Manual Reaction Time Research Articles

Componentes sensoriais e atencionais do tempo de reação: efeitos do tamanho, excentricidade e previsibilidade de estímulos visuais

A percepção visual depende do arcabouço sensorial e do processamento atencional. Este trabalho estudou o efeito, sobre o tempo de reação manual (TR), do tamanho, excentricidade e previsibilidade de estímulos visuais. No experimento 1 (n=8), um alvo foi apresentado aleatoriamente em uma de quatro excentricidades diferentes, possuindo três possíveis tamanhos. O experimento 2 (n=12) apresentava configuração similar, porém uma pista indicava o quadrante de maior probabilidade (70%) de apresentação do alvo. Os resultados mostraram um aumento do TR em função da excentricidade do alvo, além de uma diminuição do TR com o aumento do tamanho do alvo e indicação correta da pista. Uma análise das interações sugere uma superposição de mecanismos atencionais e puramente sensoriais compartilhando um estágio comum do processamento visual.

Deep brain stimulation of the subthalamic nucleus in Parkinson’s disease

The purpose of this study was to determine whether the very large effects of saccadic latency distribution, generated by deep brain stimulation of the subthalamic nuclei are reflected in quantitatively corresponding changes for manual responses, rather than representing a reflection of the specific role of the subthalamus in controlling saccades. Saccadic and manual reaction times were measured under as nearly identical conditions as possible in six patients with implanted subthalamic electrodes and in six age-matched controls with the stimulation either on or off. Median latency was found to be reduced by stimulation in a similar way to saccadic latency; in neither case was there a significant change in the Linear Approach to Threshold with Ergotic Rate parameter σ. For both types of response, the effect is to move the responses proportionately in the direction of average of responses in the control group. We therefore conclude that the previously described effects of stimulation on latency are not a phenomenon peculiar to saccades, increasing confidence in using saccadic latency measurements as a surrogate for more general responses when determining the efficacy of deep brain stimulation.

On the convergence of time interval moments: caveat sciscitator

The frequency distributions of biological time-intervals (TIs) have been measured in innumerable behavioural and neurophysiological studies including, for example, reaction time experiments and studies of neuronal spike timing. Regardless of context, TI distributions tend to be significantly positively skewed, and many studies have attempted to characterise these distributions by their mean or higher moments (variance, skewness, and kurtosis). It is, however, not widely appreciated in the neural/behavioural literature that highly skewed distributions may not have moments: they may not converge to a finite value. For example, the reciprocal Normal distribution, frequently used as a model of saccade latency and manual reaction time, does not have a finite mean or higher moments. We explore this non-trivial phenomenon.We introduce ‘cumulative’ moments and show that moment convergence can be easily related to the distribution of the reciprocal of time-intervals (rate). The behaviour of the rate distribution near zero determines which moments in the time domain converge. Non-convergence may be very slow leading to the appearance of convergence, but after infinite time they become infinite (pseudo-convergence). Experiments take place in finite time and cannot reconcile pseudo-convergence. Nevertheless, cumulative sample moments can provide insight into the convergence of the parent moments, but this depends on sample size. We illustrate convergence issues with three empirical examples: manual reaction times, neural inter-spike intervals, and optokinetic inter-saccadic intervals. We conclude that estimating moments of skewed TI distributions is at best questionable and propose that rate (reciprocal TI) usually (but not always) provides more information.

Unraveling the Association Between SSRI Use and Falls

Selective serotonin reuptake inhibitors (SSRIs) are widely used to treat depression and are also associated with an increased falls risk. However, the biological mechanism underlying accidental falls with SSRI intake has yet to be elucidated. The present experimental study was designed to investigate whether obstacle avoidance skills in long-term (>90 days), senior paroxetine users (61 ± 5.8 years) are affected during gait, simple and challenging postural balance tasks, as well as during manual reaction time tasks. The performance of the paroxetine users was compared with healthy group-matched controls (60 ± 4.8 years). The results demonstrated impaired postural balance in the paroxetine users, especially during one-legged stance or under various dual-task conditions. Although the deficit in one-legged stance could indicate vestibular involvement, this was deemed unlikely because performance of standing on compliant surface with closed eyes remained unaffected. Paroxetine use also failed to affect manual reaction times or obstacle avoidance performance. It is suggested that paroxetine affects attentional capacities particularly in conjunction with balance control. Compared with healthy seniors, long-term senior users of paroxetine seem to be at an increased risk of falling due to impairments in balance control, especially when attention has to be divided between 2 concurrent activities.

