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The Neural Basis of Echolocation in Bats
books
Daniel Nlargoliash Departmentof OrganismalBiology andAnatomy, Universityof Chicago, 1025East57thStreet, Chicago,IL50537, USA.
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in the same section), but ND is wholly inadequate for comparing different specimens under different optical conditions. Determination of integrated optical density (IOD) for a stained region is straightforward using a video digitizer. The incident light image (background) is stored in a buffer, the OD is calculated using the ratio of the specimen to background for each pixel and the IOD is the sum of the individual ODs. However, because performing these calculations in 'real time' on a personal computer
requires expensive hardware accelerators, several vendors have implemented shortcuts in the assay. Buyer beware: vendors usually provide no warning if their IOD data do not conform to Beer's Law. This shortcut confusion is illustrated in Mize's chapter on quantitative histochemistry, where a 'real time' formula is presented from a commercial system that saves time by using a constant for the numerator of the ratio (background illumination). So, the 'real time' instrument is accurate if your
optical system is perfectly constant and uniform and your camera has perfectly linear sensitivity. Of course, your data will be inaccurate if your system has any resemblance to reality. In summary, Capowski's book provides a valuable introduction to a rapidly developing field; the application of computers to the study of neuronal architecture. Those interested in video microdensitometry are advised to consult their p-chem texts and evaluate thoroughly commercial claims.
The Neural Basis of Echolocation in Bats
are highlighted throughout the book. Meaningful differences can be seen starting at the level of the cochlea and essentially at every level thereafter. This does not simply validate the comparative perspective, but also gives insight into differentiation between primitive and derived characteristics. To this end, more reference to the relevant mammalian literature, especially that on cats, might have been useful. Where specialization has occurred, organization can be gleaned when it would otherwise be difficult to observe. A particularly valuable example is the hypertrophy of the 60 kHz region of the CF-FM mustached bat, and its ramifications throughout the nervous system. Returning to the problem of the functioning of the system during behavior, the final chapters deal with problems that bats face when they are listening for faint echoes masked by their own intense vocalizations. Here again the system exhibits remarkably elegant species-specific solutions that involve peripheral, brainstem and mid-brain structures. The summary emphasizes that the bat system offers excellent evidence for multiple parallel brainstem auditory pathways, evidence for convergence/divergence at multiple levels, and provides some rationale for these in behavioral terms. A summary might also have attempted to reconcile the known neurobiology with some of the most
challenging behavioral data, and a discussion of the relationships between midbrain and cortical processing, but this has not been attempted. These topics might have been difficult to include without considerably expanding the scope of the monograph. Apart from a few typographical errors, the book is well produced and is extensively and cleverly illustrated. A more difficult aspect is to identify an appropriate readership. The material should be accessible to any serious student, since the authors explain elementary concepts in auditory physiology such as Qlo, interaural time and intensity cues, and terminology for binaural interactions. On the other hand, by design (and reflecting the research interests of the authors) the book does not cover cortical physiology, and offers limited explanations of behavioral observations. These are two areas where enormous and exciting progress has been made. Thus, a comprehensive introduction to bat echolocation would have to include other recent reviews, as the authors point out. Nevertheless, the auditory midbrain serves as a virtual nexus for information to the thalamus and telencephalon, and there is considerable precedent for considering the auditory system to the level of the midbrain. Students of structure-function relationships and those interested in modeling real biological systems will benefit from this scholarly offering.
by G. D. Pollak and J. H. Casseday, Springer-Verlag, 1989. $79.00 (ix + 143 pages) ISBN 0 387 50520 2
The challenge of neuroethology is to explain animal behavior in terms of network wiring diagrams, synaptic weights and connectivities, and other network properties. Its strength lies in an appreciation of behavior and the profound interaction between behavioral specialization and physiological mechanisms. Bat echolocation is a premier vertebrate system where this approach has yielded deep insights into CNS organization and its relationship to behavior. The Neural Basis of Echolocation in Bats examines some of these relationships. The book starts with an introduction to the fascinating world of bat echolocation that is general enough for the uninitiated. After a description of tonotopy in brainstem structures, the main chapters give detailed accounts of the anatomy and physiology of the auditory brainstem and midbrain including the several parallel pathways- and consideration of temporal, spectral and binaural properties of neurons. Some species of bat produce pure frequency modulation (FM) orientation calls while others start their calls with a constant frequency (CF) component. In the true spirit of comparative neurobiology, the differences between these species -
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TINS, VoL 14, No. 1, 1991
Daniel Nlargoliash Departmentof OrganismalBiology andAnatomy, Universityof Chicago, 1025East57thStreet, Chicago,IL50537, USA.
