This dissertation has bean 6 6 -1 8 6 8 microfilmed exactly as received YUTZEY, David Alan, 1938- CHANGES IN EMOTIONALITY FOLLOWING SIMULTANEOUS LESIONS OF THE SEPTAL REGION AND LIMBIC CORTEX.

The Ohio State University, Ph.D., 1965 Psychology, experimental

University Microfilms, Inc., Ann Arbor, Michigan Copyright by David Alan Yutzey 1966 CHANGES IN EMOTIONALITY FOLLOWING SIMULTANEOUS

LESIONS OF THE SEPTAL REGION

AND LIMBIC CORTEX

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

David Alan Yutzey, B. A., M. A.

*******

The Ohio State University 1965

Approve*

Adviser Department of Psycho' ACKNOWLEDGMENTS

The author gratefully acknowledges his adviser, Professor Donald

R. Meyer, for his aid and encouragement in all phases of the present study. 1 also wish to thank Professors William C. Howell and Raymond

C. Miles, members of my reading committee, for their helpful comments concerning the early draft of this dissertation. Finally, to Dr.

Patricia M. Meyer, for her participation in the rating of the animals and her suggestions during the conduct of the experiment, and to Mr.

John Lauber, for his assistance in preparing the histological mate­ rials, I wish to express my appreciation.

The author was supported under National Institute of Health

Training Grant MH-6748 during the course of this research.

ii VITA

July 31, 1938 Born - Glendale, West Virginia

1960 ...... B. A., Ohio Wesleyan University, Delaware, Ohio

1960-1961 . . Research Assistant, Laboratory of Aviation Psychology, The Ohio State University Research Foundation, Columbus, Ohio

1961-1965 . . National Institute of Health Training Fellow, Laboratory of Comparative and Physiological Psychology, The Ohio State University Research Foundation, Columbus, Ohio

1963 ...... H. A., The Ohio State University, Columbus, Ohio

1963-1964 . . Assistant Instructor, Department of Psychology, The Ohio State University, Columbus, Ohio

PUBLICATIONS

"Precedence effects in discrimination learning by normal and frontal monkeys." J. comp, physiol. Psychol.. 1964, 58, 472-474. (with Meyer, D. R . , Treichler, F. R. and Meyer, Patricia M.)

"Emotionality changes following septal and neocortical ablations in rats." J. comp, physiol. Psychol.. 1964, 58, 463-465. (with Meyer, Patricia M. and Meyer, D. R.)

"Effects of neocortical ablations on relearning of a black-white dis­ crimination habit by two strains of rats." J. comp, physiol. Psychol. (in press), (with Meyer, D. R., and Meyer, Patricia, M.)

iii FIELDS OF STUDY

Major Field: Physiological Psychology

Studies in emotionality and learning after lesions of the neocortex and limbic system. Professor Donald R. Meyer

Studies in discrimination learning and deficits in learning after lesions of the frontal neocortex in monkeys. Professor Donald R. Meyer

Studies in sequential behavior in several species and after lesions of the frontal cortex. Professor Raymond C. Miles

Studies in decision making and information processing behavior. Professor George E. Briggs

iv CONTENTS

Acknowledgments ...... 11

Vita - Publications...... iii

Fields of S t u d y ...... iv

Introduction ...... 1

Method ...... 5

R e s u l t s ...... 7

D i s c u s s i o n ...... 10

Appendix I. Statistical Analysis and Average Emotionality Scores . 12

Appendix II. Analysis of Thalamic Degeneration and Discussion . . 20

R e f e r e n c e s ...... 23

v TABLES

Table

1. Analysis of Variance for Groups, Days, and Groups by Days Interaction Effects ...... 14

2. Analysis of Variance for Differences between Groups on Day 1 of Post-operative Ratings ...... 15

3. Analysis of Variance for Differences between Groups on Day 2 of Post-operative Ratings ...... 15

4. Newman-KueIs Studentized Range Tests on Differences between Pairs of Means on Day 1 of Post-operative Ratings ...... 16

5. Maim-Whitney U Tests between Pairs of Means of Interest . . . 17

6. Mean Emotionality Ratings for All Groups by D a y s ...... 18

7. Median Emotionality Ratings for All Groups by D a y s ...... 19

vi INTRODUCTION

A forebear of much of the current research on the neural correlates

of emotional behavior is the theoretical paper by James W. Papez (1937)

entitled "A proposed theory of emotion." Based primarily on anatomical

considerations, the "Papez theory of emotion" suggested that the limbic

system of the forebrain, a group of interconnected structures previously

regarded as functionally related to olfaction, had an equally important

role in emotional behavior. Within a decade, the effect of this proposal was evident both in a revival of theoretical interest in the limbic

system and in the advent of several programs of experimental research designed to investigate the effects of destruction or stimulation of various components of the system upon emotional behavior.

