Fig. 1. (A) Experimental arrangement for conditioning. A syringe containing water
or saline solution was used for conditioning. A filter paper soaked with
peppermint or vanilla essence was attached to the needle of the syringe 10mm
from its tip (see left). The filter paper was placed within 1 cm of the
cricket's head so as to present a particular odour, and water or saline was
then presented to the mouth (right). (B) The apparatus used for the odour
preference test. WCH, waiting chambers; TCH, training chamber; CH, container
holder; RA, rotating axle; OS, odour source; N, gauze net; SD, sliding door;
H, holes connecting the chamber with two of three odour sources. (C) Typical
time schedule for training and testing; preference tests (PTs, open columns)
were performed before (PT-0) and 2 h (PT-1), 1 day (PT-2) and 4 days (PT-3)
after training (Tr, filled column). The white and black parts of the time bar
indicate photophase (12 h) and scotophase (12 h), respectively. A typical
stimulus schedule for training is illustrated at the bottom, in which the
hatched and shaded bars above the line indicate the presentation of peppermint
or vanilla odour, and the white and black squares below the line indicate the
presentation of water or saline solution, respectively. For appetitive
conditioning, peppermint odour was associated with water (reward); for
aversive conditioning, vanilla odour was associated with saline solution
(punishment).
