Heart-Rate Responses and Hebb-Williams Maze Performance in Three Different Age Groups of Rats

Abstract

A study was carried out to examine heart-rate changes and changes in performance levels in Hebb-Williams maze in three different age groups of rats (21, 43, and 83 days old). Heart rate was recorded using a miniature FM radio transmitter. The rats were first exposed to 6 odd Hebb-Williams maze items and were retested 12 days later using 6 even test items. The main findings were: over-all the heart rate was significantly higher in the 21-day-old group and heart rate in this group decreased during the running of the maze while it increased in the other two groups. Heart-rate responses increased as a function of trials in all the groups and increased most sharply for the 21-day-old group. On retest a significant over-all decrease occurred in the heart-rate responses. The short-term reliability of heart rate was quite high for all the age groups. The 21-day-old group rats made significantly fewer errors in the Hebb-Williams maze when compared with the two older groups but the test-retest reliability of the Hebb-Williams maze scores was very low in the 21-day group relative to the other two. The results are discussed in terms of response inhibition and changes in drive level as a function of age. Questions are also raised concerning the validity of the Hebb-Williams maze test as a measure of problem-solving behavior.