Some of the most valuable discoveries in this field were made in a series of experiments by Bard and Mountcastle (1948) upon the neural

correlates of emotional behavior in cats. These workers found that a

complete neocortical ablation produced a placid animal, but that a

subsequent lesion of the old cortex, either the transitional cortex of

the midline or the pyriform-amygdaloid complex, led to a complete rever­

sal of Sjs response tendencies. Cats with neocortical ablations could be roughly handled without danger to the experimenter, but after the

second lesion, these animals displayed extreme rage at the slightest provocation. The authors' interpretation of this phenomenon was that

1 2

the neocortex normally acted as a facilitator of emotional behavior and

that the function of the old cortex was to inhibit this phylogenetically

newer system. Although the implications of the Bard and Mountcastle

study for a theory of emotion were significant, of equal importance was

the demonstration of the usefulness of the sequential lesion procedure.

Using this method, a behavior tendency produced by one lesion could be

cancelled or even completely reversed by a second ablation of a function­ ally antagonistic system.

Using the sequential lesion procedure as a research tool, several investigators began to study other functional relationships within the limbic system. Of clinical as well as theoretical interest was the possibility of surgically taming an animal in which a prior lesion had produced a propensity for angry behavior. One such hyperemotional prep­ aration was the septal rat (Brady and Nauta, 1953; King 1958, 1959) which exhibited striking hyperreactivity in response to tactile or audi­ tory stimulation. On the basis of research in which lesions of the amygdala were found to dampen emotional reactivity, King and Meyer

(1958) suspected that septal hyperemotionality could be reduced by lesions of the amygdala. These workers found that the septal syndrome was indeed suppressed inmediately following bilateral destruction of the antagonistic system. Acting upon the suggestion of the King and Meyer experiment, that the removal of a facilltory system could reduce septal hyperemotionality, Yutzey, Meyer, and Meyer (1964) produced both sequen­ tial and simultaneous lesions of the septal region and of the neocortex, the structure which when completely removed in cats, had produced 3

placidity in the Bard and Mountcastle experiments. Due to the fact that

a relatively long (21-days) recovery period was used in this experiment,

animals with septal lesions had returned to normal levels of emotional­

ity by the time the surgical removal of the neocortex was accomplished, and Yutzey, Meyer, and Meyer were unable to obtain results comparable with the King and Meyer septal-amygdaloid study. However, an unexpected

finding by the former workers was that animals with simultaneous septal-

complete neocortical ablations were just as hyperemotional as rats with

septal lesions observed within two days following surgery. In other words, the neocortical ablations apparently prevented the “spontaneous" attenuations of septal hyperemotionality during the 21-day recovery period. Since this first experiment, these investigators have also obtained maintained states of hyperemotionality with simultaneous septal- anterior neocortical and -posterior neocortical ablations in which less than 50% of the neocortex was removed (Meyer, Yutzey, and Meyer, in preparation).

These results raised the question of whether the phenomenon of unattenuated hyperemotionality after the removal of the septal region and the neocortex could be replicated with lesions of other structures which, when destroyed alone, produced calming effects. Anatomical and functional similarities between limbic and neocortices suggested that comparable effects upon emotional behavior could be obtained with mid­ line cortex. Like the neocortex, the anterior cingulate (Area 24), posterior cingulate (Area 23), and the retrosplenial (Area 29 and 30) cortices are richly supplied with afferents from the thalamus, 4

respectively the anteromedial, anteroventral, and anterodorsal nuclei

(Rose and Woolsey, 1948). In addition, on the basis of several anatom­

ical methods of classification, the limbic or juxtallocortex more closely

approximates the structural characteristics of the neocortex than any

other rhinencephalic system (Cf. Pribram and Kruger, 1954), Finally,

in several behavioral studies, cingulate lesions have produced increased

tameness in monkeys (Smith, 1944; Glees, Cole, Whitty, and Cairns, 1950)

and in cats (Bard and Mountcastle, 1948), although in the latter investi­

gation reduced emotional reactivity was not consistently obtained.

