A fronto‐parietal circuit for object manipulation in man: evidence from an fMRI‐study

In an event-related fMRI study, we investigated the neural correlates of visual dimension and response changes. We used a compound task, which required target selection by a singleton feature, a unique color or motion direction, before the appropriate motor response, which was determined by target orientation, could be selected. Both types of change elicited distinct patterns of activation, with dimension-changerelated activation primarily in posterior visual areas and responserelated activation primarily in motor-related areas of the parietal and frontal cortices. Response-change-related activation was delayed by about 1 s relative to dimension-change-related activation, suggesting that the latter is elicited by perceptual processes, whereas the former reflects response-related or post-response processes. Although dimension changes and response changes rely on different processes, they are not independent: response facilitation was observed for combined dimension and response repetitions, this facilitation, however, was disrupted by dimension changes. D

Abstract.[Purpose] The aim of this study was to verify frontal lobe activity in healthy individuals during the performance of spatial tasks as part of a cognitive therapeutic exercise.[Subjects] Twelve healthy young adults participated in the experiment.[Methods] The spatial tasks were to differentiate the sizes of circles with different diameters. In actual practice, a therapist held the upper limbs of an experiment participant and passively traced 5 randomly appearing circles of differing sizes by moving only the participant's shoulder joint and then had the participant determine the order of the circles. Under control conditions, the participant was not asked to make this determination. Under both experimental and control conditions, the experiment participant was asked to close his or her eyes during the tasks. Functional nearinfrared spectroscopy (fNIRS) was used for measurement, and relative changes in blood flow in the frontal lobe were measured.[Results] Blood flow in the premotor cortex and dorsolateral prefrontal cortex increased significantly (p<0.05) under spatial task conditions in comparison to control conditions.[Conclusion] This result suggests that the premotor cortex, which is responsible for motor learning, and the dorsolateral prefrontal cortex, which is responsible for working memory function, are activated during the performance of spatial tasks as part of cognitive therapeutic exercise.

The execution of movements that are guided by an increasingly complex target motion is known to draw on premotor cortices. Whole-brain functional magnetic resonance imaging was used to investigate whether, in the absence of any movement, attending to and predicting increasingly complex target motion also rely on premotor cortices. Complexity was varied as a function of number of sequential elements and amount of dynamic sequential trend in a pulsing target motion. As a result, serial prediction caused activations in premotor and parietal cortices, particularly within the right hemisphere. Parametric analyses revealed that the right ventrolateral premotor cortex and the right anterior intraparietal sulcus were the only areas that, in addition, covaried positively with both behavioral and physical measures of sequential complexity. Further areas that covaried positively with increasing task difficulty reflected influences of both number and trend manipulation. In particular, increasing element number drew on dorsal premotor and corresponding posterior intraparietal regions, whereas increasing trend drew on the visual motion area and area V4. The present findings demonstrate that premotor involvement directly reflects perceptual complexity in attended and predicted target motion. It is suggested that when we try to predict how a target will move, the motor system generates a "blueprint" of the observed motion that allows potential sensorimotor integration. In the absence of any motor requirement, this blueprint appears to be not a byproduct of motor planning, but rather the basis for target motion prediction.