State-Dependent Effects of Stimulus Presentation Duration on the Temporal Dynamics

20 During natural vision, stimuli are viewed for different durations as the state of brain activity 21 changes over time. Here, we studied the effects of stimulus presentation duration on cell 22 responses (n=259) in three subdivisions of the inferotemporal (IT) cortex of fixating macaque 23 monkeys as neural baseline firing rates varied over the course of recording. First, cell responses 24 to the presentation of 120 images were tested and four images that elicited significant responses 25 with various degrees of effectiveness were selected for further study. Then, the four selected 26 images were presented to the monkeys for five different presentation durations (18, 70, 140, 210 27 and 350 ms). We found that, depending on the magnitude of neural baseline activity, stimulus 28 presentation duration affected the response properties and efficiency of neural information 29 processing in the IT cortex. Short stimulus presentation durations elicited phasic responses 30 consisting of rhythmic activation and inactivation, which conveyed a lower amount of stimulus 31 information, particularly following higher baseline firing rates. Longer presentation durations 32 elicited a sustained pattern of response and carried a greater amount of information, particularly 33 at lower baseline firing rates. Finally, a significantly higher proportion of cells in the posterior IT 34 compared to the anterior IT had a tendency to have high baseline activity, recruit stronger phasic 35 responses and convey less information. It is plausible that during natural vision, as stimuli with 36 various exposure durations affect the visual system, top-down influence or competition within 37 local neural networks differentially influences the function of IT cells by changing their baseline 38 activity. 39