Motor learning is supported by multiple systems adapted to processing different forms of sensory information (e.g., reward versus error feedback), and by higher-order systems supporting strategic processes. Yet, the extent to which these systems recruit shared versus separate neural pathways is poorly understood. To elucidate these pathways, we separately studied error-based (EL) and reinforcement-based (RL) motor learning in two functional MRI experiments in the same human subjects. We find that EL and RL occupy opposite ends of neural axis broadly separating cerebellar and striatal connectivity, respectively, with somatomotor cortex, and that alignment of this axis to each task is related to performance. Further, we identify a separate neural axis that is associated with strategy use during EL, and show that the expression of this same axis during RL predicts better performance. Together, these results offer a macroscale view of the common versus distinct neural architectures supporting different learning systems.

Twenty-six tumours of the mediastinum and hilar regions were examined by magnetic resonance; the technique and initial experience in distinguishing normal from pathological appearances are described. ECG triggering has proved essential, whereas respiratory triggering was found to be unnecessary. Spin-echo images were found to be best for tumour delineation but, for further characterisation, the inversion recovery mode and multi-echo technique were most satisfactory. In general, the space-occupying lesion was seen as well as it would be with CT. The advantages of the new method are the excellent differentiation of vascular structures and the ability to image in multiple planes, whereas CT possesses better resolution which, in some cases, may be of diagnostic advantage.