ABSTRACT
In 20 subjects the supraorbital nerve was stimulated and R1 recorded from electrodes placed over the ipsilateral orbicularis oculi muscle and from locations Fz, F8, F7, Cz, C6, C5, Pz, T4, and T3 on the scalp. The latter were referred either to an extracranial electrode or to Fz. In five subjects an artificial dipole was set at three different positions on the eyebrow and records were taken from the same derivations on the scalp to study the distribution of fields of known intensity originating from known locations. It was found that R1 could be easily detected from all scalp locations. According to its scalp distribution, three patterns were identified, which matched those of the artificial dipole. Conversely from what had been believed by previous authors, the amplitude of R1 could be larger on the contralateral scalp, according to the reference used or to the location of its origin. Therefore, it is remarked that larger amplitude contralateral to the stimulus cannot anymore be considered an exclusive feature of responses arising from the cortex. The evidence we have provided recommends a highly cautious approach in interpreting results describing trigeminal scalp responses in the latency range of R1.
Subject(s)
Blinking/physiology , Brain Mapping , Cerebral Cortex/physiology , Electroencephalography , Adult , Evoked Potentials, Somatosensory/physiology , Female , Humans , Male , Reaction Time/physiology , Reference Values , Trigeminal Nerve/physiologySubject(s)
Cranial Nerve Diseases/chemically induced , Cranial Nerve Diseases/physiopathology , Trichloroethylene/adverse effects , Trigeminal Nerve/physiopathology , Adult , Evoked Potentials , Humans , Male , Neural Conduction , Sensation Disorders/chemically induced , Sensation Disorders/physiopathologyABSTRACT
The R1 component of the blink reflex was evoked by stimulation of the left supraorbital and infraorbital nerves in 10 subjects. In addition, an artificial dipole was placed over the left eyebrow, in order to simulate the occurrence of the R1 component of the blink reflex. These electrical events were recorded at scalp locations Fz, F8, F7, C6, C5, referred either to Cv7 (seventh cervical vertebra) or to Fz. It was found that the blink R1 and the field of the artificial dipole had similar behaviour across the scalp; larger amplitudes were recorded ipsilateral to the stimulus from derivations referred to Cv7, but when referred to Fz larger contralateral amplitudes were measured. In the latter condition, the scalp-recorded R1 shows similar amplitude behaviour to electrical events originating from the cortex and hence its appearance may be deceiving.
Subject(s)
Blinking/physiology , Brain/physiology , Evoked Potentials/physiology , Trigeminal Nerve/physiology , Electric Stimulation , Electroencephalography , Humans , Reaction Time/physiologyABSTRACT
A novel calcium entry blocker, nicardipine, has been tested using a dosage of 20 mg twice a day against placebo on 30 patients suffering from migraine without aura, according to a double-blind, cross-over design; overall duration of the study was four months (two with nicardipine and two with placebo). Migraine parameters such as monthly frequency, mean intensity and mean duration of attacks were monitored. Two indexes were also calculated: index A (monthly frequency x mean intensity) and index B (monthly frequency x mean intensity x mean duration). All the parameters considered and the two indexes showed a marked and significant improvement after nicardipine treatment in comparison to both placebo and pre-study scores. Detailed analysis of the cross-over results showed that improvement obtained with nicardipine lasted some time after the drug was discontinued. Nicardipine did not alter the blood and attention tests performed and caused few side effects.
