Human area MT+ shows load-dependent activation during working memory maintenance with continuously morphing stimulation.

Daniela Galashan,Andreas K Kreiter,Thorsten Fehr,Manfred Herrmann

doi:10.1186/1471-2202-15-85

Daniela Galashan, Andreas K Kreiter + Show 2 more

Open Access

https://doi.org/10.1186/1471-2202-15-85

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Abstract

BackgroundInitially, human area MT+ was considered a visual area solely processing motion information but further research has shown that it is also involved in various different cognitive operations, such as working memory tasks requiring motion-related information to be maintained or cognitive tasks with implied or expected motion.In the present fMRI study in humans, we focused on MT+ modulation during working memory maintenance using a dynamic shape-tracking working memory task with no motion-related working memory content. Working memory load was systematically varied using complex and simple stimulus material and parametrically increasing retention periods. Activation patterns for the difference between retention of complex and simple memorized stimuli were examined in order to preclude that the reported effects are caused by differences in retrieval.ResultsConjunction analysis over all delay durations for the maintenance of complex versus simple stimuli demonstrated a wide-spread activation pattern. Percent signal change (PSC) in area MT+ revealed a pattern with higher values for the maintenance of complex shapes compared to the retention of a simple circle and with higher values for increasing delay durations.ConclusionsThe present data extend previous knowledge by demonstrating that visual area MT+ presents a brain activity pattern usually found in brain regions that are actively involved in working memory maintenance.

Highlights

Human area MT+ was considered a visual area solely processing motion information but further research has shown that it is involved in various different cognitive operations, such as working memory tasks requiring motion-related information to be maintained or cognitive tasks with implied or expected motion
Memory for motion direction was associated with increased neuronal activity in MT during retention [10] and human MT+ was shown to demonstrate a signal increase in functional magnetic resonance imaging when motion information had to be held in working memory (WM) [11]
We explored whether manipulations in complexity and delay length modulate brain activity in area MT+ during WM maintenance, and whether area MT+ is engaged in the processing of stimuli with motion information that does not need to be maintained in WM

Summary

Introduction

Human area MT+ was considered a visual area solely processing motion information but further research has shown that it is involved in various different cognitive operations, such as working memory tasks requiring motion-related information to be maintained or cognitive tasks with implied or expected motion. Memory for motion direction was associated with increased neuronal activity in MT during retention [10] and human MT+ was shown to demonstrate a signal increase in functional magnetic resonance imaging (fMRI) when motion information had to be held in working memory (WM) [11]. These memory studies investigated motion-related memory contents. We investigated whether area MT+ is engaged during WM maintenance when no motionrelated WM content is used, but motion information has to be processed

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