Biomedical subjects

S M Pellis

Publications and source records attributed to S M Pellis.

At least 37 records · Page 2Linked to original sources

PubMed1996

Spatio-temporal impairments in limb and body movements during righting in an hemiparkinsonian rat analogue: relevance to axial apraxia in humans.

Humans with Parkinson's disease (PD) often have problems in righting themselves, in that they have difficulty in recruiting their axial musculature to rotate the body to prone. Since this "axial apraxia' is not ameliorated by L-DOPA therapy, it has been concluded that dopamine (DA) does not play a role in recruiting axial rotation of the body [14]. This hypothesis was tested by comparing the righting of rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the substantia nigra (SN) with that of intact rats. Body-on-body righting, where asymmetrical tactile stimulation of the body initiates hindquarter righting, was used to specifically test tactile righting independently of righting triggered or influenced by other sensory systems. In this behavioral test, rats are placed on their sides, their forequarters are held down and their hindquarters released. The DA-depleted rats took longer to begin righting, to complete righting, and used more limb action to right themselves than did control rats. These findings suggest that for this tactile based form of righting, DA-depletion produces axial apraxia. However, frame-by-frame analysis of righting sequences of DA-depleted rats showed that pelvis-led axial rotation could occur, but the spatio-temporal relationship between body and limb movements was disorganized. Therefore, following DA-depletion axial apraxia-like deficits appear to arise from sensorimotor disruption. This raises the issue of whether the axial apraxia in PD patients arises from damage to systems beyond the nigrostriatal DA system, or from interference with sensorimotor integration that is not ameliorated by replacement therapy.

Animals↗

PubMed1996

Visual modulation of air righting by rats involves calculation of time-to-impact, but does not require the detection of the looming stimulus of the approaching ground.

Rats do not visually trigger righting when falling supine in the air. They can, however, use vision to modulate the time of onset of air righting depending upon the height from the ground from which they are dropped. That is, the shorter the height, the quicker they begin to right. The visual cortex has been shown not to be necessary for such modulation; however, such modulation is absent if the superior colliculus is damaged. It is known that the superior colliculus has cells that respond to looming stimuli, and this could be the mechanism for modulation during air righting. In this study, 3 experiments were conducted to test this possibility. The evidence from all 3 suggests that something other than detecting a looming stimulus (i.e., the oncoming ground) is involved in the rats' determination of when to initiate righting. Expt. 1 showed that the ability to modulate the onset of air righting visually is not mature until adulthood (> 80 days). Yet young rats do respond to looming stimuli. Exp. 2 showed that the ability to modulate the onset of air righting requires both eyes. One eye should be sufficient to detect a looming stimulus. Expt. 3 showed that the rats require visual information prior to being dropped, not after, in order to modulate the onset of air righting. If the looming stimulus were the triggering stimulus, then this would be detected after, not before, being dropped. These findings suggest that the rats' ability to calculate the time-to-impact when falling involves a more complex calculation than simply detecting the presence of a looming stimulus.

Aging↗

PubMed1996

Skilled forelimb movements in prey catching and in reaching by rats (Rattus norvegicus) and opossums (Monodelphis domestica): relations to anatomical differences in motor systems.

Traditional anatomical/behavioral classifications suggest that rats and opossums have simple motor systems and are impoverished with respect to their ability to make prehensile movements. Nevertheless, the motor system in rats and opossums represent extremes in relative size and complexity suggesting that a behavioral analysis of the movement competencies of these species will provide insights into the significance of such anatomical differences. This paper examines the movements that the two species use in catching crickets and in reaching for food items. Both species could use a single limb to reach out and grasp prey during prey catching and both could use a single limb to take food from a shelf. Both species could transport the food to the mouth by using a single paw. The food handling behavior of the rats was more complex than that of the opossums, however. They used a variety of prey catching movements and extensively manipulated the prey to remove the legs and wings before eating only the head and body. Additionally the rats made rotatory limb movements of aiming, pronation, and supination, when reaching. For both cricket catching and reaching, they used their digits more than did the opossums. The suggestion also emerged from the results that the movements of the opossums were more fixed and species-typical whereas those of the rats were more plastic and individualistic. Thus, the skilled movements of both species are more complex than is generally recognized and the greater complexity of the rat movements parallels their more complex motor system. These results are discussed in relation to anatomical differences in the motor system and, specifically, to differences in the terminal fields of the pyramidal tract. It is concluded that the motor abilities of nonprimate mammals have been vastly underrated.

