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The aim of this study was to identify the cerebral areas activated during kinematic processing of movement trajectories. We measured regional cerebral blood flow (rCBF) during learning, performance and imagery of right-hand writing in eight right-handed volunteers. Compared with viewing the writing space, increases in rCBF were observed in the left motor, premotor and frontomesial cortex, and in the right anterior cerebellum in all movement conditions, and the increases were related to mean tangential writing velocity. No rCBF increases occurred in these areas during imagery. Early learning of new ideomotor trajectories and deliberately exact writing of letters both induced rCBF increases in the cortex lining the right intraparietal sulcus. In contrast, during fast writing of overlearned trajectories and in the later phase of learning new ideograms the rCBF increased bilaterally in the posterior parietal cortex. Imagery of ideograms that had not been practised previously activated the anterior and posterior parietal areas simultaneously. Our results provide evidence suggesting that the kinematic representations of graphomotor trajectories are multiply represented in the human parietal cortex. It is concluded that different parietal subsystems may subserve attentive sensory movement control and whole-field visuospatial processing during automatic performance.

SUMMARY Classical conditioning is one of the most fundamental forms of learning, and yet little is known regarding the effects of brain injury on conditioning processes in humans. Three patients with temporal lobe lesions and severe memory problems were therefore assessed in terms of eyeblink conditioning, extinction, discrimination and reversal learning, and in one patient electrodermal conditioning was also investigated. The acquisition of conditioned responses was seen to be intact, but the evidence regarding extinction was ambiguous. All of the patients were impaired in discrimination learning and also reversal learning.Classical conditioning is one of the most fundamental forms of learning, and has been important in theories of both experimental psychology' and clinical psychology.2 Classical conditioning techniques have also been extensively applied in pharmacological research3 and have formed the basis of many early neuropsychological investigations into the effects of brain lesions in animals.4 It is known, for instance, that classical conditioning can survive even complete cerebral decortication in the rat and the rabbit,56 although in these same animals classical conditioning may be abolished or impaired following lesions of the cerebellum' or limbic structures.8 9 It is therefore surprising that little is known about classical conditioning in the brain-injured human, especially since a great deal is known about classical conditioning in healthy subjects.'' " To our knowledge only two attempts have been made to study classical conditioning in patients with brain lesions. The first was a single case study involving H.M., the well-documented patient who suffered total anterograde amnesia following bilateral mesial resection of the temporal lobes.'2 H.M., however, failed to show phasic electrodermal responses to the unconditioned stimulus (UCS), an electroshock, in a procedure designed to condition the galvanic skin response to a neutral stimulus, and thus Address for reprint requests: Irene Daum, Department ofPsychology,

The study examines the nature of the influence that the basal ganglia exert on frontal cortex via the motor nuclei of the thalamus. Twelve monkeys were trained to pull a handle given one colour cue and to turn it given another. Bilateral lesions were then placed in the ventral thalamus. Four monkeys with large anterior lesions including the VA nucleus and the anterior part of VLo were severely impaired at relearning the task. Monkeys with small lesions in VAmc or with lesions centred on VLo were not impaired. The analysis of the histology suggests that the impairment in the four monkeys did not result from involvement of the cerebellar relay through nucleus X. It is argued that the animals are not impaired because of faulty execution. This suggests that the basal ganglia have an influence on motor learning.

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