Limits...
The human frontal oculomotor cortical areas contribute asymmetrically to motor planning in a gap saccade task.

van Donkelaar P, Lin Y, Hewlett D - PLoS ONE (2009)

Bottom Line: The results showed that the incidence of multiple saccades was increased for ispiversive but not contraversive directions for the right and left FEF, the left SEF, but not for the right SEF.A control condition in which the dorsal motor cortex was stimulated demonstrated that this was not due to any non-specific effects of the TMS influencing the spatial distribution of attention.Taken together, the results are consistent with a direction-dependent role of the FEF and left SEF in delaying the release of saccadic eye movements until they have been fully planned.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Physiology and Institute of Neuroscience, University of Oregon, Eugene, Oregon, United States of America. paulvd@uoregon.edu

ABSTRACT

Background: Saccadic eye movements are used to rapidly align the fovea with the image of objects of interest in peripheral vision. We have recently shown that in children there is a high preponderance of quick latency but poorly planned saccades that consistently fall short of the target goal. The characteristics of these multiple saccades are consistent with a lack of proper inhibitory control of cortical oculomotor areas on the brainstem saccade generation circuitry.

Methodology/principal findings: In the present paper, we directly tested this assumption by using single pulse transcranial magnetic stimulation (TMS) to transiently disrupt neuronal activity in the frontal eye fields (FEF) and supplementary eye fields (SEF) in adults performing a gap saccade task. The results showed that the incidence of multiple saccades was increased for ispiversive but not contraversive directions for the right and left FEF, the left SEF, but not for the right SEF. Moreover, this disruption was most substantial during the approximately 50 ms period around the appearance of the peripheral target. A control condition in which the dorsal motor cortex was stimulated demonstrated that this was not due to any non-specific effects of the TMS influencing the spatial distribution of attention.

Conclusions/significance: Taken together, the results are consistent with a direction-dependent role of the FEF and left SEF in delaying the release of saccadic eye movements until they have been fully planned.

Show MeSH
TMS leads to significant increases in multiple saccade frequency ipsilateral to the stimulation site.Percentage change in multiple saccade frequency plotted as a function of TMS delivery time for the left FEF (A), right FEF (B), left SEF (C), and right SEF (D). Solid symbols represent saccades made ipsiversive to the side of stimulation; open symbols, contraversive saccades. Shaded region centered on 0 represents the intersubject variability in multiple saccade frequency during the non-TMS trials. This varies across the 4 conditions because each was performed in a separate session. Asterisks, significant difference between ipsiversive and contraversive multiple saccade frequency.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2749336&req=5

pone-0007278-g004: TMS leads to significant increases in multiple saccade frequency ipsilateral to the stimulation site.Percentage change in multiple saccade frequency plotted as a function of TMS delivery time for the left FEF (A), right FEF (B), left SEF (C), and right SEF (D). Solid symbols represent saccades made ipsiversive to the side of stimulation; open symbols, contraversive saccades. Shaded region centered on 0 represents the intersubject variability in multiple saccade frequency during the non-TMS trials. This varies across the 4 conditions because each was performed in a separate session. Asterisks, significant difference between ipsiversive and contraversive multiple saccade frequency.

Mentions: The tendency for more multiple saccades to be generated ipsiversive to the site of stimulation is captured in Figure 4 which displays the percentage change in the frequency of multiple saccades as a function of the time at which TMS is delivered. For the FEF (Fig. 4A,B) there is a clear increase in multiple saccade frequency for saccades directed ipsiversively, but not contraversively when TMS is delivered to either the left (main effect of saccade direction: F[1,139] = 4.19, p = 0.018) or right (main effect of saccade direction: F[1,139] = 2.41, p = 0.0342) hemisphere. Post-hoc tests demonstrated that this effect was driven by differences across ipsi- versus contraversive saccades when TMS was delivered coincident with peripheral target appearance or 50 ms later in the left FEF (p<0.05), or coincident with peripheral target appearance or 50 ms earlier in the right FEF (p<0.05). This trend was partially replicated in the SEF (Fig. 4C,D). In particular, there was a significant effect of saccade direction when TMS was delivered to the left SEF (F[1,139] = 2.95, p = 0.0396), but not when it was delivered to the right SEF (F[1,139] = 0.55, p = 0.261). Again, post-hoc tests revealed that this was due to differences between ipsi- versus contraversive saccades when TMS was delivered over the left SEF coincident with the appearance of the peripheral target or 50 ms later (p<0.05). Finally, stimulation at the dorsal motor cortex control site did not lead to any change in the incidence of multiple saccades across ipsiversive and contraversive directions (F[1,49] = 0.55, p = 0.261). Thus, taken together, these data demonstrate that whereas the reaction times of multiple saccades remained invariant across the different combinations of trial types; the frequency with which they occurred was systematically influenced by both TMS delay and saccade direction.


