Effects of caudate nuclei or frontal cortical ablations in kittens: Neurology and gross behavior

EXPERIMENTAL

Effects

JAIME

R.

KEUROLOGY

of Caudate in Kittens: VILLARLANCA,

61, 615-634

(1978)

Nuclei or Frontal Cortical Ablations Neurology and Gross Behavior CHARLES E. OLMSTEAD, AITDROBERT J. MARCUS~

Dcpartmcnts of Psgchiatry awl School of Medicine, Ullizwsity

MICHAEL

.4uatovlg, Mcutal Retardation of California, Los Arlgclcs,

Rcscarch California

S. LEVINE,

Cmter, 90024

Kittens with a one-stage ablation by aspiration of the caudate nuclei were compared to kittens with bilateral removal of the frontal cortical regions, sham-operated animals, and intact littermates. Surgery was done between 9 and 36 days of age and more than 505% of the subjects were studied through adulthood. After surgery, most caudate-ablated kittens showed a visual and auditory stereotyped “compulsory approaching syndrome” with exaggerated visual tracking and motor activity. This was similar to, but less marked, than that seen in adults. Other components of the adult syndrome, such as exaggerated forelimb treading, marked purring, rooting, exaggerated tactile approach, and sexual changes, began to appear when the kittens were 3 to 4 months of age and peaked at puberty. Kittens with frontal or sham operations did not significantly show these changes. All subjects with lesions were remarkably free of gross neurologic deficits except for defective paw usage and, in the kittens with the caudate lesion, impoverishment of movement. Both groups with lesions showed a significant delay in the development of the limb contact placing reactions with acaudate kittens showing a longer delay than those with frontal cortex ablations. In brief, neonatal caudatectomy produced qualitative effects similar to those after caudate ablation in adults and, as in the adults, these were different from those resulting from frontal removals. However. there were marked differences in the time course and the magnitude of the effects. At least three variables were found to influence the consequences of neonatal brain damage demonstrated here : Age at surgery, age at testing, and cortical versus subcortical site of the lesion. 1 This research was supported by U.S. Public Health Service grants HD-05958. MH-07097, and HD-04612. We wish to thank Dr. D. I,. Avery for his participation in the early stages of the research and P. Atkinson and S. McAdam of the UCLA Mental Retardation and Child Psychiatry Media Unit for their assistance in the illustrations and filming. 615 0014-4886/78/0(;13-oGl~$OZ.OO/O All

Copyright @ 1978 rights of reproduction

by Academic Press, Inc. in any form reserved.

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INTRODUCTION This is the first of a #series of papers reporting behavioral and neurological studies in kittens with large lesions of the caudate nucleus or frontal cortex. The experiments are an extension of similar studies in adult cats (21, 32-34). There were several reasons for extending our work to developing animals. First, we were interested in studying the consequences of brain damage sustained early in life upon the course of development and final status of neurologic and behavioral landmarks (36). Second, we wished to compare the effects of neonatal caudate or frontal ablations with those of similar lesions in our adult cats (21, 32-34). Early experimental work in this field suggested that the effects of neonatal brain lesions are governeNd by rather simple rules. For example, an important conclusion of the classical work of Kennard in monkeys (12, 13) was that similar cortical lesions cause less impairment if inflicted in infancy than if sustained in adulthood. Based on this as well as on other investigators’ data, Teuber (27) introduced the “Kennard principle” according to which “the time to have one’s cortical lesion, if one could arrange it, would be early” (in life). Teuber (27, 28) and others (8, 10, 11, 16) however, indicated that additional variables may be involved. Factors such as the age at testing (9, 10, 14, 15), the task used (11, 28, 29), and the cortical versus subcortical nature of the lesion (11, 16) have been reported. We are particularly interested in evaluating the relative importance of these and of other possible variables which may affect the outcome after neonatal brain damage. Third, our previous work in adult cats (32-34) demonstrated that extensive caudate ablation produces effects which are not readily apparent after the more frequently performed smaller lesions. Those experiments also permitted a differentiation between the consequence of lesions in the frontal cortical regions and the caudate nuclei (21, 32-34). Because these observations have implications for the physiology of the basal ganglia, their eventual replication and extension to kittens would considerably strengthen our conclusions in the adult cats. It was suggested that the role of the caudate might be different in the neonatal period, compared to adulthood, especially in explaining the sparing of behavioral deficits after frontal damage (9, 10). It was also proposed that at this early age the caudate might be functionally equipotential with the frontal cortex (6). Finally, a ‘search of the literature produced no caudate nuclei lesion studies in kittens and only a few studies concerning the effects of frontal cortical lesion at that age (1, 3, 7). The present paper reports on neurologic and some behavioral effects and these should be considered together with results described in ensuing reports have been published (2, 20, 31, 3.5, 37). papers. Preliminary

