JERZY KONORSKI 129 



ablation of the same area in monkeys produced a total abolition of recent 

 memory of visual stimuli tested by our method in recent experiments by 

 Stfpieii ct ill. 



To sum up, we believe that the inferotemporal area in monkeys contains 

 reverberating chains of neurones connected with the visual projection area 

 and therefore lesions in this area produce the deficit of recent memory 

 observed either directly by using our test, or indirectly by using not very 

 firmly established visual discrimination habits. 



To end this section it is necessary to draw attention to the striking 

 deficits of recent memory found in recent years in humans after hippo- 

 campal lesions (Milner and Penticld, 1955; Scoville and Milner, 1957; and 

 others). Similar results were recently obtained after hippocampal lesions in 

 monkeys by St^pieii et al. with respect to both visual and auditory stimuli. 

 The physiological mechanism of these deficits seems to us so far not clear 

 and they require more detailed investigation. 



SUMMARY 



In this paper the general review of the existing experimental material 

 concerning recent memory in animals is presented and possible mechan- 

 isms of this phenomenon are discussed. 



It has been shown that recent memory is involved in trace CRs (section i ) , 

 in delayed responses (section 2) and in those forms of CRs in w^hich, in 

 order to display a correct response the animal has to compare two succes- 

 sive stimuli (section 3). It has been assumed that the mechanism of recent 

 memory depends on throwing into activity reverberating circuits of 

 neurones, connected with neurones engaged in perception of a given 

 stimulus, and probably situated in the so-called association areas surround- 

 ing the given projection area (section 4). As delayed responses appear to be 

 based on the recent memory of directional cues, it is understandable that 

 they are destroyed after lesions in prefrontal cortex situated in the vicinity 

 of premotor area and caudate nucleus, structures directly concerned with 

 the animal's orientation in space. Similarly acoustic recent memory is 

 destroyed by lesion in gyri sylviaci in dogs and cats and anterior parts of 

 temporal gyri in monkeys; visual recent memory is destroyed after 

 inferotemporal lesions in monkeys (section 5). 



Recent memory plays a prominent role in the consolidation processes of 

 conditioning, since it causes a much more prolonged activation of groups 

 of neurones concerned in a given conditioning than is provided by the 

 actual operation of the corresponding stimuli (section 6). Therefore, the 



