Research objective: Regulation of brain activity by neurofeedback(NF)training has been widely applied in treatment of human psychological disorders,improvement of human cognitive performance and recently enhancement of brain-computer interfaces(BCIs)performance.Nevertheless,no study has investigated whether training the same EEG feature but with different training direction has the reverse effects on some performance.Regarding alpha neurofeedback,it has been demonstrated that alpha up-regulation NF has positive effects on short term memory enhancement while alpha down-regulation NF could improve steady state visual evoked potential BCI performance.However,it is unknown whether alpha down-regulation NF has side effects on short term memory.Thus,this study aimed to investigate: 1)whether multi-session NF training can decrease alpha activity and 2)whether this NF training has side effects in cognitive test of short term memory.Method: A total of 19 participants performed 10 sessions of individualized alpha down-regulation neurofeedback training with 5 sessions per day.Each session had three 1-min trials with an interval of 5 s between two consecutive trials.Before and after the 5 sessions of NF training in each day,three 30-s eyes open and three 30-s eyes closed resting baselines were recorded.9 in 19 participants performed forward and backward digit span as short term memory assessment before and after all training sessions.Participants were trained to decrease their amplitude in individual alpha band(IAB)which is defined as band ranges from peak alpha frequency(PAF)-4 Hz to PAF+2 Hz.Results: 14 out of total 19 subjects could decrease the training parameter,their IAB amplitude,over training sessions.In terms of the cognitive performance,neither forward nor backward digit span performance had significant change between before and after the alpha down-regulation neurofeedback training,indicating that this type of training has no side effects in short term memory.Discussion: Our previous study found short term memory improvement by alpha up-regulation NF.Thus,this research is interested in whether down-regulating alpha by NF has side effects on short term memory.The findings in this study provides evidence to the researchers that it is not necessary to worry about the short term memory performance when using down-regulating alpha NF to improve some specific performance such as implicit motor learning and reaction time.