Physical theory of organisation and consequent neural model of spatio-temporal pattern acquisition

A neurone model (the FORMON) is proposed which provides a mathematical explanation for a range of psychological phenomena and has potential in Artificial Intelligence applications. A general definition of organisation in terms of entropy and information is formulated. The concept of microcodes is introduced to describe the physical nature of organisation. Spatio-temporal pattern acquisition and processing functions attributable to individual neurones are reviewed. The criterion for self-organisation in a neurone is determined as the maximisation of mutual organisation. A feedback control system is proposed to satisfy this criterion and provide an integrated long-term memory of spatio-temporal pattern. This pattern acquisition system is shown to be applicable to dendritic pattern recognition and axonal pattern generation. Provision is also made for adaptation, short-term memory and operant learning. An electro-chemical model of transmission and processing of neural signals is outlined to provide the pattern acquisition functions of the Formon model. A transverse magnetic mode of electrotonic propagation is postulated in addition to the transverse electromagnetic mode. Configurations of the Formon are categorised in terms of possible pattern processing functions. Connective architectures are proposed as self-organising models of acquisitive semantic and syntactic networks.

Spatial and temporal disparities in aurally aided visual search

Research over the last decade has shown that auditorily cuing the location of visual targets reduces the time taken to locate and identify targets for both free-field and virtually presented sounds. The first study conducted for this thesis confirmed these findings over an extensive region of free-field space. However, the number of sound locations that are measured and stored in the data library of most 3-D audio spatial systems is limited, so that there is often a discrepancy in position between the cued and physical location of the target. Sampling limitations in the systems also produce temporal delays in which the stored data can be conveyed to operators. To investigate the effects of spatial and temporal disparities in audio cuing of visual search, and to provide evidence to alleviate concerns that psychological research lags behind the capabilities to design and implement synthetic interfaces, experiments were conducted to examine (a) the magnitude of spatial separation, and (b) the duration of temporal delay that intervened between auditory spatial cues and visual targets to alter response times to locate targets and discriminate their shape, relative to when the stimuli were spatially aligned, and temporally synchronised, respectively. Participants listened to free-field sound localisation cues that were presented with a single, highly visible target that could appear anywhere across 360° of azimuthal space on the vertical mid-line (spatial separation), or extended to 45° above and below the vertical mid-line (temporal delay). A vertical or horizontal spatial separation of 40° between the stimuli significantly increased response times, while separations of 30° or less did not reach significance. Response times were slowed at most target locations when auditory cues occurred 770 msecs prior to the appearance of targets, but not with similar durations of temporal delay (i.e., 440 msecs or less). When sounds followed the appearance of targets, the stimulus onset asynchrony that affected response times was dependent on target location, and ranged from 440 msecs at higher elevations and rearward of participants, to 1,100 msecs on the vertical mid-line. If targets appeared in the frontal field of view, no delay of acoustical stimulation affected performance. Finally, when conditions of spatial separation and temporal delay were combined, visual search times were degraded with a shorter stimulus onset asynchrony than when only the temporal relationship between the stimuli was varied, but responses to spatial separation were unaffected. The implications of the results for the development of synthetic audio spatial systems to aid visual search tasks was discussed.

The temporal price relationship between the stock index futures and the underlying stock index : evidence from Malaysia

The stock index futures was introduced in Malaysia in December 1995 with the launching of the futures contract on the Kuala Lumpur Stock Exchange Composite Index. Due to its recentness in the country, many issues pertaining to this equity derivatives instrument have not been explored. Thus, the development of stock index futures opens many opportunities for research in this area. This study examines the temporal relationship between the price of the Kuala Lumpur Stock Exchange Composite Index futures contract (FKLI) and its underlying stock index, the Kuala Lumpur Stock Exchange Composite Index (KLSE CI). The five-year period under study is split into three subperiods to observe the price co-movement pattern under different volatility levels. The study finds that futures market tends to lead the spot market by one day during the periods of stable market, and there is a mixed lead-lag relationship between the two markets during the period of highly volatile market.

Temporal causality and the dynamics of exports, human capital and real income in China

This article employs cointegration and error-correction modelling to test the causal relationship between real income, exports and human capital stock using data for China over the period 1960 to 1999. We find that real exports, human capital and real income are cointegrated when real exports is the dependent variable, but are not cointegrated when human capital or real income are the dependent variable. In the short-run we find evidence of bi-directional Granger causality between human capital and real exports, unidirectional Granger causality running from real income to human capital and neutrality between real exports and real income.

Temporal causality between human capital and real income in cointegrated VAR processes : empirical evidence from China, 1960-1999

This article examines the causal relationship between human capital and real income using data for China from 1960 to 1999. In the long run there is unidirectional Granger causality running from human capital to real income, while in the short run there is unidirectional Granger causality running from real income to human capital

Temporal causality and the dynamics of democracy, emigration and real income in Fiji

This study is the first to explore temporal causality between democracy, emigration and real income in Fiji within a multivariate cointegration model. We find three long run relationships between democracy, emigration and real income. In the long run there is evidence that migration and democracy Granger cause real GDP in Fiji; real GDP and democracy Granger cause migration from Fiji and that real GDP and migration Granger cause democracy in Fiji. In the short run we find unidirectional Granger causality running from migration to real GDP and from democracy to real GDP, but neutrality between democracy and migration in the short run. We also extend the analysis to examine the degree of exogeneity of the variables beyond the sample period through considering the decomposition of variance and impulse response functions.