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XETHODS The experiments were carried out in 69 kittens of either sex (Table 1) : 17 with bilateral caudate lesions (acaudate preparations), 12 with bilateral ablation of the frontal cortices (afrontal preparations), 7 sham-operated, and 33 intact littermates. The age at surgery was between 9 and 36 postnatal days. All kittens were offspring of pound-derived animals and, therefore, were part of a “randomly bred” population. All were reared in the colony of the University of California at Los Angeles Mental Retardation Research Center and came from term pregnancies. They were kept in whelping cages (SZ X 112 x S4 cm) with their mothers until 56 days of age, then they were housed in groups of as many as seven animals in larger cages (120 x SS x 16s cm). At about 4 months of age, they were moved to individual standard laboratory cat cages. All received standard vaccinations (36) between 53 and Sl days of age. The animals were weaned onto a diet of wet canned chicken or tuna fish once daily and had ad libitlln~ access to Purina Cat Chow. Their weights were monitored daily prior to and after surgery and differences in growth between groups (Fig. 3) were statistically compared [analysis of variance and Newman-Keuls test (38) 1. Surgical Procedures. Surgery was done under combined chlorpromazine (5 mg/kg) and pentobarbital (11 to 15 mg/kg) anesthesia plus hypothermia. The kitten was placed in a special stereotaxic head holder. Sparing the saggital sinus, a large portion of the dorsal skull was removed and the flap was preserved in warm saline. The dura was opened. A 3-111111 wide spatula was positioned with a sterotaxic carrier between one cerebral hemisphere and the midline falx and was used to gently retract the hemisphere. Using a thin glass pipet for suction, a small opening was made in the gyrus cinguli just below the midline cruciate sulcus. The corpus callosun was then penetrated, thereby gaining access to the lateral ventricle and exposing dorsomedial aspects of the caudate head. A fiber optic head light and the experience gained in adult cats were useful in visualizing the caudate in young kittens in which both color and consistency differences between white and gray matter are less marked than in adults. To complete the bilateral ablation, the lower edge of the falx was cut and the caudate lesion was made contralaterally. In sham-operated kittens all steps were carried out except for caudate aspiration. For the frontal ablations, a more anterior bone flap was removed and most brain tissue in front of a line equidistant from cruciate and ansatus sulci was removed. After either l)rocetlure, the skull flal) was sutured back into place and the scalp was closctl. The kitten was then gradually warmed to normothermia (19) and, when it became spontaneously active, was coated with cod liver oil

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and returned to the mother. Prophylactic treatment with penicillin-G was administered for 4 days postoperatively. Testing Procedures. A battery of neurological tests and behavioral observations (3.2, 36) was applied to all kittens: once immediately before surgery, almost daily during the first 10 to 15 postsurgical days, about every 15 days during the following 3 to 4 months, and every month thereafter. Normative developmental data, reported elsewhere (36)) were obtained from a larger pool of 207 intact kittens including 33 littermates of the present animals. Neurological Testing. The items assessed were the following. (u) Movement and posture: locomotion, strength (paresis), spontaneous usage of paws, presence of abnormal movements, body righting upon a surface or on free fall, tonic neck reflexes, spontaneous body or head deviations, rigidity or spasticity of limbs, and limb placing reactions (proprioceptive, chin and visual placing, contact lifting (36)) dorsal and lateral contact placing, lateral hopping, and plank walking). (b) Sensatiom and other refle.vcs: reaction to pin prick, limb withdrawal and crossed extensor reflexes, visuopalpebral reflex, visual exploring, pupil size and reaction to light, binocular coordination, auditory orienting, and olfaction. The testing was to verify whether or not the developmental time course of the above characteristics matched the landmarks in intact kittens (36) and if abnormal neurological events appeared and persisted. Behavioral Observations. After preliminary observations, these focused on determining the presence or absence and time course of manifestations of the “compulsory approaching syndrome” as described for adult acaudate cats (32). The nine discreet behavioral elements of the syndrome were explored as follows. (a) Visual approaclz: following of persons and/or objects (vigor, speed, duration, head and eye positions while following, etc.), reaction to being pushed away from the investigator (how many times returned), effects of an auditory cue added to the visual stimulus or presented in another location. (b) V&al Tracking: objects moving horizontally or vertically in the kitten’s visual field (number of successive tracking movements, amplitude of head and eye movements). (c) Rooting reaction: The ringed thumb and index finger, or the cupped hand were placed around the muzzle and the kitten’s reaction was observed : rooting was considered present when forward walking against the hand was elicited and the strength and persistence of the pushing were evaluated. (d) Motor activity: This was scored during the test sessionsand also by observing the kittens in their home cages. An additional measurement was made when the animals were 36 to 63 days of age. The kittens were

