Learning- and expectation-related changes in the human brain during motor learning

We have studied a simple form of motor learning in the human brain so as to isolate activity related to motor learning and the prediction of sensory e vents. Whole-brain, event-related functional magnetic resonance imaging (fM RI) was used to record activity during classical discriminative delay eyebl ink conditioning. Auditory conditioned stimulus (CS+) trials were presented either with a corneal airpuff unconditioned stimulus (US, paired), or with out a US (unpaired). Auditory CS- trials were never reinforced with a US. T rials were presented pseudorandomly, 66 times each. The subjects gradually produced conditioned responses to CS+ trials, while increasingly differenti ating between CS+ and CS- trials. The increasing difference between hemodyn amic responses for unpaired CS+ and for CS- trials evolved slowly during co nditioning in the ipsilateral cerebellar cortex (Crus I/Lobule HVI), contra lateral motor cortex and hippocampus. To localize changes that were related to sensory prediction, we compared trials on which the expected airpuff US failed to occur (Unpaired CS+) with trials on which it occurred as expecte d (Paired CS+). Error-related signals in the contralateral cerebellum and s omatosensory cortex were seen to increase during learning as the sensory pr ediction became stronger. The changes seen in the ipsilateral cerebellar co rtex may be due either to the violations of sensory predictions, or to lear ning-related increases in the excitability of cerebellar neurons to present ations of the CS+.