Relation between decreased mental efficiency in mice and the presence of cerebral lesions after experimental encephalitis caused by yellow fever virus.

The behavior of 1,072 mice that had recovered from encephalitic infection with intracerebrally injected yellow fever virus 17D and of 216 normal mice was tested in a maze and on a horizontal rod rotating around its axle. Infected animals needed more time (average, 8.90 min) to find their food in a maze than did normal animals (average, 4.37 min). Infected mice were able to stay on the rotating rod for a shorter time (average, 6.4 seconds) than were normal animals (average, 9.0 seconds). The correlation between the concentration of virus injected and the performance of the mice was confirmed by the extent of lesions found by histologic study: animals that had anatomic lesions after surviving encephalitic infection showed abnormal behavior.