Brain Research, 93 (1975) 223-240
223
© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
I N T E R M A N U A L T R A N S F E R IN T H E M O N K E Y A M O U N T OF C A L L O S A L S P A R I N G
AS A F U N C T I O N
OF
M. HUNTER, G. E T T L I N G E R AND J. J. MACCABE
Institute of Psychiatry, De Crespigny Park, London SE5 8AF (Great Britain) (Accepted February 19th, 1975)
SUMMARY
The effects of commissure section, task difficulty and overtraining on the intermanual transfer of tactile learning have been examined. Twenty-one rhesus monkeys were allocated to 4 groups. One group was subjected to complete transection of the corpus callosum, massa intermedia and posterior commissure. Some of this group also sustained a cerebellar section. A second group received a similar division of the commissures but with part of the posterior body of the corpus callosum left intact. A third group received similar division of the commissures but with the posterior commissure left intact. The fourth group formed an unoperated control group. Animals with only the posterior commissure left intact showed little or no transfer. Animals with partial callosal lesions showed significantly greater transfer than animals with total transections, but were impaired relative to the unoperated controls. Estimates have been made of the number of callosal fibres left intact in the animals with partial callosal lesions. These estimates have been correlated with transfer. The correlation was significant on only one task. Neither task difficulty nor overtraining were found to affect transfer significantly. The comparison of transfer of the submodalities of size and roughness was inconclusive.
INTRODUCTION
Recent anatomical investigations8,13 have found that there are no direct interhemispheric connections between areas of SI which represent the distal parts of the limbs - - the hand and foot areas. This suggests that the forebrain commissures, in transferring learned patterns of behaviour from one hemisphere to the other, are not transferring at the level of the primary sensory areas. The interhemispheric projections of parietal cortex have been studied in detaiP 3, but up to now no detailed attempt has
224
been made to clarify the relationship between these projections and the transler of tactile learning. The evidence in the literature concerning the intermanual transfer of tactile learning is conflicting. Some investigators 2,1° have concluded that sectioning of the corpus callosum (CC) completely arrests interhemispheric transfer, while others '~,~,11, 15 have found variable amounts of transfer. The explanation for these inconsistent results may lie in the parameters affecting the behavioural training. It has been suggested 15 that the difficulty of the learning task may influence the amount of transfer, and in a recent study u it was suggested that both task difficulty and amount of overtraining may have an effect. The present experiment is an attempt to correlate interhemispheric transfer of tactile learning with specific numbers of fibres of the posterior body of the CC. Further, it is designed to analyze the possible roles of task difficulty and amount of overtraining in intermanual transfer. Finally, it is designed to investigate the possible involvement of the posterior commissurO 1 in the transfer of tactile learning. METHODS
Twenty-one rhesus monkeys were the subjects in this experiment. The 21 animals were divided into 4 groups. Animals T1-T4 (total splits) were intended to have a complete division of the CC, of the posterior commissure (PC) and the massa intermedia (MI); animals T5-T7 were intended to have similar lesions and in addition a midline sagittal section along the vermis of the cerebellum; animals PI-P5 (partial splits) were intended to have a complete division of the PC and the MI but incomplete division of the CC, leaving a 2-3 mm band of fibres intact in the posterior third ofthe body of the CC; C 1-C2 (control splits with PC intact) were intended to have complete division of the CC and of the MI; and U1-U7 formed an unoperated controI group. (It was considered possible that the additional transection of the cerebellum in the total splits T5-T7 would affect transfer. However, this was not found, Therefore their results have been combined with those of animals Tl-T4.)
Operations All the surgical operations were carried out in aseptic conditions. After a large bilateral cranial bone flap had been raised the dura mater was incised on the left side and widely reflected back to the sagittal sinus. The transections were then made by aspirating with a small-gauge sucker under direct vision, with the aid of a binocular microscope. For animals T5-T7 the midtine bisection of the cerebellum was carried out at a second operation 16, 3 and I0 months respectively after the sections of the CC, PC and MI. The cerebellum was approached through an opening made with rongeurs in the occipital bone. The section along the midline extended ventrally through the vermis to the medulla, dividing the cerebellar cortex and separating the cerebellar nuclei. Again the section was carried out under direct vision. Following surgery 4 animals (T1, T2, P4 and P5) suffered from a mild transient right hemiparesis and one animal (T4) from a permanent right herniparesis. Also 3
225 a n i m a l s (T3, T4 a n d P5) suffered i n t e r m i t t e n t right-sided focal epileptic seizures for s h o r t p e r i o d s o f time, usually less t h a n one day. T h e recovery o f all other a n i m a l s was either uneventful, or, as in the case o f the a n i m a l s with total splits plus a cerebellar transection, h a d been c o m p l e t e d some m o n t h s before the b e h a v i o u r a l testing o f this e x p e r i m e n t began. Histological procedures and findings
F o r a n i m a l s T l, T3 a n d T5, c o r o n a l sections were t a k e n at a thickness o f 25/~m and every twentieth section was stained with the fibre stain a n d cell counter-stain o f Klfiver a n d B a r r e r a 9. F o r a n i m a l s P1-P5, C1 a n d 2, a n d U 4 the b r a i n was divided sagittally a l o n g the midline. The left side o f the b r a i n was t a k e n in P I - 5 , C2 a n d U4, a n d the right side in C I a n d then these b r a i n halves were c o r o n a l l y sectioned and stained with the K l f i v e r - B a r r e r a m e t h o d . The o t h e r brain halves had smaller blocks cut f r o m them. The blocks o f P1-5 included the p o s t e r i o r p a r t o f the CC, the blocks o f C 1 - 2 included the PC, a n d the b l o c k o f U 4 included the whole o f the C C a n d PC. These blocks were sectioned sagittally at a thickness o f 10/tin a n d were stained with either a G l e e s - M a r s l a n d 12 stain (P2), a G r o s s - B i e l s c h o w s k y stain (C1), or a Hfiggqvist 7 stain (P1, 3, 4 a n d 5; C1 a n d 2; a n d U4). The lesions o f T 2 a n d 4 were confirmed by gross analysis at p o s t - m o r t e m b r a i n cut. The b r a i n s o f a n i m a l s T6 a n d 7 are still to be processed. The fibres left intact in the C C o f the p a r t i a l splits a n d in U4 a n d the fibres of the P C in the c o n t r o l splits a n d U 4 were counted, using a m e t h o d based on that of De M y e r 1. R a n d o m samples o f the a r e a left intact were p h o t o g r a p h e d at × 500 magnification. The n u m b e r o f intact fibres was c o u n t e d f r o m the p h o t o m i c r o g r a p h s . The total a r e a o f intact fibres was estimated. A n estimate o f the total n u m b e r o f intact fibres was derived f r o m these values. TABLE I E S T I M A T E S O F T O T A L N U M B E R S OF I N T A C T F I B R E S
All brains were studied with H/iggqvist stain 7 except where shown otherwise. Animal
Estimate of total area of intact fibres
Mean fibre count from n samples of 0.0324 sq. mm and ranges
Estimate of total number of intact fibres
PI P2 (Glees-Marsland) P3 P4 P5 C1 (Hfiggqvist stain) C1 (Gross-Bielschowsky) C2 U4 U4
0.162 sq. rnm of CC 2.137 sq. mm of CC
453 (n = 2) (486/420) 1,227 (n -- 4) (1320/1124)
2,265 80,946
0.798 sq. 3.915 sq. 1.457 sq. 0.948 sq.