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placed for 15min periods, one to two times per week, in a 61-cm? open field chamber gridded into 10.2-cm squares by 10 photocells positioned low in the walls. Movement across any photocell beam produced a count and these were recorded every 3 min. The kittens were removed from the mother in litters and kept together in a small 110s where they usually remained quiet. The order of testing was comnterbalancedto control amount of time (never longer than 1 h) of mother deprivation. (e) Tactile approach: assessedby observing whether the animal tended to physically contact the investigator or his hand placed near the kitten, attempted to grab or grasp the person or object being followed, or rubbed repeatedly against them. (f) Treading or kneading of the fovepazcrs: transient versus continuous occurrence, amplitude and rhythmicity of the movements, influence of the animal’s posture. (g) Pz0+g: persistence, intensity, relationship with the environmental variables (novel situation, threatening stimuli, etc.). Because no normative data were found in the literature concerning the maturation of this landmark, 20 colony kittens were studied from birth until more than 4 months of age following methods described previously (36 j. (h) Sr.~al behaz)ioY: Estrous-type behavior was assessedby observing the reaction to touching of the lumbosacral and perigenital regions. The presence and degree of lordosis, tail deviations, and hind limb treading were observed in males and females. The reaction to vaginal stimulation with a glass rod was also explored (“postcoital” reaction, genital secretion, etc. ) . (i) “AflCct:” assessedby observing the kitten’s attitude toward investigators and other cats (frien’dly versus hostile, exploring versus hiding, approach versus withdrawal). At each test session, the presence or absence of each of the above behaviors was noted and scored on a four-point scale on the basis of the quantifiable aspects described above. Three observers participated in the scorings with a good agreement in the ratings of the behaviors for individual animals. The median score for each cat was calculated for three postsurgical periods (expressed in postsurgical days) : 1 to 15, 16 to 120, and 120 to the day on which animals were killed or died. The median scores of the groups were then expressed as a percentage of the possible scores and are shown in Fig. 5 for the early (1 to 15) and late (120 to the end) epochs. Other behaviors were also monitored, i.e., feeding, drinking, grooming, and playin g. but were not quantified. Finally, relevant aspects of the chscrvations

were

recortlctl

on 8- and 16mm

film ant1 vitko

tape. Neurological and behavioral tlifferences between groti]ls \verc compared using nonparamctric statistics (25).

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Hisfological Procedures. At the end of the experiments, the animals were weighed, killed with an overdose of barbituate, and perfused with 10% formalin. The brains of most cats (Table 1) more than 9 months of age were weighed after cutting the brain stem at the level of the caudal cerebellar end and eliminating the olfactory bulbs, and brain weight: body weight ratios were calculated. Coronal sections of all acaudate brains and sagittal sections of all afrontal brains were stained using the Weil and Nissl methods on alternate sections. The lesions were reconstructed on plates from the atlas by Snider and Niemer (26), and the percentage ‘of caudate removed was then calculate’d following a previously described method (32). For evaluating the damage to noncaudate structures, the atlas by Reinoso-Suarez (22) was used as it provides complete coronal sections of the cat telencephalon. The ‘extent of the frontal ablation was evaluated by reconstructing the lesions on a drawing of the external surface of the brain (Fig. 2). RESULTS Survival The distribution of survival times is shown in Table 1. Most animals kept for more than 1 year were killed after a terminal electrophysiological experiment. Two acaudate preparations were killed due to antibioticresistant eye infections (at Days 190 and 224). For those dying from other causes, there was no correlation between the extent of brain lesion and age at death. The mortality rate of kittens with ablations under 1 year of age was not significantly higher and the causes of death were not different from those for normal kittens in our colony. Anatomy Acaudate Kittens. The amount of the nuclei removed was 22 to 100% (Table 1) with the majority of the subjects (N = 9) having extensive (Fig. 1) ablations including 66 to 100% of the nuclei volume (called large ablations). In incomplete ablations, the remnants were found in ventral and lateral regions of the caudate head and at the caudal end of the caudate body. Two kittens had bilateral damage to medial and ventral aspects of the rostra1 internal capsule [between A18 and A20 (26) ] ; one survived only 82 days. Additional damage in eight other brains was unilateral and slight including lesions of septal-fornix regions (three cases), internal capsule (six cases), and rostra1 thalamus (two cases). In all brains dorsolateral and frontal cortical regions were intact. Afrontal Kittens. The regions bilaterally ablated (Fig. 2) included the

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N Age at surgery (days) ix (range) SCi Male (N) Female (N) Survival >1 year (N) <1 year (iv) Brain Weight: Body Weight

Afrontal

66-100 (N = 9) 36-66 (N = 6) <33 (N = 2) 17 22 (9-36)

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Acaudate Extent of bilateral ablation (%)

IN

Frontal poles (cruciate sulcus rostra1 to it) 12 20 (9-32)

Sham-operated

and

Penetration (gyms

sites cinguli, corpus

CdlOSU~)

7 21 (14-30)

10 7

6 6

4 3

7 10 (2, 121 days) 0.0079 (N = 6)

8 4 (f. 90 days) 0.0081 (N = 7)

4 3 (2, 259 days) 0.007 (N = 6)

following gyri and adjacent sulci : proreus, presylvius (anterior two-thirds or one-half), anterior sygmoid, posterior sygmoid (anterior one-half in most kittens except in four in which only about the anterior one-fourth was ablated), coronalis (anterior one-half to one-fourth), orbitalis (anterior one-third to one-fourth), and, finally, most of frontalis and rectus with the anterior one-third to one-fourth of the pericruciate area in the medial aspect of the hemisphere. There were occasional asymmetries between right and left sides. Although differences in ablation size were rather small, the brains were rank ordered for lesion size for the purpose of correlation; about equal numbers were within the larger and smaller lesion groups as defined in Fig. 2. In all brains the rostra1 wall of the ventricles and the caudate nuclei were intact. The midline cortical lesion in sham-operate’d and in acaudate kittens was through the caudal end of the lower bank of the midline cruciate sulcus (area 24)) with variable extension over the upper bank and occasionally into area 31 or rostra1 aspects of area 23. The brain weight: body weight ratios of acaudate and afrontal animals (Table 1) were within the range of values for shamoperated cats [which was coincident with the ratio previously reported (4) for intact cats]. Given the small numbers and variability in measurements no firm conclusion is possible, but these data indicate there was no obvious atrophy of the brains; a finding which was supported by the histologic material. Recovery

a?ld Growth

(Body

Weight)

