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Ferdinando Sartucci - One of the best experts on this subject based on the ideXlab platform.

  • platform session nibs altered recovery from inhibitory repetitive transcranial magnetic stimulation rtms in subjects with Photosensitive Epilepsy
    Clinical Neurophysiology, 2018
    Co-Authors: T Occi, Matteo Caleo, Laura Restani, Simone Rossi, Anna De Rosa, Ferdinando Sartucci
    Abstract:

    Introduction Only few studies have explored the pathophysiology of PSE; some Authors have suggested a defective visual inhibition as a contributing factor to photoparoxysmal response, pointing to an overactive visuomotor connectivity thus inducing abnormal motor responses. In order to investigate functional changes underlying photosensitivity, we studied the response of the visual cortex to low-frequency, inhibitory repetitive transcranial magnetic stimulation (rTMS) in drug-free patients with Photosensitive seizures and healthy volunteers. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different luminance contrasts (K20%, K50% and K90%) were recorded in both hemispheres before and after transient functional inactivation of the occipital cortex of one side via low-frequency rTMS (0.5 Hz, at 120 % of resting motor threshold, for 20’). VEPs were recorded before (T0), immediately after (T1) and 45’ following the completion of rTMS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Results Baseline amplitudes of the VEP components (N1 and P1) were enhanced in Photosensitive patients. At T1, rTMS produced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a concurrent facilitation of responses in the contralateral hemisphere. Compared with PSE subjects, VEP amplitudes remained persistently dampened in the stimulated hemisphere of controls (Holm–Sidak post hoc method, p  Conclusion The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity may play a role in the pathophysiology of Photosensitive Epilepsy. Beyond the stereotyped dichotomy between generalized and focal epilepsies, our data seem to indicate PSE as a “system disease”.

  • altered recovery from inhibitory repetitive transcranial magnetic stimulation rtms in subjects with Photosensitive Epilepsy
    Clinical Neurophysiology, 2016
    Co-Authors: Tommaso Bocci, Matteo Caleo, Laura Restani, Simone Rossi, D Barloscio, Ferdinando Sartucci
    Abstract:

    Objective To investigate functional changes underlying photosensitivity, we studied the response of the visual cortex to low-frequency, inhibitory repetitive transcranial magnetic stimulation (rTMS) in patients with Photosensitive seizures and healthy volunteers. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts were recorded in both hemispheres before and after inactivation of the occipital cortex of one side via low-frequency rTMS (0.5 Hz, 120 % RMT, 20′). VEPs were recorded before (T0), immediately after (T1) and 45′ following rTMS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Results Baseline amplitudes of the VEP components (N1 and P1) were enhanced in Photosensitive patients. At T1, rTMS produced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a concurrent facilitation of responses in the contralateral hemisphere. Compared with PSE subjects, VEP amplitudes remained persistently dampened in the stimulated hemisphere of controls (Holm-Sidak post hoc method, p p Conclusions The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity may play a role in the pathophysiology of Photosensitive Epilepsy. Significance beyond the stereotyped dichotomy between generalized and focal epilepsies, both sets of data seem to indicate PSE as a “system disease”.

  • 109 Photosensitive Epilepsy role of corpus callosum in cortical excitability
    Clinical Neurophysiology, 2015
    Co-Authors: Ferdinando Sartucci, Tommaso Bocci, A Torzini, Matteo Caleo, Elisa Giorli, Laura Restani, Simone Rossi, Lamberto Maffei
    Abstract:

    Photosensitive Epilepsy (PE) is a form of epileptic seizure induced by several powerful visual stimuli. Cortical mechanisms underlying paroxysmal activity have been widely studied in several ways. Here, we employed rTMS in an attempt to disclose the role of callosal input in modulating cortical visual excitability in both healthy subjects and PE patients. We enrolled 10 healthy subjects (5 males and 5 females; mean age 16.8 ± 3.4 yrs) and 5 patients (15.9 ± 4.2 yrs). Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts were recorded before and after functional inactivation of the occipital cortex of one hemisphere via off-line low-frequency repetitive transcranial magnetic stimulation (rTMS; 0.5 Hz stimulation for 20 min). VEPs were recorded in V1 before (T0), immediately after (T1) and 45′ following the end of rTMS (T2). We found that low-frequency rTMS had an inhibitory effect on VEP amplitudes at all contrasts in the treated side in controls and patients. Reduction of VEP amplitudes in the inhibited hemisphere at T1 was accompanied by an increase in VEP amplitudes in the contralateral side at mid-high contrasts (50–90%) in healthy subjects ( p p p

Joydeep Bhattacharya - One of the best experts on this subject based on the ideXlab platform.

