Halawa, Islam F.

[["dc.bibliographiccitation.firstpage","1244"],["dc.bibliographiccitation.issue","5"],["dc.bibliographiccitation.journal","Brain Stimulation"],["dc.bibliographiccitation.lastpage","1252"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Halawa, I."],["dc.contributor.author","Shirota, Y."],["dc.contributor.author","Neef, A."],["dc.contributor.author","Sommer, M."],["dc.contributor.author","Paulus, W."],["dc.date.accessioned","2020-12-10T14:22:48Z"],["dc.date.available","2020-12-10T14:22:48Z"],["dc.date.issued","2019"],["dc.identifier.doi","10.1016/j.brs.2019.04.012"],["dc.identifier.issn","1935-861X"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/71740"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-354"],["dc.title","Neuronal tuning: Selective targeting of neuronal populations via manipulation of pulse width and directionality"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.journal","Frontiers in Neuroscience"],["dc.bibliographiccitation.volume","15"],["dc.contributor.author","Halawa, Islam"],["dc.contributor.author","Reichert, Katharina"],["dc.contributor.author","Aberra, Aman S."],["dc.contributor.author","Sommer, Martin"],["dc.contributor.author","Peterchev, Angel V."],["dc.contributor.author","Paulus, Walter"],["dc.date.accessioned","2022-01-11T14:06:15Z"],["dc.date.available","2022-01-11T14:06:15Z"],["dc.date.issued","2021"],["dc.description.abstract","Introduction: High frequency repetitive transcranial magnetic stimulation applied to the motor cortex causes an increase in the amplitude of motor evoked potentials (MEPs) that persists after stimulation. Here, we focus on the aftereffects generated by high frequency controllable pulse TMS (cTMS) with different directions, intensities, and pulse durations. Objectives: To investigate the influence of pulse duration, direction, and amplitude in correlation to induced depolarization on the excitatory plastic aftereffects of 5 Hz repetitive transcranial magnetic stimulation (rTMS) using bidirectional cTMS pulses. Methods: We stimulated the hand motor cortex with 5 Hz rTMS applying 1,200 bidirectional pulses with the main component durations of 80, 100, and 120 μs using a controllable pulse stimulator TMS (cTMS). Fourteen healthy subjects were investigated in nine sessions with 80% resting motor threshold (RMT) for posterior-anterior (PA) and 80 and 90% RMT anterior-posterior (AP) induced current direction. We used a model approximating neuronal membranes as a linear first order low-pass filter to estimate the strength–duration time constant and to simulate the membrane polarization produced by each waveform. Results: PA and AP 5 Hz rTMS at 80% RMT produced no significant excitation. An exploratory analysis indicated that 90% RMT AP stimulation with 100 and 120 μs pulses but not 80 μs pulses led to significant excitation. We found a positive correlation between the plastic outcome of each session and the simulated peak neural membrane depolarization for time constants >100 μs. This correlation was strongest for neural elements that are depolarized by the main phase of the AP pulse, suggesting the effects were dependent on pulse direction. Conclusions: Among the tested conditions, only 5 Hz rTMS with higher intensity and wider pulses appeared to produce excitatory aftereffects. This correlated with the greater depolarization of neural elements with time constants slower than the directly activated neural elements responsible for producing the motor output (e.g., somatic or dendritic membrane). Significance: Higher intensities and wider pulses seem to be more efficient in inducing excitation. If confirmed, this observation could lead to better results in future clinical studies performed with wider pulses."],["dc.description.abstract","Introduction: High frequency repetitive transcranial magnetic stimulation applied to the motor cortex causes an increase in the amplitude of motor evoked potentials (MEPs) that persists after stimulation. Here, we focus on the aftereffects generated by high frequency controllable pulse TMS (cTMS) with different directions, intensities, and pulse durations. Objectives: To investigate the influence of pulse duration, direction, and amplitude in correlation to induced depolarization on the excitatory plastic aftereffects of 5 Hz repetitive transcranial magnetic stimulation (rTMS) using bidirectional cTMS pulses. Methods: We stimulated the hand motor cortex with 