MIPFORACTION · Understanding the organisation of the medial parietal cortex: Sensorimotor integration for goal-directed behaviour

Understanding the organisation of the medial parietal cortex: Sensorimotor integration for goal-directed behaviour

The MIPforAction project, supported by the EU Marie Skłodowska Curie International Outgoing Action, addressed fundamental questions regarding the organization of primate parietal association cortex. The surface area of parietal cortex has expanded greatly in primates (including humans), and parietal subregions have no clear homologues in other mammals. We employed a multidisciplinary approach, making use of established anatomical and physiological methodologies, to study anatomical and functional characteristics of parietal cortex in monkeys. In addition, we used digital reconstructions of the brain surface as a means of visualization of cortical morphology and experimental data. The medial parietal cortex plays a key role in our ability to interact with the environment using our limbs, as demonstrated by the consequences of damage to this part of the brain. Although it is recognized that medial parietal cortex likely contains different architectonic areas, it still remains one of the least characterized brain regions. Ongoing work in non-human primates has revealed medial parietal regions (see attached Figure) specialized for particular sensorimotor actions, such as reaching and grasping; however, the exact contributions of different areas to sensorimotor behavior remain unclear. Moreover, the recent advances in non-invasive research in humans, which suggest the existence of parallel networks for limb actions in the human brain, emphasize the need for detailed descriptions of the cortical areas involved in coordinating skilled arm movements. The project aimed to provide a refined model of these areas, using anatomical tracing, histological reconstructions, and electrophysiological mapping of sensory activity. The main findings are as follows: First, medial parietal cortical areas form widespread connections with several brain areas, in the frontal, temporal, limbic, and local parietal cortices, emphasizing the associative features of the medial parietal cortex region. Second, the associative (i.e., neither strictly sensory nor motor) nature of this cortical sector is further suggested by the absence of connections with primary sensory cortices and general lack of purely sensory responses. Third, although links to premotor frontal cortex have been important in establishing the parietofrontal networks for limb movements, connections with less-studied parts of the brain are more difficult to interpret; for example, posterior temporal-parietal networks could possibly be related to shifts of attention to salient parts of the world, upon which an action might be directed. Fourth, by and large, the posterior parietal region appears to contain histologically defined areas with some overlap in connectivity patterns and function, adding to current theories of distributed information processing. In summary, present data, combined with our previous work on adjacent superior parietal areas, have provided a systematic view of the organization of cortical areas-components of networks for purposeful movement. Overall, project results expand our understanding of the areas that form the medial part of parietal association cortex and their respective contributions to sensorimotor behavior. This knowledge has the potential to provide insight regarding the cellular bases of neurological syndromes, including optic ataxia, and to enable future primate studies involving inactivation of specific areas to test clinical hypotheses. Importantly, understanding of the different contributions conveyed by medial parietal areas has the potential to guide accurate placement of prosthetic devices for the control of artificial limbs. This exciting modern field of research aims to assist patients suffering from brain lesions or degenerative disease by restoring a degree of motor abilities. Research findings have been presented in oral and abstract forms in meetings and in publications in international Peer Reviewed Journals with high impact; one additional publication is currently under revision; further analyses of data for two additional publications are in process after completion of experiments. It is important to note that experience with this type of methodologies of supervisors Profs. Fattori and Rosa and the Fellow, and close collaboration of the parties and staff at the University of Bologna and Monash University has been pivotal in collecting a large body of high-quality scientific data. An important aspect of the Fellowship, related to its international component, allowed the Fellow to highlight the collaborative nature of the project, particularly via joint presentations of research results to conferences and publications, and via joint co-supervision of students between UniBo and Monash. Equally important, engaging in research in a European and non-European country allowed the Fellow to obtain a broad perspective of current ethical considerations regarding animal studies.

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