Introduction of magnetoencephalography to stereotactic techniques.

Magnetoencephalography (MEG), a noninvasive functional brain mapping technique, was used for preoperative localization of the sensorimotor cortex in patients harboring lesions involving these eloquent regions. Prior to surgery, MEG source locations were transferred onto high-resolution MRI pictures which were then used for preoperative evaluation, risk analysis, and planning. We have developed a process to transform the MEG-derived sensorimotor localization coordinates into the COMPASS stereotactic coordinate system.

Time resolved calcium microdomains and synaptic transmission.

The time course for the calcium entry that triggers release was studied at the squid giant synapse by imaging light emission from n-aequorin-J intracellularly injected into the presynaptic terminal. The imaging utilized a video system capable of acquiring 4000 frames per second. The results indicate that the calcium entry triggered by action potentials reaches a peak within 200 microseconds and has an overall duration of close to 800 microseconds, closely matching the duration of the presynaptic calcium current determined by voltage clamp results under similar conditions.

Different calcium channels mediate transmitter release evoked by transient or sustained depolarization at mammalian sympathetic ganglia.

We have compared the effect of calcium channel blockers on the potassium-evoked release of tritium-labeled acetylcholine and on preganglionic spike-evoked synaptic transmission in the rat superior cervical ganglion. Transmitter release at the nerve terminals is mediated by the influx of calcium through voltage-gated calcium channels. While four types of voltage-gated calcium channels (T, L, N and P) have been identified in neurons, it is not clear which may actually be involved in excitation-secretion coupling.

The inositol high-polyphosphate series blocks synaptic transmission by preventing vesicular fusion: a squid giant synapse study.

Presynaptic injection of inositol 1,3,4,5-tetraphosphate, inositol 1,3,4,5,6-pentakisphosphate, or inositol 1,2,3,4,5,6-hexakisphosphate--which we denote here the inositol high-polyphosphate series (IHPS)--is shown to block synaptic transmission when injected into the preterminal of the squid giant synapse. This effect is not produced by injection of inositol 1,4,5-trisphosphate. The synaptic block is characterized by a time course in the order of 15-45 min, depending on the injection site in the preterminal fiber; the fastest block occurs when the injection is made at the terminal release site.

High-resolution measurement of the time course of calcium-concentration microdomains at squid presynaptic terminals.

Transmitter release is considered to be a secretory event triggered by localized calcium influx which, by binding to a low-affinity Ca2+ site at the presynaptic active zone, initiates vesicular exocytosis (1-7). In previous experiments with aequorin-loaded presynaptic terminals we visualized, upon tetanic presynaptic stimulation, small points of light produced by calcium concentration microdomains of about 300 microM (5). These microdomains had a diameter of about 0.

Time-resolved imaging of Ca(2+)-dependent aequorin luminescence of microdomains and QEDs in synaptic preterminals.

Localized elevation of intracellular free calcium [Ca2+]i concentration serves as the trigger for a wide variety of physiological processes, e.g., neurotransmitter release at most chemical synapses (1-3).

Human oscillatory brain activity near 40 Hz coexists with cognitive temporal binding.

Spontaneous oscillatory electrical activity at a frequency near 40 Hz in the human brain and its reset by sensory stimulation have been proposed to be related to cognitive processing and to the temporal binding of sensory stimuli. These experiments were designed to test this hypothesis and to determine specifically whether the minimal interval required to identify separate auditory stimuli correlates with the reset of the 40-Hz magnetic signal. Auditory clicks were presented at varying times, while magnetic activity was recorded from awake human subjects.

Electrophysiology of globus pallidus neurons in vitro.

1. We investigated the electrical properties of globus pallidus neurons intracellularly using brain slices from adult guinea pigs. Three types of neurons were identified according to their intrinsic electrophysiological properties.

Non-lamellar propagation of entorhinal influences in the hippocampal formation: multiple electrode recordings in the isolated guinea pig brain in vitro.

Experiments were carried out to study the spatiotemporal organization of medial entorhinal inputs to the hippocampal system. They were performed in the isolated guinea pig brain in vitro preparation as it provides easy access to the medial entorhinal cortex (mEC) which is difficult to reach in vivo. Multiple simultaneous field potential recordings along the septotemporal extent of the dentate granular layer revealed that the mEC projection to the dentate gyrus (DG) is organized topographically.

Transmission at the squid giant synapse was blocked by tetanus toxin by affecting synaptobrevin, a vesicle-bound protein.

1. The effect of whole tetanus toxin (TeTX) and of its light chain (TeTX L-chain) on transmitter release was determined by presynaptic pressure-injection in the squid giant synapse. 2.