5 Hz rTMS applying 1,200 bidirectional pulses with the main component durations of 80, 100, and 120 μs using a controllable pulse stimulator TMS (cTMS). Fourteen healthy subjects were investigated in nine sessions with 80% resting motor threshold (RMT) for posterior-anterior (PA) and 80 and 90% RMT anterior-posterior (AP) induced current direction. We used a model approximating neuronal membranes as a linear first order low-pass filter to estimate the strength–duration time constant and to simulate the membrane polarization produced by each waveform. Results: PA and AP 5 Hz rTMS at 80% RMT produced no significant excitation. An exploratory analysis indicated that 90% RMT AP stimulation with 100 and 120 μs pulses but not 80 μs pulses led to significant excitation. We found a positive correlation between the plastic outcome of each session and the simulated peak neural membrane depolarization for time constants >100 μs. This correlation was strongest for neural elements that are depolarized by the main phase of the AP pulse, suggesting the effects were dependent on pulse direction. Conclusions: Among the tested conditions, only 5 Hz rTMS with higher intensity and wider pulses appeared to produce excitatory aftereffects. This correlated with the greater depolarization of neural elements with time constants slower than the directly activated neural elements responsible for producing the motor output (e.g., somatic or dendritic membrane). Significance: Higher intensities and wider pulses seem to be more efficient in inducing excitation. If confirmed, this observation could lead to better results in future clinical studies performed with wider pulses."],["dc.identifier.doi","10.3389/fnins.2021.773792"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/97863"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-507"],["dc.publisher","Frontiers Media S.A."],["dc.relation.eissn","1662-453X"],["dc.rights","http://creativecommons.org/licenses/by/4.0/"],["dc.title","Effect of Pulse Duration and Direction on Plasticity Induced by 5 Hz Repetitive Transcranial Magnetic Stimulation in Correlation With Neuronal Depolarization"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","340"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","Journal of Neurophysiology"],["dc.bibliographiccitation.lastpage","348"],["dc.bibliographiccitation.volume","126"],["dc.contributor.author","Shorafa, Y."],["dc.contributor.author","Halawa, I."],["dc.contributor.author","Hewitt, M."],["dc.contributor.author","Nitsche, M. A."],["dc.contributor.author","Antal, A."],["dc.contributor.author","Paulus, W."],["dc.date.accessioned","2021-10-01T09:58:12Z"],["dc.date.available","2021-10-01T09:58:12Z"],["dc.date.issued","2021"],["dc.description.abstract","Stimulation intensity and activation of center versus surround muscles affect cortical excitability alterations generated by 140-Hz tACS. At rest, excitatory aftereffects were induced by tACS with 1 mA, but not 2 mA stimulation intensity. With agonistic muscle activation, excitability first decreases, and then increases with 2 mA. For antagonist activation, the MEP amplitude reduction observed in the sham condition is counteracted upon by 1 and 2 mA tACS. This reflects the relation of LTP-like aftereffects to Ca 2+ concentration alterations."],["dc.description.abstract","During transcranial electric stimulation, increasing intracellular Ca 2+ levels beyond those needed for inducing long term potentiation (LTP) may collapse aftereffects. State-dependent plastic aftereffects are reduced when applied during muscle activation as compared with rest. Cortical surround inhibition by antagonistic muscle activation inhibits the center-innervated agonist. The objective of this study is to determine the interaction of state dependency of transcranial alternating current stimulation (tACS) aftereffects at rest and under activation of agonist and antagonist muscles during stimulation with different intensities. In 13 healthy participants, we measured motor-evoked potential (MEP) amplitudes before and after applying tACS at 140 Hz over the motor cortex in nine single-blinded sessions using sham, 1 mA, and 2 mA stimulation intensities during rest and activation of agonist and antagonist muscles. During rest, only 1 mA tACS produced a significant MEP increase, whereas the 2 mA stimulation produced no significant MEP size shift. During agonist activation 1 mA did not induce MEP