Takeshi Mita

Analysis of neuronal cells of dissociated primary culture on high-density CMOS electrode array

Spontaneous development of neuronal cells was recorded around 4-34 days in vitro (DIV) with high-density CMOS array, which enables detailed study of the spatio-temporal activity of neuronal culture. We used the CMOS array to characterize the evolution of the inter-spike interval (ISI) distribution from putative single neurons, and estimate the network structure based on transfer entropy analysis, where each node corresponds to a single neuron. We observed that the ISI distributions gradually obeyed the power law with maturation of the network. The amount of information transferred between neurons increased at the early stage of development, but decreased as the network matured. These results suggest that both ISI and transfer entropy were very useful for characterizing the dynamic development of cultured neural cells over a few weeks.

Development of neural population activity toward self-organized criticality

Self-organized criticality (SoC), a spontaneous dynamic state established and maintained in networks of moderate complexity, is a universal characteristic of neural systems. Such systems produce cascades of spontaneous activity that are typically characterized by power-law distributions and rich, stable spatiotemporal patterns (i.e., neuronal avalanches). Since the dynamics of the critical state confer advantages in information processing within neuronal networks, it is of great interest to determine how criticality emerges during development. One possible mechanism is developmental, and includes axonal elongation during synaptogenesis and subsequent synaptic pruning in combination with the maturation of GABAergic inhibition (i.e., the integration then fragmentation process). Because experimental evidence for this mechanism remains inconclusive, we studied the developmental variation of neuronal avalanches in dissociated cortical neurons using high-density complementary metal-oxide semiconductor (CMOS) microelectrode arrays (MEAs). The spontaneous activities of nine cultures were monitored using CMOS MEAs from 4 to 30days in vitro (DIV) at single-cell spatial resolution. While cells were immature, cultures demonstrated random-like patterns of activity and an exponential avalanche size distribution; this distribution was followed by a bimodal distribution, and finally a power-law-like distribution. The bimodal distribution was associated with a large-scale avalanche with a homogeneous spatiotemporal pattern, while the subsequent power-law distribution was associated with diverse patterns. These results suggest that the SoC emerges through a two-step process: the integration process accompanying the characteristic large-scale avalanche and the fragmentation process associated with diverse middle-size avalanches.

Multiple Time Scales Observed in Spontaneously Evolved Neurons on High-density CMOS Electrode Array

Spontaneous evolution of neural cells was recorded around 4-34 days in vitro (DIV) with high-density CMOS microelectrode array, which enables detailed study of the spatiotemporal activity of cultured neurons. We used the CMOS array to characterize 1) the evolution of activation patterns of each putative neurons, 2) the developmental change in cell-cell interactions, and finally, 3) emergence of multiple timescales for neurons to exchange information with each other. The results revealed not only the topology of the physical connectivity of the neurons but also the functional connectivity of the neurons within different time scales. We finally argued the relationship of the results with “functional networks”, which interact with each other to support multiple cognitive functions in the mature human brain.

Locally embedded presages of global network bursts

Significance This paper reports an approach to detecting the “early warnings” of upcoming global state transitions in a network based on its local dynamics, demonstrating that seemingly stochastic global events can be predicted by local deterministic dynamics. Based on the method using a nonlinear state-space reconstruction, we show that, surprisingly, dynamics of individual neurons can robustly predict the upcoming synchronous burst in the neural population at high signal-to-noise ratios, which even outperform the predictions based on population activity. We explain this apparently counterintuitive property by the network structures realizing in the nonbursting period, which is supported by a manipulative experiment and analyses. These results reveal basic properties of the bursting network dynamics. Spontaneous, synchronous bursting of neural population is a widely observed phenomenon in nervous networks, which is considered important for functions and dysfunctions of the brain. However, how the global synchrony across a large number of neurons emerges from an initially nonbursting network state is not fully understood. In this study, we develop a state-space reconstruction method combined with high-resolution recordings of cultured neurons. This method extracts deterministic signatures of upcoming global bursts in “local” dynamics of individual neurons during nonbursting periods. We find that local information within a single-cell time series can compare with or even outperform the global mean-field activity for predicting future global bursts. Moreover, the intercell variability in the burst predictability is found to reflect the network structure realized in the nonbursting periods. These findings suggest that deterministic local dynamics can predict seemingly stochastic global events in self-organized networks, implying the potential applications of the present methodology to detecting locally concentrated early warnings of spontaneous seizure occurrence in the brain.

