Biomedical subjects

S M Pellis

Publications and source records attributed to S M Pellis.

At least 19 recordsLinked to original sources

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↗

PubMed1992

The role of the cortex in play fighting by rats: developmental and evolutionary implications.

Play is a distinctive behavior of young mammals, especially mammals with a well-developed forebrain. For this reason it is thought that there may be a relation between forebrain evolution and highly elaborated play behavior. This study investigated the contribution of the cortex to play behavior by comparing play in control and neonatally decorticated rats (Rattus norvegicus). Play fighting in rats involves the combination of attack by one rat and defense by the recipient, with pinning arising when specific patterns of defense are used. Whether paired with another decorticate or with an intact pairmate, decorticates attacked pairmates as frequently as did intacts, and they were just as likely to defend against playful attacks as were intacts. Where decorticates differed from intacts was on a measure of pinning, in which one rat stands over a supine partner, decorticate rats displayed a reduction of 50% relative to control rats during the juvenile stage in which play is most pronounced (days 25 to 40). Juvenile decorticate rats adopted types of defensive responses which were less likely to result in the pinning configuration. Thus, a reduced pinning frequency reflects an altered pattern of defense, not a reduced level of play fighting. Rather, the decorticate patterns of defense were typical of those defensive responses displayed by adult rats. That is, decorticate juveniles exhibit a precociously mature pattern of playful defense. As intact controls mature, they come to resemble the decorticates in their defensive responses, and hence the difference in pinning frequency between decorticate and intact pairs diminishes. This suggests that the cortex may inhibit the escalation of defense in juveniles and thus promote prolonged ventral-ventral contact during play fighting. The results further suggest that the cortex is involved in the development of adult behavioral skills by facilitating juvenile play.

Aggression↗

PubMed1991

Visual modulation of vestibularly-triggered air-righting in rats involves the superior colliculus.

Vision plays two roles in air-righting, it can trigger air-righting in the absence of the labyrinths, and it can modulate the onset and speed of air-righting depending upon the height of the fall. While the visual cortex is known to be necessary for visual triggering, the neural systems necessary for visual modulation are unclear. In this study, the role of the visual cortex and the superior colliculus in visual modulation by rats was analysed. Rats can visually modulate vestibularly-triggered righting, but not trigger righting visually in the absence of the labyrinths. Adult rats with complete neonatal decortication, and adult rats with more specific ablation of the visual cortex were able to visually modulate air-righting. Ablation of the superior colliculi as well as the visual cortex, or ablation of the superior colliculi alone, resulted in loss of the ability to visually modulate air-righting. It is concluded that the superior colliculus is necessary for visual modulation in rats. It is hypothesized that in cats also, the superior colliculus, not the visual cortex, is necessary for visual modulation.

Animals↗

PubMed1991

Labyrinthine and other supraspinal inhibitory controls over head-and-body ventroflexion.

The vestibular head righting reflex can be demonstrated by holding an adult rat vertically downward, so that the snout points downward. In this situation, the animal dorsiflexes its head and neck, bringing the head towards its normal orientation in space. Bilateral labyrinthectomy not only blocks this response, but releases an actively maintained ventroflexion of the head and neck. Bilateral electrolytic lesions of the lateral hypothalamus (LH) exaggerate such ventroflexion in labyrinthectomized rats. By themselves, LH lesions had no such effect. Therefore, it is argued that there are vestibular and supraspinal inhibitory mechanisms which, in the intact adult animal, keep this ventroflexion response in check. In addition, when the rats were held with their heads down, and with gentle paw contact with the ground, they did not ventroflex. However, they ventroflexed immediately upon releasing this paw contact. These observations suggest that there are tactile mechanisms which can also inhibit this exaggerated ventroflexion released by labyrinthectomy.

Animals↗

PubMed1991

Air righting without the cervical righting reflex in adult rats.

The current explanation of air righting in animals is that when falling supine in the air, labyrinthine stimulation triggers head rotation. The head rotation involves neck rotation which, via the cervical righting reflex, triggers rotation of the body. (In cats and monkeys, when the labyrinths are absent, visual stimulation when falling supine can also trigger this righting sequence.) In the present paper, a descriptive analysis of air righting in the rat shows that the shoulders rotate, carrying the unmoving head and neck passively along. Thus, for this species, labyrinthine input appears to trigger shoulder rotation directly, independently of the cervical righting reflex. This suggests that at least two physiological mechanisms exist for labyrinthine control of head rotation during air righting, one via the neck and the other via the shoulder girdle.

Animals↗

PubMed1991

The impairments in reaching and the movements of compensation in rats with motor cortex lesions: an endpoint, videorecording, and movement notation analysis.