of CC of CC of CC of PC
464 (n -- 4) (638/314) 496 (n -- 4) (525/440) 1,042 (n = 4) (1148/940) 707 (n 4) (816/575)
11,428 59,901 46,869 20,687
0.971 sq. mm of PC
742 (n = 4) (830/667)
22,253
mm mm mm mm
1.999 sq. mm of PC 578 (n = 4) (602/568) in posterior body of CC 1,350 (n -- 4) (1494/1104) 0.965 sq. mm of PC 1,013 (n = 4) (1079/968)
35,657 41,667 fibres/sq, mm 30,182
226 P2
P1
P3
P4
P5
Fig. 1. Diagrammatic representation of the position in the corpus callosum of the anterior and posterior boundaries of the spared segment (black), reconstructed from the cross-sectionS with reference to the posterior limits of the splenium.
The coronal sections confirmed the intended lesions with 2 exceptions. Firstly, in P3 a few fibres anteriorly in the genu of the CC were left intact, and a small area of the dorsal MI appears to be uncut. Secondly, in T3 a few fibres at the posterior end of the PC have been spared. The mid-sagittal division of those brains, for which sagittal as well as coronal sections were taken, occasionally resulted in parts of the lesions being included in the sagittal blocks. Consequently, not all the lesions appeared in the coronal slides. This occurred in PI and 3 and C2. However, the intended lesions were confirmed in all slides in which they were visible. In addition to the intended lesions the anterior commissure was cut in all animals, although not completely cut in P2; the habenular commissure was cut in TI and 3, and in P5; the anterior part of the commissure of the superior colliculus was cut in T1 and P5. the lateral ventricles were abnormally dilated in T3. P1. P2, P3, P4, P5 and C2; there was a small stab wound in the hypothalamic area m T3; a little damage to the hypothalamus in P4 and 5 and to the pineal body of P5. The gross analysis at post-mortem brain cut o f T 2 and T4 confirmed the intended lesions and in addition showed section of the anterior commissure and abnormal dilatation of the lateral ventricles. The counts of intact fibres made from the sagittal sections are shown in Table I : the position of the intact fibres of the partial animals in Fig. 1.
Behavioural testing All behavioural training was carried out in the dark in a Wisconsin General Testing Apparatus (WGTA). In order that the animals would only use one hand at a time for the discrimination tasks the other hand was restrained by attaching a weighted rubber ball to the wrist by means of a bracelet. The test objects used (see Figl 2) were chosen to provide a range of difficulty, based on learning scores in previous experiments, and to compare different sub-modalities within the somatic sense modality. Different degrees of overtraining were also used. Stage I of training, cylinder and sphere, was a preliminary preoperative task (see Table II). After postoperative reten-
227
i _J Fig. 2. T h e pairs of test objects used in behavioural training. Choice of the object to the left o f each pair was rewarded (except d u r i n g training o f the second h a n d o n C a n d D, see text). T A B L E 11 P R E - A N D P O S T - O P E R A T I V E P E R F O R M A N C E O N A N EASY T A C T I L E S H A P E D I S C R I M I N A T I O N TASK.
(cylinder vs. sphere, stages I a n d 1! of training) Figures for pre-op a n d post-op retention represent trials to reach a level of p e r f o r m a n c e o f 180 correct responses in 200 consecutive trials. Figures for 'savings' have been calculated f r o m the f o r m u l a : pre-op score -- post-op score x 100 pre-op score + post-op score 1
Animals
Pre-op
Post-op retention
Savings
T1 T2 T3 T4
240 300 400 200
0 0 0 130
÷100 + 100 + 100 + 21.2
P1 P2 P3 P4 P5
220 380 140 90 100
20 10 0 0 0
C1 C2
200 120
0 0
+ 100 + 100
U1 U2 U3 U4 U5 U6 U7
220 230 210 240 300 320 290
0 0 0 0 0 -
+100 ÷ 100 +100 + 100 + 100
+ + + + +
83.3 94.9 100 100 100
Groupmean savings
+ 80.3
+ 95.6
+100
+ 100
228 TABLE I11 INTERMANUALTRANSFERON AN EASYTACTILESHAPEDISCRIMINATIONTASK (switch vs. knob, stage II1 of training) Figures in the 'lst Hand' column represent trials to reach a level of performance of 10 correct responses in 11 consecutive trials. After reaching this level all animals were given 400 trials of overtraining before changing to the second hand. Figures in the '2nd Hand' column represent trials to reach a level of performance of 45 correct responses in 50 consecutive trials. Figures for 'Savings' have been calculated from the formula:
1st hand score -- 2nd hand score × 100 -• 1st hand score + 2nd hand score 1
Animals
1st Hand
2nd Hand
Savings
Group mean savings
T1 T2 T3 T4 T5 T6 T7
107 36 95 54 13 13 221
80 60 70 70 100 100 180
+ 14.4 -- 25 ~- 15.15 -- 12.9 -- 77 --- 77 + 10.2
--
P1 P2 P3 P4 P5
2 2 79 0 24
70 0 0 20 0
-
C1 C2
0 12
70 70
--100 -- 70.7
U1 U2 U3 U4 U5 U6 U7
41 96 102 23 198 144 84
0 0 0 0 0 0 0
94.4 t 100 -k 100 -- 100 q- 100
+100 +100 +100 +100 +100 +100 + 100
21.7
+ 21.1
-
85.35
+100
t i o n o n this t a s k (stage II), t h e a n i m a l s w e r e a d a p t e d to t h e h a n d r e s t r a i n t u s i n g a n 'adapting' task
c o n e a n d p y r a m i d . W h e n the r e s t r a i n t was s u b s e q u e n t l y c h a n g e d
