The spatial distribution and temporal dynamics of brain regions activated during the perception of object and non-object patterns

Both animal and human studies suggest that the efficiency with which we are able to grasp objects is attributable to a repertoire of motor signals derived directly from vision. This is in general agreement with the long-held belief that the automatic generation of motor signals by the perception of objects is based on the actions they afford. In this study, we used magnetoencephalography (MEG) to determine the spatial distribution and temporal dynamics of brain regions activated during passive viewing of object and non-object targets that varied in the extent to which they afforded a grasping action. Synthetic Aperture Magnetometry (SAM) was used to localize task-related oscillatory power changes within specific frequency bands, and the time course of activity within given regions-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. Both single subject and group-averaged data on the spatial distribution of brain activity are presented. We show that: (i) significant reductions in 10-25 Hz activity within extrastriate cortex, occipito-temporal cortex, sensori-motor cortex and cerebellum were evident with passive viewing of both objects and non-objects; and (ii) reductions in oscillatory activity within the posterior part of the superior parietal cortex (area Ba7) were only evident with the perception of objects. Assuming that focal reductions in low-frequency oscillations (< 30 Hz) reflect areas of heightened neural activity, we conclude that: (i) activity within a network of brain areas, including the sensori-motor cortex, is not critically dependent on stimulus type and may reflect general changes in visual attention; and (ii) the posterior part of the superior parietal cortex, area Ba7, is activated preferentially by objects and may play a role in computations related to grasping. © 2006 Elsevier Inc. All rights reserved.

Perception of concurrent sentences with harmonic or frequency-shifted voiced excitation:performance of human listeners and of computational models based on autocorrelation

Keyword identification in one of two simultaneous sentences is improved when the sentences differ in F0, particularly when they are almost continuously voiced. Sentences of this kind were recorded, monotonised using PSOLA, and re-synthesised to give a range of harmonic ?F0s (0, 1, 3, and 10 semitones). They were additionally re-synthesised by LPC with the LPC residual frequency shifted by 25% of F0, to give excitation with inharmonic but regularly spaced components. Perceptual identification of frequency-shifted sentences showed a similar large improvement with nominal ?F0 as seen for harmonic sentences, although overall performance was about 10% poorer. We compared performance with that of two autocorrelation-based computational models comprising four stages: (i) peripheral frequency selectivity and half-wave rectification; (ii) within-channel periodicity extraction; (iii) identification of the two major peaks in the summary autocorrelation function (SACF); (iv) a template-based approach to speech recognition using dynamic time warping. One model sampled the correlogram at the target-F0 period and performed spectral matching; the other deselected channels dominated by the interferer and performed matching on the short-lag portion of the residual SACF. Both models reproduced the monotonic increase observed in human performance with increasing ?F0 for the harmonic stimuli, but not for the frequency-shifted stimuli. A revised version of the spectral-matching model, which groups patterns of periodicity that lie on a curve in the frequency-delay plane, showed a closer match to the perceptual data for frequency-shifted sentences. The results extend the range of phenomena originally attributed to harmonic processing to grouping by common spectral pattern.

Extrinsic factors in the perception of bistable motion stimuli

When viewing a drifting plaid stimulus, perceived motion alternates over time between coherent pattern motion and a transparent impression of the two component gratings. It is known that changing the intrinsic attributes of such patterns (e.g. speed, orientation and spatial frequency of components) can influence percept predominance. Here, we investigate the contribution of extrinsic factors to perception; specifically contextual motion and eye movements. In the first experiment, the percept most similar to the speed and direction of surround motion increased in dominance, implying a tuned integration process. This shift primarily involved an increase in dominance durations of the consistent percept. The second experiment measured eye movements under similar conditions. Saccades were not associated with perceptual transitions, though blink rate increased around the time of a switch. This indicates that saccades do not cause switches, yet saccades in a congruent direction might help to prolong a percept because i) more saccades were directionally congruent with the currently reported percept than expected by chance, and ii) when observers were asked to make deliberate eye movements along one motion axis, this increased percept reports in that direction. Overall, we find evidence that perception of bistable motion can be modulated by information from spatially adjacent regions, and changes to the retinal image caused by blinks and saccades.

