Forelimb Preference Research Articles

Preferential limb use in relation to epicoracoid overlap in the shoulder girdle of toads

We studied left-right asymmetry in forelimb and hindlimb use in green toads (Bufo viridis) and fire-bellied toads (Bombina bombina) and investigated its possible relationship to the asymmetric structure of the shoulder girdle (epicoracoid overlap) in the latter species. To estimate forelimb use preference we used a modified “snout-wiping test” (Bisazza et al., 1997) and to estimate hindlimb use preference we used the “righting response test” (Robins et al., 1998). The position of epicoracoids in living animals was determined as proposed earlier (Borkhvardt & Malashichev, 1997). We also examined behavioural laterality in B. viridis to check whether B. viridis is a left-handed species, as it was not clear from the previous study. Our results showed that B. viridis predominantly used the left forelimb and left hindlimb in experimental situations at both the population and individual levels. The same tests were applied to fire-bellied toads, B. bombina, with right or left epicoracoids in the top (dorsal) position. We found that (1) B. bombina is mostly a symmetric species, sometimes using both hands or feet simultaneously; (2) it is ambidextrous in hand and foot use with non-significant left side preference at the population level; (3) there is a positive and significant concordance between the position of epicoracoids and the forelimb preference in B. bombina. Animals with the right epicoracoid in the dorsal position (R. top = L. superficial) prefer to use the right forelimb in the ''snout-wiping test'' and L. top animals predominantly use their left forelimb.

Are Archeobatrachian Anurans Ambidextrous? Assessing Handedness in Bombina orientalis

Lateralized behaviors (i.e., handedness), in the absence of conspicuous morphological asymmetry, have been noted in a variety of nonmammalian vertebrates, including certain fishes, frogs, and birds (reviewed in Bisazza et al., 1998; Vallortigara et al., 1999). Lateralized behaviors, such as turning preference during the initiation of a startle response, may facilitate quick reaction. When these behaviors first evolved, though, is unknown. Yamashita et al. (2000) suggested that lateralized behaviors might be common among anurans. However, their presence in any archeobatrachian anurans has not been assessed. One of the most basal archeobatrachian families is the Bombinatoridae (Cannatella, 1999). Here, we test tadpoles and postmetamorphic juveniles of the bombinatorid taxon Bombina orientalis for turning bias and forelimb use, respectively, to determine whether lateralized behaviors occur in this family. There is a fairly extensive literature on handedness in postmetamorphic anurans, at least for neobatrachian taxa. Dill (1977), for example, examined jumping direction in the Pacific tree frog, Hyla regilla, and found a significant left side preference in certain individuals. Bisazza et al. (1997) and Robins et al. (1998) examined handedness in toads of the genus Bufo using a series of protocols. Their first test required each toad to remove a plastic balloon from its head. In this test, Bufo bufo showed significantly greater use of the right forelimb than the left at the population level. Their second test consisted of placing a thin wet strip of paper on a toad's snout and noting which limb it used to clean the paper off. Again, B. bufo showed significant use of the right forelimb. The third test was an underwater righting test in which each toad was submerged in water in a supine position and allowed to right itself. In this test, Bufo marinus exhibited a right forelimb preference, causing it to roll to the left side. In addition, Robins et al. (1998) found lateralized hind limb use by B. marinus, Bufo viridis, and B. bufo when allowed to right themselves on a dry surface. Specifically B. marinus and B. bufo showed a significant preferential use of the right hind limb, and B. viridis showed significant use of the left hind limb. More recently, behavioral laterality was reported in the preferred turning direction of anuran larvae (Wassersug et al., 1999; Yamashita et al., 2000). When tadpoles are startled, or when they descend after surfacing to take a gulp of air, they can turn preferentially

Graded unilateral cervical spinal cord injury in the rat: evaluation of forelimb recovery and histological effects

The purpose of this study was to develop a model of unilateral cervical (C4–C5) spinal cord contusion injury in the rat and to characterize the functional and histological consequences following three injury levels using a new weight-drop spinal cord injury device. We evaluated forepaw/forelimb and hindlimb functions by: (1) a horizontal ladder beam measuring paw misplacements and slips; and (2) the forelimb preference test which measures the forelimb used for pushing off to rear, for support, and to land on after rearing. Rats with a mild spinal cord injury displayed primarily a forepaw deficit (forepaw misplacements) for 8 weeks after injury. Paw preference also improved after injury, but failed to reach control levels even after 12 weeks. These rats had damage primarily to the rubrospinal, spinocervicothalamic, and the uncrossed lateral corticospinal tracts in the dorsolateral funiculus a well as some loss of the lateral spinothalamic tracts in the lateral funiculus. Rats with a moderate injury had a prominent forepaw deficit still evident at 12 weeks after injury as well as a mild but not significant hindlimb deficit. Paw preference improved slightly 12 weeks. There was a larger lesion in the dorsolateral and lateral funiculi than in mildly injured rats which extended into the ventrolateral funiculi. There was a significant loss of gray matter compared to rats with a mild injury. Rats with a severe injury displayed significant forelimb and hindlimb deficits throughout the 12 week testing period compared to rats with a mild or moderate injury, and also had a more severe paw preference bias (90%). The lesion encompassed the entire dorsolateral, lateral and ventrolateral funiculi with some disruption of the ventral funiculus. There was more significant gray matter necrosis compared to rats with either a mild or moderate injury. Thus, the spinal cord injury device we used may be useful for studying graded cervical spinal cord injury in rats and potential treatments or interventions, because both the behavioral and histological effects are reproducible and consistent.

