Very Short Term Visual Memory Via Reverberation: A Role for the Cortico-thalamic Excitatory Circuit in Temporal Filling-in During Blinks and Saccades?

There is a large projection of neurons from Layer VI of V1 that makes excitatory connections on LGN relay cells. It has been proposed that this circuit is involved in signal processing and thalamic sensitivity regulation. Alternatively, Crick has suggested that the circuit could be a reverberatory loop-a site for very short-term (iconic) visual memory. This hypothesis is shown to be plausible if the reverberation is keyed to the onset of neurally initiated visual disruptions such as blinks and saccades. Neural mechanisms suppress perception during these events but little is known about temporal filling-in processes analogous to the mechanisms that fill-in spatial scotomas. Crick's reverberatory loop could provide a process for filling-in temporal scotomas with information acquired just before the disruption, thus maintaining the continuity of visual experience.