Showing papers by "Nicholas J. Strausfeld published in 1976"

Resolution of intraneuronal and transynaptic migration of cobalt in the insect visual and central nervous systems

Abstract: Conventional cobalt chloride procedures, using either diffusion into cut nerves or application via an electrode, can only incompletely resolve nerve cells for light microscopical observation Enhanced resolution can be obtained by the addition of small quantities of serum albumin to the cobalt chloride This allows sufficient contrast many nerve cells and enhances the details of thin fibres and their appendages That this should be possible is of cardinal importance for combined electrophysiological and structural studies The present account also illustrates that in Dipterous insects there are certain conditions where cobalt chloride will move from one neuron into another This movement is between functionally contiguous neurons and is here described from the visual system, with reference to electrophysiological studies that employ procion yellow identifications Transynaptically filled neurons are only faintly resoluble in whole mounts A block modification of the Timm's enhancement procedure is described which will reveal the finest details of neurons in thick sections and will also reveal nerve cells that have taken up minute quantities of CoCl2 after passage across at least two synapses These observations are discussed with reference to their implications and applications for electrophysiological mappings of structural pathways

A Historical Commentary

Abstract: Neurological sciences in the 19th and early part of the 20th century were dominated by researches on vertebrate, and in particular, mammalian brain. Very little scientific consideration was given to arthropod cerebral structures. The few investigations that were performed prior to 1885 dealt with overt brain structures and hardly considered behavioural phenomena that might be evoked by the neural architecture. To be fair, the size of the insect brain did not lend itself to the kinds of lesion experiments that were practised on Cephalopods (UexkUll, 1895) or, until much later, on vertebrates (Lashley, 1929), and the apparently simple structure of the intact insect brain lead to simplistic statements about its probable modes of action. Only the most obvious divisions of the cerebral ganglia, such as the olfactory lobes, optic lobes and the so-called mushroom bodies (corpes fungiformes, or corpora pedunculata which were discovered by Dujardin, 1850), were subject to speculation. To the early anatomists it was obvious that the first two regions were intimately concerned with the sensations of vision and olfaction (see the works of FlOgel, 1876 and 1878), and because of its prominence in social insects there was a certain penchant for describing the third region as a centre of intelligence or emotion (Dujardin, 1850; Leydig, 1864), a misconception that is even perpetrated in some modern text books of entomology.