Methods in Psychobiology: Specialized Laboratory Techniques in Neuropsychology and Neurobiology

Methods in Psychobiology, Volume 2, Specialized Laboratory Techniques in Neuropsychology and Neurobiology is intended for the beginning ""student"" in physiological, neuro-, bio-psychology, or whatever label one wishes to attach to the exciting interdisciplinary field which weds the brain and behavior. In contrast to Volume 1, somewhat more emphasis is given in the selection of topics to a number of difficult behavioral methods that are used frequently by individuals in the more traditional neurosciences. The book begins with a discussion of the measurement of behavioral activity. This is followed by separate chapters on techniques such as electric shock motivation; aversive learning; methods of assessing the behavioral effects of drugs; long-term intravenous infusions; and perfusion of different parts of the brain. Subsequent chapters deal with the assay of pharmacologically active substances; the split-brain technique; using microknives in brain lesion studies and the production of isolated brain-stem islands; the functional decortication technique; and recording evoked potentials.

• Language: English
• Publisher: Academic Press
• Release date: Oct 22, 2013
• ISBN: 9781483268293

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Specialized Laboratory Techniques in Neuropsychology and Neurobiology

METHODS IN PSYCHOBIOLOGY

Volume 2

R.D. MYERS

Laboratory of Neuropsychology, Purdue University, Lafayette, Indiana, U.S.A.

Table of Contents

Cover image

Title page

Copyright

LIST OF CONTRIBUTORS

PREFACE

Chapter 1: Measuring Behavioral Activity

Publisher Summary

I INTRODUCTION

II METHODS OF MEASUREMENT

III THE REVOLVING WHEEL

IV STABILIMETER AND STATIONARY-CAGE RECORDING

V CONCLUSIONS

ACKNOWLEDGEMENT

Appendix

Chapter 2: Techniques of Electric Shock Motivation

Publisher Summary

I APPARATUS FOR DELIVERING THE SHOCK TO THE SUBJECT

II SHOCK SOURCES: GENERAL CONSIDERATIONS

III TYPES OF SHOCK SOURCES

IV SHOCK SCRAMBLERS

V FACTORS WHICH CAN ATTENUATE GRID FLOOR SHOCK

VI BASIC TECHNIQUES FOR THE MEASUREMENT AND CONTROL OF ELECTRIC SHOCK MOTIVATION

Chapter 3: Aversive Learning Situations: Apparatus and Procedures

Publisher Summary

I INTRODUCTION

II INSTRUMENTAL AVERSIVE SITUATIONS

ACKNOWLEDGEMENT

Appendix

Chapter 4: Assessing the Effects of Drugs

Publisher Summary

I INTRODUCTION

II PHARMACOLOGICAL CONSIDERATIONS

III BEHAVIORAL CONSIDERATIONS

Appendix

Chapter 5: Manipulation of the Oral and Gastric Environments

Publisher Summary

I ORIGIN AND APPLICATION OF TECHNIQUES

II METHODS

III FUTURE APPLICATIONS

ACKNOWLEDGEMENTS

Appendix

Chapter 6: Long-term Intravenous Infusion

Publisher Summary

I INTRODUCTION

II SADDLE AND FEEDTHROUGH SWIVEL

III CANNULA CONSTRUCTION

IV SURGICAL PROCEDURE

V TROUBLE SHOOTING AND SPECIAL ARTS

Appendix

Chapter 7: Methods for Perfusing Different Structures of the Brain

Publisher Summary

I INTRODUCTION

II PERFUSING THE CEREBRAL VENTRICLES

III ISOLATED TISSUE PERFUSION WITH PUSH-PULL CANNULAE

IV PERFUSION OF THE CORTEX

V THEORETICAL CONSIDERATIONS

Appendix

Chapter 8: The Neurobiological Assay

Publisher Summary

I INTRODUCTION

II IDENTIFICATION BY PHARMACOLOGICAL ANALYSIS

III RECORDING THE CONTRACTIONS OF ISOLATED SMOOTH AND STRIATED MUSCLES

IV THE BIOASSAY OF ACETYLCHOLINE

V THE BIOASSAY OF 5-HYDROXYTRYPTAMINE (SEROTONIN)

VI THE BIOASSAY OF CATECHOLAMINES

APPENDIX

Chapter 9: Specialized Lesions: The Split-Brain Technique

Publisher Summary

I HISTORICAL INTRODUCTION

II SURGICAL METHODS

III POST-SURGICAL CARE

IV HISTOLOGICAL VERIFICATION OF SURGERY

V FABRICATION OF INSTRUMENTS FOR SPLIT-BRAIN SURGERY. (FIG. 10)

VI BEHAVIOURAL TESTING METHODS

Appendix

Chapter 10: Specialized Lesions: Cerveau Isolé and Encephale Isolé

Publisher Summary

I INTRODUCTION

II THE CERVEAU ISOLé

III THE ENCEPHALE ISOLé

IV MAINTENANCE AND NURSING CARE

V THE USE OF THE PREPARATIONS FOR PSYCHOBIOLOGY

ACKNOWLEDGEMENT

Appendix

Chapter 11: The Use of Microknives in Brain Lesion Studies and the Production of Isolated Brain-stem Islands

