Magnetic fields associated with spreading depression in anaesthetised rabbits.

Magnetic fields were measured with SQUID magnetometry outside the skull of anaesthetised rabbits during initiation and propagation of spreading depression (SD) in the cortex. Slowly changing fields (up to 1.4 pT) were observed during the propagation phase, from 4-8.5 min after initiation of SD with KCl application, with maxima at about 6 min. The peak amplitude of the equivalent net dipole generators in the brain was ca. 28 microA.mm, substantially less than previously observed with SD in vitro, but large enough that similar signals might be detectable in man.

Event-related slow potentials and associated catecholamine function in migraine.

Plasma norepinephrine and dopamine and event-related slow potentials were measured at menses and ovulation in migraine with and without aura relative to normal subjects. The results indicated that at menses, but not ovulation, plasma dopamine was increased and norepinephrine was decreased relative to normal. This catecholamine imbalance was greater in migraine without aura than in migraine with aura. Conversely, event-related slow potentials measured over the posterior cortex at ovulation but not at the menses was altered relative to normal. Early epoch negativity was reduced in migraine with aura, whereas late epoch negativity was reduced in migraine without aura. The results suggested that (a) migraine without aura may involve dynamic shifts in the function of both norepinephrine and dopamine responsive neurons; (b) pathophysiology of migraine with aura is less dependent on catecholamine imbalance (norepinephrine alone affected); (c) these pathophysiological mechanisms are most prevalent in or restricted to posterior cortical regions but may be modulated by brainstem mechanisms.

Ovarian steroid levels in migraine with and without aura.

Radioimmunoassays were used to measure interictal levels of ovarian steroids (oestradiol, total oestrogens and progesterone) in migraine patients at the onset of menses and coincident with the luteinizing hormone surge preceding ovulation. Results of these verified biochemically-contrasting points of the ovarian cycle were used to compare 13 migraine patients without aura and 6 migraine patients with aura with 17 non-migraine women. No group differences were found for physiological basal levels of ovarian steroids measured at menses. Preceding ovulation elevation in oestradiol levels relative to normal was found in migraine patients with aura but not in migraine patients without aura. These results suggest that a variation in oestradiol levels is an important factor in the different clinical expressions of migraine.

Magnetoencephalographic studies of migraine.

We report for the first time the detection by magnetoencephalography (MEG) of signals observable in migraine patients during headache, but not in controls. These signals consisted of three features: suppression of spontaneous cortical activity, long duration field changes, and large amplitude waves (LAW) of several seconds duration. LAW were also seen during the interictal period. We discuss the possible relationship of these signals to spreading depression (SD), and why the LAW have not been observed in previous studies of SD.

Cerebral control of directed visual attention and orienting saccades.

The object of this experiment was to identify the contribution of the frontal and parietal lobes to the control of visual attention and voluntary saccades. A symbolic spatial cue (arrow) was used to indicate validly or invalidly the location of a visual target located to the left or right of the cue. Manual reaction time and reaction time to initiate a saccade to the target were measured. Patients with damage to the left frontal lobe (n = 6), right frontal lobe (n = 7) and right parietal lobe (n = 7) were compared with normal control subjects (n = 20). A sex difference was found for the right cerebral hemisphere patients in the manual reaction time data. Right parietal males and right frontal females showed an overall elevation in manual reaction time, reflecting an inability to maintain a normal level of visual arousal and/or motor activation. Conversely, right frontal males and right parietal females were not influenced significantly by cue validity, suggesting that they were unable to direct visual attention in a covert manner. All subjects showed a normal effect of cue validity on saccade reaction time. Thus the cortical areas studied do not appear to be necessary for directing visual attention with a saccade. Cue validity, however, affected saccade amplitude, especially in the left visual field of patients with right hemisphere damage. The cue validity effect depended both on the sex of the subject and the anterior/posterior location of damage in the right hemisphere. Damage to the right frontal lobe resulted in an 'under' reaction to the spatial cues, especially in the male patients. Saccades were smaller than normal following the valid cues, but larger than normal following the invalid cues. The effect was opposite following damage to the right parietal lobe. In this case, saccade amplitude reflected an 'over' reaction to the spatial cues, especially in the female patients. Saccades were larger than normal following valid cues and smaller than normal following invalid cues.

Platelet norepinephrine and serotonin balance in migraine.

Platelet serotonin (5 hydroxytryptamine, 5-HT) and norepinephrine (NE) were measured in common and classic migraine patients and healthy controls. Common migraine sufferers had high NE levels and a low 5-HT/NE ratio. Classic migraine patients had a high 5-HT level and a high 5-HT/NE ratio. The data suggest disparate NE and 5-HT metabolism between common and classic migraine.

Platelet catecholamines in migraine.

We measured platelet levels of norepinephrine (NE), epinephrine (E), and dopamine (DA) in migraine patients. Platelet NE was selectively increased in common migraine. This is attributed to platelet dense body hyposecretion.

Effects of kainic acid and radiofrequency lesions of the pulvinar on visual discrimination in the monkey.

Monkeys with thermocoagulation or kainic acid lesions of the pulvinar and unoperated control monkeys were tested in two tasks: pattern discrimination retention and color discrimination learning in which the stimuli were located at the response sites or were separated spatially from them (S-R separation). The monkeys with kainic acid pulvinar lesions were mildly impaired in retention of the pattern discrimination, but were unimpaired in the color discrimination tasks with or without the S-R separation. The monkeys with thermocoagulation lesions, like monkeys with superior colliculus lesions in a prior study, were severely impaired in performing one of the color discrimination tasks with S-R separation. These findings suggest that: (a) the inferior pulvinar, unlike the superior colliculus, does not contribute to the performance of discriminations involving S-R separation; and (b) corticotectal projections traversing the pulvinar and destroyed by the thermocoagulation lesions are crucial to the performance of discriminations involving S-R separation. The results of an earlier experiment also suggested that interruption of corticotectal fibers passing through the pulvinar impairs performance in another task sensitive to superior colliculus lesions--spatial localization of light flashes. Thus, corticotectal projections may be crucial for the contribution of the colliculus to performance in a variety of visual tasks.