The postsurgical recovery of most kittens was surprisingly fast. They were active and nursing either late on the day of surgery or the next day. Only nine kittens (five acaudate and four afruntal) received supplemental feeding for 2 to 4 days due to poor nursing. The long-term body weights

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FIG. 1. Nissl-stained coronal sections of the brain of a 544-day-old cat which had bilateral removal of the caudate nuclei at 29 days of age. (Cortical damage is from electrode penetrations in a tervziml experiment.) A-at about A17.0 (26) ; B-at A13.0.

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2. Schematic views of the rostra1 portion of the cat telencephalon (A), dorsal (B), and midline (C) extension of the smaller (stippled plus darkened) frontal ablations.

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to show the (stippled) and

showed that animals with large caudate ablations gained less weight than those in other groups throughout their entire survival period (Fig. 3). However, the differences compare,d to intact animals were not significant unless they were divided according to sex, i.e., acaudate males, regardless of the ablation size, were significantly lighter (I’ < 0.01) than intact males. Neurology

Most neurologic characteristics matured Nezrrologic Cl~avactcvistics. within the normal range or with slight, nonsignificant delays in both acaudate and afrontal preparations. The exceptions were defects in the use of the paws, a subjective impoverishment of motor activities in the acaudate animals, and a delay in the maturation of the limb placing reactions. In addition, a minor but persisting paresis of the limbs and some deficit in reaction to pin prick or light foot pinch were detected in three afrontal kittens with large removals and in two of the three afrontal kittens with large removals and in two of the acaudate kittens with capsular damage. The defects of paw use were noticed even prior to puberty, particularly in climbing and walking, and were described as “clumsiness” or “awkwardness.” As long as contact placing was still immature, some aspects of this deficit could be accounted for, i.e., defects in plank walking, inadequate lifting of limbs when walking on uneven surfaces, paws slipping and/or limbs dangling over edges. However, a paw-use abnormality still persisted beyond full maturation of the placing reactions or at a time when the latter were only slightly defective. We analyzed these persistent defects in separate experiments and the results will be reported separately. Limb Placing Reactions. At surgery, all kittens exhibited a normal proprioceptive placing and all but two had contact lifting (2, 36). These were not affected by surgery in the sham-operated kittens. After surgery,

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in 4370 of the afrontal and 44% of the acaudate kittens (all with large ablations), the proprioceptive component was absent or markedly depressed until a mean age of 47 and 80 postnatal days, respectively. Similarly, contact lifting was suppressed in 55% of the afrontal and 50% of the acaudate kittens and reappeared at a mean age of 45 and 37 days, respectively. The other placing reactions were either absent or developing at time of surgery (36). As shown in Fig. 4, the mean dates for maturation of chin, visual, contact placing reactions, and plank walking were all delayed in the groups with lesions. The delays were small (1 to 2 weeks) and nonsignificant for the sham-operated kittens, but were significant in relation to normals for acaudate and afrontal kittens. The

4ooc

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AGE IN MONTHS FIG. 3. Body weight for brain-damaged and intact kittens. The extent of the large frontal ablations is shown in Fig. 2. The large caudate ablations removed 66% or more of the nuclei. The sham-operated kittens were not included in this graph because their growth was similar to that of intact animals. There were no differences prior to surgery.

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FIG. 4. Mean days to maturation of the limb placing reactions. (Mann-Whitney U) are as follows. P < 0.001 : *to intact animals ; P < 0.05 : *to intact, ‘to acaudate, and fto afrontal

Statistical animals, animals.

significances ‘to acaudate

acaudate animals showed the larger maturational retardation (Fig. 4) such that the reactions took two to four times longer to develop than in the intact animals. Indeed, in kittens with the largest removals, contact placing took as long as 8 months to mature. There was a positive correlation between the extent of caudate removal and delay in maturation of the reactions (Fig. 4), although this was significant only for lateral hopping and contact lifting (Spearman rank, Y, = 0.71, P < 0.02). On the other hand, there was no correlation between any capsular damage (see above) and maturational delays. In afrontal animals, the reactions matured within 4 postnatal months and, therefore, the delays were markedly shorter than in acaudate animals (significantly for four reactions ; Fig. 4). There was no correlation between extent of ablation and delay in maturation.