Publisher Summary

I BRAIN LESIONS: GENERAL CONSIDERATIONS

II THE USEFULNESS OF MICROKNIVES

III THE HYPOTHALAMIC ISLAND

IV THE DESIGN AND CONSTRUCTION OF KNIVES

V THE HYPOTHALAMIC ISLAND: PROCEDURES AND POST-OPERATIVE CARE

Appendix

Chapter 12: Inducing Cortical Spreading Depression

Publisher Summary

I INTRODUCTION

II SEMI-CHRONIC TECHNIQUE

III CHRONIC TECHNIQUE

IV MAIN FIELDS OF APPLICATION

Appendix

Chapter 13: Recording Evoked Potentials

Publisher Summary

I INTRODUCTION

II THE RECORDING SITUATION

III STIMULUS GENERATORS

IV INSTALLATION OF ELECTRODES IN HUMANS AND ANIMALS

V EVALUATION OF EVOKED POTENTIAL DATA

Appendix

AUTHOR INDEX

SUBJECT INDEX

Copyright

ACADEMIC PRESS INC. (LONDON) LTD.

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United States Edition published by

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Copyright © 1972 by

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No part of this book may be reproduced in any form by photostat, microfilm, or any other means, without written permission from the publishers

Library of Congress Catalog Card Number: 76–153535

ISBN: 0-12-512302-7

Text set in 11/12 pt. Monotype Scotch Roman, printed by letterpress, and bound in Great Britain at The Pitman Press, Bath

LIST OF CONTRIBUTORS

D.B. BELESLIN,     Faculty of Medicine, Institute of Pharmacology, Beograd 11105, Yugoslavia (pp. 213–256)

J. BUREŠ,     Institute of Physiology, Czechoslovak Academy of Sciences, Prague, Czechoslovakia (pp. 319–343)

O. BUREŠOVÁ,     Institute of Physiology, Czechoslovak Academy of Sciences, Prague, Czechoslavia (pp. 319–343)

B.A. CAMPBELL,     Department of Psychology, Princeton University, Princeton, New Jersey 08540, U.S.A. (pp. 21–58)

E.D. CAPALDI,     Department of Psychological Sciences, Purdue University, Lafayette, Indiana 47907, U.S.A. (pp. 59–81)

E.J. CAPALDI,     Department of Psychological Sciences, Purdue University, Lafayette, Indiana 47907, U.S.A. (pp. 59–81)

P.B. DEWS,     Department of Psychiatry, Harvard Medical School, Boston, Massachusetts 02115, U.S.A. (pp. 83–124)

G. ELLISON,     Department of Psychology, University of California, Los Angeles, California 90024, U.S.A. (pp. 303–318)

F. FINGER,     Department of Psychology, University of Virginia, Charlottesville, Virginia 22901, U.S.A. (pp. 1–19)

S.S. FOX,     Department of Psychology, University of Iowa, Iowa City, Iowa, U.S.A. (pp. 345–369)

H. KISSILEFF,     University of Pennsylvania, School of Allied Medical Professions, 13901 Pine Street, Philadelphia, Pennsylvania 19104, U.S.A. (pp. 125–154)

F.A. MASTERSON,     Department of Psychology, University of Delaware, Newark, Delaware 19711, U.S.A. (pp. 21–58)

R.D. MYERS,     Laboratory of Neuropsychology, Purdue University, Lafayette, Indiana 47907, U.S.A. (pp. 169–211)

P. ROSENFELD,     Department of Psychology, Northwestern University, Evanston, Illinois, U.S.A. (pp. 245–369)

C.B. TREVARTHEN,     Department of Psychology, University of Edinburgh, Edinburgh, Scotland (pp. 351–284)

J. VILLABLANCA,     Departments of Psychiatry and Anatomy, Mental Retardation Program, NPI, University of California, Los Angeles, California, U.S.A. (pp. 285–302)

J. WEEKS,     Department of Pharmacology, The Upjohn Company, Kalamazoo, Michigan 49001, U.S.A. (pp. 155–168)

PREFACE

LIKE the first Volume of this series, Volume 2 is again intended for the beginning student in physiological, neuro-, bio-psychology, or whatever label one wishes to attach to the exciting interdisciplinary field which weds the brain and behavior. Once again, the pervasive meaning of student is reiterated since this word encompasses any individual, be he undergraduate or professor, who because of his imagination and curiosity desires to pursue an experiment on some aspect of brain function.

In contrast to Volume 1, it is apparent from the Contents that somewhat more emphasis is given, in our selection of topics, to several of the difficult behavioral methods that are used frequently by individuals in the more traditional neurosciences. There are horrendous pitfalls that one can unwittingly encounter when measuring what appears, superficially at least, to be the events in a straightforward behavioral task. Thus, fundamental information is provided in the early chapters pertaining to certain special procedures used by experimental psychologists which have tangible utility to those on the physiological side of the coin.

