Effect of coil orientation on strength-duration time constant and I-wave activation with controllable pulse parameter transcranial magnetic stimulation
D'Ostilio, Kevin ; ; et al
in Clinical Neurophysiology (in press)
Objective: To compare the strength-duration (S-D) time constants of motor cortex structures activated by current pulses oriented posterior-anterior (PA) or anterior-posterior (AP) across the central ... [more ▼]
Objective: To compare the strength-duration (S-D) time constants of motor cortex structures activated by current pulses oriented posterior-anterior (PA) or anterior-posterior (AP) across the central sulcus. Methods: Motor threshold and input–output curve, along with motor evoked potential (MEP) latencies, of first dorsal interosseus were determined at pulse widths of 30, 60, and 120 μs using a controllable pulse parameter (cTMS) device, with the coil oriented PA or AP. These were used to estimate the S-D time constant and we compared with data for responses evoked by cTMS of the ulnar nerve at the elbow. Results: The S-D time constant with PA was shorter than for AP stimulation (230.9 ± 97.2 vs. 294.2 ± 90.9 us; p<0.001). These values were similar to those calculated after stimulation of ulnar nerve (197 ± 47us). MEP latencies to AP, but not PA stimulation were affected by pulse width, showing longer latencies following short duration stimuli. Conclusion: PA and AP stimuli appear to activate the axons of neurons with different time constants. Short duration AP pulses are more selective than longer pulses in recruiting longer latency corticospinal output. [less ▲]Detailed reference viewed: 10 (1 ULg)
Neurophysiology of hypnosis
VANHAUDENHUYSE, Audrey ; Laureys, Steven ; Faymonville, Marie-Elisabeth
in Clinical Neurophysiology (2014), 44
We here review behavioral, neuroimaging and electrophysiological studies of hypnosis as a state, as well as hypnosis as a tool to modulate brain responses to painful stimulations. Studies have shown that ... [more ▼]
We here review behavioral, neuroimaging and electrophysiological studies of hypnosis as a state, as well as hypnosis as a tool to modulate brain responses to painful stimulations. Studies have shown that hypnotic processes modify internal (self awareness) as well as external (environmental awareness) brain networks. Brain mechanisms underlying the modulation of pain perception under hypnotic conditions involve cortical as well as subcortical areas including anterior cingulate and prefrontal cortices, basal ganglia and thalami. Combined with local anesthesia and conscious sedation in patients undergoing surgery, hypnosis is associated with improved peri- and postoperative comfort of patients and surgeons. Finally, hypnosis can be considered as a useful analogue for simulating conversion and dissociation symptoms in healthy subjects, permitting better characterization of these challenging disorders by producing clinically similar experiences. [less ▲]Detailed reference viewed: 56 (7 ULg)
Probing command following in patients with disorders of consciousness using a brain-computer interface.
; Noirhomme, Quentin ; et al
in Clinical Neurophysiology (2013), 124(1), 101-6
OBJECTIVE: To determine if brain-computer interfaces (BCIs) could serve as supportive tools for detecting consciousness in patients with disorders of consciousness by detecting response to command and ... [more ▼]
OBJECTIVE: To determine if brain-computer interfaces (BCIs) could serve as supportive tools for detecting consciousness in patients with disorders of consciousness by detecting response to command and communication. METHODS: We tested a 4-choice auditory oddball EEG-BCI paradigm on 16 healthy subjects and 18 patients in a vegetative state/unresponsive wakefulness syndrome, in a minimally conscious state (MCS), and in locked-in syndrome (LIS). Subjects were exposed to 4 training trials and 10 -12 questions. RESULTS: Thirteen healthy subjects and one LIS patient were able to communicate using the BCI. Four of those did not present with a P3. One MCS patient showed command following with the BCI while no behavioral response could be detected at bedside. All other patients did not show any response to command and could not communicate with the BCI. CONCLUSION: The present study provides evidence that EEG based BCI can detect command following in patients with altered states of consciousness and functional communication in patients with locked-in syndrome. However, BCI approaches have to be simplified to increase sensitivity. SIGNIFICANCE: For some patients without any clinical sign of consciousness, a BCI might bear the potential to employ a "yes-no" spelling device offering the hope of functional interactive communication. [less ▲]Detailed reference viewed: 184 (18 ULg)
Motor neuron disorders : novel electrophysiologic approach (MUFDEC protocol)
WANG, François-Charles ; ; WANG, Pascale et al
in Clinical Neurophysiology (2009), Suppl(Vol 60), 143-152Detailed reference viewed: 17 (4 ULg)
Diagnosing entrapment neuropathies: probes and magnets instead of electrodes and needles?
