A cross-species investigation of acetylcholine, attention, and feature binding.

The binding problem is the brain's fundamental challenge to integrate sensory information to form a unified representation of a stimulus. A recent nonhuman animal model suggests that acetylcholine serves as the neuromodulatory substrate for feature binding. We hypothesized that this animal model of cholinergic contributions to feature binding may be an analogue of human attention. To test this hypothesis, we conducted a cross-species study in which rats and humans learned comparable intramodal feature-conjunction (FC) and feature-singleton (FS) tasks. We challenged the cholinergic system of rats using the muscarinic antagonist scopolamine (0.2 mg/kg) and challenged the attentional system of humans by dividing attention. The two manipulations yielded strikingly similar patterns of behavior, impairing FC acquisition, while sparing FS acquisition and FC retrieval. These cross-species findings support the hypothesis that cholinergically driven attentional processes are essential to feature binding at encoding, but are not required for retrieval of neural representations of bound stimuli.