Neff Contributions to Sensory Physiology

Volume 8
1. Auflage 2013
ISBN: 978-1-4831-9161-4
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 214 Seiten

Contributions to Sensory Physiology, Volume 8 is a collection of scientific essays that resulted from experiments made in the field of sensory systems. One of the focuses of the study is the superior colliculus, or optic tectum. Optic tectum is responsible for the start of orienting responses to visual stimuli. The layered structure inside the optic tectum is vital to understand the neural basis of its sensorimotor transformations. A chapter of the book shows that some specific rules govern critical developmental actions, such as proliferation, migration, differentiation, cell death, and formation of intercellular connections. The article reviews the ontogenetic sequence by which layers form in the lateral geniculate nucleus. Different classes of axons are also covered in the text. The temporal summation in audition is likewise demonstrated. A section of the volume discusses extensively the central auditory system. The book will serve as a good reference for doctors, veterinarians, neurologists, students, and researcher in the fields of anatomy.

Autoren/Hrsg.

Neff, William D.

Inhaltsverzeichnis

1;Front Cover;1
2;Contributions to Sensory Physiology;4
3;Copyright Page;5
4;Table of Contents;6
5;CONTRIBUTORS;8
6;PREFACE;10
7;CONTENTS OF PREVIOUS VOLUMES;12
8;Chapter 1. The Anatomical Basis for Sensorimotor Transformations in the Superior Colliculus;18
8.1;I. Introduction;18
8.2;II. The Laminar Organization of the Superior Colliculus;20
8.3;III. Models of Superior Colliculus Organization;30
8.4;IV. Indirect Visual Pathways to the Deep Layers of the Superior Colliculus;38
8.5;V. Conclusions;47
8.6;References;51
9;Chapter 2. Development of Layers in the Dorsal Lateral Geniculate Nucleus in the Tree Shrew;58
9.1;I. Introduction;58
9.2;II. Features of Lamination in the Mature LGN;60
9.3;III. Development of LGN Layers;66
9.4;IV. The Role of Retinogeniculate Fibers in the Development of Individual Features of Lamination;79
9.5;V. A Model of LGN Development;88
9.6;References;91
10;Chapter 3. 2-Deoxyglucose Studies of Stimulus Coding in the Brainstem Auditory System of the Cat;96
10.1;I. Introduction;96
10.2;II. Interpretation of 2-DG Autoradiographs;98
10.3;III. Effects of Variations in Sound Onset;102
10.4;IV. Effects of Variations in Frequency;106
10.5;V. Effects of Variations in Intensity;110
10.6;VI. Summary;112
10.7;References;113
11;Chapter 4. Axonal Organization in the Cat Medial Superior Olivary Nucleus;116
11.1;I. History of Multiple Classes of Axons;116
11.2;II. Classical Approaches to Identifying Axonal Populations;117
11.3;III. Differential Amino Acid-Labeling Studies;136
11.4;References;144
12;Chapter 5. Auditory Temporal Integration at Threshold: Theories and Some Implications of Current Research;148
12.1;I. Introduction;148
12.2;II. Major Empirical Findings;149
12.3;III. Theories of Auditory Temporal Summation;157
12.4;IV. Some Implications of Current Research;168
12.5;V. Conclusions;173
12.6;References;174
13;Chapter 6. The Specialized Auditory System of Kangaroo Rats;178
13.1;I. Introduction;178
13.2;II. The Middle Ears;182
13.3;III. The Cochlea;200
13.4;IV. The Central Auditory System;206
13.5;V. Summary;209
13.6;References;211
14;INDEX;214

Leseproben

The Anatomical Basis for Sensorimotor Transformations in the Superior Colliculus

William C. Hall and Paul J. May,     Department of Anatomy, Duke University, Durham, North Carolina

Publisher Summary

This chapter describes the laminar organization of the superior colliculus, physiological distinctions between superficial and deep layers, retinal influences of the occipital lobe on the deep tectal layers, and indirect visual pathways to the deep layers of the superior colliculus. Projections from the retina and from the occipital cortex terminate almost entirely in the layers above stratum opticum. The superficial layers appear to be involved in relaying visual information to the diencephalon and also to the cerebellum by way of the relay in the lateral pontine nuclei. The anatomical and behavioral results correlate well with differences in the response characteristics of neurons in the superficial and deep layers. Despite the differences in their response characteristics, the superficial and deep collicular layers are in register spatially. The pathway from substantia nigra pars reticulata may provide the input responsible for the initiation of the motor responses. Both visual and nonvisual sensory inputs can be traced to substantia nigra pars reticulata via relays in the corpus striatum. The deep tectal layers—with respect to their connections with the basal ganglia, cerebellum, and cortical nonprimary sensory areas—are remarkably similar to the motor areas of the cortex.

I Introduction

II The Laminar Organization of the Superior Colliculus

A Cytoarchitecture

B Efferent Connections of the Superficial and Deep Layers.

C Behavioral Studies of Tectal Organization.

D Physiological Distinctions between the Superficial and Deep Layers

III Models of Superior Colliculus Organization

A Retinal Influences on the Deep Tectal Layers.

B Intracollicular Connections between the Superficial and Deep Layers

C Influences of the Occipital Lobe on the Deep Tectal Layers.

