The neural mechanisms of perceptual decision making

Perceptual decision making (PDM) involves choosing one option among several on the basis of sensory evidence and is a highly adaptive mechanism for organisms to successfully interact with their environments. Such a choice requires integrating and interpreting sensory information for the purpose of guiding subsequent behavior (e.g., seeing a ball move rightward and veering accordingly to catch it). Typical single-unit recording studies examining PDM utilize simple sensorimotor tasks (e.g., a macaque views a noisy array of dots moving in one of two possible directions and deploys a saccade in the chosen - and presumably, perceived - direction) in order to parse various aspects of PDM. With the aid of mathematical models, these experiments have found that the activity of individual neurons involved in motor response generation comprises perceptual decisions, and that PDM can be formalized as an accumulation of sensory evidence towards a particular choice (as represented by an increase in neuronal firing rate) until some threshold is reached. Explaining the mechanisms of PDM at the level of neural populations and linking ensemble patterns of neural activity to perception, however, still remains unclear. With a combination of visual psychophysics, neuroimaging, and modeling, I present a set of studies that examines the neural correlates subserving PDM in human cortex (Experiment 1), clarifies the relationship between sensory representations in visual cortex and perceptual performance (Experiment 2), and tests the behavioral predictions derived from single-cell recordings (Experiment 3). These findings both challenge and confirm some of the previous neurophysiological work: Experiment 1 provides evidence of a neural mechanism of PDM not based purely on oculomotor regions, Experiment 2 shows that the optimality of activation patterns in visual cortex predicts task performance, and Experiment 3 illustrates that attentional manipulations influence perception in a manner consistent with the enhancement and suppression of distinct neural populations predicted from single-unit recordings. Furthermore, these studies demonstrate the utility of model-based cognitive neuroscience in quantifying psychological processes of interest for each individual and relating between-subject differences with corresponding brain measurement

Spectral Amplitude-Coding Optical CDMA System Using Mach-Zehnder Interferometers

In this paper, we propose a family of newly constructed codes to suppress the phase-induced intensity noise (PIIN) in spectral amplitude-coding (SAC) optical code division multiple access (OCDMA) systems. These new codes are derived from modified prime codes and their cross-correlation is not larger than one. We also present a novel SAC-OCDMA system employing the new codes together with Mach-Zehnder interferometers to eliminate the multi-user interference (MUI). Compared with the systems employing modified quadratic congruence codes (MQC codes), numerical results verify that our proposed system can more effectively suppress the PIIN and eliminate MUI. Hence, the number of simultaneously users and total transmission rate increases significantly.SCIEI紙本電子

The analysis of agency cost within state-ownership structures of the airline industries: Direct state-owned companies and indirect state-owned companies (ownership via sovereign wealth fund)

Objectives This study is conducted to investigate the significance of the two ownership structures, namely direct state-ownership and indirect state-ownership, in the context of airline companies. The research also extends to examine the underlying reason for the implied distinctions. Agency cost is the main measure used to compare the efficiency between the two ownership structures. This paper also seeks to test out the relative importance of each characteristic in relation to agency cost. Summary The findings supported two hypotheses: (H2) indirect state-owned enterprise has lower agency cost due to greater use of debt and (H4) indirect state-owned enterprise has lower agency cost due to the international diversification. The findings, however, rejected the two remaining hypotheses: (H1) indirect state-owned enterprise has lower agency cost due to greater transparency pressures and (H3) indirect state-owned enterprise has higher agency cost due to the international diversification. Conclusions In the comparison between indirect and direct state-owned airline companies, it is evident that indirect state-owned airlines performed more efficiently than direct state-owned airlines

Drainage in urban water environment

Good drainage improves the waterways from the place of origin is released. However, improper waste management system in drainage could lead pollution in streams and rivers. In the case study in Batu Pahat town, there are several issues arise on drainage system. One of the main problems that caused the drainage get clogged is food waste from restaurants especially in closed drainage. There are several effects that are encountered if the waste management in the drainage system is poor. The effects could happen on human, flora and fauna, and environment. The aim of this chapter will identify the method of practices that has been used for cleaning the drainage. Responsibilities of local authorities in cleaning the drains at Batu Pahat will be explained. The best management practise to overcome the drainage pollution issues will be highlighted

