Psychological Reports, 1975, 37, 981-982. @ Psychological Reports 1975 CAUDATE NUCLEUS LESIONS A N D REARING RESPONSES
ROBERT J. KIRKBY Lincoln Institute Carlton, Victoria, Australia Summary.-Lesioned rats were observed for 10-min. in a wooden enclosure. Frequencies of rearing were greatest for unoperated, frontal lesioned, and least for those with caudate lesions. Increased arousal of rats with caudate lesions was suspected. "Rearing" or the rising up on hindlegs is a response commonly observed in rats exploring a novel environment. Subjective observations carried out during a series of earlier studies (2, 3 ) suggested chat rats with lesions involving the bilateral caudate nuclei tended to rear less than unoperated rats. To test this hypothesis experimentally the present research was carried out. Ss were 38 male Wistar rats supplied by C.S.I.R.O. Clunies Ross Laboratories. When Ss were 3 or 4 mo. old, 12 Ss received bilateral lesions of the anterodorsal caudate nucleus, 13 Ss received bilateral lesions of the dorsolateral frontal cortex, and 13 Ss served as unoperated controls. Details of surgery and histological procedure have been outlined previously (2, 3). The apparatus was a wooden enclosure (84 X 84 X 40 cm. high). The inside walls and floor of the enclosure were painted grey. The apparatus was placed on the floor of the laboratory directly below a 40-w. fluorescent light. The test procedure was as follows: S was placed in one corner of the apparams and observed for a 10-min. period. During this time frequency of rearing, either unsupported or with one or both forepaws against the wall, was recorded. In between Ss the apparatus was wiped out with a damp rag. Ss were tested once, 65 to 76 days after surgery, when they were approximately six months old. Prior to this they had been tested on a series of spontaneous alternation casks involving equivalent treatment for all groups ( 3 ) . Histological examination indicated that the extent and location of lesions within the caudate nucleus and frontal cortex were very similar to those previously reported in detail ( 2 ) . Mean frequencies of rearing for each group were: caudate = 4.5; frontal = 11.6; unoperated = 11.9. Group differences were tested by analysis of variance using the technique of planned contrasts. The caudate rats showed significantly less rearing than the frontal and unoperated racs (F3,34= 3.83, p < .025). Between the frontal and unoperated groups 1.00). there was no significant difference ( F That the frontal rats, with lesions involving the motor cortex, reared as frequently as unoperated rats suggests that the reduced incidence of rearing in the caudate racs was not associated with a motor impairment. Decreased rearing - -
ROBERT J. KIRKBY Lincoln Institute Carlton, Victoria, Australia Summary.-Lesioned rats were observed for 10-min. in a wooden enclosure. Frequencies of rearing were greatest for unoperated, frontal lesioned, and least for those with caudate lesions. Increased arousal of rats with caudate lesions was suspected. "Rearing" or the rising up on hindlegs is a response commonly observed in rats exploring a novel environment. Subjective observations carried out during a series of earlier studies (2, 3 ) suggested chat rats with lesions involving the bilateral caudate nuclei tended to rear less than unoperated rats. To test this hypothesis experimentally the present research was carried out. Ss were 38 male Wistar rats supplied by C.S.I.R.O. Clunies Ross Laboratories. When Ss were 3 or 4 mo. old, 12 Ss received bilateral lesions of the anterodorsal caudate nucleus, 13 Ss received bilateral lesions of the dorsolateral frontal cortex, and 13 Ss served as unoperated controls. Details of surgery and histological procedure have been outlined previously (2, 3). The apparatus was a wooden enclosure (84 X 84 X 40 cm. high). The inside walls and floor of the enclosure were painted grey. The apparatus was placed on the floor of the laboratory directly below a 40-w. fluorescent light. The test procedure was as follows: S was placed in one corner of the apparams and observed for a 10-min. period. During this time frequency of rearing, either unsupported or with one or both forepaws against the wall, was recorded. In between Ss the apparatus was wiped out with a damp rag. Ss were tested once, 65 to 76 days after surgery, when they were approximately six months old. Prior to this they had been tested on a series of spontaneous alternation casks involving equivalent treatment for all groups ( 3 ) . Histological examination indicated that the extent and location of lesions within the caudate nucleus and frontal cortex were very similar to those previously reported in detail ( 2 ) . Mean frequencies of rearing for each group were: caudate = 4.5; frontal = 11.6; unoperated = 11.9. Group differences were tested by analysis of variance using the technique of planned contrasts. The caudate rats showed significantly less rearing than the frontal and unoperated racs (F3,34= 3.83, p < .025). Between the frontal and unoperated groups 1.00). there was no significant difference ( F That the frontal rats, with lesions involving the motor cortex, reared as frequently as unoperated rats suggests that the reduced incidence of rearing in the caudate racs was not associated with a motor impairment. Decreased rearing - -
