The Neurobiology of Mammalian Navigation.

Spatial and non-spatial learning in turtles: the role of medial cortex.

Reversal learning deficit in a spatial task but not in a cued one after telencephalic ablation in goldfish.

Turtles (Pseudemys scripta) were trained in place, cue, and control arm maze procedures. The turtles learned both tasks with accuracy. Subsequent probe and transfer trials revealed guidance and mapping strategies by the cue and the place groups, respectively. Thus, the turtles in the cue procedure solved their task by directly approaching the single individual intramaze cue associated with the goal, whereas the animals in the place task seemed to be using a maplike representation based on the encoding of simultaneous spatial relationships between the goal and the extramaze visual cues. Furthermore, the turtles in the place task were able to navigate with accuracy to the goal from unfamiliar start places, and their performance was resistant to a partial loss of relevant environmental information. The results reveal for the first time, to our knowledge, spatial learning and memory capabilities in a reptile that closely parallel those described in mammals and birds.

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Place and cue learning in turtles

Turtles (Pseudemys scripta) were trained in place, cue and control open-field procedures The turtles trained in both the place and the cue procedures were able to learn their respective tasks with accuracy Subsequent probe tests revealed that the turtles trained in the place task relied on the information provided by the extramaze cues to locate the goal However, for these animals, no single cue was essential for performance, as accurate navigation to the goal was still possible when subsets of extramaze cues were eliminated Furthermore, the turtles trained in the place task were able to navigate accurately to the goal place from new start locations These results suggest that the turtles trained in the place task used map-like, relational strategies, by encoding the simultaneous spatial relationships between the goal and the extramaze cues in an allocentric frame of reference In contrast, the turtles trained in the cue procedure used guidance strategies, ie approaching the individual intramaze cue associated to the goal as it were a beacon and largely ignoring the extramaze cues Thus, the results of this experiment suggest that turtles are able to employ spatial strategies that closely parallel those described in mammals and birds

Spatial learning in turtles

Three tests investigated how the geometric relation between object/landmarks and goals influenced spatial choice behavior in rats. Two groups searched for hidden food in an object-filled circular arena containing 24 small poles. For the “Proximal” group, four distinct objects in a square configuration were placed close to four baited poles. For the “Distal” group, the identical configuration of objects was rotated 45° relative to the poles containing the hidden food. The Proximal group learned to locate the baited poles more quickly than the Distal group. Tests with removed and rearranged landmarks indicated that the two groups learned to use the objects differently. The results suggested that close proximity of objects to goals encouraged their use as beacons, while greater distance of objects from goals resulted in the global encoding of the geometric properties of the arena and the use of the objects as landmarks.

Traci L. Tauro

Papers

Object-goal positioning influences spatial representation in rats.