W. R. ADEY 579 



anterior influx from the septum to the dentate granule cells, which in turn 

 relayed to the hippocampal pyramidal cells, with subsequent activation of 

 the entorhinal area. Certainly the results of acute electrophysiological 

 experiments have favoured the latter pathways as a source of the rhythmic 

 slow potentials recorded in the hippocampus during various t)'pes of 

 arousal (Green and Arduini, 1954; Green and Adey, 1956; Adcy, Mcrril- 

 lecs and Sunderland, 1956; Adey, Sunderland and Dunlop, 1957; Adey, 

 Dunlop and Sunderland, 1958). It was to test aspects of these various 

 fluxes through the hippocampus in a training situation that our experiment 

 was designed. 



The test situation involved training cats in a T-maze box, with food 

 reward on the basis of a visual cue. Time-lapse photographs were taken in 

 the course of the animal's approach. Our attention was directed particu- 

 larly to the appearance of certain regular slow- wave trains at 5-6 cycles/sec. 

 in the course of the approach behaviour. All records were obtained with 

 implanted bipolar electrodes 200 pi in diameter and spaced 1.5 mm. be- 

 tween recording tips. Particular attention has been given to the use of 

 appropriate time-constants in the recording amplifiers, to record the slow- 

 wave activity undistorted, and to the elimination of artifacts from the 

 records in freely moving animals (Adey, Dunlop and Hendrix, 1959). 



Li the naive animal, during its first exposure to the training situation, 

 we found a wide distribution of slow activity extending far into the ventral 

 hippocampus, and exhibiting a wide spectrum from 4-7 cycles/sec. The 

 animal continued to show this activity until one started the training 

 procedure, and the slow activity then rapidly disappeared from the 

 ventral hippocampus in the first few trials (Fig. 2). 



After the initial presentations, regular rhythmic slow-wave trains, at 

 5-6 cycles/sec, appeared with each approach performance. This activity 

 was limited to the dorsal hippocampus, particularly in CA4, and in the 

 entorhinal area. Bursts of this 5-6 cycles/sec. activity may appear in the 

 entorhinal record on as many as three occasions in the approach per- 

 formance: once, as the animal approaches first the wrong side oi the box; 

 again, as it turns back, and a third time as it finally turns to the right side 

 of the box. In the pre-approach phase, there was often much 4 cycles/sec. 

 activity. In Fig. 3, the animal rapidly proceeded first to the wrong side 

 of the box. After a significant interval, during which the animal stood 

 stiU, moving its head from side to side, it proceeded to the right side of 

 the box. There was clearly an association of the 5-6 cycles/sec. activity 

 with each of the two phases of motor activity, with very little evidence of 

 rhythmic activity between these two bursts. By contrast, it did not seem 



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