Encoding of Time-varying Stimuli in Populations of Cultured Neurons |
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Authors: | Laura Cozzi Paolo D’Angelo Vittorio Sanguineti |
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Institution: | (1) Department of Informatics, Systems and Telematics, University of Genova, Via Opera Pia 13, 16145 Genova, Italy |
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Abstract: | We wondered whether random populations of dissociated cultured cortical neurons, despite of their lack of structure and/or
regional specialization, are capable of modulating their neural activity as the effect of a time-varying stimulation – a simulated
‘sensory’ afference. More specifically, we used localized low-frequency, non-periodic trains of stimuli to simulate sensory
afferences, and asked how much information about the original trains of stimuli could be extracted from the neural activity
recorded at the different sites. Furthermore, motivated by the results of studies performed both in vivo and in vitro on different
preparations, which suggested that isolated spikes and bursts may play different roles in coding time-varying signals, we
explored the amount of such ‘sensory’ information that could be associated to these different firing modes. Finally, we asked
whether and how such ‘sensory’ information is transferred from the sites of stimulation (i.e., the ‘sensory’ areas), to the
other regions of the neural populations.
To do this we applied stimulus reconstruction techniques and information theoretic concepts that are typically used to investigate
neural coding in sensory systems.
Our main results are that (1) slow variations of the rate of stimulation are coded into isolated spikes and in the time of
occurrence of bursts (but not in the bursts’ temporal structure); (2) increasing the rate of stimulation has the effect of
increasing the proportion of isolated spikes in the average evoked response and their importance in coding for the stimuli;
and, (3) the ability to recover the time course of the pattern of stimulation is strongly related to the degree of functional
connectivity between stimulation and recording sites.
These observations parallel similar findings in intact nervous systems regarding the complementary roles of bursts and tonic
spikes in encoding sensory information.
Our results also have interesting implications in the field of neuro-robotic interfaces. In fact, the ability of populations
of neurons to code information is a prerequisite for obtaining hybrid systems, in which neuronal populations are used to control
external devices. |
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