Partitioning of behavioral arousal

Ph.vsiology & Behavior', Vol. 17, pp. 581 586. Pergamon Press and Brain P,esearch Publ., 1976. Printed in the U.S.,\.

Partitioning of Behavioral Arousal' C H A R L E S M. M I E Z E J E S K I 2

N e w York Stale Institute ]'or Basic Research in Mental Retardation, 1050 Foresl Hill Rd., Staten Island, N Y 10,714 STACY L A M O N , G E O R G E C O L L I E R A N D L E O N A R D W. H A M I L T O N

Rutgers University. N e w Brunswick, N J 0890,7 (Received 7 O c t o b e r 1975) Mlt'IZI{.II:;SKI, ('. M., S. LAMON, G. COLLIER AND L. W. HAMILTON. Partitionhtg o/'hehavioral arousal. PIIYSIOL. BI.HAV. 17(4) 581-586, 1 9 7 6 . - Rats given continuous access to running wheels exhibited depressed stahilimeter and rearing activity in novel environments. Whereas starvation increased running wheel activity, it depressed slabilimeter activity markedly and increased rearing slightly, but not significantly. Relative to animals ted ad lib, starved rills exhibited an absence of intersession habituation or" stabilimeter responses and dinrinished intrasession habituation of rearing responses. Whereas running wheel behavior was correlated with percent body weight loss, stabilimeter and rearing responses were not. These data accentuate the heterogeneity of so-called behavioral arousal. Arousal

l)eprivalion

Running wheel

Slabilimeter

THE term arousal appears f r e q u e n t l y in discussions of b o t h h u m a n and i n f r a h u m a n behavior. O f t e n used s y n o n y m o u s l y with n o n s p e c i f i c behavioral, a u t o n o m i c , and electrocortical activity, it has been used to explain a b r o a d range of p h e n o m e n a : e.g., interspecies [ 3 3 ] , interindividual [21] and i n t r a i n d i v i d u a l 1 l ' 4 2 9 ] differences in p e r f o r m a n c e and learning, m e n t a l r e t a r d a t i o n [7,25] and s c h i z o p h r e n i a [ 1 8 , 3 5 ] . The m e a n i n g f u l n e s s of these e x p l a n a t i o n s d e p e n d s upon our u n d e r s t a n d i n g of arousal. Investigations of the behavioral arousal or activity of i n f r a h u m a n species have involved a variety of indices t h a t a p p a r e n t l y lack c o m p a r a b i l i t y [ 1 ] . Three c o m m o n l y used indices of behavioral arousal have been the activity wheel, s t a b i l i m e l e r or tilt cage and f r e q u e n c y or d u r a t i o n of rearing responses in an o p e n field. Rearing b e h a v i o r has been t h o r o u g h l y researched by Lat and his associates [17, 20, 21, 22, 2 3 ] , w h o have regarded it as an index of nonspecific e x c i t a b i l i t y level. ( ' a m p b e l l and his associates have used s t a b i l i m e t e r devices to e x a m i n e the effects of tood d e p r i v a l i o n [ 6 , 3 2 ] , wa~er d e p r i v a t i o n [ 4 ] , brain lesions [5 ], and p h a r m a c o l o g i c a l m a n i p u l a t i o n s [ 16]. They have viewed the s t a b i l i m e t e r as indicative of altered reactivity lo e n v i r o n m e n t a l stimuli. T h e m o s t f r e q u e n t l y used measure of the general or s p o n t a n e o u s activity of animals has been the activity wheel. First used in 1898 by Stewart [ 2 7 ] , level of wheel activity is the only measure of s p o n t a n e o u s activity that has r e p e a t e d l y been s h o w n to be related to percent b o d y weight loss during food or w a t e r deprivation ]8, ~,~. 11, 13, 3 4 ] . The fact t h a t o t h e r activity

