Validity of head-dipping as a measure of exploration in a modified hole-board.

To determine whether head-dipping could be validated as a measure of exploration a modified hole-board was developed with four holes in the floor, under which novel objects could be placed. Two criteria for considering head-dipping as a measure of exploration were proposed: firstly that it should reflect novel aspects of the environment; secondly, that exposure to the hole-board should result in information storage. That head-dipping reflected novelty was indicated by the longer duration of head-dips on initial exposure if objects were present, and also on a second exposure when objects were introduced for the first time. Information storage was indicated by habituation on re-exposure to the hole-board. A significant positive correlation between head-dipping in the "four" and "sixteen" hole-boards was obtained for rats, but not for mice. This provided some indirect evidence that rat head-dipping in the "sixteen hole-board" also reflects exploration. (+)Amphetamine and alcohol were tested in the modified hole-board, and (+)amphetamine decreased and alcohol increased the frequency and duration of head-dips.