Biomedical subjects

Thomas Rammsayer

Publications and source records attributed to Thomas Rammsayer.

7 recordsLinked to original sources

PubMed2006

Sensorimotor effects of pergolide, a dopamine agonist, in healthy subjects: a lateralized readiness potential study.

OBJECTIVE: The major purpose of the present study was to further elucidate dopaminergic modulation of sensorimotor processing in healthy human subjects. MATERIALS AND METHODS: To more specifically analyze dopaminergic effects on premotor and motor stages of sensorimotor processing, lateralized readiness potentials (LRPs) were obtained. In a randomized double-blind crossover design, either 0.075 mg of the D1/D2 dopamine (DA) agonist pergolide or placebo were administered to 12 healthy male volunteers ranging from 19 to 25 years in age. The subjects performed a two-choice visual reaction time task. In addition to behavioral measures, such as response speed and error rate, stimulus-locked LRP (S-LRP) and response-locked LRP (LRP-R) latencies were determined. To better dissociate potential central and peripheral motor effects, measures of response dynamics and response-locked electromyogram (EMG-R) recordings were also obtained. OBSERVATIONS: Pergolide reliably enhanced speed of stimulus-related information processing as indicated by shorter S-LRP latencies while LRP-R latencies, reaction time, and indicators of response dynamics were not influenced by DA agonistic treatment. Furthermore, lower EMG-R amplitudes and an increased number of wrong-hand responses were observed under pergolide compared to placebo. CONCLUSION: The results indicate that dopaminergic neurotransmission effectively modulates early perceptual and cognitive stages of information processing as suggested by neural network models of the functional role of prefrontal DA. The lack of an effect on aspects of motor processing may be due to a higher capacity of the nigrostriatal compared to the mesocortical DA system to compensate pharmacologically induced changes in dopaminergic activity.

Adult↗

PubMed2005

No evidence for qualitative differences in the processing of short and long temporal intervals.

Several lines of research suggest that two distinct timing mechanisms are involved in temporal information processing: a sensory mechanism for processing of durations in the range of milliseconds and a cognitively controlled mechanism for processing of longer durations. The present study employed a dual-task approach and a sensory interference paradigm to further elucidate the distinct timing hypothesis. Experiment 1 used mental arithmetic as a nontemporal secondary task, Experiment 2 a memory search task, and Experiment 3 a visuospatial memory task. In Experiment 4, a loudness manipulation was applied. Mental arithmetic and loudness manipulation affected temporal discrimination of both brief and long intervals, whereas the two remaining tasks did not influence timing performance. Observed differences in interference patterns may be explained by some tasks being more difficult than others. The overall pattern of results argues against two qualitatively distinct timing mechanisms, but is consistent with attention-based cognitive models of human timing.

Adult↗

PubMed2004

Perceived duration of expected and unexpected stimuli.

Three experiments assessed whether perceived stimulus duration depends on whether participants process an expected or an unexpected visual stimulus. Participants compared the duration of a constant standard stimulus with a variable comparison stimulus. Changes in expectancy were induced by presenting one type of comparison more frequently than another type. Experiment 1 used standard durations of 100 and 400 ms, and Experiments 2 and 3 durations of 400 and 800 ms. Stimulus frequency did not affect perceived duration in Experiment 1. In Experiments 2 and 3, however, frequent comparisons were perceived as shorter than infrequent ones, and discrimination performance was better for infrequent comparisons. Overall, this study supports the notion that infrequent stimuli increase the speed of an internal pacemaker.

Adult↗

PubMed2004

Differences in the transmission of sensory input into motor output between introverts and extraverts: Behavioral and psychophysiological analyses.

The present study was designed to investigate extraversion-related individual differences in the speed of transmission of sensory input into motor output. In a sample of 16 introverted and 16 extraverted female volunteers, event-related potentials, lateralized readiness potentials (LRPs), and electromyogram (EMG) were recorded as participants performed a visual choice reaction time task. As additional behavioral indicators of performance, measures of reaction time (RT) and response dynamics were obtained. Although extraversion-related differences were found neither for behavioral measures nor for the N1 and P3 components of the evoked potential, introverts showed a reliably shorter latency in stimulus-locked LRP than extraverts. This latter finding supports the notion of faster stimulus analysis in introverts compared to extraverts. Furthermore, there was no indication of extraversion-related individual differences in speed of response organization and response execution as indicated by response-locked LRP and EMG latencies, respectively. However, a significantly higher EMG amplitude observed with introverts pointed to a less accurately adjusted motor output system of introverts compared to extraverts.

