Modulatory effects of α7-nicotinic cholinergic receptors on perceptual sensitivity in a visual signal detection task

RationaleCholinergic signalling is critical for attentional control and signal detection, yet the contribution of specific acetylcholine receptor (AChR) subtypes remains poorly understood. Although the 7 nicotinic AChR (nAChR) holds promise as a target for cognition-enhancing therapy, clinical findings to date have been inconsistent. ObjectiveTo investigate the effects of putative cognitive enhancing drugs, including those targeting cholinergic transmission and 7 nAChRs on a visual signal detection task (SDT). MethodsMale and female Sprague Dawley rats were trained on an SDT. Cholinergic transmission was probed systemically with nicotinic and muscarinic receptor antagonists (mecamylamine and scopolamine), a cholinesterase inhibitor (galantamine), an M4-AChR positive allosteric modulator (PAM; VU0467154), an 7 nAChR antagonist (MLA), an 7 nAChR PAM (CCMI), and an 7 nAChR partial agonist (SSR-180,711). Dopaminergic transmission was probed using the catechol-O-methyltransferase (COMT) inhibitor, tolcapone. A novel, trial-level signal detection theory-based generalised linear mixed-effects model (SDT-GLMM) was used to index response bias and perceptual sensitivity (d'), the latter reflecting subjects ability to discriminate signal from noise. ResultsMecamylamine profoundly impaired SDT performance across all measures. Galantamine significantly improved d' at moderate doses but not when a distractor was present. MLA uniquely produced dose-dependent improvements in d' that were preserved under distraction. In contrast, positive allosteric modulation and agonism of 7 nAChRs impaired task performance. Scopolamine, VU0467154, and tolcapone had no consistent or interpretable effects on signal detection. ConclusionsThis work demonstrates that 7 nAChR modulation bidirectionally and dose-dependently regulates perceptual sensitivity, irrespective of attentional distraction. These findings have implications for targeted cognitive enhancement in disorders of attention.