Conductivity in the somatosensory cortex of the cat — evidence for cortical anisotropy

Hoeltzell, Perry B.; Dykes, Robert W.

doi:10.1016/0006-8993(79)90918-1

Cited by 56 publications

(31 citation statements)

References 26 publications

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“…Measurements of the conductivity in cat cerebellar cortex showed that the conductivity in the direction normal to the cortical surface has a value which is approximately twice as large as the conductivity parallel to the surface (YEDLIN et al, 1974) and in the cerebral white matter this factor is nine (NICHOLSON, 1965). HOELTZELL and DIJKER, (1979) also demonstrated the existence of cortical anisotropy in the somatosensory cortex of the cat. They found that the anisotropy varied with the depth.…”

Section: Ifmbe: 1988mentioning

confidence: 84%

On the magnetic field and the electrical potential generated by bioelectric sources in an anisotropic volume conductor

Peters

Eliáš

1988

Med. Biol. Eng. Comput.

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Section: Ifmbe: 1988mentioning

confidence: 84%

On the magnetic field and the electrical potential generated by bioelectric sources in an anisotropic volume conductor

Peters

Eliáš

1988

Med. Biol. Eng. Comput.

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“…The conductivity of the grey matter, however, was inhomogeneous, with layer I having a ~6 0 % lower value than layers I I -V I . This value was estimated from empirical data by HABERLY andSHEPHERD (1973) andHOELTZELL andDYKES (1979). In both studies, a large gradient in conductivity was reported from layer I to layer II.…”

Section: Conductivitiesmentioning

confidence: 98%

Modelling motor cortex stimulation for chronic pain control: Electrical potential field, activating functions and responses of simple nerve fibre models

Manola

Roelofsen

Holsheimer

et al. 2005

Med. Biol. Eng. Comput.

111

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This computer modelling study on motor cortex stimulation (MCS) introduced a motor cortex model, developed to calculate the imposed electrical potential field characteristics and the initial response of simple fibre models to stimulation of the precentral gyrus by an epidural electrode, as applied in the treatment of chronic, intractable pain. The model consisted of two parts: a three-dimensional volume conductor based on tissue conductivities and human anatomical data, in which the stimulation-induced potential field was computed, and myelinated nerve fibre models allowing the calculation of their response to this field. A simple afferent fibre branch and three simple efferent fibres leaving the cortex at different positions in the precentral gyrus were implemented. It was shown that the thickness of the cerebrospinal fluid (CSF) layer between the dura mater and the cortex below the stimulating electrode substantially affected the distribution of the electrical potential field in the precentral gyrus and thus the threshold stimulus for motor responses and the therapeutic stimulation amplitude. When the CSF thickness was increased from 0 to 2.5 mm, the load impedance decreased by 28%, and the stimulation amplitude increased by 6.6 V for each millimetre of CSF. Owing to the large anode-cathode distance (10 mm centre-to-centre) in MCS, the cathodal fields in mono- and bipolar stimulation were almost identical. Calculation of activating functions and fibre responses showed that only nerve fibres with a directional component parallel to the electrode surface were excitable by a cathode, whereas fibres perpendicular to the electrode surface were excitable under an anode.

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“…This type of volume conductor is designated as a piecewise homogenous volume conductor. There is evidence of anisotropic properties in head tissues (Hoeltzell & Dykes 1979); however, in this paper we shall consider only the isotropic case. The static approach for living tissues, which neglect displacement and eddy currents inside the head, was also assumed (Plonsey & Heppner 1967).…”

Section: (D) Volume Conductor Modelmentioning

confidence: 99%

Fusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses

Riera

Aubert

Iwata

et al. 2005

Phil. Trans. R. Soc. B

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The elucidation of the complex machinery used by the human brain to segregate and integrate information while performing high cognitive functions is a subject of imminent future consequences. The most significant contributions to date in this field, known as cognitive neuroscience, have been achieved by using innovative neuroimaging techniques, such as electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI), which measure variations in both the time and the space of some interpretable physical magnitudes. Extraordinary maps of cerebral activation involving function-restricted brain areas, as well as graphs of the functional connectivity between them, have been obtained from EEG and fMRI data by solving some spatio-temporal inverse problems, which constitutes a top-down approach. However, in many cases, a natural bridge between these maps/graphs and the causal physiological processes is lacking, leading to some misunderstandings in their interpretation. Recent advances in the comprehension of the underlying physiological mechanisms associated with different cerebral scales have provided researchers with an excellent scenario to develop sophisticated biophysical models that permit an integration of these neuroimage modalities, which must share a common aetiology. This paper proposes a bottom-up approach, involving physiological parameters in a specific mesoscopic dynamic equations system. Further observation equations encapsulating the relationship between the mesostates and the EEG/f MRI data are obtained on the basis of the physical foundations of these techniques. A methodology for the estimation of parameters from fused EEG/fMRI data is also presented. In this context, the concepts of activation and effective connectivity are carefully revised. This new approach permits us to examine and discuss some future prospects for the integration of multimodal neuroimages.

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Conductivity in the somatosensory cortex of the cat — evidence for cortical anisotropy

Cited by 56 publications

References 26 publications

On the magnetic field and the electrical potential generated by bioelectric sources in an anisotropic volume conductor

On the magnetic field and the electrical potential generated by bioelectric sources in an anisotropic volume conductor

Modelling motor cortex stimulation for chronic pain control: Electrical potential field, activating functions and responses of simple nerve fibre models

Fusing EEG and fMRI based on a bottom-up model: inferring activation and effective connectivity in neural masses

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