Temporal expression of heat shock proteins 60 and 70 at lesion-prone sites during atherogenesis in ApoE-deficient mice

In the study, we investigate whether the expressions of heat shock protein (hsp)60 (a potential autoantigen) and the stress-inducible form of cytoprotector hsp70 are correlated with the development of atherosclerotic lesions in the aortic tree of apolipoprotein E–deficient (apoE^-/-) mice. The apoE^-/- mouse model is advantageous because the stress-inducible form of hsp70 is not constitutively expressed in mice, unlike primates; hence, tissues under stress can be clearly defined. Both mammalian hsps were detected newly expressed (before mononuclear cell infiltration) on aortic valves and endothelia at lesion-prone sites of 3-week-old apoE^-/- mice. In 8- and 20-week-old mice, they were strongly and heterogeneously expressed in early to advanced fibrofatty plaques, with levels correlating with lesion severity. Expression was markedly downregulated in advanced collagenous, acellular, calcified plaques of 40- and 69-week-old mice and was absent in control aortas of normocholesterolemic wild-type (apoE^+/+) mice. Western blot analysis of tissue homogenates confirmed the temporal expression of the hsps. Double immunostaining revealed that both hsps were expressed by lesional endothelial cells, macrophages, smooth muscle cells, and CD3⁺ T lymphocytes. This study provides evidence that hsp60 and hsp70 are temporally expressed on all major cell types in lesion-prone sites during atherogenesis, suggesting that few cells escape the toxic environment of the atherosclerotic plaque.

Spatial and temporal variation of infauna in an Australian estuary

Macroinvertebrates living within the sediments of the Hopkins River estuary were examined during 1997. Differences in the abundance and composition of faunal assemblages were identified between vegetated and unvegetated habitats and between the lower, middle and upper sections of the estuary. The numbers of taxa and individuals present were found to be similar to that of other periodically opened estuaries.

Depression in temporal lobe epilepsy surgery patients : an FDG-PET study

Summary: Purpose: Depression is common in temporal lobe epilepsy (TLE) and after temporal lobectomy, and its etiology is obscure. In nonepileptic depression (including depression associated with other neurologic disorders), a consistent PET imaging finding is frontal lobe hypometabolism. Many TLE patients have hypometabolism involving frontal regions. Thus in data available from routine clinical assessments in an epilepsy surgery unit, we tested the hypothesis that the pattern of hypometabolism, particularly in the frontal lobe, may be associated with the depression seen in patients with TLE and TLE surgery.

Methods: We studied 23 medically refractory TLE patients who underwent anterior temporal lobectomy and who had preoperative FDG-PET scanning. All patients had pre- and postoperative psychiatric assessment. By using statistical parametric mapping (SPM-99), patterns of hypometabolism were compared between patients who had a preoperative history of depression (n = 9) versus those who did not (n = 14) and between those in whom postoperative depression developed (n = 13) versus those in whom it did not (n = 10). A significant region of hypometabolism was set at p < 0.001 for a cluster of ≥20 contiguous voxels.

Results: Patients with a history of depression at any time preoperatively showed focal hypometabolism in ipsilateral orbitofrontal cortex compared with those who did not (t= 4.64; p < 0.001). Patients in whom depression developed postoperatively also showed hypometabolism in the ipsilateral orbitofrontal region (t= 5.10; p < 0.001).

Conclusions: Although this study is methodologically limited, and other explanations merit consideration, orbitofrontal cortex dysfunction, already implicated in the pathophysiology of nonepileptic depression, may also be relevant to the depression of TLE and temporal lobectomy.

The extent of resection of FDG-PET hypometabolism relates to outcome of temporal lobectomy

A significant minority of patients undergoing surgery for medically refractory non-lesional temporal lobe epilepsy (TLE) continue to have seizures, but the reasons for this are uncertain. Fluorodeoxyglucose (FDG) PET shows hypometabolism in a majority of patients with non-lesional TLE, even in the absence of hippocampal atrophy. We examined whether the extent of resection of the area of FDG-PET hypometabolism influenced outcome following surgery for non-lesional TLE. Twenty-six patients who underwent temporal lobectomy for medically refractory TLE with at least 12 months follow-up were studied. The preoperative FDG-PET was compared with 20 non-epileptic controls using SPM99 to identify regions of significant hypometabolism (P < 0.0005, cluster > 200). This image was then co-registered to the postoperative MRI scan. The volume of the FDG-PET hypometabolism that lay within the area of the resected temporal lobe was calculated. The volume of temporal lobe resected was also calculated. Patients with a good outcome had a greater proportion of the total FDG-PET hypometabolism volume resected than those with a poor outcome (24.1% versus 11.8%, P = 0.02). There was no significant difference between the groups in the volume of temporal lobe resected (P = 0.86). Multivariate regression demonstrated that the extent of resection of the hypometabolism significantly correlated with outcome (P = 0.03), independent of the presence of hippocampal sclerosis (P = 0.03) and total brain volume of hypometabolism (P = 0.45).

The extent of resection of the region of hypometabolism on the preoperative FDG-PET is predictive of outcome following surgery for non-lesional TLE. Strategies that tailor resection extent to regional hypometabolism may warrant further evaluation.

Modelling inter-temporal aid allocation : a new application with a focus on Papua New Guinea

This paper models the inter-temporal allocation of foreign development aid to Papua New Guinea (PNG). A formal theoretical model of aid allocation is developed, in which aid to any one country is determined jointly with aid to all other recipient countries. This is recognized in the econometric application of this model, which involves simultaneously modelling aid to a number of countries in addition to PNG. Results based on data for the period 1969–99 indicate that both recipient need and donor interest variables determine the amount of foreign aid to PNG and most other countries under consideration.