Motor Response Time Research Articles

Speed of memory scanning is not affected in early HIV-1 infection.

Thirty-seven nondemented HIV-seropositive and 17 seronegative control subjects were administered the Sternberg speed of memory scanning task, a procedure frequently employed to study mental slowing in patients with subcortical dementing disorders. Experimental and control subjects did not differ in speed of memory scanning, as indexed by the slopes of set size-reaction time functions, nor on mean 0-intercepts for the RT functions, which index stimulus detection and motor response time. Intercept values were significantly greater for subjects with a positive alcohol abuse history and for subjects with greater self-reported depression, but slopes were not significantly correlated with substance abuse history or psychological distress. Cognitive slowing in early HIV-1 infection is not a nonspecific effect observed across all measures of information processing speed. Underlying component functions measured must be carefully considered when selecting reaction time tasks for study with HIV-seropositive subjects. The term "subcortical" dementia may be too general a descriptor, and RT task performance may provide an alternative basis for classification of dementia types.

Effects of Monocular Occlusion on Neural and Motor Response Times for Two-Dimensional Stimuli

Previous studies have shown that there are advantages associated with the simultaneous use of both eyes to view two-dimensional stimuli. To investigate further this binocular advantage, three experiments were conducted using male and female names presented on a video display as stimuli. In the first experiment, simple reaction times (RT's) were found to increase by about 6% as a result of monocular occlusion. In the second experiment, visual evoked response (VER) and P300 implicit times were also found to increase as a result of occlusion. The third experiment confirmed these results and investigated the sensitivity of evoked potential techniques to changes in stimulus complexity. The three experiments demonstrate that monocular occlusion does have a significant effect on processing speed for two-dimensional visual stimuli. The major portion of this effect (62%) is manifest at the level of the visual cortex, and is not perceived by subjects as significantly increasing the mental workload associated with generating responses to these stimuli.

Relationship between response time and falls among stroke patients undergoing physical rehabilitation

This study evaluated the influence of simple motor response time on the risk of falling among 202 stroke patients admitted to a rehabilitation hospital. All patients were tested within 2 weeks of admission to hospital on a computerized response time task. Visual stimuli were presented centrally, in the left and in the right visual fields. Three response times were calculated for each patient. Using the response time from the most impaired field, the 95 fallers generally had slower response times than did the 107 non-fallers (on average, 2.50 s vs. 1.93 s). However, response time was only significantly slower when the visual stimuli were presented in the left visual field (on average, 1.99 s vs. 1.39 s). As response time increased so did the risk of falling, demonstrating a dose-response effect. In comparison to patients with 'normal' response times (0.0-0.50 s), patients with response times between 2.00 s and 2.50 s had a sevenfold increase in the risk of falling. Previous research has shown that the response time of stroke patients improves over time, indicating that response time may be one factor influencing falls which is indeed modifiable. A suggestion is made to include the assessment of response time as a screening tool for identifying persons at elevated risk to fall as it is easily and accurately measured and as interventions aimed at improving response time are available.

Change in Response Time of Stroke Patients and Controls during Rehabilitation

In this study we investigated motor response times of stroke patients at admission to a rehabilitation hospital and again after 6 wk of hospitalization. A prospective comparative study was carried out on 164 stroke patients; 48 hospitalized patients served as controls. Mean motor response times to visual stimuli presented in the left and right visual fields and to centrally presented stimuli were studied. The principle finding was that stroke patients improved significantly in their response times from initial to final evaluation. While at initial assessment they performed significantly more slowly than controls, by final assessment the response times of the two groups did not differ. Visual hemineglect influenced change in response time differentially depending on side of lesion: right hemisphere lesion patients with neglect improved, whereas left hemisphere lesion patients with neglect actually deteriorated. The presence of depression influenced right hemisphere lesion patients' response times and change in response times but it did not have any influence for left hemisphere lesion patients. The findings that response time generally improved during rehabilitation has important implications for the treatment of individuals with brain injury. It will be important to identify therapeutic practices which will be effective in the remediation of response time for all patients. Ultimately the goal of intervening in slow response time is to improve performance of functional activities which are influenced by an individual's ability to respond to visual stimuli.

