OBJECTIVE: It is well known that to acquire sensorimotor (SMR)-based 
brain-computer interface (BCI) control requires a training period before users 
can achieve their best possible performances. Nevertheless, the effect of this 
training procedure on the cortical activity related to the mental imagery 
ability still requires investigation to be fully elucidated. The aim of this 
study was to gain insights into the effects of SMR-based BCI training on the 
cortical spectral activity associated with the performance of different mental 
imagery tasks.
APPROACH: Linear cortical estimation and statistical brain mapping techniques 
were applied on high-density EEG data acquired from 18 healthy participants 
performing three different mental imagery tasks. Subjects were divided in two 
groups, one of BCI trained subjects, according to their previous exposure (at 
least six months before this study) to motor imagery-based BCI training, and one 
of subjects who were naive to any BCI paradigms.
MAIN RESULTS: Cortical activation maps obtained for trained and naive subjects 
indicated different spectral and spatial activity patterns in response to the 
mental imagery tasks. Long-term effects of the previous SMR-based BCI training 
were observed on the motor cortical spectral activity specific to the BCI 
trained motor imagery task (simple hand movements) and partially generalized to 
more complex motor imagery task (playing tennis). Differently, mental imagery 
with spatial attention and memory content could elicit recognizable cortical 
spectral activity even in subjects completely naive to (BCI) training.
SIGNIFICANCE: The present findings contribute to our understanding of BCI 
technology usage and might be of relevance in those clinical conditions when 
training to master a BCI application is challenging or even not possible.