MAERTENS DE NOORDHOUT, Alain
in Clinical Neurophysiology (2006), 117(3), 484-5Detailed reference viewed: 7 (2 ULg)
Post-stroke reorganization of hand motor area : a 1-year prospective follow-up with focal transcranial magnetic stimulation
DELVAUX, Valérie ; ; GERARD, Pascale et al
in Clinical Neurophysiology (2003), 114(Issue 4), 1217-1225Detailed reference viewed: 19 (5 ULg)
Evoked potentials and transcranial magnetic stimulation in migraine: published data and viewpoint on their pathophysiologic significance.
Schoenen, Jean ; ; et al
in Clinical Neurophysiology (2003), 114(6), 955-72
Migraine is a disorder in which central nervous sytem dysfunction might play a pivotal role. Electroneurophysiology seems thus particularly suited to study its pathophysiology. We have extensively ... [more ▼]
Migraine is a disorder in which central nervous sytem dysfunction might play a pivotal role. Electroneurophysiology seems thus particularly suited to study its pathophysiology. We have extensively reviewed evoked potential and transcranial magnetic stimulation studies performed in migraineurs in order to identify their pathophysiologic significance. Publications available to us were completed by a Medline search. Retrieved and personal data were compared with respect to methodology and interpreted according to present knowledge on cortical information processing. Results are in part contradictory which appears to be method-, patient- and disease- related. Nonetheless, both evoked potential and transcranial magnetic stimulation studies demonstrate that the cerebral cortex, and possibly subcortical structures, are dysfunctioning interictally in both migraine with and without aura. These electrophysiologic abnormalities tend to normalise just before and during an attack and some of them seem to have a clear familial and predisposing character. Besides the studies of magnetophosphenes which have yielded contrasting results, chiefly because the method is not sufficiently reliable, most recent electrophysiologic investigations of cortical activities in migraine favour deficient habituation and decreased preactivation cortical excitability as the predominant interictal dysfunctions. We propose that the former is a consequence of the latter and that it could favour both interictal cognitive disturbances as well as a cerebral metabolic disequilibrium that may play a role in migraine pathogenesis. To summarize, electrophysiologic studies demonstrate in migraine between attacks a cortical, and possibly subcortical, dysfunction of which the hallmark is deficient habituation. [less ▲]Detailed reference viewed: 23 (2 ULg)
Single motor axon conduction velocities of human upper and lower limb motor units. A study with transcranial electrical stimulation
; GERARD, Pascale ; De Pasqua, Victor et al
in Clinical Neurophysiology (2002), 113(2), 284-291
OBJECTIVES: To calculate conduction velocities (CV) of single motor axons innervating hand, forearm and leg muscles, weak anodal electrical transcranial stimuli were used and single motor unit potentials ... [more ▼]
OBJECTIVES: To calculate conduction velocities (CV) of single motor axons innervating hand, forearm and leg muscles, weak anodal electrical transcranial stimuli were used and single motor unit potentials were recorded in 17 normal subjects. METHODS: The central motor conduction time and neuromuscular transmission delay were subtracted from the latency of unit response to cortical stimulation and single motor axon CV were calculated. RESULTS: In extensor indicis proprius (EIP) units, CV ranged from 30.3 to 76.1m/s (mean: 51.3 +/- 7.1m/s, 139 units). In first dorsal interosseous (FDI), they ranged from 45.1 to 66.2m/s (mean: 54.6 +/- 2.6m/s, 88 units). In tibialis anterior (TA), velocities ranged from 27.8 to 55.9m/s (mean: 41.3 +/- 7.5m/s, 123 units). In FDI units, velocities were compared with those obtained with the F-wave method (range: 50.3-64.5m/s, mean: 58.1 +/- 2.0m/s). CONCLUSIONS: Compared with previously published values, the present method gives better access to slow-conducting units, first recruited by transcranial stimulation and voluntary effort. The spectrum of individual CV was much broader for EIP and TA than for FDI. A linear decline of maximal CV with age was observed, while minimal CV were not affected, suggesting that aging causes a selective loss of the fastest-conducting units. [less ▲]Detailed reference viewed: 21 (5 ULg)
Electrophysiological study of central mechanisms of fatigue in multiple sclerosis.
