Mansour Alyahyay
Published: 2023
Total Pages: 0
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Abstract: The ability to catch a ball involves a complex interplay between the premotor and motor cortices. The premotor cortex (PMC) generates a plan for the movement, taking into account the estimated trajectory and speed of the ball, while the primary motor cortex (M1) executes the movements required to intercept it. This intricate coordination between different cortical regions is crucial to successfully catch the ball. Similarly, when we walk on an uneven surface, the premotor areas are constantly monitoring our surroundings and generating a plan for the next step, while the primary motor cortex adjusts the respective muscles to maintain balance and avoid falling. This integration of sensory information and motor output is critical to the ability to navigate the environment around animals, and highlights the fundamental role of premotor and motor interaction in motor behavior. The brain is a complex network of neural circuits where information is processed and transformed to generate behavior. The development of the neocortex in mammals marked a significant milestone in brain evolution, as it plays a crucial role in mediating complex behaviors such as decision-making, sensation, and movement control (Harris and Shepherd, 2015). Understanding the organization of neural circuits and how they shape behavior is crucial for comprehending brain function. Neurons receive inputs from multiple sources and integrate them to produce outputs that are transmitted to other neurons or effector organs. The connectivity between neurons plays a crucial part in the flow of information within the neural circuit and ultimately the behavior of the animal (Kiritani et al., 2012). Here I looked into the communication between PMC and M1 in rats with the aim of looking at the interaction between motor areas in goal-directed behavior (Alyahyay et al., 2023). The work in this thesis provides mechanistic insights into the interactions between the cortical areas controlling the forelimb in rats, namely the rostral forelimb area (RFA) and the caudal forelimb area (CFA). Specifically, I provide evidence for a differential impact of RFA on CFA depending on the task period and the targeted CFA layers. RFA contained at least two spatially intermingled subpopulations - one related to movement preparation and one to movement execution. Both subpopulations project to CFA. Here I investigated the impact of these two subpopulations on the activity of the local circuit in CFA as well as on the behavior in different contexts. When rats were not involved in a task, RFA input was mainly excitatory in the deep CFA viii layers, while the superficial layers remained unaffected. This can be interpreted as a non-selective activation of the deep CFA neurons enabling a variety of spontaneous movements. In a preparation-movement task, the RFA had an opposite impact during the preparation period on the superficial and deep layers: while the superficial CFA layers were excited by RFA input, the deeper layers were mostly inhibited, minimizing movements and enabling continued holding of a lever. During the movement period, the inhibitory effect on neurons in the deep CFA layers was counterbalanced by excitation, thus enabling selective conduction of movements. With an electron microcopy (EM) approach, I demonstrated that inhibitory and excitatory CFA neurons are directly targeted by RFA, thus providing a mechanism for the control of CFA activity by RFA