# Perceptual Judgments for Table Tennis Serve Recognition: An Event-Related Potentials Study
## 4 Discussion  
We hypothesized that table tennis athletes and undergraduates would show differences in performance and ERPs components during recognizing the type of serves. In agreement with our predictions, table tennis athletes were quicker and/or more accurate than undergraduates when they recognized the type of serves by hitting location. Table tennis athletes probably developed more elaborate domain-specific knowledge structures or patterns to rapidly encode information in their memories through many hours of practice and match play [17]. Our results indicated that table tennis players can use key information to make accurate judgments. For the table tennis athletes group, the ERPs results clearly showed an early negative component around 45-65 ms post-standard stimulus at the occipital region of the scalp topography. This component was named the C1 component in previous studies [18]. Compared with the undergraduates' group, table tennis athletes had an earlier latency and greater amplitude of the C1 component. This component reflected the early activity of the primary visual cortex (V1) for very early sensory processing. The current study probably revealed that the C1 component is modulated by long-term practice and match play; in particular, for speed-ball games such as table tennis, athletes were highly demanded in visual perceptual processing. A recent find proposed that the experience-induced brain plasticity in the primary visual cortex results in a greater C1 component for badminton players [9]. The present study showed that table tennis athletes were very sensitive to domain-specific knowledge structures or patterns (e.g., hitting location), and the greater C1 component appeared in the primary visual cortex for very early sensory processing. Another positive component was indexed at the occipital region of scalp topographies for two groups by standard stimuli, whose time window was from 80 to 150 ms. Thiscomponent was interpreted as P1 and was connected with the location of visual spatial selective attention. According to the selective attention theory, the attention to the location of objects plays an important role in the early stage of perceptual coding, which avails to recognizing the objects' characteristics [19]. Compared with the undergraduates group, table tennis athletes had a later latency and greater amplitude of the P1 component. The previous study found that individuals can voluntarily allocate significant amounts of attention to particular locations in the visual field while fixating on a central focal point [20]. Another study believed that the strengthened P1 could be related to the auto-processing of attention orientation caused by suddenly appearing visual events [21]. [PERSON] et al. (2005) [22] found the differences in P1 amplitude between volleyball players and non-players. The current result showed that table tennis athletes had devoted more attention for the early visual processing of the location of objects. Around 90-160 ms post-target stimulus at central sites (e.g., Cz, C3 and C4), a clearly negative component was evoked, which was called N1. According to the previous research results, table tennis athletes' greater N1 component maybe reflect the discrimination processing of attention focusing on features of target stimuli [23]. These results were in line with previous studies on N1 elicited by recognizing motion pattern [13]. The researchers generally believed that the more time devoted in the stage of visual working memory coding and retention, the more elaborately the current processing was made. The current results showed that table tennis athletes could distribute more attention resources to prepare for the later elaborate processing and accurate recognizing. The most noticeable difference between the ERPs profiles of table tennis athletes and undergraduates was in their P3 component changes around 300-500 ms post-target stimulus at central sites (e.g., Cz, C3 and C4). Table tennis athletes exhibited a greater P3 amplitude in a shorter latency than undergraduates.