive of cortical disactivation of the right-hemisphere in depressive disorders and the limited drug-EEG effects in depressives argue for additional studies on multi-lead oriented pharmaco-EEG profiles in psychiatric populations.

1-Naphthylamine↗
PubMed1987

Acute effects of tobacco on human brain stem evoked potentials.

Reports of tobacco-induced electrocortical activation have frequently indicated that this effect is mediated via nicotine's action on sub-cortical structures. This study focused on human brain stem involvement by examining the acute effects of tobacco smoking on brain stem auditory potentials (BSAEPs). Twelve regular smokers were tested on two separate sessions involving sham or real smoking. On each session, BSAEPs were recorded during a baseline period and immediately after smoking. BSAEPs, recorded from Cz, were elicited by presentation of 1,000 monaural, rare fraction click stimuli. Latency and amplitudes of peak components I, III and V were assessed and analysed. No significant effects were observed for latency measures or for amplitudes of peaks I and III. A significant effect was observed for peak V with tobacco resulting in larger amplitudes relative to sham smoking. Peak V reflects activity from upper pontine-lower midbrain sites and this tobacco-peak V finding is discussed in relation to arousal and information processing theories of smoking.

Adult↗
PubMed1986

Tobacco effects on cortical evoked potentials to task stimuli.

Cortical evoked potentials (EP) were investigated in a group of female smokers in separate smoking and non-smoking sessions. In a constant-fore-period S1-S2 reaction time paradigm, EPs were averaged separately to auditory warning (S1) stimuli and visual imperative (S2) stimuli under 4 conditions: (a) a single-choice S1-S2 sequence with no auditory distraction task; (b) a single-choice S1-S2 sequence with concomitant auditory distraction task; (c) a four-choice S1-S2 sequence with no auditory distraction task; (d) a four-choice S1-S2 sequence with concomitant auditory distraction task. Two individual EP peaks, N1 and P2 and one peak-to-peak measure, N1-P2, were involved in amplitude analysis of S1 and S2 stimuli. Tobacco significantly improved the decision time (DT) component of reaction time and increased N1 amplitudes to S1 stimuli. Tobacco also interacted with task complexity to reduce P2 amplitudes to S1. No significant tobacco effects were observed with EPs to S2. The results are discussed in relation to improved attention and information processing.

Adult↗
PubMed1986

Effects of lactate-induced panic attacks on brain stem auditory evoked potentials.

As the clinical symptomatology of panic attacks may be conceivably related to abnormal brain stem activity, the present study examined the effect of lactate-precipitated panic on brain stem auditory evoked potentials (BSAEPs). The subjects were 27 patients who met DSM-III criteria for panic disorder (Pd), agoraphobia with panic attacks (AgPa) or agoraphobia (Ag). Following drug washout, patients were tested in two separate sessions, in a double-blind randomised controlled design in which each session involved two sequentially ordered BSAEP collection periods - a baseline period with no infusion followed by an intravenous infusion of 5% dextrose in water or 1.0 M sodium lactate (5 ml/kg in 5% dextrose/water) over a 20-min period. Of the 27 patients, 17 were clear responders, reporting panic attacks and self-report changes under lactate similar to those occurring during spontaneous panic. Of the remaining 10 patients, 6 were pseudo-responders, reporting panic symptoms under both dextrose and lactate, and 4 were non-responders. In the clear responders, lactate did not alter electrical events of the BSAEP, but further analysis within the clear responders, comparing AgPa patients with Pd patients, yielded a significant effect with lactate resulting in a prolonged III-V inter-peak interval in the AgPa group. It is suggested that the increased III-V interval in the AgPa group may be reflective of hyperactivity of brain stem noradrenergic nuclei.

Anxiety↗
PubMed1985

Tobacco effects on cortical evoked potentials to distracting stimuli.

In a group of female smokers, cortical evoked potentials (EP) were averaged to low and high intensity auditory stimuli which were presented during both task and non-task conditions and in separate smoking and non-smoking sessions. Four individual EP peaks, P1,N1,P2,N2 and 3 peak-to-peak measures, P1-N2, N1-P2, N2-P2, were involved in amplitude analysis. Tobacco significantly interacted with intensity and task condition to produce both increases (P1, N1) and decreases (P2, P2-N2) in amplitudes of EP peaks. The results are discussed in relation to arousal and information processing.

