Bi-stable perception has been an important tool to investigate how visual input is interpreted and how it reaches consciousness. To explain the mechanisms of this phenomenon, it has been assumed that a mutual inhibition circuit plays a key role. It is possible that this circuit functions to resolve ambiguity of input image by quickly shifting the balance of competing signals in response to conflicting features. Recently we established an in vitro neural recording system combined with computerized connections mediated by model neurons and synapses (“dynamic clamp” system). With this system, mutual inhibition circuit between two pyramidal cells from primary visual cortex were established by model inhibitory neurons and model synapses. Simultaneous injection of depolarizing current to the two pyramidal cells caused bi-stable activities: dominance of neural activities alternated between the two neurons with an interval of several seconds. We report the effect of adding noise to the (real) pyramidal cells and the (model) inhibitory neurons. Both excitatory and inhibitory synaptic conductance noise was modelled and given to these neurons while the pyramidal cells were exhibiting bi-stable activity. The histogram of the dominant activity durations showed gamma-like skewed distributions. The skewedness was enhanced by increasing the standard deviation of the conductance noise and the durations decreased overall. While adaptation of the dominant neuron and recovery (from adaptation) of the suppressed neuron caused a decrease and increase of their excitabilities, the fluctuation of membrane potentials due to the given conductance noise appeared to facilitate the reversal of the dominance
