Physiology & Behavior, Vol. 16, pp. 381-385. Pergamon Press and Brain Research Publ., 1976. Printed in-the U.S.A.
Hyperactivity and Deficits in Problem Solving Following Superior Colliculus Lesions in the Rat CHARLES J. SMITH AND DOUGLAS A. WELDON
Department o f Psychology, State University o f N e w York at Buffalo, Buffalo N Y 14226 (Received 25 September 1975) SMITH, C. J. AND D. A. WELDON. Hyperactivity and deficits in problem solving following superior colliculus lesions in the rat. PHYSIOL. BEHAV. 16(4) 381-385, 1976. - Animals with bilateral superior colliculus lesions or control operations were tested for problem solving ability in a Hebb-Williamsclosed field and for locomotor activity and emotionality in an open field. Experimental animals were significantly both hyperactive and deficient in maze performance. Activity and maze performances were significantly related in the experimental animals but not in controls. The 2 groups did not differ in emotionality as measured by defecation. The results were interpreted as supporting the current theory that the superior colliculus is functionally involved in attention and orientation. Superior coUiculus Problem solving
Vision
Orientation
Attention
Mazelearning
Locomotor activity
that the functions of the subcortical and cortical visual areas are closely interrelated has been well illustrated in the s t u d i e s o f u n i l a t e r a l c o l l i c u l a r damage producing hemianopia and ipsiversive circling which can be ameliorated by contralateral cortical ablation [20,35]. Although Freeman and Papez [8] found that animals with colliculus lesions exhibited no savings of a preoperatively learned brightness discrimination, the implications of their results are not clear since no control group was included in their experiment. One very sensitive measure of problem solving ability in the rat has been the Hebb-Williams closed-field test [16]. The test requires that the animals solve a series of 12 simple maze problems, and by definition involves certain orientative and discriminative abilities. The present experiment was designed to test the effects of superior colliculus lesions on problem solving ability in this test with the hypothesis that if orientative abilities of hooded rats were impaired by collicular damage, then those animals would show deficits in closed-field test performance. Another area of interest concerning the functions of the superior colliculus in rodents is its role in locomotor activity [ 1, 2, 12, 19]. Results of such investigations appear to be strongly dependent on conditions of measurement. The present study assessed the effects of collicular lesions on locomotor activity in a simple condition of constant lighting and 1 level of illumination. Emotionality as measured by counts of fecal boluses [ 14] was also investigated.
RECENT theorizing on the organization of the mammalian visual system has involved the concept of 2 relatively independent neuronal systems. One o f these, the retinogeniculo-striate system, is fairly clearly identified with discriminative aspects of form vision. The functions of the other, the retino-tectal-pulvinar-temporal system, are less clearly appreciated, but seem to involve orientation and attention, and at least in some species may subserve form discrimination in the absence of the geniculo-striate system [ 5 , 3 4 ] . Electrophysiological studies have shown that neurons in the visual cortex respond to trigger features of varying degrees of complexity, and that orientation and size are frequently critical [18]. Neurones in the superior colliculus, in contrast, respond without orientation preference and usually are not specific for size [ 11 ]. In addition, electrical stimulation of the colliculus elicits movements of the eyes reminiscent of visual search [29], and the deeper layers receive information from sensory systems other than visual, suggesting functions which extend beyond vision [37,40]. In rodents, the concept of 2 visual systems seems to provide an adequate explanation for the experimental results. Although bilateral lesions of the superior colliculus do not produce deficits in actual discrimination abilities [3, 8, 9, 22, 23, 24, 30, 39], deficits have been observed in the ability of hamsters to approach the correct alley of a T maze [30] and of rats to jump from a platform to a white box situated among various black boxes [3 ]. The fact
1This research was supported by a subvention allocated by the Institutional Funds Committee, SUNY at Buffalo. We are indebted to Mrs. Dorothy Budzynski for careful preparation of the histological material. These results were presented at the 36th Annual Meeting of the Canadian Psychological Association, Quebec, P.Q., 1975. 381
382
SMITH AND WELDON METHOD
Animals The 31 male Long-Evans rats, purchased from Blue Spruce Farms, were 90 days old at the time of operation and were randomly assigned to superior colliculus lesion (n = 17) and control (n = I0) groups. Three rats failed to perform adequately and were dropped, and one died. The animals were housed in standard 18 × 20 x 25 cm rat cages and maintained at 22 + 1° C on a 14:10 l i g h t - d a r k schedule throughout the experiments (lights on: 0400 hr).
