The effect of dietary supplementation of Vitamin B12 on behavioural and neural activity in healthy rats

Hayashi, Y. (2026) The effect of dietary supplementation of Vitamin B12 on behavioural and neural activity in healthy rats. PhD thesis, University of Reading. doi: 10.48683/1926.00130247

Abstract/Summary

Background: Vitamin B12 is essential for brain function, including neurotransmitter synthesis and myelination. Although vitamin B12 deficiency is associated with cognitive and sensory impairments, its effects on sensory perception and sensory signal processing in healthy individuals remain unclear. Investigating such effects requires behavioural paradigms that allow reliable repeated assessment of sensory function; however, suitable protocols for repeated texture-based whisker discrimination in rodents have not been well established for repeated assessment. Objectives: This study aimed (i) to establish an appropriate methodological framework for repeated assessment of whisker mediated texture discrimination using the textured novel object recognition test (tNORT), and (ii) to apply this framework to examine the effects of vitamin B12 supplementation on whisker sensitivity and sensory-evoked neural responses in healthy rats. Methods: A methodological study was first conducted to determine suitable object properties and inter test intervals for repeated tNORT using eight male Lister Hooded rats. For the main study, twenty-eight male Lister Hooded rats were randomly assigned to a control group (n = 14) or a vitamin B12 group (n = 14). The B12 group received vitamin B12 enriched drinking water, with the concentration gradually increased to a final level of 4000 μg/kg diet. Behavioural assessments using the validated tNORT protocol were performed before and after a three-week supplementation period. Following supplementation, in vivo electrophysiological recordings of sensory evoked field potentials (LFPs) were recorded in the ventral posteromedial nucleus (VPM) of the thalamus and the barrel cortex under varying stimulus intensities, and stimulation frequencies. In addition, ex vivo recordings were performed to assess input-output relationships, short-term plasticity, and sensory adaptation within cortical networks. Results: The methodological study identified task parameters that enabled reliable repeated assessment of whisker-mediated texture discrimination without positional or exploration bias. For the main study, vitamin B12 supplementation significantly increased serum cobalamin levels; however, behavioural performance in the tNORT did not show significant group differences in healthy rats. In vivo electrophysiological recordings revealed no marked effects of vitamin B12 supplementation on input-output relationships or short-term sensory adaptation in either the thalamus or barrel cortex. Ex vivo recordings similarly showed no significant supplementation related changes in baseline synaptic transmission, presynaptic release probability, or overall adaptation strength. A subtle, frequency-specific difference was detected at 10 Hz stimulation, where evoked responses in the supplemented group exhibited greater attenuation across successive pulses; however, this effect did not generalise across frequencies or stimulation paradigms. Conclusions: Together, these findings indicate that vitamin B12 supplementation does not robustly alter whisker-dependent behaviour or sensory processing in the barrel cortex of healthy, non-deficient rats. Any potential effects appear subtle, frequency dependent, and restricted to specific circuit states. This thesis highlights the importance of methodological validation in behavioural neuroscience and suggests that the neurophysiological consequences of vitamin B12 supplementation in healthy systems are context-dependent rather than uniform.

Item Type	Thesis (PhD)
URI	https://centaur.reading.ac.uk/id/eprint/130247
Identification Number/DOI	10.48683/1926.00130247
Divisions	Life Sciences > School of Biological Sciences > Biomedical Sciences
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