Adult↗

PubMed2004

Extraversion-related differences in response organization: evidence from lateralized readiness potentials.

Research utilizing a mental-chronometry approach to examine individual differences in extraversion suggests that extraversion-related individual differences may involve stimulus analysis, response organization, and peripheral motor processes. In a sample of 14 introverted and 14 extraverted female volunteers event-related potentials (ERP) and lateralized readiness potentials (LRPs) were recorded concurrently with reaction time (RT) measures as participants performed a two-choice go/no-go task. Although there were no extraversion-related differences in mean reaction time, introverts showed higher N1 amplitudes and shorter P3 latencies compared to extraverts. Furthermore, response-locked LRP latencies were reliably shorter for extraverts than for introverts. The latter finding provides first direct evidence for the contribution of central processes related to motor activation to account for extraversion-related individual differences.

Adult↗

PubMed2003

Variable foreperiods and temporal discrimination.

Temporal judgements are often accounted for by a single-clock hypothesis. The output of such a clock is reported to depend on the allocation of attention. In the present series of experiments, the influence of attention on temporal information processing is investigated by systematic variations of the period preceding brief empty intervals to be judged. Two indicators of timing performance, temporal sensitivity, reflecting discrimination performance, and perceived duration served as dependent variables. Foreperiods ranged from 0.3 to 0.6 s in Experiments 1 to 4. When the foreperiod varied randomly from trial to trial, perceived duration was longer with increasing length of foreperiod (Experiments 1 and 3 with brief auditory markers and Experiment 4 with brief visual markers), an effect that disappeared with no trial-to-trial variations (Experiment 2). Longer foreperiods also enhanced performance on temporal discrimination of auditory empty intervals with a base duration of 100 ms (Experiments 1 and 5), whereas discrimination performance was unaffected for auditory intervals with a base duration of 500 ms (Experiment 3). The variable-foreperiod effect on perceived duration also held when foreperiods ranged from 0.6 to 1.5 s (Experiments 57). Findings suggest that foreperiods appear to effectively modulate attention mechanisms necessary for temporal information processing. However, alternative explanations such as assimilation or compatibility effects cannot be totally discarded.

Adult↗

PubMed2002

Processing of temporal information and the basal ganglia: new evidence from fMRI.

Temporal information processing is a fundamental brain function, which might include central timekeeping mechanisms independent of sensory modality. Psychopharmacological and patient studies suggest a crucial role of the basal ganglia in time estimation. In this study, functional magnetic resonance imaging (fMRI) was applied in 15 healthy right-handed male subjects performing an auditory time estimation task (duration discrimination of tone pairs in the range of 1,000-1,400 ms) and frequency discriminations (tone pairs differing in pitch, around 1,000 Hz) as an active control task. Task difficulty was constantly modulated by an adaptive algorithm (weighted up-down method) reacting on individual performance. Time estimation (vs rest condition) elicited a distinct pattern of cerebral activity, including the right medial and both left and right dorsolateral prefrontal cortices (DLPFC), thalamus, basal ganglia (caudate nucleus and putamen), left anterior cingulate cortex, and superior temporal auditory areas. Most activations showed lateralisation to the right hemisphere and were similar in the frequency discrimination task. Comparing time and frequency tasks, we isolated activation in the right putamen restricted to time estimation only. This result supports the notion of central processing of temporal information associated with basal ganglia activity. Temporal information processing in the brain might thus be a distributed process of interaction between modality-dependent sensory cortical function, the putamen (with a timing-specific function), and additional prefrontal cortical systems related to attention and memory. Further investigations are needed to delineate the differential contributions of the striatum and other areas to timing.

Acoustic Stimulation↗