Effects of the common cold on mood, psychomotor performance, the encoding of new information, speed of working memory and semantic processing

Previous research has shown that people with the common cold report a more negative mood and psychomotor slowing. Recent research suggests that memory speed may also be impaired. This was examined in the study reported here. A prospective design was used and all participants (N=200; half male, half female; mean age 21years, range 18-30years) carried out a baseline session when healthy. The test battery involved mood rating, simple and choice reaction time, verbal reasoning and semantic processing. Volunteers returned when they developed an upper respiratory tract illness (URTI) and repeated the test battery. If they remained healthy they were recalled as a control. One hundred and eighty-nine participants completed the study and 48 developed URTIs and 141 were in the healthy control group. Symptoms and signs suggested that those who were ill had colds rather than influenza. The results showed that those with colds reported lower alertness, a more negative mood, and psychomotor slowing. They were also slower at encoding new information and slower on the verbal reasoning and semantic processing tasks. The magnitude of the mood changes associated with being ill were correlated with symptom severity. The performance changes were not correlated with symptom severity, sleep duration or mood changes. Further research is now needed to elucidate the underlying mechanisms of the behavioral malaise associated with URTIs.     

Effects of melatonin on human mood and performance

The function of melatonin, a hormone secreted by the pineal gland primarily at night, has not been definitively established in humans. To determine if pharmacologic doses of melatonin had any behavioral effects it was administered acutely to 14 healthy men. Their mood, performance, memory and visual sensitivity were assessed. Plasma melatonin concentration was assayed as well. Melatonin significantly decreased self-reported alertness and increased sleepiness as measured by the Profile of Mood States and the Stanford Sleepiness Scale self-report mood questionnaires. The effects were brief. Melatonin also affected performance, slowing choice—reaction time but concurrently decreasing errors of commission. Sustained fine motor performance was not impaired after melatonin administration nor were the tests of memory and visual sensitivity that were administered. It is concluded that melatonin, administered orally in pharmacological quantities, has significant but short acting sedative-like properties.     

Effects of anti-histaminic and anti-cholinergic substances on human thermoregulation during cold provocation

The roles of histaminergic and cholinergic neuron systems in the regulation of body temperature have been studied almost exclusively in animals. Recently, we have found that motion sickness, i.e. a condition where hippocampal cholinergic mismatch signals induce a release of histamine in the vomiting centre, accelerates the decline in body temperature in men during exposure to cold. In the present study we measured the thermoregulatory effects of two substances commonly used against motion sickness, i.e. the histamine (H1) receptor blocker dimenhydrinate (DMH) and the muscarine receptor blocker scopolamine (SCOP). In three trials, control (CN), DMH and SCOP, 10 male subjects were immersed in 15 °C water for a maximum of 90 min. The trials were separated by a minimum of three days and their order was alternated between subjects. In all trials the subject received, in a double blind fashion, a transdermal patch (SCOP or placebo) 12-14 h before immersion and a tablet (DMH or placebo) 1 h before immersion. Mean skin temperature, rectal temperature (T_rec), the difference in temperature between the non-immersed right forearm and 3rd finger of the right hand (T_ff), and oxygen uptake (VO₂) were recorded. The fall in T_rec was smaller in the DMH than in the CN and SCOP conditions. The recordings of T_ff and VO₂ suggest that SCOP attenuates peripheral vasoconstriction while DMH increases shivering thermogenesis. Notably, thermal discomfort was reduced in the SCOP condition. Findings are thoroughly discussed in the context of animal studies on the neuropharmacology and neurophysiology of thermoregulation and motion sickness.     

Selective effects of colds and influenza on human performance efficiency: a critical appraisal.

This paper provides an appraisal of the results published from the MRC Common Cold Unit on human performance efficiency during minor upper respiratory tract infection, i.e., colds and influenza. Despite strict controls employed in the methods of data collection, the robustness of the results and some of the conclusions drawn are questioned. In particular, the claim that colds and influenza lead to selective (and different) effects is criticised as being based on incomplete data. The lack of replication, the small sample sizes, possible response biases and use of controls are considered. Overall, it is argued that there are insufficient data to provide conclusive evidence for selective effects and that over-generalisation from such studies can be misleading.     

