In a second step, researchers tested how the manipulation of deep sleep affected the motoric learning tasks on the following day. Here, they observed how the learning and performance curves of the test subjects changed over the course of the experiment. As expected, the participants were particularly able to learn the motoric task well in the morning. As the day went on, however, the rate of mistakes rose. After sleep, the learning efficiency considerably improved again. This was not the case after the night with the manipulated sleep phase. Here, clear performance losses and difficulties in learning the finger movements were revealed.
Learning efficiency was similarly as weak as on the evening of the first day of the experiment. Through the manipulation of the motor cortex, the excitability of the corresponding synapses was not reduced during sleep. “In the strongly excited region of the brain, learning efficiency was saturated and could no longer be changed, which inhibited the learning of motor skills,” Nicole Wenderoth explains.
In a controlled experiment with the same task assignment, researchers manipulated another region of the brain during sleep. In this case, however, this manipulation had no effect on the learning efficiency of the test subjects.