Learning a new behavioral task is an exploration process that involves the formation and modulation of sets of associations between stimuli and network's responses. The dissociated rat hippocampal neurons were cultured on a multi-electrode array (MEA) substrate. So the electrophysiological activity can be extracellularly recorded, the response of network dynamics induced by electrical pulse stimulation can be analyzed using the recorded data. The test stimuli patterns were different interval twice stimuli. Each stimulus is voltage-controlled pulses (100μs at +0.6V, followed by 100μs at -0.6V). With the intervals between two stimuli decreasing such as a series of 100ms, 50ms, 20ms and 10ms, the response duration of cultured neuronal network increased. The firing rate of neuronal network was affected by the stimuli patterns: compare with the spontaneous firings of neurons, after the quick electrical stimulation (10ms interval stimuli pattern), the firing rate of neuronal network increases. On the contrary, the slow electrical stimulation (100ms interval stimuli pattern) depresses the firing rate of neuronal network.
Many mammalian neuronal networks, such as Central Nervous System (CNS), fire single spikes and complex spike burst. In fact, the conditions for triggering burst are not well understood. In the paper multi-electrode array (MEA) is used to record the spontaneous electrophysiology activity of cultured rat hippocampal neuronal networks for long-term. The transition from single spikes to burst is observed on networks that is cultured about 3 weeks and quickly fire before burst activity. The firing rate during burst is lower than that before burst, but the difference of inter spike intervals (ISIs) between the two firing patterns is not distinctness. Moreover, the electrical activities on neighboring electrodes show strong synchrony during burst activity. In a word, the generation of burst requires that network has a sufficient level of excitation as well as the balance by synaptic inhibition.