f r o m o n e h a n d to t h e o t h e r in s u c c e e d i n g tasks t h e a n i m a l s w e r e a l w a y s first r e t r a i n e d to a c r i t e r i o n o f 45 c o r r e c t r e s p o n s e s in 50 trials w i t h c o n e a n d p y r a m i d in o r d e r to r e a d a p t t h e f o r m e r l y r e s t r a i n e d h a n d to the d i s c r i m i n a t i o n p r o c e d u r e 11. S t a g e I I I , s w i t c h a n d k n o b , was a n ' e a s y - o v e r t r a i n e d ' task. A n i m a l s w e r e tested w i t h t h e i r first h a n d to a c r i t e r i o n o f 10 c o r r e c t r e s p o n s e s in 11 trials a n d w e r e t h e n g i v e n 400 f u r t h e r trials b e f o r e t h e r e s t r a i n t was c h a n g e d a n d t h e o t h e r h a n d tested to a c r i t e r i o n o f 45 c o r r e c t r e s p o n s e s in 50 trials - - the s e c o n d h a n d score. S t a g e IV, C a n d D, was a ' d i t t i c u l t - u n d e r t r a i n e d ' task. T h e a n i m a l s w e r e t r a i n e d o n this m i r r o r i m a g e d i s c r i m i n a t i o n to a c r i t e r i o n o f 10 c o r r e c t r e s p o n s e s in 11 trials. T h e h a n d b e i n g r e s t r a i n e d was then changed and the other hand trained on the mirror image discrimination D and C a to a c r i t e r i o n o f 45 c o r r e c t r e s p o n s e s in 50 trials. S t a g e V, disc a n d h e x a g o n , was
229 TABLE IV 1NTERMANUAL TRANSFER ON A DIFFICULT TACTILE SHAPE DISCRIMINATION TASK
(C vs. D, stage IV of training) F indicates that the animal failed to learn within the stated number of trials, indicates that the second hand was not tested. All other figures and symbols are as in the previous table, but there was no overtraining of the first hand. Animals"
1st Hand
2nd Hand
Savings
TI T2 T3 T4 T5 T6 T7
721 448 308 830 439 112 1200F
710 340 230 1000 530 370 -
+ 0.8 + 13.7 + 14.5 -- 9.3 -- 9.4 -- 53.5
Pl P2 P3 P4 P5
179 436 479 174 220
190 660 590 3O 140
-- 3.0 -- 20.4 10.4 + 70.6 + 22.2
Cl C2
634 465
1000F 590
U1 U2 U3 U4 U5 U6 U7
508 459 779 60 940 1200F 173
40 0 50 30 100 0
--
< -- 22.4 11.8
Group mean savings
--
7 . 2
+11.8
< --17.1
--
÷ 85.4 ÷100 ÷ 87.9 ÷ 33.3 + 80.8
+81.2
+ 100
a 'difficult-overtrained' task. T h e animals were trained on this d i s c r i m i n a t i o n to a criterion o f 10 correct responses in 11 trials an d were then given a further 400 trials o f o v e r t r a i n i n g before the restraint was c h an g ed an d the other h a n d was trained to a criterion o f 45 correct responses in 50 trials. Stage VI, r o u g h vs. s m o o t h , was an 'easyu n d e r t r a i n e d ' task. T h e a n i m a l s were trained on this task to a criterion o f 10 correct responses in 1 1 trials, the restraint was then ch an g ed and the other h a n d was trained to a criterion o f 45 correct responses in 50 trials. Stage V I I consisted o f a series o f d i scr i m i n at i o n s o f the relative roughness of sandpapers. T h e series and the m e t h o d o f p r e s e n t a t i o n (i.e. threshold testing) was the same as used p r e v i o u s l y n . A f te r 12 descending and 12 ascending thresholds h ad been d e t e r m i n e d for the first hand, the restraint was ch an g ed to the other h a n d and 6 ascen d i n g and 6 descending thresholds were then d e t e r m i n e d for the second hand. Th e first level o f d i s c r i m i n a t i o n presented to the second h a n d was that o f s a n d p a p e r grade 320 particles per linear inch against x, where x equals one step in the series coarser t h a n the m e d i a n o f the final 4 ascending and 3 descending thresholds o f the first hand.
230 TABLE V INTERMANUAL
TRANSFER ON A DIFFICULT TACTILE SHAPE DISCRIMINATION TASK
(disc vs. hexagon, stage V of training) Figures and symbols as in previous tables. First hand overtrained. Animals
1st Hand
2nd Hand
Savings
TI T2 T3 T4 T5 T6 T7
172 163 132 1200F 129 585 387
360 - (died) 360 190 910 30
35.5
-- 19.1 21.7 + 85.6
P1 P2 P3 P4 P5
49 243 90 215 771
150 170 70 0 100
-- 50.75 17.7 t2.5 + 100 + 77
CI C2
451 123
180 130
42.9 2.8
U1 U2 U3 U4 U5 U6 U7
1200F 203 216 598 1082 723 78
0 0 30 0 0 0
+ 100 ~-100 ~- 90.4 +100 + 100 + 100
Group mean savings
46.3 --
7.4
+31.3
+20.05
+98.4
( I n t e r a c t i o n between stages VI a n d VII is n o t a p p a r e n t either for the u n o p e r a t e d a n i m a l s which s h o w e d positive i n t e r m a n u a l t r a n s f e r o r f o r the o p e r a t e d g r o u p s which d i d n o t initially p e r f o r m b e l o w chance with the second h a n d o f stage VII). Stage V I I I consisted o f a series o f d i s c r i m i n a t i o n s o f the relative d i a m e t e r o f s m o o t h metal cylinders. T h e series is described in S e m m e s a n d M i s h k i n 14. T h e p r e s e n t a t i o n o f the series was the s a m e as for stage VII. Stage I X , s h o r t c y l i n d e r (1.6 c m high z 3.1 c m d i a m . ) a n d t a l l cylinder (5.0 c m high z 3.1 c m d i a m . ) , was a n ' e a s y - u n d e r t r a i n e d ' task. A n i m a l s were t r a i n e d to a c r i t e r i o n o f 10 correct responses in 10 trials. The h a n d r e s t r a i n t was then c h a n g e d a n d the o t h e r h a n d t r a i n e d to a criterion o f 45 correct responses in 50 trials. S t a g e X, I kg weight a n d 0.5 kg weight, was a 'difficult-overtrained' task. A n i m a l s were t r a i n e d to a c r i t e r i o n o f 10 correct responses in 10 trials a n d were then given a further 400 overt r a i n i n g trials before t h e h a n d r e s t r a i n t was c h a n g e d a n d the o t h e r h a n d t r a i n e d to a criterion o f 45 correct responses in 50 trials. Stage X I , long o b l o n g (5.0 c m l o n g × 1.0 c m wide × 2.0 c m high) a n d s h o r t o b l o n g (2.5 c m long x 1.0 cm wide × 2.0 cm high), was a n ' e a s y - u n d e r t r a i n e d ' task. A n i m a l s were t r a i n e d to a criterion o f t 0 c o r r e c t responses in 10 trials. T h e h a n d restraint was then c h a n g e d a n d the o t h e r h a n d t r a i n e d to a c r i t e r i o n o f 45 correct responses in 50 trials.
231 T A B L E VI 1NTERMANUAL TRANSFER ON AN EASY TACTILE TEXTURE DISCRIMINATIONTASK (rough vs. smooth, stage VI of training)
Figures and symbols as in previous tables. There was no overtraining of the first hand.
