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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.


(A) Average hemodynamic response amplitudes of the hemodynamic responses for each condition and FEF zone uniquely connected to the CN or SC. The lateralization observed for anti-saccades of the response amplitudes with respect to saccade direction is highlighted with red circles. Error bars denote standard error. (B) Same response amplitudes for FEF zones connected to both the CN and SC and for FEF zones connected to neither SC nor CN.
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Figure 6: (A) Average hemodynamic response amplitudes of the hemodynamic responses for each condition and FEF zone uniquely connected to the CN or SC. The lateralization observed for anti-saccades of the response amplitudes with respect to saccade direction is highlighted with red circles. Error bars denote standard error. (B) Same response amplitudes for FEF zones connected to both the CN and SC and for FEF zones connected to neither SC nor CN.

Mentions: For statistical analysis the response amplitude for each PSTH was estimated using a model of the standard HRF from SPM5 (two superimposed gamma functions). These estimated response amplitudes represent the signal change for each condition and projection zone. See Figure 6 for an overview. Response amplitudes for the various conditions were then tested statistically. First a 2 × 2 × 4 within-subjects ANOVA was performed for FEF zones uniquely connected to the SC or the CN (data in Figure 6A), missing values had to be estimated for five subjects for whom no DTI connection could be established for at most one out of four FEF zones, see Section ‘Data Analysis: Data Imputation’ for details. In Table 2 the individual response amplitudes are given for these projection zones and all four conditions. Imputed values are depicted in bold.


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)

(A) Average hemodynamic response amplitudes of the hemodynamic responses for each condition and FEF zone uniquely connected to the CN or SC. The lateralization observed for anti-saccades of the response amplitudes with respect to saccade direction is highlighted with red circles. Error bars denote standard error. (B) Same response amplitudes for FEF zones connected to both the CN and SC and for FEF zones connected to neither SC nor CN.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 6: (A) Average hemodynamic response amplitudes of the hemodynamic responses for each condition and FEF zone uniquely connected to the CN or SC. The lateralization observed for anti-saccades of the response amplitudes with respect to saccade direction is highlighted with red circles. Error bars denote standard error. (B) Same response amplitudes for FEF zones connected to both the CN and SC and for FEF zones connected to neither SC nor CN.
Mentions: For statistical analysis the response amplitude for each PSTH was estimated using a model of the standard HRF from SPM5 (two superimposed gamma functions). These estimated response amplitudes represent the signal change for each condition and projection zone. See Figure 6 for an overview. Response amplitudes for the various conditions were then tested statistically. First a 2 × 2 × 4 within-subjects ANOVA was performed for FEF zones uniquely connected to the SC or the CN (data in Figure 6A), missing values had to be estimated for five subjects for whom no DTI connection could be established for at most one out of four FEF zones, see Section ‘Data Analysis: Data Imputation’ for details. In Table 2 the individual response amplitudes are given for these projection zones and all four conditions. Imputed values are depicted in bold.

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.