Septal lesion and experiential influences on saline and ...

Physiology and Behavior, Vol. 12, pp. 951-959. Brain Research Publications Inc., 1974. Printed in the U.S.A.

Septal Lesion and Experiential Influences on
Saline and Saccharin Preference-Aversion
Functions

RICHARD G. BURRIGHT, PETER J. DONOVICK AND EDMOND ZUROMSKI 3

State University of New York at Binghamton, Binghamton, New York 13901

(Received 16 July 1973)

BURRIGHT, R. G., P. J. DONOVICK AND E. ZUROMSKI. Septal lesion and experiential influences on saline and
saccharin preference-aversion functions. PHYSIOL. BEHAV. 12(6) 951-959, 1974. - Relatively high (unpalatable)
concentrations of saline or saccharin (independent studies) presented in 24 hr choices with water were found to more
markedly and persistently suppress the subsequent preference of septal-lesioned rats for lower concentrations when
compared with any such shifts in preference displayed by operated-control rats. These data were used to support the
notion that the septal region is involved with a comparator mechanism which affects the animal's response to various
external and internal cues guiding consumption. In addition, wide individual differences in both groups were presented
and discussed to emphasize that future studies should be designed to clarify those uncontrolled genetic and/or early
experience variables which must serve, at least in part, to differentially bias the adult animal's consummatory choice
behavior.

Septal-lesions Water consumption Saline Saccharin Experiential history

AN IMPORTANT factor in the survival of an animal is the consumption generally increases (e.g., [3]), but such
decision to ingest or reject a food or liquid. The decision of changes can be sharply affected by the sensory conditions
toxicity vs. nutritive value must often be made prior to surrounding the meal. For example, adulteration with palat-
feedback from the gut, when the decision could have grave able sodium (Na) saccharin or unpalatable concentrations
consequences. While all senses might become involved in of quinine affect the intake levels of rats with septal lesions
such a decision, for the rat it is probable that smell, taste, more than comparable control animals (e.g., [1,6]).
and perhaps somatic senses would be most involved. However, it has become clear that septal damage alters the
O'Kelly's regulatory-system model [ 13 ] clearly points out degree, rather than the direction of the rat's behavioral
that consummatory behavior, while often bounded by response. Further, even though a typical septal animal may
need- and satiety-detectors, may be influenced by factors be statistically described and inferentially validated, indi-
which affect the organisms orientation to its environment, vidual patterns of response are clearly apparent and suggest
as well as the consummatory act itself. Young (cf., [21]), the importance of uncontrolled genetic and experiential
for example, has argued that consummatory behavior may factors. We have begun to examine some of the origins of
be drastically affected by preference-aversion factors individual response patterns by investigating the effects of
(hedonic processes) in conjunction with, and sometimes early pre-surgical rearing conditions upon subsequent adult
regardless of, the need-state of the individual organism. behavior [5]. The experiential history imposed between
Indeed, an acceptance or rejection response commonly weaning and surgery at 85 days of age markedly influenced
occurs within the same substance (cf., [16]); this bivalence a variety of adult rat behaviors, including fluid consump-
is undoubtedly the product of past experience, species speci- tion, and the effects of septal lesions were somewhat
fic factors, general need state, and the immediate environ- dependent upon the prior rearing conditions. In addition,
mental conditions surrounding the consummatory act. investigations concerned with more recent past experience
[2, 8, 15, 20] strongly imply that we must pay more atten-
Investigations of the role of the septal region in tion to both the pre- and post-surgical history of the animal
consummatory behavior have indicated that destruction of to clarify neuro-behavioral relationships.
this forebrain structure alters various components of inges-
tive behavior. Following septal lesions, food and water To further explore post-surgical and relatively recent

~This research was supported in part by NIMH Grant MH-15821. A partial report of the saline experiment was presented at the ABS-AIBS
bteetin_gs,Burlington, Vermont, 1969.

2We thank Barton Frolich, Michael Jacobson, and Charles Ruiz for assistingin the collection and analysis of data.
3Now at the University of Rhode Island.

