Further information about the wireless sensor node is available in [34].Figure 3.Wireless nodes. (a) Sensor node; (b) Master node.The master node shown in Figure 3b [40,41] receives processed data from the sensor nodes through short-range wireless communication (ISM band) and transmits these data to the monitoring server through long-range (Code Division Multiple Access��CDMA, [42]) communication. Four senso
The human brain consists of approximately one hundred billion neurons interconnected in a complex way to perform computational, cognition and memory tasks. Neurons usually interact via synapses, which allow information transmission from one cell to the other. Each neuron has an average of 7,000 synaptic connections.

Being subserved by a complex molecular mechanism, the synapses are capable of changing the efficiency of signal transmission between neurons by sensing electrical activity and chemical concentrations. It is believed that the flexibility of the synaptic connections (e.g., synaptic plasticity) underlies the implementation of computational and cognitive tasks in brain networks. While in living cells, the synaptic plasticity is mediated by complex molecular transformation, in an artificial biosystem, the synaptic transmission can be regulated by adjusting the parameters of an artificial synapse.Significant efforts have been made to represent a synapse by a single device that mimics synaptic connections and behavioral flexibility. This challenging task for biorobotics would allow a direct linkage between neuroscience and artificial intelligence.

Any attempt to construct an artificial brain must GSK-3 consider its complexity. Several attempts have already been made. For example, Sharp et al. [1] used an electronic circuit to couple two living stomatogastric ganglia neurons. Synaptic behavior has also been imitated by hardware-based neural networks, such as hybrid complementary metal-oxide-semiconductor analogue circuits and other artificial neural devices [2�C4] capable of mimicking the major features of human memory; namely, sensory, short-term and long-term memories. Great progress in nanotechnology has provided significant advances in the miniaturization of synthetic synapses, e.g., the fabrication of a carbon nanotube synaptic circuit [5]. Artificial synaptic devices based on ion migration have been also designed [6]; some of them [7,8] have demonstrated spike-timing-dependent plasticity [9], the important mechanism of brain memory, related to the synaptic connection strength in biological circuits and synthetic devices. These devices require precise control of the signal timing to simulate the pre- and post-synaptic potentials in biological systems.