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Versace, E., Morgante, M., Pulina, G., & Vallortigara, G. (2007). Behavioural lateralization in sheep (Ovis aries). Behav. Brain. Res., 184(1), 72–80.
Abstract: This study investigates behavioural lateralization in sheep and lambs of different ages. A flock was tested in a task in which the animals were facing an obstacle and should avoid it on either the right or left side to rejoin flock-mates (adult sheep) or their mothers (lambs). A bias for avoiding the obstacle on the right side was observed, with lambs apparently being more lateralized than sheep. This right bias was tentatively associated with the left-hemifield laterality in familiar faces recognition which has been documented in this species. Differences between adult sheep and lambs were likely to be due to differences in social reinstatement motivation elicited by different stimuli (flock-mates or mothers) at different ages. Preferential use of the forelegs to step on a wood-board and direction of jaw movement during rumination was also tested in adult animals. No population bias nor individual-level lateralization was observed for use of the forelegs. At the same time, however, there was a large number of animals showing individual-level lateralization for the direction of jaw movement during rumination even though there was no population bias. These findings highlight that within the same species individual- and population-level lateralization can be observed in different tasks. Moreover, the results fit the general hypothesis that population-level asymmetries are more likely to occur in tasks that require social coordination among behaviourally asymmetric individuals.
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Marinsek, N. L., Gazzaniga, M. S., & Miller, M. B. (2016). Chapter 17 – Split-Brain, Split-Mind. In S. Laureys, O. Gosseries, & G. Tononi (Eds.), The Neurology of Conciousness (Second Edition) (pp. 271–279). San Diego: Academic Press.
Abstract: The corpus callosum anatomically and functionally connects the two cerebral hemispheres. Despite its important role in interhemispheric communication however, severing the corpus callosum produces few--if any--noticeable cognitive or behavioral abnormalities. Incredibly, split-brain patients do not report any drastic changes in their conscious experience even though nearly all interhemispheric communication ceases after surgery. Extensive research has shown that both hemispheres remain conscious following disconnection and the conscious experience of each hemisphere is private and independent of the other. Additionally, the conscious experiences of the hemispheres appear to be qualitatively different, such that the consciousness of the left hemisphere is more enriched than the right. In this chapter, we offer explanations as to why split-brain patients feel unified despite possessing dual conscious experiences and discuss how the divided consciousness of split-brain patients can inform current theories of consciousness.
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Giljov, A., & Karenina, K. (2019). Differential roles of the right and left brain hemispheres in the social interactions of a free-ranging ungulate. Behav. Process., 168, 103959.
Abstract: Despite the abundant empirical evidence on lateralized social behaviours, a clear understanding of the relative roles of two brain hemispheres in social processing is still lacking. This study investigated visual lateralization in social interactions of free-ranging European bison (Bison bonasus). The bison were more likely to display aggressive responses (such as fight and side hit), when they viewed the conspecific with the right visual field, implicating the left brain hemisphere. In contrast, the responses associated with positive social interactions (female-to-calf bonding, calf-to-female approach, suckling) or aggression inhibition (fight termination) occurred more likely when the left visual field was in use, indicating the right hemisphere advantage. The results do not support either assumptions of right-hemisphere dominance for control of various social functions or hypotheses about simple positive (approach) versus negative (withdrawal) distinction between the hemispheric roles. The discrepancy between the studies suggests that in animals, the relative roles of the hemispheres in social processing may be determined by a fine balance of emotions and motivations associated with the particular social reaction difficult to categorize for a human investigator. Our findings highlight the involvement of both brain hemispheres in the control of social behaviour.
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Esch, L., Wöhr, C., Erhard, M., & Krueger, K. (2019). Horses� (Equus Caballus) Laterality, Stress Hormones, and Task Related Behavior in Innovative Problem-Solving. Animals, 9(5), 265.
Abstract: Domesticated horses are constantly confronted with novel tasks. A recent study on anecdotal data indicates that some are innovative in dealing with such tasks. However, innovative behavior in horses has not previously been investigated under experimental conditions. In this study, we investigated whether 16 horses found an innovative solution when confronted with a novel feeder. Moreover, we investigated whether innovative behavior in horses may be affected by individual aspects such as: age, sex, size, motor and sensory laterality, fecal stress hormone concentrations (GCMs), and task-related behavior. Our study revealed evidence for 25% of the horses being capable of innovative problem solving for operating a novel feeder. Innovative horses of the present study were active, tenacious, and may be considered to have a higher inhibitory control, which was revealed by their task related behavior. Furthermore, they appeared to be emotional, reflected by high baseline GCM concentrations and a left sensory and motor laterality. These findings may contribute to the understanding of horses� cognitive capacities to deal with their environment and calls for enriched environments in sports and leisure horse management.