Animals↗

PubMed1996

A kinematic analysis of evasive dodging movements used during food protection in the rat (Rattus norvegicus): evidence for sex differences in movement.

Food-deprived rats (Rattus norvegicus) will protect their food by dodging away from a conspecific. A detailed kinematic analysis of these movements in adult rats shows that each sex uses sex-typical movements. Females move their snout through a greater spatial curvature, and their snout achieves a greater velocity, relative to the pelvis, than males. Males make more hindpaw steps than females and achieve a more simultaneous movement of the fore- and hindquarters. This suggests that females pivot around a point more posterior on the body than males. The finding that functionally similar patterns of movement have a sex-specific organization provides a new dimension for the study of sex differences. These differences are discussed in relation to sex differences in sex-typical behaviors, associated body structure, and neural control.

Animals↗

PubMed1995

What do rats find rewarding in play fighting?--an analysis using drug-induced non-playful partners.

Play fighting by juvenile rats involves playful attacks directed at the partner's nape, where successful contact leads to gentle rubbing of the snout into the nape area. In addition, the recipient of such contact may defend the nape by adopting tactics of playful defense. The two most common defensive tactics in the juvenile period are evasion, where the recipient swerves or leaps away and facing defense involving rotation to supine, where the attacker is faced and its further attempts to contact the nape are blocked. An unresolved issue is whether the nape contact itself or defense by the recipient alone or in combination with nape contact, are involved in rewarding play fighting. In this study, drug-induced non-playful partners were used to test the 'motivation' for play fighting when only playful nape contact was possible. In drug-trials compared to baseline and saline trials, both neonatally androgenized females (high players) and control, oil-treated, females (low players), decreased the frequency of launching nape attacks. These results suggest that nape contact alone, in the absence of defense by the recipient, is not sufficient reinforcement for such playful activity, irrespective of the initial playfulness of the subjects. However, while nape attacks decrease, other forms of social contact, such as anogenital investigation and climbing over the partner (i.e., crawl overs), increase in frequency. These results suggest that non-playful partners are not neutral targets for normal rats. Rather, the 'non-normal' behavior of the drugged target may affect the subjects' behavior in such a way as to reduce their playfulness for reasons other than reduced reinforcement for play.

Aggression↗

PubMed1994

Making two movements at once: impairments of movement, posture, and their integration underlie the adult skilled reaching deficit of neonatally dopamine-depleted rats.

Adult rats depleted bilaterally of dopamine in infancy display a profound impairment in skilled forelimb use in reaching for food. This impairment was investigated using end-point measures of reaching success, movement analysis, and kinematic measures. The rats made few successful reaches in either an easy or a difficult reaching test. Their reaches were characterized by many attempts in which trajectories of the limb were irregular and the movements were slow. Their lack of success was related in part to an impairment in making component movements of the reach, including aiming, pronating, grasping, and supinating the paw and in releasing the food pellet. It was also related to an inability to adjust posture as the limb was voluntarily moved toward the food. The results are consistent with the hypotheses that the basal ganglia, including its dopamine innervation, is important for enabling voluntary movements and postural adjustments and perhaps also the simultaneous performance of two movements at the same time.

Aging↗

PubMed1994

Differential effects of amphetamine on the attack and defense components of play fighting in rats.

Treatment with d-amphetamine has been shown to cause a decrease in play fighting by juvenile rats. Previous studies, however, did not determine if all behavioral components of play were equally diminished. In this study, the effects of amphetamine on both the attack and defense patterns of play fighting were analyzed. Experiment 1 shows that a 0.5 mg/kg dose, injected subcutaneously in the nape, decreases both attack and defense. In contrast, Experiment 2 shows that the same dose, injected subcutaneously in the hip, decreases the level of attack to a similar level, but does not significantly affect defense. This suggests that while the 0.5 mg/kg dose of amphetamine is primarily affecting the attack components of play, via its action on the central nervous systems, the reduced likelihood of defense for those rats injected in the nape probably results from a local anesthetic effect, which numbs the area of the body defended during play fighting. Further doses (0.15 & 1.0 mg/kg), injected in the hip, were also tested. The highest dose decreased both components of play. The lowest dose had no effect on either attack or defense. It is suggested that the attack and defensive components of play fighting may be mediated by different neural systems.

Aggression↗

PubMed1994

Development of righting when falling from a bipedal standing posture: evidence for the dissociation of dynamic and static righting reflexes in rats.

