Denise Albe-Fessard

A study of an ascending nigro-caudate pathway.

Abstract 1. 1. Former electrophysiological investigations have shown that, following substantia nigra (SN) stimulation, responses could be recorded in the caudate nucleus (n Cd). In order to analyse the characteristics of these responses, macro- and micro-electrode records were taken from 116 cats, 46 of them being maintained under local analgesia after an operating phase with volatile anaesthetics; in 47 volatile anaesthesia was prolonged, and 23 were anaesthetized with chloralose or barbiturate. 2. 2. It was shown that such n Cd responses persist after degeneration of the descending cortical pathways following a broad anterior cortical ablation performed 15 days earlier. 3. 3. Micro-electrodes in the head of the n Cd reveal two types of unit. They exhibit opposite reactions when SN is stimulated. Those detected through their spontaneous firing most often have their activity depressed. The other units can only be detected through their excitatory responses to nigral stimulation. The characteristics of 419 of these latter neurones were studied in detail. 4. 4. These excited neurones respond after a relatively stable long latency (16.8±5 msec, in cats under local analgesia). They follow each stimulus of short trains of shocks (100–320/sec). These responses are suppressed by barbiturate anaesthesia. Their orthodromic origin was demonstrated by the collision technique, extra spikes having been provoked by repetitive stimulation or by electrophoretic application of excitatory amino acids. 5. 5. A study of the organization of the nigro-caudate inflow has shown that responsive units are driven by stimulating electrodes placed in the posterior as well as the anterior parts of SN. The responsive units are predominantly found in the medial two-thirds of the head of caudate nucleus. No significant difference in latency can be correlated with differences in unit localization. Given the mean value of the latencies and the distance between the stimulating electrode and the active units, the average conduction velocity is 0.90±0.27 m/sec. 6. 6. Stimuli applied to the periphery and to different central regions were mostly unable to drive the cells responding to SN stimulation. Internal capsule, ventro-medial tegmental areas and n Cd were the only ones to be efficacious.

Labelling of cells in the medulla oblongata and the spinal cord of the monkey after injections of horseradish peroxidase in the thalamus.

Injections of horseradish peroxidase were performed in macaque monkeys in the intralaminar and the ventroposterior thalamic region, respectively. Following injection in the intralaminar region labelled cells were present in the marginal zone both in the spinal trigeminal nuclues and in the spinal dorsal horn. The same areas contained labelled cells after injections in the ventroposterior thalamic region, but in such experiments labelled cells were also present in the lamina IV-V region of the spinal cord, in the gracile and main cuneate nuclei and in the external cuneate nucleus. Thus, the marginal zone of the spinal cord appears to project to at least two of the thalamic regions receiving spinothalamic fibres in the monkey.

Double labelling of branched neurons in the central nervous system of the rat by retrograde axonal transport of horseradish peroxidase and iron dextran complex

The retrograde axonal transport of an iron-dextran complex leads to a labelling of neural cell bodies in the central nervous system (CNS) of the rat. This tracer and horseradish peroxidase (HRP) can both be demonstrated histochemically in same cell bodies of intralaminar thalamic neurons in the central lateral nucleus, after injection of iron-dextran in the striatum and injection of HRP in the motor cortex. This is made possible by processing the sections first for HRP and then for ferric ions by Perls reaction. This method allows an accurate demonstration of divergent axonal projections and is compatible with cytoarchitectonic studies on the same sections.

Projections of medial thalamic nuclei to putamen and cerebral frontal cortex in the cat

Abstract Projections of cells of the nucleus centrum medianum (CM) and the nucleus centralis lateralis (CL) in the cat have been studied by observing antidromic invasion of these cells on stimulation of putamen and pericruciate cortex. Cells in CM project to the putamen. Cells in CL and the anterior tip of CM project to the pericruciate cortex and either to or through the putamen.

Evidence for a projection to the thalamus from the external cuneate nucleus in the monkey.

Abstract Following injections of horseradish peroxidase in the ventroposterior nuclei of the thalamus, labelled cells were present in the contralateral external cuneate nucleus at all rostrocaudal levels of the nucleus. The results demonstrate the existence of a hitherto unknown projection from the external cuneate nucleus to the thalamus in the macaque.

Electrophysiological methods for the identification of thalamic nuclei

SummaryTo increase the precision of the anatomical localization in stereotaxic neurosurgery, three techniques are now in common use to identify the thalamic nuclei: electrophysiological recording, local stimulation, reversible local blockade. A comparison is made between the results obtained by these three methods.ZusammenfassungDrei Techniken werden benutzt, um bei stereotaktischen Eingriffen am Thalamus die anatomische Lokalisation noch zuverlässiger zu präzisieren: Elektrophysiologische Ableitungen, lokale Reizung und reversible lokale Blockierung. In der vorliegenden Arbeit werden die Resultate dieser drei Methoden miteinander kritisch verglichen.

Depressive effect of high frequency peripheral conditioning stimulation upon the nociceptive component of the human blink reflex. Lack of naloxone effect

High frequency (100 Hz) low intensity (2 mA) peripheral conditioning stimulation of either segmental or heterosegmental cutaneous nerves induced non-naloxone-reversible depression of the nociceptive component of the human blink reflex. Electrophysiological studies suggest that this depression is due to a local synaptic inhibitory mechanism involving convergence interactions between several cutaneous afferents onto a same internuncial pool in the trigemino-facial path.