Scene-based Contextual Cueing in the Rhesus Macaque

The neurophysiology that underlies the guidance of attention during search through naturalistic scenes remains largely unexplored. In order to understand how scene identification leads to the prioritization of certain regions of space, we have developed an animal analogue of scene-based contextual cueing in the monkey so that we might conduct physiological experiments. Our task was adapted from the contextual cueing task of Brockmole and Henderson (2006). The monkey must search for a semi-transparent object embedded in a real-world scene. The monkey has previous experience classifying these objects into one of two arbitrary categories by pressing response buttons. In half of the scenes (non-predictive condition), objects appeared randomly in one of eight locations. In the other half of the scenes (predictive condition), scene identity cued the location of the object through consistent scene-location pairings. Along with manual reaction time, we also tracked the monkey's eye-position in order to examine how the monkey searched through each scene and how many saccades it took to locate the target. As in humans, the monkey showed a benefit when executing searches through repeated scenes across multiple sessions, demonstrating sensitivity to scene familiarity. The monkey also showed a significant reaction time benefit when searching through predictive scenes when compared to non-predictive scenes, demonstrating scene contextual cueing. Similar to the associations formed by human participants in Chun & Jiang (2003), these scene-location associations were stable after a week-long hiatus, indicating the long-term nature of the associations. Finally, we conducted target-absent tests during which we monitored eye-movements. In these tests, the monkey saccaded to the cued location in an average of less than two saccades and did so on greater than 90% of trials. These results demonstrate scene-based contextual cueing in the macaque, showing promise as a method for uncovering the physiological basis for attentional guidance during active search.

Basic mechanisms of visual attention are normal in Asperger’s syndrome

Several studies 1, 2, 3 have shown that visual search is superior in people with autism relative to that of normal controls. Eye movement recordings during visual search 2, 3 show that people with autism make fixations of shorter duration (implying faster encoding of stimuli) and have fewer fixations than controls (implying that they encode more stimuli pr. fixation than controls). Participants in visual search experiments must rely on both eye movements and manual reaction-times. Therefore measures of mechanisms driving attention and perceptual abilities might be confounded with mechanisms driving hand and eye movements.

ERP evidence for selective drop in attentional costs in uncertain environments: Challenging a purely premotor account of covert orienting of attention

Several studies have proved that the reliability of endogenous spatial cues linearly modulates the reaction time advantage in the processing of targets at validly cued vs. invalidly cued locations, i.e. the “validity effect”. This would imply that with non-predictive cues, no “validity effect” should be observed. However, contrary to this prediction, one could hypothesize that attentional benefits by valid cuing (i.e. the RT advantage for validly vs. neutrally cued targets) can still be maintained with non-predictive cues, if the brain were endowed with mechanisms allowing the selective reduction in costs of reorienting from invalidly cued locations (i.e. the reduction of the RT disadvantage for invalidly vs. neutrally cued targets). This separated modulation of attentional benefits and costs would be adaptive in uncertain contexts where cues predict at chance level the location of targets. Through the joint recording of manual reaction times and event-related cerebral potentials (ERPs), we have found that this is the case and that relying on non-predictive endogenous cues results in abatement of attentional costs and the difference in the amplitude of the P1 brain responses evoked by invalidly vs. neutrally cued targets. In contrast, the use of non-predictive cues leaves unaffected attentional benefits and the difference in the amplitude of the N1 responses evoked by validly vs. neutrally cued targets. At the individual level, the drop in costs with non-predictive cues was matched with equivalent lateral biases in RTs to neutrally and invalidly cued targets presented in the left and right visual field. During the cue period, the drop in costs with non-predictive cues was preceded by reduction of the Early Directing Attention Negativity (EDAN) on posterior occipital sites and by enhancement of the frontal Anterior Directing Attention Negativity (ADAN) correlated to preparatory voluntary orienting. These findings demonstrate, for the first time, that the segregation of mechanisms regulating attentional benefits and costs helps efficiency of orienting in “uncertain” visual spatial contexts characterized by poor probabilistic association between cues and targets.

