Learning impairments caused by lesions to the pedunculopontine tegmental nucleus: an artifact of anxiety?

Bilateral N-methyl-d-aspartate lesions of the pedunculopontine tegmental nucleus (PPTg) blocked the acquisition of a delayed non-matching to position task (DNMP) performed in a T-maze. This acquisition impairment, however, was reversed by pre-testing injections of diazepam (1 mg/kg). These results, in addition to the finding that PPTg lesions elevated anxiety as measured by the elevated plus maze, suggest that PPTg is not involved in learning or memory, but in the regulation of anxiety.