80 K. S. LASHLEY 



p trials = 0.397 ± 0.152 

 p errors = 0.438 ± 0.145 



c. Cases with no invasion of the area critical for pattern 

 vision. In this group are included nos. 50, 53, 55, 58, 59, 62, 

 73, 74, and 75. The average extent of lesion in these cases 

 was 9.6 per cent of the neocortex. In postoperative reten- 

 tion tests the average records were: trials = 22.2, errors = 

 7.3. In this group only two cases, nos. 74 and 75, made 

 records appreciably higher than the records in preoperative 

 retention tests. The lesions in these two cases approach very 

 near to the areas critical for pattern vision and the cases 

 probably should have been included in group h. If these are 

 omitted from the group, the average of the others gives no 

 evidence of loss of the brightness habit.^ 



Comparing the averages for the three groups, we find that 

 lesions in the area striata which do not invade the parts 

 necessary for pattern vision have probably no effect upon 

 the retention of the habit based upon discrimination of light 

 and darkness, that partial destruction of the critical area 

 results in some loss of the habit, and that complete bilateral 

 destruction of the critical area produces a more serious post- 

 operative amnesia. If the sparing or involvement of a criti- 

 cal area for brightness vision were the sole cause of the 

 correlation found previously, the present division of cases 

 should bring about the following results: Cases without 

 involvement of the critical areas should show no amnesia. 

 Cases with partial involvement should divide into two 

 groups, one with complete, the other with no amnesia. Cases 

 with complete destruction of the critical areas should all 

 show equally complete amnesia. 



The results of this analysis conform to such expectations 

 only in the case of group c, with no involvement of the critical 

 areas. In group h, with partial involvement of the critical 

 area, the significance of the data is uncertain. The correla- 

 tion for the series is barely significant (0.40 ±0.15), but, 



*With these two cases omitted, the amount of cerebral destruction in the 

 remaining cases is so small that a proportional deterioration of the habit might 

 escape detection by our rather crude measurements of retention. 