initially placed on the start box side of that barrier (see Fig. 1). A small fan was placed directly under the center of the maze to mask noises. The maze was cleaned with a dilute alcohol solution after completion of each animal's trials. Observations were made between 1800 and 0100 hr.
I! b tl s "S
Surgery
.J
Animals were anesthetized with 3 ml/kg IP Equi-Thesin (Jensen-Salsbery Laboratories), shaved, and placed in a stereotaxic apparatus. A 3 cm incision was made in the scalp, the skull was scraped clean, and four holes were drilled in the skull at the appropriate coordinates. A stainless steel electrode insulated with Insl-X, except for 0.5 mm at the tip, was directed toward the superior colliculus. In the experimental animals, 2 radio-frequency lesions (25 mA for 15 sec) were made in each colliculus at Skinner [32] coordinates: A 1.05, L 1.5, V 2.0 and P 0.25, L 1.5, V 1.5, with reference to an anal electrode, using a Radionics, Inc. model RFG-4 lesion maker. In control animals the electrode was directed to the surface of the colliculus but current was not passed. The wound was then closed with surgical silk sutures and dusted with sulfathiazole powder.
Closed-field Test Apparatus. The apparatus was a Hebb-Williams closedfield maze [28], modified so that the animals could return to the start area without handling between trials. Figure 1 illustrates the modified maze and a representative example of a Hebb-Williams closed-field problem. The maze was 75 × 75 × 1 0 cm , and the alleys were 1 0 c m wide and 1 0 c m high. All walls were painted black and the floor was painted light gray. The maze floor was divided into 30 13 cm squares with thin black lines. A clear acrylic plastic lid was attached with hinges to each of the alleys and the goal box. Barriers were painted black and had aluminum L brackets attached to the tops. Machine bolts and wing nuts lield the barriers firmly to a 6 mm acrylic top. One-way acrylic doors were suspended from hinges between the maze and the goal box and between the alleys and the start area to eliminate retracing. The floor of the maze was covered with clear acrylic for ease of cleaning. Lighting was provided by fluorescent lamps, yielding an illumination level of 5.6 Lux. Procedure. Five days following operation, animals were placed on a 23 hr deprivation schedule. Two days later, pretraining began according to Rabinovitch and Rosvold [28] with the following exceptions. Animals were introduced to the maze in groups (n = 3 or 4) for 2 days and subsequent pretraining consisted of individual sessions of either 7 trials or 10 rain. Animals received 0.5 g wet food upon entering the goal box. After all animals had reached a criterion of 7 trials in 50 sec (Day 17) training began, using the standard 12 test problems. Three animals that were not performing 7 trials in 10 min were dropped from the experiment at this point. After each day's 7 trials, animals were fed for 1 hr on a wooden feeding stand. A barrier blocking one of the alleys was alternated daily, and animals were
.a. £?
tl I! !
FIG. l. Hebb-Wiltiams closed-field maze modified after Rabinovitch and Rosvold [28]. One-way swinging doors (d) restricted passage from the goalbox (GB) back to the start area (S) via the outside alley only. Barriers (b) were alternated daily, and for the initial trial, animals were placed on the start area side of the barrier. Animals ran 7 trials without handling before being removed.
