Neural Contributions To Gradual Change Of Awareness States In Implicit Sequence Learning

Awareness of implicit knowledge is a changing process consisting of both conscious and unconscious components,which may be reflected in brain activation changes.Previous studies examined brain activation patterns corresponding to the start and end stages of implicit learning,but not the whole process of implicit learning.Thus,the gradual changing course of awareness in implicit learning could not be elucidated.The present study explored brain activation changes corresponding to different awareness status elicited by different stimulus onset asynchrony(SOA),over the whole course of implicit learning,by using a process dissociation procedure(PDP)paradigm and functional magnetic resonance imaging(fMRI).It was found that the 850 ms SOA elicited primarily automatic processing,while the 1350 ms SOA controlled processing.In the 850 ms SOA condition,awareness changes were mediated by the development of learning,as reflected in enhanced frontal lobe activation.In the 1350 ms SOA condition,increased controlled processing was found during the middle stage of implicit learning,while both increased controlled processing and decreased automatic processing were found in the later stage of implicit learning.Both patterns were mediated by functioning of inferior parietal lobule.These findings are consistent with representation quality theory.Moreover,four different activation patterns(i.e.,increase followed by stabilization in activation over time,continued increase in activation over time,decrease followed by stabilization in activation over time,and continued decrease in activation over time)were found in various brain regions,suggesting the variety and complexity of implicit learning processes.The results of function network show that,in the 850 ms SOA condition,the change of early learning was associated with decreased connectivity between the putamen and anterior cingulate gyrus.At the same time,the connectivity between the anterior cingulate gyrus and thalamus was decreased;the change of late learning was associated with increased connectivity between the putamen and frontal lobe.In the 1350 ms SOA condition,the change of early learning was associated with decreased connectivity between the anterior cingulate gyrus and frontal lobe;the connectivity between the anterior cingulate gyrus and cerebellar was decreased in the change of late learning,it also happened between the putamen、temporal gyrus and cerebellar,indicating the diversity and complexity of implicit learning was associated with changes in network activity,spatial extent,and connectivity.