951

952 BURRtGHT, DONOVICK AND ZUROMSKI

influences on consummatory behavior of normal and brain Experiment 2 Saccharin Choice
damaged rats we carried out two independent but parallel
experiments. In the first, we examined the effects of septal Twenty naive, male, Sprague-Dawley rats that weighed
lesions on preferential consummatory behavior by repeated 295-335 g at the time of surgery were maintained under
presentation of a series of saline concentrations in choice conditions similar to those in the saline experiment, but
with water. In the second, naive animals were similarly this study was conducted at a later date. Presurgical match-
exposed to a repetitive series involving Na saccharin concen- ing, surgery and histology were also the same. Following
trations. In both experiments, choice days were alternated surgery, measurement of daily, double bottle, water
with water days on which 2 tubes of water only were consumption was resumed for 13 days. Then, following a
present. The solution series was presented 4 times in a similar up-down order, a choice between the sodium salt of
consistent order, and each time the solutions used ranged saccharin (0.05, 0.10, 0.25, 0.50, 1.00, 2.00%) and water
from low (palatable) to high (unpalatable) concentrations. was introduced with interspersed water-water days. During
the first up-down series saccharin was always on the right
METHOD when present; during the second such series, saccharin was
on the left. All 6 concentrations were presented in both
Experiment 1 Saline Choice series, but 2.00% saccharin was only presented once in the
UR-DR series and once in the UL-DL series; all animals
Animals. Twenty naive, male, Sprague-Dawley rats that were returned to a week of daily water-water availability at
weighed between 260- 320 g at the time of surgery were the end of the choice period. The saccharin study required
individually housed in a vivarium where temperatures were about 9 weeks total post-surgery. Since all animals survived,
maintained between 21- 24°C and the lights were on 12 hr there were 10 septals and 10 controls throughout the
a day. saccharin study.

Procedure. Total daily fluid consumption was measured RESULTS
to the nearest ml with two, 100 ml capacity Richter tubes
mounted on each animal's cage. Agway rat chow was Histology. Figure 1 shows reconstructions of the
always available and the animals were weighed weekly smallest, the largest, and the most typical lesion damage
throughout the experiment. Surgical groups were matched produced in both experiments. Tl~ese large septal lesions
on the basis of mean preoperative water consumption. were quite similar to those previously produced in this
Animal cages were distributed over cage rack faces to laboratory (e.g., [3]) in that they bilaterally destroyed the
control for differences in the micro-environment of indi- major portion of the precommissural septum. No damage
vidual cages across groups. was seen in the preoptic nuclei. As has been usual with
these relatively large lesions, we were unable to relate either
Large, bilateral septal lesions were produced under extent or locus of the lesions to the individual variability in
aseptic conditions while the animals were anesthetized with consummatory behavior described below. None of the
Nembutal (50 mg/kg) supplemented by local application of surviving animals were discarded on histological grounds
Xylocaine, as previously described [3]. Control rats under- from either experiment.
went the same procedure, including drilling of the skull, but
the electrode was not lowered. Upon completion of behav- Growth functions. The weight data from both studies
ioral testing, animals were overdosed with Nembutal and confirmed previous findings [3] in that growth functions of
perfused with isotonic saline followed by 10% Formalin, the septal animals were consistently lower than, but parallel
and brains fixed in 10% Formalin. The brains were sec- to the growth of controls throughout the post-surgical
tioned using frozen tissue technique and every fifteenth measurement periods. The control-septal difference in
section was mounted. Sections were stained with thionin weight was on the order of 20--30 g in both studies.
and extent of damage was determined by microscopic
examination. Our data showed the typical (cf., [21]) finding of
highly idiosyncratic choice behavior (see discussion). As a
Following surgery, measurement of daily, double bottle, result, group tendencies regarding choice behavior are
water consumption was resumed for 2 weeks. Then, 2 described for each study and then non-parametric tech-
consecutive up-down (U-D) water vs. saline (0.08, 0.15, niques are used where appropriate to aid in summarizing
0.25, 0.45, 0.80, 1.10, 1.50, or 2.00%) series were pre- the statistically reliable group effects observed in both
sented on alternate days. On interspersed days there were saline and saccharin experiments. Mean difference scores
two bottles of water. (Note: all concentration values will be (solution-water) have been employed to describe the
referred to as % for convenience, but are actually gins of preference-aversion results. Analyses making use of either
solute/100 ml of solution, and thus may be readily trans- absolute amounts of the various solutions consumed or
formed to molar concentration (cf., [ 14] ).) During the first relative, percentage preference scores reflect similar effects.
up-down series, saline was always on the right (R) when
present, and the 2 lowest concentrations were not Experiment 1 Saline Choice
employed during the up-phase; during the second such
series, saline was on the left (L) and all 8 concentrations Following surgery, rats with septal lesions displayed the
were employed throughout. In this regard, side was con- typical increase in water consumption (2 wk. individual
founded with experience. Furthermore, 2.00% saline was total post surgery water intake/bodyweight; U = 8, n, = q,
only employed once in each such series. Following the n2 = 10; p = 0.002, 2-tailed). Group differences in total
entire choice period, all animals were returned to daily, water intake on water-water days increased somewhat
2 bottle water availability for an additional week; thus, the during the choice period of the experiment and remained
saline study required a total of about 11 weeks posl- quite stable regardless of the saline concentration presented
surgery. One septal animal died in surgery, and therefore on the choice day preceding the water-water day (choice
there were n = 9 septals and n = 10 controls in the saline period: Xseptal H20-~ 55ml/day; X control H~Ov
experiment. 45 ml/day).

