Is there manual asymmetry in movement preparation?

Manual asymmetry in response preparation was investigated in simple and complex movements by using simple reaction-time tasks. The simple movement consisted of lifting the index finger, while in the complex one subjects reversed direction of movement to hit a switch after reaching for and grasping a tennis ball. Analysis showed that performance with either the right or the left hand was equivalent, with longer latencies for reacting on the complex task in comparison to the simple one. These findings indicate similar capabilities of the right and the left cerebral hemispheres to prepare the motor system for action independently of the spatial requirements of movement.     

Preparatory Set,Response Complexity,and Reaction Latency

The interaction between preparatory set and response complexity was demonstrated in an experiment investigating the reaction latency of discrete arm movements. Following simple finger-lift reaction-time (RT) trials, subjects performed simple and complex versions of a discrete horizontal arm movement under one of two enforced preparatory set conditions. For the simple task, requiring subjects to attend to the components of the response prior to stimulus presentation (enforced motor set) produced significantly shorter RTs than when concentration was on the stimulus (enforced sensory set). However, RT differences for the complex version of the task failed significance. Theoretical implications of the results for Henry’s (1960) memory drum theory of neuromotor reaction were discussed.     

Movement-based compatibility in simple response tasks

Previous studies reported that movement observation affected movement execution. Using one and the same set of responses (i.e., lifting or tapping the finger), correspondence effects were observed for simple responses when the go-signals were similar to the responses (i.e., movies of finger movements) but not when they were dissimilar (i.e., moving squares). The difference was attributed to a higher degree of ideomotor compatibility with visible limb movements. We tried to provide further evidence for ideomotor theory by manipulating the degree to which different responses matched one and the same set of stimuli (drifting sine-wave gratings). To this end, we measured simple reaction time of dynamic (hand movements) or static (key presses) movements in response to the onset of object motion. Object motion and dynamic responses showed ideomotor compatibility without looking alike; however, both stimulus and response involved continuous displacements. Correspondence effects were observed for dynamic responses, but not for static responses.     

Locus of the effect of a distinguishing feature in a memory search task

Subjects memorized one to four 8- or 16-sided random forms in a memory search task. The positive set forms ("yes" response) differed in number of sides from the negative set forms ("no" response) for the different set (DS) group, but this distinguishing feature was not available to the same set (SS) group. Mean reaction time increased as a linear function of log(2) of the positive set size for both groups, but the increase was greater for the SS than the DS group, suggesting that memory search rather than an encoding stage of information processing was influenced by the availability of a distinguishing feature. In a transfer task which followed, new forms were introduced in which the positive and negative set forms differed in number of sides for both groups. In this task, the two groups did not differ in memory search, but in encoding. It was proposed that (a) availability of a distinguishing feature influences search time because the information specifying the number of sides of the set of memorized forms can be used to influence the speed with which individual forms are examined in memory; (b) previous experience with a distinguishing feature influences encoding because the DS group had learned to extract the information specifying the set of memorized forms (not the information specifying individual forms) more efficiently than the SS group.     

The role of emotional context in facilitating imitative actions

In two experiments, we explored whether emotional context influences imitative action tendencies. To this end, we examined how emotional pictures, presented as primes, affect imitative tendencies using a compatibility paradigm. In Experiment 1, when seen index finger movements (lifting or tapping) and pre-instructed finger movements (tapping) were the same (tapping–tapping, compatible trials), participants were faster than when they were different (lifting–tapping, incompatible trials). This compatibility effect was enhanced when the seen finger movement was preceded by negative primes compared with positive or neutral primes. In Experiment 2, using only negative and neutral primes, the influence of negative primes on the compatibility effect was replicated with participants performing two types of pre-instructed finger movements (tapping and lifting). This emotional modulation of the compatibility effect was independent of the participants' trait anxiety level. Moreover, the emotional modulation pertained primarily to the compatible conditions, suggesting facilitated imitation due to negatively valent primes rather than increased interference. We speculate that negative stimuli increase imitative tendencies as a natural response in potential flight-or-fight situations.     

