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A New View on Real Actions: Neural Mechanisms of Visuo-Motor Transformations

Periodic Reporting for period 1 - BraIn Action (A New View on Real Actions: Neural Mechanisms of Visuo-Motor Transformations)

Reporting period: 2016-10-01 to 2018-09-30

The main objective of the project BraIn Action was aimed to use neuroimaging and neurostimulation techniques to investigate whether the Early Visual Cortex (EVC), a brain region known to process visual information, plays a role in planning actions even when vision is not available. The importance of studying actions lies on the fact that they are essential to satisfy our basic needs, and they are also the only way we have to affect the world around us. While the majority of studies that investigated the brain regions involved in actions have focused on areas typically known to play a role in motor control, such as motor and premotor cortices as well as associative areas, the involvement of the EVC has been relatively neglected.

When we plan movements, our brain needs to anticipate the sensory consequences of the upcoming actions through mechanisms of predictive coding. Predictive functions are necessary as they enable us to adjust our own movements according to rapid changes in the environment. This is crucial given the unavoidable delays in our sensory and motor processing systems. In addition, predictive mechanisms allow us to distinguish the sensory consequences of our own actions from external factors. Impairments in predictive mechanisms can affect a variety of mental functions that encompass the domains of action, perception and cognition. However, the neural basis that underlie predictions as well as the cortical areas involved in this process are still poorly understood.

The major cause of permanent movement disabilities arises from brain disorders originating from brain injuries, strokes, autoimmune diseases and other devastating illnesses that affect the central nervous system. Patients suffering the consequences of these debilitating events are left with the inability to coordinate actions. In particular, the affected aspects are visuo-motor coordination and memory retrieval, which consists of the ability to store and retrieve visual information from memory in order to guide our intentions and subsequent actions.

BraIn Action has contributed to push forward the knowledge about the functional architecture of the action network in the brain of neurologically intact individuals. By starting from well-functioning models, we can develop a deep understanding about dysfunctional ones and gain insights into rehabilitative strategies.
BraIn Action was aimed to combine functional Magnetic Resonance Imaging (fMRI) and Transcranial Magnetic Stimulation (TMS) techiques to investigate: 1) whether the activity pattern in the EVC can be used to decode action intention even in absence of visual information, 2) the functional connections between the EVC and the rest of the brain during action planning, 3) the causal role of the EVC in action planning, and 4) whether the role of the EVC in action planning can be due to motor imagery.

The results of BraIn Action consistently show that the preparatory activity in the EVC can be reliably used to predict what movement participants will perform within a few seconds, even in absence of online visual information. Further, action intention modulates the representation of object features in the EVC. Therefore, the EVC plays a role in predictive coding for action by anticipating the visual consequences of our own movements even when vision is not available, and by shaping the cortical representation of object properties. In addition, when we plan an action the EVC intensifies its functional connections with brain areas that are typically known to be involved in motor control and object perception. Further, action planning and motor imagery have overlapping but not identical substrates, suggesting that imagery alone cannot explain the effects observed in the EVC. The causal role of the EVC in action planning is still being investigated with the use of TMS.
BraIn Action has brought new insights that are relevant to better understand the neural networks underlying actions, and, in the long term, can contribute to the development of rehabilitation strategies for patients with motor impairments. The understanding of how sensory expectations are processed for planning simple actions, such as grasping an object, is a step forward into a more comprehensive view of the neural mechanisms involved in motor control. In addition, the findings of BraIn Action might explain the neural processes by which action imagery can be used to improve motor performance in patients and athletes, as well as for controlling prosthetic devices by imagining the final goal of the effector. In summary, BraIn Action paves the way for future investigations on action planning in patients with motor impairments or sensory deprivations.