The principles of each scientific method, whether surgical or observational, may well apply to a variety of experimental situations. Although Volume 2 stands on its own, the reader should be cautioned that the ideas and techniques presented here are not in any way independent of those contained in Volume 1 of this series. The integrated nature of the series is predicated on the fact that the knowledge gained from the chapters in Volume 1 relate intimately to the more specialized methods in the pages to follow. To illustrate that the basic skills are mastered first, one would not, in fact, attempt to section the corpus callosum by aspiration (Chapter 9) unless the fundamental technique of suction lesioning was acquired as described in Volume 1 (Chapter 4) with cortical or other preparations. Further, stereotaxic, histological, and other essential procedures are requisite to any advanced undertaking.

Again, the authors were chosen because they are active laboratory workers who are notably proficient in the particular technique about which they have written. Refraining from turgidity, each author attempts to be as descriptive as possible in presenting a rational approach to the respective method.

The editor is deeply grateful to Marjorie Myers, our Laboratory Editor, for her untiring efforts given to every facet of the production of this Volume, and to Peter Curzon, Head Technician of the Laboratory, for his capability in attending to the photographic requirements of several of the chapters. Finally, the splendid cooperation and patience of the Academic Press is deeply appreciated.

Lafayette, Indiana March, 1972

R.D. MYERS

Chapter 1

Measuring Behavioral Activity

FRANK W. FINGER,     Department of Psychology, Gilmer Hall, University of Virginia, Charlottesville, Virginia, U.S.A.

Publisher Summary

This chapter discusses the belief that electro, neuro, and physiological sophistication may be wasted unless the subtleties on the measurement end of the enterprise are to a degree recognized. The measures of general behavioral activity can be so distorted by irrelevant variables that they are sometimes of questionable value. A few simple precautions need to be taken by the experimenter to sufficiently reduce the variability to have a powerful tool for the assessment of the neurophysiological state. There is still the effect upon one’s results of the type of measuring device and the uncertainty of how this may best be dealt with. For testing the effect of brain interference, the running wheel seems a logical choice in view of its mechanical simplicity and the demonstrated sensitivity of running to physiological and environmental manipulations. The chapter discusses the recording techniques that are similar in that the animal lives in an enclosure much like a standard home cage. Various shapes and sizes are used with the average dimension perhaps two or three times the body length. More than is the case with the wheel, these methods have been readily adapted to species other than the rat.

I. Introduction

II. Methods of Measurement

III. The Revolving Wheel

A. Characteristics of the Wheel

B. The Measurement Period and Habituation

C. Individual Differences

D. Long-range Changes

E. Environmental Control

F. Use of Side Cage

G. Recording

IV. Stabilimeter and Stationary-cage Recording

A. General Characteristics

B. Stabiiimeters and Tilt Cages

C. Photoelectric Recording

D. Ultrasonic Recording and Resonant Circuits

E. Direct Observation

V. Conclusions

Acknowledgement

References

Appendix

I INTRODUCTION

A QUICK glance at the chapter headings in these volumes suggests a greater emphasis on neuro- than upon -psychology. There is no doubt that the prospective experimenter will welcome the chapters of detailed instructions in the manipulation of the independent variable, involving as it does a relatively inaccessible and somewhat mysterious mass of tissue and drawing upon several disciplines for its specialized techniques. By contrast, the reliable recording of the consequent behavior changes usually seems pretty straightforward and routine, demanding little more than a modicum of common sense, an equipment catalogue, and a modest grant. At the gross level this may be adequate. It is sometimes obvious that the brain-operated animal eats nothing, that his bar-pressing for water is insufficient to keep him alive, that his learning is retarded, or that he is incapable of coordinated locomotion on a flat surface.

But as extirpation-by-teaspoon is replaced by functional ablation, stereotaxic localization, and microdissection, it is also appropriate to advance to a more fine-grained analysis of the dependent variable. This chapter, as well as Chapter 10 in Volume I of this series and Chapters 2, 3 and 4 in this volume, is predicated on the belief that electro/neuro/physiological sophistication may be wasted unless the subtleties on the measurement end of the enterprise are to a degree recognized.

Long a favorite behavioral target of the psychopharmacologist, general activity has in recent years been increasingly adopted as an assay tool by neuropsychologists. A change in activity level can indeed be a sensitive indicant of an altered internal state (motivation?), but its maximal usefulness requires attention to a number of potentially distorting factors. Failure to take these into account has led in many instances to unnecessary variability of the data, and on occasion, to conclusions that seemingly contradict each other. The identification of some of these pitfalls will be the major goal of the pages that follow.

