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Human fronto-tectal and fronto-striatal-tectal pathways activate differently during anti-saccades.

de Weijer AD, Mandl RC, Sommer IE, Vink M, Kahn RS, Neggers SF - Front Hum Neurosci (2010)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht Utrecht, Netherlands.

ABSTRACT
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.

No MeSH data available.


FEF activation t-map for the ‘localizer’ task in four individual participants at threshold t > 3, overlaid on their T1-weighted structural scan, in a coronal (upper panels) and axial (lower panels) view. Only the clusters of activated voxels are shown that overlap with known locations of the FEF. The data is shown in MNI atlas space and has been normalized from native space only for visualization purposes in this figure. The color codes denote T-values for the contrast saccade-block vs rest. For every slice the y and z MNI coordinate of the cross-section are given in millimeter.
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Figure 2: FEF activation t-map for the ‘localizer’ task in four individual participants at threshold t > 3, overlaid on their T1-weighted structural scan, in a coronal (upper panels) and axial (lower panels) view. Only the clusters of activated voxels are shown that overlap with known locations of the FEF. The data is shown in MNI atlas space and has been normalized from native space only for visualization purposes in this figure. The color codes denote T-values for the contrast saccade-block vs rest. For every slice the y and z MNI coordinate of the cross-section are given in millimeter.

Mentions: The individual FEF could be properly localized using the fast pro- anti-saccade ‘localizer’ task. Besides the FEF, parietal and occipital cortices were also activated. The non-FEF clusters were removed from the maps to create FEF masks (see Materials and Methods). One participant showed no evident activation in the FEF and was excluded from further analysis. See Figure 2 for the individual activation maps of four participants. Note the considerable variability in shape, location and size of activated regions over subjects (see also Neggers et al., 2007; Van Ettinger-Veenstra et al., 2009). From these activation maps, the right and left FEF masks were created by assessing the proximity of connected clusters of voxels to known FEF coordinates (Nielsen and Hansen, 2002) (see Materials and Methods).


Human fronto-tectal and fronto-striatal-tectal pathways activate differently during anti-saccades.

de Weijer AD, Mandl RC, Sommer IE, Vink M, Kahn RS, Neggers SF - Front Hum Neurosci (2010)

FEF activation t-map for the ‘localizer’ task in four individual participants at threshold t > 3, overlaid on their T1-weighted structural scan, in a coronal (upper panels) and axial (lower panels) view. Only the clusters of activated voxels are shown that overlap with known locations of the FEF. The data is shown in MNI atlas space and has been normalized from native space only for visualization purposes in this figure. The color codes denote T-values for the contrast saccade-block vs rest. For every slice the y and z MNI coordinate of the cross-section are given in millimeter.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2903195&req=5

Figure 2: FEF activation t-map for the ‘localizer’ task in four individual participants at threshold t > 3, overlaid on their T1-weighted structural scan, in a coronal (upper panels) and axial (lower panels) view. Only the clusters of activated voxels are shown that overlap with known locations of the FEF. The data is shown in MNI atlas space and has been normalized from native space only for visualization purposes in this figure. The color codes denote T-values for the contrast saccade-block vs rest. For every slice the y and z MNI coordinate of the cross-section are given in millimeter.
Mentions: The individual FEF could be properly localized using the fast pro- anti-saccade ‘localizer’ task. Besides the FEF, parietal and occipital cortices were also activated. The non-FEF clusters were removed from the maps to create FEF masks (see Materials and Methods). One participant showed no evident activation in the FEF and was excluded from further analysis. See Figure 2 for the individual activation maps of four participants. Note the considerable variability in shape, location and size of activated regions over subjects (see also Neggers et al., 2007; Van Ettinger-Veenstra et al., 2009). From these activation maps, the right and left FEF masks were created by assessing the proximity of connected clusters of voxels to known FEF coordinates (Nielsen and Hansen, 2002) (see Materials and Methods).

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht Utrecht, Netherlands.

ABSTRACT
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.

No MeSH data available.