Fig. 2.

Spontaneous activity assayed by photobeam crossing. Individual mice were removed from their home cage and placed in the photobeam apparatus for 40 hr. The number of successive beam crossings (ambulation) was recorded and is expressed per hour. Control mice (n = 8; 4 males) explored this new environment extensively for the first 24 hr period and then settled into a regular activity pattern on the second day. The mice born to infected mothers (n = 10; 5 males) failed to display the early, active exploration pattern seen in the controls, but beginning on the second night, their baseline activity level was not different from the controls. *p < 0.05; **p < 0.01.