Abstract:

The filtering efficiency is the mechanism to inhibit irrelevant items from entering visual working memory. Studies have shown that it can be measured by using Change Detection Task which contains extra distracters (based on working memory capacity) or Color Recall Task (based on representation precision). The paradigm of the former is relatively mature, including the behavioral and cognitive neurological level whereas the latter has begun to gain attention in recent years,which support the variable precision resource model. 
The neural processes underlie filtering efficiency are presence of distractors, initiation of filtering, and filtering success/unnecessary storage, which are orchestrated by the prefrontal cortex and the basal ganglia, the posterior parietal cortex. Nowadays, researches have been made to use transcranial direct current stimulation(tDCS) technology to find out that electrically stimulating the parietal cortex helped working memory capacity increase effectively. However, there are few studies on electrical stimulation of the prefrontal cortex to improve filtering efficiency and the results lack consistency, which deserves further attention. 
The life-long development characteristic of filtration efficiency is partly similar to an inverted U-shaped curve: it develops rapidly in adolescence, and after reaching its peak in early adulthood, it shows a downward trend, but there will be no very obvious decline.There are same and different from the characteristic that fluid intelligence declines with age after adulthood: the same is that both filtering effciency and fluid intelligence will decline after reaching the peak, and the difference is that the decline in filtering efficiency is slower than that of fluid intelligence. It may be because the elderly have activated a wider area of the brain to compensate for the filtering efficiency.This assumption can be verified by longitudinal tracking studies or comparisons of all age groups.
Special disorders (such as Parkinson's disease, trait anxiety, depression, attention deficit and hyperactivity disorder, autism spectrum disorder and schizophrenia) and negative emotional factors mainly cause the damage and weakening of filtering efficiency.The cognitive style of independent analysis, the thinking mode that grasps the essence of information, and the high representation accuracy are beneficial to the filtering efficiency. At the same time, adding clues and regulate training can also effectively improve the filtering efficiency.
Problems that need to be solved in future research include clarifying the causal relationship between filtration efficiency and working memory capacity. Discerning whether the psychological realization process of filtering effectiveness is through increased attention to the target item or the inhibition of distracted items, or both? Exploring the differences in the brain mechanism of the filtering efficiency of groups of different ages, special obstacles and occupations. Improving the ecological validity of basic research paradigms by changing experimental materials, difficulty, and applying virtual reality technology.

Key words: filtering efficiency, visual working memory, neural mechanism