The use of flow control devices to improve the flow pattern and throughput of sieve trays

Compared to packings trays are more cost effective column internals because they create a large interfacial area for mass transfer by the interaction of the vapour on the liquid. The tray supports a mass of froth or spray which on most trays (including the most widely used sieve trays) is not in any way controlled. The two important results of the gas/liquid interaction are the tray efficiency and the tray throughput or capacity. After many years of practical experience, both may be predicted by empirical correlations, despite the lack of understanding. It is known that the tray efficiency is in part determined by the liquid flow pattern and the throughput by the liquid froth height which in turn depends on the liquid hold-up and vapour velocity. This thesis describes experimental work on sieve trays in an air-water simulator, 2.44 m in diameter. The liquid flow pattern, for flow rates similar to those used in commercial scale distillation, was observed experimentally by direct observation; by water-cooling, to simulate mass transfer; use of potassium permanganate dye to observe areas of longer residence time; and by height of clear liquid measurements across the tray and in the downcomer using manometers. This work presents experiments designed to evaluate flow control devices proposed to improve the gas liquid interaction and hence improve the tray efficiency and throughput. These are (a) the use of intermediate weirs to redirect liquid to the sides of the tray so as to remove slow moving/stagnant liquid and (b) the use of vapour-directing slots designed to use the vapour to cause liquid to be directed towards the outlet weir thus reducing the liquid hold-up at a given rate i.e. increased throughput. This method also has the advantage of removing slow moving/stagnant liquid. In the experiments using intermediate weirs, which were placed in the centre of the tray. it was found that in general the effect of an intermediate weir depends on the depth of liquid downstream of the weir. If the weir is deeper than the downstream depth it will cause the upstream liquid to be deeper than the downstream liquid. If the weir is not as deep as deep as the downstream depth it may have little or no effect on the upstream depth. An intermediate weir placed at an angle to the direction of flow of liquid increases the liquid towards the sides of the tray without causing an increase in liquid hold-up/ froth height. The maximum proportion of liquid caused to flow sideways by the weir is between 5% and 10%. Experimental work using vapour-directing slots on a rectangular sieve tray has shown that the horizontal momentum that is imparted to the liquid is dependent upon the size of the slot. If too much momentum is transferred to the liquid it causes hydraulic jumps to occur at the mouth of the slot coupled with liquid being entrained, The use of slots also helps to eliminate the hydraulic gradient across sieve trays and provides a more uniform froth height on the tray. By comparing the results obtained of the tray and point efficiencies, it is shown that a slotted tray reduces both values by approximately 10%. This reduction is due to the fact that with a slotted tray the liquid has a reduced residence time Ion the tray coupled also with the fact that large size bubbles are passing through the slots. The effectiveness of using vapour-directing slots on a full circular tray was investigated by using dye to completely colour the biphase. The removal of the dye by clear liquid entering the tray was monitored using an overhead camera. Results obtained show that the slots are successful in their aim of reducing slow moving liquid from the sides of the tray, The net effect of this is an increase in tray efficiency. Measurements of slot vapour-velocity found it to be approximately equal to the hole velocity.

Studies on the behaviour of Reticulitermes santonensis (Feytaud) in laboratory colonies and its implications for some methods of termite control

An investigation of behavioural patterns that form a basis for termite control in the Australasian region was undertaken using laboratory colonies of the subterranean termite Reticulitermes santonensis (Feytaud). The study attempted to build a picture of the behavioural elements of individuals in a colony and based on this, trophallaxis, aggression and cannibalism were investigated in detail. Preliminary study of food transmission showed that 'workers' played a major role in the distribution of food. It was found, that among factors responsible for release of trophallactic behaviour the presence of 'right odour' between participants was important. It also appeared that the role taken by individuals depended on whether they were hungry or fully fed. Antennal palpation was shown by donors and acceptors alike and this seemed to be excitatory in function. Introduction of aliens into nests elicited aggression and these aliens were often killed. Factors eliciting aggression were investigated and colony odour was found to be important. Further investigations revealed that development of colony odour was governed by genetical and environmental mechanisms. Termite response to injury and death was also governed by odour. In the case of injury either the fresh haemolymph from the wound or some component of the haemolymph evoked cannibalism. Necrophagic behaviour was found to be released by fatty acids found in the corpses. Finally, the response of colonies to nestmates carrying arsenic trioxide was investigated. It was found that living and freshly dead arsenic-carrying nestmates were treated like normal nestmates, resulting in high initial mortality. However, poisoned cadavers soon became repellant and were buried thus preventing further spread of the poison to the rest of the colony. This suggested that complete control of subterranean termites by arsenic trioxide is unlikely to be fully effective, especially in those species which are capable of developing secondary reproductives from survivors and thus rebuilding the community.

