Selective fatigue in the human motor system

Summary If the form of simple movements as well as the muscles involved are coded by place, it should be possible selectively to fatigue form-specific and muscle-specific neurons, whereby muscle-specific units are supposed to control homologous muscles on both sides of the body. In two experiments both kinds of selective fatigue effects were observed by the use of movements of different forms and with different fingers of both hands. These effects showed up in the variability of movement times only, but not in their mean.     

Reconsideration of measurement of error in human motor learning

Human motor learning is often measured by error scores. The convention of using mean absolute error, mean constant error, and variable error shows lack of desirable parsimony and interpretability. This paper provides the background of error measurement and states criticisms of conventional methodology. A parsimonious model of error analysis is provided, along with operationalized interpretations and implications for motor learning. Teaching, interpreting, and using error scores in research may be simplified and facilitated with the model.     

The measurement of speed in motor performance

When the centroid method of factor analysis was applied to two sets of data on athletic performances, three significant factors emerged: strength, velocity, and dead weight. Scores on this speed factor were predicted by the multiple regression technique, the factor loadings on the speed factor being used as the criterion correlations, and these predicted scores were correlated with each of the other variables. When the original tables, augmented by the new speed variable, were refactored, the computed speed factor fell on the speed axis as a primary trait. It is thus shown that it is possible to isolate and measure a factor which appears in variables under consideration only as a compound.Much of the expense of the statistical computations connected with this study was financed by a grant from the Carnegie Foundation for the Advancement of Teaching.     

Complex oscillations in a human motor system

Experiments were performed to investigate the oscillations arising in a human motor system with delayed visual feedback. Eight subjects were instructed to maintain a constant finger position relative to a stationary baseline. The finger displacement was measured using a microdisplacement transducer connected to the index finger, and was displayed on an oscilloscope. Time delays between 40 and 1,500 ms were inserted in the visual feedback loop for 100 s. Results show that, as the time delays increase, irregular rhythms appear with short intermittent periods of regular oscillations. These regular low-frequency oscillations have an amplitude that increases with the time delays and a period that is consistently about 2 to 4 times the time delay. Fast Fourier Transforms (FFT) show a peak between 8 and 12 Hz, corresponding to physiological tremor in half the subjects. No systematic variations in the FFT for the 2 to 15 Hz range were observed as time delay increased. In the 0 to 2 Hz range, the FFT show a consistent increase in power with the time delay. These results indicate that, under the conditions of this experiment, tremor is not affected by time delays in the visuomotor system, and time delays in the visuomotor feedback loop give rise to complex oscillatory behaviors.     

The effect of perceptual information on output interference

Psychonomic Bulletin & Review - Retrieval from episodic memory has consequences (Malmberg, Lehman, Annis, Criss, & Shiffrin, The Psychology of Learning and Motivation, 61;...     

The human operator as a single channel information system

A further experiment is reported on reaction times to stimuli separated by short intervals. On this occasion an auditory stimulus was followed by a visual stimulus. Results indicate that the pattern of delays at short intervals is the same as the pattern of delays when the stimuli are presented in one modality only. This suggests a model of the human operator functioning as a single channel through which information from both sense modalities has to pass before appropriate responses are organized. An attempt is also made to reconcile data with the known facts about the peripheral and central components of reaction time and the possibility that delays are the result of occupation of the channel for a central time plus a central refractory time is suggested.     

Discrete versus continuous stage models of human information processing: in search of partial output

This article introduces a new technique designed to study the flow of information through processing stages in choice reaction time tasks. The technique was designed to determine whether response preparation can begin before stimulus identification is complete ("continuous" models), or if a stimulus must be fully identified prior to any response activation ("discrete" models). To control the information available at various times during stimulus identification, some relevant stimulus characteristics were made easy to discriminate and some were made hard to discriminate. The experimental strategy was to look for effects of partial output based on information conveyed by characteristics that were easy to discriminate. The technique capitalized on the fact, demonstrated in Experiment 1, that preparation of two response fingers on the same hand is more effective than preparation of two response fingers on different hands. The usefulness of partial output was varied by manipulating the assignments of stimuli to responses. For some mappings partial information could contribute to effective response preparation because the responses consistent with partial information were assigned to fingers on the same hand. For other mappings partial information could not contribute to effective response preparation because the responses consistent with partial information were assigned to fingers of different hands. Performance differences between these mappings were considered evidence that partial information about a stimulus was transmitted to response activation processes before the stimulus was uniquely identified, and thus were considered evidence against discrete transmission of information about the stimulus as a whole. A variety of stimulus sets were studied; the results suggest that information is transmitted discretely with respect to stimulus codes, although distinct codes activated by a single stimulus may be transmitted at different times.     

The effects of approach and avoidance motor actions on the elements of creative insight

The authors propose that the nonaffective bodily feedback produced by arm flexion and extension informs individuals about the processing requirements of the situation, leading to the adoption of differential processing styles and thereby influencing creativity. Specifically, the authors predicted that arm flexion would elicit a heuristic processing strategy and bolster insight processes, whereas arm extension would elicit a systematic processing strategy and impair insight processes. To test these predictions, the authors assessed the effects of these motor actions on 3 central elements of creative insight: contextual set-breaking, restructuring, and mental search. As predicted, in 6 experiments, arm flexion, relative to arm extension, facilitated insight-related processes. In a 7th experiment, arm extension, relative to arm flexion, facilitated analytical reasoning, supporting a cognitive tuning interpretation of the findings.     