This Is the Rhythm of Your Eyes: The Phase of Ongoing Electroencephalogram Oscillations Modulates Saccadic Reaction Time

Motor reaction times in humans are highly variable from one trial to the next, even for simple and automatic tasks, such as shifting your gaze to a suddenly appearing target. Although classic models of reaction time generation consider this variability to reflect intrinsic noise, some portion of it could also be attributed to ongoing neuronal processes. For example, variations of alpha rhythm frequency (8-12 Hz) across individuals, or alpha amplitude across trials, have been related previously to manual reaction time variability. Here we investigate the trial-by-trial influence of oscillatory phase, a dynamic marker of ongoing activity, on saccadic reaction time in three paradigms of increasing cognitive demand (simple reaction time, choice reaction time, and visual discrimination tasks). The phase of ongoing prestimulus activity in the high alpha/low beta range (11-17 Hz) at frontocentral locations was strongly associated with saccadic response latencies. This relation, present in all three paradigms, peaked for phases recorded ∼50 ms before fixation point offset and 250 ms before target onset. Reaction times in the most demanding discrimination task fell into two distinct modes reflecting a fast but inaccurate strategy or a slow and efficient one. The phase effect was markedly stronger in the group of subjects using the faster strategy. We conclude that periodic fluctuations of electrical activity attributable to neuronal oscillations can modulate the efficiency of the oculomotor system on a rapid timescale; however, this relation may be obscured when cognitive load also adds a significant contribution to response time variability.

The default allocation of attention is broadly ahead of smooth pursuit

When moving through our environment, it is vital to preferentially process positions on our future path in order to react quickly to critical situations. During smooth pursuit, attention may be directed ahead with either a focused locus or a broad bias. We examined the 2D spatial extent of attention during a smooth pursuit task using both saccade (SRT) and manual (MRT) reaction times as measures of attentional allocation. Targets were flashed at various locations around current eye position while subjects pursued a moving target. Subjects made a saccade or pressed a button as soon as they perceived the target. Both SRTs and MRTs were shortest to targets flashed ahead of compared to behind the direction of pursuit across half of the visual field ahead of pursuit direction. Furthermore, we found an increase specific to SRTs at small target eccentricities directly ahead of pursuit, which may be related to an additional saccade trigger strategy; small saccades take longer to execute if smooth pursuit brings the eyes close to the target. In summary, both SRTs and MRTs revealed that attention is by default broadly allocated in the visual hemi-field ahead of the line of sight during smooth pursuit eye movements. This attentional bias may serve a predictive purpose for facilitating the processing of upcoming events.

Effects of intensity and positional predictability of a visual stimulus on simple reaction time

The influence of visual stimuli intensity on manual reaction time (RT) was investigated under two different attentional settings: high (Experiment 1) and low (Experiment 2) stimulus location predictability. These two experiments were also run under both binocular and monocular viewing conditions. We observed that RT decreased as stimulus intensity increased. It also decreased as the viewing condition was changed from monocular to binocular as well as the location predictability shifted from low to high. A significant interaction was found between stimulus intensity and viewing condition, but no interaction was observed between neither of these factors and location predictability. These findings support the idea that the stimulus intensity effect arises from purely sensory, pre-attentive mechanisms rather than deriving from more efficient attentional capture.

The effect of a non-steroidal anti-inflammatory drug on two important predictors for accidental falls: Postural balance and manual reaction time. A randomized, controlled pilot study

Accidental falls in older individuals are a major health and research topic. Increased reaction time and impaired postural balance have been determined as reliable predictors for those at risk of falling and are important functions of the central nervous system (CNS). An essential risk factor for falls is medication exposure. Amongst the medications related to accidental falls are the non-steroidal anti-inflammatory drugs (NSAIDs). About 1–10% of all users experience CNS side effects. These side effects, such as dizziness, headaches, drowsiness, mood alteration, and confusion, seem to be more common during treatment with indomethacin. Hence, it is possible that maintenance of (static) postural balance and swift reactions to stimuli are affected by exposure to NSAIDs, indomethacin in particular, consequently putting older individuals at a greater risk for accidental falls. The present study investigated the effect of a high indomethacin dose in healthy middle-aged individuals on two important predictors of falls: postural balance and reaction time. Twenty-two healthy middle-aged individuals (59.5 ± 4.7 years) participated in this double-blind, placebo-controlled, randomized crossover trial. Three measurements were conducted with a week interval each. A measurement consisted of postural balance as a single task and while concurrently performing a secondary cognitive task and reaction time tasks. For the first measurement indomethacin 75 mg (slow-release) or a visually identical placebo was randomly assigned. In total, five capsules were taken orally in the 2.5 days preceding assessment. The second measurement was without intervention, for the final one the first placebo group got indomethacin and vice versa. Repeated measures GLM revealed no significant differences between indomethacin, placebo, and baseline in any of the balance tasks. No differences in postural balance were found between the single and dual task conditions, or on the performance of the dual task itself. Similarly, no differences were found on the manual reaction time tasks. The present study showed that a high indomethacin dose does not negatively affect postural balance and manual reaction time in this healthy middle-aged population. Although the relatively small and young sample limits the direct ability to generalize the results to a population at risk of falling, the results indicate that indomethacin alone is not likely to increase fall risk, as far as this risk is related to abovementioned important functions of the CNS, and not affected by comorbidities.

Hemispheric Asymmetry in the Remapping and Maintenance of Visual Saliency Maps: A TMS Study

Parietal cortex has been implicated in the updating, after eye movements, of a salience map that is required for coherent visual experience and for the control of visually guided behavior. The current experiment investigated whether TMS over anterior intraparietal cortex (AIPCx), just after a saccade, would affect the ability to update and maintain a salience map. In order to generate a salience map, we employed a paradigm in which an uninformative cue was presented at one object in a display to generate inhibition of return (IOR)-an inhibitory tag that renders the cued object less salient than others in the display, and that slows subsequent responses to visual transients at its location. Following the cue, participants made a saccade to either left or right, and we then probed for updating of the location of IOR by measuring manual reaction time to targets appearing at cued location of the cued compared to an uncued object. Between the time of saccade initiation and target appearance, dual-pulse TMS was targeted over right (Experiment 1) or left AIPCx (Experiment 2), and a vertex control side. Updating of the location of IOR was eliminated by TMS over right, but not the left, AIPCx, suggesting that right parietal cortex is involved in the remapping of IOR. Remapping was eliminated by right AIPCx, regardless of whether the saccade was made to the left (contralateral), or right (ipsilateral) visual field, and regardless of which field the target appeared in. We conclude that right AIPCx is the neural substrate for maintaining a salience map across saccades, and not simply for propagating an efference copy of saccade commands.

Perceptual and Motor Inhibition in Individuals With Vestibular Disorders

Vestibular dysfunction has been shown to be associated with altered cognitive function. The purpose of this study was to examine changes in cognitive function in participants with vestibular disease during the course of vestibular physical therapy. Twenty-two participants (mean age = 52, standard deviation = 11) with previously diagnosed vestibular disorders were tested at the beginning and end of rehabilitation. The Motor and Perceptual Inhibition Test (MAPIT) was used to assess manual reaction times when responding to various stimuli presented on a computer screen. Additional physical performance measures and questionnaires related to dizziness, fear of falling, and activities of daily living were used to quantify change during the 6-week intervention period. The repeatable battery for the assessment of neuropsychological status (a measure of memory and executive function) was used to ensure that participants did not have memory or executive function deficits. Overall, there were no significant differences in MAPIT score before versus after physical therapy intervention, however there were some participants who demonstrated improvements in motor inhibition (MI) and perceptual inhibition (PI) scores. Interstingly, 8 of the 9 participants with abnormal caloric test findings had improvements on 2 of the PI scores. Overall 50% to 64% of the participants demonstrated improvement in the 4 different MAPIT scores. There were improvements in physical performance and self-report measures at the end of the 6-week physical therapy intervention program. Individuals with vestibular disorders may show improvement in MI and PI after a 6-week physical therapy intervention program; those with abnormalities on caloric and rotational chair tests appear especially likely to experience improvement in PI. Additional study is needed to determine whether individuals with vestibular disorders have remediable deficits in MI and PI.