changes; after 2 mA, first a decrease and later an increase of MEPs were observed. Antagonist activation under sham tACS led to an inhibition, which was restored to baseline by 1 and 2 mA tACS. Increasing stimulation intensity beyond 1 mA does not increase excitability, compatible with too strong intracellular Ca 2+ increase. Antagonist innervation leads to MEP inhibition, supporting the concept of surround inhibition, which can be overcome by tACS at both intensities. During agonist innervation, a tACS dose-dependent relationship exists. Our results integrate concepts of “leaky membranes” under activation, surround inhibition, intracellular Ca 2+ increase, and their role in the aftereffects of tACS. NEW & NOTEWORTHY Stimulation intensity and activation of center versus surround muscles affect cortical excitability alterations generated by 140-Hz tACS. At rest, excitatory aftereffects were induced by tACS with 1 mA, but not 2 mA stimulation intensity. With agonistic muscle activation, excitability first decreases, and then increases with 2 mA. For antagonist activation, the MEP amplitude reduction observed in the sham condition is counteracted upon by 1 and 2 mA tACS. This reflects the relation of LTP-like aftereffects to Ca 2+ concentration alterations."],["dc.description.abstract","Stimulation intensity and activation of center versus surround muscles affect cortical excitability alterations generated by 140-Hz tACS. At rest, excitatory aftereffects were induced by tACS with 1 mA, but not 2 mA stimulation intensity. With agonistic muscle activation, excitability first decreases, and then increases with 2 mA. For antagonist activation, the MEP amplitude reduction observed in the sham condition is counteracted upon by 1 and 2 mA tACS. This reflects the relation of LTP-like aftereffects to Ca 2+ concentration alterations."],["dc.description.abstract","During transcranial electric stimulation, increasing intracellular Ca 2+ levels beyond those needed for inducing long term potentiation (LTP) may collapse aftereffects. State-dependent plastic aftereffects are reduced when applied during muscle activation as compared with rest. Cortical surround inhibition by antagonistic muscle activation inhibits the center-innervated agonist. The objective of this study is to determine the interaction of state dependency of transcranial alternating current stimulation (tACS) aftereffects at rest and under activation of agonist and antagonist muscles during stimulation with different intensities. In 13 healthy participants, we measured motor-evoked potential (MEP) amplitudes before and after applying tACS at 140 Hz over the motor cortex in nine single-blinded sessions using sham, 1 mA, and 2 mA stimulation intensities during rest and activation of agonist and antagonist muscles. During rest, only 1 mA tACS produced a significant MEP increase, whereas the 2 mA stimulation produced no significant MEP size shift. During agonist activation 1 mA did not induce MEP changes; after 2 mA, first a decrease and later an increase of MEPs were observed. Antagonist activation under sham tACS led to an inhibition, which was restored to baseline by 1 and 2 mA tACS. Increasing stimulation intensity beyond 1 mA does not increase excitability, compatible with too strong intracellular Ca 2+ increase. Antagonist innervation leads to MEP inhibition, supporting the concept of surround inhibition, which can be overcome by tACS at both intensities. During agonist innervation, a tACS dose-dependent relationship exists. Our results integrate concepts of “leaky membranes” under activation, surround inhibition, intracellular Ca 2+ increase, and their role in the aftereffects of tACS. NEW & NOTEWORTHY Stimulation intensity and activation of center versus surround muscles affect cortical excitability alterations generated by 140-Hz tACS. At rest, excitatory aftereffects were induced by tACS with 1 mA, but not 2 mA stimulation intensity. With agonistic muscle activation, excitability first decreases, and then increases with 2 mA. For antagonist activation, the MEP amplitude reduction observed in the sham condition is counteracted upon by 1 and 2 mA tACS. This reflects the relation of LTP-like aftereffects to Ca 2+ concentration alterations."],["dc.identifier.doi","10.1152/jn.00065.2021"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/90008"],["dc.language.iso","en"],["dc.notes.intern","DOI Import