In contrast to the sparse neurologic consequences, the main effects of caudatectomy were behavioral. There were changes which could be detected by simple procedures (see Methods) as well as other manifestations which were demonstrable only by specific behavioral tests. The former will be described here, the latter will be reported in ensuing papers. All the

626 behaviors cats (32)

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related to the compulsory approaching syndrome of adult were seen in kittens, hut with a different time course. Early (1 to 15 days) Postswgical Period. As soon as they emerged from surgical anesthesia, all kittens which were 18 days of age or older (N = 11) exhibited a predominant visual approach with the subject walking toward a stationary person or object and following vigorously and persistently any movement of the target (compulsory approach). This behavior was stereotyped in that the kitten walked very close to the moving object, with the head down, and adhere’d markedly to changes in speed or direction. If pushed away by the investigator, the kitten would repeatedly return. As walking and running abilities were just developing, it was impressive to observe the vigor of the approach that made these activities appear suddenly improved. An auditory component was present, i.e., a sudden noise distracte’d or even redirected the kitten following a silent object whereas a sound emanating from a visual cue enhanced the approach. The behavior was less marked in the presence of smaller objects with poor contrast and the animals would not attempt to grab, grasp, or follow objects up the wall as do acaudate adults (32). Only three other elements of the adult syndrome were present at this time (Fig. 5) : visual tracking of objects in pendular motion, motor hyperactivity, and rooting. Visual tracking was not too vigorous or persistent and would not go beyond 10 to 20 repetitions. Hyperactivity was manifested in a continuous, aimless locomotion and/or vocalization even in the absenceof objects to follow, Contrasting with kittens older than 18 days at surgery, the two subjects which were 9 days old did not exhibit visual following or tracking and the four kittens between 9 and 19 days of age exhibited the behaviors less consistently when they reached 18 to 20 days of age. Nevertheless, all the latter six kittens were included for calculating the scores in Fig. 5. Acaudate kittens generally scored significantly higher on the above behaviors than all other animals. For afrontal kittens, the scoreswere higher for only some behaviors (e.g., visual tracking), but increases relative to intact animals were not statistically significant (Fig. 5). From 16 to 120 days Postsurgery. During the postsurgical period from 16 to 120 days, the scoresmarkedly declined for acaudate and afrontal animals alike, but did not change appreciably for controls. The acaudate animals, scores were still the highest, but the differences were not statistically significant. For brevity, the results for this period are not shown in Fig. 5. Motor activity was further tested at this time. Kittens with large caudate lesions were significantly [P < 6.01, Newman-Keuls test (38)] more active than animals in all other groups. The animals with the larger frontal lesions displayed a nonsignificant increase in motor activity. Sham-operated

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FIG. 5. Median percentage of possible scores for behaviors related to the “compulsory approaching syndrome” at (E) early (1 to 15 days) and (L) late (120 days to juvenile or young adult age) postsurgical periods. Statistical significances (median test) indicate differences between acaudate animals and the other groups: *P < 0.001, AP < 0.001, ‘P < 0.02, and l P < 0.05). Differences between afrontal, sham-o~rated, and intact animals were nonsignificant.

kittens showed lessactivity than intact controls (F’ < 0.01) or animals with a brain lesion (P < 0.01). Late FQs~slfrg~calPeriod (> 120 days). Purring was observed in about 5070 of intact kittens. The nlean day of its appearance was 70 c 31 days of age (range : 40 to 132 days). A similar developmental time course was observed in the experimental kittens. Paw treading a and tactile approach 3 A similar activity, i.e., kneading, is seen at birth but this seems to be of a different behavioral meaning as it occurs in the context of nursing,

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were seldom seen before the appearance of purring, and sexual behavior could be evaluated only at puberty [ 5 to 9 months (23) 1. The rooting reaction, tactile approach, purring, treading, and the sexual behaviors explored were enhanced in acaudate juveniles and young adults such that scores were significantly higher compared to other groups (Fig, 5). Those behaviors which were enhanced during early life also became prominent again, but were statistically significant for only visual approach and visual tracking of acaudate animals. Observations regarding sexual behavior and “affect” can be better described than statistically analyzed because the groups became small when partitioned by sex and evaluation of “affect” was, by necessity, subjective. After 5 to 9 months of age, all acaudate males (N = 4) displayed a stereotyped estrous-type behavior. This included brisk lordosis to light touch of the perineum, tail deviation toward the side contralateral to that stimulated and hind limb treading. In addition, rooting was exaggerated. This behavior was also observed consistently in the three acaudate females with a typical postcoital reaction and vaginal secretion following genital stimulation. Only two of the four afrontal males (and none of the shamoperated or intact animals) displayed intermittent female-type behavior. Acaudate animals were also most often described as friendly, approaching, purring, rooting, and sexually displaying cats. Accordingly, an overall mean score of > 2 was given to their “aflect” for all testing sessions. Among afrontal cats, two were described as very timid, withdrawn, and occasionally hostile and most others (N = 6) were labeled neutral or mildly timid. Only one, a female, received an overall score of 2 as did the intact animals. For sham-operated cats the scores were even more negatively biased as three of them were in the timid-withdrawn-occasionally hostile category. In brief, at juvenile and young ages the acaudate animals became again a strongly distinctive group. Finally, for all behaviors related to the compulsory approach there was a significant positive correlation between overall median percentage scores and extent of the caudate ablation (Spearman rank correlation, r, = 0.78, P < 0.02). DISCUSSION General Efects

of Extensive

Caudate Lesions

To our knowledge, this is the first study reporting effects of caudate lesions in kittens. We demonstrated that it is possible to ablate large portions of the caudate nuclei and to maintain the animals indefinitely. Qualitatively, the effects of both caudate and frontal lesions were similar in kittens compared to our adult cats but followed a quite different