On the basis of the foregoing considerations, the present experiment was designed to test the notion that the limbic and neocortices might

similarly affect functional systems for the display of emotion. More

specifically, the hypothesis of the investigation was that, after a 21-

day recovery period, the emotional reactivity of animals with combined

limbic cortex-septal lesions would be at significantly higher levels

than that of rats with septal lesions alone. METHOD

The Ss were 98 male, hooded rats from the Ohio State University

colony, 90-120 days old at the beginning of the experiment. During all

phases of the study Ss were individually caged and were isolated in a

photographic darkroom which was entered only for experimental procedures

and for weekly maintenance and cleaning. This isolation area measured

11 x 7% x 9 feet, was constantly illuminated by a low level incandes­

cent source, and was ventilated by the laboratory air-conditioning

system which also served to partially mask noise from external sources.

Emotionality was rated independently by two observers, whose scores

correlated .92. The emotionality rating procedure used was that devised

by King (1958) in which each _S was evaluated on (a) reaction to a pencil presented close to the snout, (b) response to a light tap on the back with the pencil, (c) resistance to capture, (d) resistance to handling,

(e) vocalization during capture and handling, (£) urination and defeca­

tion in reaction to capture and handling. Each £ was scored from zero

to five points on all categories except for the last one which ranged

from zero to three. The sum of scores for all categories represented

S/s emotionality rating for a particular day.

After daily ratings of emotionality had been made for six days,

eight groups of animals were formed. The Ss were assigned to these

groups by matching them on their scores for the first day of emotional­

ity ratings. On the seventh day of the experiment, Ss were surgically 6 operated according to their group memberships. The Ss In Groups CS, RS, and CRS received simultaneously performed lesions of the septal region

In combination with bilateral ablations of either the cingulate cortex, retrosplenial cortex, or both areas. Three additional groups of animals,

Groups C, R, and CR, were given bilateral ablations of cingulate cortex, retrosplenial cortex, or both areas alone. In the surgical preparation of Group DS, removal of an area of the neocortex 2 mm. wide and extend­ ing anteriorily to the frontal pole and posteriorily to the caudal edge of the hemispheres and a lesion of the septal region were simultaneously performed. The medial extent of the neocortical ablation was limited to within 2 mm. of the midline in order to avoid invasion of the limbic cortex. A final group, Group S, had lesions of the septal region alone.

Following surgery, all groups were allowed to recover for 21 days. After this recovery period, ratings of emotionality were carried out for six days.

All cortical ablations were performed by the aspiration technique after removal of the skull and incision of the dura directly over the intended area of ablation. Septal lesions were stereotaxically placed and were made by electrocoagulation. After the post-operative observa­ tions were completed, all animals were perfused with 10 per cent formalin, the brains were embedded in celloidin, serially cut and stained with cresyl violet. Finally, histological reconstructions of the lucus and extent of damage to the cortical areas or to the septal region, and of the amount of degeneration in the thalamic projection areas were carried out. RESULTS

Mean and median emotionality ratings across experimental days for all groups are presented in Tables 6 and 7 of Appendix 1. From these tables it is evident that preoperatively all groups were nearly identical in average emotionality on the first day of rating and subsequently stabilized at similar levels by the third day of observa­ tions .

A complete summary of the results of the statistical analysis has been tabulated and discussed in Appendix 1. Although the groups, days, and groups by days effects were all statistically significant in the overall analysis of variance (Table 1), subsequent one-way analyses of the groups effect on Days 1 and 2 of the post-operative emotionality ratings showed that by the second day no between groups difference was present (Tables 2 and 3). Therefore, the data points of major interest in the present study are the group emotionality ratings obtained on the first day of testing after the animals had been surgically operated and allowed to recover for 21 days.

With respect to the first day of post-operative emotionality ratings, when compared with the control group with a septal lesion alone, Group S, all of the groups with ablations of the limbic cortex combined with a septal lesion, Groups CS, RS, and CRS, were at signif­ icantly higher levels of emotionality after the 21-day recovery period as indicated by both the Newman-Kuels tests on ordered means (Table 4) and the Mann-Whitney U tests (Table 5). However, the average of Group

DS, although nearly as high as the combined limbic cortex-septal lesioned groups, was significantly different at the .05 level from the animals with septal lesions alone by the Newman-Kuels but not by the Mann-

Whitney U test. Next, in comparing the three groups with ablations of the limbic cortex combined with septal lesions and their respective control groups with lesions of the limbic cortex alone, the differences between Groups RS and R and between Groups CRS and CR were statistically significant, but the comparison between Groups CS and C did not meet the .05 probability requirement (both tests). Finally, the emotionality ratings for Group C, animals with ablations of the cingulate cortex, and Group S, Ss with septal lesions, were also not statistically dif­ ferent on the first post-operative day.