The human frontal oculomotor cortical areas contribute asymmetrically to motor planning in a gap saccade task.

van Donkelaar P, Lin Y, Hewlett D - PLoS ONE (2009)

TMS leads to significant increases in multiple saccade frequency ipsilateral to the stimulation site.Percentage change in multiple saccade frequency plotted as a function of TMS delivery time for the left FEF (A), right FEF (B), left SEF (C), and right SEF (D). Solid symbols represent saccades made ipsiversive to the side of stimulation; open symbols, contraversive saccades. Shaded region centered on 0 represents the intersubject variability in multiple saccade frequency during the non-TMS trials. This varies across the 4 conditions because each was performed in a separate session. Asterisks, significant difference between ipsiversive and contraversive multiple saccade frequency.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2749336&req=5

pone-0007278-g004: TMS leads to significant increases in multiple saccade frequency ipsilateral to the stimulation site.Percentage change in multiple saccade frequency plotted as a function of TMS delivery time for the left FEF (A), right FEF (B), left SEF (C), and right SEF (D). Solid symbols represent saccades made ipsiversive to the side of stimulation; open symbols, contraversive saccades. Shaded region centered on 0 represents the intersubject variability in multiple saccade frequency during the non-TMS trials. This varies across the 4 conditions because each was performed in a separate session. Asterisks, significant difference between ipsiversive and contraversive multiple saccade frequency.
Mentions: The tendency for more multiple saccades to be generated ipsiversive to the site of stimulation is captured in Figure 4 which displays the percentage change in the frequency of multiple saccades as a function of the time at which TMS is delivered. For the FEF (Fig. 4A,B) there is a clear increase in multiple saccade frequency for saccades directed ipsiversively, but not contraversively when TMS is delivered to either the left (main effect of saccade direction: F[1,139] = 4.19, p = 0.018) or right (main effect of saccade direction: F[1,139] = 2.41, p = 0.0342) hemisphere. Post-hoc tests demonstrated that this effect was driven by differences across ipsi- versus contraversive saccades when TMS was delivered coincident with peripheral target appearance or 50 ms later in the left FEF (p<0.05), or coincident with peripheral target appearance or 50 ms earlier in the right FEF (p<0.05). This trend was partially replicated in the SEF (Fig. 4C,D). In particular, there was a significant effect of saccade direction when TMS was delivered to the left SEF (F[1,139] = 2.95, p = 0.0396), but not when it was delivered to the right SEF (F[1,139] = 0.55, p = 0.261). Again, post-hoc tests revealed that this was due to differences between ipsi- versus contraversive saccades when TMS was delivered over the left SEF coincident with the appearance of the peripheral target or 50 ms later (p<0.05). Finally, stimulation at the dorsal motor cortex control site did not lead to any change in the incidence of multiple saccades across ipsiversive and contraversive directions (F[1,49] = 0.55, p = 0.261). Thus, taken together, these data demonstrate that whereas the reaction times of multiple saccades remained invariant across the different combinations of trial types; the frequency with which they occurred was systematically influenced by both TMS delay and saccade direction.

Bottom Line: The results showed that the incidence of multiple saccades was increased for ispiversive but not contraversive directions for the right and left FEF, the left SEF, but not for the right SEF.A control condition in which the dorsal motor cortex was stimulated demonstrated that this was not due to any non-specific effects of the TMS influencing the spatial distribution of attention.Taken together, the results are consistent with a direction-dependent role of the FEF and left SEF in delaying the release of saccadic eye movements until they have been fully planned.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Physiology and Institute of Neuroscience, University of Oregon, Eugene, Oregon, United States of America. paulvd@uoregon.edu

ABSTRACT

Background: Saccadic eye movements are used to rapidly align the fovea with the image of objects of interest in peripheral vision. We have recently shown that in children there is a high preponderance of quick latency but poorly planned saccades that consistently fall short of the target goal. The characteristics of these multiple saccades are consistent with a lack of proper inhibitory control of cortical oculomotor areas on the brainstem saccade generation circuitry.

Methodology/principal findings: In the present paper, we directly tested this assumption by using single pulse transcranial magnetic stimulation (TMS) to transiently disrupt neuronal activity in the frontal eye fields (FEF) and supplementary eye fields (SEF) in adults performing a gap saccade task. The results showed that the incidence of multiple saccades was increased for ispiversive but not contraversive directions for the right and left FEF, the left SEF, but not for the right SEF. Moreover, this disruption was most substantial during the approximately 50 ms period around the appearance of the peripheral target. A control condition in which the dorsal motor cortex was stimulated demonstrated that this was not due to any non-specific effects of the TMS influencing the spatial distribution of attention.

Conclusions/significance: Taken together, the results are consistent with a direction-dependent role of the FEF and left SEF in delaying the release of saccadic eye movements until they have been fully planned.

Show MeSH