How details of action potential generation influence encoding in neocortical neurons

21 июня (четверг), в 15.00 в конференцзале состоится доклад профессора Университета Коннектикута и сотрудника ИВНД Максима Волгушева

The abilities of neuronal populations to encode rapidly-varying stimuli and respond fast to abrupt input changes are crucial for basic neuronal computations, such as coincidence detection, grouping by synchrony and spike-timing-dependent plasticity, as well as for the processing speed of neuronal networks. Theoretical analysis has linked these abilities to onset dynamics of action potentials (APs). Using a combination of whole cell recordings from neurons in rat neocortex and computer simulations, we provide first experimental evidence for this conjecture and prove its validity for the case of distal AP initiation in the axon initial segment (AIS), typical for cortical neurons. We show that neocortical neurons generating APs with fast onset dynamics can encode rapidly changing signals by phase-locking their population firing to signal frequencies up to ~300-400 Hz and respond very fast, within 1-2 ms, to subtle changes of input current. In multicompartment conductance based models that reproduce spatial pattern of AP initiation in the AIS, encoding depends on AP onset dynamics at the initiation site. In neocortical neurons in which AP onset was slowed down by experimental manipulations, or was intrinsically slow due to immature AP generation mechanisms, the ability to encode high frequencies and response speed were dramatically reduced. We conclude that fast onset dynamics is a genuine property of cortical AP generators. It enables fast computations in cortical circuits, rich of recurrent connections both within each region and across the hierarchy of areas.