In terms of its operational definition, and I question the present utility of any other, general activity must be regarded as multiple rather than unitary, and the first lesson to be heeded is that the differently measured general activities may diverge under identical biological conditions. Thus, the amount of the rat’s wheel running during the third day of continuous water deprivation is usually several times the ad lib. base-line (Finger and Reid, 1952), but measurement in a stabilimeter may yield no significant change, or even a decreased count (Campbell, 1964). The 4- or 5-day estrous cycle of activity is much more clearly revealed by wheel recording than by photocell recording or direct observation of the female rat’s movements about the home cage (Finger, 1961, 1969). Telencephalic lesions differentially affect activity in wheel and stabilimeter (Campbell and Lynch, 1969), and there is evidence that the behaviors reflected in the contrasting scores are mediated by different pathways (Lynch, 1970).

Clearly it is inappropriate, in enumerating the consequences of a neurological manipulation, to refer simply to a change or lack of change in general activity, without specifying the method of measurement. The specification of the situation must extend to the physiological and environmental conditions, for complex interactions seem to be the rule rather than the exception. To illustrate: hunger greatly accentuates the difference between frontal rats and controls in the stabilimeter, but not in the wheel (Campbell and Lynch, 1969), and deep frontal lesions elevate stabilimeter scores much more in the light than in the dark, but only during the first few postoperative days (Harrell and Isaac, 1969). As one examines in detail the major types of activity measurement, the suspicion is born that any neurological intervention can be shown to produce a change under some combination of circumstances. A dubious dividend is the limitation which such rich diversity imposes upon interpretation.

II METHODS OF MEASUREMENT

Any listing of methods that attempts to be both inclusive and restrictive would be an exercise in arbitrariness. It might be argued that the common label should be applied only to those procedures that yield similar results under comparable conditions, but at this point, the data required for such a classification are still fragmentary. In deciding which methods to describe, I have simply accepted the investigator’s statement that what he is measuring can legitimately be termed general activity.

As a guide for the experimenter’s minimal coverage of the possibilities, it may tentatively be hypothesized that the revolving wheel or drum as normally used is in a category by itself, with all the other techniques in a second group. But even this prescription, it must be acknowledged, cannot yet be generalized beyond the rat. Further, there is a real possibility that such a dichotomy is reasonably valid for the intact organism, but that for brain-operated subjects a quite different subdivision is required.

III THE REVOLVING WHEEL

The classic general activity study describes the rat in a wheel or revolving drum. The tread of the wheel in most common use (Wahmann Mfg. Co.; -in opening in the supporting bulkhead, into a side-cage where food and water can be supplied. An arm attached to an eccentric on the axle connects to a mechanical counter, which accumulates complete revolutions in either direction (and occasionally spurious additional counts, when the wheel happens to rock back and forth around the position of engagement of the counter’s ratchet). Some investigators have modified the system for their particular purpose, e.g., counting every 1/5 revolution (Slivka et al., 1967), and requiring a reversal of running direction after each revolution (Pereboom, 1968).

FIG. 1 The revolving wheel, with side cage. The water bottle is normally attached by a spring to the outside at one end, with the spout extending into the side cage. A food cup can be hung on the inside, or fastened to the mesh floor. (Courtesy Wahmann Mfg. Co.)

For accommodation of a large number of subjects in a limited floor space, we have designed a 2-tiered rack (60 in long × 16 in wide × 77 in high) holding 6 Wahmann wheels. Built-in fluorescent fixtures immediately above each bank of wheels insure even illumination, and when remote recording of activity is required (see Section III, G), the electrical circuit from each wheel plugs into its channel in the cable serving the entire unit. Even more economical of space, although in some respects less convenient to service, are batteries of 8, 12 or 16 wheels, manufactured by the E. A. Kaestner Co. (See Fig. 2.)

FIG. 2 in, the tread width 6 in. (Courtesy E. A. Kaestner Co.)

The meaning of any general activity data depends upon a number of characteristics of the experimental situation, and failure to take these into account has often led to discrepant reports. They are most clearly documented in experiments involving the wheel, but parallel considerations will be raised briefly in later sections.

A Characteristics of the Wheel

The properties of the wheel itself may be crucial (Skinner, 1933; Lockhard, 1965). The frictional torque can be altered by adjusting the cone ball bearing, of a bicycle type, supporting the axle. Ideally the turning force of the wheels to be used is equated, for example by the method described by Lacey (1944) and Lockhard (1965). In practice this control is seldom sufficiently precise for a between-groups design, and must be supplemented by balanced assignment of wheels across conditions.

Unless prohibited by other requirements, it is safest to use the subject for its own sequential control. Periodic calibration is a desirable safeguard in any instance, especially if the design calls for repeated measures over an extended period of time and irreversible treatment makes return to baseline conditions impossible.

For species other than the rat, wheels of different dimensions have been used (e.g., 100-cm circumference for the hamster [Richards, 1966], 6-in diameter for the mouse [Acme Research Products]). Collier and Leschner (1967) demonstrated that, while normal mice ran farther in the small wheel than in the 14-in rat wheel, the work expended was invariant across the two. This relationship, of course, might not hold in brain-damaged or otherwise abnormal individuals, or in other species.