Serotonergic and cholinergic inhibition of mesopontine cholinergic neurons controlling REM sleep: an in vitro electrophysiological study.

Intracellular recordings were obtained from neurons of the laterodorsal tegmental and pedunculopontine tegmental nuclei in a brain-slice preparation. The action of exogenously applied 5-hydroxytryptamine and acetylcholine was studied on NADPH-diaphorase-labeled cells which contain nitric oxide synthase and are presumed to be cholinergic. Our results indicated that these cells were hyperpolarized by both 5-hydroxytryptamine and acetylcholine; the ionic mechanism of this inhibition was investigated using current and voltage clamp methods.

Neuromagnetic studies of the lip area of primary somatosensory cortex in humans: evidence for an oscillotopic organization.

Magnetic trigeminal somatosensory responses from human subjects were recorded using a 14-channel magnetoencephalographic system. Sensory stimuli comprising a 15-ms vibration at frequencies of 50 Hz, 150 Hz and 250 Hz were given at randomized interstimulus intervals. Using a single dipole model, the neuronal sources of the evoked responses were determined, and mapped onto magnetic resonance images of each subject.

IgG from amyotrophic lateral sclerosis patients increases current through P-type calcium channels in mammalian cerebellar Purkinje cells and in isolated channel protein in lipid bilayer.

The effect of the IgG from amyotrophic lateral sclerosis (ALS) patients was tested on the voltage-dependent barium currents (IBa) in mammalian dissociated Purkinje cells and in isolated P-type calcium channels in lipid bilayers. Whole cell clamp of Purkinje cells demonstrates that ALS IgG increases the amplitude of IBa without modifying their voltage kinetics. This increased IBa could be blocked by a purified nonpeptide toxin from Agelenopsis aperta venom (purified funnel-web spider toxin) or by a synthetic polyamine analog (synthetic funnel-web spider toxin) and by a peptide toxin from the same spider venom, omega-Aga-IVA.

On the cerebellum and motor learning.

A critical review of the role of the cerebellum in motor learning is presented. Specifically, the hypothesis that the climbing fibers that issue from the inferior olive serve to modify the responsiveness of cerebellar Purkinje cells is evaluated. It is concluded that there is no convincing evidence, at this time, to support the view that a long-term modification of Purkinje cell activity is either the basis of motor learning or an authentic mechanism of cerebellar function.

Anterior temporal language areas in patients with early onset of temporal lobe epilepsy.

Eighteen consecutive patients undergoing dominant temporal lobectomy underwent preoperative cortical stimulation for language localization. Patients with naming deficits on anterior (4.5 cm from the temporal pole) temporal lobe stimulation had earlier seizure onset vs those without such deficits (5.

Uniform olivocerebellar conduction time underlies Purkinje cell complex spike synchronicity in the rat cerebellum.

1. The issue of isochronicity of olivocerebellar fibre conduction time as a basis for synchronizing complex spike activity in cerebellar Purkinje cells has been addressed by latency measurement, multiple-electrode recording and Phaseolus vulgaris leucoagglutinin (PHA-L) tracing of climbing fibres in the adult rat. 2.

The isolated and perfused brain of the guinea-pig in vitro.

We describe here an isolated and perfused in vitro adult guinea-pig whole brain preparation which is an extension of the previously described in vitro brainstem-cerebellum preparation. Viability was tested by the analysis of trans-synaptic responses along the visual pathways following the electrical stimulation of the optic nerve or the optic radiations. The evoked field potentials were recorded in the dorsal lateral geniculate, the superior colliculus and the visual cortex.

Somatosensory cortical plasticity in adult humans revealed by magnetoencephalography.

Microelectrode recordings in adult mammals have clearly demonstrated that somatosensory cortical maps reorganize following peripheral nerve injuries and functional modifications; however, such reorganization has never been directly demonstrated in humans. Using magnetoencephalography, we have been able to demonstrate the somatotopic organization of the hand area in normal humans with high spatial precision. Somatosensory cortical plasticity was detected in two adults who were studied before and after surgical separation of webbed fingers (syndactyly).

Coherent 40-Hz oscillation characterizes dream state in humans.

Magnetic recording from five normal human adults demonstrates large 40-Hz coherent magnetic activity in the awake and in rapid-eye-movement (REM) sleep states that is very reduced during delta sleep (deep sleep characterized by delta waves in the electroencephalogram). This 40-Hz magnetic oscillation has been shown to be reset by sensory stimuli in the awake state. Such resetting is not observed during REM or delta sleep.