The attentional demands of negation in a memory-scanning task

Subjects were run in a Sternberg recognition memory task modified to occasionally require a transformation prior to response. The transformation was similar to logical negation since onplus or nontransformed trials subjects responded "yes" if the probe was from the current memory set and "no" otherwise, while onminus or transformed trials subjects responded "no" to memory set probes and "yes" to nonmemory set probes. Two models proposed to account for the effects of logical negation were compared: The encoding and comparison model predicts that logical negation requires an additional processing stage, while the capacity sharing model argues that negation adds a processing stage and also retards the rate of memory search. The results indicated that minus probes had 50% larger mean reaction time by set size slopes than the corresponding plus probes. This finding offers clear support for the capacity sharing model.     

The effect of movement amplitude and target diameter on reaction time

Henry's (Henry & Rogers, 1960) memory drum model of neuromotor reaction, which predicts an increased response latency for more complicated movements, was tested by examining the effects of variations in movement amplitude and target diameter on choice RT. RT tended to increase with decreasing target diameter, and varied as a U-shaped function with amplitude. Such findings were in only partial support of the memory of drum notion. The data were discussed in relation to information processing, muscle activation, and subjects' expectations for executing responses along the range of movement amplitude.     

Evidence of Incomplete Motor Programming in Parkinson's Disease

One of the essential questions regarding movement deficits in Parkinson's disease (PD) is whether they stem from impaired selecting and switching among movements, impaired use of predictive information to prepare movement, or impaired execution of movement. PD subjects (n equals 9) and age-matched control subjects (n equals 8) performed a cued, sequential-response RT task. The cue provided either no information, accurate information, or inaccurate information about the upcoming response. PD subjects used predictive information to prepare and to switch among movement sequences normally, but second and third key press latencies were prolonged in comparison with the first key press latency. In Experiments 2 and 3, the effects of choice set and sequence length on key press latencies were examined. These results provide evidence that PD subjects initiate movement before the entire response sequence is prepared. PD does not impair motor programming or execution processes themselves but impairs the smooth coordination of those processes.     

Evidence of Incomplete Motor Programming in Parkinson's Disease

One of the essential questions regarding movement deficits in Parkinson's disease (PD) is whether they stem from impaired selecting and switching among movements, impaired use of predictive information to prepare movement, or impaired execution of movement. PD subjects (n = 9) and age-matched control subjects (n = 8) performed a cued, sequential-response RT task. The cue provided either no information, accurate information, or inaccurate information about the upcoming response. PD subjects used predictive information to prepare and to switch among movement sequences normally, but second and third key press latencies were prolonged in comparison with the first key press latency. In Experiments 2 and 3, the effects of choice set and sequence length on key press latencies were examined. These results provide evidence that PD subjects initiate movement before the entire response sequence is prepared. PD does not impair motor programming or execution processes themselves but impairs the smooth coordination of those processes.     

Effects of type of responding on memory/visual search: Responding just “yes” or just “no” can lead to inflexible performance

Interactions of stimulus consistency and type of responding were examined during perceptual learning. Subjects performed hybrid memory-visual search tasks over extended consistent and varied mapping practice. Response conditions required subjects to respond to both the presence and absence of a target, only when a target was present or only when a target was not present. After training, the subjects were transferred to a different response condition. The results indicate that: (1) performance on search tasks with stimuli that are variably mapped show no qualitative changes attributable to manipulation of response format; (2) improvement due to consistent mapping (CM) practice is attenuated in the no-only response condition; (3) yes-only CM training attenuates the subjects ability to transfer to no-only responding; and (4) yes/no CM training leads to the greatest improvement and transfer when compared with other responding conditions. The practice and transfer data support and extend previous research investigating effects of response set in memory/visual search and help to delineate factors that facilitate or inhibit reduction of load effects in memory and visual search.     

