Abstract/Summary

This doctoral thesis presented two studies. The first study focuses on the effect of Vitamin B6 (VitB6) supplementation, and the second study examines the phase relationship of local field potentials (LFPs) between the barrel and motor cortices. The same rodent model was employed in both studies. VitB6 is an essential water-soluble vitamin involved in amino acid metabolism, neurotransmitter synthesis, and neuronal function. While its deficiency is well-documented to impair neurological and cognitive processes, the effect of VitB6 supplementation on anxiety-related behaviour and sensorimotor function, and cortical neuronal activity in neurotypical populations has attracted interest in recent years due to the increasing number of diagnosed anxiety disorders globally. The work presented here used a cohort of young male adult Lister Hooded rats not deficient in VitB6. They were randomly assigned to a control and a VitB6 supplemented group. The VitB6 group were supplemented with ViB6 at 40 times the recommended dietary allowance (RDA) via drinking water for 5 weeks, with the control group for comparison. The open field test was used to assess anxiety-like behaviour, and rotarod tasks for motor coordination, while concurrent electrophysiological recordings from the barrel and motor cortices were used to evaluate neural activity. Serum VitB6 levels, dietary intake, and physiological parameters were also monitored. Our results indicated that VitB6-supplemented rats showed significantly reduced anxiety-like behaviour (fewer faecal boli and increased centre exploration in the open field) and exhibited enhanced sensorimotor performance (longer latency to fall on the rotarod) compared to control rats. However, no significant difference was detected in the neural activity of the barrel cortex between the groups in terms of the evoked local field potential (LFP), multi-unit activity (MUA), sensory adaptation, as well as resting state neural signals. As to the cortico-cortical phase relationship between the barrel and motor cortices, our results revealed that under whisker pad stimulation, the evoked neural response in the barrel cortex preceded that in the motor cortex, as expected. However, during resting state under the condition of slow wave oscillation (SWO), the Up state initiation was earlier in the motor cortex compared to the barrel cortex but returned to the baseline later, indicating a prolonged Up state phase in the motor cortex relative to the barrel cortex. Consistent with the earlier onset of Up states, the onset of burst during resting state of burst suppression in the motor cortex also preceded the barrel cortex. We further showed that these phase relationships between the barrel and motor cortices were not significantly different between the control and VitB6 groups. Our findings suggest that VitB6 supplementation may have positive outcomes in reducing anxiety and enhancing motor coordination even in healthy individuals, offering potential benefits for improving mental health and healthy living for the general population. However these behavioural differences didn’t result in significant differences between the control and VitB6 groups in terms of neural activities in the barrel cortex under whisker pad stimulation or resting state. Our study also provided new insights into neocortical communication and introduced a novel approach to investigate cortico-cortical network dynamics.