https://www.mathworks.com/help/deeplearning/ref/nnet.cnn.layer.prelulayer.html
PReLULayer - Parametrized rectified linear unit (PReLU) layer - MATLAB
A PReLU layer performs a threshold operation, where for each channel, any input value less than zero is multiplied by a scalar learned at training time.
rectified linear unitparametrizedlayermatlab