_
_
-iiII
IIII
I
IIIIII IIIIIIIIII
in the same section), but ND is wholly inadequate for comparing different specimens under different optical conditions. Determination of integrated optical density (IOD) for a stained region is straightforward using a video digitizer. The incident light image (background) is stored in a buffer, the OD is calculated using the ratio of the specimen to background for each pixel and the IOD is the sum of the individual ODs. However, because performing these calculations in 'real time' on a personal computer
requires expensive hardware accelerators, several vendors have implemented shortcuts in the assay. Buyer beware: vendors usually provide no warning if their IOD data do not conform to Beer's Law. This shortcut confusion is illustrated in Mize's chapter on quantitative histochemistry, where a 'real time' formula is presented from a commercial system that saves time by using a constant for the numerator of the ratio (background illumination). So, the 'real time' instrument is accurate if your
optical system is perfectly constant and uniform and your camera has perfectly linear sensitivity. Of course, your data will be inaccurate if your system has any resemblance to reality. In summary, Capowski's book provides a valuable introduction to a rapidly developing field; the application of computers to the study of neuronal architecture. Those interested in video microdensitometry are advised to consult their p-chem texts and evaluate thoroughly commercial claims.
The Neural Basis of Echolocation in Bats
are highlighted throughout the book. Meaningful differences can be seen starting at the level of the cochlea and essentially at every level thereafter. This does not simply validate the comparative perspective, but also gives insight into differentiation between primitive and derived characteristics. To this end, more reference to the relevant mammalian literature, especially that on cats, might have been useful. Where specialization has occurred, organization can be gleaned when it would otherwise be difficult to observe. A particularly valuable example is the hypertrophy of the 60 kHz region of the CF-FM mustached bat, and its ramifications throughout the nervous system. Returning to the problem of the functioning of the system during behavior, the final chapters deal with problems that bats face when they are listening for faint echoes masked by their own intense vocalizations. Here again the system exhibits remarkably elegant species-specific solutions that involve peripheral, brainstem and mid-brain structures. The summary emphasizes that the bat system offers excellent evidence for multiple parallel brainstem auditory pathways, evidence for convergence/divergence at multiple levels, and provides some rationale for these in behavioral terms. A summary might also have attempted to reconcile the known neurobiology with some of the most
challenging behavioral data, and a discussion of the relationships between midbrain and cortical processing, but this has not been attempted. These topics might have been difficult to include without considerably expanding the scope of the monograph. Apart from a few typographical errors, the book is well produced and is extensively and cleverly illustrated. A more difficult aspect is to identify an appropriate readership. The material should be accessible to any serious student, since the authors explain elementary concepts in auditory physiology such as Qlo, interaural time and intensity cues, and terminology for binaural interactions. On the other hand, by design (and reflecting the research interests of the authors) the book does not cover cortical physiology, and offers limited explanations of behavioral observations. These are two areas where enormous and exciting progress has been made. Thus, a comprehensive introduction to bat echolocation would have to include other recent reviews, as the authors point out. Nevertheless, the auditory midbrain serves as a virtual nexus for information to the thalamus and telencephalon, and there is considerable precedent for considering the auditory system to the level of the midbrain. Students of structure-function relationships and those interested in modeling real biological systems will benefit from this scholarly offering.
by G. D. Pollak and J. H. Casseday, Springer-Verlag, 1989. $79.00 (ix + 143 pages) ISBN 0 387 50520 2
The challenge of neuroethology is to explain animal behavior in terms of network wiring diagrams, synaptic weights and connectivities, and other network properties. Its strength lies in an appreciation of behavior and the profound interaction between behavioral specialization and physiological mechanisms. Bat echolocation is a premier vertebrate system where this approach has yielded deep insights into CNS organization and its relationship to behavior. The Neural Basis of Echolocation in Bats examines some of these relationships. The book starts with an introduction to the fascinating world of bat echolocation that is general enough for the uninitiated. After a description of tonotopy in brainstem structures, the main chapters give detailed accounts of the anatomy and physiology of the auditory brainstem and midbrain including the several parallel pathways- and consideration of temporal, spectral and binaural properties of neurons. Some species of bat produce pure frequency modulation (FM) orientation calls while others start their calls with a constant frequency (CF) component. In the true spirit of comparative neurobiology, the differences between these species -
38
_
TINS, VoL 14, No. 1, 1991