The Cerebellar Nuclei (CN) are the sole output of the cerebellum, integrating and relaying information computed in the cerebellar cortex and transmitted by Purkinje cells, before sending it to the downstream targets of the cerebellum. The cerebellum receives two types of afferents: mossy fibers (sensory-motor context) and climbing fibers (teaching signals). These inputs project to the cerebellar cortex, with some also sending direct excitatory collaterals to the CN. However, little is known about the functional properties and the impact of these excitatory inputs on the firing of cerebellar nuclei. Not all cerebellar inputs form collaterals on the CN, and it is currently unknown whether inputs from different origins have distinct functional properties. We aim to characterize the properties and impact of these inputs depending on their source and target, to understand the role of these direct inputs that bypass cortical processing. To study the different sources of excitatory inputs, several populations of inputs projecting collaterals into the anterior interposed nucleus were labeled with stereotaxic injections. We selected the Red Nucleus, the Pons, and the Inferior Olive as our main targets, as they constitute major inputs in this nucleus. Short-term plasticity profiles are being investigated through voltage-clamp experiments by patching Anterior Interposed Nucleus (AInt) neurons and using 2-photon targeted minimal stimulations of the input fibers. Preliminary results suggest that while most synapses depress, heterogeneous short-term plasticity profiles can be observed on individual neurons.