Anticipatory Movements Research Articles

Organization of local anticipatory movements in single step initiation

The study deals with the segmental organization of single- and multi-step walking. Local (segmental) and global (center of gravity) anticipatory movements associated with the initiation of the stepping movement were investigated in 5 normal subjects. Each subject performed a single-step walking task under three conditions of step velocity. Global anticipatory phenomena were indicated by the acceleration of the center of gravity and displacement of the center of foot pressure. Local anticipatory movements, i.e. the accelerations of trunk, shoulders, hips and shanks were recorded simultaneously. The biomechanical data suggest that there are two distinct parts in the anticipatory phase. The earlier correspond to the static postural changes, which are correlated to the velocity of the forthcoming movements. As in multi-step walking, global and local accelerations are specific to the forthcoming movement. The latter part aims to counterbalance the disruption induced by heel-off and is related to postural necessities. These results suggest that the same parameters are programmed in the execution of the single- or multi-step walking process.

Express saccades: the effects of spatial and temporal uncertainty

Once trained to make express saccades, monkeys continue to make express saccades when there is a high level of uncertainty about both the location and the time of onset of a peripheral target. Providing additional information about the location and the time of onset of a peripheral target does not increase the frequency of occurrence of short latency saccades. Furthermore, the metrics of saccades with express latencies are typical of visually-guided saccades, rather than anticipatory movements or saccades to the remembered location of a target. Finally, practice on the gap paradigm restricted to one target location always viewed from the same initial eye position does not increase the probability of producing express saccades to the same target from other initial eye positions. Instead, the practice effect is specific to targets that have the same relative location, regardless of initial eye position.

Compensatory muscle activity for sitting posture during upper extremity task performance in paraplegic persons

Compensation for the loss of postural activity of the erector spinae (ES) muscle in spinal cord injured (SCI) subjects was investigated. All SCI subjects had clinically complete lesions below the T3 level. Body disbalance was invoked by requiring sitting subjects to execute reaching movements over individually predetermined distances in a horizontal plane. Myoelectric activity of the latissimus dorsi (LD) muscle and the trapezius pars ascendens (TPA) muscle both in the SCI subjects and in controls was recorded. The body disbalance was measured in terms of changes in the position of the body centre of gravity. The effects of anticipation for body displacement were examined by cuing the direction of the reaching movement. Our results indicate that paraplegic subjects use both LD and TPA to stabilize their sitting posture, in contrast to non-disabled persons. Secondly, the movement anticipation is in general slower in persons with paraplegia. Furthermore, the paraplegic subjects showed considerable impairments concerning the processing of precued information prior to a goal-directed upper extremity movement.

Conditioning to time: Evidence for a role of hippocampus from unit recording

Unit activity of the dorsal hippocampus was recorded in partially restrained but awake and undrugged rats during a “conditioning to time”. In this type of conditioning, only one stimulus, the equivalent of the unconditioned stimulus of the usual procedures, is used. It is delivered at a constant interval which, in principle, is the conditioned stimulus. In our experiments, the unconditioned stimulus was a mechanical stimulation of a vibrissa; two successive unconditioned stimuli were separated by a 24-s interval. In 11/18 rats, anticipatory movements of a “trained” vibrissa developed at the end of the interstimulus interval. In a number of cases, in parallel to this conditioned behavior, there was a significant change in unit activity, either an increase or a decrease, during the last third of the interstimulus interval. Controls showed that these changes in unit activity did not merely reflect modifications of arousal state or of vibrissa and body movements. From autocorrelograms, it appeared that anticipatory increases in unit activity were associated with the development of a bursting mode of discharge. These data constitute one of the rare examples of a neurophysiological correlate of a “conditioning to time” at the unit Ievel and the first recorded from the dorsal hippocampus of rats.

DIFFERENTIAL STARCH DEPOSITION: A ‘MEMORY’ HYPOTHESIS FOR NOCTURNAL LEAF MOVEMENTS IN THE SUN‐TRACKING SPECIES LAVATERA CRETICA L.

