S-R compatibility effects on motor potentials associated with hand and foot movements

Two four-choice reaction time (RT) experiments used the lateralized readiness potential (LRP) and the limb selection potential (LSP) to assess the effects of spatial S-R compatibility on motor processes. Individual stimuli were presented at one corner of a square centered at fixation, and each response was made with the left or right hand or foot. In Experiment 1, the correct response was determined by stimulus location, whereas in Experiment 2 it was determined by stimulus identity. Horizontal and vertical compatibility affected both RT and response accuracy, but the LRP and LSP results suggested that compatibility had little or no direct effect on the duration of motor processes. In addition, the results suggest that the relatively new LSP measure is a useful index of motor activation processes. Its insensitivity to horizontal stimulus artifacts makes it especially useful for studying the effects of horizontal spatial compatibility.

Polarity correspondence effect between loudness and lateralized response set

Performance is better when a high pitch tone is associated with an up or right response and a low pitch tone with a down or left response compared to the opposite pairs, which is called the spatial-musical association of response codes effect. The current study examined whether polarity codes are formed in terms of the variation in loudness. In Experiments 1 and 2, in which participants performed a loudness-judgment task and a timbre-judgment task respectively, the correspondence effect was obtained between loudness and response side regardless of whether loudness was relevant to the task or not. In Experiments 3 and 4, in which the identical loudness- and timbre-judgment tasks were conducted while the auditory stimulus was presented only to the left or right ear, the correspondence effect was modulated by the ear to which the stimulus was presented, even though the effect was marginally significant in Experiment 4. The results suggest that loudness produced polarity codes that influenced response selection (Experiments 1 and 2), and additional spatial codes provided by stimulus position modulated the effect, generating the stimulus eccentricity effect (Experiments 3 and 4), which is consistent with the polarity correspondence principle.

The development of inhibitory control: an averaged and single-trial Lateralized Readiness Potential study

Inhibitory control (IC) is an important contributor to educational performance, and undergoes rapid development in childhood. Age-related changes in IC were assessed using an in-depth analysis of reaction time, the Lateralized Readiness Potential (LRP), and other event-related potential (ERP) measures to control for speed of processing. Five-year-olds, 8-year-olds and adults completed an adapted Stroop task. Both reaction time and ERP results suggest that IC does develop in this age range, over and above changes in speed of processing. The LRP identified two processes that contribute to IC. These processes develop at different rates--an early process, involving how the conflict is initially responded to is mature by age 5, while a later process, involving how the conflict is overcome is still developing after 8 years of age. We propose that these early and late processes reflect interference suppression and response inhibition, respectively. Further, a single-trial analysis of the LRP in the incongruent condition provides evidence that the LRP is consistent across trials and functionally similar in each age group. These results corroborate previous findings regarding the development of IC, and present a new and useful tool for assessing IC across development.