D Projections from the Ventral Lateral Geniculate Nucleus to the Deep Tectal Layers

IV Indirect Visual Pathways to the Deep Layers of the Superior Colliculus

A The Distribution of the Tectoreticular Cells

B Relationships between the Optic Tectum and the Basal Ganglia

C Sources of Cortical Input to the Deep Tectum

D Cerebellar Connections with the Superior Colliculus.

V Conclusions

References

I Introduction

The superior colliculus, or optic tectum, is concerned with the initiation of orienting responses to visual stimuli and, probably, to nonvisual stimuli as well (Chalupa and Rhoades, 1977; Dräger and Hubel, 1975; Gordon, 1973; Harris and Gammow, 1971; Jay and Sparks, 1982; Kass 1978; Schneider, 1969; Sprague and Meikle, 1965; Stein and Gaither, 1981; Wickelgren, 1971). This function of the superior colliculus is the subject of considerable study, not only because orientation is a universal behavior but, even more importantly, because the constant relationships between stimulus location and stereotyped motor responses suggest that orienting behavior may provide a relatively simple model for studying the more general problem of how sensorimotor transformations are mediated by the brain.

The superior colliculus is a layered structure and the layers are almost certainly a key to understanding the neural basis of its sensorimotor transformations. Anatomical studies have indicated the importance of differences between the layers by demonstrating that projections from the retina terminate almost entirely in the superficial layers (Abplanalp, 1970; Behan, 1981; Graybiel, 1975; Hubel 1975; Sterling, 1971), whereas the major descending pathways from the colliculus to the lower brainstem regions known to control head and eye movements arise in the deep layers (Altman and Carpenter, 1961; Harting , 1973; Holcombe and Hall, 1981a,b; Kawamura and Hashikawa, 1978). In physiological studies, the superficial layers are considered to be sensory because the neurons in these layers respond at fixed latencies to visual stimulation and have receptive fields arranged into a systematic representation of the visual field (Dräger and Hubel, 1975; Horn and Hill, 1966; Humphrey, 1968; Marchiafava and Pepeu, 1966; Mcllwain and Buser, 1968; Michael, 1972). In contrast, the deeper layers have properties of motor systems. In particular, neurons in the deeper layers discharge prior to saccadic head or eye movements, which shift gaze to a particular locus in the visual field (Crommelinck 1977; Mohler and Wurtz, 1976; Schiller and Koerner, 1971; Sparks 1977; Sparks, 1978; Wurtz and Goldberg, 1971, 1972). An association between the deep layers and motor functions is also suggested by electrical stimulation studies, which indicate that the current levels necessary to produce saccadic eye movements are much lower in the deep layers than in the superficial layers (Schiller and Stryker, 1972; Sparks and Pollack, 1977). In addition, the direction and amplitude of saccades produced by collicular stimulation vary systematically with the site of stimulation (Harris, 1980; Robinson, 1972; Schiller and Stryker, 1972; Stryker and Schiller, 1975). This systematic map of saccades is in register with the map of the visual field that is represented in the superficial layers (Schiller and Stryker, 1972).

The correspondence between the sensory and motor maps suggests that the sensorimotor transformation achieved by the superior colliculus may involve interactions between the superficial and deep layers. Consequently, a primary concern of research in this field has been to identify and describe the patterns of interconnections between these layers. The purpose of this article is to discuss this research and to relate it to various hypotheses that account for the apparent interactions between the layers. The discussion will be presented in three main sections. In the first, we shall briefly describe the anatomical, physiological, and behavioral data that distinguish between the superficial and deep layers. In the second section, we shall discuss several models that have been proposed to account both for the distinctions between the layers and also for how the sensory responses in the superficial layers might initiate appropriate motor responses in the deep layers. In the final section we shall present some recent results that suggest that the solution to the problem of how sensorimotor transformations are accomplished in the superior colliculus lies in part outside of the colliculus itself, and that this solution might also contribute to our understanding of similar transformations in other structures, such as the motor cortex.

II The Laminar Organization of the Superior Colliculus

A Cytoarchitecture

The cytoarchitecture of the superior colliculus is illustrated in Fig. 1 for a species with an exceptionally well-developed tectum, the gray squirrel (). Both the Nissl-stained section and the section stained for myelin illustrate that the mammalian colliculus can be divided into a series of alternating cell and fiber layers. The outermost layer is a cell-free neuropil designated stratum zonale. Beneath stratum zonale is a broad layer, heavily populated with cells, named stratum griseum superficiale. Stratum griseum superficiale can in turn be divided into two sublaminae, an upper zone of small neurons and a lower, thinner band of larger cells. These superficial layers, strata zonale and superficiale, are separated from the deeper layers by a layer consisting primarily of fibers, stratum opticum. Immediately beneath stratum opticum is a cell layer, stratum griseum intermediale. In this layer, an inner sublamina densely populated with cells can be distinguished from an outer, more sparsely populated one. Stratum griseum intermediale is separated by a fiber lamina, stratum album intermediale, from the deepest two layers, strata griseum and album profundum. The deepest two layers merge without clear cytoarchitectonic distinctions into the underlying midbrain tegmentum.

Fig. 1...