Reaching for food by rats, with the limb contralateral to limb area motor cortex damage, was analyzed using end-point scores, videoanalysis, and Eshkol-Wachmann Movement Notation (EWMN). End point results from groups of rats with small, medium, and large lesions showed reaching success and amount of food grasped per reach decreased with increases in lesion size. Videoanalysis and EWMN showed that the impairments were attributable to: (1) an inability to pronate the paw over the food by abduction of the upper arm, and (2) an inability to supinate the paw at the wrist to orient the food to the mouth. There were no obvious impairments in locating food using olfaction, in positioning the body in order to initiate a reach, or in clasping the digits to grasp food. There were only mild impairments in lifting, aiming, and advancing the limb. In rats with medium and large lesions, loss of pronation and supination were compensated for by a variety of whole body movements. These findings are discussed in reference to neural and behavioral mechanisms underlying recovery of function and the contribution of the motor cortex to skilled movements in the rat and other species.

Animals↗

PubMed1990

The structure of skilled forelimb reaching in the rat: a proximally driven movement with a single distal rotatory component.

The movements of rats trained to reach through an aperture for food pellets, located on a shelf, were videorecorded and filmed from lateral and ventral perspectives for analysis using Eshkol-Wachman Movement Notation (EWMN). Reaching was subdivided into phases of locating the food and advancing the limb to grasp the food, bringing the food to the mouth, and returning to the starting position. Further analysis of the movements comprising these acts revealed a number of novel findings. (1) Most of the first phase of the movement is produced proximally, with the limb lifted, aimed, and advanced from the shoulder. (2) After the limb is lifted from the substrate to initiate reaching, it is carried to a parasagittal position so that the long axis of the forearm is aligned along the midline of the body. This aspect of the movement 'aims' the limb toward the target. (3) The digits are opened as the limb is advanced from the aiming position toward the food. As the paw approaches the food, pronation of the palm is accomplished by abduction of the upper arm. (4) As the limb is retracted, the digits are closed to grasp the food. As retraction ends, the paw is supinated by a rotatory movement at the wrist. This is the only distal rotatory movement. (5) The position taken by the second forelimb, as it is adducted to aid in holding the food pellet for eating, resembles the 'aiming' posture. The results are discussed in reference to the kinematics, neural control, and the evolutionary origins of reaching in the rat and other animals. Additionally, the results provide a framework for analysis of changes in movements produced by physiological manipulations.

Animals↗

PubMed1990

Labyrinthine and visual involvement in the dorsal immobility response of adult rats.

The dorsal immobility response (DIR) is typically seen in the infants of many altricial mammalian species. Lifting the animal into the air by the nape of the neck is the primary releasing stimulus. Functionally, this response appears to facilitate carrying of the infants by the adults. When grasped by the nape and lifted into the air, adult rats will also exhibit the DIR. In this paper, the role of the labyrinths in the DIR of adult male rats was examined. Vestibular stimulation produced by vertical circular acceleration increased the duration of the DIR, while labyrinthectomy greatly diminished the DIR. In rats with intact labyrinths, visual occlusion greatly potentiated the DIR, whereas, in labyrinthectomized rats, visual occlusion had little effect. These data indicate that the vestibular system plays a major role in mediating the DIR of adult rats. The retention of the DIR into adulthood and the possible increased role of the labyrinths in the control of the adult DIR, are discussed with respect to the possible role of the DIR as an anti-predator mechanism.

Animals↗

PubMed1990

Differential rates of attack, defense, and counterattack during the developmental decrease in play fighting by male and female rats.

During postweaning development, rats exhibit several well documented trends in their play fighting: (1) It peaks between 30-40 days and then declines with the approach of sexual maturity; (2) males initiate more play fights than females; and (3) the overall complexity of play fights, as expressed by such measures as duration of bouts, also decreases with increasing age. Such trends could arise from changes in attack or defense, or some combination of both. In this article it is shown that (a) the decline in play fighting with the onset of sexual maturity in rats results from a decline in attack, not in defense; (b) the differences in play fighting by male and female rats are due to sex-specific rates of both attack and defense; and (c) the developmental decrease in the complexity of play fighting arises from a decrease in the frequency of counterattacks (i.e., after an animal defends itself, it is less likely to launch an attack). In this way, age and sex differences in play fighting can be traced to differences in its subcomponents.

Aggression↗

PubMed1990

An open-field activity analysis of labyrinthectomized rats.

A detailed behavioral analysis was performed on rats that received bilateral labyrinthectomies. They were placed in a walled activity monitor (39 x 39 cm) that allowed the animal to move freely within the enclosure. Their behavioral activities were automatically recorded. These activities were placed into twelve different categories. The results show a lower rate of habituation for the labyrinthectomized animal as well as an overall increase in activity over all dimensions as compared to the control. This increase in behavior may be exploratory and a necessary feature in the formation of spatial maps.