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time course. Furthermore, the same clear differentiation of effects of caudate versus frontal lesions seen in adults was verified in the present study. We emphasized the effects of extensive, caudate ablations selective, (removal of more than 65% of the nuclei) because these have not been studied in either adult or neonatal cats (31, 32) and because, as discussed previously (21, 32-34), due probably to a large futictional reserve of caudate tissue, some effects of caudatectomy can be seen onl~l after total or near-complete ablations. Even though a number of studies analyzed the effects of smaller lesions in infant monkeys (5, 9, 10, 16, 17), a large lesion of the caudate nuclei not involving the cortex has been reported for only a single animal (5). The only persistent abnormalities observed were postural and were interpreted as avoiding automatisms. Transiently, that animal displayed approach toward the observer which was (5) felt to be similar to the compulsory approaching of our cats (32). Kling and Tucker (16, 17) reported devastating effects on survival, growth, and somatomotor functions in neonatal monkeys receiving combined frontal-caudate lesions which destroyed 10 to 50% of the nuclei. The deficits were thought to be due to the caudate damage because they were not present in subjects with only frontal ablations. The present observations certainly do not agree with the above findings as, in our kittens, caudatectomy did not have profound effects on feeding or other vital homeostatic processes, nor did it produce incapacitating neurologic or behavioral abnormalities. We do not have a clear explanation for the developmental lag in body weight in acaudate kittens, although the lag was small and significant only for males. There was a tendency for a decrease in growth to occur in all animals both at time of weaning anmdlater coincident with changes in feeding schedules for the behavioral testings (to be reported separately) carried out between 5 and 14 months of age. These decreases (Fig. 3) were even more marked for acaudate animals than for cats in other groups which suggests that they were more susceptible to imposed dietary changes. Klosovskii and Bolzhina (18) reported no alteration in body weight of no statistical comparisons beagle pups with caudate lesions, however, were made. Placing Reactions Neurologically, the defects in our kittens were rather subtle. Only the maturational defect in the limb placing reactions will be discussed here and the others will be dealt with elsewhere. The placing reactions were unusually delayed in acaudate animals so that in those with more than 6670 removal the reactions took longer than 6 months to full development in contrast with 2 to 3 months for intact animals (24, 30, 36). Comparisons

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with our earlier findings in adults (34) slowed 1 a striking difference : There was a reverse order in the time course of recovery of placing reactions in the acaudate and afrontal groups. Acaudate adults recovered contact placing within 4 postsurgical months, whereas not all the afrontal animals fully recovered the reactions and those that did (about 45%) took from 5 to 9 months to complete the process. This discrepancy cannot be accounted for by a differential amount of caudate or frontal ablations in the two age groups. On the one hand, there were acaudate adults with more than 90% removal whose reactions recovered within 4 months, whereas, on the other hand, there were afrontal kittens recovering in about 3 months and adults with lesions of a comparable size which did not fully recover in more than 6 months. It is likely that our kitten caudatectomise produced more capsular damage than those in adults and that could help to explain the differences. It is unlikely, however, that this is the whole explanation. First, minimal or no capsular damage occurred in several kittens with caudate removals greater than 7570. Second, if any damage of pathways occurred it could never be larger than that produced by removing, as in the afrontal animals, the same cortical regions where these pathways originate or terminate. Thus, the alternative explanation that the caudate might have a differential role in the control of contact placing in kittens should be considered. Although, in adults, such control seems to depend predominately on frontal cortical regions, the caudate might have a major role at an early age. A similar ontogenetic shift from subcortical to cortical “dominance” was hypothesized for delayed response performances in monkeys (9, 10). The placing reactions recovered faster in our kitten than in our afrontal adults which would indicate that for this function there is a larger sparing after neonatal cortical lesions. Such a conclusion, however, does not quit& agree with Glassman (7) who did not observe differential recovery after early versus late (5 months of age) frontal cortical lesions. However, the ablations in his kittens were more extensive than those inflicted at 5 months of age, an age which, furthermore, rendered his adults not strictly comparable to ours. Given the difficulty of performing frontal lesions of exactly the same size in newborn and adult cats, the large difference in sparing of functions between our adult and neonatal groups versus only a slight difference in size of the removals (larger in adults) should perhaps be taken as an argument for a larger recovery in kittens. Finally, we have seen nothing to agree with the report (1) that, in kittens less than 4 weeks of age, contact placing returns minutes or hours after frontal removal and is lost when the animals are 1 to 2 months of age.

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Bchaz~io~~al Results There was an interesting time course in the behaviors related to the compulsory approaching syndrome. Immediately after caudatectomy, only a few manifestations were present in all acaudate kittens more than 18 days old. The remainder appeared after 3 months of age and were most marked at puberty. These late manifestations (tactile approach, purring, treading, sexual, and “affect” changes) were behaviors which even normal kittens did not display before 2 to 3 months of age. Therefore, we think that it is precisely the absence of these behaviors in the repertoire of kittens of this age which best explains why they were not present immediately after surgery (as in adults). Within the same context, Kling observed that after amygdalectomy in kittens (14) some aspects of the adult syndrome ( 15) became prominent only at puberty. On the basis of the above observations, one can conclude that some effects of neonatal brain damage can be seen only when the brain has matured sufficiently (f7) to provide the functional background neede’d for the actual display of given behaviors. If the animals are not followed long enough after surgery such manifestations can be totally missed. The fact that the two youngest (9 days old) acaudate kitt.ens did not display any early visual approach or tracking and that three other subjects (13, 13, and 17 clays of age) displayed these behaviors only when they were about 18 to 20 days old puzzled us greatly, particularly when the histological study confirmed that this was not due to incomplete caudate removal. However, our study of intact kittens demonstrated that visual behavioral abilities (36) mature rather late. Indeed, visual exploring appeared at a mean age of 24 * 4 days (range: 18 to 37 ; N = 36) and other visual behaviors matured even later, Therefore, absence of visual following in the youngest acaudate animals seems to be another case (see above) of immaturity of the function being tested, i.e., the veq young kittens did not display a visual approach merely because they could not clearly see what they were supposed to follow. If this interpretation is true, it strongly underscores the age element in the evaluation of early brain lesions. In the present case, if all our kittens had been younger than 9 days at surgery, we would have arrived at the erroneous conclusion that compulsory approaching is not seen after neonatal caudatectomy. As in the present kittens, the compulsory approaching seen in acaudate adults also attenuated with time (32) and this decrease was inversely related to the size of the lesion. Such reduction was more marked between 16 and 120 days after surgery. The fact that not all components of the syndrome were simultaneously present and that visual following was less marked in kittens initially may partially explain the faster attenuation. The finding of motor Izyprmctiz-lity in acaudate kittens agrees with our

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observations in adults (20, 32, 33). It was suggested (17) that, even though both the frontal regions and the caudate nuclei participate in the control of motor activity, the basal ganglia appear to exert greater suppression early in development. In the present study, caudate ablation produced a significant hyperactivity whereas the enhancement produced by frontal removal was slight, a finding which supports the above hypothesis. The mechanisms by which caudate lesions may produce hyperactivity were previously discussed (33). In sunwzary, these observations indicate that the effects of early brain lesions are both complex and dynamic. There are early deficits which disappear as development proceeds, e.g., the defects in limb placing reactions in afrontal kittens. Another category of effects, e.g., several elements of the compulsory approaching syndrome in acaudate kittens, appears very late, only at puberal age. Finally, a third group of manifestations, e.g., motor hyperactivity and impoverishment on movements in acaudate subjects, appears to be permanent. The main factors contributing to 1he complexity of the effects of early brain damage demonstrated here were age at surgery and age at testing. Also, the site of the lesion is important for functions such as placing reactions and motor activity which apparently are controlled by both the caudate and the frontal cortex. Data further defining the above categories as well as additional factors involved in the outcome of neonatal lesions will be reported in the following papers. REFERENCES 1. AMASSIAN, V. E., AND R. Ross. 1972. Development in the kitten of control of contact placing by sensorimotor cortex. J. Physiol. (London) 230: 55-56. 2. AVERY, D. L., J. R. VILLABLANCA, R. J. MARCUS, AND C. E. OLMSTEAD. 1975. Development of limb placing reactions in intact, frontal and caudate lesioned kittens. Fed. Proc. 34 : 445. 1959. Differential effects of cortical 3. BENJAMIN, R. M., AND R. F. THOMPSON. lesions in infant and adult cats on roughness discrimination. Exp. Neurol. 1: 305321. 4. CRILE, G., AND D. P. QUIRING. 1940. A record of the body weight and certain organ and gland weights of 3690 animals. OItio J. Sci. 40: 219-229. 5. DENNY-BROWN, D., AND N. YANAGISAWA. 1973. Dystonia resulting from lesions of basal ganglia in infant macaques. Trans. Am. Nezlrol. Assoc. 97 : 105-108. 6. DIVAC, I., H. E. ROSVOLD, AND M. K. SZWARCBART. 1967. Behavioral effects of selective ablation of the caudate nucleus. J. Camp. Physiol. Psychol. 63 : 184-190. 7. GLASSMAN, R. B. 1973. Similar effects of infant and adult sensorimotor cortical lesions on cats’ posture. Bruin Res. 63 : 103-110. 8. GOLDMAN, P. S. 1971. Functional development of the prefrontal cortex in early life and the problem of neuronal plasticity. Exp. Neural. 32: 366-387. 9. GOLDMAN, P. S. 1976. Maturation of the mammalian nervous system and the ontogeny of behavior. Pages l-90. in J. S. ROSENBLATT, R. A. HINDE, E. SHAW, AND C. BEER, Eds., Advances In The Study Of Behavior. Academic Press, New York.

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11.

12. 13. 14. 15. 16. 17.

l$

19. 20. 21.

22. 23. 24. 25. 26. 27. 28. 29.