Rearing activity

Exploralory behavior

devices differ from activity wheels in this respect has been n o t e d previously [4, 14, 3 1 , 3 4 , 3 6 1 . Collier, Hirsch and Leshner 113] have r e p o r t e d that, during the first few days of d e p r i v a l i o n , activity-naive rats given access to activity wheels did not lose b o d y weight any more rapidly than rats not given access to wheels. Collier and Hirsch [101 have also s h o w n that access to an activity wheel can be used as a reinforcer. F o r these reasons. Collier and his associates have argued that wheel activity, unlike o t h e r measures of s p o n t a n e o u s activity, is related to physiological regulatory m e c h a n i s m s . In the present investigation, ruts were either starved or provided food ad lib and either given c o n t i n u o u s access or not given access to r u n n i n g wheels. The effect o f these t r e a t m e n t s on s t a b i l i m e t e r and rearing aclivity d u r i n g brief e x p o s u r e h) novel e n v i r o n m e n t s was then observed. MEI'HOI)

A n irnals The animals were 24 male Sprague-Dawley rats, 62 days of age and weighing 265 315 g at the b e g i n n i n g of the experiment.

Apparatus Twelve W a h m a n n activity wheels {dia. = 36 cm) were used. E x p l o r a t o r y b e h a v i o r was measured with stabilimeters and an a p p a r a t u s for the a u t o m a t i c recording of t h e

'The author~ wish It) acknowledge the drawing and pholographing of tile figures by Michael I'. Donadio and Paul t.. {Jlatowski and the 'ariling ot" the computer program for ~;1atistical analyses by DiamantJs Skinitis. Portions of lhis paper ,,,,ere presented al file Annual Meeting ot" tile Easlern P';ychological Association. New York. April 1975. eThe dahr pre~;ented here were collected while this author Was ill Rulgers Unb, ersilr. 581

582

M I E Z E J E S K I , L A M O N , ( O L [ IER A N D H A M I L T O N

f r e q u e n c y a n d d u r a t i o n of rearing responses. E a c h stab i l i m e t e r cage was 40 × 18 × 1c) cm and had a floor c o m p o s e d of 4 m e t a l gratings of e q u a l size. O n e edge of each grating was a t t a c h e d w i t h hinges to the central long axis of t h e cage, while the o p p o s i t e edge rested on a m i c r o s w i t c h , o p e r a t e d b y a p p r o x i m a t e l y 140 g of pressure. This a p p a r a t u s p e r m i t t e d the r e c o r d i n g of m o v e m e n t s from q u a d r a n t to q u a d r a n t . Six of these s t a b i l i m e t e r s were h o u s e d in a s o u n d and light a t t e n u a t i n g c a b i n e t , ventilated by a fan t h a t also p r o v i d e d a m a s k i n g noise. T h e rearing device was a Plexiglas c o m p a r t m e n t (31 × 28 ~ 64 cm) with a floor consisting of m e t a l bars (2 m m dia.: 12 m m apart, c e n t e r to c e n t e r ) . Along the w i d t h of this c o n > p a r t m e n t and at a h e i g h t of 10 cm, there were eight equally spaced p h o t o b e a m s . T h e i n t e r r u p t i o n of o n e beam or the s i m u l t a n e o u s i n t e r r u p t i o n of m o r e t h a n o n e b e a m resulted in a single c o u n t o n a f r e q u e n c y c o u n t e r . A t i m e r was activated for the d u r a t i o n of b e a m blockages. A b a n k of 10 c o u n t e r s and 10 timers p e r m i t t e d t h e r e c o r d i n g of freq u e n c y per m i n a n d t o t a l d u r a t i o n per min. Thus, the average d u r a t i o n of rears w i t h i n a given m i n u t e could be calculated. This rearing device w a s h o u s e d in a s o u n d and light a t t e n u a t i n g c a b i n e t , v e n t i l a t e d b y a fan that also provided a masking noise.