Open-field Test Apparatus. A wooden open-field, 1 m square and 45 cm high, was divided into 16 equal squares by black lines. The floor was covered with tinted acrylic for ease of cleaning. The illumination level was 6.0 Lux. Procedure. Animals were placed in the open-field facing a corner, and during the following 2 min the number of squares entered with both front paws was counted. In addition, the number of fecal boluses deposited by each animal was recorded. The floor of the field was cleaned with a dilute alcohol solution after each animal's test session. Animals were run in this experiment on the night following the last closed-field problem between 2000 and 2200 hr. Histology. Animals were perfused with 0.9% saline followed by a 10% Formalin-saline solution while deeply anesthetized. Brains were blocked, embedded in celloidin, and sections were stained with cresyl violet. RESULTS
Anatomical Findings All animals in the experimental group were found to have lesions of the superior colliculi, the largest and smallest of which are shown in Fig. 2. In approximately half the animals the lesions also involved a small area of the medial geniculate body, the pretectal areas and central gray,
COLLICULUS, PROBLEM SOLVING AND ACTIVITY
383 TABLE 1 SPEARMAN RANK CORRELATIONSBETWEEN BEHAVIORALRESULTS AND DEGREE OF DAMAGETO NONCOLLICULARAREAS
0.6
Locus of Damage
Pretectal Cortex Medial Geniculate Central Gray
Behavioral Measure Closed-field Open-field (Errors) (Squares Crossed) - .40* .39 .15 .25
- .41 * .02 .04 .10
*p 0 .0 5 ) but not for openfield activity (rho = 0.23, p = ns). Behavioral Findings The number of errors for each problem were summed to give animals a total error score. The mean number of errors for the oontrol group was 136.1 and for the superior coUiculus lesion group was 238.4. A t test for independent means [41] showed the difference to be statistically significant (t = 2.97, d f = 25, p p > 0.05). An analysis of covariance of the data was attempted in order to investigate the lesion effects on maze performance with activity level held constant statistically, but the homogeneity of regression assumption was not met [41]. Although the correlation between the animals' activity in the open field and their error scores in the maze was high and statistically significant for the superior colliculus lesion group (Pearson r = 0.58, d f = 16, p
Hyperactivity and Deficits in Problem Solving Following Superior Colliculus Lesions in the Rat CHARLES J. SMITH AND DOUGLAS A. WELDON
Department o f Psychology, State University o f N e w York at Buffalo, Buffalo N Y 14226 (Received 25 September 1975) SMITH, C. J. AND D. A. WELDON. Hyperactivity and deficits in problem solving following superior colliculus lesions in the rat. PHYSIOL. BEHAV. 16(4) 381-385, 1976. - Animals with bilateral superior colliculus lesions or control operations were tested for problem solving ability in a Hebb-Williamsclosed field and for locomotor activity and emotionality in an open field. Experimental animals were significantly both hyperactive and deficient in maze performance. Activity and maze performances were significantly related in the experimental animals but not in controls. The 2 groups did not differ in emotionality as measured by defecation. The results were interpreted as supporting the current theory that the superior colliculus is functionally involved in attention and orientation. Superior coUiculus Problem solving
Vision
Orientation
Attention
Mazelearning
Locomotor activity
that the functions of the subcortical and cortical visual areas are closely interrelated has been well illustrated in the s t u d i e s o f u n i l a t e r a l c o l l i c u l a r damage producing hemianopia and ipsiversive circling which can be ameliorated by contralateral cortical ablation [20,35]. Although Freeman and Papez [8] found that animals with colliculus lesions exhibited no savings of a preoperatively learned brightness discrimination, the implications of their results are not clear since no control group was included in their experiment. One very sensitive measure of problem solving ability in the rat has been the Hebb-Williams closed-field test [16]. The test requires that the animals solve a series of 12 simple maze problems, and by definition involves certain orientative and discriminative abilities. The present experiment was designed to test the effects of superior colliculus lesions on problem solving ability in this test with the hypothesis that if orientative abilities of hooded rats were impaired by collicular damage, then those animals would show deficits in closed-field test performance. Another area of interest concerning the functions of the superior colliculus in rodents is its role in locomotor activity [ 1, 2, 12, 19]. Results of such investigations appear to be strongly dependent on conditions of measurement. The present study assessed the effects of collicular lesions on locomotor activity in a simple condition of constant lighting and 1 level of illumination. Emotionality as measured by counts of fecal boluses [ 14] was also investigated.