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P. S., AND H. E. ROSVOLD. 1972. The effects of selective caudate lesions in infant and juvenile rhesus monkeys. Brain RFS. 43 : 53-66. ISAACSON, R. L., A. J. NONNE~~AN, AND L. W. SCHMALTZ. 1968. Behavioral and anatomical sequelae of damage to the infant limbic system. Pages 41-78 in R. L. ISAACSON, Ed., The Netwopsychology of Dcuelopmer~t. Wiley, New York. KENNARD, M. A. 1938. Reorganization of motor function in the cerebral cortex of monkeys deprived of motor and premotor areas in infancy. J. Nekwophysiol. 1 : 477-496. EIENNARD, M. A. 1940. Relation of age to motor impairment in man and in subhuman primates. Arch. Newel. Psychiat. 44 : 377-397. KLING, A. 1962. Amygdalectomy in the kitten. Science 137 : 429. KLING, A. 1965. Behavioral and somatic development following lesions of the amygdala in the cat. J. Psychiat. Res. 3 : 263-273. KLING, A., AND T. J. TCCKER. 1967. Effects of combined lesions of frontal granular cortex and caudate nucleus in the neonatal monkey. Brain Rcs. 6: 428-439. KLING, A., AND T. J. TUCIER. 1968. Sparing of function following localized brain lesions in neonatal monkeys. Pages 145-212 in R. L. ISAACSON, Ed., The Nezbropsyclrology of Dezelopmcrtt. Wiley, New York. KLOSOVSKII, B. N., AND N. S. BOLZHINA. 1956. Physical and behavioral development of puppies with removed subcortical nuclei (caudate nuclei) and spared cerebral cortex. Avk. Patol. 18 : 35542 [in Russian]. OLMSTEAD, C. E., AND J. R. VILLABLANCA. 1977. Maturation of behavioral and physiological thermoregulation in kittens. Proc. Int. U&&t Physiol. Sci. 13: 567. OLMSTEAD, C. E.,AND J. R. VILLABLANCA. 1977. Hyperactivity versus hyperreactivity in frontal cortex and caudate lesioned cats. Sot. Nez~rosci. .qbstr. 3 : 44. OLMSTEAD, C. E., J. R. VILLABLANCA, R. J. MARCUS, AND D. L. AVERY. 1976. Effects of caudate nuclei or frontal cortical ablations in cats. IV. Bar pressing and maze learning and performance. E.rP. Nczwol. 53 : 670-693. REINOSO-SUAKEZ, F. 1961. Topograp/zisc!rcr Hirnatlas der Katz. Herausgegeben von E. Merck, A. G. Darmstadt. SCOTT, P. P. 1970. Cats. Pages 192-207 in E. S. E. HAFEX, Ed., Repvodztctiox and Brcediug Techniques for Laboratory A~zivzals. Lea Febiger, Philadelphia. SECHZER, J. A., R. F. MERVIS, AND G. L. COOPER. 1975. Neuro-ontogeny of postural reflexes in normal kittens. Sot. Nezbrosci. Ahtr. 1 : 747. SIEGEL, S. 1956. Nonparametric Statistics for the BcitaeIioral Scicwes. McGrawHill, New York. SNIDER, R. S., AND W. T. NIEMER. 1961. -4 Steveotasic Atlas of the Cat Brailk. University of Chicago Press, Chicago. TEUBER, H.-L. 1973. Recovery of function after lesions of the central nervous system : History and prospects. Neurosci. Res. Program Bull. 12 : 197-211. TEUBER, H.-L., AXD R. RUDEL. 1962. Behaviour after cerebral lesions in children and adults. Den. Med. Child Newel. 4 : 3-20. TUCKER, T. J., AND A. KLINC. 1967. Differential effects of early and late lesions of frontal granular cortex in the monkey. Brain Res. 5 : 377-389. GOLDMAN,

30. VAN HOF-VAN DUIN, J. 1976. Development of visuomotor behavior in normal and dark reared cats. Braikk Rcs. 104 : 233-241. 31. VILLABLANCA, J. 1975. Effects of caudate nuclei removal versus frontal cortex lesions in kittens. Pages 393-399 in N. A. BUCIIWALD AND M. A. BRAZIER, Eds., Brain Mechanisms irz Mrutal Retardation, Academic Press, New York. 32. VILLABLANCA, J., R. J. MARCUS, AND C. E. OLMSTEAD. 1976. Effects of caudate

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nuclei or frontal Exp.

33. 34.

35. 36. 37. 38.

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ablations in cats. I. Neurology

and gross behavior.

52 : 389420.

J., R. J. MARCUS, AND C. E. OLMSTEAD. 1976. Effects of caudate nuclei or frontal cortical ablations in cats. II. Sleep-wakefulness, EEG and motor activity. Exp. Neural. 53 : 31-50. VILLABLANCA, J., R. J. MARCUS, C. E. OLMSTEAD, AND D. L. AVERY. 1976. Effects of caudate nuclei or frontal cortex ablations in cats. III. Recovery of limb placing reactions including observations in hemispherectomized animals. Exp. Neurol. 53 : 289-303. VILLABLANCA, J. R., AND C. E. OLMSTEAD. 1977. Effects of similar caudate or frontal ablations in kittens and in adult cats. Proc. 1st. Union Physiol. Sci. 13: 788. VILLABLANCA, J. R., AND C. E. OLMSTEAD. 1978. Neurological development of kittens. Dev. Psychobiol. (in press). VILLABLANCA, J. R., AND C. E. OLMSTEAD. 1978. Effects of caudate nuclei removal in kittens. Appl. Neuroplzysiol. (Basel) . (in press). WINER, B. J. 1962. Statistical Principles irt Experimental Desigrz. McGraw-Hill, New York. . VILLABLANCA,