Evidence of partial response activation in a memory-search task.
Studies using the lateralized readiness potential (LRP; an index of hand-specific motor preparation), suggest that the motor system can be activated on the basis of partial information, providing support for a parallel view of the human information processing system. However, data to the contrary have been obtained in memory-search paradigms, leading Heil et al. [Psychological Research 62 (1999) 289] to propose that hand-specific motor preparation cannot occur in parallel with memory scanning. To further investigate these findings we recorded the LRP in a fast-paced memory search task, in which the case of target letter and memory set size were manipulated and a choice-go/no-go procedure was used. The case of the test letter determined the response hand, whereas membership of the test stimulus in the memory set determined whether a response was required. We found different types of LRP effects as a function of time on task. Analyses based on the data from the first half of the experiment replicated those obtained by Heil et al. [Psychological Research 62 (1999) 289]. However, unlike Heil et al. [Psychological Research 62 (1999) 289], the second half of the data showed significant LRP activity on no-go trials and similar LRP onset latencies for go and no-go trials, as well as for different memory set size conditions in the stimulus-locked LRP waveforms. The response-related waveforms showed an earlier LRP onset in the set-size 4 than in the set-size 2 condition. These data suggest that motor preparation can occur simultaneously with memory search when participants are sufficiently practiced. Time-on-task and strategy differences between the two studies are discussed.
Shin
Eunsam
E
Psychology Department, Beckman Institute, University of Illinois at Urbana-Champaign, IL 61801, USA.
Fabiani
Monica
M
Gratton
Gabriele
G
D000293:Adolescent; D000328:Adult; D003071:Cognition / Q000502:physiology; D005074:Evoked Potentials, Visual / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology