Search results for "Stimulus"
showing 10 items of 555 documents
Are postural responses to backward and forward perturbations processed by different neural circuits?
2013
Item does not contain fulltext Startle pathways may contribute to rapid accomplishment of postural stability. Here we investigate the possible influence of a startling auditory stimulus (SAS) on postural responses. We formulated four specific questions: (1) can a concurrent SAS shorten the onset of automatic postural responses?; and if so (2) is this effect different for forward versus backward perturbations?; (3) does this effect depend on prior knowledge of the perturbation direction?; and (4) is this effect different for low- and high-magnitude perturbations? Balance was perturbed in 11 healthy participants by a movable platform that suddenly translated forward or backward. Each particip…
Do Intensity Ratings and Skin Conductance Responses Reliably Discriminate Between Different Stimulus Intensities in Experimentally Induced Pain?
2010
Abstract The present study addresses the question whether pain-intensity ratings and skin conductance responses (SCRs) are able to detect different intensities of phasic painful stimuli and to determine the reliability of this discrimination. For this purpose, 42 healthy participants of both genders were assigned to either electrical, mechanical, or laser heat-pain stimulation (each n = 14). A whole range of single brief painful stimuli were delivered on the right volar forearm of the dominant hand in a randomized order. Pain-intensity ratings and SCRs were analyzed. Using generalizability theory, individual and gender differences were the main contributors to the variability of both intens…
Distraction of task-relevant information processing by irrelevant changes in auditory, visual, and bimodal stimulus features: A behavioral and event-…
2009
Distractibility with auditory, visual, and bimodal stimulus changes was investigated using an audio-visual distraction paradigm. Participants were asked to discriminate between equiprobable short and long audio-visual stimuli. Infrequently, the auditory, the visual, or both parts of the stimuli changed. These rare deviations (deviants) were irrelevant for the actual task. The influence of the three types of deviant stimuli on the processing of task-relevant information was assessed with behavioral and event-related potential (ERP) measures assuming that bimodal deviants would lead to an increase in distraction. Behavioral and ERP results did not support this assumption, as reaction time (RT…
Differential effects on the laser evoked potential of selectively attending to pain localisation versus pain unpleasantness
2004
Abstract Objective : To determine the effects on the laser evoked potential (LEP) of selectively attending to affective (unpleasantness) versus sensory-discriminative (localisation) components of pain. Methods : LEPs, elicited by painful CO 2 laser stimulation of two areas of the right forearm, were recorded from 62 electrodes in 21 healthy volunteers, during three tasks that were matched for generalised attention: Localisation (report stimulus location), Unpleasantness (report stimulus unpleasantness), Control (report pain detection). LEP components are named by polarity, latency, and electrode. Results : N300-T7 peak amplitude was significantly greater during Localisation than Unpleasantn…
Paradoxical heat sensation in patients with multiple sclerosis
1996
Temperature thresholds were determined in 16 patients with probable or definite multiple sclerosis, in six patients with possible but unconfirmed multiple sclerosis and in 34 healthy subjects, using the method of limits and the thermal sensory limen (TSL) of the MarStock technique. A significant proportion of the patients had thresholds outside the 2.5 SD range for normal subjects, both for warmth detection threshold and TSL. In addition, 10 patients with probable or definite multiple sclerosis and one patient with possible multiple sclerosis reported a paradoxical heat sensation, i.e. a sensation of warmth elicited by a cold stimulus. This illusion was almost exclusively observed with the …
Manual Reaction Times and Brain Dynamics after 'Awake Surgery' of Slow-Growing Tumours Invading the Parietal Area. A Case Report.
2012
International audience; PRIMARY OBJECTIVES: Awake surgeries of slow-growing tumours invading the brain and guided by direct electrical stimulation induce major brain reorganizations accompanied with slight impairments post-operatively. In most cases, these deficits are so slight after a few days that they are often not detectable on classical neuropsychological evaluations. Consequently, this study investigated whether simple visuo-manual reaction time paradigms would sign some level of functional asymmetries between both hemispheres. Importantly, the visual stimulus was located in the saggital plane in order to limit attentional biases and to focus mainly on the inter-hemispheric asymmetry…
Isometric muscle contractions after double pulse stimulation. comparison of healthy subjects and patients with myotonic dystrophy.
1996
Isometric contractions of the adductor pollicis muscle were studied in healthy subjects and patients with myotonic dystrophy after single and double stimuli of the ulnar nerve using a wide range of interstimulus intervals (ISI, 0.4-180 ms). In healthy subjects, the force contributed by a second stimulus was greater than the single twitch force being maximal (mean + 140%) at 12-ms ISI. In myotonic dystrophy, the force contributed by the second stimulus was (relative to a reduced twitch amplitude) increased (mean + 204%) with a maximum at 4.8-ms ISI. An abnormal increase of force was only recorded if the single twitch force was clearly reduced. The absolute refractory period of muscle contrac…
Precursors of the evoked K-complex in event-related brain potentials in stage 2 sleep.
1997
The aim of the study was to examine precursors of the evoked K-complex as manifested in event-related brain potentials (ERPs) during stage 2 sleep. ERPs to infrequent deviant tones of 1100 and 2000 Hz and immediately preceding frequent standard tones of 1000 Hz were compared between trials containing and trials not containing a K-complex (KC trials, NO KC trials, respectively) to the deviant tones. The N350 wave to the deviant tones was markedly larger during the KC than during the NO KC trials. Also the P210 wave to the 2000 Hz deviant tone showed the same phenomenon. No definite evidence was found for the mismatch negativity-like deflection during the KC trials. ERPs to the standard tones…
Are different kinds of acoustic features processed differently for speech and non-speech sounds?
2001
This study examined how changes in different types of acoustic features are processed in the brain for both speech and non-speech sounds. Event-related potentials (ERPs) were recorded in native Finnish speakers presented with sequences of repetitive vowels (/e/) or complex harmonical tones interspersed with infrequent changes in duration, frequency and either a vowel change (/o/ for vowel sequences) or a double deviant (frequency+duration change for tone sequences). The stimuli were presented monaurally in separate blocks to either the left or right ear. The results showed that speech stimuli were more efficiently processed than harmonical tones as reflected by an enhanced mismatch negativi…
Habituation and Sensitization Processes in Depressive Disorders
1999
The aim of the present study was to investigate further into habituation and sensitization processes in depressive disorders. The depressive subjects were 27 outpatients. All of them were diagnosed according to DSM-III-R criteria. Controls were 27 normal subjects. The amplitudes of electrodermal responses and the basal levels were recorded during a stimuli series of 15 80-dB tones and of 1 100-dB tone in the 11th trial. The depressive patients displayed lower basal conductance levels and lower conductance amplitudes in orienting responses to the first stimulus and to stimulus change. No differences were found in conductance response amplitudes of stimuli series, although a tendency towards …