As the global human population grows older, a rising number of people are at great risk of developing memory-associated problems like amnesia, Parkinson's disease (PD), and Alzheimer's disease (AD), for which very limited therapeutic approaches are known [1]. The onset stage of memory loss during aging and AD is mild cognitive impairment (MCI), which shows a strong association with malnutrition. In order to assess the combinatorial potential of vitamins in memory during old and amnesic conditions, it is crucial to understand their impact on mitochondrial dynamics and associated metabolic pathways. The hippocampus is primarily involved in the formation and retrieval of long-term memories and in making those memories resistant to forgetting. It also plays an important role in spatial processing and navigation. The essential role of hippocampal mitochondria is to facilitate the processes of learning and memory [2]. Scopolamine causes short-term and long-term memory loss by blocking the muscarinic cholinergic receptors in the brain and interfering with learning and memory [3]. It shows its effects on the hippocampus by altering the synaptic transmission, disrupting the communication between neurons, and interfering with the processes that underlie memory formation contributing to long-term memory loss [4]. Mitochondrial malfunction is a prevalent characteristic in numerous genetic disorders that affect the brain and cognitive functions [5]. Mitochondrial health is prone to alteration in mitochondrial dynamics that regulate the mitochondrial movement along with the cytoskeleton and mitochondrial morphology and its distribution. The mitochondrial dynamics is disturbed by the age-dependent neurodegenerative disorders, and the equilibrium between fission and fusion may distress [6]. Mitochondria undergo regulated fusion and fission processes to modify their abundance and distribution within specific cells or subcellular regions with high energy demands. Additionally, these dynamic events enable mitochondria to actively scavenge other forms of damage caused by free radicals. Fission plays a crucial role in maintaining quality control within cells by segregating damaged mitochondria for degradation and promoting the generation of mitochondria. In contrast, fusion maintains mitochondrial function during aging and age-related neurodegenerative disease; fused mitochondria have the ability to compensate for damage to organelles by exchanging functional components [6].

Some of the "quasi-vitamins" and vitamins identified so far serve as cofactors that regulate foremost pathways accompanying neurodegenerative diseases [1]. The water-soluble B vitamins function as coenzymes and are important for brain health, but their efficiency in mitochondrial health is unclear [7]. Vitamin B12 plays a vital role as a micronutrient, participating in a wide range of biological processes. Efficient vitamin B12 absorption relies on intrinsic factors, the deficiency of which has been linked to neurological disorders [8]. Vitamin B12 deficiency is a condition that develops insidiously over a prolonged period, gradually affecting overall health. This deficiency has a preclinical stage, known as subclinical deficiency, characterized by non-specific symptoms, often underdiagnosed, and notably affecting vulnerable groups, especially older adults [9,10]. Vitamin B12 deficiency has been notably associated with cognitive decline, dementia, and various psychiatric disorders, including conditions characterized by suicidal behaviours, psychosis, mania, and intense agitation. A study conducted by Morris et al. reported cognitive decline in a cohort of 549 community-dwelling individuals, with a mean age of 74.8 years, who had low B12 serum levels. Furthermore, low B12 levels have also been linked to increased levels of inflammation, oxidative stress, and a heightened susceptibility to infections, which can cause apoptosis in a variety of cell types, while its supplementation avoids the onset of several disorders [11]. Additionally, vitamin B12 plays a vital role as a coenzyme in the metabolism of folate and the synthesis of nucleotides, thus being essential for the proper functioning of the nervous system and overall health [12,13]. Folic acid, one of the most important vitamins, has antioxidant qualities in addition to being required for the synthesis of purine and thymidylate. The deficiency of folic acid attributes to the emergence of numerous ailments including cancer, cardiovascular problems, foetal neural tube abnormalities and AD [14]. Previous reports indicated that vitamin B12 and folic acid synergistically promote neurological health through the methylation cycle, crucial for neurotransmitter production and nerve cell maintenance [15]. Co-administering vitamin B12 with folic acid improves function and synthesis of intrinsic factor, enhancing B12 absorption [16,17]. Although vitamin B12 and folic acid are known to function as cofactors and alter various pathways related to pathological conditions, the task of identifying and investigating the specific combination of vitamins that can more precisely and consistently aid in the prevention of memory loss remains poorly understood [1]. Therefore, it is imperative to investigate the impact of exogenous vitamin B12-folic acid administration on mitochondrial dynamics and memory during aging and age-related neurodegenerative diseases. In the current study, we have explored the potential role of vitamin B12-folic acid on mitochondrial fragmentation, mitochondrial dysfunction, neuronal cytoarchitecture, synaptic plasticity and memory in old and amnesic male mice.