Animals
1st Hand
2nd Hand
Savings
TI T3 T4 T5 T6 T7
165 23 37 196 121 90
70 20 340 180 140 60
+ 40.4 + 7.0 -- 80.4 + 4.25 -- 7.3 + 20
P1 P2 P3 P4 P5
6 36 81 81 52
10 0 10 0 0
-- 25 ÷ 100 + 78 + 100 + 100
C1 C2
4 57
110 0
-- 93 + 100
U1 U2 U3 U4 U5 U6 U7
80 43 27 89 73 200 503
0 0 0 0 0 0 0
+100 + 100 %-100 +100 +100 ÷ 100 + 100
G r o u p m e a n savings
--
2.7
-t- 70.6
3.5
+ 100
The hand preferences of the animals were recorded during the training of stages I and I l and were balanced within groups in the subsequent transfer training. A period of 4 weeks elapsed between stages I and lI in order to allow for postoperative recovery. The order of task presentation was balanced within groups for stages III-VI. The tasks were presented either in the order III, IV, V and VI, or in the order VI, V, IV and Ill. Stages VII, VIII, IX, X and Xl were presented to all animals in that order. Animals were routinely trained for 40 trials per day, and all discrimination training followed the pseudo-random schedule of Gellermann ,~. Comparisons were systematically monitored with an infra-red telescope or an electronic touch sensing device. RESULTS
(1) The preoperative learning scores on the easy tactile shape discrimination task, cylinder and sphere, are shown in Table II. Comparison of these scores by t-test shows a significant inferiority of the unoperated control group relative to the control splits group at the 0.05 level, but no other significant differences. Postoperative retention scores are also shown in Table II. Only 3 animals failed to show complete reten-
232 TABLE VII INTERMANUALTRANSFERON PARAMETRICDISCRIMINATIONTASKOF ROUGHNESS (stage VII of training) Figures in the 'lst Hand' column represent the mean of the last 4 ascending thresholds and the last 4 descending thresholds of the first hand, as shown in the graphs of raw data. Figures in the '2nd Hand' column represent the mean of the first 4 ascending thresholds and the first 4 descending thresholds of the second hand, as shown in the graphs of raw data. Figures for 'Savings' have been calculated as in previous tables, but here savings are not distributed between + 100 and --100 as in the standard savings index (see text). An#nab
lstHand
TI T3 T4 T6 T7
161.25 257.5 115 97.5 155
P1 P2 P3 P4
2ndHand
Savings
Groupmean savings
41.25 88.75 57.5 40 70
--59.3 --48.7 33.3 --41.8 --37.7
-44.2
200 135 250 161.25
80 96.25 170 117.5
-42.9 -16.8 -19.05 -15.7
C1 C2
183.75 191.25
83.75 71.25
-37.4 -45.7
U1 U4 U5 U7
202.5 157.5 120 165
197.5 153.75 61.25 143.75
-- 1.25 -- 1.2 -- 32.4 -- 6.9
-23.6
--41.55
--10.4
tion. A n i m a l s T 5 - T 7 a r e n o t i n c l u d e d because they h a d p r e v i o u s l y experienced postsurgical t r a i n i n g in a n o t h e r e x p e r i m e n t (to be p u b l i s h e d ) . (2) T h e scores for the first 4 d i s c r i m i n a t i o n learning tasks are in T a b l e s I I I , IV, V a n d VI, a n d s h o w two m a i n effects. Firstly, the t o t a l splits, a n d c o n t r o l splits consistently s h o w less savings t h a n the p a r t i a l splits a n d the u n o p e r a t e d controls. Secondly, the p a r t i a l splits consistently show less savings t h a n the u n o p e r a t e d controls. I n o r d e r to facilitate a n analysis o f variance t h e a n i m a l s with i n c o m p l e t e sets o f d a t a were excluded (i.e. a n i m a l s T2, T4, T7, U1 a n d U6). A n i m a l s C1 a n d C2 have also been e x c l u d e d because a g r o u p o f o n l y two subjects m a y p r o v i d e u n s t a b l e results. T h e t o t a l g r o u p shows significantly less savings t h a n the p a r t i a l g r o u p on the 4 tasks c o m b i n e d ( P < 0.0009). T h e p a r t i a l g r o u p shows significantly less savings t h a n the u n o p e r a t e d g r o u p o n these tasks (P < 0.0077). C o m p a r i n g the 4 tasks, there is a significant difference in savings ( P < 0.0004). T h e source o f this between tasks difference derives largely f r o m the relatively greater savings shown b y all a n i m a l s in the texture d i s c r i m i n a t i o n t a s k (stage VI o f training). N o interactions were significant except for a g r o u p s - t a s k i n t e r a c t i o n ( P < 0.0093), where the significance derives f r o m a ceiling effect o n the savings o f the u n o p e r a t e d group. T h e effect o f t a s k difficulty was
233
TABLE
VIll
INTERMANUAL
TRANSFER ON PARAMETRIC
DISCRIMINATION
TASK OF SIZE
(stage VIII of training) Figures and symbols as in Table V I I . Animals
1st Hand
2nd Hand
Savings
Group mean savings
T1 T3 T4 T6 T7
1.39 1.37 1.6 1.45 1.5
1.65 2.46 2.32 2.42 2.09
-- 8.55 --28.5 18.2 25.1 - 16.4
- 19.35
Pl P2 P3 P4
1.33 1.35 1.33 1.37
1.81 1.57 1.41 1.36
15.3 - 7.5 - 2.9 -' 0.4
c1 c2
1.32 1.33
1.71 1.76
12.9 - 13.9
U4 U7
1.38 1.57
1.45 1.75
-
2.5 5.4
8.4
-13.4
3.95
RCX.iGHNESS
40 q
3.81
5O
2.96
I,
6O e0
2.40 2.02
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© Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
I N T E R M A N U A L T R A N S F E R IN T H E M O N K E Y A M O U N T OF C A L L O S A L S P A R I N G
AS A F U N C T I O N
OF
M. HUNTER, G. E T T L I N G E R AND J. J. MACCABE
Institute of Psychiatry, De Crespigny Park, London SE5 8AF (Great Britain) (Accepted February 19th, 1975)
SUMMARY
The effects of commissure section, task difficulty and overtraining on the intermanual transfer of tactile learning have been examined. Twenty-one rhesus monkeys were allocated to 4 groups. One group was subjected to complete transection of the corpus callosum, massa intermedia and posterior commissure. Some of this group also sustained a cerebellar section. A second group received a similar division of the commissures but with part of the posterior body of the corpus callosum left intact. A third group received similar division of the commissures but with the posterior commissure left intact. The fourth group formed an unoperated control group. Animals with only the posterior commissure left intact showed little or no transfer. Animals with partial callosal lesions showed significantly greater transfer than animals with total transections, but were impaired relative to the unoperated controls. Estimates have been made of the number of callosal fibres left intact in the animals with partial callosal lesions. These estimates have been correlated with transfer. The correlation was significant on only one task. Neither task difficulty nor overtraining were found to affect transfer significantly. The comparison of transfer of the submodalities of size and roughness was inconclusive.