  • frequency and phase synchronization in neuromagnetic cortical responses to flickering color stimuli
    Laser Physics, 2010
    Co-Authors: Serge F Timashev, R M Yulmetyev, S A Demin, Yu O Panischev, Shinsuke Shimojo, Joydeep Bhattacharya, Yuriy S Polyakov
    Abstract:

    In our earlier study dealing with the analysis of neuromagnetic responses (magnetoencephalograms—MEG) to flickering-color stimuli for a group of control human subjects (9 volunteers) and a patient with Photosensitive Epilepsy (a 12-year old girl), it was shown that Flicker-Noise Spectroscopy (FNS) was able to identify specific differences in the responses of each organism. The high specificity of individual MEG responses manifested itself in the values of FNS parameters for both chaotic and resonant components of the original signal. The present study applies the FNS cross-correlation function to the analysis of correlations between the MEG responses simultaneously measured at spatially separated points of the human cortex processing the red-blue flickering color stimulus. It is shown that the cross-correlations for control (healthy) subjects are characterized by frequency and phase synchronization at different points of the cortex, with the dynamics of neuromagnetic responses being determined by the low-frequency processes that correspond to normal physiological rhythms. But for the patient, the frequency and phase synchronization breaks down, which is associated with the suppression of cortical regulatory functions when the flickering-color stimulus is applied, and higher frequencies start playing the dominating role. This suggests that the disruption of correlations in the MEG responses is the indicator of pathological changes leading to Photosensitive Epilepsy, which can be used for developing a method of diagnosing the disease based on the analysis with the FNS cross-correlation function.

  • dynamic effects and information quantifiers of statistical memory of meg s signals at Photosensitive Epilepsy
    Mathematical Biosciences and Engineering, 2008
    Co-Authors: R M Yulmetyev, Shinsuke Shimojo, Dinara G Yulmetyeva, Peter Hanggi, E V Khusaenova, Katsumi Watanabe, Joydeep Bhattacharya
    Abstract:

    The time series analysis of magnetoencephalographic (MEG) signals is very important both for basic brain research and for medical diagnosis and treatment. Here we discuss the crucial role of statistical memory effects (ME) in human brain functioning with Photosensitive Epilepsy (PSE). We study two independent statistical memory quantifiers that reflect the dynamical characteristics of neuromagnetic brain responses on a flickering stimulus of different colored combinations from a group of control subjects, which are contrasted with those from a patient with PSE. We analyze the frequency dependence of two memory measures for the neuromagnetic signals. The strong memory and the accompanying transition to a regular and robust regime of the signals' chaotic behavior in the separate areas are characteristic for a patient with PSE. This particularly interesting observation most likely identifies the regions of the protective mechanism in a human organism against occurrence of PSE.

  • analysis of biomedical signals by flicker noise spectroscopy identification of Photosensitive Epilepsy using magnetoencephalograms
    arXiv: Medical Physics, 2008
    Co-Authors: Serge F Timashev, Yuriy Polyakov, R M Yulmetyev, S A Demin, Yu O Panischev, Shinsuke Shimojo, Joydeep Bhattacharya
    Abstract:

    The flicker-noise spectroscopy (FNS) approach is used to determine the dynamic characteristics of neuromagnetic responses by analyzing the magnetoencephalographic (MEG) signals recorded as the response of a group of control human subjects and a patient with Photosensitive Epilepsy (PSE) to equiluminant flickering stimuli of different color combinations. Parameters characterizing the analyzed stochastic biomedical signals for different frequency bands are identified. It is shown that the classification of the parameters of analyzed MEG responses with respect to different frequency bands makes it possible to separate the contribution of the chaotic component from the overall complex dynamics of the signals. It is demonstrated that the chaotic component can be adequately described by the anomalous diffusion approximation in the case of control subjects. On the other hand, the chaotic component for the patient is characterized by a large number of high-frequency resonances. This implies that healthy organisms can suppress the perturbations brought about by the flickering stimuli and reorganize themselves. The organisms affected by Photosensitive Epilepsy no longer have this ability. This result also gives a way to simulate the separate stages of the brain cortex activity in vivo. The examples illustrating the use of the "FNS device" for identifying even the slightest individual differences in the activity of human brains using their responses to external standard stimuli show a unique possibility to develop the "individual medicine" of the future.