Gradual Specification of Response Amplitude in Human Tracking Performance

These experiments examine how human subjects use information from a target to trigger a response and to specify its trajectory. We first determined if response initiation is predicated on the prior specification of response amplitude by examining the latencies and trajectories of impulses of isometric elbow flexion aimed to one of three visual targets. We varied target predictability (simple versus choice), the urgency with which the response was required, and the level of practice. With practice, subjects could respond to unpredictable targets with the same latency as to predictable ones; the range of response amplitudes was, however, always constricted. This central tendency bias disappeared when subjects were allowed long latencies to respond to the target, suggesting that with urgency, subjects can respond before specification is complete. To determine the time course of specification, the subjects were trained to initiate force impulses in synchrony with the last of a series of predictable tones. They also attempted to match the amplitude of their force impulses to one of three unpredictable visual targets presented at randomly varying times (50-400 ms) prior to the synchronizing tone. At the shortest stimulus-response intervals, before target information could be processed, the amplitudes of responses to all targets were clustered around that of the middle-sized target. Then, as the stimulus-response interval increased, response amplitudes gradually converged upon their specific targets. Specification started at stimulus-response intervals of about 100 ms and extended until about 350 ms.(ABSTRACT TRUNCATED AT 250 WORDS)

Prefrontal representation of stimulus attributes during delay tasks. I. Unit activity in cross-temporal integration of sensory and sensory-motor information

The activity of 294 single units was recorded from the dorsolateral prefrontal cortex of monkeys performing two visual discrimination tasks with delayed response. One task, delayed matching-to-sample (DMS), required memory of a colored cue for later (18 s) matching and choice of color; the cue did not connote the location of the delayed response. The other task, delayed conditional position discrimination (DCPD), required memory of a colored cue for later (18 s) choice of spatial response; the cue did connote delayed-response location. All 4 cues (red and green in DMS, yellow and blue in DCPD) were isoluminous and appeared in identical location at trial start. Differential unit reactions to the two DCPD cues were more common than those to the two DMS cues (samples). During the delay period, 15% of all units showed, in one task or the other, differential discharge depending on the cue. In DCPD, a large proportion of the units showing direction-related activity at the time of motor response also reacted with a firing frequency change to one or both (spatially identical) trial-initiating cues. Some units showed coherence of cue-related and response-related changes in accord with the behavioral association between color and direction of response (i.e., yellow-right, blue-left). The reactivity of some units was correlated with the behavioral performance of the tasks in terms of correctness or incorrectness of response. The results indicate that, during visual delay tasks, neurons in the dorsolateral prefrontal cortex may process both spatial and non-spatial information. Because of their protracted differential discharge between cue and response (i.e., during the delay), some units seem involved in the transfer of sensory information across time. These findings suggest the role of prefrontal neurons in the representation of multiple attributes of sensory stimuli, including their associated motor connotations, and the overlap of the cortical representations of different attributes. They are also consistent with the role of the prefrontal cortex in the cross-temporal mediation of sensory-motor contingencies and, therefore, the temporal organization of behavior.

Réponses verbales et motrices à des mots et à des dessins

Summary : Verbal and motor response times to words and pictures. The fact that it takes longer to name a picture than to read a word is now a standard resuit in experimental psychology. This study compared the pattern of picture versus word processing with verbal responses and motor responses to simple geometric figures and the equivalent words at various stimulus presentation times. The pattern of effects with motor responses was the opposite of that with verbal responses, motor reaction times being longer to the words than to the figures at all presentation times. We conclude that when a motor response is required to a word, the subject must translate a phonetic code into a semanticfspatial code in order to match the word with the corresponding response key. The figure stimuli are automatically given a semantic code and do not therefore require a supplementary processing stage to give a motor response. However, if a verbal response is required, the semantic code attributed to the figure stimuli must be translated into a phonetic code thus entailing a supplementary processing stage compared to the word stimuli which are automatically attributed a phonetic code. Key words : picture-word perception, motor response.