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Kruska, D. C. T. (2014). Comparative quantitative investigations on brains of wild cavies (Cavia aperea) and guinea pigs (Cavia aperea f. porcellus). A contribution to size changes of CNS structures due to domestication. Mamm Biol, 79(4), 230–239.
Abstract: Intraspecific allometric calculations of the brain to body size relation revealed distinct differences between 127 (67; 60) ancestral wild cavies and 82 (37; 45) guinea pigs, their domesticated relatives. The dependency of both measures from one another remained the same in both animal groups but the brains of guinea pigs were by 14.22% smaller at any net body weight. Consistent with results in other species the domestication of Cavia aperea is also characterized by a decrease of brain size. Fresh tissue sizes of the five brain parts medulla oblongata, cerebellum, mesencephalon, diencephalon and telencephalon were determined for 6 cavies and 6 guinea pigs by the serial section method. Additionally the sizes of 16 endbrain structures and those of the optic tract, the lateral geniculate body and the cochlear nucleus were measured. Different decrease values resulted for all these structures concomitant with domestication as was calculated from the amount of total brain size decrease and average relative structure values in the wild as well as the domesticated brain. The size decrease of the entire telencephalon (-13.7%) was within the range of the mean overall reduction as similarly was the case for the total neocortex (-10.7%) whereas the total allocortex (-20.9%) clearly was more strongly affected. The size decrease of the olfactory bulb (-41.9%) was extreme and clearly higher than found for the secondary olfactory structures (around -11%). The primary nuclei of other sensory systems (vision, audition) were decreased to less extent (lateral geniculate: -18.1%; cochlear nucleus: -12.6%). Mass decreases of pure white matter parts were nearly twice as high in contrast to associated grey matter parts (neocortex white versus grey matter; tractus opticus versus lateral geniculate body). The relatively great decrease values found for the limbic structures hippocampus (-26.9%) and schizocortex (-25.9%) are especially notable since they are in good conformity with domestication effects in other mammalian species. The findings of this study are discussed with regard to results of similar investigations on wild and domesticated gerbils (Meriones unguiculatus), the encephalization of the wild form, the special and species-specific mode and duration of domestication and in connection with certain behavioral changes as resulted from comparative investigations in ethology, socio-biology, endocrinology and general physiology.
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Shen, Y. - Q., Hebert, G., Lin, L. - Y., Luo, Y. - L., Moze, E., Li, K. - S., et al. (2005). Interleukine-1β and interleukine-6 levels in striatum and other brain structures after MPTP treatment: influence of behavioral lateralization. Journal of Neuroimmunology, 158(1–2), 14–25.
Abstract: MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) induces diminution of the dopamine in nigrostriatal pathway and cognitive deficits in mice. MPTP treatment also increases pro-inflammatory cytokine production in substantia nigra and striatum. Since, pro-inflammatory cytokines influence striatal dopamine content and provoke cognitive impairments, the cognitive defects induced by MPTP may be partly due to brain cytokine induction in other structures than nigrostriatal pathway. Furthermore, behavioral lateralization, as assessed by paw preference, influences cytokine production at the periphery and in the central nervous system. Behavioral lateralization may thus influence brain cytokine levels after MPTP. In order to address these issues, mice selected for paw preference were injected with 25 mg/kg MPTP i.p. for five consecutive days after which striatal dopamine and DOPAC contents were measured by HPLC and IL-1β and IL-6 quantified by ELISA in the striatum, cerebral cortex, hippocampus and hypothalamus. The results showed that MPTP treatment induced dramatic loss of DA in striatum, simultaneously, IL-6 levels decreased in the striatum and increased in hippocampus and hypothalamus, while IL-1β levels decreased in the striatum, cerebral cortex and hippocampus. Interestingly, striatal dopamine turnover under basal conditions as well as striatal IL-1β and IL-6 levels under basal conditions and after MPTP depended on behavioral lateralization. Left pawed mice showed a higher decrease in dopamine turnover and lower cytokine levels as compared to right pawed animals. Behavioral lateralization also influenced IL-6 hippocampal levels under basal conditions and IL-1β cortical levels after MPTP. From these results, it can be concluded that MPTP-induced cognitive defects are accompanied by an alteration of pro-inflammatory cytokine levels in brain structures other than those involved in the nigrostriatal pathway. In addition, MPTP-induced dopamine decrease is influenced by behavioral lateralization, possibly through an effect on brain cytokine levels.
