ABSTRACT
Objective To investigate the effect of heroin abuse on attention switching. Methods Thirty-six Heroin abusers (33 males, 3 females) and 36 controls (32 males, 4 females) were enrolled in the study. Their cognitive function was tested by using the Switching Task, including Sustained Attention trials and Switching Attention trials. The reaction time and accuracy were recorded separately by the computer. Results The accuracy or reaction times were not signifi-cantly different between Switching Attention trial and Sustained Attention trial in heroin abusers, suggesting a lower Switch Costs value compared to the healthy controls [(19.7 ± 66.8) ms vs. (85.1 ± 92.4) ms]. The healthy controls showed faster reaction speed [Sustained Attention trial (695.3 ± 95.9) ms vs. Switching Attention trial (780.3 ± 93.3) ms, P<0.05] and higher accuracy [Sustained Attention trial (98.0%±2.2%) vs. Switching Attention trial (93.8%±5.0%), P<0.05] under the Sustained Attention trial. Compared with the healthy controls, the heroin abusers showed slower reaction speed [(791.6 ± 74.3) ms vs. (695.3±95.9) ms, P<0.05] and lower accuracy [(92.5%±8.4%) vs. (98.0%±2.2%), P<0.05] in Sus-tained Attention trial, but not in Switching Attention trial. Conclusions The present study has revealed absence of Switch Costs in heroin abusers, which may be related to the damage of heroin abusers in their Sustained Attention function.
ABSTRACT
Objective To investigate the neural mechanism of the reduction of switch cost induced by short presentation of the task cue.Methods The event-related potentials (ERP) was recorded from 19 subjects while they performed a Chinese Stroop switching task.The factorial design of repeated-measures was adopted with the cue presentation time (100/1000 ms) and the type of succeeding task (repeat/switch).Results For the switch cost of reaction time (the switch subtracts the repeat),the difference between the long cue group (15.0 ± 33.3 ms) and the short group (0.80 -±40.7 ms) had the significantly tendency( t (18) =- 1.77,P=0.09).During the stage of cue processing,the ERP effects of cue reveal in the frontal-occipital areas ( 100 ～ 200 ms),frontoparietal and tempo-occipital regions (200 ～500 ms),frontoparietal network and centro-occipital regions (500 ～900ms).During the stage of task execution,the ERP effects of the cue were observed from the left fronto-occipital areas ( 300 ～ 400 ms) to parieto-occipital areas (400 ～ 900 ms).The ERP effects of the task started from the right hemisphere (500 ～600 ms ) and extended to bilateral prefrontal and centro-parietal area (600 ～900 ms ).Conclusion The short cue presentation can not only start up the preparation of frontoparietal network earlier during cue processing stage but also enhance its retrieval in the left dorsal lateral frontal cortex during task executive stage.