Reaction time in cerebrovascular disease

One hundred and eight patients have been investigated clinically, by computer tomography and by measuring the reaction time (RT). Thirty six controls without histories of brain disease, normal psychiatric findings and the same mean age as the other groups, were compared with 37 stroke patients without and 35 stroke patients with dementia. The dementia was defined clinically and by a psychological test (WAIS) and by applying a deterioration index (Baxa and Pakesch, 1972). The RT was measured by the Wiener Test system (Schuhfried) using eight optic, eight acoustic and eight choice signals at random for both hands, by adding the decision and motor response time to perform a task. The stroke patients as a whole (72) had significantly longer RT than the controls. When the stroke group was divided according to degree of dementia, in almost all the measurements the RT was significantly longer in the demented group. The localisation of the infarcts with RT with dominant or non-dominant hemisphere lesions showed no significant correlation, despite the fact that RT was longer in patients with infarcts in the dominant hemisphere or in those having bilateral lesions. When IQ was measured, only a few significant correlations were found between IQ and RT. In almost all the measurements a significant correlation between RT and OI was found. It was therefore concluded that RT is an easily applicable method for stroke patients in the differentiation between dementia and normal intellectual functioning, and a useful instrument for evaluating the long-term course of intellectual impairment in patients with stroke.

The property of contingent negative variation (CNV) in psychiatric patients: schizophrenia and neurosis.

The CNV parameters (amplitude and morphology) and the relationship between CNV parameters and performances (motor response time) were studied on schizophrenics (15 subjects), neurotics (15 subjects) and normal controls (30 subjects divided into 2 groups) in order to clarify the property of CNV in psychiatric patients. Also, the relationship between CNV and personality traits was investigated in neurotics. Since it has been known that age, sex and psychoactive drugs influence the CNV genesis in normal subjects, the control group method was used for these factors in this study. The results obtained were as follows: 1) Mean amplitudes of CNV's for schizophrenics and neurotics in each session of control, nonresponse and recovery tended to be lower than those for normal controls. Significant differences were found between schizophrenics and normal controls. 2) Correlations between CNV amplitude and response time in schizophrenics tended to be positive, while normal controls showed significantly high negative correlations. These findings were discussed from the viewpoint of the arousal theory of CNV genesis. 3) For the neurotic patients, the personality variables appeared to influence CNV amplitude. 4) Type B-CNV was most frequently seen in all sessions for normal controls. Schizophrenics and neurotics tended to show the increment of type P-CNV in nonresponse sessions without a motor response. 5) "Field Dependency" type-CNV was not found in psychiatric patients. This result did not correspond with the data reported by other investigators. 6) Type III- and type IV-prolonged CNV's appeared almost especially in schizophrenics although type II-CNV was observed in all groups. The mechanism of genesis of the prolonged CNV's was discussed.

Relationships of hippocampal theta cycles with bar pressing during self-stimulation

Previous reports have demonstrated a relationship between hippocampal rhythmical slow activity (theta) and movement, and have suggested that rhythmical movements tend to occur during certain phase of theta. Therefore, the relationships between theta cycles and voluntary motor activity were investigated. Bar pressing for electrical brain stimulation provided the reference to relate hippocampal activity. Ongoing theta increased in amplitude and frequency before and after pressing. Periodic waves preceding and following pressing. These waves only appear if the presses occur at particular phases of the theta cycles. They gradually disappeared during sessions lasting 4 to 8 hr. Light weights (<90 g) added to the lever did not alter theta, but heavier weights (> 90 g) produced averages without periodic waves and with movement-related potentials. Introduction of a delay between pressing and electrical stimulation delayed evoked potentials, while averaging indicated that periodical waves persisted before and after bar pressing. Total lesions of the septum or superior fornix abolished theta and increased the frequency of self stimulation. In animals with partial lesions, theta reappeared during pressing. The above results indicating that the rats tended to lever press during particular phases of theta, suggest that phase-locked theta may be a corollary of motor mechanisms, and perhaps of the timing of motor responses.

