Figure 9.

Comparing anatomical and functional representations in premotor cortex. We compared the differences of arm and hand AUROCs with the differences of reach and grasp AUROCs to determine whether there was a systematic relationship such that cells that encoded arm kinematics preferentially likewise encoded reaching synergies and, similarly, cells that encoded hand kinematics preferentially likewise encoded grasping synergies. A, Expected results based on the dual-channels hypothesis. PMd would be concerned exclusively with arm kinematics and reaching, whereas PMv would be concerned with hand kinematics and grasping. There would be a segregation of both function and anatomy between PMd and PMv. B, Actual results based on observed data. A χ² test of independence revealed no significant relationship between functional and anatomical encoding preferences. C, Comparing the relative encoding performance of anatomical and functional models. Here, we show the distribution of the logarithm of the ratio of arm and reach model AUROCs. If the log of this ratio is positive, then the arm model had a higher AUROC than the reach model and vice versa for negative values. We found that both PMd and PMv are better predicted by anatomical features rather than functional features, but this preference is stronger in PMd (see main text for additional statistics). D, Same conventions as C, but using hand and grasp models.