background Cognitive abilities encompass multiple functions including learning, memory, and information integration, with their neural basis rooted in synaptic plasticity. Long-term potentiation (LTP) stands as the widely recognized core metric—this hallmark electrophysiological manifestation of synaptic plasticity reflects sustained enhancement in neuronal signal transmission efficiency. Higher LTP levels typically indicate stronger learning and memory capabilities. Research reveals that breastfed infants often demonstrate superior cognitive development compared to those fed traditional formula milk, a difference closely associated with the unique human milk oligosaccharides (HMOs). As one of the most abundant HMOs, 2’-fucosyllactose (2′-FL) not only plays roles in immune regulation and gut health but may also modulate neural functions and cognitive performance through the "gut-brain axis". This study evaluated 2′-FLs effects on hippocampal synaptic plasticity and cognitive abilities in rat models using electrophysiological and behavioral experiments, while exploring its mechanisms through vagotomy experiments. Research design and methods This study comprises two independent experiments. The first experiment employed a three-group design: a control group (Control), a fucose group (Fucose), and a 2′-FL experimental group. Under awake conditions, field excitatory postsynaptic potentials (fEPSPs) in the CA3–CA1 hippocampal pathway were recorded to quantify synaptic transmission efficiency, while high-frequency stimulation (HFS) was used to induce and track long-term potentiation (LTP). The second experiment utilized a four-group design to verify the necessity of the vagus nerve: control + sham surgery (Control-Sham: retaining the vagus nerve), control + vagotomy (Control-Vagotomized), 2′-FL + sham surgery (2′-FL-Sham), and 2′-FL + vagotomy (2′-FL-Vagotomized). In addition to recording LTP, operant conditioning was employed to assess learning performance. Key findings 1. 2′-FL enhances hippocampal synaptic plasticity In the three-group comparison of Experiment 1, the 2′-FL group demonstrated significantly higher and more sustained long-term potentiation (LTP) after high-frequency stimulation (HFS), outperforming both the control and fucose groups. This indicates that 2′-FL can substantially enhance synaptic connection strength, thereby improving learning and memory capabilities. No significant differences were observed between the fucose and control groups, suggesting that the intact 2′-FL molecule—rather than its fucose components—serves as the key mechanism underlying LTP enhancement. Figure 1: Long-term administration of 2′-FL enhances long-term potentiation (LTP) in the hippocampus of rats 2. 2′-FLs LTP-promoting effect depends on vagus nerve integrity In the four experimental conditions of Experiment 2, rats treated with 2′-FL-Sham showed significantly higher LTP levels than other groups. Notably, vagotomy not only reduced LTP but also eliminated the gain effect of 2′-FL, with 2′-FL-Vagotomized rats no longer outperforming control-Vagotomized rats. This directly demonstrates that the vagus nerve in the gut-brain axis is a necessary pathway for 2′-FL to exert its central effects. Figure 2: Long-term administration of 2′-FL enhances long-term potentiation (LTP) in the hippocampus of rats, though this beneficial effect depends on the integrity of bilateral vagus nerves. 3. 2′-FL improves operant conditioning performance while also depending on the vagus nerve In the operant conditioning task of Experiment 2, animals received food rewards by pressing a lever, with the target number of presses being achieved over multiple consecutive days considered as meeting the criterion. All four rat groups successfully met this learning standard. The 2′-FL-Sham group reached the target faster than both vagotomy groups, and demonstrated significantly higher daily press frequency during training compared to the 2′-FL-Vagotomized and Control-Vagotomized groups. After vagotomy, the behavioral advantage of 2′-FL disappeared, consistent with LTP findings, indicating that improvements in cognition-related learning and executive functions also depend on the integrity of the vagus nerve pathway. Figure 2: Long-term administration of 2′-FL enhances rats acquisition of operant conditioning tasks, but this positive effect depends on the integrity of bilateral vagus nerves. Discussion and outlook This study reveals the cognitive-enhancing effects of 2′-FL through both mechanistic and functional perspectives. On one hand, 2′-FL significantly enhances long-term potentiation (LTP) in the hippocampus, indicating its capacity to improve neuronal synaptic plasticity. On the other hand, it markedly improves learning speed and task performance in operant conditioning tasks. Notably, these effects disappear after vagotomy, suggesting that its action depends on intact gut-brain signaling. These findings not only validate the potential mechanism by which 2′-FL influences brain function via the vagus nerve, but also provide experimental evidence for the application of hydroxychalconoids (HMOs) in cognitive health. Future research could explore this mechanism across different developmental stages and cognitive impairment models, while integrating gut microbiota and metabolomics studies to further investigate its potential in brain health nutrition interventions. References [1] Vazquez, Enrique, et al. "Dietary 2’-fucosyllactose enhances operant conditioning and long-term potentiation via gut-brain communication through the vagus nerve in rodents." PloS one 11.11 (2016): e0166070.