Aging and the restructuring of precued movements

A precue paradigm was used to examine the time it takes to restructure a planned motor response. Two groups of subjects, a young group and an elderly group, performed an aiming task in which 75% of the trials involved no change of movement parameters. On remaining trials, subjects had to change one or more of the movement parameters. Elderly subjects had slower reaction times (RTs), movement times, and made more errors in both conditions. Elderly subjects had proportionally longer RTs overall, independent of restructuring a movement plan. Preparation of arm and direction also exhibited a proportional increase in RT. However, differential aging effects were found for preparation of extent. Elderly subjects were slower preparing short movements compared with long movements, whereas young subjects showed the opposite trend. These results suggest that with advancing age, operations concerned with movement-plan restructuring for arm and direction undergo change in processing rate, whereas operations for extent undergo more extensive alteration.     

The Attention Demands of Movements

The probe technique has been employed extensively to measure the attention demands of movement control. Inherent in any RT paradigm is the potential confounding effect of anticipation. Experiment 1 studied this problem by varying probe frequency (or, conversely, catch-trial frequency) for three independent groups of subjects performing the same movement. Probe frequencies of one-third and two-thirds produced V-shaped curves of probe RT plotted against probe position within the movement, while a three-thirds condition was described by a negatively sloped linear function. Because of the different shaped curves it was recommended that a two-thirds frequency be adopted by all researchers in this area. Experiments 2 and 3 looked at the effects of movement length and movement time on the attention demands of movement. Shorter (11-cm) movements were more attention demanding in the middle of the movement than the longer (50-cm) movements, but movement time had no effect.     

The effect of an extraneous added memory set on item recognition: A test of parallel-dependent vs. serial-comparison models

The linear increase in response time (RT) in item recognition as a function of memory set size may be attributed either to increased memory search, as in Sternberg’s serial-comparison model, or to increased interference and competition for a limited processing capacity, as in a parallel-dependent model. An additional memory load was imposed on the normal item recognition task. If the normal task involved letters, the additional task involved digits, or vice versa. The added set was presented before and tested after the normal core set was presented and tested. Across the four trial blocks, the subjects did come to dissociate the two memory sets, but this could be due as much to directed rehearsal as to directed search when other results, including the subjects’ postsession reports, are considered. Other findings, such as the higher error rate and shorter RT for positive than negative trials, seem to reflect differences in effective trace strength, and thus are consistent with the parallel-dependent model.     

Sequence of preparatory set for response movement

Electromyographic reaction times (EMG-RTs) of the right biceps brachii muscle were examined for two movement patterns, elbow flexion and forearm supination, in 8 healthy male subjects under simple and complex RT conditions with varied preparatory intervals (PIs): 0, 200, 400, 600, and 800 msec. In the simple RT condition, the subject was informed of the movement patterns to be performed prior to beginning the trials. In the complex RT condition the subject had to choose one of the two movement patterns at the time of the presentation of a warning signal. The results indicated that: (1) compared with the simple RT condition a delay of about 100 msec. in over-all mean EMG-RT was observed at PI = 0 msec. in the complex RT condition; (2) the difference of over-all mean EMG-RT between the two RT conditions disappeared when PI = 400 msec.; and (3) the difference in EMG-RTs between flexion and supination in the complex RT condition became the same as that in the simple RT condition when PI = 700 msec. It is assumed that the preparatory set for response movements is organized in an order, resulting in the differentiation of RT.     

Effects of same-category and different-category extraneous memory sets on item recognition

In a study designed to distinguish between parallel and serial models of performance on Sternberg’s item recognition task, Krueger (1975) presented subjects with a memory set (the “added” set) followed by a second (“core”) set, a probe to the core set, and finally a probe to the added set. Response latency (RT) to both the core- and added-set probes initially increased with the size of the extraneous set. Over successive blocks of trials, the effect of the size of the extraneous set diminished. In Experiment 1 of the present study, Krueger’s basic procedures were replicated with results similar to those he reported for early trials. Experiment 2 was a variation on the added-set procedure. Rather than the memory sets’ being drawn from different categories (letters and digits), both sets consisted of digits. On half of the negative trials for both the core and the added tasks, the probe was drawn from the extraneous set, forcing the subjects to separate the two sets. Although RT on the core task did not increase with the size of the added set, there was an increase in RT to the added set with increases in core-set size, a finding inconsistent with the serial search model     

Simple movement imitation: Are kinematic features sufficient to map perceptions into actions?