Deluding the motor system

How do we know that our own actions belong to us? How are we able to distinguish self-generated sensory events from those that arise externally? In this paper, I will briefly discuss experiments that were designed to investigate these questions. In particular, I will review psychophysical and neuroimaging studies that have investigated how we recognise the consequences of our own actions, and why patients with delusions of control confuse self-produced and externally produced actions and sensations. Studies investigating the failure of this 'self-monitoring' mechanism in patients with delusions of control will be discussed in the context of the hypothesis that overactivity in the parietal cortex and the cerebellum contribute to the misattribution of an action to an external source.     

The motor system in simple reaction time experiments

In this paper evidence is presented that the variability of the motor system does not play an important role in the variability of simple reaction time. Many studies refer to this fact which, however, seems contradictory to electrophysiological data. A model is proposed for the operation of the motor system in simple reaction time experiments which consistently links single cell neuronal activity with electromyographic activity and with response time. It appears that the motor system subserving simple reactions consists of many elements which once triggered produce a mechanical response well defined in time despite the fact that the elements themselves show a rather large time jitter.     

The association of motor information and verbal information: a new perspective on the mechanism of the SPT effect

Current perspectives on the mechanism underlying the Subject Performed Task (SPT) effect have not yet reached a consensus. This study investigated whether the association between motor and verbal information is a key factor that explains the SPT effect. Experiment 1 and 2 tested whether motor and verbal retrieval memory performance were different when the association level was varied. Results showed that when subjects used low association learning materials, memory performance in either motor or verbal retrieval condition was significantly better than performance in the combined retrieval condition. Experiment 3 examined whether the level of association between motor and verbal information affects the SPT effect. Results revealed that the SPT effect disappeared when low association learning materials were used. Our findings imply that the high association level between motor and verbal information enables mutual activation of the two information types, leading to improved memory performance.     

The measurement of human oral forces

This paper reviews the types of instruments used and problems encountered in the measurement of human biting forces. A new instrument, developed for this purpose, which employs strain gauges mounted on a cantilever bridge bite element is described. Associated circuitry, which includes a Wheatstone bridge, amplifier, and integrator, is described. The integrator enables the investigator to record accumulative force over time. Biting force values recorded at five different areas of the mouth are presented from 11 male and 8 female Ss.     

Oscillator mechanisms in the human motor system: investigating their properties using the aftercontraction effect

It is proposed that the human motor system is organized to use hardware and/or software non-linear oscillator mechanisms, the output of these oscillators being responsible for driving the limbs via signals to muscle groups. Following earlier theoretical development, it is argued that these muscle groupings act as a unit and themselves are likely to behave as a non-linear system. The attributes of non-linear oscillators are many, and they are potentially significant for the explanation of motor behavior. This paper reviews and presents recent experiments that investigated the properties of muscular aftercontraction. The basic finding shows that subsequent to a period of moderate strain against a fixed surface the treated limb exhibits prolonged involuntary molar oscillations in the plane of the treatment. These results provide for the presence of driving oscillator mechanisms in the human motor apparatus. The mechanisms show generality of action in that directed attention can lead to oscillation of untreated limbs. Overall, the experiments showed that the movements exhibited the mutual interaction, synchronization, and preservation of phase relationships that are fundamental properties of non-linear oscillators. the picture that emerges is that these mechanisms can drive involuntary movements that are richly patterned: like slow versions of voluntary movements. The aftercontraction phenomenon proves to be an excellent tool for research on the oscillatory substrate of human motor organization.     

Organization of rhythmic buccal motor output of Lymnaea stagnalis in the absence of food

The pond snail Lymnaea stagnalis exhibits spontaneous rasping movements in the absence of food which are thought to be involved in food searching activity. Rasping activity is patterned into bouts, separated by periods of quiescence. Recordings from buccal feeding motoneurons in the isolated CNS reveal similar bouts of rhythmic motor output, though the modal cycle period is significantly longer than that shown by intact snails. Log survivorship curves of interval data from both intact animals and isolated CNS indicate that the pattern of motor output is controlled by at least two processes, one generating intervals between rasps within a bout, and the other generating intervals between bouts of rasping. When compared to well-fed individuals, 2-day-starved snails show significant enhancement of the probability function for generation of intervals between rasps within a bout; the function underlying between-bout intervals is not significantly affected.     

Perception of the color red enhances the force and velocity of motor output

The present research examined whether perception of the color red influences basic motor functioning. Prior research on color and motor functioning has been guided by ill-defined theoretical statements, and has been plagued by methodological problems. Drawing on theoretical and empirical work on the threat-behavior link in human and nonhuman animals, we proposed and tested the prediction that perceiving red enhances the force and velocity of motor output. Experiment 1 demonstrated that red, relative to gray (matched to red on lightness), facilitates pinchgrip force. Experiment 2 demonstrated that red, relative to gray (matched to red on lightness) and blue (matched to red on lightness and chroma) facilitates handgrip force and the velocity of that force. These findings clearly establish a link between red and basic motor action, illustrate the importance of rigorous experimental methods when testing color effects, and highlight the need to attend to the functional, as well as aesthetic, value of color.