Adult↗
PubMed1985

Effects of tobacco and distraction on sensory and slow cortical evoked potentials during task performance.

Sensory and slow cortical evoked potentials (EP) of female smokers were investigated under two conditions in separate sham and real smoking sessions: a non-distraction (ND) condition consisting of a constant fore-period S1-S2, i.e., a single-choice reaction time situation with a tone (S1)/light (S2) key press sequence, and a task distraction (TD) condition identical to ND with the addition of a short-term memory task consisting of four letters presented within the S1-S2 interval with the requirement that subjects repeat after key press to the light. Two individual EP peaks, N1 and P2, were involved in the amplitude analysis of S1 and S2 stimuli; in addition, the amplitude of the slow contingent negative variation (CNV) developing between S1 and S2 was analyzed. Tobacco significantly altered the amplitude of P2 in response to S1 and CNV amplitudes depending on the pre-experimental expired air carbon monoxide (CO) levels of the smokers. Smokers exhibiting low pre-experimental CO levels evidenced tobacco-induced P2 reductions and CNV increments during the ND condition while subjects exhibiting high pre-experimental CO levels displayed similar cortical changes but in the TD conditions. The results are discussed in relation to the role of nicotine and to improved attention and information processing.

Adult↗
PubMed1985

Relaxation, noise-induced stress, and autonomic responsivity in male alcoholics and normal controls.

Skin conductance and heart rate activity were monitored in male alcoholics and normal controls before, during, and after the presentation of high-intensity (100 db) white noise. Analysis of nonstressful, pre- and postnoise periods indicated a relatively nonlabile pattern characterizing alcoholics as they exhibited lower skin conductance levels than normals and showed no changes in activity either within or between resting sessions. A similar pattern was observed in response to noise-induced stress as alcoholics exhibited significantly smaller changes in skin conductance and heart rate activity.

Adult↗
PubMed1984

Noise and task induced distraction effects on information processing: sex differences in smokers and non-smokers.

Choice reaction time performance was monitored in male and female smokers and nonsmokers during the separate and combined presentation of noise- and task-induced distraction. Behavioral measures of decision time and movement time were examined together with response errors. Relative to female nonsmokers, female smokers exhibited significantly slower decision times during both separate and combined presentation of distractors. Female smokers also showed significantly longer decision times than male smokers during task-induced distraction. Significant differences were also observed with response errors, with task and combined noise- and task-induced distraction resulting in greater impairment in female smokers. The results are supportive of a relative central information processing deficit in female smokers and discussion is focused on the role of attentional processes.

Adult↗
PubMed1984

Electrodermal activity during aversive stimulation: sex differences in smokers and non-smokers.

Skin conductance activity was monitored in male and female smokers and non-smokers during repeated presentation of high intensity auditory stimuli. Smokers, and, in particular, female smokers, exhibited significantly higher resting skin conductance levels and significantly larger skin conductance responses. The results are discussed in relation to "stress-reduction" smoking.

Acoustic Stimulation↗
PubMed1984

Heart rate responsivity to a high intensity auditory stimulus: a comparison of male alcoholics and normal controls.

Previous research has demonstrated the presence of two heart rate acceleration responses to high intensity auditory stimuli. Both responses, the short latency acceleration peaking at 3-4 beats poststimulus and the long latency acceleration peaking at approximately 30-35 sec poststimulus, have been related to defensive responding to aversive stimuli and thus were employed to examine a stress-related hypothesis of alcoholism. A group of male alcoholics (n = 15) and a group of male controls (m = 15) received a 100 dB tone while heart rate was recorded. While both groups exhibited equal amplitudes on the short latency component, alcoholics exhibited a slower initial response time and relative to normal controls, failed to exhibit a secondary acceleration response. The results are discussed with respect to previous findings of hypo-responsivity observed in alcoholics.

Acoustic Stimulation↗