Righting to prone when placed supine on the ground by rats is present at birth, albeit in incomplete form. In contrast, righting in the air when falling from the supine position does not begin to emerge until the end of the first week and is not complete until the end of the third week postnatally. On the ground, the animals have sensory information from proprioceptive-tactile sources, as well as vestibular; in the air, they have only vestibular. Thus, it is possible that the difference between contact righting and air righting is a reflection of the relative difference in the maturation of tactile vs. vestibular mechanisms. In this study, pups were tested by pushing them backwards from a bipedal standing position. Such a context provided proprioceptive-tactile information during the fall. The results showed that the developmental onset and maturation of righting from the bipedal position resembled that of air righting rather than contact righting. This suggests that the difference between air righting and contact righting is not due to differences in sensory inputs, but to differential maturation of neural mechanisms for acceleratory (i.e., falling) vs. stationary (i.e., lying on the ground) forms of righting. That is, the appropriate neural systems are organized for the type of righting, not for the sensory systems used. Even so, some evidence is provided suggesting a developmental dissociation between righting from falling with vestibular information only, and with proprioceptive-tactile information in addition. Therefore, righting systems appear to need two dimensions of classification--one based on sensory systems involved, and the other in terms of the context of righting (i.e., falling vs. stationary).

Aging↗

PubMed1994

Feminine dimension in the play fighting of rats (Rattus norvegicus) and its defeminization neonatally by androgens.

In rats (Rattus norvegicus), juvenile males engage in more play fighting (a male-typical behavior) than do juvenile females, and this difference is based on perinatal influences of androgens. We show that there are qualitative and quantitative differences between the sexes in the type of defensive responses and their manner of execution. In defensive responses rats try to avoid having their napes contacted by the partner's snout. The sex differences arise from females' greater response distance; that is, females responded to an approach when the partner's snout was further from the nape. This permits females to use different defensive responses and to use them more successfully. This greater response distance is defeminized by the neonatal administration of testosterone propionate. Our findings suggest that play fighting in rats has both male- and female-typical features and that these are, at least in part, influenced perinatally by androgens.

Aggression↗

PubMed1993

Haloperidol exaggerates proprioceptive-tactile support reflexes and diminishes vestibular dominance over them.

Rats made immobile and cataleptic by haloperidol, a dopamine receptor blocker, maintain their static stable equilibrium by employing a variety of allied postural support reflexes. Under some test conditions, competition between such reflexes occurs, and in haloperidol-treated rats, unlike undrugged controls, proprioceptive-tactile stimuli appear to be dominant over vestibular stimuli. We investigated this relationship in rats by testing their air-righting with and without simultaneous contact of the tail on a wooden platform. The rats were lightly held in a supine position by the shoulders and pelvis, with or without tail contact on a small wooden platform 47 cm above the ground. Undrugged rats showed the normal pattern of righting which involves axial rotation with cephalocaudal recruitment whether the tail is contacting the platform or not. Upon release, the haloperidol-treated rats (2.5 mg/kg) gripped the platform with their tail, which interfered with the air-righting reflex. This demonstrates that in haloperidol-treated rats, the dominance of tactile-proprioceptive postural support reflexes over those triggered vestibularly.

Animals↗

PubMed1993

The role of the striatum in organizing sequences of play fighting in neonatally dopamine-depleted rats.

Juvenile rats sustaining dopamine depletions by intraventricular injections of 6-hydroxydopamine (6-OHDA) as neonates were used to study the role of the striatum in controlling play fighting. As juveniles, the rats exhibited all the behavior elements typical of play fighting. However, they were more likely to use defensive tactics that shortened the playful contact between partners; and when contacting the partner, they were more likely to switch to other behaviors, such as allogrooming and sexual mounting, rather than continue with the play sequence. It is suggested here that the striatum is important for maintaining sequential organization of play fighting.

Aggression↗

PubMed1993

Proximal and distal impairments in rat forelimb use in reaching follow unilateral pyramidal tract lesions.

