Lateralized motor behaviour in the righting responses of the cane toad (Rhinella marina).

This paper reports a series of tests for fore- and hind-limb preferences used by cane toads, Rhinella marina, to assist returning to the righted position after being overturned. We confirm the strong and significant right-handedness reported in this species, which under certain conditions exceeded 90% right-hand preference at the group level. Toads were tested under a variety of conditions including horizontal and inclined surfaces, with and without the opportunity for the forelimbs to grasp a support, in order to assess the effects of different vestibular and proprioceptive input on the strength and direction of fore- and hind-limb preferences. A range of behavioural strategies indicated learning effects; however, the strength or direction of limb preferences did not increase significantly with experience, even in toads retested multiple times. Comparisons with the mammalian condition for limb preferences are discussed with relevance to practice effects and established limb preferences, and to effects associated with arousal or stress. In contrast to the expectation that handedness in toads represents intentional or voluntary preferences, the presence of lateralized central pattern generators in the toads is postulated to explain the different forms of lateralization revealed by our tests.

Sheep Quickstep while the Floor Rock and Rolls: Visuomotor Lateralization during Simulated Sea Travel.

Unpredictable floor motions during transport disturbs animals' balance, requiring stepping to move the centre of gravity in the direction of body movement. When repeated regularly, this may be stressful, requiring involvement of the right brain hemisphere, hence we investigated the existence of behavioral laterality in sheep during prolonged floor motions. Six sheep were restrained in pairs on a programmable rocking platform, in which they were unable to turn around. They were exposed to three continuous rocking motion treatments (roll, pitch or both) in a regular or irregular pattern for 1 h periods in a changeover design. Right forelimb and left hindlimb diagonal stepping was more frequent in response to the motion treatment of irregular roll and pitch, which previous research has suggested to be the most stressful from heart rate measurements. An overall strategy to maintain balance appeared to be the use of the right hindlimb as a stabilizer, which was repositioned least often of all limbs until towards the end of the hour of experimental treatment. Of each tested pair, sheep restrained on the left side of the rocking floor stepped significantly often than its partner restrained on the right side, and we postulate the existence of visuomotor lateralization as left restrained sheep were unable to view their partner within the field of view of their left eye. We also investigated which side sheep lie down on, which if left lateralized could explain our observed bipedal diagonal control of sheep balance under stress. From the observation of 412 web-based images of sheep, there was an overall left-sided laterality to their lying, as has been observed in cattle. We conclude that stepping activity in sheep in response to a motion stressor is lateralized, providing evidence that floor motion experienced in transport may induce stress responses.

The Alpha Hypothesis: Did Lateralized Cattle-Human Interactions Change the Script for Western Culture?

Domestic cattle possess lateralized cognitive processing of human handlers. This has been recently demonstrated in the preference for large groups of cattle to view a human closely within the predominantly left visual field. By contrast, the same stimulus viewed predominantly within the right visual field promotes a significantly greater frequency of dispersal from a standing position, including flight responses. The respective sets of behaviours correspond with the traditional terms of "near side" for the left side of cattle and horses, and the "off" or "far side" for the right side. These traditional terms of over 300 years usage in the literature communicate functional practicalities for handling livestock and the recognition of lateralized cognitive processing. In this review, the possibility of even earlier recognition and the significance of laterality in cattle-human interaction was argued, from the earliest representations of the letter "A", originally illustrated from nearly 4000 years before the present time as the head of an ox as viewed not from the front or from the right, but from the left (near) side. By extension, this knowledge of lateralization in cattle may represent the earliest written example of applied ethology-the study of the behaviour of animals under human management.

The eyes have it: lateralized coping strategies in cattle herds responding to human approach.