  • statistical memory of meg signals at Photosensitive Epilepsy
    International Journal of Bifurcation and Chaos, 2008
    Co-Authors: R M Yulmetyev, Shinsuke Shimojo, Dinara G Yulmetyeva, Peter Hanggi, E V Khusaenova, Katsumi Watanabe, Joydeep Bhattacharya
    Abstract:

    Here we discuss the remarkable role of the statistical memory effects in the human brain functioning at Photosensitive Epilepsy (PSE). We have analyzed three independent statistical memory quantifiers for the magnetoencephalographic (MEG) signals. These quantifiers reflect the dynamical characteristics of neuromagnetic brain responses to a flickering stimulus of different color combinations. Results for a group of control subjects are contrasted with those from a patient with PSE. The emergence of the strong memory and the transition to a regular and robust regime of chaotic behavior of the signals in separate areas is characteristic for a patient with PSE versus a healthy brain.

  • relaxation and phase space singularities in time series of human magnetoencephalograms as indicator of Photosensitive Epilepsy
    Physica A-statistical Mechanics and Its Applications, 2007
    Co-Authors: R M Yulmetyev, Shinsuke Shimojo, Joydeep Bhattacharya, Dinara G Yulmetyeva, Peter Hanggi, E V Khusaenova, Katsumi Watanabe
    Abstract:

    To analyze the crucial role of fluctuation and relaxation effects for the function of the human brain we studied some statistical quantifiers that support the information characteristics of neuromagnetic brain responses (magnetoencephalogram, MEG). The signals to a flickering stimulus of different color combinations have been obtained from a group of control subjects which is then contrasted with those of a patient suffering Photosensitive Epilepsy (PSE). We found that the existence of the specific stratification of the phase clouds and the concomitant relaxation singularities of the corresponding nonequilibrium dynamics of the chaotic behavior of the signals in separate areas in a patient provide likely indicators for the zones which are responsible for the appearance of PSE.

R M Yulmetyev - One of the best experts on this subject based on the ideXlab platform.

  • frequency and phase synchronization in neuromagnetic cortical responses to flickering color stimuli
    Laser Physics, 2010
    Co-Authors: Serge F Timashev, R M Yulmetyev, S A Demin, Yu O Panischev, Shinsuke Shimojo, Joydeep Bhattacharya, Yuriy S Polyakov
    Abstract:

    In our earlier study dealing with the analysis of neuromagnetic responses (magnetoencephalograms—MEG) to flickering-color stimuli for a group of control human subjects (9 volunteers) and a patient with Photosensitive Epilepsy (a 12-year old girl), it was shown that Flicker-Noise Spectroscopy (FNS) was able to identify specific differences in the responses of each organism. The high specificity of individual MEG responses manifested itself in the values of FNS parameters for both chaotic and resonant components of the original signal. The present study applies the FNS cross-correlation function to the analysis of correlations between the MEG responses simultaneously measured at spatially separated points of the human cortex processing the red-blue flickering color stimulus. It is shown that the cross-correlations for control (healthy) subjects are characterized by frequency and phase synchronization at different points of the cortex, with the dynamics of neuromagnetic responses being determined by the low-frequency processes that correspond to normal physiological rhythms. But for the patient, the frequency and phase synchronization breaks down, which is associated with the suppression of cortical regulatory functions when the flickering-color stimulus is applied, and higher frequencies start playing the dominating role. This suggests that the disruption of correlations in the MEG responses is the indicator of pathological changes leading to Photosensitive Epilepsy, which can be used for developing a method of diagnosing the disease based on the analysis with the FNS cross-correlation function.

  • dynamic effects and information quantifiers of statistical memory of meg s signals at Photosensitive Epilepsy
    Mathematical Biosciences and Engineering, 2008
    Co-Authors: R M Yulmetyev, Shinsuke Shimojo, Dinara G Yulmetyeva, Peter Hanggi, E V Khusaenova, Katsumi Watanabe, Joydeep Bhattacharya
    Abstract:

    The time series analysis of magnetoencephalographic (MEG) signals is very important both for basic brain research and for medical diagnosis and treatment. Here we discuss the crucial role of statistical memory effects (ME) in human brain functioning with Photosensitive Epilepsy (PSE). We study two independent statistical memory quantifiers that reflect the dynamical characteristics of neuromagnetic brain responses on a flickering stimulus of different colored combinations from a group of control subjects, which are contrasted with those from a patient with PSE. We analyze the frequency dependence of two memory measures for the neuromagnetic signals. The strong memory and the accompanying transition to a regular and robust regime of the signals' chaotic behavior in the separate areas are characteristic for a patient with PSE. This particularly interesting observation most likely identifies the regions of the protective mechanism in a human organism against occurrence of PSE.