Laterality effects in schizophrenia and bipolar disorder

There are numerous reports in the literature of lateralised structural cerebral abnormalities and alterations of the corpus callosum in the major psychoses. In the light of these findings the purpose of this study was to directly compare hemispheric differences and callosal interhemispheric transmission (IT) in schizophrenia and bipolar disorder. To do that we tested schizophrenic (SCZ), bipolar disorder (BD) patients and controls in a simple manual reaction time (RT) task with lateralised visual stimuli (Poffenberger paradigm) which enables one to test both laterality effects and IT time. We found an overall slowing of responses with the right hand in schizophrenics but not in bipolar patients, who, like controls, showed no hand differences. This selective slowing down of the right hand is likely to be related to abnormalities of intrahemispheric cortico-cortical connections in the left hemisphere. In contrast, IT time was similar in SCZ and BD patients and did not differ with respect to controls. Two are the novel findings of the present study: first both SZC and BD share a normal IT of visuomotor information despite the presence of callosal abnormalities. Second, an impairment of intrahemispheric left hemispheric processing is present only in SCZ patients. This represents a potentially important clue to a further understanding of the pathogenetic differences between the two major psychoses.

Processing emotional stimuli: Comparison of saccadic and manual choice-reaction times

We compared the speed of discrimination for emotional and neutral faces in four experiments, using a forced-choice saccadic and manual reaction time task. Unmasked, brief (20 ms) bilateral presentation of schematic (Exp. 1) or naturalistic (Exp. 2) emotional/neutral face pairs, led to shorter discrimination of emotional stimuli in saccadic localisation task. When the effect of interference from emotional stimuli is ruled out by showing a pairing of the emotional or neutral face with an outline face, faster saccadic discrimination was obtained for fearful facial expression only (Exp. 3). The manual discrimination reaction time was not significantly different for emotional versus neutral stimuli. To explore the absence of a manual RT effect we manipulated the stimulus duration (20 ms vs. 500 ms: Exp. 4). Faster saccadic discrimination of emotional stimuli was observed at both durations. For manual responses, emotional bias was observed only at the longest duration (500 ms). Overall, comparison of saccadic and manual responses shows that faster discrimination of emotional/neutral stimuli can be carried out within the oculomotor system. In addition, emotional stimuli are processed preferentially to neutral face stimuli.

The comparison of visual working memory representations with perceptual inputs.

The human visual system can notice differences between memories of previous visual inputs and perceptions of new visual inputs, but the comparison process that detects these differences has not been well characterized. In this study, the authors tested the hypothesis that differences between the memory of a stimulus array and the perception of a new array are detected in a manner that is analogous to the detection of simple features in visual search tasks. That is, just as the presence of a task-relevant feature in visual search can be detected in parallel, triggering a rapid shift of attention to the object containing the feature, the presence of a memory-percept difference along a task-relevant dimension can be detected in parallel, triggering a rapid shift of attention to the changed object. Supporting evidence was obtained in a series of experiments in which manual reaction times, saccadic reaction times, and event-related potential latencies were examined. However, these experiments also showed that a slow, limited-capacity process must occur before the observer can make a manual change detection response.