DELVAUX, Valérie ; ; et al
in Clinical Neurophysiology (2000, August), 111(Suppl. 1), 12316-05Detailed reference viewed: 16 (1 ULg)
Post-stroke reorganization of hand motor area: a 1 year longitudinal study with focal transcranial magnetic stimulation.
DELVAUX, Valérie ; ; DE PASQUA, Victor et al
in Clinical Neurophysiology (2000), 111(Suppl. 1), 12517-06Detailed reference viewed: 34 (5 ULg)
Ipsilateral motor responses to focal TMS in normal man and stroke patients.
; DELVAUX, Valérie ; Delwaide, Paul et al
in Clinical Neurophysiology (2000), 111(Suppl. 1), 11512-05Detailed reference viewed: 24 (4 ULg)
Comparison of visual and auditory evoked cortical potentials in migraine patients between attacks.
; ; et al
in Clinical Neurophysiology (2000), 111(6), 1124-9
OBJECTIVE: As both habituation of pattern reversal visual evoked potentials (PR-VEP) (Schoenen J, Wang W, Albert A, Delwaide PJ. Potentiation instead of habituation characterizes visual evoked potentials ... [more ▼]
OBJECTIVE: As both habituation of pattern reversal visual evoked potentials (PR-VEP) (Schoenen J, Wang W, Albert A, Delwaide PJ. Potentiation instead of habituation characterizes visual evoked potentials in migraine patients between attacks. Eur J Neurol 1995;2:115-122) and intensity dependence of auditory evoked cortical potentials (IDAP) (Wang W, Timsit-Berthier M, Schoenen J. Intensity dependence of auditory evoked potentials in migraine: an indication of cortical potentiation and low serotonergic neurotransmission? Neurology 1996;46:1404-1409) were found abnormal in migraine between attacks, we have searched for intraindividual correlations between both tests in 59 migraine patients (22 with aura [MA], 37 without aura [MO]) and in 23 healthy volunteers (HV). METHODS: Amplitude change of the PR-VEP N1-P1 was measured between the 1st and 5th block of 50 sequential averagings during continuous stimulation at 3.1 Hz. IDAP was computed from N1-P2 amplitudes of 100 averagings during stimulations at 40, 50, 60 and 70 dB SL. Amplitude-stimulus intensity function (ASF) slopes and amplitude changes between 40 and 70 dB were calculated. MO and MA differed from HV in PR-VEP amplitude change (P=0.007) and IDAP slope (P = 0.0004). RESULTS: There was no significant correlation between VEP amplitude changes and IDAP slopes, nor between the latter two and attack frequency or disease duration. A negative correlation was found between the amplitude of the first block of averaged responses and potentiation of VEP in all subject groups (P = 0.03) as well as between the amplitude of the auditory evoked potential, at 40 dB, and the percentage of amplitude increase between 40 and 70 dB in MO (P = 0.004) and MA (P = 0.007). ASF slopes and 40 dB amplitudes were significantly correlated only in the MA group (P = 0.002). These results confirm the interictal deficit of habituation in cortical processing of repetitive visual and auditory information in migraine. Since there is no intraindividual correlation between the cortical responses to these sensory modalities they are complementary tools for the study of migraine and may help to identify subgroups of patients with distinct pathophysiological mechanisms. CONCLUSIONS: The strong negative correlation between the initial amplitude of evoked potentials and their amplitude increase during subsequent averaging confirms that the response potentiation in migraine is likely to be due to a reduced preactivation level of sensory cortices. [less ▲]Detailed reference viewed: 37 (1 ULg)