Neural representation of 270° by a dlPFC delay cell. Low, but not high, doses of a nic-α7R agonist enhance the neural representation of visual space by dlPFC delay cells. (a) A dlPFC delay cell has weak, delay-related firing under control conditions, with subtle representation of 270°. (b) Iontophoresis of a low dose of the nic-α7R agonist PHA543613 (at 20 nA) enhances the representation of 270° by increasing persistent firing across the delay period only in trials in which the monkey is remembering 270°. (c) A higher dose of PHA543613 (at 40 nA) increases persistent firing for all directions, thus eroding the information held in working memory stores. Thus, low doses are often essential to be effective cognitive enhancers. Abbreviations: dlPFC, dorsolateral prefrontal cortex; nic-α7R, nicotinic α7 receptor.