De Vitis Marina, Filippini Matteo, Hadjidimitrakis Kostas, Vaccari Francesco Edoardo, Diomedi Stefano, Gamberini Michela, Gori Martina, Testa Michele, Galletti Claudio, Fattori Patrizia
Department of Biomedical and Neuromotor Sciences - DIBINEM, University of Bologna, Italy.
Department of Biomedical and Neuromotor Sciences - DIBINEM, University of Bologna, Italy; Alma Mater Research Institute for Human-Centered Artificial Intelligence, University of Bologna, Italy.
Neuroimage. 2025 Sep;318:121387. doi: 10.1016/j.neuroimage.2025.121387. Epub 2025 Jul 21.
Neuronal populations in parietal and frontal cortices orchestrate a series of visuomotor transformations crucial for executing successful reaching movements. Two key nodes in this network are the dorsal premotor area F2 and the medial posterior parietal area V6A, which are strongly reciprocally connected (Gamberini et al., 2021). Extensive research in premotor areas primarily focused on center-out reaches, which did not account for reach depth. Therefore, it is unknown whether tuning by spatial and motor variables, such as reach direction and depth, is similar in frontal and parietal cortices and whether there are differences in the temporal evolution of activity that reflects functional specializations. To fill this gap, we recorded single-neuron activity from two regions of the medial fronto-parietal circuit in macaques performing an instructed delay reaching task toward targets varying in both direction and depth. We then compared how various spatial and temporal movement parameters are represented both at the neural and population levels across these two network nodes. Our results reveal that neurons in the medial posterior parietal cortex (mPPC) exhibit sharper spatial tuning, with a particularly robust representation of target depth, compared to the broader, more gradual activation patterns observed in the dorsal premotor cortex (PMd). Moreover, greater decoding accuracy for direction and depth has been found in mPPC. These findings suggest that mPPC is specialized for accurate and reliable spatial encoding that is essential for dynamic sensorimotor transformations, whereas PMd may primarily support the planning and initiation of motor actions directed toward a continuum of spatial locations.
顶叶和额叶皮质中的神经元群体协调一系列视觉运动转换，这些转换对于成功执行伸手动作至关重要。该网络中的两个关键节点是背侧运动前区F2和顶叶后内侧区V6A，它们之间有强烈的相互连接（甘贝里尼等人，2021年）。对运动前区的广泛研究主要集中在从中心向外的伸手动作上，而没有考虑伸手的深度。因此，尚不清楚额叶和顶叶皮质中由空间和运动变量（如伸手方向和深度）进行的调谐是否相似，以及反映功能特化的活动时间演变是否存在差异。为了填补这一空白，我们记录了猕猴内侧额顶叶回路两个区域的单神经元活动，猕猴在执行一项指令延迟伸手任务，目标在方向和深度上都有所不同。然后，我们比较了这两个网络节点在神经和群体水平上如何表示各种空间和时间运动参数。我们的结果表明，与在背侧运动前皮质（PMd）中观察到的更广泛、更渐进的激活模式相比，顶叶后内侧皮质（mPPC）中的神经元表现出更敏锐的空间调谐，对目标深度的表示尤为强烈。此外，在mPPC中发现了更高的方向和深度解码精度。这些发现表明，mPPC专门用于精确可靠的空间编码，这对于动态感觉运动转换至关重要，而PMd可能主要支持针对一系列空间位置的运动动作的规划和启动。