-in lip that prevents this. Since the mesh is too fine to allow larger boluses and food to drop through, there tends to be an accumulation of debris that is not only unsanitary and a source of extraneous noise during running, but with some frequency interferes with free turning. -in holes in the metal rim forming the inner edge of the running surface, to allow the unwanted material to fall out. To decrease binding of the wheel, especially when it has been bent somewhat out of shape, we sometimes remove the metal plate covering the threshold of the opening between wheel and side cage.

B The Measurement Period and Habituation

How long a measurement period is required to ascertain whether a manipulation has altered activity level, and how much prior experience in the wheel must the subject have had to avoid contamination by the curiosity or emotionality traditionally ascribed to behavior in novel settings? There is no simple answer, beyond the empirical one. We have reported (Finger, 1965) a significant difference between groups of rats under 0- vs 24-hr food deprivation during their first 10 min in the wheel. The operation of a more subtle variable might be detectable only with an observation period of several hours, and the complete description of its effect, including its circadian characteristics (see, for example, Cold Spring Harbor Symposia, 1960), will require that the subject live continuously in the apparatus.

Whenever we can, we avoid the possible interaction with novelty and the rat’s initial inability to turn the wheel smoothly, by providing an extended preadaptation period. This is certainly essential when using a repeated-measures design, for during the first week a marked day-by-day increase in revolutions is typically recorded, and as long as a month’s habituation may be required to achieve a moderately stable baseline.

C Individual Differences

There are vast individual differences in baseline running, even among like-sexed litter mates. Some individuals turn the wheel not at all, although a few of these will respond to a couple of days of starvation with the usual hyperactivity and thereafter maintain a reasonable level of running. Others are high runners from the beginning (5,000–15,000 revolutions per 24 hr). Additionally, rats older than 120–150 days tend to be less active than younger adults, and of course females in estrous are most active of all.

Different strain samples vary widely in their vigor, with young males averaging between about 500 and 5,000 revolutions a day in wheels adjusted to turn freely, mature females between 4,000 and 10,000. Observation over a few days is usually sufficient to determine the general range of running and the ranks within a group. Our data indicate that an individual will maintain his relative intra-group position for at least 5–6 weeks. Obviously, some experiments require pretreatment selection of subjects with comparable records, or must use large numbers to balance out the original variability. In at least exploratory studies, it is desirable to include a wide range of activity levels, for high runners and low runners may respond differentially, and even in opposite directions, to the independent variable. Within a heterogeneous group, the individual’s reaction to the experimental manipulation is best described in terms of proportional change from pretreatment baseline which is, ideally, 5–7 undisturbed days.

D Long-range Changes

In studies extending beyond a month or so, a steady decline in activity is eventually to be expected, irrespective of age (Seward and Pereboom, 1955). Where the long-range effect of an irreversible treatment is being examined, an untreated, adequately matched control group can provide a continuing reference level. With repeated acute treatments, the subject can serve as its own control. Particularly in view of the additional possibility of residual effects, a comparison should always be made with the subject’s immediately preceding baseline of several days, and perhaps post-recovery performance.

E Environmental Control

Optimally, extraneous stimulation is eliminated by enclosing each wheel unit in its own environmental chamber. At the least, the experimental room must be secure against visual and auditory disturbance, and inter-animal stimulation minimized by provision of visual screens between units and a continuous background of white noise of about 80 db SPL. We have obtained some data suggesting that change in either direction in background noise from the familiar level tends to depress running for 1–3 days. Presumably such transient effects are readily overcome by habituation, although there may be persisting interaction with such variables as brain damage.

For animals living continuously in the apparatus, our regularly-scheduled maintenance of replenishing food and water, cleaning, and checking the free turning of the wheels is carried out quickly and as quietly as possible. The disruption reflected in the records extends for some animals as long as 30–60 min, and so we discard at least this portion of the data, if not the figures for the entire day.

Under conditions of continuous light or continuous dark, general activity as well as most other behavioral and physiological functions drifts away from the 24-hr schedule, and meaningful analysis becomes complicated (Halberg, 1969). Unless we are investigating free-running circadian phenomena themselves, we therefore maintain our subjects on a fixed illumination regimen, usually 12-hr light and 12-hr dark. Since it is imperative that disruption of this cycle be avoided, and recording and/or servicing may need to be carried out in the dark, a red 40-W fluorescent tube (General Electric F40R) is continuously on, and a light-lock is provided for the door of the experimental room.

F Use of a Side Cage

Access to the side cage, for eating and drinking, leads to two kinds of problems. The first is simply contamination of the food, which can be reduced by restricting the space directly over the food cup, so that the rat is unable to rest there (see, for example, the critical measurement feeder for the Rat Activity Study Cage, Acme Research Products). A more serious consequence is that a significant number of movements go unrecorded as the subject goes back and forth between wheel and side cage. To overcome this we have in some experiments eliminated the side cage and supplied food and water directly through the bulkhead (see Fig. 3).