  • analysis of biomedical signals by flicker noise spectroscopy identification of Photosensitive Epilepsy using magnetoencephalograms
    arXiv: Medical Physics, 2008
    Co-Authors: Serge F Timashev, Yuriy Polyakov, R M Yulmetyev, S A Demin, Yu O Panischev, Shinsuke Shimojo, Joydeep Bhattacharya
    Abstract:

    The flicker-noise spectroscopy (FNS) approach is used to determine the dynamic characteristics of neuromagnetic responses by analyzing the magnetoencephalographic (MEG) signals recorded as the response of a group of control human subjects and a patient with Photosensitive Epilepsy (PSE) to equiluminant flickering stimuli of different color combinations. Parameters characterizing the analyzed stochastic biomedical signals for different frequency bands are identified. It is shown that the classification of the parameters of analyzed MEG responses with respect to different frequency bands makes it possible to separate the contribution of the chaotic component from the overall complex dynamics of the signals. It is demonstrated that the chaotic component can be adequately described by the anomalous diffusion approximation in the case of control subjects. On the other hand, the chaotic component for the patient is characterized by a large number of high-frequency resonances. This implies that healthy organisms can suppress the perturbations brought about by the flickering stimuli and reorganize themselves. The organisms affected by Photosensitive Epilepsy no longer have this ability. This result also gives a way to simulate the separate stages of the brain cortex activity in vivo. The examples illustrating the use of the "FNS device" for identifying even the slightest individual differences in the activity of human brains using their responses to external standard stimuli show a unique possibility to develop the "individual medicine" of the future.

  • statistical memory of meg signals at Photosensitive Epilepsy
    International Journal of Bifurcation and Chaos, 2008
    Co-Authors: R M Yulmetyev, Shinsuke Shimojo, Dinara G Yulmetyeva, Peter Hanggi, E V Khusaenova, Katsumi Watanabe, Joydeep Bhattacharya
    Abstract:

    Here we discuss the remarkable role of the statistical memory effects in the human brain functioning at Photosensitive Epilepsy (PSE). We have analyzed three independent statistical memory quantifiers for the magnetoencephalographic (MEG) signals. These quantifiers reflect the dynamical characteristics of neuromagnetic brain responses to a flickering stimulus of different color combinations. Results for a group of control subjects are contrasted with those from a patient with PSE. The emergence of the strong memory and the transition to a regular and robust regime of chaotic behavior of the signals in separate areas is characteristic for a patient with PSE versus a healthy brain.

  • relaxation and phase space singularities in time series of human magnetoencephalograms as indicator of Photosensitive Epilepsy
    Physica A-statistical Mechanics and Its Applications, 2007
    Co-Authors: R M Yulmetyev, Shinsuke Shimojo, Joydeep Bhattacharya, Dinara G Yulmetyeva, Peter Hanggi, E V Khusaenova, Katsumi Watanabe
    Abstract:

    To analyze the crucial role of fluctuation and relaxation effects for the function of the human brain we studied some statistical quantifiers that support the information characteristics of neuromagnetic brain responses (magnetoencephalogram, MEG). The signals to a flickering stimulus of different color combinations have been obtained from a group of control subjects which is then contrasted with those of a patient suffering Photosensitive Epilepsy (PSE). We found that the existence of the specific stratification of the phase clouds and the concomitant relaxation singularities of the corresponding nonequilibrium dynamics of the chaotic behavior of the signals in separate areas in a patient provide likely indicators for the zones which are responsible for the appearance of PSE.

Laura Restani - One of the best experts on this subject based on the ideXlab platform.