Computer integrated manufacturing (CIM) and the principle of business control

In response to the increasing international competitiveness, many manufacturing businesses are rethinking their management strategies and philosophies towards achieving a computer integrated environment. The explosive growth in Advanced Manufacturing Technology (AMI) has resulted in the formation of functional "Islands of Automation" such as Computer Aided Design (CAD), Computer Aided Manufacturing (CAM), Computer Aided Process Planning (CAPP) and Manufacturing Resources Planning (MRPII). This has resulted in an environment which has focussed areas of excellence and poor overall efficiency, co-ordination and control. The main role of Computer Integrated Manufacturing (CIM) is to integrate these islands of automation and develop a totally integrated and controlled environment. However, the various perceptions of CIM, although developing, remain focussed on a very narrow integration scope and have consequently resulted in mere linked islands of automation with little improvement in overall co-ordination and control. This thesis, that is the research described within, develops and examines a more holistic view of CIM, which is based on the integration of various business elements. One particular business element, namely control, has been shown to have a multi-facetted and underpinning relationship with the CIM philosophy. This relationship impacts various CIM system design aspects including the CIM business analysis and modelling technique, the specification of systems integration requirements, the CIM system architectural form and the degree of business redesign. The research findings show that fundamental changes to CIM system design are required; these are incorporated in a generic CIM design methodology. The affect and influence of this holistic view of CIM on a manufacturing business has been evaluated through various industrial case study applications. Based on the evidence obtained, it has been concluded that this holistic, control based approach to CIM can provide a greatly improved means of achieving a totally integrated and controlled business environment. This generic CIM methodology will therefore make a significant contribution to the planning, modelling, design and development of future CIM systems.

Aspects of the design and operation of production control systems in manufacturing industry

Computerised production control developments have concentrated on Manufacturing Resources Planning (MRP II) systems. The literature suggests however, that despite the massive investment in hardware, software and management education, successful implementation of such systems in manufacturing industries has proved difficult. This thesis reviews the development of production planning and control systems, in particular, investigates the causes of failures in implementing MRP/MRP II systems in industrial environments and argues that the centralised and top-down planning structure, as well as the routine operational methodology of such systems, is inherently prone to failure. The thesis reviews the control benefits of cellular manufacturing systems but concludes that in more dynamic manufacturing environments, techniques such as Kanban are inappropriate. The basic shortcomings of MRP II systems are highlighted and a new enhanced operational methodology based on distributed planning and control principles is introduced. Distributed Manufacturing Resources Planning (DMRP), was developed as a capacity sensitive production planning and control solution for cellular manufacturing environments. The system utilises cell based, independently operated MRP II systems, integrated into a plant-wide control system through a Local Area Network. The potential benefits of adopting the system in industrial environments is discussed and the results of computer simulation experiments to compare the performance of the DMRP system against the conventional MRP II systems presented. DMRP methodology is shown to offer significant potential advantages which include ease of implementation, cost effectiveness, capacity sensitivity, shorter manufacturing lead times, lower working in progress levels and improved customer service.

Individual differences in the sensory perception of fats

Excessive consumption of dietary fat is acknowledged to be a widespread problem linked to a range of medical conditions. Despite this, little is known about the specific sensory appeal held by fats and no previous published research exists concerning human perception of non-textural taste qualities in fats. This research aimed to address whether a taste component can be found in sensory perception of pure fats. It also examined whether individual differences existed in human taste responses to fat, using both aggregated data analysis methods and multidimensional scaling. Results indicated that individuals were able to detect both the primary taste qualities of sweet, salty, sour and bitter in pure processed oils and reliably ascribe their own individually-generated taste labels, suggested that a taste component may be present in human responses to fat. Individual variation appeared to exist, both in the perception of given taste qualities and in perceived intensity and preferences. A number of factors were examined in relation to such individual differences in taste perception, including age, gender, genetic sensitivity to 6-n-propylthiouracil, body mass, dietary preferences and intake, dieting behaviours and restraint. Results revealed that, to varying extents, gender, age, sensitivity to 6-n-propylthiouracil, dietary preferences, habitual dietary intake and restraint all appeared to be related to individual variation in taste responses to fat. However, in general, these differences appeared to exist in the form of differing preferences and levels of intensity with which taste qualities detected in fat were perceived, as opposed to the perception of specific taste qualities being associated with given traits or states. Equally, each of these factors appeared to exert only a limited influence upon variation in sensory responses and thus the potential for using taste responses to fats as a marker for issues such as over-consumption, obesity or eating disorder is at present limited.