FIG. 3 Schematic side view of modified food hopper and panel, showing its relation to the wheel.

A Wahmann LC-303 food hopper and water-bottle holder is modified by removing the top edge, which is normally used to hang the hopper to the cage front, and bending the bottom edge forward and up at a 45° angle to form a protruding ledge. The hopper is then attached to an aluminum panel that in turn is bolted to the bulkhead in such a way that the opening into the wheel is closed off. The ledge extends through a slit in the panel, so that the rat can take from it the pellets of Purina guinea pig chow. The water-bottle spout also extends into the wheel area, through a small hole in the panel and bulkhead. There is evidence that under certain conditions such as high ambient temperature, the more complete registration of the animal’s activity, resulting from this arrangement, yields a different function from that found with the standard combination of wheel and cage.

G Recording

We have experienced little trouble with the mechanical counters (Veeder), except after an overzealous caretaker subjected the units to a steam bath, and in such a case the counters are easily replaced.

In many activity studies, the counters are read only once every 24 hr. We have so often found that light-activity and dark-activity are differentially affected by an imposed variable that we routinely record at least twice daily, at each illumination change. It is sometimes the case that distribution of activity over the daily cycle, rather than total amount, is the significant measure. It may be useful, for example, to determine the number of hours during the day or during various portions of the day, or the number of 30-sec periods, in which some activity has occurred. Here automatic printing or punching of data at the shorter intervals, or continuous recording (e.g., by Esterline-Angus Event Recorder) is called for. The required circuitry can be activated by a 3-leaf switch so positioned as to be opened and closed by the movement of the arm that advances the Veeder counter.

To eliminate repeated false impulses when the wheel rocks back and forth, the design includes a capacitor, charged and discharged at opposite excursions of the central leaf. Remote location of the recorders not only eliminates auditory feedback to the subjects but also gives the extremely desirable bonus of reducing disturbance of the subjects by the experimenter.

IV STABILIMETER AND STATIONARY-CAGE RECORDING

It is not immediately apparent that the rat’s movements as he turns the wheel, sometimes at a virtually constant rate for the better part of an hour, has any close counterpart in his repertoire when living in the natural or non-laboratory environment. Intuitively, it might seem more useful to measure components of his behavior as he reacts in and to surroundings more similar to his workaday world. Whatever the speculative arguments, there are empirical grounds (cf. p. 2) for insisting that a reasonably complete description of general activity must include at least one form other than the quasi-locomotion recorded in the wheel, and for suspecting that these others may be fairly equivalent to one another.

A General Characteristics

The several recording techniques discussed in this section are similar in that the animal lives in an enclosure much like a standard home cage, and some aspect of its behavior is monitored. Various shapes and sizes are used, with the average dimension perhaps two or three times the body length. More than is the case with the wheel, these methods have been readily adapted to species other than the rat.

As with the wheel, short periods of recording may yield useful data, but continuous living in the cage, with recording at least twice daily, is often desirable. Establishment of a baseline, 4–6 days is probably adequate, can usually be begun after no more than one week’s habituation to the situation. The precautions pertaining to the strict maintenance of constant conditions during testing should be re-emphasized, as well as the necessity for taking into account the age, sex, and strain differences and dealing with uncontrolled variability by repeated measures or grouped data.

B Stabilimeters and Tilt Cages

The stabilimeter is a cage so supported that it is displaced slightly from resting position by the subject’s movements. With most devices the displacements are simply counted as a function of time. There is usually no attempt to quantify amplitude of movement and no way to identify the type of movement that causes the cage displacement.

The early-developed jiggle cages for rodents were tambour-mounted (e.g., Richter, 1927) or spring-suspended (e.g., Hunt and Schlosberg, 1939). An apparatus employing similar principles has been successfully used with sheep and dogs (e.g., Anderson and Parmenter, 1941). These have for the most part been supplanted by some sort of tilt cage.

Campbell (1964) most often uses a rectangular cage supported by a central transverse axle, with a microswitch at each short end. The switches are connected with a single counter, so that the score is number of tilts from end to end, corresponding to the number of times the center of gravity of rat plus cage shifts across the axle. It has been suggested (Strong, 1957) that the form of the obtained function varies with the amplitude of deflection required to complete the circuit. For example, a cage that detects such small movements as grooming and restless stirring may yield a lesser relative change in score under food deprivation than does a cage that records only locomotion.

Other devices depending on cage movement include a centrally pivoted annular runway or gallery (-in diameter for the rat (Campbell, 1964), 15-in for the opossum (Cone and Cone, 1968), both with microswitches around the periphery.

C Photoelectric Recording

To the extent that kinesthetic feedback from the moving stabilimeter interacts with the variable under scrutiny, it may be preferable to substitute a stationary cage with a recording system that responds to the animal’s activity without stimulating it. In a number of experiments with rats we have successfully used photoelectric recording (e.g., -in wire mesh. The long axis is bisected, about 3 in above the floor, somewhat less for young subjects, by a beam of far-red light (Wratten Photometric Filter No. 87) to which the rat’s retina is insensitive. Interruption of the beam advances a remote counter and an event recorder.