18 cm cages. Since the small size ¢~! lhe c o n v e n t i o n a l living cage used with t h e W a h m a n n activity wheel prevents, or at leasl limits rearing, an a l t e r n a t i v e had to be f o u n d . For this reason, the same type of cage as had been used with the Nonactive a n i m a l s was used with tht:' ~ c l i v e animals, excep~ it was placed on its side with t h e ~pen lop against the wait of the W a h m a n n activity wheel, dllowing the o c c u p a n t c o n t i n u a l access to the wheel. One day after t h e removal of food f r o m t h e Deprived animals. ~me hr of s t a b i l m l e t c r activity and 10 rain of rearing acl;vily were recorded daily on 5 c o n s e c u t i v e days for all animals. F o l l o w i n g these tests, they were i m m e d i a t e l y r e t u r n e d t,~ t h e i r cages,.)r r u n n i n g wheels. F a c h day, before the s t a b i l i m e t e r and rearing t e s t s n u m b e r of wheel t u r n s m a d e b5 li~c Active an{ma!s was recorded. F o l l o w i n g the 5 hr t.estl~g period (2 7 p.m.i, alt animals were weighed and wheel t u r n s were again recorded. Thus, data include only the I~¢ hr preceding the daity testing period. A 14- l 0 light dark cycle, lights out a~ X p.m. was used. RESU I, i>

As shown in Fig. l, the presentty observed body weighl changes clearly replicated t h o s e r e p o r t e d b y Collier +'t at. [ 1 3 ] . Likewise, there was a similar increase in wheel activity due to starvation (Fig. 2). f i n b o t h Figs. I and 2. the left graph depicts the data o b t a i n e d by ('oilier c t a/. [ t 3 l and the right graph is that o~ the present d a t a . ) A s is evident in Fig. 3, b o t h access Io activity wheels and starvation resulted in depressed s t a b i l i m e t e r activity I F ( 1 . 2 0 ) = 51.70, p < 0 . 0 0 1 : F< 1,77(!) = 3 1 . 0 3 , F
Procedure

One day b e f o r e t h e r e c o r d i n g of any activity data, the animals were m a t c h e d for weight and assigned to 4 groups: 1) Active-Ad lib, 2) A c t i v e - D e p r i v e d , 3) N o n a c t i v e - A d lib and 4) N o n a c t i v e - D e p r i v e d . Active is d e f i n e d as access to a W a h m a n n activity wheel for 21.5 h r per day and Deprived refers to t h e c o m p l e t e r e m o v a l of food b u t n o t water. T h e N o n a c t i v e animals were h o u s e d individually in 24 × 18 ,~

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FIG. 1. Changes in log percent body weight as a function of clays of wheel activity and food deprivation. Left graph: Collier, et al. I 13 t- Right graph : Present data.

PARTITIONING OF AROUSAL

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FIG. 2. Wheel activity during starvation and ad lib feeding. Left graph: Collier et al. [13], each point represents 24 hr of activity. Right graph: Present data, each point represents 19 hr of activity. Condition interaction (F(1,20) = 34.41, p < 0 . 0 0 1 ) . A significant Activity Condition × Days interaction (F(4,80) = 4.14, p < 0 . 0 0 5 ) resulted from the decreased responding across days by the Nonactive animals and no change by the Active animals. This intersession habituation by the Nonactive animals is upheld by a critical difference value of t.0 s = 36.2, using Fisher's test for the least significant difference (LSD test). As shown in Figs. 4 and 5, the rearing activity of the Active animals was significantly less than that of the Nonactive groups (F(1,20) = 8.23, p < 0 . 0 1 ) . The main effect of Days was also significant (F(4,80) = 10.91, p< 0.001 ), indicating intersession habituation for all groups. On the other hand, as shown by Fig. 5, while there was a significant overall decrease in rearing within a 10 min session (F(4,80) = 19.91, p < 0 . 0 0 1 ) , greater intrasession habituation by the Ad lib animals is evidenced by a F o o d Condition x Intervals interaction (F(4,80) = 3.50, p<0.01 ). The Fisher LSD test yielded a critical difference value of Cos = 1.75. A correlation of 0.66 ( d f = 28, p < 0 . 0 1 ) was obtained between wheel activity and percent body weight loss without regard to time for the Active-Deprived animals. On the other hand, the correlations of percent body weight loss with rearing and with stabilimeter activity for the same animals (r = 0.06 and r = 0.15, respectively), as well as for the combined data of the Active and Nonactive-Deprived animals (r = 0.05 and r = 0.04, respectively), were nonsignificant. DISCUSSION

