Hebbian Plasticity for Improving Perceptual Decisions
  Shibata et al. reported that humans could learn to repeatedly evoke a stimulus-associated functional magnetic resonance imaging (fMRI) activity pattern in visual areas V1/V2 through which visual perceptual learning was achieved without stimulus presentation. Contrary to their attribution of visual improvements to neuroplasticity in adult V1/V2, our Hebbian learning interpretation of these data explains the attainment of better perceptual decisions without plastic V1/V2. 
Tsung-Ren Huang
q-bio.NC