Figure 1.

Schematic diagram of the proposed network model of contextual memory retrieval within the hippocampus where an astrocyte modulates synchronous firing of a pack of four CA1 pyramidal neurons during context-dependent memory retrieval. The pack of neurons is aligned within 100 μm of the stratum pyramidale along the input, i.e., Schaffer collateral (SC) axons of the CA3 pyramidal neuron, which makes synapses with the spines of the proximal apical dendrites of CA1 pyramidal cells in the stratum radiatum. The field potential recording electrode is placed next to the CA1 neuron 4, at the most distal end to the input of this pack. The fine processes of the astrocyte, allied with the neuronal pack and located in the stratum oriens, listen to the synaptic transmission which takes place in the stratum radiatum, at the synapse made by the CA3 pyramidal neuron onto the lead CA1 pyramidal neuron 1 (the utmost left, proximal to the input). The astrocyte integrates received information and relays the signal to the following CA1 pyramidal neurons within the pack (in this case the three remaining CA1 pyramidal neurons 2–4, distal to the input) associated with the context of the input signal from the CA3 pyramidal neuron concurrently, the astrocyte also potentiates the SC-CA1 synapse strengthening, the small network activity.