Apparatus and methods for efficient synaptic update in a network such as a spiking neural network. In one aspect, the system presented has a poultry stunner defining a partially enclosed passageway and at least one first conduit in fluid communication with the fluid source, configured to direct a first stream of fluid into at least a portion of the at least partially enclosed passageway. The present invention provides useful materials and methods for reducing such reflection or re-radiation effects, leading to temperature stability of the substrate, reduced thermal distortion and the possibility of increased patterning accuracy. Such a path-based row source may be modified to use the predicate condition to filter the rows it generates so that only rows satisfying the predicate condition need to be further processed.