Exploring the after-effects of theta burst magnetic stimulation on the human motor cortex: a functional imaging study

Theta burst stimulation (TBS) is a protocol of subthreshold repetitive transcranial magnetic stimulation (rTMS) inducing changes in cortical excitability. From functional imaging studies with conventional subthreshold rTMS protocols, it remains unclear what type of modulation occurs (direction and dependency to neural activity) and whether putative effects are bound to unspecific changes in cerebral perfusion or require a functional challenge. In a within-subjects (n = 17) repeated measurement design including real TBS and a control session without stimulation, we examined neural activation in a choice-reaction task after application of intermittent TBS, a protocol, which enhances cortical excitability over the left motor cortex (M1). Brain activity was monitored by blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging interleaved with measuring regional cerebral blood flow (rCBF) at rest using MR-based perfusion imaging. On a separate day, TMS-induced compound muscle action potentials (cMAPs) amplitude of the right hand was measured after excitatory TBS. Compared to control, a significant decrease in BOLD signal due to right hand motor activity during the choice-reaction task was observed mainly in the stimulated M1 and motor-related remote areas after stimulation. This decrease might represent a facilitating effect, because cMAPs amplitude increased upon TBS compared to control. No changes in rCBF at rest were observed. The data demonstrate that subthreshold intermittent TBS targets both the stimulated cortical area as well as remote areas. The facilitation changing the efficacy of neural signal transmission seems to be reflected by a BOLD signal decrease, whereas the network at rest does not appear to be affected.     

Effects of influenza vaccination and influenza illness on exacerbations in multiple sclerosis

Despite reports that influenza vaccination appears to be safe in multiple sclerosis there is uncertainty which patients may benefit from it. By using a questionnaire we compared the effects of influenza illness (1995–1996 season) and influenza vaccination (autumn of 1996) on neurologic symptoms in patients with multiple sclerosis registered in the Groningen Multiple Sclerosis Data Bank. No clinically relevant effects were reported in 53 patients with primary progressive multiple sclerosis, either following vaccination or the illness. In a group of 180 patients with relapsing multiple sclerosis, an exacerbation occurred within the following 6 weeks in 33% after influenza illness, whereas it occurred in only 5% after vaccination. The exacerbation rate following influenza illness was significantly higher regardless of whether patients were essentially restricted to wheelchair or not. Because of a substantial greater risk of relapse after influenza illness than after vaccination, annual influenza vaccination should be offered routinely to all patients with relapsing multiple sclerosis.     

Effects of zaleplon or triazolam with or without ethanol on human performance

Objectives and background: Given that non-selective γ-aminobutyric acid (GABA) agonist hypnotics impair performance and potentiate the disruptive effects of ethanol, this study was done to determine the performance-impairing and ethanol-potentiating effects of zaleplon, a new selective GABA agonist hypnotic.Methods: Eighteen healthy men (12) and women (six), 31.5±5.6 years old, were studied. Each underwent six treatments of 2 days in duration, presented in a Latin square design with 2–12 recovery days between. The treatments were: placebo–placebo; placebo–ethanol; triazolam–placebo; triazolam–ethanol; zaleplon–placebo; and zaleplon–ethanol; with triazolam (0.25 mg) or placebo administered at 08:30 h, zaleplon (10 mg) or placebo at 09:00 h, and ethanol (0.75 g/kg) or placebo consumed from 09:30 h. Performance tests were completed each day at 10:30, 12:00 and 14:30 h.Results: Breath ethanol concentration (BrEC), tested 0.5, 2.0, 4.5 and 6 h post consumption, did not differ among treatments and peaked at 0.052%, declining to 0.037, 0.009 and 0.001%. Triazolam with and without ethanol impaired digit symbol substitution, symbol copying, simple and complex reaction times and divided attention performance relative to placebo–placebo treatment. It did so consistently at 10:30 and 12:00 h, and less consistently at 14:30 h. Zaleplon without ethanol impaired only digit symbol substitution and divided attention tracking, and only at 10:30 h. Zaleplon with ethanol impaired most measures at 10:30 and 12:00 h, but not at 14:30 h. Zaleplon without ethanol consistently differed from triazolam without ethanol in the extent of performance impairment. Zaleplon with ethanol began to differ from triazolam with ethanol in performance impairment on the 12:00 and 14:30 h test sessions. Ethanol itself impaired most measures at 10:30 h, fewer at 12:00 h and none at 14:30 h. All active drug treatments increased self-rated sleepiness compared with placebo–placebo. Triazolam without ethanol produced greater self-rated sleepiness than zaleplon without ethanol. The addition of ethanol to both drugs generally produced comparable levels of self-rated sleepiness.Conclusions: In an absolute sense, zaleplon produced less performance impairment and a shorter period of ethanol potentiation than triazolam.     

