Layer 4 neurons are the first cortical station that receives sensory information from the external world. The main recipients of this sensory input are the spiny stellate neurons. Thus, these neurons play a significant role in sensory information processing. However, the active mechanisms that are used by spiny stellate dendrites for shaping sensory responses are still unknown. This work investigates the active dendritic properties of layer 4 spiny stellate neurons by means of whole cell recordings, dendritic calcium imaging and glutamate uncaging in the thalamocortical slice preparation. The findings suggest that local and global dendritic spikes can amplify convergent thalamocortical and cortico-cortical inputs to layer 4 neurons and, thus, may have a substantial function in modulating the sensory signal transmitted by the thalamus.