Spatio-Temporal Nonlinear Modeling of Gastric Myoelectrical Activity

The accomplishment of a complete digestive process of human stomach is regulated by a spatio-temporally-coordinated electric pattern called gastric myoelectrical activity (GMA). The normal patterns of GMA present temporal evolution from endogenous rhythmic oscillation to bursting of spikes associated with contractions, and also ordered spatial propagation of the oscillating waves. The abnormal patterns of GMA have been observed in temporal dysrhythmia, such as tachygastria, bradygastria and arrhythmia, and in spatial propagation failure, such as retrograde propagation and uncoupling. Different GMA patterns are associated with different gastric symptoms and there exist some nonlinear mechanisms to govern the formation and dynamic evolution of these patterns. However, these mechanisms are so complex that few of them are known by medical observations. The aim of this study is to explore these mechanisms by spatio-temporal modeling of GMA. The single-cell model simulating the formation process of slow waves and spikes, the multi-cell model simulating the propagation process of GMA and the extracellular model simulating the formation of bipolar recordings are presented.

[The efficacy analysis of interferon combined with imatinib in chronic myelogenous leukemia patients with ABL kinase domain mutations]

To retrospectively analyze the efficacy of interferon plus imatinib (IM) in patients with chronic-phase chronic myelogenous leukemia(CML-CP)and ABL kinase domain mutations. The mutation rates of ABL kinase region in patients with Sokal score low, medium and high risk CML-CP were statistically significant (6.25%, 9.42% and 47.06%, P<0.05). The response rates of interferon plus IM versus second-generation TKI in CML-CP with non-T315I ABL kinase domain mutations were comparable (61.11% vs 65.52%, P>0.05). When CML-CP patients with ABL kinase domain mutations were resistant to TKI or not accessible to second-generation TKI, interferon plus IM can be an alternative choice.

A novel speech-processing strategy incorporating tonal information for cochlear implants

Good performance in cochlear implant users depends in large part on the ability of a speech processor to effectively decompose speech signals into multiple channels of narrow-band electrical pulses for stimulation of the auditory nerve. Speech processors that extract only envelopes of the narrow-band signals (e.g., the continuous interleaved sampling (CIS) processor) may not provide sufficient information to encode the tonal cues in languages such as Chinese. To improve the performance in cochlear implant users who speak tonal language, we proposed and developed a novel speech-processing strategy, which extracted both the envelopes of the narrow-band signals and the fundamental frequency (F0) of the speech signal, and used them to modulate both the amplitude and the frequency of the electrical pulses delivered to stimulation electrodes. We developed an algorithm to extract the fundatmental frequency and identified the general patterns of pitch variations of four typical tones in Chinese speech. The effectiveness of the extraction algorithm was verified with an artificial neural network that recognized the tonal patterns from the extracted F0 information. We then compared the novel strategy with the envelope-extraction CIS strategy in human subjects with normal hearing. The novel strategy produced significant improvement in perception of Chinese tones, phrases, and sentences. This novel processor with dynamic modulation of both frequency and amplitude is encouraging for the design of a cochlear implant device for sensorineurally deaf patients who speak tonal languages.

[Determination of +Gz tolerance end-point by steady state visual evoked potential]

OBJECTIVE

To study the possibility of applying steady-state visual evoked potential (SSVEP) to detect the end-point of +Gz tolerance.

METHOD

When a subject was exposed to +Gz acceleration on a human centrifuge, the SSVEP signals (evoked by LED lamps triggered by 8 Hz pulse train) were recorded. The characters of SSVEP in frequency domain were extracted by adaptive filtering, and a modified T2circ statistic was used to determine the visual obstruct objectively.

RESULT

SSVEP had strong relationship with visual obstruct of the subjects during +Gz exposure.

CONCLUSION

SSVEP might be used as an objective criterion for determination of end-point of +Gz tolerance and an index of the degree of symptoms as well. But, multi-parameter method seemed still necessary to get reliable estimations.

Spatio-temporal nonlinear modeling of gastric myoelectrical activity

The accomplishment of a complete digestive process of human stomach is regulated by a spatio-temporally-coordinated electric pattern called gastric myoelectrical activity (GMA). The normal patterns of GMA present temporal evolution from endogenous rhythmic oscillation to bursting of spikes associated with contractions, and also ordered spatial propagation of the oscillating waves. The abnormal patterns of GMA have been observed in temporal dysrhythmia, such as tachygastria, bradygastria and arrhythmia, and in spatial propagation failure, such as retrograde propagation and uncoupling. Different GMA patterns are associated with different gastric symptoms and there exist some nonlinear mechanisms to govern the formation and dynamic evolution of these patterns. However, these mechanisms are so complex that few of them are known by medical observations. The aim of this study is to explore these mechanisms by spatio-temporal modeling of GMA. The single-cell model simulating the formation process of slow waves and spikes, the multi-cell model simulating the propagation process of GMA and the extracellular model simulating the formation of bipolar recordings are presented.