This study found that the majority of differential brain areas between the group of volleyball players and the general population were concentrated in the visual system. Consistent results from metrics such as mALFF and zALFF showed involvement of the calcarine cortex, inferior temporal gyrus, and parahippocampal gyrus. These areas are associated with preliminary processing of external information, processing of visual features, object recognition and identification, perception of object and external spatial location. And the activation of the cerebellum is related to cognitive and sensory-motor functions. These findings are consistent with numerous behavioral studies by earlier researchers, demonstrating that after long-term specialized training, the brain plasticity of volleyball players undergoes beneficial changes in individuals[31, 32].
The results of ReHo further indicate the superior performance of volleyball players in visual information processing. The activity consistency in the bilateral primary visual cortex and the region surrounding the right cuneus was stronger in the athlete group, reflecting the enhanced visual processing ability in their brains compared to the general population. Furthermore, focusing on the differential brain areas in the bilateral primary visual cortex, we conducted whole-brain functional connectivity analysis at the voxel level. Our results further revealed that key connections in the brains of athletes, specifically between the bilateral primary visual cortex and the left primary somatosensory cortex and supplementary motor area, were significantly stronger compared to the novice group. Moreover, in terms of higher-level cognitive functions, the functional connectivity between the bilateral primary visual cortex and the right insula, left posterior cingulate cortex, and left precuneus was also significantly stronger in athletes compared to the novice group.
In a study involving 87 professional volleyball players and 67 non-athletes, it was found that athletes performed better in executive control tasks and visual-spatial attention processing tasks[17]. Additionally, in sports, the most efficient or skilled actions are considered optimal[11]. Athletes are able to predict the sensory outcomes of motor commands, integrate these predictions with actual sensory feedback, make judgments about their body and the external world based on this integration, and further adjust the sensorimotor feedback loop based on these judgments to optimize the cost and reward of movement and maximize performance[11]. These findings align with our research results, which indicate enhanced local activity in the primary visual cortex and increased functional connectivity between the primary visual cortex and somatosensory cortex, as well as the supplementary motor cortex and other brain regions involved in visual information processing, cognitive control, decision-making, and visual-spatial processing in volleyball players[30]. These changes optimize the brain's visual processing and body control during movement.
Although this study did not reveal statistically significant differences between the two groups in terms of auditory and visual reaction times, the correlation analysis between behavioral and imaging data did not show any statistical differences either. However, the differences between athletes and non-athletes have been well-established by other researchers[31]. Previous studies have shown that athletes perform better in their own specific sports compared to non-athletes. However, it does not necessarily mean that they will demonstrate the same superiority when switching to different sports[11]. This is similar to the findings of our experiment, which was an observational study. In our experiment, we tested the reaction times to sound and light using an audiovisual reaction device. This device was not part of the athletes' training, so they did not perform significantly better than the non-athlete group during the initial test. However, it is possible that the athlete group would show better performance after a period of training on the audiovisual reaction device. This would require further validation.
From the perspective of growth and development, there is a surge in synaptic generation in the visual areas before and after birth. Subsequently, the growth process primarily involves synaptic elimination, which relies on activity. Synapses are preserved in active brain cortex regions while gradually disappearing in inactive areas[33]. Through this process of synaptic pruning, the visual system can gradually self-regulate based on environmental demands and sensory input. This implies that targeted training in the early stages can preserve a greater number of synapses in the brain cortex associated with the trained activity, providing a solid neurological foundation in the corresponding training domain.
Based on previous research, the mechanism of exercise in regulating brain neuroplasticity involves the action of various neurotrophins, such as monoamines, brain-derived neurotrophic factor (BDNF), and Insulin-Like Growth Factor 1(IGF-1)[19]. Particularly, BDNF, as a primary brain plasticity modulator, exhibits heightened sensitivity to exercise. It not only regulates the central nervous system but also exerts certain control over the peripheral nervous system, with a more enduring impact compared to nerve growth factor(NGF), vascular endothelial growth factor(VEGF), and fibroblast growth factor 2(FGF-2).In addition to changes in neurotransmitters, the focal point of exercise-induced neural plasticity lies in the intermediation of synaptic genesis and dendritic spine formation. Exercise enhances synaptic genesis and dendritic spine formation in multiple brain regions, especially the hippocampus and somatosensory cortex[34]. Furthermore, exercise-induced synaptic-based long-term potentiation (LTP) is also considered a crucial aspect in influencing brain plasticity[35].
Some researchers have expressed doubts about the substantial benefits of early specialization in sports training for long-term youth development, and the underlying mechanisms remain unclear[36]. However, this study focused on volleyball athletes and found that, in terms of brain plasticity, early specialization training contributes to increased activation in the visual cortex of young individuals. It also strengthens functional connections between the visual cortex and multiple sensory, motor, and cognitive-related cortices. This reflects enhanced brain function in visual-motor processing, attention-movement regulation, and improved neural efficiency in areas related to executive control. Other studies have also found adaptations in visual and motor-related processes due to long-term training, including modifications in neural functioning, gray matter, and white matter structures[32]. This evident brain plasticity, along with the direct relationship between neural function and visual-motor response capabilities, offers significant potential for sports performance. And this unique ability of higher organisms to adapt to the environment by changing ourselves through learning and experience is specific to us. It is crucial in the process of evolution for our species[19]. Furthermore, other researchers have discovered that adolescents participating in team sports exhibit higher levels of life satisfaction, positive emotions, and self-esteem[36]. These findings provide further evidence for the cultivation of early sporting talent and broader youth development.
Furthermore, early researchers have found that the acquisition of individual skills not only affects brain activity but also leads to gray matter changes in many brain regions[11]. In our subsequent research, we will further investigate the structural changes in the brains of volleyball athletes compared to ordinary university students. This will allow us to explore the brain's adaptations resulting from skill acquisition in competitive sports training. If there are neuroplastic changes induced by prior sports training, it suggests that the use-dependent plasticity induced by training can contribute to brain function remodeling when facing issues such as disabilities requiring movement rehabilitation[37]. This highlights the beneficial role of early training in promoting the reconstruction of motor function following neural injuries.