JERZY KONORSKI I25 



space, i.e. in reacting correctly to directional cues and in formation and 

 retention of locomotor CRs. Therefore, it is quite reasonable to believe 

 that the prefrontal area, or rather some yet undehned part of it, is closely 

 functionally connected with these regions supplynig the reverberating 

 circuits responsible for recent memory of those cues which subserve this 

 orientation. 



But It seems that much more precise analysis of the relations between 

 projection areas and adjacent associative areas can be carried out with 

 respect to the recent memory of exteroceptive stimuli on the basis of the 

 test described in section 3. The corresponding experiments were performed 

 by Chonjzyna and L. St^pieh in our laboratory (unpublished). After the 

 dogs were trained to differentiate between pairs of identical tones (SxSx) 

 and different tones (SxS>), the areas situated ventral to the auditory projec- 

 tive area, namely gyrus sylviacus anterior and posterior (Fig. 3), were 

 bilaterally removed. After this operation the dogs lost completely and 

 irreversibly the ability to differentiate such pairs, although not only simple 

 differentiations, but even conditioned inhibition (see footnote on page 6) 

 was fully preserved (Fig. 4). In other words, the animal was able to differ- 

 entiate between the auditory stimulus S — positive CS — and the auditory 

 compound SnS — inhibitory CS — because stimulus So elicited a negative 

 attitudiual reaction which was retained or remembered during the action 

 of S. 



On the other hand ablation of the prefrontal area did not impair the 

 performance of our test.^ This shows that the prefrontal area has probably 

 nothing to do with recent memory of auditory stimuli. It is of interest to 

 note that partial bilateral ablations of the auditory projection area also did 

 not affect this test. 



Similar results were obtained by Goldberg ct al. (1957) in cats. After 

 bilateral removal of ventral parts of the temporal region discrimination 

 between groups of tones which differed only in temporal patterning was 

 lost, although simple tonal discriminations were preserved. 



Even more convincing experiments were recently performed by 

 St(t^pieh ct al. (personal communication). These authors, as mentioned 

 before, used our test for investigating visual and auditory recent memory 

 in monkeys. After the animals were trained to differentiate between 

 pairs of identical and different rhythmical stimuli, both acoustic (clicks) 

 and visual (flashes), different parts of the temporal lobes were bilaterally 



1 After prefrontal ablation the animal was disinhibited for several weeks (Brutkowski et al., 

 1956) and therefore displayed a positive reaction to both excitatory and inhibiting stimuli, 

 but this defect was soon totally compensated. 



