The Threshold for Phosphenes is Lower in Migraine

Cephalalgia ◽  
2003 ◽  
Vol 23 (4) ◽  
pp. 258-263 ◽  
Author(s):  
SK Aurora ◽  
KMA Welch ◽  
F Al-Sayed
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Occipital Cortex ◽  
Logrank Test ◽  
Clinical Observations ◽  
Blinded Study ◽  
Visual Phenomena ◽  
Preliminary Study ◽  
The Difference ◽  
Normal Controls

We have reported a preliminary study confirming hyperexicitability of occipital cortex in migraine with aura (MwA) using transcranial magnetic stimulation (TMS). We have now completed a blinded study to investigate the occipital cortex in MwA and without aura (MwoA) compared with normal controls (NC) using TMS. TMS was performed using the Caldwell MES-10 stimulator. A circular coil 9.5 cm diameter was applied to the occipital scalp (7 cm above the inion). Stimulator intensity was increased in 10% increments until subjects reported visual phenomena or 100% intensity was reached. Stimulation intensity was then fine tuned to determine the threshold at which phosphenes were seen. Fisher's exact t-test and logrank test were used for statistical comparisons. Ten subjects with MwA and MwoA were compared to 10 NC. The difference in the proportion of subjects with phosphene generation was statistically significant (MwA 100%, MwoA 60% and NC 30%) [ P = 0.003]. The difference in threshold levels for phosphenes was also significant for MwA 42.8%, and controls 57.3% [ P = 0.0001]. There is a difference in threshold for excitability of occipital cortex in MwA and MwoA compared to NC. This is a direct neurophysiological correlate for clinical observations, which have inferred hyperexicitability of the occipital cortex in migraineurs.

Repetitive transcranial magnetic stimulation as treatment of poststroke depression: a preliminary study

2004 ◽  
Vol 55 (4) ◽  
pp. 398-405 ◽  
Author(s):  
Ricardo E Jorge ◽  
Robert G Robinson ◽  
Amane Tateno ◽  
Kenji Narushima ◽  
Laura Acion ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Repetitive Transcranial Magnetic Stimulation ◽  
Poststroke Depression ◽  
Preliminary Study

scholarly journals Spatio-temporally specific transcranial magnetic stimulation to test the locus of perceptual decision making in the human brain

2018 ◽  
Author(s):  
Bruce Luber ◽  
David C. Jangraw ◽  
Greg Appelbaum ◽  
Austin Harrison ◽  
Susan Hilbig ◽  
...  
Keyword(s):  
Decision Making ◽  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Performance Enhancement ◽  
Occipital Cortex ◽  
Stimulus Onset ◽  
Perceptual Decision Making ◽  
Perceptual Decision ◽  
Slow Reaction Time ◽  
Predictive Validation

AbstractPrevious research modeling EEG, fMRI and behavioral data has identified three spatially distributed brain networks that activate in temporal sequence, and are thought to enable perceptual decision-making during face-versus-car categorization. These studies have linked late activation (>300ms post stimulus onset) in the lateral occipital cortex (LOC) to object discrimination processes. We applied paired-pulse transcranial magnetic stimulation (ppTMS) to LOC at different temporal latencies with the specific prediction, based on these studies, that ppTMS beginning at 400ms after stimulus onset would slow reaction time (RT) performance. Thirteen healthy adults performed a two-alternative forced choice task selecting whether a car or face was present on each trial amidst visual noise pre-titrated to approximate 79% accuracy. ppTMS, with pulses separated by 50ms, was applied at one of five stimulus onset asynchronies: -200, 200, 400, 450, or 500ms, and a sixth no-stimulation condition. As predicted, TMS at 400ms resulted in significant slowing of RTs, providing causal evidence in support of LOC contribution to perceptual decision processing. In addition, TMS delivered at -200ms resulted in faster RTs, indicating early stimulation may result in performance enhancement. These findings build upon correlational EEG and fMRI observations and demonstrate the use of TMS in predictive validation of psychophysiological models.

scholarly journals Transcranial magnetic stimulation entrains alpha oscillatory activity in occipital cortex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong-Jun Lin ◽  
Lavanya Shukla ◽  
Laura Dugué ◽  
Antoni Valero-Cabré ◽  
Marisa Carrasco
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Cortical Excitability ◽  
Time Windows ◽  
Oscillation Amplitude ◽  
Occipital Cortex ◽  
Oscillatory Activity ◽  
Input Frequency ◽  
Oscillation Phase ◽  
Frequency Specificity

AbstractParieto-occipital alpha rhythms (8–12 Hz) underlie cortical excitability and influence visual performance. Whether the synchrony of intrinsic alpha rhythms in the occipital cortex can be entrained by transcranial magnetic stimulation (TMS) is an open question. We applied 4-pulse, 10-Hz rhythmic TMS to entrain intrinsic alpha oscillators targeting right V1/V2, and tested four predictions with concurrent electroencephalogram (EEG): (1) progressive enhancement of entrainment across time windows, (2) output frequency specificity, (3) dependence on the intrinsic oscillation phase, and (4) input frequency specificity to individual alpha frequency (IAF) in the neural signatures. Two control conditions with an equal number of pulses and duration were arrhythmic-active and rhythmic-sham stimulation. The results confirmed the first three predictions. Rhythmic TMS bursts significantly entrained local neural activity. Near the stimulation site, evoked oscillation amplitude and inter-trial phase coherence (ITPC) were increased for 2 and 3 cycles, respectively, after the last TMS pulse. Critically, ITPC following entrainment positively correlated with IAF rather than with the degree of similarity between IAF and the input frequency (10 Hz). Thus, we entrained alpha-band activity in occipital cortex for ~ 3 cycles (~ 300 ms), and IAF predicts the strength of entrained occipital alpha phase synchrony indexed by ITPC.

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