The posterior parietal cortex of human and non-human primates has been implicated in sensorimotor transformations, whereby sensory input (vision, touch, sound) is converted into motor commands. For instance, visual information regarding a target can be used to appropriately guide reaching movements towards the relevant part of space. These sensorimotor and multisensory representations suggest that the role of the posterior parietal lobe is to implement perception for action, rather than create a passive, purely perceptual representation of space. This dissertation consists of three different studies that map such multimodal and sensorimotor representations in the human brain, using functional magnetic resonance imaging (fMRI). The first study shows that observation, imagery, and execution of reaching rely on similar neural substrates in the posterior parietal lobe, specifically involving more superior (dorsal) areas. These 'mirror neuron' activations are in agreement with macaque parieto-frontal circuits underlying reaching movements, and differ from the more ventral (inferior) activations for grasping or for hand- object interactions. This suggests that (visuomotor) mirror neurons are specific to the hand action that is executed (reaching versus grasping). The second study attempts to dissociate visual and proprioceptive feedback from the reaching hand, to identify visuomotor and proprioceptive-motor areas involved in the control of reaching. Reaching without visual feedback from the moving hand involves more anterior and medial parietal areas than reaching with visual feedback. This indicates a posterior- to-anterior organization for sensorimotor representations that use visual versus somatosensory input, respectively, within posterior parietal cortex. Finally, the third study investigates tactile and visual representations of target location. Identifying target location using exploratory hand movements in the absence of visual input activates similar intraparietal and superior parietal areas as does visual identification of spatial location. The common activation by visual and tactile input suggests multisensory processing in these areas

Previous functional magnetic resonance imaging (fMRI) research on action observation has emphasized the role of putative mirror neuron areas such as Broca's area, ventral premotor cortex, and the inferior parietal lobule. However, recent evidence suggests action observation involves many distributed cortical regions, including dorsal premotor and superior parietal cortex. How these different regions relate to traditional mirror neuron areas, and whether traditional mirror neuron areas play a special role in action representation, is unclear. Here we use multi-voxel pattern analysis (MVPA) to show that action representations, including observation, imagery, and execution of reaching movements: (1) are distributed across both dorsal (superior) and ventral (inferior) premotor and parietal areas; (2) can be decoded from areas that are jointly activated by observation, execution, and imagery of reaching movements, even in cases of equal-amplitude blood oxygen level-dependent (BOLD) responses; and (3) can be equally accurately classified from either posterior parietal or frontal (premotor and inferior frontal) regions. These results challenge the presumed dominance of traditional mirror neuron areas such as Broca's area in action observation and action representation more generally. Unlike traditional univariate fMRI analyses, MVPA was able to discriminate between imagined and observed movements from previously indistinguishable BOLD activations in commonly activated regions, suggesting finer-grained distributed patterns of activation.

There is a great deal of discussion about whether people intuitively seek to falsify their working hypothesis. But therehas been little consideration of the relationships between falsificationist and probabilistic Optimal Experimental Design(OED) approaches to evaluating the usefulness of possible experiments. Recent work has shown that a variety of importantOED and heuristic models can be derived as special cases of the generalized Sharma-Mittal framework of information gainmeasures. We show how falsification-like behavior can also derive from a quasi-information gain model, based on high-degree Tsallis entropies. Our analysis shows that falsificationist and probabilistic approaches are not as far apart as theeast and the west. Rather, they can be built out of virtually the same set of ingredients, within a probabilistic framework.We report simulation studies showing how important falsificationist, OED, and hybrid models could be differentiated aspossible descriptive accounts of information-seeking behavior.