Experimental Neurology By Prof Paul Glees Pp xii + 532 (Oxford: Clarendon Press; London: Oxford University Press, 1961) 75s net

The Nervous System

Evolution of Nervous Control from Primitive Organisms to Man A Symposium organized by the Section on Medical Sciences of the American Association for the Advancement of Science, and presented at the New York Meeting on December 29–30, 1956. Edited by Allan D. Bass. Pp. vii + 231. (Washington, D.C.: American Association for the Advancement of Science; London: Bailey Bros. and Swinfen, Ltd., 1959.) 52s.

The Central Nervous System

We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework of statistical mechanics. Examples of such active units in complex physico-chemical and biological systems are chemically powered nano-rods, localized patterns in reaction-diffusion system, motile cells or macroscopic animals. Based on the description of individual motion of point-like active particles by stochastic differential equations, we discuss different velocity-dependent friction functions, the impact of various types of fluctuations and calculate characteristic observables such as stationary velocity distributions or diffusion coefficients. Finally, we consider not only the free and confined individual active dynamics but also different types of interaction between active particles. The resulting collective dynamical behavior of large assemblies and aggregates of active units is discussed and an overview over some recent results on spatiotemporal pattern formation in such systems is given.

Active Brownian Particles. From Individual to Collective Stochastic Dynamics

The embryonic ventricular zone (VZ) of the cerebral cortex contains migrating neurons, radial glial cells, and a large population of cycling progenitor cells that generate newborn neurons. The latter two cell classes have been assumed for some time to be distinct in both function and anatomy, but the cellular anatomy of the progenitor cell type has remained poorly defined. Several recent reports have raised doubts about the distinction between radial glial and precursor cells by demonstrating that radial glial cells are themselves neuronal progenitor cells (Malatesta et al., 2000; Hartfuss et al., 2001; Miyata et al., 2001; Noctor et al., 2001). This discovery raises the possibility that radial glia and the population of VZ progenitor cells may be one anatomical and functional cell class. Such a hypothesis predicts that throughout neurogenesis almost all mitotically active VZ cells and a substantial percentage of VZ cells overall are radial glia. We have therefore used various anatomical, immunohistochemical, and electrophysiological techniques to test these predictions. Our data demonstrate that the majority of VZ cells, and nearly all mitotically active VZ cells during neurogenesis, both have radial glial morphology and express radial glial markers. In addition, intracellular dye filling of electrophysiologically characterized progenitor cells in the VZ demonstrates that these cells have the morphology of radial glia. Because the vast majority cycling cells in the cortical VZ have characteristics of radial glia, the radial glial precursor cell may be responsible for both the production of newborn neurons and the guidance of daughter neurons to their destinations in the developing cortex.

https://www.jneurosci.org/content/jneuro/22/8/3161.full.pdf

Dividing precursor cells of the embryonic cortical ventricular zone have morphological and molecular characteristics of radial glia.

Introduction: Past, Present and Potential Recording Evoked Potentials: Means to an End Frequency-Domain: Music of the Hemispheres Finding Sources: Forwards and Backwards Sounds to Charm the Brain Interpreting the Waveforms: Time and Uncertainty Electrocochleography: From Song to Synapse Auditory Brainstem Responses: Peaks Along the Way Middle Latency Responses - The Brain and the Brawn Auditory Steady State and Following Responses: Dancing to the Rhythms Late Auditory Evoked Potentials: Changing the Things Which Are Endogenous Auditory Evoked Potentials: Attention Must Be Paid Infant Hearing Assessment: Opening Ears Neurotology and Neurology: From Cochlea to Cortex Auditory Neuropathy: When Time is Broke Cochlear Implants: Body Electric Concluding Comments: Beginning to Live