SEPTAL LESIONS, EXPERIENCE AND PREFERENCE-AVERSION 953

~-0- I, I,+ o ' ,

I A • ,1

II "2 /2-/9 . \ 2-3

FIG. 1. Reconstruction of a small, medium, or large septal lesion. The typical lesion most closely resembled the medium lesion.

A somewhat different pattern was observed on choice saline choice days (3 days U-R, 5 days D-R, 5 days U-L, 5
days, where group differences in total intake (solution + days D-L), the median of the mean saline-water differences
water) were dependent upon whether hypotonic or hyper- was 12 ml for the septal groups and 15 ml for the control
tonic saline was presented in the choice. When hypotonic group (U = 37; not significant). The 10 hypertonic saline
saline was presented, the total consumption of the septal choice days (5 days U and D-R, and 5 days U and D-L) did
group was higher than the control group; but when hyper- show a lesion effect - median of the mean saline-water
tonic saline was presented, this difference in total intake on differences was - 3 7 ml for the septal group and - 1 0 ml for
choice days disappeared. The reason for this pattern is that the control group (U = 20; n, = 9, n: = 10; p = 0.05, 2-
the septal group consumed almost 10 ml/day more water tailed). However, such an overall analysis does not aid in
than controls on choice days regardless of saline concentra- clarifying the apparent dynamic differential experiential
tion but the control group consumed nearly that much effects suggested by Fig. 2.
more hypertonic saline than the septal group.
In the first ascending-descending series, the choice
In Fig. 2 the abscissa represents saline concentrations in exposure to hypertonic saline solutions produced a marked
the order in which they were presented on the 28 successive decrease in preference for hypotonic saline compared with
choice days in the saline experiment; thus, there is an the initially observed levels for both groups. In the second
ascending-descending series of concentrations passing series, the lesioned rats displayed this shift in relative
through 2% NaC1, followed by a second such series. preference even more dramatically. The controls, however,
showed a marked recovery in their preference for hypo-
The mean differences between saline and water tonic saline in the final, descending portion of the second
consumption are plotted for both the septal (solid lines) series.
and control (dashed lines) groups. Thus, Fig. 2 can be
viewed as representing 4 long-term preference-aversion An additional indication of differential experiential
functions for each group. In general, both groups preferred effects can be found in the mean side preference data
hypotonic saline to water (a positive difference), and obtained on days when only water was available. On the
preferred water to hypertonic saline concentrations (a water only days leading to the choice period, neither the
negative difference). Considering all 18 of the hypotonic septal nor control group displayed marked, nor clearly

954 BURRIGHT, DONOVICK AND ZUROMSKI

II0~- SHAILGINH E SHAILGIHNE I00
I00" I----I t- .... -t
80
90 .-(:? 60

80
tr 70
~to. 650 I

to

to ~ .