  • platform session nibs altered recovery from inhibitory repetitive transcranial magnetic stimulation rtms in subjects with Photosensitive Epilepsy
    Clinical Neurophysiology, 2018
    Co-Authors: T Occi, Matteo Caleo, Laura Restani, Simone Rossi, Anna De Rosa, Ferdinando Sartucci
    Abstract:

    Introduction Only few studies have explored the pathophysiology of PSE; some Authors have suggested a defective visual inhibition as a contributing factor to photoparoxysmal response, pointing to an overactive visuomotor connectivity thus inducing abnormal motor responses. In order to investigate functional changes underlying photosensitivity, we studied the response of the visual cortex to low-frequency, inhibitory repetitive transcranial magnetic stimulation (rTMS) in drug-free patients with Photosensitive seizures and healthy volunteers. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different luminance contrasts (K20%, K50% and K90%) were recorded in both hemispheres before and after transient functional inactivation of the occipital cortex of one side via low-frequency rTMS (0.5 Hz, at 120 % of resting motor threshold, for 20’). VEPs were recorded before (T0), immediately after (T1) and 45’ following the completion of rTMS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Results Baseline amplitudes of the VEP components (N1 and P1) were enhanced in Photosensitive patients. At T1, rTMS produced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a concurrent facilitation of responses in the contralateral hemisphere. Compared with PSE subjects, VEP amplitudes remained persistently dampened in the stimulated hemisphere of controls (Holm–Sidak post hoc method, p  Conclusion The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity may play a role in the pathophysiology of Photosensitive Epilepsy. Beyond the stereotyped dichotomy between generalized and focal epilepsies, our data seem to indicate PSE as a “system disease”.

  • altered recovery from inhibitory repetitive transcranial magnetic stimulation rtms in subjects with Photosensitive Epilepsy
    Clinical Neurophysiology, 2016
    Co-Authors: Tommaso Bocci, Matteo Caleo, Laura Restani, Simone Rossi, D Barloscio, Ferdinando Sartucci
    Abstract:

    Objective To investigate functional changes underlying photosensitivity, we studied the response of the visual cortex to low-frequency, inhibitory repetitive transcranial magnetic stimulation (rTMS) in patients with Photosensitive seizures and healthy volunteers. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts were recorded in both hemispheres before and after inactivation of the occipital cortex of one side via low-frequency rTMS (0.5 Hz, 120 % RMT, 20′). VEPs were recorded before (T0), immediately after (T1) and 45′ following rTMS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Results Baseline amplitudes of the VEP components (N1 and P1) were enhanced in Photosensitive patients. At T1, rTMS produced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a concurrent facilitation of responses in the contralateral hemisphere. Compared with PSE subjects, VEP amplitudes remained persistently dampened in the stimulated hemisphere of controls (Holm-Sidak post hoc method, p p Conclusions The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity may play a role in the pathophysiology of Photosensitive Epilepsy. Significance beyond the stereotyped dichotomy between generalized and focal epilepsies, both sets of data seem to indicate PSE as a “system disease”.

  • 109 Photosensitive Epilepsy role of corpus callosum in cortical excitability
    Clinical Neurophysiology, 2015
    Co-Authors: Ferdinando Sartucci, Tommaso Bocci, A Torzini, Matteo Caleo, Elisa Giorli, Laura Restani, Simone Rossi, Lamberto Maffei
    Abstract:

    Photosensitive Epilepsy (PE) is a form of epileptic seizure induced by several powerful visual stimuli. Cortical mechanisms underlying paroxysmal activity have been widely studied in several ways. Here, we employed rTMS in an attempt to disclose the role of callosal input in modulating cortical visual excitability in both healthy subjects and PE patients. We enrolled 10 healthy subjects (5 males and 5 females; mean age 16.8 ± 3.4 yrs) and 5 patients (15.9 ± 4.2 yrs). Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts were recorded before and after functional inactivation of the occipital cortex of one hemisphere via off-line low-frequency repetitive transcranial magnetic stimulation (rTMS; 0.5 Hz stimulation for 20 min). VEPs were recorded in V1 before (T0), immediately after (T1) and 45′ following the end of rTMS (T2). We found that low-frequency rTMS had an inhibitory effect on VEP amplitudes at all contrasts in the treated side in controls and patients. Reduction of VEP amplitudes in the inhibited hemisphere at T1 was accompanied by an increase in VEP amplitudes in the contralateral side at mid-high contrasts (50–90%) in healthy subjects ( p p p

Simone Rossi - One of the best experts on this subject based on the ideXlab platform.