Although it was once thought that the corticospinal (pyramidal) tract was the main substrate of voluntary movement, the extent to which it is involved in the control of proximal vs. distal musculature, independent finger movements, and movements characteristic of different species of animals now is unclear. The objective of this study was to examine the effects of pyramidal tract lesions on skilled forelimb use in rats. In addition, cell morphology in motor cortex following lesions was examined. Naive and trained rats received unilateral pyramidal sections just rostral to the pyramidal decussation. Performance was assessed and filmed on two reaching tasks. Measures of reaching consisted of success in obtaining food, kinematic analysis of limb trajectory and velocity, and qualitative evaluation of 10 movement components comprising a reach. Pyramidal tract lesions only impaired reaching for single food pellets. Almost all movements comprising a reach, except digit opening, were impaired, including lifting, aiming, pronating and supinating the limb, and releasing food. Although success in limb use was unchanged over the 180 day observation period, there were significant improvements in the qualitative features of limb use. Histologically, the morphology of pyramidal cells in the forelimb area ipsilateral to the lesion seemed normal. Rats with additional damage to adjacent structures, such as the medial lemniscus and olivary complex, were much more severely impaired on the reaching tasks, and displayed similar impairments as judged by qualitative and kinematic measures. The results demonstrate that a number of movements involved in independent limb use are chronically impaired by pyramidal tract lesions in the rat. Nevertheless, significant use of the limb is possible, due perhaps to both the contribution of extrapyramidal motor systems and the influence of the remaining pyramidal system through its extrapyramidal connections. The results not only show that the rat pyramidal tract supports functions very similar to those of primates and thus might provide a good model for some aspects of pyramidal tract dysfunctions, but also they argue that the pyramidal tract is involved in both proximal and distal limb movements.

Animals↗

PubMed1992

A behavioral study of the contributions of cells and fibers of passage in the red nucleus of the rat to postural righting, skilled movements, and learning.

Although the red nucleus consists of cells of origin for the rubro-spinal and rubro-olivary tracts, fibers of passage, including those of the superior cerebellar peduncle, which project from the cerebellum to the ventrolateral thalamus, pass through it. This study examined the relative effect of cell vs. fiber damage in the red nucleus on a number of behaviors thought to involve the red nucleus, including a skilled movement of reaching for food with a forelimb, postural righting on a surface and in the air, and learning a place response in a swimming pool test. Rats received unilateral or bilateral red nucleus lesions, using either the relatively cell-specific neurotoxins, ibotenic and quinolinic acid, or non-specific electrolytic anodal lesions. Both neurotoxic lesions effectively eliminated all red nucleus cell bodies, and in some animals they produced small cavities in the red nucleus and/or loss of cells in adjacent structures. Electrolytic lesions destroyed both cells and fibers, leaving a large cavity. The severity of the behavioral deficits were not related to the loss of red nucleus cells and there was a close relation between fiber damage and behavioral impairments on all of the tasks. The results suggest that for a number of behaviors, which have been thought to involve the red nucleus, impairments are more closely associated with fiber damage or damage to structures outside the red nucleus than they are to damage to cells of the red nucleus.

Animals↗

PubMed1992

Medial frontal cortex lesions impair the aiming component of rat reaching.

This study examined the contribution of medial frontal cortex (the medial portion of supplementary motor cortex, or Fr1) to the performance of rats on trained, or 'skilled', reaching tasks. Unilateral medial frontal cortex lesions moderately impaired reaching success on a task that demanded accuracy but they did not impair performance on a less demanding reaching task nor did they affect limb preference. Kinematic analyses indicated that the aiming component, in which the forearm of the limb is aligned along the midline of the body by adduction of the elbow, was chronically impaired. Rather than adducting the elbow to aim, the rats used a number of limb and whole body postural adjustments to compensate for incomplete or absent aiming. That medial frontal cortex is involved in the execution of at least one component of skilled reaching implies that a larger area of frontal cortex is involved in skilled limb movement than has been suggested by previous studies. The results also suggest that the different regions of frontal cortex may each have a relatively selective involvement in the execution of only a subset of the movements comprising a reach.

Animals↗

PubMed1992

Intrinsic and extrinsic influences on play fighting in rats: effects of dominance, partner's playfulness, temperament and neonatal exposure to testosterone propionate.