The aim of this study was to pinpoint the nature of the visual features used in the automatic mapping of perceived movements into similar executed movements, following the direct matching hypothesis. In Experiment 1 subjects imitated the lifting of one of two fingers, presented with different orientations. As predicted, stimuli which were further rotated away from the posture of the executing hand elicited slower reaction times. In Experiment 2, we verified that this orientation effect was not a purely perceptual effect by presenting the same stimuli but asking subjects to respond verbally. No orientation effect was found using a verbal response. In Experiment 3, we replaced the moving fingers by two arbitrary objects moving with the trajectories of the finger tips of Experiment 1. The same orientation effect as in Experiment 1 was observed. We conclude that in this experiment participants are using purely kinematic features to map perceived into executed movements.     

Mutual Interactions Between Speech and Finger Movements

Speech output and finger movements were recorded as right-handed males repeated a syllable while making cyclical finger movements in three experimental conditions: (a) maintaining constant amplitude in both response systems; (b) alternating speech amplitude while attempting to maintain constant finger movement amplitude; and (c) alternating finger movement amplitude while attempting to maintain constant speech amplitude. Observations showed that output of the two response systems was coupled (one syllable was uttered with each finger movement) and entrained in amplitude (the amplitude pattern of the response that the subject attempted to keep constant followed that of the concurrently-active amplitude-modulated response).

These interactions were bidirectional and were present with both left-handed and right-handed finger movements. The interactions are more extensive and subtle than mere interference with one response system by the other, and apparently do not depend on anatomical overlap of the responding neural systems.     

Premovement facilitation of corticospinal excitability before simple and sequential movement

The purpose of this study was to investigate whether premovement facilitation of corticospinal excitability before sequential movement was different from that before simple movement. Each of 7 participants who performed choice reaction tasks with the right hand pressed a force transducer with the index finger in response to a start cue or pressed the transducers sequentially with the index finger, little finger, thumb, little finger, and index finger. Transcranial magnetic stimulation was delivered to the left motor cortex before the electromyographic burst in the first dorsal interosseous muscle and motor evoked potentials were recorded from the first dorsal interosseous muscle. The amplitude of the motor-evoked potential increased as its onset got closer to the onset of the electromyographic burst. The increase before the sequential movement was larger and began earlier than that before the simple movement. These findings indicate that premovement facilitation of corticospinal excitability is different in magnitude and timing between sequential and simple movements.     

Vision,proprioception and corollary discharge in a movement recall test

Movement recall was investigated in relation to the sensory processes involved in a triangle drawing task.Forty subjects in two groups, one with and one without visual feedback, performed a recall task involving movements of their index finger. All subjects attended different experimental sessions in which (1) all proprioceptive feedback was eliminated by the ischaemic block technique, (2) muscle spindle feedback was distorted by vibration of the muscles and tendons involved in the movement, and (3) proprioceptive feedback was normal.Within each session subjects were required firstly to recall triangular movements made for them passively by the experimenter, and secondly, to recall movements they had made actively. Results indicated comparable accuracy in recall of active movements in all conditions, and a decrement in passive recall dependent on the availability of the alternative sources of feedback. The results indicated a process of integrated contribution of all inputs to the perception of movement; redundancy in information when all channels are available; and a role of corollary discharge in recall of movements.     

Effect of directional response variables on eye-hand reaction times and decision time

To determine if direction of response affects reaction time, we measured the time for hand response to a visual stimulus, using a sensitive, microprocessor-based testing device to determine simple reaction time (RT), choice RT, and decision time. Mean simple RT was 207 +/- 3.7 msec. (mean +/- SEM); mean choice RT was 268 +/- 4.2 msec; and mean decision time was 61 msec. No differences were noted for leftward versus rightward movements, or midline versus lateral movements. Choice RT increased by 1.49 msec./yr. of age. Simple RT increased significantly with age for the nondominant hand, but not for the dominant hand. Right-handed subjects were more rapid with the dominant hand for choice RT. We conclude that dominance of hand tested and test initiation mechanism have major effects, but direction of movement in the lateral plane has little effect on reaction time.