INTRODUCTION
Recent anatomical investigations8,13 have found that there are no direct interhemispheric connections between areas of SI which represent the distal parts of the limbs - - the hand and foot areas. This suggests that the forebrain commissures, in transferring learned patterns of behaviour from one hemisphere to the other, are not transferring at the level of the primary sensory areas. The interhemispheric projections of parietal cortex have been studied in detaiP 3, but up to now no detailed attempt has
224
been made to clarify the relationship between these projections and the transler of tactile learning. The evidence in the literature concerning the intermanual transfer of tactile learning is conflicting. Some investigators 2,1° have concluded that sectioning of the corpus callosum (CC) completely arrests interhemispheric transfer, while others '~,~,11, 15 have found variable amounts of transfer. The explanation for these inconsistent results may lie in the parameters affecting the behavioural training. It has been suggested 15 that the difficulty of the learning task may influence the amount of transfer, and in a recent study u it was suggested that both task difficulty and amount of overtraining may have an effect. The present experiment is an attempt to correlate interhemispheric transfer of tactile learning with specific numbers of fibres of the posterior body of the CC. Further, it is designed to analyze the possible roles of task difficulty and amount of overtraining in intermanual transfer. Finally, it is designed to investigate the possible involvement of the posterior commissurO 1 in the transfer of tactile learning. METHODS
Twenty-one rhesus monkeys were the subjects in this experiment. The 21 animals were divided into 4 groups. Animals T1-T4 (total splits) were intended to have a complete division of the CC, of the posterior commissure (PC) and the massa intermedia (MI); animals T5-T7 were intended to have similar lesions and in addition a midline sagittal section along the vermis of the cerebellum; animals PI-P5 (partial splits) were intended to have a complete division of the PC and the MI but incomplete division of the CC, leaving a 2-3 mm band of fibres intact in the posterior third ofthe body of the CC; C 1-C2 (control splits with PC intact) were intended to have complete division of the CC and of the MI; and U1-U7 formed an unoperated controI group. (It was considered possible that the additional transection of the cerebellum in the total splits T5-T7 would affect transfer. However, this was not found, Therefore their results have been combined with those of animals Tl-T4.)
Operations All the surgical operations were carried out in aseptic conditions. After a large bilateral cranial bone flap had been raised the dura mater was incised on the left side and widely reflected back to the sagittal sinus. The transections were then made by aspirating with a small-gauge sucker under direct vision, with the aid of a binocular microscope. For animals T5-T7 the midtine bisection of the cerebellum was carried out at a second operation 16, 3 and I0 months respectively after the sections of the CC, PC and MI. The cerebellum was approached through an opening made with rongeurs in the occipital bone. The section along the midline extended ventrally through the vermis to the medulla, dividing the cerebellar cortex and separating the cerebellar nuclei. Again the section was carried out under direct vision. Following surgery 4 animals (T1, T2, P4 and P5) suffered from a mild transient right hemiparesis and one animal (T4) from a permanent right herniparesis. Also 3
225 a n i m a l s (T3, T4 a n d P5) suffered i n t e r m i t t e n t right-sided focal epileptic seizures for s h o r t p e r i o d s o f time, usually less t h a n one day. T h e recovery o f all other a n i m a l s was either uneventful, or, as in the case o f the a n i m a l s with total splits plus a cerebellar transection, h a d been c o m p l e t e d some m o n t h s before the b e h a v i o u r a l testing o f this e x p e r i m e n t began. Histological procedures and findings
F o r a n i m a l s T l, T3 a n d T5, c o r o n a l sections were t a k e n at a thickness o f 25/~m and every twentieth section was stained with the fibre stain a n d cell counter-stain o f Klfiver a n d B a r r e r a 9. F o r a n i m a l s P1-P5, C1 a n d 2, a n d U 4 the b r a i n was divided sagittally a l o n g the midline. The left side o f the b r a i n was t a k e n in P I - 5 , C2 a n d U4, a n d the right side in C I a n d then these b r a i n halves were c o r o n a l l y sectioned and stained with the K l f i v e r - B a r r e r a m e t h o d . The o t h e r brain halves had smaller blocks cut f r o m them. The blocks o f P1-5 included the p o s t e r i o r p a r t o f the CC, the blocks o f C 1 - 2 included the PC, a n d the b l o c k o f U 4 included the whole o f the C C a n d PC. These blocks were sectioned sagittally at a thickness o f 10/tin a n d were stained with either a G l e e s - M a r s l a n d 12 stain (P2), a G r o s s - B i e l s c h o w s k y stain (C1), or a Hfiggqvist 7 stain (P1, 3, 4 a n d 5; C1 a n d 2; a n d U4). The lesions o f T 2 a n d 4 were confirmed by gross analysis at p o s t - m o r t e m b r a i n cut. The b r a i n s o f a n i m a l s T6 a n d 7 are still to be processed. The fibres left intact in the C C o f the p a r t i a l splits a n d in U4 a n d the fibres of the P C in the c o n t r o l splits a n d U 4 were counted, using a m e t h o d based on that of De M y e r 1. R a n d o m samples o f the a r e a left intact were p h o t o g r a p h e d at × 500 magnification. The n u m b e r o f intact fibres was c o u n t e d f r o m the p h o t o m i c r o g r a p h s . The total a r e a o f intact fibres was estimated. A n estimate o f the total n u m b e r o f intact fibres was derived f r o m these values. TABLE I E S T I M A T E S O F T O T A L N U M B E R S OF I N T A C T F I B R E S
All brains were studied with H/iggqvist stain 7 except where shown otherwise. Animal
Estimate of total area of intact fibres
Mean fibre count from n samples of 0.0324 sq. mm and ranges
Estimate of total number of intact fibres
PI P2 (Glees-Marsland) P3 P4 P5 C1 (Hfiggqvist stain) C1 (Gross-Bielschowsky) C2 U4 U4
0.162 sq. rnm of CC 2.137 sq. mm of CC
453 (n = 2) (486/420) 1,227 (n -- 4) (1320/1124)
2,265 80,946
0.798 sq. 3.915 sq. 1.457 sq. 0.948 sq.
of CC of CC of CC of PC
464 (n -- 4) (638/314) 496 (n -- 4) (525/440) 1,042 (n = 4) (1148/940) 707 (n 4) (816/575)
11,428 59,901 46,869 20,687
0.971 sq. mm of PC
742 (n = 4) (830/667)
22,253
mm mm mm mm
1.999 sq. mm of PC 578 (n = 4) (602/568) in posterior body of CC 1,350 (n -- 4) (1494/1104) 0.965 sq. mm of PC 1,013 (n = 4) (1079/968)
35,657 41,667 fibres/sq, mm 30,182
226 P2
P1
P3
P4
P5
Fig. 1. Diagrammatic representation of the position in the corpus callosum of the anterior and posterior boundaries of the spared segment (black), reconstructed from the cross-sectionS with reference to the posterior limits of the splenium.