Cost effectiveness of production control systems

This thesis deals with the problems associated with the planning and control of production, with particular reference to a small aluminium die casting company. The main problem areas were identified as: (a) A need to be able to forecast the customers demands upon the company's facilities. (b) A need to produce a manufacturing programme in which the output of the foundry (or die casting section) was balanced with the available capacity in the machine shop. (c) The need to ensure that the resultant system enabled the company's operating budget to have a reasonable chance of being achieved. At the commencement of the research work the major customers were members of the automobile industry and had their own system of forecasting, from which they issued manufacturing schedules to their component suppliers, The errors in the forecast were analysed and the distributions noted. Using these distributions the customer's forecast was capable of being modified to enable his final demand to be met with a known degree of confidence. Before a manufacturing programme could be developed the actual manufacturing system had to be reviewed and it was found that as with many small companies there was a remarkable lack of formal control and written data. Relevant data with regards to the component and the manufacturing process had therefore to be collected and analysed. The foundry process was fixed but the secondary machining operations were analysed by a technique similar to Component Flow Analysis and as a result the machines were arranged in a series of flow lines. A system of manual production control was proposed and for comparison, a local computer bureau was approached and a system proposed incorporating the production of additional management information. These systems are compared and the relative merits discussed and a proposal made for implementation.

Oscillatory dynamics in the perception of pain investigated using magnetoencephalography

This thesis investigates changes in the oscillatory dynamics in key areas of the pain matrix during different modalities of pain. Gamma oscillations were seen in the primary somatosensory cortex in response to somatic electrical stimulation at painful and non-painful intensities. The strength of the gamma oscillations was found to relate to the intensity of the stimulus. Gamma oscillations were not seen during distal oesophageal electrical stimulation or the cold pressor test. Gamma oscillations were not seen in all participants during somatic electrical stimulation, however clear evoked responses from SI were seen in everyone. During a train of electrical pulses to the median nerve and the digit, a decrease in the frequency of the gamma oscillations was seen across the duration of the train. During a train of electrical stimuli to the median nerve and the digit, gamma oscillations were seen at ~20-100ms following stimulus onset and at frequencies between 30-100Hz. This gamma response was found to have a strong evoked component. Following a single electrical pulse to the digit, gamma oscillations were seen at 100-250ms and between 60-95Hz and were not temporally coincident with the main components of the evoked response. These results suggest that gamma oscillations may have an important role in encoding different aspects of sensory stimuli within their characteristics such as strength and frequency. These findings help to elucidate how somatic stimuli are processed within the cortex which in turn may be used to understand abnormal cases of somatosensory processing.

Autonomic response in the perception of disgust and happiness in depersonalization disorder

Patients with depersonalization disorder have shown attenuated responses to emotional unpleasant stimuli, hence supporting the view that depersonalization is characterised by a selective inhibition on the processing of unpleasant emotions. It was the purpose of this study to establish if autonomic responses to facial emotional expressions also show the same blunting effect. The skin conductance responses (SCRs) of 16 patients with chronic DSM-IV depersonalization disorder, 15 normal controls and 15 clinical controls with DSM-IV anxiety disorders were recorded in response to facial expressions of happiness and disgust. Patients with anxiety disorders were found to have greater autonomic responses than patients with depersonalization, in spite of the fact that both groups had similarly high levels of subjective anxiety as measured by anxiety scales. SCR to happy faces did not vary across groups. The findings of this study provide further support to the idea that patients with depersonalization have a selective impairment in the processing of threatening or unpleasant emotional stimuli.