As light source we use a tube-enclosed flashlight-type bulb (Chicago Miniature Lamp Bulb, 313), run at 24 V to reduce heat and lengthen bulb-life. Interference by the overhead room illumination is minimized by shielding the photocell (Clairex CL-3) and including a converging lens in the optic system. Light source and cell are rigidly mounted on a common support, permitting ready replacement of the entire unit without disturbing the rather critical alignment of the components. The support runs beneath the cage and positions cell and light source about 1 in outside their respective cage sides. The circuit is biased to minimize recording of small movements that partially occlude the beam (Fig. 4).

FIG. 4 Circuit diagram of photocell activity recorder.

The absolute number of counts produced by a given subject of course depends upon the properties of the particular recording unit, be it stationary cage or wheel. As a rule, scores are substantially lower in the former than in the latter device (Weasner et al., 1960); if cross-apparatus comparison of a treatment effect is to be made, it must be in terms of such a relative measure as per cent deviation from baseline. It is relevant to note further that cage activity tends to be distributed more evenly across the 24 hr than is wheel running. For example, in the wheel it is not unusual for 95% or more of the mature male rat’s daily running to be concentrated within the dark 12 hr, while in the stationary cage the figure averages closer to 75%.

With larger species, the dimensions of the cage are correspondingly increased. To illustrate, Isaac and Reed (1961) studied the cat in an enclosure 30 in × 21 in × 22 in; for Macaca mulatta the dimensions were 24 in × 18 in × 20 in (DeVito and Smith, 1959), and for the rhesus monkey 22 in × 17 in × 24 in (Gross, 1963).

in prevents accumulation of feces.

One limitation of the stabilimeter and the stationary-cage systems thus far described is the grossness of their discrimination. For example, the subject can move about at one end of the rectangular cage without activating the counter, whereas multiple small movements of the head or a limb may inflate the score if he happens to be in the vicinity of the beam or at the center of gravity. Division of the cage into small sectors, with independent sensors, is one way to refine the measurement. Multiple photocells (Lehigh Valley Electronics, B1497; cf. Henderson, 1963; Fuller, 1967), or separately-recording floor sections which are electrically (Raphelson and Rabin, 1964) or mechanico-electrically (Campbell, 1964) coupled to a counter permit a degree of resolution that may be worth the complication of design.

D Ultrasonic Recording and Resonant Circuits

The monitoring of all movements, amplitude-integrated and without any coupling to the organism that might affect it, is more completely achieved by ultrasonic recording (Peacock and Williams, 1962; Peacock et al., 1966). A 40-kc acoustic signal, attenuated below auditory threshold, is delivered into the test area. As the animal moves through the three-dimensional pattern of standing waves, the alterations in reflected energy are picked up by a ceramic microphone and recorded as digital counts. Sensitivity can be varied over a broad spectrum, ranging from breathing to locomotion. The technique is not without its problems, however, for the spatial and acoustical characteristics of the test area are critical for reliable measurement. The transmitting and receiving crystals must be positioned rigidly. If a wire cage is used, it should be enclosed in a chamber of such material as fiberboard.

Separately caged animals can be housed in the same chamber, provided that there is shielding between them and that their respective transmitters are driven by a common oscillator. There is some ambiguity in the scores produced, for the changes in the energy field can be influenced by the plane of movement and the subject’s distance from the receiver. When comparisons are made across cages, calibration should be with moving targets of various size, speed, position, and direction.

One advantage of the ultrasonic system is its adaptability to a wide range of species, from rodent to human (McFarland et al., 1966) or, as one manufacturer states, from mosquitoes to elk. When a test enclosure of increased dimensions is required, the circuitry can be modified to accommodate the demand for increased power, or several transmitters can be added (Crawford and Nicora, 1964).

A change in the capacitance of a resonant circuit, as the rat or mouse moves through the associated fields of force, is the basis for the recording systems described by McClelland (1965) and Van-Toller and de Sa (1968). These and commercial models by Columbus Instruments (Selective Activity Meter) and Stoelting (Electronic Activity Monitor) are said to have advantages similar to those of ultrasonic recording, viz., no sensible effect upon the subject, summation of all movements, and possibility of varying sensitivity of detection. Standardization data are not yet reported.

E Direct Observation

But the question still remains: What is being measured by all these automated cages? The ultrasonic device does not ordinarily differentiate the rat’s grooming from eating and yawning, nor can the photocell and running wheel discriminate the various normal and abnormal locomotor gaits. The psychologist’s most primitive sensor, the human eyeball, is still useful, with or without supplement by camera and video tape. The tedium of direct observation can be reduced by systematic sampling (Bindra and Blond, 1958), and the wealth of more detailed information sometimes repays the considerable effort.