Reversal of paw preference after ablation of the preferred forelimb primary motor cortex representation of the rat depends on the size of the forelimb representation

Animals were tested for forelimb preference in a grasp or in a force task before microstimulation mapping of the primary motor cortex contralateral to the preferred forelimb. The size and location of the preferred forelimb primary motor cortex representation was determined and ablated. Seven days later, forelimb preference was again evaluated. Reversal of the initial preference after cortical ablation depended on the size of the preferred forelimb primary motor cortex representation. The mean size of the forelimb representation of the animals that immediately reversed forelimb preference after the cortical ablation was significantly smaller than the mean size of the representation of the animals that did not reverse forelimb preference in three consecutive tests seven days after the lesion. In another experiment, the size, location, and threshold currents of the forelimb representations were evaluated bilaterally before the forelimb preference test. The mean size of the preferred representations did not differ from the mean size of the non-preferred representations. However, when the primary motor cortex representation of the preferred forelimb was ablated, reversal of the initial preference depended, as in the previous experiment, on the size of the forelimb representation. In conclusion, reversal of forelimb preference after ablation of the preferred forelimb primary motor cortex representation depends on the size of the forelimb representation. Moreover, forelimb preference in a behavioral task is not associated with a larger forelimb representation in the contralateral primary motor cortex.

Innate versus learned factors determining limb preference in the rat

The basic factors determining forelimb preference in the performance of different skilled movements were studied in white rats. To analyse whether limb preference actually reflects an initial individual motor asymmetry or is a result of instrumental learning (the first successful movement becoming fixed), the method of retrograde amnesia from electroconvulsive shock was used. It was shown that limb preference is initial and not a results of learning and, evidently, is due to intrinsic factors. The preferred limb can be identified in as few as 3 successful movements. There is a gradation among animals according to the degree of initial limb preference and its resistance to rearrangement of the motor task. The differences of limb preference in different movements were also analysed. Dependence of the preference on the character of the required movement was shown. Four basic types of movement were revealed by factor analysis. As different muscular groups (distal and proximal), controlled by different descending motor systems can be involved in the performance of different movements, it is assumed that the initial motor asymmetry in each movement is a result of asymmetry of central motor structures involved in the realization of the movement. In the same animal asymmetry of different motor structures might be different. This could explain different limb preference in different movements.

A fast feed-back pathway transmitting sensory information to rubro-spinal cells in the cat

The purpose of this study was to develop a model of unilateral cervical (C4–C5) spinal cord contusion injury in the rat and to characterize the functional and histological consequences following three injury levels using a new weight-drop spinal cord injury device. We evaluated forepaw/forelimb and hindlimb functions by: (1) a horizontal ladder beam measuring paw misplacements and slips; and (2) the forelimb preference test which measures the forelimb used for pushing off to rear, for support, and to land on after rearing. Rats with a mild spinal cord injury displayed primarily a forepaw deficit (forepaw misplacements) for 8 weeks after injury. Paw preference also improved after injury, but failed to reach control levels even after 12 weeks. These rats had damage primarily to the rubrospinal, spinocervicothalamic, and the uncrossed lateral corticospinal tracts in the dorsolateral funiculus a well as some loss of the lateral spinothalamic tracts in the lateral funiculus. Rats with a moderate injury had a prominent forepaw deficit still evident at 12 weeks after injury as well as a mild but not significant hindlimb deficit. Paw preference improved slightly 12 weeks. There was a larger lesion in the dorsolateral and lateral funiculi than in mildly injured rats which extended into the ventrolateral funiculi. There was a significant loss of gray matter compared to rats with a mild injury. Rats with a severe injury displayed significant forelimb and hindlimb deficits throughout the 12 week testing period compared to rats with a mild or moderate injury, and also had a more severe paw preference bias (90%). The lesion encompassed the entire dorsolateral, lateral and ventrolateral funiculi with some disruption of the ventral funiculus. There was more significant gray matter necrosis compared to rats with either a mild or moderate injury. Thus, the spinal cord injury device we used may be useful for studying graded cervical spinal cord injury in rats and potential treatments or interventions, because both the behavioral and histological effects are reproducible and consistent.