Human Auditory Evoked Potentials

If exposed to bulk water flow, fish lateral line afferents respond only to flow fluctuations (AC) and not to the steady (DC) component of the flow. Consequently, a single lateral line afferent can encode neither bulk flow direction nor velocity. It is possible, however, for a fish to obtain bulk flow information using multiple afferents that respond only to flow fluctuations. We show by means of particle image velocimetry that, if a flow contains fluctuations, these fluctuations propagate with the flow. A cross-correlation of water motion measured at an upstream point with that at a downstream point can then provide information about flow velocity and flow direction. In this study, we recorded from pairs of primary lateral line afferents while a fish was exposed to either bulk water flow, or to the water motion caused by a moving object. We confirm that lateral line afferents responded to the flow fluctuations and not to the DC component of the flow, and that responses of many fiber pairs were highly correlated, if they were time-shifted to correct for gross flow velocity and gross flow direction. To prove that a cross-correlation mechanism can be used to retrieve the information about gross flow velocity and direction, we measured the flow-induced bending motions of two flexible micropillars separated in a downstream direction. A cross-correlation of the bending motions of these micropillars did indeed produce an accurate estimate of the velocity vector along the direction of the micropillars.

https://www.jneurosci.org/content/jneuro/28/17/4479.full.pdf

Measuring flow velocity and flow direction by spatial and temporal analysis of flow fluctuations.

Fish use the lateral line system for prey detection, predator avoidance, schooling behavior, intraspecific communication and spatial orientation. In addition the lateral line may be important for station holding and for the detection of the hydrodynamic trails (vortex streets) generated by swimming fish. We investigated the responses of anterior lateral line nerve fibers of goldfish, Carassius auratus, to unidirectional water flow (10 cm s−1) and to running water that contained a Karman vortex street. Compared to still water conditions, both unidirectional water flow and Karman vortex streets caused a similar increase in the discharge rate of anterior lateral line nerve fibers. If exposed to a Karman vortex street, the amplitude of spike train frequency spectra increased at the vortex shedding frequency. This increase was especially pronounced if the fish intercepted the edge of a Karman vortex street. Our data show that the vortex shedding frequency can be retrieved from the responses of anterior lateral line nerve fibers.

Kármán vortex street detection by the lateral line.

Behavior of Animals with Passive, Low-Frequency Electrosensory Systems

The ability of Rhodnius prolixus (Hemiptera; Reduviidae) to approach a thermal source solely by its infrared radiation

The temporal envelope of speech is an important cue contributing to speech intelligibility. Theories about the neural foundations of speech perception postulate that the left and right auditory cortices are functionally specialized in analyzing speech envelope information at different time scales: the right hemisphere is thought to be specialized in processing syllable rate modulations, whereas a bilateral or left hemispheric specialization is assumed for phoneme rate modulations. Recently, it has been found that this functional hemispheric asymmetry is different in individuals with language-related disorders such as dyslexia. Most studies were, however, performed in adults and school-aged children, and only a little is known about how neural auditory processing at these specific rates manifests and develops in very young children before reading acquisition. Yet, studying hemispheric specialization for processing syllable and phoneme rate modulations in preliterate children may reveal early neural markers for dyslexia. In the present study, human cortical evoked potentials to syllable and phoneme rate modulations were measured in 5-year-old children at high and low hereditary risk for dyslexia. The results demonstrate a right hemispheric preference for processing syllable rate modulations and a symmetric pattern for phoneme rate modulations, regardless of hereditary risk for dyslexia. These results suggest that, while hemispheric specialization for processing syllable rate modulations seems to be mature in prereading children, hemispheric specialization for phoneme rate modulation processing may still be developing. These findings could have important implications for the development of phonological and reading skills.

https://www.jneurosci.org/content/jneuro/34/4/1523.full.pdf

Michael Hofmann

Papers

Measuring flow velocity and flow direction by spatial and temporal analysis of flow fluctuations.

Kármán vortex street detection by the lateral line.

Behavior of Animals with Passive, Low-Frequency Electrosensory Systems

The ability of Rhodnius prolixus (Hemiptera; Reduviidae) to approach a thermal source solely by its infrared radiation

Hemispheric Asymmetry in Auditory Processing of Speech Envelope Modulations in Prereading Children