The histological analysis of the brain materials revealed that, in general, lesion placements were in the designated areas, although most of the ablations of the limbic cortex were not as extensive as had been intended. The septal lesions involved 80-100% of the septal region with sparing most commonly noted in the ventrolateral portion of the lateral nuclei. Because of the displacement of the defect remaining after the limbic cortex had been removed by adjacent undamaged tissue, lesions of the old cortex often appeared to be excessively limited in extent. However, a more accurate estimate of the amount of damage to these structures could be obtained by noting the quantity of remaining tissue superior to the callosal sulcus, the degree of distortion to the corpus callosum Itself, and the extent of degeneration In the anterior thalamic nuclei. By these criteria, the losses of limbic cortex sus­ tained by animals of all groups were judged to range between 40-80% of the intended areas of ablation. In each of the groups with combined limbic cortex-septal lesions, the extent of damage to the old cortex was approximately equal to that of the respective control groups with ablations of the limbic cortex alone. With respect to Group DS, excepting three animals with bilateral asymmetry in lesion size, the neocortical strip lesions corresponded closely in locus and extent to the intended areas of ablation.

The histological analysis of thalamic degeneration not only served to confirm the accuracy of lesion placement for the purpose of support­ ing the behavioral conclusions of the present study, but also furnished additional data with respect to several unresolved anatomical questions.

Therefore, these results have been presented in detail and discussed in

Appendix II. DISCUSSION

The results of the present experiment verify the prediction that

lesions of the limbic cortex, when produced simultaneously with septal

lesions, prevent the attenuation of septal hyperemotionality after a

21-day recovery period. Therefore, the old and new cortex appear to be equipotential in their functional relationship to the limbic system with respect to the course of recovery from states of hyperemotionality.

A more puzzling result is the intermediate mean emotionality rating for animals with anterior cingulate ablations, Group C, which was not

significantly different from either septal operatees, Group S (£” .078), nor rats with combined cingulate-septal lesions, Group CS (£-.068). On the basis of several recent studies, a more definitive outcome would have been predicted. First, a reciprocity of function has been noted in avoidance behavior such that animals with septal lesions show improved performance in an active avoidance task and are deficient in a passive avoidance task, whereas precisely the opposite is true in animals with anterior cingulate ablations (King, 1958; Peretz, 1960;

McCleary, 1961). Secondly, since direct connections are known to exist between the septal and anterior cingulate regions (Powell, 1963), the double dissociation obtained in the two types of avoidance tasks could be interpreted as partially due to the releasing of the function of one system after the antogonistic system had been removed. On the basis of 11 this evidence, therefore, one would have expected the ablation of the anterior cingulate cortex to produce a taming effect.

Finally, although the mean emotionality rating of 10.64 for Group

DS is similar to the means of the groups with combined limbic cortex- septal lesions, the question of whether ablations of 25% of the cortex are effective in maintaining septal hyperemotionality over a 21-day recovery period has not been definitely answered. Comparing, the present experiment with the previous studies in which 40-100% of the neocortex was removed in conjunction with a septal lesion (Yutzey, Meyer, and

Meyer, 1964; Meyer, Yutzey, and Meyer, in preparation), we suspect that a lesion of one-fourth of the neocortex approaches the lower limit of neocortical mass which is necessary for the maintenance of septal hyperemotionality. APPENDIX I

STATISTICAL ANALYSIS AND AVERAGE EMOTIONALITY SCORES

The tables presented In this section constitute a complete summary of the statistical analysis of the emotionality rating data. In addi­ tion, the final two tables, Tables 6 and 7, present the mean and median values for the emotionality ratings of all groups over pre- and post­ operative days. The following few paragraphs briefly explain the rationale of the statistical analysis.

Since the samples did not appear to deviate seriously from normal­ ity and were not highly skewed as judged from a comparison of the mean and median values, parametric tests of the data were first computed.

The overall analysis of variance with groups and days as factors resulted in significant differences between groups, days, and groups by days interaction effects. Cochran Fm ay tests performed upon the error terms of this analysis rejected the hypothesis of heterogeneity of variance at the .05 level of significance (See Table 1).