,to..o ),// %..0
ILl ~ ~

,=o_ -)0 / ] :0: l] / =o
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.o= I .~ I .='o1,.'N,.'518'o I .:~, ~ .de .do ~ .,~5 I .,,'o1,.'.~ ,'~1.,'o I .~5 I .o,,

.J5 .45 tJ I i.i .45 .I .I .45 I.o I tJ ,45 ,15

(2.0) (2.0)

gins SALINE X I00 (LOG SCALE)
I00 ml SOLUTION

FIG. 2. Saline experiment. The abscissa represents saline concentrations in the order in which they were presented on the
successive choice days in the saline experiment; there is an ascending-descending series of concentrations passing through
2% NaCI, followed by a second series. The mean differences between saline and water consumption are plotted on the

ordinate for both septal (solid lines) and control (dashed lines) groups.

different side preferences. But Table 1 shows that during, prior saline side. During the week after the choice period,
and immediately subsequent to the choice period, the side the septals' side preference had shifted about 13 ml toward
preference of the two groups was differentially shifted as a the side which water had been on during the last saline
function of saline choice experience. The control group was choice exposures.
moved toward a preference for the prior saline side when
saline concentrations had been low (0.80% or less) during Experiment 2 - Saccharin Choice
the ascending portions of both choice series, and during the
descending portion of the second series. However, when Absolute total water intake levels for both groups were
saline concentrations were low during the descending somewhat reduced compared to those in the saline study,
portion of the first choice series, or high ( 1.10% or greater) probably due to the difference in bodyweights between the
during both series, the control group's side preference was two studies (cf., [3]). However, water intake to body-
not markedly altered. During the post choice period week, weight measures on the 13 days post surgery indicated the
side preference of control animals had shifted about 6 ml typical increase in water consumption following septal
toward the last saline side exposures. It is clear from Table lesions (U = 11.5, n, = n2 = 10; p<0.02, 2-tailed). On the
1, however, that the septal group's side preference data water only days during the choice period, group differences
cannot be described in this manner. Relative to the side in total intake remained quite stable (choice period: Septal
preference which they displayed during the week prior to
the choice period, septals were more typically shifted H~ O ~ 48 ml, Control X H 2 0 ~ 39 ml).
toward a preference for the side on which water had been Absolute amounts and group differences in total intake
present during various choices with saline. Only when saline (solution + water) on saccharin choice days were again
concentrations were low during the descending portion of influenced as a function of concentration. That is, total
the first series and the ascending portion of the second intake was highest for both groups on days when 0.25%
series did the septal group shift their preference toward the saccharin was available, (Septal X = 97 ml; Control X =
89 ml), and lowest on days when 2.00% saccharin was

SEPTAL LESIONS, EXPERIENCE AND PREFERENCE-AVERSION 955

TABLE 1

SALINE STUDY: WATERONLY DAYS DURING AND FOLLOWING THE CHOICE PERIOD. MEAN AND RANGE OF
SIDE PREFERENCE CHANGES (NEAREST ML) TOWARD (+) OR AWAY FROM (-) THE PRIOR SALINE SIDE.*

EXPERIENCEt 2nd Series (Saline left)
1st Series (Saline right)

Post Lo Post Hi Post Lo Post Lo Post Hi Post Lo Post Choice

No. of days (3) (5) (5) (5) (5) (5) (7)
-4 -2 11 2 11 6
Control ll (-26:22) (-27:27) (-18:47) (-28:53)
(n = 10) (-16:39) -21 7 (-16:36) -12 (33:46)
(-83:15) 9 (-60:64) -3 (-84:43) 13
(Range) (-80:109)
(-64:65) (-122:38)
Septal -14
(n = 9) (-79:22)

(Range)

*All changes are expressed relative to the side preferences observed during the week prior to the choice period:
Control X (left-right) = - 4 ; Septal X (left-right) = 5.

tPost Lo refers to prior saline-choice days when saline concentrations were 0.80% or less (hypotonic); Post Hi refers
to prior saline-choice days when saline concentrations were 1.10% or greater (hypertonic). Post Choice refers to the week
of water only subsequent to the 56 day choice period.