Play fighting is a frequent activity of juvenile rats and appears to show marked variability amongst individuals in that some rats play a great deal and others very little. This study attempted to identify some of the factors involved in producing this individual variability. The major influence over an individual's frequency of play as a juvenile was found to be the frequency of play by the partner. That is, play appears to be contagious, in that a high playing animal stimulates its partner to play frequently as well. In male juveniles, but seemingly not in female juveniles, the subsequent adult status of one partner as dominant influences the subordinate-to-be to initiate more playful contacts. In addition to these extrinsic influences, however, there appear to be intrinsic factors that influence whether an individual is a high or low playing animal. One intrinsic factor appears to be 'boldness', so that bolder animals tend to initiate more playful contacts. Higher players tend to be more susceptible to the stereotypy-inducing effects of the dopamine agonist, apomorphine, and tend to be more dependent upon the playful activity of the partner to maintain their own high levels of play. Both of these characteristics are consistent with other studies comparing bold and timid rats. Boldness, however, only seems to influence how much play a rat will exhibit, not how much play it is capable of exhibiting. Neonatal testosterone augmentation increases juvenile play fighting but not apomorphine susceptibility, suggesting that a high player need not be a bold animal. The total frequency of play an individual is capable of initiating appears to depend upon perinatal exposure to androgens. Boldness and the playfulness of the partner appear to modulate the expression of this hormonally set value.

Agonistic Behavior↗

PubMed1992

Spontaneous forelimb grasping in free feeding by rats: motor cortex aids limb and digit positioning.

Forelimb use in grasping food during free feeding was studied in control and motor cortex damaged rats using videoanalysis and Eshkol-Wachmann Movement Notation (EWMN). Rats detected food using olfaction, grasped it by mouth, and then sat and reached for it with their paws. Once held in the paws, the food was eaten. A reach consists of: (1) lifting the forelimbs from the ground, (2) positioning them elbows-in, so that the paws were adjacent to the mouth, and (3) clasping the food in the digits. These movements were executed mainly with the upper arm. Limb movements were usually bilaterally symmetrical but when asymmetrical movements occurred, the forelimb least involved in weight support initiated the movement. As the limb was positioned for grasping, the aperture of the digits was adjusted to anticipate the size of the food and the food was grasped and manipulated with the tips of the digits. Following unilateral motor cortex lesions to the forelimb area: (1) the ipsilateral limb (good limb) initiated lifting, positioning, and grasping movements, (2) appropriate adjustment of the digits of the contralateral limb (bad limb) and grasping were impaired, and (3) when contact with food was lost, the bad limb adopted an extended, closed-fist spastic posture and could not be repositioned independently. The gross impairments cleared within 2 weeks, and after a few months impairments were infrequently observed. These findings show that: (1) spontaneous food grasping uses both proximal movements of the limb and distal movements of the digits, (2) digit aperture anticipates food size in reaching, and (3) motor cortex damage impairs both proximal and distal movements more profoundly when the limb is used independently than when it is used in conjunction with the good limb. The results are discussed in relation to kinematic studies on primates and humans.

Animals↗

PubMed1992

Skilled reaching in rats and humans: evidence for parallel development or homology.

Forelimb reaching by the rat is used as a paradigm for the experimental study of neural control, plasticity, and recovery of function after injury, in the expectation that results are generalizable to humans. The present study was done to compare rat to human reaching movements. The movements of both species were videorecorded and subjected to frame-by-frame analysis using Cartesian (spatial and velocity) and Eshkol-Wachman Movement Notation (EWMN) systems. The component movements of reaching, their sequence and velocity profiles, and their topography were similar in the two species. Both species also displayed more supination and lengthened grasping times when reaching for small as opposed to large objects. Both rats and humans moved the limb medially using the upper arm to aim it when they were required to reach through an aperture but in a free reaching test only rats continued to aim the limb. Human movements were characterized by greater blending of movement components, more variability, and independent digit use. Arguments are presented that the similarities and differences in rat and human reaching are not trivially accounted for by limb and task similarities. The many similarities in the movements of the two species provide evidence for at least parallel development or perhaps even homology.

Adult↗

PubMed1992

The development of righting reflexes in the pouch young of the marsupial Dasyurus hallucatus.

The development of righting was studied in the young of Dasyurus hallucatus, a small marsupial from northern Australia. Young were tested from birth to weaning. Righting began at 40 days, when tactile input on the snout triggered rotation to prone. Over the next 15-20 days, asymmetrical tactile input on the body triggered righting movements by the hindlegs (and later by the forelegs). Vestibular righting reflexes developed after these tactile righting reflexes. Furthermore, asymmetrical vestibular righting (i.e., when the young are held laterally in the air) developed before symmetrical vestibular righting (i.e., when held downward by the pelvis or placed supine in water). Vestibular righting triggered by falling supine in the air did not develop until about 80 days. This study further demonstrates that righting behavior does not consist of a single, integrated motor pattern, but a suite of motor patterns having independent control mechanisms and patterns of development.

Aging↗