NORADRENALINE AND SELECTIVE ATTENTION

Rats depleted of forebrain noradrenaline by intracerebral injection of four micrograms of 6-hydroxydopamine into the dorsal noradrenergic bundle were examined on their ability to ignore irrelevant stimuli. In the latent inhibition paradigm normal rats were pre-exposed to visual and auditory stimuli in the absence of reward and such pre-exposure was found to slow subsequent learning of a successive discrimination task using these stimuli. Noradrenaline depletion blocked the usual latent inhibition effect, thus suggesting that the lesioned animals were impaired in ignoring irrelevant stimuli. A second paradigm, a nonreversal shift, involved training rats on a two-dimension discrimination task with one dimension relevant and the other irrelevant. Nonreversal shift (in which the initially irrelevant dimension became the sole relevant one) was significantly improved by 6-hydroxydopamine lesion. It is thus concluded that strong evidence has been presented in favour of a role for the dorsal noradrenergic bundle in attentional filtering processes. © 1979.