The term arousal has been used in the sense of a general

increase in activity level. For the term to be useful the variables posited to increase arousal should have c o m m o n effects. One finding of the present study is that food deprivation, c o m m o n l y assumed to increase arousal, has quite different effects on three different kinds of activity. This is not a surprising conclusion in the light of past research [4, 14, 31, 34, 36] and the fact that these activities differ in kind and apparently in the functions they subserve for the organism. Wheel running is an energy consuming response which does not habituate over successive opportunities, and which is sensitive to variables influencing metabolic state, such as time of day [28], food and water depletion [8,13], dietary imbalance [ 1 2 ] , ambient temperature [3,30], etc. It appears to be under endogenous control with the qualification that it c o m p e t e s with other behaviors which may be under stimulus control. Rearing, on the other hand, has low energy cost, habituates rapidly both within and between sessions, and is very sensitive to environmental stimuli [17}. ('age-crossing seems to be the only one of the three activities which is nonspecific and intuitively exemplifies the notions of restlessness and irritability which underly the concept of arousal. In one sense it is not a response measure, since it is a composite of the variety of behaviors which activate the recorder. It does not, on the face of it, subserve any single function in the animal's e c o n o m y . The effect of deprivation on wheel running replicated previous results, showing that running is :l simple function of percent body weight loss, and that, in spite of the large increase in running and presumably energy expenditure as weight is lost, it does not affect the rate of weight loss [10]. The effect of deprivation on rearing was quite

584

MIEZEJESKI, LAMON, COLLIER AND HAMILTON

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different in that, while the absolute level of rearing was greater and the rate of habituation was less in deprived animals neither measure was a function of body weight loss. The effect of deprivation on rearing appears to be the result of the nonavaitability of food rather than the metabolic consequence of deprivation. The effect of deprivation on cage-crossing was simply to reduce the amount of activity. Again there was no relation between percent body weight loss and the level of cage-crossing. Recent brain lesion studies, demonstrating the neuroanatomical separation of wheel, stabilimeter and rearing activities, accentuate the inability to use these measures as interchangeable indices of behavioral arousal. Lynch [24] has shown that rats with lesions of the anterior medial forebrain bundle are more active than control animals in wheels but not stabilimeters. On the other hand, lesions of the dorsal frontal cortex or the inferior thalamic peduncle enhance stabilimeter activity in deprived rats but have no effect on wheel activity. Similarly, Capobianco and Hamilton (in press) observed greatly increased wheel activity and decreased stabilimeter activity in rats following transection of septo-hypothalamic fibers, whereas the transection of septo-hippocampat fibers produced large increases in stabitimeter activity and only slight increases in wheel activity. Neither of these transections altered rearing activity. More recently, Miezejeski and Hamilton (unpublished observations), working in the same laboratory and using the same rearing apparatus, have observed large increases in the rearing activity of rats following lesions of the dorsal raphe nucleus. Another indication of the heterogeneity of behavioral arousal derives from research findings in behavior genetics. Mice selectively bred'for high and low open-field activity do not exhibit corresponding differences on a number of other activity measures, including the running wheel [ 15 ]. Perhaps the most interesting result of the present experiment is the effect of wheel running on the brief, daily