Next, two single-factor analyses of variance were computed for the first and second post-operative days of the experiment. In both cases Cochran Fmav tests showed the variances to be homogeneous at the

.05 level. On Day 1 the differences among groups were significant at the .005 level, but on the second day the groups effect was found to be non-significant (See Tables 2 and 3). These results indicated not only

12 13 that differences between groups had disappeared by the second day of post-operative ratings but also that the significant groups by days

Interaction obtained in the overall analysis of variance was primarily due to the differences between the scores on Day 1.

The final parametric test was a comparison between pairs ofordered means on the first post-operative day by the Newman-Kuels procedure.

The results of this test, the significant differences at both the .01 and .05 levels, are presented in Table 4.

Although F tests are generally regarded as robust with respect to minor violations of the assumptions, because the measure of emotionality was based on an ordinal scale at best, several paired comparisons of interest on the data of the first post-operative day were computed non- parametrically. One of the most powerful of these tests is the Mann-

Whitney U test, but since this test assumes independent sampling, and since in the present experiment the groups were matched on their pre- operative scores, before the U test could be legitimately applied to the data, some evidence that the ratings before and after surgery were unrelated was needed. Accordingly, Spearman rank-order correlations between the Day 1 pre- and post-operative scores were computed for each group, and since only one of the eight correlations was significant, the assumption of independence between groups was thought to be justi­ fied. The selected Mann-Whitney U's and the associated probabilities are presented in Table 5. With the exception of the comparison between

Groups DS and S, the results are identical to those obtained with the

Newman-Kuels procedure. 14

Table 1. Analysis of Variance for Groups, Days, and Groups by Days Interaction Effects

Source of Variation SS df MS F £

Between Ss 1340.71 97

G (Groups) 276.83 7 39.55 3.35 .025

Ss within G 1063.88 90 11.82

Within Ss 2020.87 490

D (Days ) 693.57 5 138.71 82.56 .005

GD 571.20 35 16.32 9.71 .005

D by Ss within G 756.10 450 1.68

Total 3361.58 587

Cochran Fmax Tests for Homogeneity of Variance for Ss within G and D by Ss within £ Terms

Variance ijnax £

Ss within G (8, 12) .2695 N.S.

D by S^s within G (8, 60) .1788 N.S. 15

Table 2, Analysis of Variance for Differences between Groups on Day 1 of Post-operative Ratings

Source of Variation SS df MS IE

Groups 324.51 7 46.36 5.82 .005

Error 716.17 90 7.96

Total 1040.68 98

Cochran Imax Test for Homogeneity of Variance of Error Term

.Umax (8, 13) - .2225 N.S.

Table 3. Analysis of Variance for Differences between Groups on Day 2 of Post- operative Ratings

Source of Variation SS df MS F E

Groups 49.10 7 7.01 1.89 N.S.

Error 332.58 90 3.70

Total 381.68 98

Cochran Fj^y Test for Homogeneity of Variance of Error Term

Fmax (8, 13) = .2053 N.S. 16

Table 4. Newman-Kuels Studentized Range Tests on Differences between Pairs of Means on Day 1 of Post'Operative Ratings

Groups R CR S C DSCRS CS RS

Ns 11 13 12 12 10 13 14 13

Means 6.80 7.62 7.75 9.68 10.64 10.92 11.64 11.65

R — * *** **

CR — ** *

S * * **

C

DS

CRS

CS

RS

* Null hypothesis rejected at the .05 level ** Null hypothesis rejected at the .01 level Table 5. Mann-Whitney IJ Tests between Pairs of Means of Interest

Pairs of Means u £

CS and S 141.0 .003**

RS and s 130.5 .004 **

CRS and s 118.5 .028 *

DS and s 83.5 .121

CS and C 113.0 .068

RS and R 126.0 .002

CRS and CR 128.0 .026*

C and s 102.5 .078

* Null hypothesis rejected at the .05 level ** Null hypothesis rejected at the .01 level 18