Emergence of Sense-Making Behavior by the Stimulus Avoidance Principle: Experiments on a Robot Behavior Controlled by Cultured Neuronal Cells.

Robot experiments using real cultured neuronal cells as controllers are a way to explore the idea of embodied cognition. Real cultured neuronal cells have innate plasticity, and a sensorimotor coupling is expected to develop a neural circuit. Previous studies have suggested that a dissociated neuronal culture has two properties: i) modifiability of connection between neurons by external stimuli and ii) stability of the connection without external stimuli. If cultured neuronal cells are embodied by coupling to an environment, they learn to avoid external stimulation. We call this mechanism a “learning by stimulation avoidance” principle. We try to demonstrate that adaptive behavior, like wall avoidance, can emerge spontaneously from embodied cultured neuronal cells. In this study, we developed a system in which a robot moves in a real environment and is controlled by cultured neuronal cells growing on a glass plate. We used a high-density complementary metal-oxide-semiconductor array to monitor the neural dynamics. We then conducted a robotic experiment using this platform. The results showed that wall-avoidance behavior by a robot can be enhanced spontaneously without giving any reward from the external environment.

Identification of diverse synchrony patterns in dissociated cortical culture using Bayesian non-negative matrix factorization

Synchrony in a neuronal network is not just a spontaneous event but rather a representation of inner information. In this point of view, the variety of synchrony patterns is considered to be related to inner capacity of the network. However, evaluating and comparing the variety of synchrony patterns, especially between different samples or different times, is difficult. In this paper, we proposed to identify the variety of synchrony based on Bayesian model selection. Hypothesizing that globally synchronized activity consists of partial synchrony, we attempted to identify reproducible-spatial pattern bases in spontaneous bursting activities of dissociated cortical cultures using Bayesian non-negative matrix factorization. Neuronal activity was recorded with high-density CMOS electrode arrays. Bayesian treatment provides evidence for selection of the number of bases based on marginal likelihood. We compared model evidence of the activity in juvenile and matured cultures. Our results suggested that the variety of synchrony patterns diversify through maturation.

Measurement of action potentials of dissociated cultured neurons by high density CMOS array and network analysis

neurosurgical protocols and flexible probes fabricated with micro-electromechanical systems. To evaluate the feasibility of intrasulcal ECoG, we first inserted parts of the probe into the superior temporal sulcus (STS) to compare ECoG responses from the ventral bank of STS with those from the inferior temporal gyrus (ITG). We found no location effect (STS or ITG) on the power spectral density (PSD) of the intertrial interval response (p = 0.66, two-way ANOVA) and no significant interaction between frequency and location (p = 0.82). There was a significant effect of frequency on the PSD (p < 10–16). Signal-to-noise ratio of the visually evoked ECoG responses in STS (1.55 ± 0.62, mean ± SD, n = 34) was not significantly different from those in ITG (1.59 ± 0.62, n = 187) (p = 0.73, t-test). Histological examination revealed no obvious physical damage in the implanted cortical areas. Second, we placed an ECoG probe into the central sulcus to stimulate the anterior bank of the sulcus and the surface of the precentral gyrus. Thresholds for muscle twitching were significantly lower during intrasulcal stimulation (1.0 ± 0.2 mA, n = 43) compared to gyral stimulation (3.6 ± 0.4, n = 50) (p < 0.001, t-test). These results demonstrate the feasibility of intrasulcal ECoG in macaque monkeys. This work was supported by SRPBS from MEXT. Research fund: SRPBS.