Neural correlates of spatial working memory load in a delayed match-to-sample saccade task

We propose a new way to identify the neural correlates of memory load in a delayed match-to-sample saccade task with a constant perceptual load. Two conditions were compared with low and high memory loads. In the low-load condition, a rectangular shaped probe defined by its color and orientation was...

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Bibliographic Details
Published in:	NeuroImage (Orlando, Fla.) Vol. 71; pp. 84 - 91
Main Authors:	Raabe, Markus, Fischer, Volker, Bernhardt, Daniela, Greenlee, Mark W.
Format:	Journal Article
Language:	English
Published:	Amsterdam Elsevier Inc 01-05-2013 Elsevier Elsevier Limited
Subjects:	Adult Attention Biological and medical sciences Brain Brain - physiology Brain Mapping Delayed match to sample task Female fMRI Fundamental and applied biological sciences. Psychology Humans Image Interpretation, Computer-Assisted Load Magnetic Resonance Imaging Male Memory, Short-Term - physiology Multivariate pattern analysis Perceptual load Photic Stimulation Saccades - physiology Studies Vertebrates: nervous system and sense organs Visual short term memory load Visual task performance Young Adult Delayed match to sample task fMRI Multivariate pattern analysis Perceptual load Visual short term memory load Perceptualload Working memory Nuclear magnetic resonance imaging Functional imaging Spatial memory
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Summary:	We propose a new way to identify the neural correlates of memory load in a delayed match-to-sample saccade task with a constant perceptual load. Two conditions were compared with low and high memory loads. In the low-load condition, a rectangular shaped probe defined by its color and orientation was presented centrally. After a delay period, four stimuli were presented peripherally, one in each quadrant. The participants were instructed to saccade to the stimulus that matched the previously viewed sample on both color and orientation. In the high-load condition, the order of stimulus presentation was reversed: first four eccentric stimuli were presented and after a delay the central probe. In the high-load condition, the participant executed a saccade to the remembered location of the stimulus that matched the central probe in color and orientation. The behavioral results indicate that greater working memory load is associated with prolonged saccadic reaction times. A general linear model revealed regions in prefrontal cortex (left anterior insula, right superior and middle frontal gyrus, anterior medial cingulum), and bilaterally along the intraparietal sulcus extending into surrounding areas (precuneus, superior and inferior parietal lobe) that were more activated when participants had to conjointly remember the locations, colors and orientations of four objects (load-4) compared to when they only had to remember the features of a single object (load-1). Specific responses for greater working memory load are focused on regions responsible for feature binding (occipital-temporal cortex) and allocation of attention (anterior insular cortex). Multivariate pattern analysis during the retrieval period of a trial revealed voxel clusters in the ventral visual pathway and the frontal eye fields that correctly classify the target location during the retrieval period of both tasks. ► fMRI analysis of high and low visual working memory loads during a saccadic task. ► Novel approach to assess memory load unconfounded from perceptual load. ► Multivariate pattern analysis predicts subjects’ responses during retrieval period.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 ObjectType-Article-2 ObjectType-Feature-1
ISSN:	1053-8119 1095-9572
DOI:	10.1016/j.neuroimage.2013.01.002