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samples of rearing and cage-crossing. In b o t h cases, the animals with access to wheels s h o w e d a depression in each of the o t h e r activities w h i c h was i n d e p e n d e n t of deprivation. This might be i n t e r p r e t e d in t e r m s o f an activity budget [ 2 6 ] , but this seems implausible in the light of t w o facts. First, the i n c o m m e n s u r a b i l i t y of the three activity measures discussed above suggests that t h e y can not be considered as measures of a c o m m o n process, but must be regarded as three d i f f e r e n t activities. Second, the failure of the depression in rearing and cage-crossing to increase with the increased running associated with increased weight loss, suggests that it is not the activity w h i c h p r o d u c e d the depression [32] but rather the d i f f e r e n t e n v i r o n m e n t provided by the presence o f wheels and o f running. Along these lines, the depression o f these activities might be viewed as the result of the t r e a t m e n t c o n d i t i o n s interacting with rate of h a b i t u a t i o n to the test e n v i r o n m e n t . This alone, however, c a n n o t explain the dramatically small n u m b e r of cage-crossings by the Active groups on Day 1, since this is still significantly less than t h a t o b t a i n e d by the Nonactive groups even on the fifth day of e x p o s u r e to the test e n v i r o n m e n t .

Thus it would seem that the three activities observed in the present e x p e r i m e n t c a n n o t be f u n c t i o n a l l y similar and must subserve d i f f e r e n t f u n c t i o n s in the animal's e c o n o m y . Wheel-running [9, 10, 13], is associated with and p e r h a p s d e f e n d s m e t a b o l i s m , while rearing, as [,at [ 2 1 ] has argued, indexes e x p l o r a t i o n . Removal of food appears to stimulate exploration. On the o t h e r hand, removal o f food may remove some o f the stimulation eliciting the group of responses included in the cage-crossing measure ['~, 6, 32]. The present findings should serve as a n o t e o f caution to those theorists w h o refer to changes in activity following surgical or pharmacological m a n i p u l a t i o n s as support for this or that t h e o r y of arousal. Saying that a change in a specific activity level is a change in general arousal is at best speculative. These findings should also, however, encourage those researchers interested in the functional aspects of activity in that clear and persistent changes were o b t a i n e d for three specific activities c o m m o n l y used in behavioral research. In conclusion, the present e x p e r i m e n t c o n f i r m s Hebb's earlier p r e d i c t i o n that '+arousal will eventually be f o u n d to vary qualitatively as well as q u a n t i t a t i v e l y . " (119], p. 249).

REFERENCES 1. Baumeistcr, A., W. 1'. Hawkins and R. L. Cromwell. Need states and activity level. Psychol. Bull, 61: 438-453, 1964. 2. Bolles. R. C. and M. S. Younger. The effect of hunger on the threshold of behavioral arousal. Psyohon. Sci. 7 : 2 4 3 244, 1967. 3. Brobeck, J. R. l~iI'fectsof variations in activity, food intake and evnironmental temperature on ,,,,'eight gain in the albino rat. Am..L Physiol. 143:1 5, 1945. 4. Campbell, 13. A. Theory and research on the effects of water deprivation on random activity in the rat. In: Thirst in the Regulation o f Body Water, edited by M. J. Wayner. New York: Pergamon Press, 1964+ pp. 317- 334. 5. Campbell, B. A. and t,. Baez. Dissociation of arousal and regulatory behaviors following lesions of the lateral hypothalamtts. J. comp. physioL PsTchoL 87:142 149, 1974. 6. Campbell, B. A. and 1,. D. Sheffield. Relation of random activity to food deprivation. J. cornp, physiol. PsyehoL 46: 320 322, 1953. 7. ('lausen. J., A. Lidsky and E. A. Sersen. Measurements of autonomic functions in mental deficiency. In: Developmental Psychoph.vsiology of Mental Retardation, edited by R. Karrer. Springfield, 111.: Charles C Thomas, 1976. 8. Collier. G. Body weight loss as a measure of motivation in hunger and thirst. Ann. N. Y. Acad. Sci. 157: 594-609, 1969. 9. Collier, G. Work: A weak reinforcer. Trans. N. K Acad. Set. 32:557 576, 1970. 10. Collier, (;. and E. Hirsch. Reinforcing properties of spontaneous activity in the rat..L cornp, physiol. Psychol, 77: 155 160, 1971. t 1. Collier, G. and 11. A. Levitsky. Operant running as a function of deprivation and effort. J comp. physioL Psychol. 66: 522 523, 1968. 12, Collier, G. anti R. L. Squibb. Diet and activity. J. comp. physiol. Ps3'chol. 64:409 413, 1967. 13. Collier, G., 1'i. llirsch and A. 1. Leshner. The metabolic cost of aclivity in activity-naive rats. Physiol. Behal'. 8 : 8 8 1 884, 1972. 14. ('ornish, E. R. and N. Mrosovsky. Activity during food deprivation and satiation of six species of rodent. Anita. Behav. 13:242 248, 1965. 15. Det,ries, ,I. C., J. R. Wilson and G. E. McClearn. Open-field behavior in mice: Selection response and situational generality. Behav. Genet. I: 195 211, 1970.

