Motivational links, however, could be modified by reinforcement. If a certain action leads to reward, strengthen the links that led to that action; if it leads to punishment, strengthen the links that would have made you avoid that action.

Reward comes along too much later for this to work for humans. Instead, the brain uses temporal difference learning. I no longer remember what was the first, classic paper demonstrating temporal difference error signals in the brain; it may have been A Neural Substrate of Prediction and Reward (1997). Google ("temporal difference learning", brain). "Temporal Difference Models and Reward-Related Learning in the Human Brain" , Neuron, 2003, will be one of the hits.