The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Binith Cheeran - One of the best experts on this subject based on the ideXlab platform.
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intra Individual Variability in the response to anodal transcranial direct current stimulation
Clinical Neurophysiology, 2015Co-Authors: Virginia Lopezalonso, Binith Cheeran, Miguel Fernandezdelolmo, Alessia Costantini, Juan Jose GonzalezhenriquezAbstract:Abstract Objective To test the intra-Individual reliability in response to anodal transcranial direct current stimulation (AtDCS). Methods 45 healthy subjects received AtDCS (1 mA, 13 min) in two separate sessions, 6–12 months apart. Motor evoked potentials were collected at baseline and then at 5-min intervals after AtDCS for 1 h. Short intracortical inhibition (SICI) was assessed at minutes 6 and 46 after AtDCS. Results AtDCS increased cortical excitability over minutes 0–30 post-stimulation in both sessions, with fair intra-Individual reliability. 60% and 64% of subjects responded with the expected increase in cortical excitability in each session, respectively. 69% of the subjects maintained their response pattern between sessions during this timeframe. However, there were no significant effects on cortical excitability over the full hour post AtDCS in either session. SICI showed fair intra-Individual reliability 6 min after AtDCS. Conclusion A change in cortical excitability in the first half-hour post-AtDCS may be a good predictor of the response in a subsequent session. Furthermore, minute 15 post-stimulation showed the maximum increase in cortical excitability in both sessions. Significance We show for the first time that intra-Individual Variability is lower than inter-Individual Variability, and with fair intra-Individual inter-sessional reliability for 30 min after AtDCS-subjects are likely to maintain their response patterns to tDCS between sessions, with implications for experimental and therapeutic applications of tDCS.
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inter Individual Variability in response to non invasive brain stimulation paradigms
Brain Stimulation, 2014Co-Authors: Virginia Lopezalonso, Binith Cheeran, Dan Riorodriguez, Miguel FernandezdelolmoAbstract:BACKGROUND: Non-invasive Brain Stimulation (NIBS) paradigms are unique in their ability to safely modulate cortical plasticity for experimental or therapeutic applications. However, increasingly, there is concern regarding inter-Individual Variability in the efficacy and reliability of these paradigms. HYPOTHESIS: Inter-Individual Variability in response to NIBS paradigms would be better explained if a multimodal distribution was assumed. METHODS: In three different sessions for each subject (n = 56), we studied the Paired Associative Stimulation (PAS25), Anodal transcranial DC stimulation (AtDCS) and intermittent theta burst stimulation (iTBS) protocols. We applied cluster analysis to detect distinct patterns of response between Individuals. Furthermore, we tested whether baseline TMS measures (such as short intracortical inhibition (SICI), resting motor threshold (RMT)) or factors such as time of day could predict each Individual's response pattern. RESULTS: All three paradigms show similar efficacy over the first hour post stimulation--there is no significant effect on excitatory or inhibitory circuits for the whole sample, and AtDCS fares no better than iTBS or PAS25. Cluster analysis reveals a bimodal response pattern--but only 39%, 45% and 43% of subjects responded as expected to PAS25, AtDCS, and iTBS respectively. Pre-stimulation SICI accounted for 10% of the Variability in response to PAS25, but no other baseline measures were predictive of response. Finally, we report implications for sample size calculation and the remarkable effect of sample enrichment. CONCLUSION: The implications of the high rate of 'dose-failure' for experimental and therapeutic applications of NIBS lead us to conclude that addressing inter-Individual Variability is a key area of concern for the field.
Benjamin Y Tseng - One of the best experts on this subject based on the ideXlab platform.
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Individual Variability of cerebral autoregulation posterior cerebral circulation and white matter hyperintensity
The Journal of Physiology, 2016Co-Authors: Benjamin Y Tseng, Muhammad Ayaz Khan, Takashi Tarumi, Candace Hill, Niki Mirshams, Timea Hodics, Linda S HynanAbstract:KEY POINTS: Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about Individual Variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large Individual Variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT: This study measured the Individual Variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large Individual Variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P < 0.01). Collectively, these findings demonstrated the presence of large Individual Variability of CA in older adults, and that, when measured in the posterior cerebral circulation, it is the higher rather than lower CA reactivity that is associated with WMH severity.
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Individual Variability of cerebral autoregulation, posterior cerebral circulation and white matter hyperintensity
The Journal of Physiology, 2016Co-Authors: Benjamin Y Tseng, Muhammad Ayaz Khan, Takashi Tarumi, Candace Hill, Niki Mirshams, Timea Hodics, Linda S Hynan, Rong ZhangAbstract:KEY POINTS: Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about Individual Variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large Individual Variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT: This study measured the Individual Variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large Individual Variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P
Linda S Hynan - One of the best experts on this subject based on the ideXlab platform.
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Individual Variability of cerebral autoregulation posterior cerebral circulation and white matter hyperintensity
The Journal of Physiology, 2016Co-Authors: Benjamin Y Tseng, Muhammad Ayaz Khan, Takashi Tarumi, Candace Hill, Niki Mirshams, Timea Hodics, Linda S HynanAbstract:KEY POINTS: Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about Individual Variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large Individual Variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT: This study measured the Individual Variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large Individual Variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P < 0.01). Collectively, these findings demonstrated the presence of large Individual Variability of CA in older adults, and that, when measured in the posterior cerebral circulation, it is the higher rather than lower CA reactivity that is associated with WMH severity.