present (Septal X = 57 ml; Control X = 40 ml). Septals aversion functions are virtually identical for both groups,
typically drank more saccharin and more water than con- and appear more similar in form to those observed for the
trols. However, on choice days involving 0.50% saccharin, control group during the first ascending-descending saccha-
the mean difference in total intake between septals and rin choice exposure series.
controls was only about 5 ml, and that difference was due
essentially to the amount of water consumed. Table 2 summarizes mean changes in side preference
during water only days as a function of the preceding
As seen in Fig. 3, and in contrast with the saline study, saccharin choice experiences. Both groups showed relatively
there was a general preference for almost all sodium strong right side preferences prior to the choice period. As
saccharin concentrations used. In fact, only when 2.00% reflected in the choice days' data, both groups showed
saccharin was available did both groups clearly take more marked shifts toward the prior saccharin side during the
water than solution. For the purpose of data analysis we ascending portions of both series when saccharin Concentra-
considered 0.05% through 0.25% saccharin as low concen- tions were low, but such shifts were at least considerably
trations, and 0.50% through 2.00% saccharin as high attenuated if not actually reversed following choice experi-
concentrations. On all 12 low saccharin choice days (3 days ence with the higher saccharin concentrations. During the
U-R, 3 days D-R, 3 days U-L, and 3 days D-L), the median week post choice, the control group's side preference had
of the mean saccharin-water differences was 73 ml for the not changed appreciably from that displayed prior to any
septal group and 62 ml for the control group (U = 38, not saccharin experience; but the septal group's side preference
significant). Similarly, an overall analysis of the 10 high had moved 16 ml toward (though not actually in favor of)
saccharin choice days (5 days U and D-R, and 5 days U and the side on which saccharin had been last presented.
D-L) showed no lesion effect - median of the mean
saccharin-water differences was 24 ml for the septal group Summary of Results of the Saline and Saccharin
and 28 ml for the control group (U = 48, not significant). Experiments
Again, however, differential experiential influences were
suggested by the data presented in Fig. 3. Table 3 shows that for both saline and saccharin the
range and distribution of total adulterated fluid consump-
In the first ascending-descending series of Fig. 3, it .can tion over all concentrations for both septal and control
be seen that rats with septal lesions initially consumed more animals was quite comparable, though very large. It appears
of the low concentrations of saccharin. Following experi- then that the hedonic value (positive and negative) of these
ence with unpalatable saccharin, intake in the previously solutions is highly idiosyncratic, though it differentially
highly acceptable lower concentrations during the descend- effected the response of the two groups. Thus, even when
ing portion of that series was depressed for both groups; presented with hypotOnic (palatable) saline for the first
however, the lesion group consumed less low concentration time, there was no significant overconsumption of the
saccharin than the control group subsequent to their septal group re controls. However, when presented with
exposure to the higher, less acceptable concentrations. hypertonic (unpalatable) saline solutions, the septals
During the second ascending-descending series, preference- showed a greater water preference than controls (MDN

956 BURRIGHT, DONOVICK AND ZUROMSKI

lie J ~S._AH_CICGHHA_RL~~. HIGH

I00 ~ - I00
80
90 ,o-
60
80 /9-- .~,
40
,~ 7 o / _ "o - 20

z 60 // 0
so -20
/
4o -40

30 5 II

2o .II0.o5

io

o

-IO \~// SACCHARIN STUDY
F, -20
~x -30 '~ ] CONT ROL ~- ----~ ~-n;IO)--~

-40 -" (n= I0) 1

-50 I SEPTAL ; tIIII

I"i I .05 I .25 I I.o I I.O I .25
.05 l 25 I 1.0 I 1.0 I 25 1.05
.I0 .50 (2.0) 50 .10 ,10 .50 (2.0) .50

gm SACCHARIN XI00(LOGSCALE)

I00 ml SOLUTION

FIG. 3. Saccharin experiment. The abscissa represents saccharin concentrations in the order in which they were presented
on the successive choice days in the saccharin experiment; there is an ascending-descending series of concentrations passing
through 2% Na saccharin, followed by a second series. The mean differences between saccharin and water consumption are

plotted on the ordinate for both septal (solid lines) and control (dashed lines) groups.