GROB-469"],["dc.relation.eissn","1522-1598"],["dc.relation.issn","0022-3077"],["dc.title","Isometric agonist and antagonist muscle activation interacts differently with 140-Hz transcranial alternating current stimulation aftereffects at different intensities"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","287"],["dc.bibliographiccitation.issue","4"],["dc.bibliographiccitation.journal","Neurosciences"],["dc.bibliographiccitation.lastpage","291"],["dc.bibliographiccitation.volume","22"],["dc.contributor.author","Halawa, Islam F."],["dc.contributor.author","El Sayed, Basma B."],["dc.contributor.author","Amin, Omnia R."],["dc.contributor.author","Meguid, Nagwa A."],["dc.contributor.author","Kader, Ann A. Abdel"],["dc.date.accessioned","2021-06-01T10:48:30Z"],["dc.date.available","2021-06-01T10:48:30Z"],["dc.date.issued","2020"],["dc.identifier.doi","10.17712/nsj.2017.4.20170067"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/85959"],["dc.language.iso","en"],["dc.notes.intern","DOI-Import GROB-425"],["dc.relation.eissn","1658-3183"],["dc.title","Frontal theta/beta ratio changes during TOVA in Egyptian ADHD children"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","358"],["dc.bibliographiccitation.firstpage","1"],["dc.bibliographiccitation.journal","Frontiers in Neuroscience"],["dc.bibliographiccitation.lastpage","12"],["dc.bibliographiccitation.volume","12"],["dc.contributor.author","Halawa, Islam"],["dc.contributor.author","Goldental, Amir"],["dc.contributor.author","Shirota, Yuichiro"],["dc.contributor.author","Kanter, Ido"],["dc.contributor.author","Paulus, Walter"],["dc.date.accessioned","2018-10-10T09:39:17Z"],["dc.date.available","2018-10-10T09:39:17Z"],["dc.date.issued","2018"],["dc.description.abstract","Introduction: rTMS has been proven effective in the treatment of neuropsychiatric conditions, with class A (definite efficacy) evidence for treatment of depression and pain (Lefaucheur et al., 2014). The efficacy in stimulation protocols is, however, quite heterogeneous. Saturation of neuronal firing by HFrTMS without allowing time for recovery may lead to neuronal response failures (NRFs) that compromise the efficacy of stimulation with higher frequencies. Objectives: To examine the efficacy of different rTMS temporal stimulation patterns focusing on a possible upper stimulation limit related to response failures. Protocol patterns were derived from published clinical studies on therapeutic rTMS for depression and pain. They were compared with conduction failures in cell cultures. Methodology: From 57 papers using protocols rated class A for depression and pain (Lefaucheur et al., 2014) we extracted Inter-train interval (ITI), average frequency, total duration and total number of pulses and plotted them against the percent improvement on the outcome scale. Specifically, we compared 10 Hz trains with ITIs of 8 s (protocol A) and 26 s (protocol B) in vitro on cultured cortical neurons. Results: In the in vitro experiments, protocol A with 8-s ITIs resulted in more frequent response failures, while practically no response failures occurred with protocol B (26-s intervals). The HFrTMS protocol analysis exhibited no significant effect of ITIs on protocol efficiency. Discussion: In the neuronal culture, longer ITIs appeared to allow the neuronal response to recover. In the available human dataset on both depression and chronic pain, data concerning shorter ITIs is does not allow a significant conclusion. Significance: NRF may interfere with the efficacy of rTMS stimulation protocols when the average stimulation frequency is too high, proposing ITIs as a variable in rTMS protocol efficacy. Clinical trials are necessary to examine effect of shorter ITIs on the clinical outcome in a controlled setting."],["dc.description.sponsorship","Open-Access-Publikationsfonds 2018"],["dc.identifier.doi","10.3389/fnins.2018.00358"],["dc.identifier.pmid","29910706"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?gs-1/15266"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/15935"],["dc.language.iso","en"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","final"],["dc.publisher","Frontiers Media S.A."],["dc.relation.eissn","1662-453X"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","Less Might Be More"],["dc.title.subtitle","Conduction Failure as a Factor Possibly Limiting the Efficacy of Higher Frequencies in rTMS Protocols"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]