Measuring attention in rats with a visual signal detection task: Signal intensity vs. signal duration

Measurement of attentional performance in animal behavioral research allows us to investigate neural mechanisms underlying attentional processes and translate results to better understand human attentional function, dysfunction and drug treatments to reverse dysfunction. One useful method to measure attention in experimental animal studies is to use an operant visual signal detection paradigm, consisting of two levers and the rapid flashing of a cue lamp to signal a reward. In this study, we tested the relative sensitivity of this task when using different variants of the stimulus signal, varying brightness or duration of the light cue. To investigate roles of different neural systems underlying attentional processes, we assessed the sensitivity of attentional performance with these two different cue variations with blockade of muscarinic acetylcholine and NMDA glutamate receptors with scopolamine and MK-801 (dizocilpine). Operant signal detection was tested using a signal light that varied in intensity (0.027, 0.269, 1.22 lx) of the signal light or in a paradigm which varied the duration (0.5 s, 1 s, 2 s) of the signal light. Both methods of assessing attention showed construct validity for producing gradients of accuracy for signal detection; the dimmest cue led to less accurate responding compared to the brighter cues, and the shortest duration led to less accuracy compared to the longer durations. However, the tests differed in their sensitivity to pharmacological disruption. With the duration test, the high dose of MK-801 along with co-exposure of scopolamine and MK-801 caused a significant reduction of hit and rejection accuracy. Conversely, the intensity variation test did not show significant differences as a function of drug exposures. These data suggest that changes in signal duration, rather than signal intensity, during operant signal detection may have higher sensitivity to detecting drug effects and be a more useful technique for examining pharmacological interventions on attentional behavior and performance.