Selective deficits in attentional performance on the 5-choice serial reaction time task following pedunculopontine tegmental nucleus lesions

Sustained attention requires the integrity of basal forebrain cholinergic s ystems. The pedunculopontine tegmental nucleus (PPTg) has direct and indire ct connections (via the thalamus) with the basal forebrain, suggesting that the PPTg may also play an important role in attentional processes. We exam ined this hypothesis by testing the effects of PPTg lesions in rats on perf ormance in the 5-choice serial reaction time test. Bilateral lesions reduce d accuracy, increased errors of omission, and increased the latency to corr ect responses. The deficits were more severe when neuronal damage was bilat eral and concentrated in the posterior PPTg. Attentional demands of the tas k were increased by decreasing the stimulus duration, the stimulus brightne ss, or the inter-trial interval, and by introducing random bursts of white noise. These challenges impaired performance of all animals, but the magnit ude of deficit was increased in the lesioned group. Conversely, lesion-indu ced deficits were partially alleviated when the attentional demands of the task were reduced. This pattern of results suggests that PPTg lesions produ ce a global deficit in attention, rather than a specific impairment in one process. The PPTg may control attentional processes through its direct proj ections to the forebrain cholinergic system or, indirectly, through activat ion of thalamocortical projections. (C) 2001 Elsevier Science B.V. All righ ts reserved.