A perception-based ERP reveals that the magnitude of delay matters for memory-guided reaching

The relationship between the implicit visuomotor control and the motor planning accuracy

It has been well established that an implicit motor response can be elicited by a target perturbation or a visual background motion during a reaching movement. Computational studies have suggested that the mechanism of this response is based on the error signal between the efference copy and the actual sensory feedback. If the implicit motor response is based on the efference copy, the motor command accuracy would affect the amount of the modulation of the motor response. Therefore, the purpose of the current study was to investigate the relationship between the implicit motor response and the motor planning accuracy. We used a memory-guided reaching task and a manual following response (MFR) which is induced by visual grating motion. Participants performed reaching movements toward a memorized-target location with a beep cue which was presented 0 or 3 s after the target disappeared (0-s delay and 3-s delay conditions). Leftward or rightward visual grating motion was applied 400 ms after the cue. In addition, an event-related potential (ERP) was recorded during the reaching task, which reflects the motor command accuracy. Our results showed that the N170 ERP amplitude in the parietal electrodes and the MFR amplitude were significantly larger for the 3-s delay condition than the 0-s delay condition. These results suggest that the motor planning accuracy affects the amount of the implicit visuomotor response. Furthermore, there was a significant within-subjects correlation between the MFR and the N170 amplitude, which could corroborate the relationship between the implicit motor response and the motor planning accuracy.

A neural marker of medical visual expertise: implications for training

Researchers have identified a component of the EEG that discriminates visual experts from novices. The marker indexes a comprehensive model of visual processing, and if it is apparent in physicians, it could be used to investigate the development and training of their visual expertise. The purpose of this study was to determine whether a neural marker of visual expertise-the enhanced N170 event-related potential-is apparent in the EEGs of physicians as they interpret diagnostic images. We conducted a controlled trial with 10 cardiologists and 9 pulmonologists. Each participant completed 520 trials of a standard visual processing task involving the rapid evaluation of EKGs and CXRs-indicating-lung-disease. Ostensibly, each participant is expert with one type of image and competent with the other. We collected behavioral data on the participants' expertise with EKGs and CXRs and electrophysiological data on the magnitude, latency, and scalp location of their N170 ERPs as they interpreted the two types of images. Cardiologists demonstrated significantly more expertise with EKGs than CXRs, and this was reflected in an increased amplitude of their N170 ERPs while reading EKGs compared to CXRs. Pulmonologists demonstrated equal expertise with both types of images, and this was reflected in equal N170 ERP amplitudes for EKGs and CXRs. The results suggest provisionally that visual expertise has a similar substrate in medical practice as it does in other domains that have been studied extensively. This provides support for applying a sophisticated body of literature to questions about training and assessment of visual expertise among physicians.