Gain and fidelity of transmission patterns at cortical excitatory unitary synapses improve spike encoding

Abstract

Neuronal spike encoding and synaptic transmission in the brain need be precise and reliable for well-organized behavior and cognition. Little is known about how a unitary synapse reliably transmits presynaptic sequential spikes and how multiple unitary synapses precisely drive their postsynaptic neurons to encode spikes. To address these questions, we investigated the dynamics of glutamatergic unitary synapses as well as their role in driving the encoding of cortical fast-spiking neurons. Synaptic transmission patterns randomly fluctuate among facilitation, depression and parallel over time. The postsynaptic calmodulin-signaling pathway enhances initial responses and converts this fluctuation to a synaptic depression. We integrated current pulses mathematically based on synaptic plasticity and found that they improve spike capacity and timing precision by shortening the spike refractory period at postsynaptic neurons. Our results indicate that the gain and fidelity of synaptic patterns enable reliable transmission of presynaptic signals by the synapse and precise encoding of spikes by postsynaptic neurons. These reproducible neural codes may be involved in controlling well-organized behavior.

Acupuncture to point Baihui prevents ischemia-induced functional impairment of cortical GABAergic neurons

“…These neurons demonstrated fast spiking and less adaptation in spike amplitude and frequency, typical properties of interneurons [30][31][32][33][34][35][36].…”

Homeostasis established by coordination of subcellular compartment plasticity improves spike encoding

“…The behavioral regulation and stabilization are probably a result of the precise and dedicated output of signals from each neuron and bundle of neural networks. Therefore, the uniformity of synaptic patterns in transmitting sequential signals (Wang, J-H. et al, 2008), the improvement of spike timing precision (Figs 5,6) and the homeostatic plasticity in subcellular compartments of individual neurons and subpopulations of neurons in neural networks, all stabilize signal encoding, which contributes to the consistent expression of neural information, i.e. memory.…”

Acidosis and alkalosis impair brain functions through weakening spike encoding at cortical GABAergic neurons

“…These neurons demonstrated the typical properties of interneurons, such as fast-spiking and less adaptation in spike amplitudes and frequency [6,[26][27][28][29][30][31].…”

“…With these pipettes for wholecell recording, intracellular pH will be balanced with the pipettes within a few minutes. Under this condition, the recording in the beginning of a few minutes can be used as the control, an approach similar to infusing other reagents [6,9,27,34,35].…”

“…Action potentials at the neurons and their transmission at the synapses are essential codes in the brain to encode various messages of controlling well-organized behaviors and cognition [1][2][3][4][5][6]. The impairment of their encodings leads to the functional disorders and psychological deficits in neurological diseases, such as epilepsy [7], ischemia [8][9][10] and psychiatric disorders [11][12][13][14].…”