Optimal stimulation duration of tens in the management of osteoarthritic knee pain

Objective: This study examined the optimal stimulation duration of transcutaneous electrical nerve stimulation (TENS) for relieving osteoarthritic knee pain and the duration (as measured by half-life) of post-stimulation analgesia. Subjects: Thirty-eight patients received either: (i) 20 minutes (TENS20); (ii) 40 minutes (TENS40); (iii) 60 minutes (TENS60) of TENS; or (iv) 60 minutes of placebo TENS (TENSPL) 5 days a week for 2 weeks. Methods: A visual analogue scale recorded the magnitude and pain relief period for up to 10 hours after stimulation. Results: By Day10, a significantly greater cumulative reduction in the visual analogue scale scores was found in the TENS40 (83.40%) and TENS60 (68.37%) groups than in the TENS20 (54.59%) and TENSPL (6.14%) groups (p 3 0.000), such a group difference was maintained in the 2-week followup session (p 3 0.000). In terms of the duration of post-stimulation analgesia period, the duration for the TENS40 (256 minutes) and TENS60 (258 minutes) groups was more prolonged than in the other 2 groups (TENS20 = 168 minutes, TENSPL = 35 minutes) by Day10 (p 3 0.000). However, the TENS40 group produced the longest pain relief period by the follow-up session. Conclusion: 40 minutes is the optimal treatment duration of TENS, in terms of both the magnitude (VAS scores) of pain reduction and the duration of post-stimulation analgesia for knee osetoarthritis.<br /

Noncoherent Spatial/Spectral Optical CDMA System With Two-Dimensional Perfect Difference Codes

[[abstract]]A dynamic optical code division multiple access (DOCDMA) communication system is proposed for high-bandwidth communication systems. An implementation of the system is proposed based on a fast tunable optical filter (TOF) in each encoder and decoder. This technique actively modulates the central wavelength of a TOF according to a functional code at the transmitter during the bit period before the transmission of the data. The system is modeled and analyzed taking into account multiple access interference (MAI), thermal noise, and phase-induced intensity noise (PIIN). The performance of this system is compared to that of a spectral amplitude coding system that uses either a Hadamard code or a modified quadratic congruence (MQC) code. The results show that the proposed DOCDMA system reduces the PIIN effect on the performance of the system and improves the bit error rate (BER) performance at a large number of users. Furthermore, it is found that when the effective power is large enough, the MAI becomes the main factor that limits system performance, whereas when the effective power is relatively low, both thermal noise and PIIN become the main limiting factors with thermal noise having the main influence.[[notice]]補正完畢[[incitationindex]]SCI[[incitationindex]]EI[[booktype]]紙本[[booktype]]電子

Bile acids cycle disruption in patients with nasopharyngeal carcinoma promotes the elevation of interleukin-10 secretion

Background: Unclear pathogenesis existed for nasopharyngeal carcinoma.Aims: to analyze the role of bile acids in the pathogenesis of nasopharyngeal carcinoma.Methods: 20 healthy volunteers and 20 patients with nasopharyngeal carcinoma were enrolled between January 1st, 2013 and December 31st, 2014. ESI-QTOF-MS analysis of serum was performed to find altered bile acids components. The biological function of changed bile acids was investigated using in vitro experiment.Results: Compared with healthy volunteers, the level of DCA and GDCA exhibited higher abundance in patients with nasopharyngeal carcinoma (p&lt;0.01). Furthermore, the biological function was investigated for the inhibition of DCA and GDCA towards the secretion of IL-10 by CD4+CD25- T cells. Both DCA and GDCA significantly inhibited the secretion of IL-10 by CD4+CD25- T cells. Furthermore, DCA+GDCA can show stronger inhibition towards the secretion of IL-10 than DCA and GDCA.Conclusion: The inhibition of IL-10 secretion by elevated DCA and GDCA components in nasopharyngeal carcinoma patients is the inducer for nasopharyngeal carcinoma.Key words: nasopharyngeal carcinoma, interleukin-10 (IL-10), pathogenesis, T cell, bile acids

Effectiveness of electroacupuncture and interferential electrotherapy in the management of frozen shoulder

Author name used in this publication: Gladys L. Y. Cheing2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe