Biomedical subjects

Marinus N Verbaten

Publications and source records attributed to Marinus N Verbaten.

12 recordsLinked to original sources

PubMed2003

Detection of visual change: mismatch or rareness?

How do we detect changes in our visual environment? By continuously comparing visual inputs to templates of experiences in the immediate past? Or by determining their rareness, how infrequently a visual event occurred previously? Recent results from event-related potentials have been interpreted in favour of the first hypothesis, as in the case of the auditory mismatch negativity. Here we demonstrate that rareness, rather than mismatch with a template, underlies visual change detection. Such rareness is detected through a dedicated mechanism in human visual cortex about 100 ms after the rare event occurs, reflected in the rareness-related negativity (RRN).

Adolescent↗

PubMed2003

Driving ability after acute and sub-chronic administration of levocetirizine and diphenhydramine: a randomized, double-blind, placebo-controlled trial.

RATIONALE: Sedation following antihistamine use poses a danger to ambulant patients involved in daily activities such as driving. OBJECTIVE: To investigate effects of levocetirizine (5 mg), diphenhydramine (50 mg), and placebo on driving ability during normal traffic. METHODS: Forty-eight healthy volunteers participated in a double-blind, placebo-controlled, randomized clinical trial. Treatments were administrated on days 1, 2, 3 and 4, exactly 1.5 h before the start of the standardized driving test (performed on day 1 and day 4). In the standardized driving test, subjects were instructed to drive with a steady lateral position, while maintaining a constant speed (95 km/h). Primary parameter was the standard deviation of lateral position (SDLP; cm). Statistical analyses were performed separately for day 1 and day 4, using analysis of variance and an equivalence test. Equivalence to placebo was evidenced if the 95% confidence interval lay between -2.6 cm and +2.6 cm. RESULTS: SDLP after levocetirizine was equivalent to placebo on both day 1 (-0.66 cm; +1.12 cm) and day 4 (-0.37 cm; +1.28 cm). In contrast, SDLP after diphenhydramine differed significantly from placebo on both day 1 ( P<0.0001) and day 4 ( P<0.0003). On day 1, the 95% confidence interval of diphenhydramine (+1.85 cm; +3.63 cm) was partially above the upper equivalence limit (+2.6 cm), indicating clinically relevant driving impairment. On day 4, however, the 95% confidence interval of diphenhydramine (+0.74 cm; +2.38 cm) was contained within the acceptance range. CONCLUSION: In contrast to diphenhydramine, driving performance was not significantly affected while using 5 mg levocetirizine once daily.

Adult↗

PubMed2003

Specific memory deficits in ecstasy users? The results of a meta-analysis.

A meta-analysis was carried out on the possible functional neurotoxic effects of ecstasy use in humans on verbal short-term memory (STM), verbal long-term memory (LTM), processing speed (RT) and % errors (attention). To that end studies were found on the effect of ecstasy that fulfilled the criteria for a meta-analysis (number of subjects, means and standard deviations of the dependent variables). Ten studies were included on STM, ten on LTM, eight on RT and eight on % errors (attention). In addition meta-regression analyses were carried out on the effect sizes with total lifetime ecstasy consumption (TLEC) as predictor. It was found that in all four meta-analyses the mean effect size (ES) was significant: ecstasy users had lower verbal STM and LTM scores, reacted slower and made more errors. The meta-regression coefficients were not significant, indicating no support for a linear relationship between the mean ES values and TLEC, leaving open the possibility for a stepwise relationship. Additional meta-analyses on ecstasy groups that did not differ in lifetime cannabis consumption showed that only the ES for LTM became insignificant. This suggests that ecstasy use does not decrease LTM, but the number of studies on which this conclusion is based was very low.

Attention↗

PubMed2003

Acute and subchronic effects of levocetirizine and diphenhydramine on memory functioning, psychomotor performance, and mood.

BACKGROUND: Central nervous system adverse effects, such as sedation, often accompany the use of first-generation antihistamines. These effects might interfere with memory functioning and psychomotor performance. Levocetirizine was recently introduced as a new antihistamine said to be free from sedative effects. OBJECTIVE: We sought to investigate the effects of levocetirizine (5 mg), diphenhydramine (50 mg), and placebo on memory and psychomotor performance after acute (day 1) and subchronic (day 4) daily administration in 48 healthy volunteers (24 men and 24 women). METHODS: This study was a double-blind, placebo-controlled, randomized clinical trial. Treatments were administrated on days 1, 2, 3, and 4, 3 hours before the start of the laboratory test battery (performed on days 1 and 4), comprising a word-learning test, the Sternberg Memory Scanning Test, a tracking test (easy and hard version), and a divided attention test (tracking and memory scanning simultaneously). Statistical analyses were performed separately for days 1 and 4 by using analysis of variance. RESULTS: On day 1, diphenhydramine significantly impaired tracking performance (easy: F(1,90) = 25.9, P <.0001; hard: F(1,90) = 20.5, P <.0001) and divided attention (tracking: F(1,90) = 23.8, P <.0001; memory scanning: F(1,90) = 22.0, P <.0001). Results on word-learning tests and Sternberg Memory Scanning Tests were not significantly impaired. On day 4, the effects of diphenhydramine did not reach significance. In contrast, on both days 1 and 4, levocetirizine did not significantly impair laboratory test performance. CONCLUSION: The results show that memory, attention, and tracking performance are unaffected after acute and subchronic administration of levocetirizine (5 mg), whereas diphenhydramine (50 mg) significantly affected divided attention and tracking after acute administration.

Acetates↗

PubMed2002

Alcohol hangover effects on memory functioning and vigilance performance after an evening of binge drinking.

The impairing effects on memory functioning after acute alcohol intoxication in healthy volunteers and after chronic use in alcoholics are well established. However, research determining the next-morning effects of a single episode of binge drinking on memory functioning is scarce. A total of 48 healthy volunteers participated in a single-blind study comprising an evening (baseline) session, followed by a treatment administration (ethanol 1.4 g/kg or placebo), and a morning session. Memory was tested with a word-learning test (including immediate and delayed recall, and recognition). Further, a 45-min Mackworth clock test for measuring vigilance was included (parameters: number of hits and false alarms) and subjective alertness was assessed, to infer whether word-learning test findings reflect sedation or specific memory impairments. Delayed recall in the morning session was significantly worse in the alcohol group when compared to the placebo group (F(1,42)=6.0, p<0.02). In contrast, immediate recall and recognition were unimpaired in the alcohol group. In the morning session, relative to the placebo group, subjective alertness was significantly reduced in the alcohol group before and after the tests (F(1,44)=8.7, p<0.005; F(1,44)=13.3, p&<0.001, respectively). However, in the Mackworth clock test, the alcohol group and placebo group did not differ significantly in the morning session. The specific findings of impaired delayed recall show that memory retrieval processes are significantly impaired during alcohol hangover. Vigilance performance was not significantly affected, indicating that this memory impairment does not reflect sedation.

Adult↗

PubMed2002

Inhibition in children with attention-deficit/hyperactivity disorder: a psychophysiological study of the stop task.

BACKGROUND: The purpose of the study was to investigate and identify abnormal brain activity, as revealed by event-related potentials (ERPs) concurring with deficient inhibitory control in children with attention-deficit/hyperactivity disorder (ADHD). METHODS: Performance and ERPs from 16 children with ADHD and 16 control subjects were compared in the stop-signal paradigm. RESULTS: The ADHD children showed a lower inhibition percentage and their (estimated) response time to the stop signal was disproportionally longer compared to the slowing of reaction times to primary-task stimuli. In normal control subjects, fronto-central positivity (100-400 msec) after the onset of the stop-signal was larger in case of successful inhibition, relative to failed inhibition; this was less so in ADHD children. A late positive wave (500-700 msec), maximal at Oz on failed inhibition trials, and possibly related to error-detection, was smaller in ADHD children. CONCLUSIONS: These results point to abnormalities in brain processes involved in motor inhibition and error-detection in ADHD children.

Attention Deficit Disorder with Hyperactivity↗

PubMed2002

Benzodiazepines have no effect on fear-potentiated startle in humans.

RATIONALE: Pre-clinical and clinical investigations have provided a great deal of evidence that the fear-potentiated startle paradigm represents a valid model for the objective assessment of emotional states of anxiety and fear. OBJECTIVE: The four studies presented in this report sought to further validate the "threat of shock" paradigm as a human analogue to fear-potentiated startle in rats, by examining the effect of benzodiazepine administration on both baseline and fear-potentiated startle. METHODS: Three studies, conducted at Utrecht University, evaluated the effects of oxazepam and of diazepam on baseline and fear-potentiated startle, whereas a fourth study, conducted at Yale University, evaluated the effect of diazepam on baseline, contextual and cue-specific fear-potentiated startle. The threat of shock paradigm consisted of verbal instruction about two visual cues (the threat cue predicted the possible administration of electric shock, the other predicted a safe period), followed by a series of presentations of these cues. During these conditions, acoustic startle stimuli were presented in order to elicit startle responses. The magnitude of the startle response was used to index the degree of fear or alarm experienced during the periods of threat and safety. The fourth study examined the effect of IV administration of diazepam in a similar threat of shock paradigm except that there were two additional context manipulations: electrode placement and darkness. RESULTS: None of the drug manipulations affected specific threat-cue potentiation of startle. However, reductions in baseline startle were observed. Further, startle potentiation by darkness was inhibited by diazepam. CONCLUSIONS: At least one type of fear-potentiated startle, i.e. potentiation by a cue-specific fear manipulation, is not susceptible to benzodiazepine treatment. In contrast, effects of manipulations more akin to anxiety (darkness, context) appear sensitive to benzodiazepines. Human experimental models differentiating between these cue specific and contextual responses are needed to shed more light on differences in the anatomy and pharmacology of anxiety disorders.

Adolescent↗

PubMed2002

Split-second sequential selective activation in human secondary visual cortex.

This work addressed early selection based on nonspatial visual features, using event-related potentials (ERPs) with high temporal resolution and dipole-source modeling. Subjects were presented rapid sequences of gratings varying in spatial frequency and orientation, and were instructed to attend to gratings with one spatial frequency and ignore those with another. Attention effects started at 120-msec latency as anterior positivity and proceeded as posterior negativity (200 msec) and anterior negativity (265 msec). Dipole-source modeling suggested that these effects reflect the sequential selective activation of, on average, posterior dorsal-medial, posterior ventral-lateral, and anterior medial cortical areas. In contrast, stimulus-specific activity was observed well before 100-msec latency and characterized by dipoles with locations significantly posterior to those of the attention-modulated activity. These results indicate that even with highly discriminable spatial frequencies, selection is not as early as before the 100-msec latency, unlike what is often found for location selection. It is also separated in time and anatomically from the earliest stimulus-specific cortical activity. Reducing discriminability of the selection feature resulted in longer selection latencies, becoming manifest only at 175 msec as an apparent combination of posterior and anterior negativities, and in an elevated criterion for overt responding.

Adult↗

PubMed2002

Effects of alprazolam on driving ability, memory functioning and psychomotor performance: a randomized, placebo-controlled study.

Alprazolam is prescribed for the treatment of anxiety and panic disorder. Most users are presumably involved in daily activities such as driving. However, the effects of alprazolam on driving ability have never been investigated. This study was conducted to determine the effects of alprazolam (1 mg) on driving ability, memory and psychomotor performance. Twenty healthy volunteers participated in a randomized, double-blind, placebo-controlled crossover study. One hour after oral administration, subjects performed a standardized driving test on a primary highway during normal traffic. They were instructed to drive with a constant speed (90 km/h) while maintaining a steady lateral position within the right traffic lane. Primary performance measures were the Standard Deviation of Lateral Position (SDLP) and the Standard Deviation of Speed (SDS). After the driving test, subjective driving quality, mental effort, and mental activation during driving were assessed. A laboratory test battery was performed 2.5 h after treatment administration, comprising the Sternberg Memory Scanning Test, a Continuous Tracking Test, and a Divided Attention Test. Relative to placebo, alprazolam caused serious driving impairment, as expressed by a significantly increased SDLP (F(1,19) = 97.3, p <.0001) and SDS (F(1,19) = 30.4, p <.0001). This was confirmed by subjective assessments showing significantly impaired driving quality (F(1,19) = 16.4, p <.001), decreased alertness (F(1,19) = 43.4, p <.0001), decreased mental activation (F(1,19) = 5.7, p <.03) and increased mental effort during driving (F(1,19) = 26.4, p <.0001). Furthermore, alprazolam significantly impaired performance on the laboratory tests. In conclusion, alprazolam users must be warned not to drive an automobile or operate potentially dangerous machinery.

Adult↗

PubMed2002

Effects of typical and atypical antipsychotics on the prepulse inhibition of the startle reflex in patients with schizophrenia.

Patients with schizophrenia show a loss of sensory (motor) gating, which is reflected in a reduced prepulse inhibition (PPI) of the startle reflex. Furthermore, patients with schizophrenia habituate less than healthy subjects. From previous studies, it is clear that typical antipsychotics have little or no effect on either sensorimotor gating or habituation, while only limited data is available on the effects of atypical antipsychotics on these processes.Forty-four schizophrenic patients (27 stable on typical and 17 stable on atypical antipsychotics) and 35 healthy control subjects were tested in a PPI paradigm. The prepulse and startle stimuli were pure tones of 1500 Hz (duration 40 ms, intensity 80 dB and 110 dB respectively), with a fixed interstimulus interval of 120 milliseconds. Block effects in PPI and startle amplitude to the pulse alone trials (habituation) were analyzed over the three groups, using comedication (i.e., benzodiazepines) as a covariate. Main effect for block was found for startle amplitude (habituation), while main effects for group and block were found for percentage PPI. Further analysis displayed significant differences in PPI between the patients treated with typical antipsychotics and the healthy control group, while patients treated with atypical antipsychotics did not differ from either the healthy control group, or the patients treated with typical antipsychotics. Furthermore, post-hoc division of the patients treated with atypical antipsychotics in patients treated with clozapine and risperidone revealed that this superiority from atypical antipsychotics over typical antipsychotics appeared to be mainly based on the effects of clozapine. Patients with schizophrenia who are treated with atypical antipsychotics appear to have levels of sensorimotor gating that are more consistent with healthy controls than patients who are treated with typical antipsychotics. Furthermore, within the class of atypical antipsychotics, clozapine appears most potent in restoring this process.

Acoustic Stimulation↗

PubMed2002

Residual effects of middle-of-the-night administration of zaleplon and zolpidem on driving ability, memory functions, and psychomotor performance.

Thirty healthy volunteers participated in this two-part study. Part 1 was a single-blind, two-period crossover design to determine the effects of a single dose of ethanol (0.03% < BAC < 0.05%) or ethanol-placebo on driving ability, memory, and psychomotor performance. Part 2 was a double-blind, five-period crossover design to measure the effects of a middle-of-the-night administration of zaleplon 10 or 20 mg, zolpidem 10 or 20 mg, or placebo on driving ability 4 hours after administration and memory and psychomotor performance 6 hours after administration. The on-the-road driving test consisted of operating an instrumented automobile over a 100-km highway circuit at a constant speed (95 km/h) while maintaining a steady lateral position between the right lane boundaries. The standard deviation of lateral position (SDLP) was the primary performance parameter of the driving test. The psychomotor and memory test battery consisted of the Word Learning Test, the Critical Tracking Test, the Divided Attention Test, and the Digit Symbol Substitution Test. Data for each part were analyzed separately using ANOVA for crossover designs. Zaleplon 10 and 20 mg did not significantly impair driving ability 4 hours after middle-of-the-night administration. Relative to placebo, after zolpidem 10 mg, SDLP was significantly elevated, but the magnitude of the difference was small and not likely to be of clinical importance. Memory and psychomotor test performance was unaffected after both doses of zaleplon and zolpidem 10 mg. In contrast, zolpidem 20 mg significantly increased SDLP and speed variability. Further, zolpidem 20 mg significantly impaired performance on all psychomotor and memory tests. Finally, driving performance, Digit Symbol Substitution Test, Divided Attention Test, and immediate and delayed free recall of the Word Learning Test were significantly impaired after ethanol. The results show that zaleplon (10 and 20 mg) is a safe hypnotic devoid of next-morning residual impairment when used in the middle of the night.

Acetamides↗

PubMed2002

Normal P50 gating in children with autism.

BACKGROUND: An important characteristic of children with autism is their unusual reaction to stimuli, which may be related to problems in the filtering of sensory input. For this reason, sensory filtering was measured in children with autism using the P50 gating paradigm. METHOD: Twelve non-mentally retarded children with autism (i.e., having a DSM-IV diagnosis of either autistic disorder or pervasive developmental disorder not otherwise specified) and 11 healthy control children were tested for their ability to suppress P50, measured at the Cz electrode. RESULTS: No differences were found between the children with autism and the control children with regard to absolute P50 amplitudes and P50 suppression. CONCLUSION: The excitability of the neuronal substrate that causes P50 is normal in children with autism, as are the early, inhibitory processes related to P50 gating. These results distinguish between subjects with autism and subjects with schizophrenia, in whom sensory gating is abnormal.

Acoustic Stimulation↗