内隐觉察的行为和神经活动特征

The Behavioral and Neural Active Features of Implicit Detection

变化盲视是指在某些条件下人们往往觉察不到视觉场景中实质性的改变。最近研究表明,变化盲视发生时个体虽然不能有意识地报告变化,但却能无意识地对变化刺激进行加工和反应,也就是产生了内隐觉察。内隐觉察能够引导注意、影响反应速度。与觉察和无觉察相比,内隐觉察的眼动模式具有鲜明的特征。与无变化试次相比,内隐觉察试次可以观察到显著的脑电活动变化以及不同的脑区激活。内隐觉察的研究虽然取得了丰富的成果,但也还存在着几个需要进一步探讨和解决的问题,如左侧前额叶在内隐觉察中的作用,以及如何将没有视觉干扰的范式应用到神经活动的测量中等。

Change blindness is the striking failure to see large changes that normally would be noticed easily.It may be a general consequence of selective visual attention relevant to multiple species and stimulus dimensions.In contrast,change detection is the successful awareness of the change.The term of change detection pertains primarily to the visual processes involved in first noticing a change.It denotes not only proper detection(i.e.,the observer reporting on the existence of the change),but also identification(reporting what the change is)and localization(reporting where it is).Recent studies have shown that while change blindness occurs,observers cannot consciously report changes,instead they can unconsciously process and respond to changing stimulus.This phenomenon is called implicit detection.When an implicit detection occurs,the observer's response time,eye movement pattern,event-related potentials and activation brain area are significantly different from those where the scene has no change.Change blindness cannot be interpreted as resulting from impoverished or volatile visual representations or as a failure to process the pre-change and post-change object.Instead,change detection appears in explicit change detection is not sensitive to the presence of that information.Implicit detection affects the speed of response,which is typically manifested in Simon effect and Sperling-type tasks.Some experimental evidence from gaze-tracking and forced-choice tasks has pointed towards the possibility that some implicit bottom-up processes may guide visual perception even during change blindness.Participants could correctly guess the change location above chance level even though they claimed that could not notice the change.Comparing eye metrics of detection,non-detection and possible implicit detection,results indicated that eye metrics of fixation count,fixation duration,mean saccade length,and backtrack rate can predict detections and non-detections.Additionally,gaze plots of possible implicit detection reveal signature that distinguishes eye movement search patterns.Differential brain activity for changes during change blindness compared to no change condition can be observed.Brain registers visual changes very rapidly,less than 100ms after the change onset,even when the subjects are not aware of these changes.Comparing the ERPs which participants are subjectively unaware of the change and localize it correctly versus incorrectly.At the early latencies of 30-80ms after change onset,different responses can be observed.The P3 component is strictly contained in the parietal electrodes for implicit detection.Change blindness does not preclude the encoding of the pre-change and post-change objects’identities and the comparison of their semantic content.There is a semantic mismatch ERP effect,that is,a more negative-going ERP resembling the N400 effect,albeit at longer latencies.Theta activity in the right superior temporal gyrus(rSTG)is noted in undetected visual change responses relative to the absence of change.Transcranial magnetic stimulation(TMS)induced disruption over this area directly increases rates of change blindness.Some studies show anterior prefrontal involvement in implicit detection processes.Neuroimaging and neurostimulation evidence that the dorsolateral and anterior prefrontal cortex can operate on non-conscious information in a manner that goes beyond automatic forms of sensorimotor priming which may support implicit detection.Based on the review of past studies,we propose that 3 problems should be explored in future work.First,in what form(visual or verbal)such representations that support implicit detection are stored in the brain,how long it is held,and whether it is at a single feature level or an integrated feature level.Second,whether the activation of the prefrontal lobe is related to cognitive control during implicit detection.Third,how to apply the change blindness paradigm without visual disturbance such as a gradual change method to the measurement of neural activity.