Of course the return of the observer does not automatically insure the most meaningful data; we have found it necessary to revise some aspects of our method as new variables are explored. Our basic procedure involves a sampling session every 2 hr around the clock (Mathews and Finger, 1966). In the course of a session we scan the 10–12 individual cages 20 times, beginning at 60-sec intervals, categorizing each rat’s behavior at first glance. We have standardized with good inter-judge reliability our criteria for floor locomotion, climbing (young subjects only), rearing, head movement, eating, drinking, cage biting, standing, resting with eyes open or eyes closed, cage licking (under water deprivation), and saliva spreading (particularly at elevated ambient temperature). The refinement of these and the addition of other categories may be necessary for adequate description in other species (e.g., Richards, 1966) or after neural interference. Another schedule of sampling, e.g. 10 min/hr, might be more revealing, albeit more confining for the observer.

There is an obvious danger of observer bias, even when categories are well defined. For this reason it is desirable to balance the assignment of observers across conditions, and where possible to keep the observer in ignorance of the experimental condition.

The usual precautions are taken to minimize extraneous and inter-subject stimulation. Since the presence of an observer has been shown to influence results, we view from behind a one-way window. During the dark 12 hr, illumination is provided by several red fluorescent tubes (General Electric F40R). While it is apparent that the albino rat will respond briefly to changes between this condition and complete darkness, the spectrum emitted is so low on the visibility curve that neither the total activity nor the day/night ratio is significantly affected by the presence of this red light.

(1) The Open Field

When the enclosure in which the animal is observed is considerably larger than the usual individual cage, it is designated as an open field. It may be circular with a diameter as great as 8 ft or square, most often 2–3 ft on a side, divided by painted lines into smaller areas to facilitate the continuous monitoring of location. It is assumed that the degree of familiarity with the field is the crucial factor in the rat’s response, and its behavior is labeled accordingly. Thus, with no prior experience in the situation, the amount of sniffing observed during a 10-min trial is said to be an index of exploration (Goodrick, 1967), and amount of ambulation during 2-min daily trials is reported to be inversely related to intragroup rank in emotionality (Hall, 1936). When locomotion is to be classified as general activity, it would seem appropriate to lengthen the test period considerably, with sufficient habituation to insure a stable baseline before the critical observations are made.

(2) Combining Observations

Even with the economy afforded by judicious sampling, observation is impracticable as the sole source of information in a long-range or multi-subject study. A compromise we have sometimes adopted is continuous photocell recording supplemented by direct observation on selected days (Finger, 1969). The simultaneous use of sampling and an automated recording system, incidentally, offers a sort of validation procedure for the latter. This, together with the reliability of operation and systematic relation to the independent variables, could be the basis for deciding which of the stabilimeter and stationary-cage techniques is most adequate for quantifying the effects of neurological manipulation.

V CONCLUSIONS

It should be clear to the reader that measures of general activity can be so distorted by irrelevant variables that they are sometimes of questionable value. By observing a few simple precautions, however, the careful experimenter can sufficiently reduce the variability so that he will have a powerful tool for the assessment of the neurophysiological state.

When examining several values of a parameter, he will, if feasible, use a within-groups design, controlling for possible interactions with order, age, and experience in the apparatus. Group matching, when called for, should take into account the potential contribution of age, sex, strain, litter, experience, and activity level. It is desirable that the recording instruments be equated by calibration and/or by balanced assignment across conditions. The interpretation of treatment effects will be most meaningful if a stable pretreatment baseline has been established after adequate habituation to rigorously maintained conditions of illumination, visual distraction, noise, temperature, feeding, and handling. Only in emergencies should a deviation from this regimen be permitted, and unless the interaction effects can be estimated, the contaminated data ought to be discarded. Except when the treatment is transitory, it is best that the observations continue over several days, optimally with some analysis carried out of the diurnal distribution of activity. Of course it is always essential that adequate cognizance be taken of the ubiquitous influence of circadian rhythmicity.

There is still the effect upon one’s results of the type of measuring device, and the uncertainty of how this may best be dealt with. For testing the effect of brain interference, the running wheel seems a logical choice, in view of its mechanical simplicity and the demonstrated sensitivity of running to physiological and environmental manipulations. Which of the other methods of automatic recording should be adopted as a complement is equivocal and perhaps rests upon the investigator’s judgment of technical feasibility and preliminary comparisons with concurrent samples of direct observation. The meaning of the discrepancies among measures is still too obscure to dictate the choice of one’s apparatus or to suggest neurological sites of probable relevance. The hope, rather, is that the research of the neuropsychologist will add a new dimension to the categorization of general activity, and suggest functional links between general activity and other patterns of behavior.

ACKNOWLEDGEMENT

The preparation of this chapter, as well as much of the research on which it is based, was facilitated by Grant 04920 by the United States Public Health Service. I am in debt to many of my colleagues, past and present, for help in framing some of the central questions and seeking their empirical answers.

REFERENCES

Anderson, O. D., Parmenter, R. Psychosom.