16. l,'ibiger, H. ('. and B. A. Campbell. The effect of parachlorophenylalanine on spontaneous locomotor activity in the rat. Neuropharmacolo,ry I0:25 32, 1971. 17. Frankova, S. Exploratory activity of rats subjected to different types of stimuli. Czechoslovak Psychol. 9:58 69, 1965. 18. Gruzelier, J. H. and P. H. Venables. Evidence of high and low levels of physiological arousal in schizophrenics. Psychophysiology 12:66 72. 1975. 19. Hebb, D. O. Drives and the ('.N.S. level of the central nerwms system in the rat. Phv.s'ioloeia hohemoslov. 20: 441 445, 1971. 24. Lynch, G. S. Separable forebrain systems controlling different manifestations of spontaneous activity..I, comp. physiol. Ps:vchol. 70:48 59, 1970. 25, Miezejcski, ('. M. Effect of while noise on the reaction time of mentally retarded subiects. Am. ,L nteHt. De./~'c. 7 9 : 3 9 43, 1974. 26. Morrison, S. D. The constancy of energy expended by rats on spontaneous activity, and the distribution of activity between feeding and non-feeding. J. Physiol. 197:305 323, 1968. 27. Reed, J. D. Spontaneous activity ot animals. A review of the literature since 1929. PsTchol. Bull. 44:393 412, 1947. 28. Richter. C. P. Animal behavior and internal drives. Q. Rev. Biol. 2:307 343, 1927. 29. Stennett, R. G. The relationship of performance level Iv level ofarousal. J. exp. P,u'chol. 54:54 61, 1957.

586 30. Stevenson, J. A. F. and R. H. Rixon. Environmental temperature and deprivation of food and water on the spontaneous activity of rats. Yale J. Biol. Med. 29: 575-584, 1957. 31. Strong, Jr., P. N. Activity in the white rat as a function of apparatus and hunger. J. cornp, physiol. Psychol. 53: 242-244, 1957. 32. Teghtsoonian, R. and B. A. Campbell. Random activity of the rat during food deprivation as a function of environmental conditions. J. comp. physiol. Psychol. 53: 242--244, 1960. 33. Thompson, R. W. and L. G. Lippman. Exploration and activity in the gerbil and rat. J. comp. physiol. Pxychol. 8 0 : 4 3 9 - 4 4 8 , 1972.

M I E Z E J E S K I , LAMON, C O L L I E R AND H A M I L T O N 34. Treichler, F. R. and J. F. Hat1. I h e relationship between deprivation weight loss and several measures of activity. ,L comp. physiol. Psychol. 5 5 : 3 4 6 - 3 4 9 . 1962. 35. Venables, P. H. Performance ~ld level of activation ira schizophrenics and normals. Br. ! P~,chol. 55: 207-218, 1964. 36. Weasner. M. H., F. W. Finger and I S. Reid. Activity changes tinder food deprivation as a function of recording device..L comp. physiol. Psychol. 53: 470-474, 1960.