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Neveu, P. J. (1993). Brain Lateralization and Immunomodulation. Int J Neurosci, 70(1-2), 135–143.
Abstract: The two sides of the brain may be differently involved in the modulation of immune responses as demonstrated by lesional and behavioral approaches in rodents. Lesions of right or left neocortex induced opposite effects on various immune parameters including mitogen-induced lymphoproliferation, interleukin-2 production, macrophage activation or natural killer cell activity. This animal model, useful to elucidate whereby the brain and the immune system can communicate, appears to be suitable for studying the immune perturbations observed during stroke in humans. Brain asymmetry in modulation of immune reactivity may also be demonstrated in intact animal using a behavioral paradigm. The direction of a lateralized motor behavior ie paw preference in a food reaching task, correlated with an asymmetrical brain organization, was shown to be associated with lymphocyte reactivity, natural killer cell activity and auto-antibody production. The association between paw preference and immune reactivity in mice varies according to the immune parameters tested and is a sex-dependent phenomenon in which genetic background may be involved. The experimental models for investigating asymmetrical brain modulation of the immune system should be useful for studying several physiological, pathological and genetic aspects of neuroimmunomodulation.
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Vlajkoviç, S., Nikoliç, V., Nikoliç, A., Milanoviç, S. žA., & Jankoviç, B. D. (1994). Asymmetrical Modulation of Immune Reactivity in Left- and Right-Biased Rats After Ipsilateral Ablation of the Prefrontal, Parietal and Occipital Brain Neocortex. International Journal of Neuroscience, 78(1-2), 123–134.
Abstract: We report here on the lateralized brain immunomodulation in male Wistar rats, a phenomenon related to the rotational bias of animal and the site of cortical lesion. Rats assigned to left- and right-rotators in a cylindrical Plexiglass rotometer were subjected to the ablation of the ipsilateral prefrontal cortex (PFC), parietal cortex (PC) and occipital cortex (OC) and sensitized with bovine serum albumin (BSA) in complete Freund's adjuvant. Intact and sham-lesioned left-biased animals demonstrated increased Arthus and delayed hypersensitivity skin reactions and antibody production to BSA in comparison with corresponding right-biased animals. PFC ablation decreased humoral and cellular immune responses to BSA in left- but increased in right-biased rats. Lesioning of PC decreased humoral immune reactions in left- but increased in right-rotating animals. OC ablation failed to produce immunological abnormalities, These results suggest that immunopotentiation is associated with the left neocortex, and immunosuppression with the right neocortex. The prefrontal cortex appears to be particularly associated with immune reactions.
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Harland, M. M., Stewart, A. J., Marshall, A. E., & Belknap, E. B. (2006). Diagnosis of deafness in a horse by brainstem auditory evoked potential. Can Vet J, 47(2), 151–154.
Abstract: Deafness was confirmed in a blue-eyed, 3-year-old, overo paint horse by brainstem auditory evoked potential. Congenital inherited deafness associated with lack of facial pigmentation was suspected. Assessment of hearing should be considered, especially in paint horses, at the time of pre-purchase examination. Brainstem auditory evoked potential assessment is well tolerated and accurate.
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Heffner, R. S., & Heffner, H. E. (1986). Localization of tones by horses: use of binaural cues and the role of the superior olivary complex. Behav Neurosci, 100(1), 93–103.
Abstract: The ability of horses to use binaural time and intensity difference cues to localize sound was assessed in free-field localization tests by using pure tones. The animals were required to discriminate the locus of a single tone pip ranging in frequency from 250 Hz to 25 kHz emitted by loudspeakers located 30 degrees to the left and right of the animals' midline (60 degrees total separation). Three animals were tested with a two-choice procedure; 2 additional animals were tested with a conditioned avoidance procedure. All 5 animals were able to localize 250 Hz, 500 Hz, and 1 kHz but were completely unable to localize 2 kHz and above. Because the frequency of ambiguity for the binaural phase cue delta phi for horses in this test was calculated to be 1.5 kHz, these results indicate that horses can use binaural time differences in the form of delta phi but are unable to use binaural intensity differences. This finding was supported by an unconditioned orientation test involving 4 additional horses, which showed that horses correctly orient to a 500-Hz tone pip but not to an 8-kHz tone pip. Analysis of the superior olivary complex, the brain stem nucleus at which binaural interactions first take place, reveals that the lateral superior olive (LSO) is relatively small in the horse and lacks the laminar arrangement of bipolar cells characteristic of the LSO of most mammals that can use binaural delta I.
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