Research report Processing of bilateral versus unilateral conditions: Evidence for the functional contribution of the ventral attention network Lena-Alexandra Beume a,b,c,* , Christoph P. Kaller a,b,c , Markus Hoeren a,b,c , Stefan Kl € oppel a,b,c,d , Dorothee Kuemmerer a,b , Volkmar Glauche a,b , Lena K € ostering a,b,c,f , Irina Mader a,e , Michel Rijntjes a,b , Cornelius Weiller a,b,c and Roza Umarova a,b,c a Department of Neurology and Neuroscience, University Medical Centre Freiburg, Germany b Freiburg Brain Imaging Centre, University Medical Centre Freiburg, Germany c BrainLinks-BrainTools Cluster of Excellence, University Medical Centre Freiburg, Germany d Department of Psychiatry and Psychotherapy, University Medical Centre Freiburg, Germany e Department of Neuroradiology, and University Medical Centre Freiburg, Germany f Biological and Personality Psychology, Dept. of Psychology, University Medical Centre Freiburg, Germany article info Article history: Received 13 October 2014 Reviewed 27 January 2015 Revised 24 February 2015 Accepted 25 February 2015 Action editor Norihiro Sadato Published online 6 March 2015 Keywords: Bilateral visual processing Multi-target perception Visual extinction Visual neglect Normal aging abstract Processing of multiple or bilateral conditions presented simultaneously in both hemifields reflects the natural mode of perception in our multi-target environment, but is not yet completely understood. While region-of-interest based studies in healthy subjects reported single cortical areas as the right inferior parietal lobe (IPL) or temporoparietal junction (TPJ) to process bilateral conditions, studies in extinction patients with reduced ability in this regard suggested the right superior temporal cortex to hold a key role. The present fMRI study on healthy subjects aimed at resolving these discrepancies by contrasting bilateral versus unilateral visual conditions in a paradigm similar to the bed-side test for patients with visual extinction on a whole brain level. Additionally, reduced attentional capacity in spatial processing was investigated in normal aging. Processing of bilateral conditions compared to unilateral ones showed to require stronger activation of not one single cortical region but the entire right-lateralized ventral attention network, bilateral parietal and vi- sual association areas. These results might suggest a conceptual difference between uni- lateral and bilateral spatial processing with the latter depending on additional anatomical and functional brain resources. Reduced attentional capacity in elderly subjects was associated with compensatory recruitment of contralateral functional homologues [left IPL, TPJ, frontal eye field (FEF)]. These data reveal the functional anatomy of our ability to * Corresponding author. University Medical Centre Freiburg, Department of Neurology and Neuroscience, Breisacherstrasse 64, 79106 Freiburg, Germany. E-mail address: lena.beume@uniklinik-freiburg.de (L.-A. Beume). Available online at www.sciencedirect.com ScienceDirect Journal homepage: www.elsevier.com/locate/cortex cortex 66 (2015) 91 e102 http://dx.doi.org/10.1016/j.cortex.2015.02.018 0010-9452/© 2015 Elsevier Ltd. All rights reserved.