The coronal sections confirmed the intended lesions with 2 exceptions. Firstly, in P3 a few fibres anteriorly in the genu of the CC were left intact, and a small area of the dorsal MI appears to be uncut. Secondly, in T3 a few fibres at the posterior end of the PC have been spared. The mid-sagittal division of those brains, for which sagittal as well as coronal sections were taken, occasionally resulted in parts of the lesions being included in the sagittal blocks. Consequently, not all the lesions appeared in the coronal slides. This occurred in PI and 3 and C2. However, the intended lesions were confirmed in all slides in which they were visible. In addition to the intended lesions the anterior commissure was cut in all animals, although not completely cut in P2; the habenular commissure was cut in TI and 3, and in P5; the anterior part of the commissure of the superior colliculus was cut in T1 and P5. the lateral ventricles were abnormally dilated in T3. P1. P2, P3, P4, P5 and C2; there was a small stab wound in the hypothalamic area m T3; a little damage to the hypothalamus in P4 and 5 and to the pineal body of P5. The gross analysis at post-mortem brain cut o f T 2 and T4 confirmed the intended lesions and in addition showed section of the anterior commissure and abnormal dilatation of the lateral ventricles. The counts of intact fibres made from the sagittal sections are shown in Table I : the position of the intact fibres of the partial animals in Fig. 1.
Behavioural testing All behavioural training was carried out in the dark in a Wisconsin General Testing Apparatus (WGTA). In order that the animals would only use one hand at a time for the discrimination tasks the other hand was restrained by attaching a weighted rubber ball to the wrist by means of a bracelet. The test objects used (see Figl 2) were chosen to provide a range of difficulty, based on learning scores in previous experiments, and to compare different sub-modalities within the somatic sense modality. Different degrees of overtraining were also used. Stage I of training, cylinder and sphere, was a preliminary preoperative task (see Table II). After postoperative reten-
227
i _J Fig. 2. T h e pairs of test objects used in behavioural training. Choice of the object to the left o f each pair was rewarded (except d u r i n g training o f the second h a n d o n C a n d D, see text). T A B L E 11 P R E - A N D P O S T - O P E R A T I V E P E R F O R M A N C E O N A N EASY T A C T I L E S H A P E D I S C R I M I N A T I O N TASK.
(cylinder vs. sphere, stages I a n d 1! of training) Figures for pre-op a n d post-op retention represent trials to reach a level of p e r f o r m a n c e o f 180 correct responses in 200 consecutive trials. Figures for 'savings' have been calculated f r o m the f o r m u l a : pre-op score -- post-op score x 100 pre-op score + post-op score 1
Animals
Pre-op
Post-op retention
Savings
T1 T2 T3 T4
240 300 400 200
0 0 0 130
÷100 + 100 + 100 + 21.2
P1 P2 P3 P4 P5
220 380 140 90 100
20 10 0 0 0
C1 C2
200 120
0 0
+ 100 + 100
U1 U2 U3 U4 U5 U6 U7
220 230 210 240 300 320 290
0 0 0 0 0 -
+100 ÷ 100 +100 + 100 + 100
+ + + + +
83.3 94.9 100 100 100
Groupmean savings
+ 80.3
+ 95.6
+100
+ 100
228 TABLE I11 INTERMANUALTRANSFERON AN EASYTACTILESHAPEDISCRIMINATIONTASK (switch vs. knob, stage II1 of training) Figures in the 'lst Hand' column represent trials to reach a level of performance of 10 correct responses in 11 consecutive trials. After reaching this level all animals were given 400 trials of overtraining before changing to the second hand. Figures in the '2nd Hand' column represent trials to reach a level of performance of 45 correct responses in 50 consecutive trials. Figures for 'Savings' have been calculated from the formula:
1st hand score -- 2nd hand score × 100 -• 1st hand score + 2nd hand score 1
Animals
1st Hand
2nd Hand
Savings
Group mean savings
T1 T2 T3 T4 T5 T6 T7
107 36 95 54 13 13 221
80 60 70 70 100 100 180
+ 14.4 -- 25 ~- 15.15 -- 12.9 -- 77 --- 77 + 10.2
--
P1 P2 P3 P4 P5
2 2 79 0 24
70 0 0 20 0
-
C1 C2
0 12
70 70
--100 -- 70.7
U1 U2 U3 U4 U5 U6 U7
41 96 102 23 198 144 84
0 0 0 0 0 0 0
94.4 t 100 -k 100 -- 100 q- 100
+100 +100 +100 +100 +100 +100 + 100
21.7
+ 21.1
-
85.35
+100
t i o n o n this t a s k (stage II), t h e a n i m a l s w e r e a d a p t e d to t h e h a n d r e s t r a i n t u s i n g a n 'adapting' task
c o n e a n d p y r a m i d . W h e n the r e s t r a i n t was s u b s e q u e n t l y c h a n g e d
f r o m o n e h a n d to t h e o t h e r in s u c c e e d i n g tasks t h e a n i m a l s w e r e a l w a y s first r e t r a i n e d to a c r i t e r i o n o f 45 c o r r e c t r e s p o n s e s in 50 trials w i t h c o n e a n d p y r a m i d in o r d e r to r e a d a p t t h e f o r m e r l y r e s t r a i n e d h a n d to the d i s c r i m i n a t i o n p r o c e d u r e 11. S t a g e I I I , s w i t c h a n d k n o b , was a n ' e a s y - o v e r t r a i n e d ' task. A n i m a l s w e r e tested w i t h t h e i r first h a n d to a c r i t e r i o n o f 10 c o r r e c t r e s p o n s e s in 11 trials a n d w e r e t h e n g i v e n 400 f u r t h e r trials b e f o r e t h e r e s t r a i n t was c h a n g e d a n d t h e o t h e r h a n d tested to a c r i t e r i o n o f 45 c o r r e c t r e s p o n s e s in 50 trials - - the s e c o n d h a n d score. S t a g e IV, C a n d D, was a ' d i t t i c u l t - u n d e r t r a i n e d ' task. T h e a n i m a l s w e r e t r a i n e d o n this m i r r o r i m a g e d i s c r i m i n a t i o n to a c r i t e r i o n o f 10 c o r r e c t r e s p o n s e s in 11 trials. T h e h a n d b e i n g r e s t r a i n e d was then changed and the other hand trained on the mirror image discrimination D and C a to a c r i t e r i o n o f 45 c o r r e c t r e s p o n s e s in 50 trials. S t a g e V, disc a n d h e x a g o n , was