Table 6. Mean Emotionality Ratings for All Groups by Days

P R E - 0 P E R A T I V E DAY S 1 2 3 4 5 6

CS 10.69 7.86 6.69 6.39 6.45 6.27

C 11.43 8.08 7.47 6.83 6.06 6.13

RS 10.50 6.93 6.34 6.34 6.12 6.03

R 11.22 7.45 5.82 5.90 5.99 5.88 Groups CRS 10.42 6.58 6.25 5.98 6.10 5.69

CR 10.92 7.68 6.45 6.12 5.74 6.00

DS 10.78 8.04 6.50 6.37 6.43 6.21

S 10.78 6.88 6.19 5.79 5.93 5.49

P 0 S T - 0 P E R A T I V E DAY S 1 2 3 4 5 6

CS 11.64 7.37 6.77 6.66 6.53 6.35

c 9.68 6.88 6.34 5.98 5.87 5.73

RS 11.65 7.65 6.33 6.05 5.85 5.65

R 6.80 6.03 5.64 5.47 5.81 5.80 Groups CRS 10.92 6.98 6.87 6.02 6.06 5.85

CR 7.62 6.03 5.78 5.73 5.75 5.44

DS 10.64 7.29 6.24 6.30 6.05 6.76

S 7.75 5.94 6.01 5.38 5.58 5.29 19

Table 7. Median Emotionality Ratings for All Groups by Days

P R E - 0 PER AT I V E DAY S 1 2 3 4 5 6

CS 11.25 7.10 6.30 6.00 6.30 6.30

c 12.23 7.60 6.50 5.85 5.85 5.70

RS 10.00 6.60 6.65 6.00 6.00 5.60

R 11.90 7.30 5.55 5.70 5.75 5.60 Groups CRS 11.00 6.40 5.80 5.80 5.80 5.60

CR 11.10 7.50 5.50 6.20 5.60 5.80

DS 11.33 7.15 6.15 6.05 5.90 6.30

S 11.00 7.15 6.10 5.95 6.00 5.30

P 0 S T - 0 PERA T I V E DAY S 1 2 3 4 5 6

CS 11.45 6.40 5.78 5.75 6.05 5.53

C 9.83 6.40 6.10 5.83 5.55 5.50

RS 11.05 7.05 5.50 5.50 5.60 5.50

R 6.40 5.90 5.60 5.40 5.40 5.40 Groups CRS 11.05 6.45 6.00 5.55 5.70 5.50

CR 6.70 5.80 5.30 5.30 5.30 5.20

DS 10.40 5.75 5.65 5.85 5.43 5.32

S 7.00 5.63 5.53 5.55 5.30 5.35 APPENDIX II

ANALYSIS OF THALAMIC DEGENERATION AND DISCUSSION

The ablations of the limbic cortex in the present experiment were

identified and performed according to the atlas proposed by Krieg

(1948). By this scheme, an ablation of the midline cortex extending from the frontal pole to a point approximately 2 mm. posterior from

the bregma included Krieg*s Areas 23 and 24 and was labeled a cingulate

(C) lesion. Similarly, removal of the limbic cortex from this point posterior to the confluence of sinuses, Krieg*s Areas 29b and 29c, was defined as a retrosplenial (R) lesion. However, on the basis of the present histological results, it appears that the anatomy of these limbic-cortical structures in the rat was more accurately known by

Lashley (1941), and was perhaps most adequately described by the maps of the rabbit constructed by Rose and Woolsey (1948).

In the rabbit, Rose and Woolsey identified the anterior cingulate cortex (their anterior limbic region) as a structure lying on the medial wall of the cerebral hemisphere and extending superior and anterior from the corpus callosum. The posterior cingulate cortex (their posterior limbic region) adjoins the anterior limbic region and extends poste­ riorly to the caudal edge of the hemisphere. This latter structure is approximately equally represented in the rabbit on the dorsal and medial surfaces of the cerebral mantle. The retrosplenial cortex lies directly

20 21

ventral on the medial wall to the posterior limbic region and terminates

at the corpus callosum. These three regions, the anterior and posterior

limbic, and the retrosplenial, were found by these workers to project respectively to the anteromedial, anteroventral, and anterodorsal nuclei

of the thalamus.

In the present experiment, the histological data suggested that

the thalamo-cortical connections in the rat are similar to those found

in the rabbit by Rose and Woolsey. On the one hand, lesions of the

cingulate cortex were associated equally with degeneration of either or both the anteromedial and anteroventral nuclei (Groups CS and C) .

