Locus of response slowing resulting from alternation-based processing interference

In serial reaction time (RT) tasks, performance is strongly influenced by previous events. RT in Trial N is much slower after response changes than response repetitions from Trial N-2 to Trial N-1 when response-stimulus interval is short (I. Jentzsch & H. Leuthold, 2005). The aim of the present study was to investigate the mechanisms leading to this slowing by contrasting the idea of a hard bottleneck, postponing all subsequent processing, with a selective prolonging of postperceptual stages. We analyzed the lateralized readiness potential (LRP) and peak latencies of P1, N1, and P300 components in a choice RT task mapping four stimuli to two responses. Alternation-based interference affected the S-LRP interval but neither the LRP-R interval nor the latency of P1, N1, and P300. These findings suggest that, whereas alternation-based conflict originates at response-related stages, postconflict slowing selectively affects central, premotoric processing.