We report a range of lateralized coping strategies adopted by large social groups of cattle in response to mild challenges posed by humans of varying degrees of familiarity. At either 14 or 18 pens at a commercial feedlot, with 90 to 200 cattle in each, we conducted a series of video recorded 'pressure tests'. 'Frontal' pressure tests involved walking from a position perpendicular to the concrete feed bunk of a given pen, towards the geometric centre of the line of feeding cattle. 'Bunk-side' pressure tests involved experimenters walking closely past a pen of feeding cattle in one direction, before returning in the opposite direction shortly afterwards. Experimenters wore white dust masks to alter their facial features in the bunk-side pressure tests. In both frontal and bunk-side pressure tests, distance from the experimenter influenced cattle's choice of binocular viewing, cessation of feeding, standing or stepping backwards to monitor the approach and leaving the feed bunk. The frequency of these coping strategies differed in a lateralized manner. The cattle were more likely to accept the close positioning of a generally familiar, unmasked human on their left, which is traditionally referred to as the "near" side. By contrast, when responding to the approach of an unfamiliar, masked human, cattle conformed to the general vertebrate model and were more likely to remove themselves from the potential threat viewed within the left and not right visual field. We argue that the traditional terms for livestock sidedness as "near" (left) and "off" (right) sides demonstrate a knowledge of behavioural lateralization in domestic livestock that has existed for over 300 years of stock handling.

White Matter Damage Relates to Oxygen Saturation in Children With Sickle Cell Anemia Without Silent Cerebral Infarcts.

BACKGROUND AND PURPOSE: Sickle cell anemia is associated with compromised oxygen-carrying capability of hemoglobin and a high incidence of overt and silent stroke. However, in children with no evidence of cerebral infarction, there are changes in brain morphometry relative to healthy controls, which may be related to chronic anemia and oxygen desaturation. METHODS: A whole-brain tract-based spatial statistics analysis was carried out in 25 children with sickle cell anemia with no evidence of abnormality on T2-weighted magnetic resonance imaging (13 male, age range: 8-18 years) and 14 age- and race-matched controls (7 male, age range: 10-19 years) to determine the extent of white matter injury. The hypotheses that white matter damage is related to daytime peripheral oxygen saturation and steady-state hemoglobin were tested. RESULTS: Fractional anisotropy was found to be significantly lower in patients in the subcortical white matter (corticospinal tract and cerebellum), whereas mean diffusivity and radial diffusivity were higher in patients in widespread areas. There was a significant negative relationship between radial diffusivity and oxygen saturation (P<0.05) in the anterior corpus callosum and a trend-level negative relationship between radial diffusivity and hemoglobin (P<0.1) in the midbody of the corpus callosum. CONCLUSIONS: These data show widespread white matter abnormalities in a sample of asymptomatic children with sickle cell anemia, and provides for the first time direct evidence of a relationship between brain microstructure and markers of disease severity (eg, peripheral oxygen saturation and steady-state hemoglobin). This study suggests that diffusion tensor imaging metrics may serve as a biomarker for future trials of reducing hypoxic exposure.

Lateralised visual processing in domestic cattle herds responding to novel and familiar stimuli.

We investigated whether cattle exhibit preferences to monitor challenging and novel stimuli. Experiments were conducted on dairy and beef cattle herds and revealed significant left eye preferences in the cattle for viewing an experimenter walking to repeatedly split the herd through its centre. Visual lateralisation was demonstrated in the preference to use the left monocular field to monitor the experimenter, alone or equipped with a range of novel stimuli. This finding is consistent with left eye preferences found in various species of mammals, birds, and amphibians responding to predators and novel stimuli. A cohort of the familiarized cattle herds was then subjected to additional herd-splitting tests with the same stimuli and demonstrated a reversal of viewing preferences, preferring to monitor the experimenter and stimuli within the right and not left monocular field. This directional shift in viewing preferences is consistent with experience-dependent learning found in lateralised visual processing in other, non-mammalian, species, and to our knowledge is the first of such studies to suggest that such lateralised learning processes also exist in mammals. Together the data support a number of key hypotheses concerning the evolution and conservation of lateralised brain function in vertebrates, and also provide important considerations for livestock handling.

Complementary and lateralized forms of processing in Bufo marinus for novel and familiar prey.