On the other hand, the intended retrosplenial ablations were most com­ monly accompanied by degeneration in the anteroventral nucleus (19 cases), but in only six cases in the anterodorsal nucleus, and just once in the anteromedial nucleus (Groups RS and R ) . In the latter preparations, cell loss and gliosis was found in the principle portion of the lateral thalamic nucleus in over 607. of the cases, suggesting that some inci­ dental damage to motor or visual neocortex may have occurred. In groups with both lesions, Groups CR and CRS, both the anteromedial and antero­ ventral nuclei usually degenerated (21 cases) but in only eleven in­ stances were any changes noted in the anterodorsal nucleus. In all groups where degeneration was noted in the anterodorsal nucleus, the lesions were among the most extensive and involved the tissue lying dorsally adjacent to the posterior callosal sulcus. These data suggest the conclusion that the groups with "C" lesions suffered damage pri­ marily to the anterior cingulate cortex and only incidentally to the 22 posterior cingulate cortex, and that the "R" lesions actually included

the greater part of the posterior cingulate cortex with occasional involvement of the retrosplenial cortex.

Finally, with respect to the groups without ablations of the limbic

cortex, the following results were obtained upon examination of the brains. In Group S, animals with septal lesions, no degenerative changes

in the thalamic nuclei were found. Group DS, rats with neocortical strip ablations combined with septal lesions, had extensive degeneration in

the lateral thalamus and the lateral geniculate bodies, the primary pro­ jection areas to the medial-posterior quadrant of the neocortex and, in only two cases were any changes noted in the anterior nuclei. No evi­ dence of any degeneration of the medial dorsal nucleus were found, even though this portion of the thalamus has often been posited as the pro­ jection area for the medial-anterior quadrant of the rat neocortex. REFERENCES

Bard, P., and Mountcastle, V. B. Some forebrain mechanisms involved in expression of rage with special reference to suppression as behavior. Res. Publ. A s s . nerv. ment. Pis.. 1948, 27, 362-404.

Brady, J. V. , and Nauta, W. J. H. Subcortical mechanisms in emotional behavior; Affective changes following septal forebrain lesions in the albino rat. J. comp, physiol. Psychol., 1953, 46, 339-346.

Glees, R. , Cole, J., Whitty, C. W. M . , and Cairns, H. The effect of lesions in the cingular gyrus and adjacent areas in monkeys. J. Neurol. Neurosurg. Psychlat.. 1950, 13, 178-190.

King, F. A. Effects of septal and amygdaloid lesions on emotional behavior and conditioned avoidance responses in the rat. J. nerv. ment. Pis., 1958, 126, 57-63.

King, F. A. Relationship of the "septal syndrome" to genetic differences in emotionality in the rat. Psychol. Rep., 1959, 5, 11-17,

King, F. A., and Meyer, P. M. Effects of amygdaloid lesions upon septal hyperemotionality in the rat. Science, 1958, 128, 655-656.

Krieg, W. J. S. Accurate placement of minute lesions in the brain of the albino rat. Quart. Bull., Northwestern Univer. Med. School. 1946, 20, 199-208.

Lashley, K. S. Thalamo-cortical connections of the rat's brain. J. comp. Neurol.. 1941, 75, 67-121.

McCleary, R. A. Response specificity in the behavioral effects of limbic system lesions in the cat. J. comp. physiol. Psychol., 1961, 54, 605-613.

Meyer, P. M . , Yutzey, D. A., and Meyer, P. R. Effects of simultaneous septal-neocortical lesions upon emotionality and relearning of a black-white discrimination. (in preparation)

Papez, James W. A proposed mechanism of emotion. Arch. Neurol. Psychiat., 1937, 38, 725-743.

23 24

Peretz, E. The effects of lesions of the anterior cingulate cortex on the behavior of the rat. J. comp, physiol. Psychol., 1960, 53, 540-548.

Pribram, K. H. and Kruger, L. Functions of the "olfactory brain." Ann. N. Y. Acad. Sci., 1954, 58, 109-138.

Powell, E. W. Septal efferents revealed by axonal degeneration in the rat. Exp. Neurol.. 1963, 8, 406-422.

Rose, J. E. and Woolsey, C. N. Structures and relations of limbic cortex and anterior thalamic nuclei in rabbit and cat. J. comp. Neurol., 1948, 89, 279-348.

Smith, W. K. The results of ablation of the cingular region of the cerebral cortex. Fed. Proc.. 1944, 3, 42.

Yutzey, D. A., Meyer, P. M., and Meyer, D. R. Emotionality changes following septal and neocortical ablations in rats. J. comp. physiol. Psychol.. 1964, 58, 463-465.