Mean Saline-Water difference over all 10 days of hypertonic 3.75;U = 16, n, = n2 = 10;p<0.02, 2-tailed).
choice; Septals = - 3 7 . 1 0 , Controls -- - 1 0 . 6 5 , U = 20, n, = Thus, when presented with a water-saline choice (but for
9, n~ = 10; p = 0.05, 2-tailed). The greater septal aversion
for hypertonic saline and its apparent differential experi- a single bottle of saline; cf., [2,4]) there is no statistical
ential effect is also reflected in the fact that the differ- evidence here of enhanced saline preference by the septal
ence between hypotonic saline preference during the lesioned group anywhere in the range of saline concentra-
up vs. down portions of the 2 series was greater in the tions employed. But septals showed a greater preference for
septals than the controls (MDN Mean change; Septals= water over hypertonic saline concentration than did con-
27.48, Controls = 1.32, U = 21, n, = 9, n2 = 10; 0.05 < p < trois, and that experience resulted in a more marked
0.10, 2-tailed). suppression of hypotonic saline preference than displayed
by the control group. (However, see [18]; Table 3 and
When the saccharin study is considered, a somewhat discussion.) On the other hand, the response to the low
different picture emerges; the septal group initially showed concentrations of saccharin used here was initially en-
a greater preference for low (0.05, 0.10, and 0.25%) hanced by septal lesions; but that enhancement was elim-
concentrations (MDN Mean Saccharin Water difference, inated following experience with higher (less palatable)
first up-run; Septals = 104.33; Controls = 68.66; U = 23; saccharin solutions in this choice situation, even though the
n; = n~ = 10; p = 0.05, 2-tailed), but displayed little differ- septal group displayed little if any difference from controls
ence in their acceptance of high (0.05, 1.00, and 2.00%) in their rejection of those higher saccharin concentrations.
concentrations (MDN Mean Saccharin - Water difference, The directions of group side preference shown in Tables 1
all 10 days of high saccharin choice; Septals = 24.55; and 2 generally fit the differential experiential patterns just
Controls = 28.15; not significant). Nonetheless, a differen- described. But the range scores provided in those two tables
tial experiential effect (preference for low saccharin also serve to underline the extreme lability of individual
concentrations during both of the up vs. down phases) was differences in side preference habits which also occur in
apparent (MDN Mean change; Septals = 34.08; Controls = both lesioned and intact animals.

SEPTAL LESIONS, EXPERIENCE AND PREFERENCE-AVERSION 957

TABLE 2

SACCHARIN STUDY: WATER ONLY DAYS DURING AND FOLLOWING THE CHOICE PERIOD. MEAN AND
RANGE OF SIDE PREFERENCE CHANGES (NEAREST ML) TOWARD (+) OR AWAY FROM (-) THE PRIOR

SACCHARIN SIDE. *

EXPERIENCE{

1st Series (Saccharin right) 2nd Series (Saccharin left)

Post Lo Post Hi Post Lo Post Lo Post Hi Post Lo Post Choice

No. of days (3) (5) (3) (3) (5) {3) (7)

'X 25 8 7 19 6 7 2
Control (5:50) (-19:37) (-28:34) (-10:45) (-27:34) (-23:31) (-31:32)
(n = 10)

(Range)

.X 34 6 -6 26 10 10 16
Septal (1:57) (-42:44) (-59:39) (-19:50) (-39:38) (-60:46) {-36:60)
(n = 10)

(Range)

*All changes are expressed relative to the side preferences observed during the week prior to the choice period:
Control X (left-right) = -16; Septal .X (left-right) = -21.

{Post Lo refers to prior saccharin-choice days when saccharin concentrations were 0.25% or less; Post Hi refers to prior
saccharin-choice days when saccharin concentrations were 0.50% or greater. Post Choice refers to the week of water only
subsequent to the 44 day choice period.