SummaryOblique illumination of the lamina of Lavatera cretica produces asymmetrical deposits of starch as a function of light‐shadow patterns owing to surface irregularities. Asymmetrical deposits, produced immediately after sunrise each day, are believed stored until shortly before the next sunrise. During daytime tracking, deposits are evenly symmetrical. Overnight conversion of these even deposits is believed to continue for most of the night. Shortly before sunrise, however, only residual asymmetrical deposits remain to be converted. Resulting solute asymmetries in the translocation stream are believed to trigger turgor gradients in the pulvinus, so producing anticipatory movements just before dawn. Pre‐dawn movements thus actually repeat those accompanying the previous post‐dawn oblique lighting. Changing solute gradients across the pulvinar phloem, originating from shifts in sunlight direction, are cited as the probable cause of normal tracking adjustments.

Coincidence anticipation of young normal and handicapped children.

Two coincident-timing experiments examined the role of three different target velocities and display extents and three age levels of normal and retarded children. Subjects made a ballistic response to a target moving horizontally across their visual field. In the first experiment there were generally no clear differences between normal and retarded children on the task, with subjects having difficulty for both the slow and fast target speeds. In the second experiment, with target velocity held constant, no significant differences were reported between normal and handicapped children, although the longer the subjects were allowed to view the target the more accurate they were. The data were discussed in terms of the response strategies to perform anticipatory ballistic movements. An ecological issue was raised which suggested that children as well as adults make their most accurate anticipations when confronted with velocity problems that have been experienced in their everyday world.

Neuron activity in rat hippocampus and motor cortex during discrimination reversal

DISTERHOFT, J. F. AND M. SEGAL. Neuron activity in rat hippocampus and motor cortex during discrimination reversal. BRAIN RES. BULL. 3(6) 583–588, 1978.—Chronic unit activity and gross movement were recorded from rats during two discrimination reversals in a classical appetitive conditioning situation. The anticipatory movement decreased in response to the former CS + tone and increased to the previous CS − tone after each reversal. Hippocampus and motor cortex were differently related to these two kinds of behavioral change. Response rates of hippocampal neurons were more closely related to the increased movement response to the former CS − which now signaled food. Motor cortex neuron responses were more closely correlated with the decrease in movement responses to the former CS + which became neutral after the reversal. It appeared that hippocampal neurons could have been involved in one cognitive aspect of the situation, motor cortex neurons in another. The data were related to current functional concepts of these brain regions.

Articulatory movements in VCV sequences.

The purpose of this experiment was to study both the timing and positional properties of articulatory movements in VCV utterances. Conventional cinefluorographic techniques were used to track the movements of the upper lip, lower lip, jaw, tongue tip, and tongue body of two speakers who read randomized lists of VCV utterances containing the vowels /i,a,u/ and the consonants /p,t,k/, in all possible combinations. Results showed that the timing of articulatory movements in a VCV sequence are constrained by the intervocalic consonant, even if the gesture for the consonant is not a contradictory one. Anticipatory movements toward the second vowel always begin during the closure period of the intervocalic consonant. The appearance of carry over coarticulation effects depends on the phonetic identity of the particular segment or degree of involvement of the articulator. Carry over effects, like anticipatory effects, did not extend beyond an immediately adjacent segment. These findings suggest that the rules governing the segmental input to a speech string might be simpler than present models suggest.

Aspects of lingual coarticulation

This study utilized high speed X-ray films (cinefluorography) to study RL coarticulations of tongue apex and tongue dorsum. Subjects spoke C 1 C 2 V and VC 1 C 2 sequences comprised of combinations of tense and lax consonant clusters and vowels. Measurements of lingual movements were obtained from cineframe tracings. Results indicate RL anticipatory movements of the tongue dorsum in C 1 C 2 V sequences, anticipatory movements toward V began on C 1 in 30 % of the cases. In VC 1 C 2 sequences, the tongue apex began RL anticipatory movements toward C 2 during the steady-state vowel segment in approximately 44% of the cases. Perturbations of tongue movement related to labial closures and subsequent oral pressure build up was observed. The articulatory feature tense/lax did not vary systematically with the amount and extent of coarticulatory RL effects. Results were related to certain hypotheses concerning articulation behavior.