Effects of cold stress on early and late stimulus gating

The P50 component of the event-related potential (ERP) mainly reflects early pre-attentional processing. Along with P50, the N100 component and mismatch negativity (MMN) were postulated to represent a complex multistage and multi-component gating system. If some variable threshold or gating is exceeded by the MMN signal, the MMN is often followed by a relatively sharp fronto-central positive wave, the P3a component, which reflects an attentional switch to an environmental change. The P50 was shown to be affected by mental and cold stress, and the P3a amplitude was shown to be increased by the anticipation of threat. The aim of this study is to examine concurrently the early and late ERP indices of gating during acute stress. The ERPs to auditory stimuli in a passive oddball paradigm were recorded in 15 normal subjects during the cold pressor test and a control condition. The cold pressor test diminished P50 gating, increased N100 amplitude, elicited P3a responses and had no significant effect on MMN. Transient stress could impair early sensory gating and the ability to ignore irrelevant information that can cause passive attention switches indexed by the P3a component.     

Effects of cold adaptation and starvation on sciatic nerve fibers in the frog

The conditions under which frogs are kept prior to experimentation were found to have a measurable effect on peripheral nerve structure. Frogs kept for 12 weeks at 4 degree C had markedly shrunken sciatic nerve fibers compared with frogs kept at 19 degrees C. Intermediate fiber shrinkage was found for frogs kept at 19 degrees C without feeding. Counts of neurofilaments and microtubules showed that fiber shrinkage was from a preferential loss of filaments, indicating cold- or starvation-induced atrophy of the axon's cyto-skeleton. This effect, however, was superimposed with additional osmotic axonal shrinkage, causing filament densities to increase per area. There were no changes in myelin sheath thickness due to cold adaptation or fasting.     

Effects of resistance training on force steadiness and common drive

The purpose of this study was to investigate the influence of an 8-week resistance training program on force steadiness and common drive for the vastus lateralis muscle. Eight untrained men performed a resistance training program. Before the program and at the end of each week, the subjects performed a trapezoid isometric muscle action of the leg extensors, and bipolar surface electromyographic signals were recorded from the vastus lateralis. The signals were decomposed into action potential trains that were cross-correlated to measure common drive. Force steadiness was quantified as the standard deviation of force during the constant-force portion of the trapezoid muscle action. The training program did not consistently affect force steadiness or common drive for any of the subjects. Although future studies are needed with different muscles and training programs, changes in the overall motor control scheme are not likely with resistance training.     

Effects of fatigue on intermuscular common drive to the quadriceps femoris

ABSTRACT The purpose of this investigation was to examine intermuscular common drive to motor units in the vastus lateralis and vastus medialis during isometric contractions of the leg extensors. A secondary purpose was to investigate the effects of fatigue on the common drive. Fourteen healthy subjects (mean ± SD, age?=?21.7 ± 1.5?years) volunteered to perform two separate isometric contractions of the leg extensors at 50% of the maximum voluntary contraction (MVC). These contractions were performed before (PRE) and immediately after (POST) a fatigue protocol of 10, 10?s isometric MVCs with 10?s of rest in between (i.e., 10?s on, 10?s off). During the PRE and POST isometric contractions, surface electromyographic (EMG) signals were detected from the vastus lateralis and vastus medialis and decomposed into individual motor unit action potential trains. A mean firing rate curve was then calculated for each motor unit, and the curves for the vastus lateralis were cross-correlated with those from the vastus medialis. The results showed that the average peak cross-correlation coefficients were always between 0.39 and 0.55, with coefficients for individual motor unit comparisons occasionally as high as 0.93. However, these coefficients were not affected by fatigue. These findings demonstrated a significant level of intermuscular common drive that was generally unaffected by fatigue.     

Effects of acute intravenous cocaine on cardiovascular function, human learning, and performance in cocaine addicts

Continuous non-invasive cardiovascular monitoring in eight healthy cocaine addicts receiving intravenous cocaine (0.325 mg/kg or 0.650 mg/kg) or placebo in double-blind, randomized, cross-over fashion demonstrated significant dose-dependent increases in pulse and mean arterial pressure following cocaine. Pulse and mean arterial pressure peaked 5 min post-cocaine injection and maximal response was sustained for a further 15 min and 35 min afterwards, respectively. Cocaine administration had no significant effect on peripheral oxygen saturation, and no clinically significant abnormalities of rhythm or conduction were seen on the electrocardiogram. These doses and method of single-dose intravenous cocaine administration, and our procedures for cardiovascular monitoring, appear relatively safe for laboratory studies of healthy cocaine addicts with no pre-existing cardiovascular disease. In addition, cocaine-taking (0.325 mg/kg i.v. and 0.650 mg/kg i.v.) was associated with enhanced attention (i.e. increased numbers of correct responses on the Rapid Visual Information Processing Task), but the trend towards reduced reaction time did not achieve statistical significance. Cocaine-taking resulted in a small but statistically insignificant improvement in learning on the Digit Symbol Substitution Task. These results suggest that cocaine-taking in rested subjects is associated with some cognitive enhancement.