Animals↗

PubMed1989

Seemingly paradoxical jumping in cataleptic haloperidol-treated rats is triggered by postural instability.

Paradoxically, animals exhibiting haloperidol-induced cataleptic immobility can be induced to leap vigorously, by pushing them forward from behind. It is shown here that such jumping can also be produced by placing them on a board and tilting it tail-end upward until about 50 degrees above horizontal. In both situations, jumps only occurred when the animal's hindlegs began to slip forward, as they lost their postural stability. As alternatives to jumping from the slope, rats turned to face upwards (negative geotaxis), or adopted a spread-eagled posture during head-first downward sliding, with the body and head flattened against the substrate. All 3 responses to the sloping board were present in some undrugged rats. Such rats, and those given low doses of haloperidol (0.5, 1.0 mg/kg), were more likely to turn upwards than to jump or slide. At high doses (7.5, 10.0 mg/kg), they were more likely to slide downward than to turn or jump. Jumping was most likely to occur at an intermediate dose (5 mg/kg), approximately 60 min after injection. We suggest that in the absence of haloperidol, and at low doses, locomotion is dominant over reflexes defending static equilibrium, and hence rats are more likely to turn upwards (which involves stepping). In contrast, at higher doses, locomotion is more fully suppressed, reducing the likelihood of turning. At very high doses of haloperidol and later in the action of the drug, muscle tonus appears to be weakened, reducing the likelihood of jumping. This possibility was supported by the finding that combined injection of the optimal dose of haloperidol and 2 mg/kg diazepam reduced the ability to cling vertically (suggesting weakness of muscle tone). In such rats, jumping from the sloping board was decreased, and active downward sliding was increased. Thus, different factors influence the occurrence of jumping at different doses of haloperidol. However, these are all active defensive responses to postural instability, and hence are similar to the other reflexes used by haloperidol-treated rats to defend against displacement from static stable equilibrium, such as standing immobile, bracing, clinging, and righting. Jumping in response to loss of stability on the sloping board also occasionally occurred in undrugged rats. Unlike jumps by haloperidol-treated rats, those by undrugged animals only occurred when they could be directed to a safe landing place. Thus, if the board faced the edge of the table, so that the jump would carry the animal into space over the edge, undrugged rats either did not jump or jumped off the side of the board onto the table.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1989

Recovery from axial apraxia in the lateral hypothalamic labyrinthectomized rat reveals three elements of contact-righting: cephalocaudal dominance, axial rotation, and distal limb action.

In earlier work, we showed that in rats, proprioceptive-tactile information is sufficient for contact-righting on the ground (from lying on one side to prone). Thus, axial rotation, starting with the shoulders and followed by the pelvis, occurs normally in labyrinthectomized animals with eyes occluded. After damage to the lateral hypothalamus, even with labyrinths intact, contact-righting is at first abolished (1-2 days postoperatively), and when it reappears, involves pushing by the hindlegs. Rostrocaudal contact-righting, involving axial rotation, takes 3-4 days to recover. If labyrinthectomy is combined with lateral hypothalamic damage, the deficit is exaggerated and recovery is greatly slowed down, now requiring 2-3 weeks. The present paper shows that during this prolonged period of recovery several transitional forms of righting are present, each produced by a different combination of limb and body axis movements. At first, axial rotation is absent, and righting is achieved only by pushing with the limbs. This is followed by a transitional form in which, even though axial rotation cannot be triggered directly by contact with the ground, it can be triggered indirectly as an allied reflex when the paw places on the ground. Eventually the body axis actively initiates the rotation to proneness (at first, in the pelvis, later in recovery, in the shoulders), with the limbs being carried. Recovery of axial rotation overlaps with the recovery of cephalic dominance, yielding complex intermediate forms of righting.

Animals↗

PubMed1989

Visual modulation of vestibularly-triggered air-righting in the rat.

Unlike cats, which can initiate righting in the air either with vestibular or visual input alone, the rat is dependent solely upon the labyrinths to trigger this response. We show, however, that the rat can modulate the onset and speed of its rotation according to the height above the ground from which it is dropped. In the absence of vision, rates initiate rotation with a latency of about 50 ms, irrespective of the height from which they are dropped. With vision, rats can modulate their latency to begin rotation, from about 102 ms at 50 cm, to about 39 ms at 7.5 cm. Similarly, as height of release decreases, the speed of rotation (i.e. degrees/ms) increases. Thus, in rats, even though vision cannot trigger air-righting, it does adaptively modulate this behavior as an allied reflex, increasing the likelihood that the animals will land on their feet.

Animals↗