229 TABLE IV 1NTERMANUAL TRANSFER ON A DIFFICULT TACTILE SHAPE DISCRIMINATION TASK
(C vs. D, stage IV of training) F indicates that the animal failed to learn within the stated number of trials, indicates that the second hand was not tested. All other figures and symbols are as in the previous table, but there was no overtraining of the first hand. Animals"
1st Hand
2nd Hand
Savings
TI T2 T3 T4 T5 T6 T7
721 448 308 830 439 112 1200F
710 340 230 1000 530 370 -
+ 0.8 + 13.7 + 14.5 -- 9.3 -- 9.4 -- 53.5
Pl P2 P3 P4 P5
179 436 479 174 220
190 660 590 3O 140
-- 3.0 -- 20.4 10.4 + 70.6 + 22.2
Cl C2
634 465
1000F 590
U1 U2 U3 U4 U5 U6 U7
508 459 779 60 940 1200F 173
40 0 50 30 100 0
--
< -- 22.4 11.8
Group mean savings
--
7 . 2
+11.8
< --17.1
--
÷ 85.4 ÷100 ÷ 87.9 ÷ 33.3 + 80.8
+81.2
+ 100
a 'difficult-overtrained' task. T h e animals were trained on this d i s c r i m i n a t i o n to a criterion o f 10 correct responses in 11 trials an d were then given a further 400 trials o f o v e r t r a i n i n g before the restraint was c h an g ed an d the other h a n d was trained to a criterion o f 45 correct responses in 50 trials. Stage VI, r o u g h vs. s m o o t h , was an 'easyu n d e r t r a i n e d ' task. T h e a n i m a l s were trained on this task to a criterion o f 10 correct responses in 1 1 trials, the restraint was then ch an g ed and the other h a n d was trained to a criterion o f 45 correct responses in 50 trials. Stage V I I consisted o f a series o f d i scr i m i n at i o n s o f the relative roughness of sandpapers. T h e series and the m e t h o d o f p r e s e n t a t i o n (i.e. threshold testing) was the same as used p r e v i o u s l y n . A f te r 12 descending and 12 ascending thresholds h ad been d e t e r m i n e d for the first hand, the restraint was ch an g ed to the other h a n d and 6 ascen d i n g and 6 descending thresholds were then d e t e r m i n e d for the second hand. Th e first level o f d i s c r i m i n a t i o n presented to the second h a n d was that o f s a n d p a p e r grade 320 particles per linear inch against x, where x equals one step in the series coarser t h a n the m e d i a n o f the final 4 ascending and 3 descending thresholds o f the first hand.
230 TABLE V INTERMANUAL
TRANSFER ON A DIFFICULT TACTILE SHAPE DISCRIMINATION TASK
(disc vs. hexagon, stage V of training) Figures and symbols as in previous tables. First hand overtrained. Animals
1st Hand
2nd Hand
Savings
TI T2 T3 T4 T5 T6 T7
172 163 132 1200F 129 585 387
360 - (died) 360 190 910 30
35.5
-- 19.1 21.7 + 85.6
P1 P2 P3 P4 P5
49 243 90 215 771
150 170 70 0 100
-- 50.75 17.7 t2.5 + 100 + 77
CI C2
451 123
180 130
42.9 2.8
U1 U2 U3 U4 U5 U6 U7
1200F 203 216 598 1082 723 78
0 0 30 0 0 0
+ 100 ~-100 ~- 90.4 +100 + 100 + 100
Group mean savings
46.3 --
7.4
+31.3
+20.05
+98.4
( I n t e r a c t i o n between stages VI a n d VII is n o t a p p a r e n t either for the u n o p e r a t e d a n i m a l s which s h o w e d positive i n t e r m a n u a l t r a n s f e r o r f o r the o p e r a t e d g r o u p s which d i d n o t initially p e r f o r m b e l o w chance with the second h a n d o f stage VII). Stage V I I I consisted o f a series o f d i s c r i m i n a t i o n s o f the relative d i a m e t e r o f s m o o t h metal cylinders. T h e series is described in S e m m e s a n d M i s h k i n 14. T h e p r e s e n t a t i o n o f the series was the s a m e as for stage VII. Stage I X , s h o r t c y l i n d e r (1.6 c m high z 3.1 c m d i a m . ) a n d t a l l cylinder (5.0 c m high z 3.1 c m d i a m . ) , was a n ' e a s y - u n d e r t r a i n e d ' task. A n i m a l s were t r a i n e d to a c r i t e r i o n o f 10 correct responses in 10 trials. The h a n d r e s t r a i n t was then c h a n g e d a n d the o t h e r h a n d t r a i n e d to a criterion o f 45 correct responses in 50 trials. S t a g e X, I kg weight a n d 0.5 kg weight, was a 'difficult-overtrained' task. A n i m a l s were t r a i n e d to a c r i t e r i o n o f 10 correct responses in 10 trials a n d were then given a further 400 overt r a i n i n g trials before t h e h a n d r e s t r a i n t was c h a n g e d a n d the o t h e r h a n d t r a i n e d to a criterion o f 45 correct responses in 50 trials. Stage X I , long o b l o n g (5.0 c m l o n g × 1.0 c m wide × 2.0 c m high) a n d s h o r t o b l o n g (2.5 c m long x 1.0 cm wide × 2.0 cm high), was a n ' e a s y - u n d e r t r a i n e d ' task. A n i m a l s were t r a i n e d to a criterion o f t 0 c o r r e c t responses in 10 trials. T h e h a n d restraint was then c h a n g e d a n d the o t h e r h a n d t r a i n e d to a c r i t e r i o n o f 45 correct responses in 50 trials.
231 T A B L E VI 1NTERMANUAL TRANSFER ON AN EASY TACTILE TEXTURE DISCRIMINATIONTASK (rough vs. smooth, stage VI of training)
Figures and symbols as in previous tables. There was no overtraining of the first hand.
