Comparison of the role of somatosensory stimuli in maze learning in a blind subterranean rodent and a sighted surface-dwelling rodent

We compared the role of tactile perception in maze learning in the blind mole rat and in the laboratory rat. Both species were tested in each of two mazes that were identical in complexity but differed in tunnel width and height: the first was only slightly wider than the animal's body width (narrow maze) while the second was about twice the animal's body width (wide maze). We found that the performances of rats tested in the narrow maze were significantly lower than those tested in the wide maze, as measured by time and number of errors to reach the end of the maze (food reward). The mole rats, in contrast, performed significantly better in the narrow maze than in the wide maze. Further, in contrast to the rats, the mole rats' locomotion in the wide maze was much less continuous than in the narrow maze, reflected in longer and more frequent stops at maze junctions, where they pressed the side of their body tightly against the tunnel walls. Two main conclusions are derived from this experiment. First, subterranean mammals, such as the blind mole rat, appear to rely more on tactile stimuli while exploring and learning a complex maze than do sighted surface-dwelling rodents, such as rat. The extensive use of this somatosensory channel may compensate for the mole rats' visual deficiency, and thus substantially contribute to their excellent spatial orientation ability, previously demonstrated in field and laboratory conditions. Second, poor performance of surface-dwelling rodents, such as the rats, in spatial-maze learning tasks might not be a consequence of impaired cognitive learning ability, but rather due to testing the animal in a physical situation that does not provide the necessary somatosensory stimuli found in their natural habitat. (C) 2004 Elsevier B.V. All rights reserved.