A step towards non-invasive characterization of the human frontal eye fields of individual subjects
A step towards non-invasive characterization of the human frontal eye fields of individual subjects
Background: Identifying eye movement related areas in the frontal lobe has a long history, with microstimulation in monkeys producing the most clear-cut results. For humans, however, there is still no consensus about the location and the extent of the frontal eye field (FEF). There is also no simple non-invasive method for unambiguously defining the FEF in individual subjects, a prerequisite for clinical applications. Here we explore the use of magnetoencephalography (MEG) for the non-invasive identification and characterization of FEF activity in an individual subject.
Methods: We mapped human brain activity before, during and after saccades by applying tomographic analysis to MEG data. Statistical parametric maps and circular statistics produced plausible FEF loci, but no unambiguous definition for individual subjects. Here we first computed the spectral decomposition and correlation with electrooculogram (EOG) of the tomographic brain activations. For each of these two measures statistical comparisons were made between different saccades.
Results: In this paper, we first review the frontal cortex activations identified in earlier animal and human studies and place the putative human FEFs in a well-defined anatomical framework. This framework is then used as reference for describing the results of new Fourier analysis of the tomographic solutions comparing active saccade tasks and their controls. The most consistent change in the dorsal frontal cortex was at the putative left FEF, for both saccades to the left and right. The asymmetric result is consistent with the 1-way callosal traffic theory. We also showed that the new correlation analysis had its most consistent change in the contralateral putative FEF. This result was obtained for EOG latencies before saccade onset with delays of a few hundreds of milliseconds (FEF activity leading the EOG) and only for visual cues signaling the execution of a saccade in a previously defined saccade direction.
Conclusions: The FEF definition derived from microstimulation describes only one of the areas in the dorsal lateral frontal lobe that act together to plan, prepare and execute a saccade. The definition and characterization of these areas in an individual subject can be obtained from non-invasive MEG measurements.
S11-S11
Ioannides, Andreas A.
f2f17b28-63d5-411d-95e3-2c3fc1b97a4e
Fenwick, Peter B.C.
46662080-3051-4d22-9cf3-112258e6f1c4
Pitri, Elina
138199c9-d690-4de5-85e4-298d7c7dc609
Liu, Lichan
458227ad-4d3b-4987-be25-b012a834bc50
3 June 2010
Ioannides, Andreas A.
f2f17b28-63d5-411d-95e3-2c3fc1b97a4e
Fenwick, Peter B.C.
46662080-3051-4d22-9cf3-112258e6f1c4
Pitri, Elina
138199c9-d690-4de5-85e4-298d7c7dc609
Liu, Lichan
458227ad-4d3b-4987-be25-b012a834bc50
Ioannides, Andreas A., Fenwick, Peter B.C., Pitri, Elina and Liu, Lichan
(2010)
A step towards non-invasive characterization of the human frontal eye fields of individual subjects.
Nonlinear Biomedical Physics, 4, supplement Consciousness and its Measures: Joint Workshop for COST Actions NeuroMath and Consciousness, .
(doi:10.1186/1753-4631-4-S1-S11).
Abstract
Background: Identifying eye movement related areas in the frontal lobe has a long history, with microstimulation in monkeys producing the most clear-cut results. For humans, however, there is still no consensus about the location and the extent of the frontal eye field (FEF). There is also no simple non-invasive method for unambiguously defining the FEF in individual subjects, a prerequisite for clinical applications. Here we explore the use of magnetoencephalography (MEG) for the non-invasive identification and characterization of FEF activity in an individual subject.
Methods: We mapped human brain activity before, during and after saccades by applying tomographic analysis to MEG data. Statistical parametric maps and circular statistics produced plausible FEF loci, but no unambiguous definition for individual subjects. Here we first computed the spectral decomposition and correlation with electrooculogram (EOG) of the tomographic brain activations. For each of these two measures statistical comparisons were made between different saccades.
Results: In this paper, we first review the frontal cortex activations identified in earlier animal and human studies and place the putative human FEFs in a well-defined anatomical framework. This framework is then used as reference for describing the results of new Fourier analysis of the tomographic solutions comparing active saccade tasks and their controls. The most consistent change in the dorsal frontal cortex was at the putative left FEF, for both saccades to the left and right. The asymmetric result is consistent with the 1-way callosal traffic theory. We also showed that the new correlation analysis had its most consistent change in the contralateral putative FEF. This result was obtained for EOG latencies before saccade onset with delays of a few hundreds of milliseconds (FEF activity leading the EOG) and only for visual cues signaling the execution of a saccade in a previously defined saccade direction.
Conclusions: The FEF definition derived from microstimulation describes only one of the areas in the dorsal lateral frontal lobe that act together to plan, prepare and execute a saccade. The definition and characterization of these areas in an individual subject can be obtained from non-invasive MEG measurements.
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Published date: 3 June 2010
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Local EPrints ID: 162389
URI: http://eprints.soton.ac.uk/id/eprint/162389
ISSN: 1753-4631
PURE UUID: 71ea9422-3772-4db7-81fc-d8283178572d
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Date deposited: 20 Aug 2010 08:00
Last modified: 14 Mar 2024 02:02
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Author:
Andreas A. Ioannides
Author:
Peter B.C. Fenwick
Author:
Elina Pitri
Author:
Lichan Liu
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