Memory for conditioned taste aversions is diminished by transcranial magnetic stimulation

Rats were allowed to drink distinctively flavored water and later received an IP injection of LiCl. In Phase I, between drinking and the onset of the mild malaise, Experimental Group rats received stimulations of the head and Controls received equivalent stimulations of the back. Later, when the flavor was again presented. Experimentals drank 10-15% more, indicating that they had forgotten to some extent that the flavor was associated with illness. In Phase II, the procedure was repeated with a different distinctive flavor. Again, the Experimentals drank more on the test day. In Phase III, all rats received stimulations of the back between tasting and illness. Experimentals and Controls were not different on the test day, indicating that 100 prior head stimulations did not interfere with the establishment of a new taste aversion. Histological examinations revealed no gross morphopathology. We conclude that 50 brief pulse transcranial magnetic stimulations may cause a retrograde memory disruption, but we find no evidence for an anterograde memory effect or for structural changes.