Oral pressure and laryngeal control

It is not clear from studies of larynx movement during stop production that the larynx is perturbed up for voiceless stops or down for voiced stops. One would expect it is the latter, however, since larynx lowering would provide a slight increase in oral cavity volume and would thus help to prolong the pressure difference across the glottis necessary for voicing. A test was made to see whether subjects during continuous phonation would lower the larynx in response to an artificially induced oral pressure buildup. Three subjects were used. Vertical larynx movement was recorded using the thyroumbrometer while a valving device inserted in the subject's mouth simulated an oral closure at random intervals. Valve closure resulted in a significant lowering for all three subjects. The fastest response times (the time between valve closure and the beginning of larynx lowering) approached the lower limits of motor response times associated with voluntary movement. The results indicate the larynx can be lowered during stops in order to prolong phonation. However, the magnitude of this delay in effecting this is large enough to suggest that if a similar lowering of the larynx occurs on voiced stops during speech, it must be an active preprogrammed gesture, not a passive compensatory response to oral pressure build‐up. [This research was supported by a NSF grant to the Phonology Laboratory, University of California, Berkeley, and by a NIDR postdoctoral fellowship at the Department of Oral Biology, University of Connecticut Health Center, Farmington, CT.]

Between-Days Consistency in Personal Tempo

Between-days performance of repetitive movements at a self-paced tempo was studied. 60 Ss performed an accuracy task involving successive arm swings at an individually chosen tempo on each of 2 consecutive days. Between-days correlations for Ss' selected tempos of performance and for within- S variance in motor response times indicated that personal tempo is at least a moderately stable attribute.

Preferred tempo in performance of repetitive movements.

Within- and between-S variability in performance of repetitive movements at a self-paced tempo was studied. Male and female Ss (Ns = 75) performed 36 consecutive arm swings at an individually chosen tempo. Differences between Ss' selected tempos of performance were considerably greater than the amount of variation in Ss' motor response times, indicating that individuals have preferred tempos of voluntary movement which differ from those of other individuals. No sex differences were evidenced in either preferred tempo or consistency of performance.

The timing of interresponse intervals

Analogs of models of duration discrimination are here related to the timing of discrete motor responses. The measure of interest is the variability in duration of intervals collected in short interval reproduction tasks. For data from a Morse key-tapping task, it is shown that, taken separately, neither of the models described can completely account for the relation between the mean and the variance of the interresponse intervals.

Response delays and the timing of discrete motor responses

A model for the timing of repetitive discrete motor responses is proposed, and a prediction of negative dependency between successive interresponse intervals is confirmed by data from a Morse key tapping task. A method that makes use of the first-order serial correlation between interresponse intervals is used to distinguish between variance due to a timekeeping process and variance in motor response delays subsequent to the timekeeper. These two quantities are examined as a function of mean interresponse interval.

Proprioception and the timing of motor responses.

Proprioception and the timing of motor responses.

A Test of the Adams-Creamer Decay Hypothesis for the Timing of Motor Responses

The Adams-Creamer hypothesis states that S uses the decay of proprioceptive feedback from an early portion of a movement to cue a timed response at some later time. This hypothesis was tested by creating passive left-arm movement in one group and withholding it from another, and having Ss make a right-hand response when exactly 2.0 sec. had elapsed since the end of the movement Ss with left-arm feedback had less absolute and algebraic error, and greater within-S consistency than did the no-movement control Ss and, when KR was withdrawn, Ss with left-arm movement regressed less than did Ss without the left-arm movement, which provided 2 lines of support for the decay hypothesis.

Proprioception as a mediator in the timing of motor responses.

The hypothesis that proprioceptive feedback from early portions of a total movement may serve as a cue for the anticipation and timing of a later portion was tested using 48 5s. The right-hand task involved anticipation (with no preview) of the coincidence of a moving and a stationary pointer, and proprioceptive feedback was manipulated by having 5s make a minimal movement or a small or large rotary movement with the left hand during the interval to be timed. Although neither absolute nor algebraic error was affected by the treatments, the number of beneficial anticipations (absolute errors less than 133 msec.) was significantly larger for intermediate than for minimal left-arm activity, supporting the view that proprioceptive feedback serves as a mediator in tasks requiring precise anticipation and timing.

An electrophysiological method for the study of binocular rivalry

A technique is described for recording cortical evoked responses from human Ss in binocular rivalry. Each target is illuminated with flickering light at different frequencies upon a steady background. While the S continuously indicates with a response key which target he is seeing, the cortical responses are tape recorded. The tape recording is later analyzed by average response computer separately for each eye, seeing and not seeing. This simultaneous record of the functioning of both eyes eliminates confounding variables found in earlier methods. Controls are included for rivalry changes during a stimulus cycle and for S motor response time.