Abstract
When ambiguous stimuli are intermittently presented, the prevalence of perceptual alternations depends on the duration of the intermittent blank interval. Short interruptions (<0.5 s) cause perceptual alternations, whereas long interruptions (>1.0 s) stabilize perception into long sequences of one dominant interpretation. Here we show how response characteristics of sensory neurons in macaque area MT are influenced by the interruption duration during the intermittent presentation of three different motion stimuli: 1) ambiguous structure-from-motion, 2) unambiguous motion, 3) dynamic random noise. For all stimulus types, spike rate variability decreased when interruption durations were systematically increased from 250 to 2,000 ms. Activity fluctuations between subsequent trials and Fano Factors over full response sequences were both lower with longer interruptions, while spike-timing patterns became more regular. These changes were independent of general adaptation effects and accompanied by increases of spectral power in the high Gamma range of the local field potential, suggesting an increased involvement of the local cortical network. In general, such a network-driven neuronal response stabilization with repeated stimuli may increase the signal-to-noise-ratio of the neural code and allow a more efficient information transfer among neurons. In the particular case of ambiguous stimuli, where perception may depend on small fluctuations in neural activity, a blank interval dependent reduction of response variability could be a crucial determinant of the perceptual stabilization of intermittently presented visual ambiguities.
This work was supported by an NWO-VIDI grant and a Utrecht University High Potential grant, both awarded to RvW.