Spatial pattern learning in rats: Conditional control by two patterns

No evidence for overshadowing or facilitation of spatial pattern learning by visual cues

“…Clearly, the visual cues came to control behavior, as is shown by the large difference in the choice accuracy of rats in the groups trained with visual cues and the group trained without visual cues. In addition, the square pattern clearly controlled choices during the test phase, albeit to a similar limited degree as has been reported in previous experiments from our laboratory (Brown et al, 2000;Brown & Terrinoni, 1996;Lebowitz & Brown, 1999). Critically, however, there was no evidence that the degree of control by the square pattern differed among the groups.…”

“…In our previous experiments involving the pole box, as in most experiments concerned with spatial performance, choices were coded by human observers. We have made earlier (but unsuccessful) attempts to automate the measurement of choices in the pole box in order to increase the efficiency and objectivity of our data collection procedure (Brown et al, 2000). In the present experiment, pole choices were measured by using computer video capture technology.…”

“…The mean of these proportions was compared with the mean proportion that would be expected on the basis of chance. Chance is defined (for each rat) as the mean proportion of adjacent, previously unvisited poles (available at the time these choices were made) that conformed to the square pattern (for additional details, see Brown et al, 2000;Brown & Terrinoni, 1996;Lebowitz & Brown, 1999). The bottom panel of Figure 4 shows the corresponding proportions for choices made immediately following the discovery of the third baited pole.…”

“…As in Experiment 1, these "sham baits" were not retrievable by the rats (because they were under the nylon mesh floor). Their purpose was to rule out any possibility that baited and unbaited poles could be discriminated on the basis of smell (see Brown et al, 2000;Brown & Terrinoni, 1996;Lebowitz & Brown, 1999, for further evidence against this possibility). The sham bait pellets were replaced weekly.…”

“…Thus, if rats learn the spatial pattern formed by the baited poles, discovery of one or more baited poles provides information about the location of the remaining baited poles. We have shown that several such spatial patterns can indeed control behavior (Brown, DiGello, Milewski, Wilson, & Kozak, 2000;Brown & Terrinoni, 1996;Brown, Zeiler, & John, 2001;DiGello, Brown, & Affuso, in press;Lebowitz & Brown, 1999).…”