DISCUSSION genetic variability and uncontrolled early environmental
variables should be expected to interact with later behavior.
Following lesions of the septum there are changes in Indeed, we have shown [5] that both the level of water
reactivity to sensory cues guiding consumption such that consumption and the degree of reactivity exhibited follow-
rats increase their intake of some palatable fluids [ 1] and ing septal lesions is in part determined by pre-surgical rear-
greatly strengthen their rejection of unpalatable fluids ing conditions. However, data such as that presented in this
[1,6]. In general, compared with intact animals, the paper and elsewhere [2,20] indicate the importance of
bidirectional limits of reactivity for rats with large septal more recent and post-surgical experiential history as well.
lesions appear to be more extreme.
Attempts to measure the impact of recent experiential
In the present study, the most apparent group changes history have been of methodological concern for quite
were that long-term post-surgical choice exposure to less some time (cf., [9, 12, 17]). Factors such as the number of
palatable solutions decreased the subsequent preference for choices allowed and .position habits clearly influence
more palatable solutions, rather than vice versa. Such consummatory data. Certainly, this study has confounded
changes were generally greater for animals with septal possible order effects. However, there is no simple resolu-
lesions than for control rats, and they also appeared to tion to such methodological problems. For example,
persist for a longer period of time in the septal group. experimenter manipulation of bottle position in a 2-choice
Comparison of these findings with those of Flaherty and situation to achieve control of various aspects of sequential
co-workers [7,8] strongly suggest that factors such as the stimalus occurrences within a finite experimental situation
quality, temporal ordering of solution presentations, and can become quite complex (cf., [17]); but even if certain
the manner of presentation are critical variables. characteristics of stimulus balance are achieved, such
balancing cannot itself remove idiosyncratic animal behav-
Of equal interest is the origin of the wide individual iors. Despite such methodological problems, septal lesions
differences in preference which exist in albino rats, raised did interact with the common history of experimentally
and maintained under uniform conditions. In the fluids defined stimulus exposure which we imposed upon all
tested here, these differences appear greatest on the positive animals in this study. However, markedly different indivi-
and neutral portions of the hedonic spectrum, but also dual patterns of consumption were observed and described
appear in the tolerance for aversive solutions. There have within both the normal and the lesioned animals; i.e., septal
been several investigations (e.g., 10, 11, 1 9 ] ) w h i c h suggest lesions per se did not override, nor clearly delimit the
that early experience influences consumption in the adult. expression of individual differences. Indeed, the data
We suggest that, especially in a species such as the rat which presented here should not and cannot be construed as
typically has large litters, the uniform treatment may in representing a completely unconfounded, parametric
fact be quite variable. Thus, depending on factors such as analysis which thoroughly specifies the precise nature
litter size, quality of mothering, and activity of a pup, the and/or quantitative values of those post-experiential vari-
amount fed (or conversely deprived) will vary. Surely,

958 BURRIGHT, DONOVICK AND ZUROMSKI

TABLE 3
INDIVIDUAL MEAN INTAKE (NEAREST ML) DURING CHOICE PERIOD

SALINE CHOICE

Septals Controls

28 Choice Days 28 Water Days 28 Choice Days 28 Water Days
X Water X Water
Rat No. Saline X Water Rat No. X Saline X Water

10a 86 18 70 14a 85 21 62
16a 54 39 56
19a 51 18 54 13a 60 24 42
2a 32 27 49
18a 22 21 80 20a 45 16 40
3a 19 36 42
la 15 46 49 7a 38 22 42
17a 12 37 35
12a 4 44 37 5a 27 20 38
... . 42
52 4a 24 24

58 21a 24 24

46 23a 19 22

49 9a 16 25

l l a 10 36

SACCHARIN CHOICE

Rat No. Septals 22 Water Days Rat No. Controls 22 Water Days
22 Choice Days X Water 22 Choice Days X Water
21b X Saccharin X Water 23b ,X Saccharin X Water
2b 72 17b 53
93 24 54 25b 93 12 48
16b 88 8 44 84 6 40
8b 77 5 60 lb 78 9 36
3b 72 20 41 20b 65 4 38
67 9 47 26b 55 6 32
24b 61 15 44 50 5 36
12b 53 13 32 6b 46 13 33
lib 48 9 45 4b 42 10 45
15b 47 15 44 22b 39 13 33
13b 39 15 5b 36 12

ables which will differentially influence the consummatory the CNS in the control of behavior.
behavior of septal lesioned rats vis-a-vis normal animals. But Finally then, we suggest that the septal region, in
we do believe that these data, especially in conjunction
with other findings which are emerging, serve to amplify conjunction with other limbic structures [6] is involved
the need for careful experimenter concern with the with a comparator mechanism which controls the reactivity
ontogeny of individual differences and the impact of short of vertebrates to both internal and external cues surround-
and long-term, pre- and post-surgical, experiential (and ing the consummatory situation, and that such reactivity is
genetic) influences when attempting to clarify the role of biased by the experiential (and genetic) history of the
individual animal.

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