Amphibian vision is one of the most comprehensively studied of all vertebrate sensory systems. However, the processes of object recognition and memory in anuran amphibians have resisted satisfactory explanation. Our research shows that insight to the issue of visual discrimination and recognition in toads may be gained by investigation of the specialized and complementary functions carried out by the left and right brain hemispheres. We report that specialized processes associated with the left eye (right hemisphere) of the Bufo marinus toad carry out decisions to view and strike at complex prey stimuli recognized as 'novel.' This was demonstrated in the toads' preferences when provided a choice between identical novel insect models presented simultaneously into the left and right lateral, monocular visual fields. In a second experiment, videotaped trials of toad groups competing in an open field for live crickets were analysed for lateralized prey-catching behaviour. Concomitant with a preference for directing agonistic strikes at conspecifics within the left visual hemifield, toads were found to possess a significant preference for directing predatory responses at the familiar prey viewed in the right visual hemifield. The preference for directing prey-catching responses at freely moving crickets in the right visual hemifield supports the earlier findings drawn from automated and familiar model insect prey. We present a hypothesis explaining differences in hemispheric processing in toads responding to 'novel' and 'familiar' prey types, utilizing a range of long-term memories found to be lateralized in other vertebrates.

Lateralized predatory responses in the ornate dragon lizard (Ctenophorus ornatus).

Lateralized responses for visually elicited feeding behaviour have been reported in toads and birds but not in the phylogenetically intermediate class of vertebrates, the reptiles. Here we examined small social groups of ornate dragon lizards Ctenophorus ornatus (family Agamidae) and provide the first report in reptiles of right eye lateralization (left brain hemisphere) for predatory responses to prey. However, right eye lateralization was not evident initially but became stronger with time supporting a shift to right eye lateralization as the prey became increasingly familiar. The study is in agreement with recent findings in toads, adding credence to the hypothesis that lateralization originated in an early ancestor and highlighting the supposition that the strength and direction of lateralization is dependent on experience.

Light experience and the development of behavioural lateralisation in chicks. II. Choice of familiar versus unfamiliar model social partner.

In late-stage embryos of domestic fowl, exposure of the right eye to light entering through the shell induces asymmetry of the thalamofugal visual pathway, together with differences in performance according to whether the right or left eye (RE, LE) is in use (Behav. Brain Res. 38 (1990) 211). Nevertheless, at least some of the main specialisations of the right and left eye systems (RES, LES) are not dependent on such exposure. Higher ability of LES to assess and respond to novelty is present in dark-incubated (Da) chicks. This is probably also true of RES ability to control response, and specifically to inhibit shift to an alternative response (i.e. to a novel stimulus). We imprinted chicks on red table-tennis balls with a horizontal, white strip on their equator. At test, they chose between this and a ball with a vertical, white strip. Da chicks showed clear choice with the LE, but not with the RE. Unexpectedly, light-incubated (Li) chicks failed to show LE/RE differences in choice. Exploratory pecks at a novel feature were greatly reduced in Li. Two effects of light exposure on RES are likely. The first is greater use of RES in the home-cage, affecting what is learned about the companion ball. This may make RES more competent in assessing ball properties, and so explain the enhanced choice by RE, that abolished the RE/LE difference in Li. Secondly, the ability of RES to inhibit shift to an alternative response is enhanced. Light exposure and being female similarly opposed shift to the novel feature, but probably via different mechanisms. The effects of exposure are discussed as an example of the generation of a range of behavioural phenotypes, which are sustained within a single population by varying or frequency-dependent selection.

Limb preference and skeletal asymmetry in the cane toad, Bufo marinus (Anura: Bufonidae).

Two forms of skeletal asymmetry were identified in a population of cane toads, Bufo marinus, an exotic species in Australia. Fluctuating asymmetry characterised the lengths and weights of the long bones of the forelimbs and hindlimbs. Directional asymmetry was observed in the structure of the pectoral girdle of the toads, with the right epicoracoid positioned ventral to the left epicoracoid in 88% of the skeletons examined. Morphological data from a cohort of individuals were correlated with limb preferences determined from 10 consecutive trials in which the toads were inverted and briefly submerged in water while bilaterally clasping the experimenter's fingers. The toad's left forelimb was released first to enable the right forelimb to exert force against the experimenter's fingers and so control righting the body of the toad in 90% of trials. Asymmetries in the long bones of the forelimbs and pectoral girdles of the toads did not correlate significantly with the strength of preference for the right forelimb, although asymmetry of the weight of the tibiafibulae did correlate significantly with percent right forelimb preference. Age, or nutritional status, was a factor in the right forelimb preference: the preference for the use of the right forelimb was strongest in toads possessing longer and heavier long bones of both the forelimbs and hindlimbs. These results provide insight into the interaction between skeletal development and lateralised motor behaviour in an anuran species.