The breakup of a spiral wave by blockade of sodium and potassium channels in a small-world network of Hodgkin-Huxley neurons is investigated in detail. The influence of ion channel block in poisoned excitable membrane patches of a certain size is measured, by varying channel noise and channel densities resulting from the change in conductance. For example, tetraethylammonium is known to cause a block (poisoning) of potassium channels, while tetrodotoxin blocks sodium channels. We observed the occurrence of spiral waves, which are ordered waves believed to play an important role in facilitating the propagation of electric signals across quiescent regions of the brain. In this paper, the effect of channel block was measured by the factors x K and x Na , which represent the ratios of unblocked, or active, ion channels, to the overall number of potassium or sodium ion channels, respectively. To quantify these observations, we use a simple but robust synchronization measure, which succinctly captures the transition from spiral waves to other collective states, such as broken segments resulting from the breakup of the spiral wave. The critical thresholds of channel block can be inferred from the abrupt changes occurring in plots of the synchronization measure against different values of x K and x Na . Notably, small synchronization factors can be tightly associated with states where the formation of spiral waves is robust to mild channel block. A spiral wave is a characteristic spatiotemporal pattern that is often observed in excitable media [1][2][3][4][5][6][7][8][9][10]. The formation and propagation of spiral waves in reaction-diffusion systems have been studied extensively [11][12][13][14][15][16], and some effective schemes have been used to remove spiral waves and prevent ventricular fibrillation [17]. Stable rotating spiral waves have been observed in rat neocortical slices visualized by voltage-sensitive dye imaging [18,19]. Spiral waves might serve as emergent population pacemakers, generating periodic activity in non-oscillatory networks without individual cellular pacemakers. The formation, death, and breakup of spiral waves in the mammalian cortex can be simulated using regular and/or small-world networks [8][9][10].In networks using Hodgkin-Huxley model neurons [20], the effects of channel noise [21,22] on spiral waves needs to be studied in detail.Normal signal propagation between neurons in networks with different topologies deeply depends on the collective behavior of neurons. Abnormalities of neurons in one domain can destroy the normal communication between neurons, and neurological disorders can occur when the normal electrical activity of neurons is violated. The response of neurons to external stimuli (drugs or electrical forcing) is often a result of the collective behaviors of all the neurons in one or more domains. It is reliable to study the collective electrical activities of neurons in functional domains using complex network schemes. Most previous schemes have been proposed to remove spira...