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Individual Variability of cerebral autoregulation, posterior cerebral circulation and white matter hyperintensity
The Journal of Physiology, 2016Co-Authors: Benjamin Y Tseng, Muhammad Ayaz Khan, Takashi Tarumi, Candace Hill, Niki Mirshams, Timea Hodics, Linda S Hynan, Rong ZhangAbstract:KEY POINTS: Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about Individual Variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large Individual Variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT: This study measured the Individual Variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large Individual Variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P
Kerrieanne Ho - One of the best experts on this subject based on the ideXlab platform.
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inter and intra Individual Variability in response to transcranial direct current stimulation tdcs at varying current intensities
Brain Stimulation, 2015Co-Authors: Taariq Chew, Kerrieanne HoAbstract:Abstract Background Translation of transcranial direct current stimulation (tDCS) from research to clinical practice is hindered by a lack of consensus on optimal stimulation parameters, significant inter-Individual Variability in response, and in sufficient intra-Individual reliability data. Objectives Inter-Individual differences in response to anodal tDCS at a range of current intensities were explored. Intra-Individual reliability in response to anodal tDCS across two identical sessions was also investigated. Methods Twenty-nine subjects participated in a crossover study. Anodal-tDCS using four different current intensities (0.2, 0.5, 1 and 2 mA), with an anode size of 16 cm 2 , was tested. The 0.5 mA condition was repeated to assess intra-Individual Variability. TMS was used to elicit 40 motor-evoked potentials (MEPs) before 10 min of tDCS, and 20 MEPs at four time-points over 30 min following tDCS. Results ANOVA revealed no main effect of TIME for all conditions except the first 0.5 mA condition, and no differences in response between the four current intensities. Cluster analysis identified two clusters for the 0.2 and 2 mA conditions only. Frequency distributions based on Individual subject responses (excitatory, inhibitory or no response) to each condition indicate possible differential responses between Individuals to different current intensities. Test-retest reliability was negligible (ICC (2,1) = −0.50). Conclusions Significant inter-Individual Variability in response to tDCS across a range of current intensities was found. 2 mA and 0.2 mA tDCS were most effective at inducing a distinct response. Significant intra-Individual Variability in response to tDCS was also found. This has implications for interpreting results of single-session tDCS experiments.
Muhammad Ayaz Khan - One of the best experts on this subject based on the ideXlab platform.
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Individual Variability of cerebral autoregulation posterior cerebral circulation and white matter hyperintensity
The Journal of Physiology, 2016Co-Authors: Benjamin Y Tseng, Muhammad Ayaz Khan, Takashi Tarumi, Candace Hill, Niki Mirshams, Timea Hodics, Linda S HynanAbstract:KEY POINTS: Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about Individual Variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large Individual Variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT: This study measured the Individual Variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large Individual Variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P < 0.01). Collectively, these findings demonstrated the presence of large Individual Variability of CA in older adults, and that, when measured in the posterior cerebral circulation, it is the higher rather than lower CA reactivity that is associated with WMH severity.
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Individual Variability of cerebral autoregulation, posterior cerebral circulation and white matter hyperintensity
The Journal of Physiology, 2016Co-Authors: Benjamin Y Tseng, Muhammad Ayaz Khan, Takashi Tarumi, Candace Hill, Niki Mirshams, Timea Hodics, Linda S Hynan, Rong ZhangAbstract:KEY POINTS: Cerebral autoregulation (CA) is a key mechanism to protect brain perfusion in the face of changes in arterial blood pressure, but little is known about Individual Variability of CA and its relationship to the presence of brain white matter hyperintensity (WMH) in older adults, a type of white matter lesion related to cerebral small vessel disease (SVD). This study demonstrated the presence of large Individual Variability of CA in healthy older adults during vasoactive drug-induced changes in arterial pressure assessed at the internal carotid and vertebral arteries. We also observed, unexpectedly, that it was the 'over-' rather than the 'less-reactive' CA measured at the vertebral artery that was associated with WMH severity. These findings challenge the traditional concept of CA and suggest that the presence of cerebral SVD, manifested as WMH, is associated with posterior brain hypoperfusion during acute increase in arterial pressure. ABSTRACT: This study measured the Individual Variability of static cerebral autoregulation (CA) and determined its associations with brain white matter hyperintensity (WMH) in older adults. Twenty-seven healthy older adults (13 females, 66 ± 6 years) underwent assessment of CA during steady-state changes in mean arterial pressure (MAP) induced by intravenous infusion of sodium nitroprusside (SNP) and phenylephrine. Cerebral blood flow (CBF) was measured using colour-coded duplex ultrasonography at the internal carotid (ICA) and vertebral arteries (VA). CA was quantified by a linear regression slope (CA slope) between percentage changes in cerebrovascular resistance (CVR = MAP/CBF) and MAP relative to baseline values. Periventricular and deep WMH volumes were measured with T2-weighted magnetic resonance imaging. MAP was reduced by -11 ± 7% during SNP, and increased by 21 ± 8% during phenylephrine infusion. CA demonstrated large Individual Variability with the CA slopes ranging from 0.37 to 2.20 at the ICA and from 0.17 to 3.18 at the VA; no differences in CA were found between the ICA and VA. CA slopes measured at the VA had positive correlations with the total and periventricular WMH volume (r = 0.55 and 0.59, P