Right sided weakness with right subdural hematoma: Motor deafferentation of left hemisphere resulted in paralysis of the right side

Background: A right handed man with trauma to the head was admitted with headache and seizures. A severe right sided weakness was noted after a blunt trauma to the right side of his head.Methods and results: MRI of brain revealed a right-sided subdural hematoma and a normal left hemisphere and downstream motor pathways. Bimanual simultaneous drawing and manual reaction times indicated that the patient was right hemispheric in laterality of his major hemisphere.Conclusion: The right sided weakness in this patient was due to temporary transcallosal disconnection (diaschisis) of the minor hemisphere (left, in this case) from the excitatory signals arising from those structures of his major hemisphere devoted to movements occurring on nondominant side, transmitted via the corpus callosum to his left hemisphere. This case draws attention to disparity between neural and behavioral handedness (laterality of major hemisphere versus that of the preferred hand). Drawing longer lines by the left hand in simultaneous bimanual tasks and a slower simple reaction time to central visual stimuli by the ostensible dominant hand permitted lateralization of the major hemisphere to the right. Thus, the neurally nondominant side (right) lagged behind the dominant (left) by an interval equal to interhemispheric transfer time.

Visual Reaction Time and Size Constancy

We carried out six experiments to find out whether simple manual reaction time (RT) to flux-equated visual stimuli of different size is modulated by size constancy or by the retinal angle subtended by the stimuli. We found that RT decreased with the increase in perceived stimulus size rather than retinal angle and that this relationship depended on the use of familiar 3-D-like stimuli and on the availability of other size-constancy cues. Thus, a stereotyped speeded motor response, such as that employed in a simple RT paradigm, is modulated by size constancy, as is the case with perceptual judgments. The present results provide original evidence on the relationship between simple RT and perception.

What is “Odd” in Posner's Location-cueing Paradigm? Neural Responses to Unexpected Location and Feature Changes Compared

Within the parietal cortex, the temporo-parietal junction (TPJ) and the intraparietal sulcus (IPS) seem to be involved in both spatial and nonspatial functions: Both areas are activated when misleading information is provided by invalid spatial cues in Posner's location-cueing paradigm, but also when infrequent deviant stimuli are presented within a series of standard events. In the present study, we used functional magnetic resonance imaging to investigate the distinct and shared brain responses to (i) invalidly cued targets requiring attentional reorienting, and (ii) to target stimuli deviating in color and orientation leading to an oddball-like distraction effect. Both unexpected location and feature changes were accompanied by a significant slowing of manual reaction times. Bilateral TPJ and right superior parietal lobe (SPL) activation was observed in response to invalidly as compared to validly cued targets. In contrast, the bilateral inferior occipito-temporal cortex, the left inferior parietal cortex, right frontal areas, and the cerebellum showed stronger activation in response to deviant than to standard targets. Common activations were observed in the right angular gyrus along the IPS and in the right inferior frontal gyrus. We conclude that the superior parietal and temporo-parietal activations observed here as well as previously in location-cueing paradigms do not merely reflect the detection and processing of unexpected stimuli. Furthermore, our data suggest that the right IPS and the inferior frontal gyrus are involved in attentional selection and distractor processing of both spatial and nonspatial features.

Postura da mão e imagética motora: um estudo sobre reconhecimento de partes do corpo

OBJECTIVE: Recognition of body parts activates specific somatosensory representations in a way that is similar to motor imagery. These representations are implicitly activated to compare the body with the stimulus. In the present study, we investigate the influence of proprioceptive information relating to body posture on the recognition of body parts (hands). It proposes that this task could be used for rehabilitation of neurological patients. METHODS: Ten right-handed volunteers participated in this experiment. The task was to recognize the handedness of drawings of a hand that were presented in different perspectives and several orientations. For drawings of a right hand, the volunteers pressed the right key, and for drawings of a left hand, they pressed the left key. The volunteers underwent two sessions: one with their hands in a prone posture and the other with their hands in a supine posture. RESULTS: The manual reaction time was longer for perspectives and orientations for which the real movement was difficult to achieve. This showed that, during the task, motor representations were activated to compare the body with the stimulus. Furthermore, the subject's posture had an influence in relation to specific perspectives and orientations. CONCLUSIONS: These results showed that motor representations are activated to compare the body with the stimulus, and that the position of the hand influences this resonance between the stimulus and the body part.