Animals
1st Hand
2nd Hand
Savings
TI T3 T4 T5 T6 T7
165 23 37 196 121 90
70 20 340 180 140 60
+ 40.4 + 7.0 -- 80.4 + 4.25 -- 7.3 + 20
P1 P2 P3 P4 P5
6 36 81 81 52
10 0 10 0 0
-- 25 ÷ 100 + 78 + 100 + 100
C1 C2
4 57
110 0
-- 93 + 100
U1 U2 U3 U4 U5 U6 U7
80 43 27 89 73 200 503
0 0 0 0 0 0 0
+100 + 100 %-100 +100 +100 ÷ 100 + 100
G r o u p m e a n savings
--
2.7
-t- 70.6
3.5
+ 100
The hand preferences of the animals were recorded during the training of stages I and I l and were balanced within groups in the subsequent transfer training. A period of 4 weeks elapsed between stages I and lI in order to allow for postoperative recovery. The order of task presentation was balanced within groups for stages III-VI. The tasks were presented either in the order III, IV, V and VI, or in the order VI, V, IV and Ill. Stages VII, VIII, IX, X and Xl were presented to all animals in that order. Animals were routinely trained for 40 trials per day, and all discrimination training followed the pseudo-random schedule of Gellermann ,~. Comparisons were systematically monitored with an infra-red telescope or an electronic touch sensing device. RESULTS
(1) The preoperative learning scores on the easy tactile shape discrimination task, cylinder and sphere, are shown in Table II. Comparison of these scores by t-test shows a significant inferiority of the unoperated control group relative to the control splits group at the 0.05 level, but no other significant differences. Postoperative retention scores are also shown in Table II. Only 3 animals failed to show complete reten-
232 TABLE VII INTERMANUALTRANSFERON PARAMETRICDISCRIMINATIONTASKOF ROUGHNESS (stage VII of training) Figures in the 'lst Hand' column represent the mean of the last 4 ascending thresholds and the last 4 descending thresholds of the first hand, as shown in the graphs of raw data. Figures in the '2nd Hand' column represent the mean of the first 4 ascending thresholds and the first 4 descending thresholds of the second hand, as shown in the graphs of raw data. Figures for 'Savings' have been calculated as in previous tables, but here savings are not distributed between + 100 and --100 as in the standard savings index (see text). An#nab
lstHand
TI T3 T4 T6 T7
161.25 257.5 115 97.5 155
P1 P2 P3 P4
2ndHand
Savings
Groupmean savings
41.25 88.75 57.5 40 70
--59.3 --48.7 33.3 --41.8 --37.7
-44.2
200 135 250 161.25
80 96.25 170 117.5
-42.9 -16.8 -19.05 -15.7
C1 C2
183.75 191.25
83.75 71.25
-37.4 -45.7
U1 U4 U5 U7
202.5 157.5 120 165
197.5 153.75 61.25 143.75
-- 1.25 -- 1.2 -- 32.4 -- 6.9
-23.6
--41.55
--10.4
tion. A n i m a l s T 5 - T 7 a r e n o t i n c l u d e d because they h a d p r e v i o u s l y experienced postsurgical t r a i n i n g in a n o t h e r e x p e r i m e n t (to be p u b l i s h e d ) . (2) T h e scores for the first 4 d i s c r i m i n a t i o n learning tasks are in T a b l e s I I I , IV, V a n d VI, a n d s h o w two m a i n effects. Firstly, the t o t a l splits, a n d c o n t r o l splits consistently s h o w less savings t h a n the p a r t i a l splits a n d the u n o p e r a t e d controls. Secondly, the p a r t i a l splits consistently show less savings t h a n the u n o p e r a t e d controls. I n o r d e r to facilitate a n analysis o f variance t h e a n i m a l s with i n c o m p l e t e sets o f d a t a were excluded (i.e. a n i m a l s T2, T4, T7, U1 a n d U6). A n i m a l s C1 a n d C2 have also been e x c l u d e d because a g r o u p o f o n l y two subjects m a y p r o v i d e u n s t a b l e results. T h e t o t a l g r o u p shows significantly less savings t h a n the p a r t i a l g r o u p on the 4 tasks c o m b i n e d ( P < 0.0009). T h e p a r t i a l g r o u p shows significantly less savings t h a n the u n o p e r a t e d g r o u p o n these tasks (P < 0.0077). C o m p a r i n g the 4 tasks, there is a significant difference in savings ( P < 0.0004). T h e source o f this between tasks difference derives largely f r o m the relatively greater savings shown b y all a n i m a l s in the texture d i s c r i m i n a t i o n t a s k (stage VI o f training). N o interactions were significant except for a g r o u p s - t a s k i n t e r a c t i o n ( P < 0.0093), where the significance derives f r o m a ceiling effect o n the savings o f the u n o p e r a t e d group. T h e effect o f t a s k difficulty was
233
TABLE
VIll
INTERMANUAL
TRANSFER ON PARAMETRIC
DISCRIMINATION
TASK OF SIZE
(stage VIII of training) Figures and symbols as in Table V I I . Animals
1st Hand
2nd Hand
Savings
Group mean savings
T1 T3 T4 T6 T7
1.39 1.37 1.6 1.45 1.5
1.65 2.46 2.32 2.42 2.09
-- 8.55 --28.5 18.2 25.1 - 16.4
- 19.35
Pl P2 P3 P4
1.33 1.35 1.33 1.37
1.81 1.57 1.41 1.36
15.3 - 7.5 - 2.9 -' 0.4
c1 c2
1.32 1.33
1.71 1.76
12.9 - 13.9
U4 U7
1.38 1.57
1.45 1.75
-
2.5 5.4
8.4
-13.4
3.95
RCX.iGHNESS
40 q
3.81
5O
2.96
I,
6O e0
2.40 2.02
100
1.77
1201
1.60
150
1491
180
1.42 1.37
230 240
1.34
28O
1.31
A D A 2
D A 0 A 3
4 threshclds
D A D A 5
D A D A
6
I 75 ,~ correct
7
8
D A
0 A
D A
D A
9
10
II
12
A DA
DA
2
3
perfor~nce )
DA
DA
DA
4
5
6
th,'edx~s
DA
DA
DA
DA
DA
DA
7
8
9
10
11
12
( 75 ~ coneet
perfonr, ance )
First Hand Second Hand Fig. 3. Performance, shown as ascending and descending thresholds (A and D), on the parametric tasks of roughness and size discrimination. The ordinates are, respectively, number of particles per linear inch and width of cylinders (see text). The arrow signifies the level of difficulty at which the second hand was started. Animal T1.
234 ROUC.HNES$ 40
3.81 I
50
2.96
60
2.40
801
2.02
I00
"1.77
120
1.60
150
1.491
180
1.42
i
I
,,.l,,\//
1.37
220 240
1-34
28O
1,31
DA
DA
I
2
DADA 3
DADA 4
5
DADA 6
7
8
DA
DA
DA
9
10
II
DA 12
A D A D A D4A D A 2 3 5
DA 6
D7A D A 8
DA 9
DA 10
DA II
DA 7
m DA DADADA 9 tO t!
O A 12
threshers { 75 ~ correct ~rforrr~n~ )
First Hand A...
__
__
•
Second Hand
Fig. 4. As for Fig. 3. Animal T6.
3,81 1 2,96
t
2.~o III I 1.77
1.6o
'2
'1
1.49
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I I ~ I| d . -- 4 ~ Q ~
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DADA 3 4
DADA 5 6
DADA 7 8
DA 9
DA 10
DA 11
DA 12
A0A 2
DA 3
First Hand Second Hand Fig. 5. As for Fig. 3. Animal PI.
DA 4
DA 5
DA 6
DA 8
12
235 RCLX~I~SS
40 5O
~ZE 3,81
~
296 2.40
60 8O
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150 180
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22O 340
13.4
280
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DADA 2
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7
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thresholds ( 75 ~ corre~
D A
DA
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I
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DA
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OA
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DA
DA
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9
10
II
12
DA 10
DA 11
DA 12
~rforr~o
]
First Hond A__
__
__~&
Second Hand
Fig. 6. ~%s for Fig. 3. Animal P2.
~NESS
S~ZE
40
3.81
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i\
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~ '-°°1 II \ ^~/' ~ ~ }
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DAOA I
DADA 2
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DADA 4
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DADA 6
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DA 2
DA 3
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