RECENT theorizing on the organization of the mammalian visual system has involved the concept of 2 relatively independent neuronal systems. One o f these, the retinogeniculo-striate system, is fairly clearly identified with discriminative aspects of form vision. The functions of the other, the retino-tectal-pulvinar-temporal system, are less clearly appreciated, but seem to involve orientation and attention, and at least in some species may subserve form discrimination in the absence of the geniculo-striate system [ 5 , 3 4 ] . Electrophysiological studies have shown that neurons in the visual cortex respond to trigger features of varying degrees of complexity, and that orientation and size are frequently critical [18]. Neurones in the superior colliculus, in contrast, respond without orientation preference and usually are not specific for size [ 11 ]. In addition, electrical stimulation of the colliculus elicits movements of the eyes reminiscent of visual search [29], and the deeper layers receive information from sensory systems other than visual, suggesting functions which extend beyond vision [37,40]. In rodents, the concept of 2 visual systems seems to provide an adequate explanation for the experimental results. Although bilateral lesions of the superior colliculus do not produce deficits in actual discrimination abilities [3, 8, 9, 22, 23, 24, 30, 39], deficits have been observed in the ability of hamsters to approach the correct alley of a T maze [30] and of rats to jump from a platform to a white box situated among various black boxes [3 ]. The fact
1This research was supported by a subvention allocated by the Institutional Funds Committee, SUNY at Buffalo. We are indebted to Mrs. Dorothy Budzynski for careful preparation of the histological material. These results were presented at the 36th Annual Meeting of the Canadian Psychological Association, Quebec, P.Q., 1975. 381
382
SMITH AND WELDON METHOD
Animals The 31 male Long-Evans rats, purchased from Blue Spruce Farms, were 90 days old at the time of operation and were randomly assigned to superior colliculus lesion (n = 17) and control (n = I0) groups. Three rats failed to perform adequately and were dropped, and one died. The animals were housed in standard 18 × 20 x 25 cm rat cages and maintained at 22 + 1° C on a 14:10 l i g h t - d a r k schedule throughout the experiments (lights on: 0400 hr).
initially placed on the start box side of that barrier (see Fig. 1). A small fan was placed directly under the center of the maze to mask noises. The maze was cleaned with a dilute alcohol solution after completion of each animal's trials. Observations were made between 1800 and 0100 hr.
I! b tl s "S
Surgery
.J
Animals were anesthetized with 3 ml/kg IP Equi-Thesin (Jensen-Salsbery Laboratories), shaved, and placed in a stereotaxic apparatus. A 3 cm incision was made in the scalp, the skull was scraped clean, and four holes were drilled in the skull at the appropriate coordinates. A stainless steel electrode insulated with Insl-X, except for 0.5 mm at the tip, was directed toward the superior colliculus. In the experimental animals, 2 radio-frequency lesions (25 mA for 15 sec) were made in each colliculus at Skinner [32] coordinates: A 1.05, L 1.5, V 2.0 and P 0.25, L 1.5, V 1.5, with reference to an anal electrode, using a Radionics, Inc. model RFG-4 lesion maker. In control animals the electrode was directed to the surface of the colliculus but current was not passed. The wound was then closed with surgical silk sutures and dusted with sulfathiazole powder.