  • platform session nibs altered recovery from inhibitory repetitive transcranial magnetic stimulation rtms in subjects with Photosensitive Epilepsy
    Clinical Neurophysiology, 2018
    Co-Authors: T Occi, Matteo Caleo, Laura Restani, Simone Rossi, Anna De Rosa, Ferdinando Sartucci
    Abstract:

    Introduction Only few studies have explored the pathophysiology of PSE; some Authors have suggested a defective visual inhibition as a contributing factor to photoparoxysmal response, pointing to an overactive visuomotor connectivity thus inducing abnormal motor responses. In order to investigate functional changes underlying photosensitivity, we studied the response of the visual cortex to low-frequency, inhibitory repetitive transcranial magnetic stimulation (rTMS) in drug-free patients with Photosensitive seizures and healthy volunteers. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different luminance contrasts (K20%, K50% and K90%) were recorded in both hemispheres before and after transient functional inactivation of the occipital cortex of one side via low-frequency rTMS (0.5 Hz, at 120 % of resting motor threshold, for 20’). VEPs were recorded before (T0), immediately after (T1) and 45’ following the completion of rTMS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Results Baseline amplitudes of the VEP components (N1 and P1) were enhanced in Photosensitive patients. At T1, rTMS produced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a concurrent facilitation of responses in the contralateral hemisphere. Compared with PSE subjects, VEP amplitudes remained persistently dampened in the stimulated hemisphere of controls (Holm–Sidak post hoc method, p  Conclusion The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity may play a role in the pathophysiology of Photosensitive Epilepsy. Beyond the stereotyped dichotomy between generalized and focal epilepsies, our data seem to indicate PSE as a “system disease”.

  • altered recovery from inhibitory repetitive transcranial magnetic stimulation rtms in subjects with Photosensitive Epilepsy
    Clinical Neurophysiology, 2016
    Co-Authors: Tommaso Bocci, Matteo Caleo, Laura Restani, Simone Rossi, D Barloscio, Ferdinando Sartucci
    Abstract:

    Objective To investigate functional changes underlying photosensitivity, we studied the response of the visual cortex to low-frequency, inhibitory repetitive transcranial magnetic stimulation (rTMS) in patients with Photosensitive seizures and healthy volunteers. Methods Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts were recorded in both hemispheres before and after inactivation of the occipital cortex of one side via low-frequency rTMS (0.5 Hz, 120 % RMT, 20′). VEPs were recorded before (T0), immediately after (T1) and 45′ following rTMS (T2). The display was either centered on the vertical meridian (central stimulation) or positioned in the right hemifield (with its inner edge at a distance of 1 degree from the fixation point). Results Baseline amplitudes of the VEP components (N1 and P1) were enhanced in Photosensitive patients. At T1, rTMS produced an inhibitory effect on VEPs amplitudes at all contrasts in the targeted side and a concurrent facilitation of responses in the contralateral hemisphere. Compared with PSE subjects, VEP amplitudes remained persistently dampened in the stimulated hemisphere of controls (Holm-Sidak post hoc method, p p Conclusions The rapid recovery of excitability and the persistent transcallosal disinhibition following perturbation of cortical activity may play a role in the pathophysiology of Photosensitive Epilepsy. Significance beyond the stereotyped dichotomy between generalized and focal epilepsies, both sets of data seem to indicate PSE as a “system disease”.

  • 109 Photosensitive Epilepsy role of corpus callosum in cortical excitability
    Clinical Neurophysiology, 2015
    Co-Authors: Ferdinando Sartucci, Tommaso Bocci, A Torzini, Matteo Caleo, Elisa Giorli, Laura Restani, Simone Rossi, Lamberto Maffei
    Abstract:

    Photosensitive Epilepsy (PE) is a form of epileptic seizure induced by several powerful visual stimuli. Cortical mechanisms underlying paroxysmal activity have been widely studied in several ways. Here, we employed rTMS in an attempt to disclose the role of callosal input in modulating cortical visual excitability in both healthy subjects and PE patients. We enrolled 10 healthy subjects (5 males and 5 females; mean age 16.8 ± 3.4 yrs) and 5 patients (15.9 ± 4.2 yrs). Visual evoked potentials (VEPs) triggered by grating stimuli of different contrasts were recorded before and after functional inactivation of the occipital cortex of one hemisphere via off-line low-frequency repetitive transcranial magnetic stimulation (rTMS; 0.5 Hz stimulation for 20 min). VEPs were recorded in V1 before (T0), immediately after (T1) and 45′ following the end of rTMS (T2). We found that low-frequency rTMS had an inhibitory effect on VEP amplitudes at all contrasts in the treated side in controls and patients. Reduction of VEP amplitudes in the inhibited hemisphere at T1 was accompanied by an increase in VEP amplitudes in the contralateral side at mid-high contrasts (50–90%) in healthy subjects ( p p p