Why the processing of repeated targets are better than that of no repetition: evidence from easy-to-difficult and difficult-to-easy switching situations

Guangheng Dong,Hongli Zhou,Qilin Lu,Yanbo Hu,Xiao Lin

doi:10.1186/1744-9081-10-4

Abstract

BackgroundPrevious studies have found that the processing of repeated targets are easier than that of non-repetition. Although several theories attempt to explain this issue, the underlying mechanism still remains uncovered. In this study, we tried to address this issue by exploring the underlying brain responses during this process.MethodsBrain activities were recorded while thirty participants performing a Stroop task (Chinese version) in the MRI scanner. Using pseudo-random strategies, we created two types of switching conditions (easy-to-difficult; difficult-to-easy) and relevant repeating conditions.ResultsThe results show that, in difficult-to-easy switching situation, higher brain activations are found in left precuneus than repeating ones (the precuneus is thought related with attention demands). In easy-to-difficult switching conditions, higher brain activations are found in precuneus, superior temporal gyrus, posterior cingulate cortex, and inferior frontal gyrus than repeating trials (most of these regions are thought related with executive function). No overlapping brain regions are observed in con_CON and incon_INCON conditions. Beta figures of the survived clusters in different conditions, correlations between brain activations and switch cost were calculated.ConclusionsThe present study suggests that the feature that response time in switching trials are longer than that in repeating trials are caused by the extra endeavors engaged in the switching processes.

Highlights

Plenty of studies have found that the current trial performance is influenced by previous one [1,2,3,4,5], and that the processing of repeated targets are better than that of non-repeated ones [6,7,8]
Response times for congruent trials following congruent trials tend to be shorter than those for congruent trials followed by incongruent trials [10,11]
Significant Stroop effect was observed when comparing incongruent trials to congruent tirals [t = 7.621, p < 0.001], which proved that the Stroop task is valid in current study

Summary

Introduction

Plenty of studies have found that the current trial performance is influenced by previous one [1,2,3,4,5], and that the processing of repeated targets are better than that of non-repeated ones [6,7,8]. Mental set switching ( termed “mental switch”, “mental shifting”) has been reported to be involved in nearly any type of cognitive switches [12,13,14]. It is required when the focus of attention must be altered in order to adapt to a frequently changing environment. When we switch from one type of task to another, extra executive endeavors should be involved to complete this process. The underlying mechanism behind this is the ability to update the executive control parameters representing a given ‘task set’ to accommodate a new task set [15,16].

Methods

Results

Conclusion