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There has been some discussion concerning the nature of luminosity pulses observed during the continuing currents of positive cloud-to-ground flashes. It still undefined whether or not these pulses can be considered M components when compared to similar events observed in negative flashes. In the present paper we expand this discussion by analyzing electric field waveforms associated with channel luminosity enhancements of both negative and positive ground flashes. Typically, negative M components are preceded by high-frequency pulses similar to those that can are associated to recoil leaders that are visible below cloud base. On the other hand, luminous processes in positive flashes (similar to M components) did not present a particularly common electric field signature, and no pulses could be positively correlated to their inception inside the cloud. We believe that this polarity asymmetry favors previous theories on the production of negative M components according to the bidirectional leader model. The distinctive features of the positive M components suggest that they are related to different processes.