Synchrony, Excitability and Firing Frequency in Neurons Containing Dendritic A-type Potassium Currents

Synchrony, Excitability and Firing Frequency in Neurons Containing Dendritic A-type Potassium Currents Current interpretations of mental processes in neuroscience usually focus on the properties of either single nerve cells or of large networks of neurons. The interplay between the cellular and the network levels remains, however, poorly understood. Based on existing experimental evidence, we suggest a participation of A-type potassium channels (KA) in the interaction between the two levels. In this project we investigate, more precisely, the role of KA in linking network synchrony to cellular excitability and firing frequency. The analysis of the notion of synchrony is of particular importance in this work due to its conceptual and modeling implications. The study uses computer simulations with biophysical models of cellular structures and of six different KA ion-channels described by Hodgkin-Huxley dynamics. First, simple simulations reveal how KA can affect excitability and how the effects can be modified through KA modulation. The results indicate that the attenuating properties of KA should be interpreted in terms of absolute local attenuation. We show that other possible appealing interpretations are actually based on misconceptions. Additional results confirm a crucial role of KA in avoiding hyperexcitability, as suggested in several studies related to epilepsy. Thereafter, with more detailed models, simulations at different levels of synchrony prove that KA, via its modulation, mediates between the network synchrony and the cellular response. This trilateral relationship suggests that mental activity resulting from the interaction between cells and networks could be altered through KA modulation. Finally, we discuss the possibility of preventing synchronization by means of dendritic ion-currents and propose, for this particular purpose, some favorable conditions regarding Hodgkin-Huxley variables.