Closed-field Test Apparatus. The apparatus was a Hebb-Williams closedfield maze [28], modified so that the animals could return to the start area without handling between trials. Figure 1 illustrates the modified maze and a representative example of a Hebb-Williams closed-field problem. The maze was 75 × 75 × 1 0 cm , and the alleys were 1 0 c m wide and 1 0 c m high. All walls were painted black and the floor was painted light gray. The maze floor was divided into 30 13 cm squares with thin black lines. A clear acrylic plastic lid was attached with hinges to each of the alleys and the goal box. Barriers were painted black and had aluminum L brackets attached to the tops. Machine bolts and wing nuts lield the barriers firmly to a 6 mm acrylic top. One-way acrylic doors were suspended from hinges between the maze and the goal box and between the alleys and the start area to eliminate retracing. The floor of the maze was covered with clear acrylic for ease of cleaning. Lighting was provided by fluorescent lamps, yielding an illumination level of 5.6 Lux. Procedure. Five days following operation, animals were placed on a 23 hr deprivation schedule. Two days later, pretraining began according to Rabinovitch and Rosvold [28] with the following exceptions. Animals were introduced to the maze in groups (n = 3 or 4) for 2 days and subsequent pretraining consisted of individual sessions of either 7 trials or 10 rain. Animals received 0.5 g wet food upon entering the goal box. After all animals had reached a criterion of 7 trials in 50 sec (Day 17) training began, using the standard 12 test problems. Three animals that were not performing 7 trials in 10 min were dropped from the experiment at this point. After each day's 7 trials, animals were fed for 1 hr on a wooden feeding stand. A barrier blocking one of the alleys was alternated daily, and animals were
.a. £?
tl I! !
FIG. l. Hebb-Wiltiams closed-field maze modified after Rabinovitch and Rosvold [28]. One-way swinging doors (d) restricted passage from the goalbox (GB) back to the start area (S) via the outside alley only. Barriers (b) were alternated daily, and for the initial trial, animals were placed on the start area side of the barrier. Animals ran 7 trials without handling before being removed.
Open-field Test Apparatus. A wooden open-field, 1 m square and 45 cm high, was divided into 16 equal squares by black lines. The floor was covered with tinted acrylic for ease of cleaning. The illumination level was 6.0 Lux. Procedure. Animals were placed in the open-field facing a corner, and during the following 2 min the number of squares entered with both front paws was counted. In addition, the number of fecal boluses deposited by each animal was recorded. The floor of the field was cleaned with a dilute alcohol solution after each animal's test session. Animals were run in this experiment on the night following the last closed-field problem between 2000 and 2200 hr. Histology. Animals were perfused with 0.9% saline followed by a 10% Formalin-saline solution while deeply anesthetized. Brains were blocked, embedded in celloidin, and sections were stained with cresyl violet. RESULTS
Anatomical Findings All animals in the experimental group were found to have lesions of the superior colliculi, the largest and smallest of which are shown in Fig. 2. In approximately half the animals the lesions also involved a small area of the medial geniculate body, the pretectal areas and central gray,
COLLICULUS, PROBLEM SOLVING AND ACTIVITY
383 TABLE 1 SPEARMAN RANK CORRELATIONSBETWEEN BEHAVIORALRESULTS AND DEGREE OF DAMAGETO NONCOLLICULARAREAS
0.6
Locus of Damage
Pretectal Cortex Medial Geniculate Central Gray
Behavioral Measure Closed-field Open-field (Errors) (Squares Crossed) - .40* .39 .15 .25
- .41 * .02 .04 .10
*p 0 .0 5 ) but not for openfield activity (rho = 0.23, p = ns). Behavioral Findings The number of errors for each problem were summed to give animals a total error score. The mean number of errors for the oontrol group was 136.1 and for the superior coUiculus lesion group was 238.4. A t test for independent means [41] showed the difference to be statistically significant (t = 2.97, d f = 25, p p > 0.05). An analysis of covariance of the data was attempted in order to investigate the lesion effects on maze performance with activity level held constant statistically, but the homogeneity of regression assumption was not met [41]. Although the correlation between the animals' activity in the open field and their error scores in the maze was high and statistically significant for the superior colliculus lesion group (Pearson r = 0.58, d f = 16, p