  background The early development of the central nervous system is significantly influenced by nutritional factors. Research indicates that breastfeeding is associated with better cognitive development in infants, a difference partly attributed to the unique presence of human milk oligosaccharides (HMOs) in breast milk. Among these, 2’-fucosyllactose (2′-FL) – one of the most abundant HMOs – has been shown to regulate nervous system development through its effects on the gut-brain axis. This study investigates whether dietary supplementation with 2′-FL can enhance learning and memory performance by improving long-term potentiation (LTP) in the hippocampus and increasing synaptic protein expression, thereby providing experimental evidence for the brain function benefits of HMOs. Research design and methods The study was conducted on healthy male Sprague-Dawley rats, with two groups receiving either standard diet (control group) or diet supplemented with 2′-FL (2′-FL group, 250 mg/kg/day) for six weeks. During the intervention period, body weight and energy intake were monitored to exclude the interference of nutritional imbalance. Subsequently, spatial learning and memory abilities were assessed using the Morris water maze (MWM) test. Long-term potentiation (LTP) effects in the CA1 region of the hippocampus were evaluated through electrophysiological testing, a key indicator of synaptic plasticity that represents the biological basis of brain learning and memory. Additionally, immunoblotting was employed to detect the expression levels of synaptic plasticity-related proteins such as synaptophysin and postsynaptic density protein 95 (PSD-95), which are closely associated with synaptic structural stability and neural signal transmission. Key findings 1. 2′-FL enhances spatial learning ability In Morris water maze training, rats in the 2′-FL group showed significantly shorter escape latencies from days 3 to 5 compared to the control group, indicating accelerated learning. In spatial memory tests, they crossed the platform more frequently, demonstrating enhanced spatial memory. Figure 1: Effects of 2′-FL intervention on escape latency and platform crossing frequency in Morris water maze tests in rats 2. 2′-FL enhances LTP in the hippocampus Electrophysiological recordings revealed that the fEPSP slope in the CA1 region of the hippocampus in 2′-FL-treated rats significantly increased after high-frequency stimulation (HFS), indicating that 2′-FL enhances the formation of long-term potentiation (LTP) in the hippocampus. LTP, a process where synaptic connections between neurons progressively strengthen, is widely recognized as the neural basis for learning and memory formation. Therefore, the improvement in this indicator by 2′-FL suggests its potential to enhance cognitive performance. Figure 2: Changes in fEPSP slope in CA1 hippocampus of rats after 2′-FL treatment 3. 2′-FL upregulates the expression of synapse-associated proteins Compared with the control group, both synaptophysin and PSD-95 expression levels were significantly upregulated in the hippocampal tissue of 2′-FL-treated rats. Synaptophysin, a vesicle protein located in the presynaptic membrane, facilitates neurotransmitter release, while PSD-95 serves as a scaffold protein in postsynaptic structures, crucial for maintaining synaptic integrity and ensuring efficient signal transmission. These upregulations further demonstrate that 2′-FL enhances synaptic function, thereby supporting the neural mechanisms underlying learning and memory processes. Figure 3: Evaluation of 2′-FLs regulatory effects on Synaptophysin and PSD-95 expression levels by immunoblotting Discussion and outlook This study reveals the direct cognitive-enhancing effects of 2′-FL through brain mechanisms. By boosting neuroplasticity and synaptic protein expression in the hippocampus, it significantly improves spatial learning and memory in rats, further supporting the positive impact of HMO on brain development. These findings provide a solid scientific basis for 2′-FLs functional role in infant nutrition supplementation. Future clinical research during critical brain development periods could facilitate the practical application of HMO in childrens brain health products. References [1] Vázquez, Enrique, et al. "Effects of a human milk oligosaccharide, 2′-fucosyllactose, on hippocampal long-term potentiation and learning capabilities in rodents." The Journal of nutritional biochemistry 26.5 (2015): 455-465.