JERZY KONORSKI I2J 



removed. After ablation of the anterior parts of the first and second 

 temporal gyri the differentiation of the pairs of auditory stimuli was lost, 

 while the performance of the same test with visual stimuli was preserved. 

 The opposite was found after the ablation of the posterior parts of the 

 second and third temporal gyri and gyrus fusiformis. 



6. RELATIONS BETWEEN RECENT AND STABLE MEMORY 



It is now generally accepted that recent memory is based on the activity 

 of reverberating chains of neurones, whereas stable, or permanent memory 

 is due to some structural changes produced in the brain. The kind of 

 changes with which wc have to do here has been a matter of much specula- 

 tion. One of the possible hypotheses is that put forward long ago by 

 Tanzi (1893), Ramon y Cajal (191 1), Ariens Kappers (1917), Child (1921), 

 Coghill (1929) and others, and recently adjusted to the CR experimental 

 evidence by Konorski (1948). According to this hypothesis when an 

 indifferent stimulus is reinforced by an unconditioned stimulus, the 

 'potential connections' established in ontogenesis between the correspond- 

 ing groups of neurones are transformed into 'actual connections'. This is 

 accomplished by growing and multiplication of synaptic contacts between 

 the axons of the neurones representing the CS and bodies and/or dendrites 

 of neurones representing the UCS. 



Without going more deeply into that problem one must notice that 

 all structural theories of conditioning have so far encountered one major 

 difficulty : it is well known that quite often a CR is formed and proves to 

 be stable even after a single reinforcement, the so-called 'one trial learning'. 

 This means that a few seconds' simultaneous operation of the two stimuli 

 would be sufficient for the formation of stable connections between the 

 respective groups of neurones. 



Fig. 4 

 The effects of cortical lesions on acoustic recent memory in dogs. 



Each graph represents the percentages of negative (correct) responses, i.e. lack of movement 

 for each dog to the inhibitory CS-i in successive blocks often inhibitory trials. 



IT, infratemporal ablation, EM, ablation of gyrus ectosylvius mcdius, F, prefrontal ablation. 

 Continuous lines, responses to inhibitory compound stimuli, S^Sy (acoustic recent memory 

 test). Dashed lines, responses to inhibitory stimulus in simple acoustic differentiation. Dashed- 

 dottcd lines, reactions to inhibitory compound of conditioned inhibition, SoS. 



Arrows in the course of tone-relation differentiation (SxSx vs. SxSy) denote the end of 

 preliminary training in which only particular pairs of tones were applied. 



In the first three dogs tone-relation differentiation was totally abolished after infratemporal 

 lesion. Both differentiation and conditioned inhibition were easily established after operation. 

 In the fourth dog bilateral removal of middle ectosylvian gyrus did not affect the tone- 

 relation differentiation; the removal of prefrontal areas caused the general syndrome of 

 disinhibition which was soon compensated. 



