Human fronto-tectal and fronto-striatal-tectal pathways activate differently during anti-saccades
- Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, Netherlands
Almost all cortical areas in the vertebrate brain take part in recurrent connections through the subcortical basal ganglia (BG) nuclei, through parallel inhibitory and excitatory loops. It has been suggested that these circuits can modulate our reactions to external events such that appropriate reactions are chosen from many available options, thereby imposing volitional control over behavior. The saccade system is an excellent model system to study cortico-BG interactions. In this study two possible pathways were investigated that might regulate automaticity of eye movements in the human brain; the cortico-tectal pathway, running directly between the frontal eye fields (FEF) and superior colliculus (SC) and the cortico-striatal pathway from the FEF to the SC involving the caudate nucleus (CN) in the BG. In an event-related functional magnetic resonance imaging (fMRI) paradigm participants made pro- and anti-saccades. A diffusion tensor imaging (DTI) scan was made for reconstruction of white matter tracts between the FEF, CN and SC. DTI fiber tracts were used to divide both the left and right FEF into two sub-areas, projecting to either ipsilateral SC or CN. For each of these FEF zones an event-related fMRI timecourse was extracted. In general activity in the FEF was larger for anti-saccades. This increase in activity was lateralized with respect to anti-saccade direction in FEF zones connected to the SC but not for zones only connected to the CN. These findings suggest that activity along the contralateral FEF–SC projection is responsible for directly generating anti-saccades, whereas the pathway through the BG might merely have a gating function withholding or allowing a pro-saccade.
Keywords:
frontal eye fields, superior colliculus, caudate nucleus, anti-saccades, DTI, fMRI
Citation:
de Weijer AD, Mandl RCW, Sommer IEC, Vink M, Kahn RS and Neggers SFW (2010) Human fronto-tectal and fronto-striatal-tectal pathways activate differently during anti-saccades. Front. Hum. Neurosci. 4:41. doi: 10.3389/fnhum.2010.00041
Received: 10 November 2009;
Paper pending published: 24 February 2010;
Accepted: 22 April 2010;
Published online: 26 May 2010
Edited by:
Chris Rorden, University of South Carolina, USA
Reviewed by:
Tony Ro, City College of New York, USA
Paul Corballis, Georgia Institute of Technology, USA
Copyright:
© 2010 de Weijer, Mandl, Sommer, Vink, Kahn and Neggers. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.
*Correspondence:
Sebastiaan F. W. Neggers, Department of Psychiatry, Rudolf Magnus Institute for Neuroscience, University Medical Center Utrecht, Heidelberglaan 100, Room B.01.103, 3584 CX Utrecht, Netherlands. e-mail: b.neggers@umcutrecht.nl