title: The relationship between working memory storage and elevated activity as measured with functional magnetic resonance imaging.
abstract: Does the sustained, elevated neural activity observed during working memory tasks reflect the short-term retention of information? Functional magnetic resonance imaging (fMRI) data of delayed recognition of visual motion in human participants were analyzed with two methods: a general linear model (GLM) and multivoxel pattern analysis. Although the GLM identified sustained, elevated delay-period activity in superior and lateral frontal cortex and in intraparietal sulcus, pattern classifiers were unable to recover trial-specific stimulus information from these delay-active regions. The converse-no sustained, elevated delay-period activity but successful classification of trial-specific stimulus information-was true of posterior visual regions, including area MT+ (which contains both middle temporal area and medial superior temporal area) and calcarine and pericalcarine cortex. In contrast to stimulus information, pattern classifiers were able to extract trial-specific task instruction-related information from frontal and parietal areas showing elevated delay-period activity. Thus, the elevated delay-period activity that is measured with fMRI may reflect processes other than the storage, per se, of trial-specific stimulus information. It may be that the short-term storage of stimulus information is represented in patterns of (statistically) "subthreshold" activity distributed across regions of low-level sensory cortex that univariate methods cannot detect.
authors.affiliation: Department of Psychology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. riggall@wisc.edu
authors.forename: Adam C
authors.initials: AC
authors.lastname: Riggall
authors.forename: Bradley R
authors.initials: BR
authors.lastname: Postle
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000098:blood supply* / Q000502:physiology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D009039:Motion Perception / Q000502:physiology*; D010100:Oxygen; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult
chemical_list: D010100:Oxygen