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The right frontal eye field (rFEF) is associated with visual perception and eye movements. rFEF is activated during optokinetic nystagmus (OKN), a reflex that moves the eye in response to visual motion (optokinetic stimulation, OKS). It remains unclear whether rFEF plays causal perceptual and/or oculomotor roles during OKS and OKN. To test this, participants viewed a leftward-moving visual scene of vertical bars and judged whether a flashed dot was moving. Single pulses of transcranial magnetic stimulation (TMS) were applied to rFEF on half of trials. In half of blocks, to explore oculomotor control, participants performed an OKN in response to the OKS. rFEF TMS, during OKN, made participants more accurate on trials when the dot was still, and it slowed eye movements. In separate blocks, participants fixated during OKS. This not only controlled for eye movements but also allowed the use of EEG to explore the FEF’s role in visual motion discrimination. In these blocks, by contrast, leftward dot motion discrimination was impaired, associated with a disruption of the frontal-posterior balance in alpha-band oscillations. None of these effects occurred in a control site (M1) experiment. These results demonstrate multiple related yet dissociable causal roles of the right FEF during optokinetic stimulation.NEW & NOTEWORTHY This study demonstrates causal roles of the right frontal eye field (FEF) in motion discrimination and eye movement control during visual scene motion: previous work had only examined other stimuli and eye movements such as saccades. Using combined transcranial magnetic stimulation and EEG and a novel optokinetic stimulation motion-discrimination task, we find evidence for multiple related yet dissociable causal roles within the FEF: perceptual processing during optokinetic stimulation, generation of the optokinetic nystagmus, and the maintenance of alpha oscillations.

Self‐motion perception is a key aspect of higher vestibular processing, suggested to rely upon hemispheric lateralization and alpha‐band oscillations. The first aim of this study was to test for any lateralization in the EEG alpha band during the illusory sense of self‐movement (vection) induced by large optic flow stimuli. Visual stimuli flickered at alpha frequency (approx. 10 Hz) in order to produce steady state visually evoked potentials (SSVEP s), a robust EEG measure which allows probing the frequency‐specific response of the cortex. The first main result was that differential lateralization of the alpha SSVEP response was found during vection compared with a matched random motion control condition, supporting the idea of lateralization of visual–vestibular function. Additionally, this effect was frequency‐specific, not evident with lower frequency SSVEP s. The second aim of this study was to test for a causal role of the right hemisphere in producing this lateralization effect and to explore the possibility of selectively modulating the SSVEP response. Transcranial alternating current stimulation (tACS ) was applied over the right hemisphere simultaneously with SSVEP recording, using a novel artefact removal strategy for combined tACS ‐EEG . The second main result was that tACS enhanced SSVEP amplitudes, and the effect of tACS was not confined to the right hemisphere. Subsequent control experiments showed the effect of tACS requires the flicker frequency and tACS frequency to be closely matched and tACS to be of sufficient intensity. Combined tACS ‐SSVEP s are a promising method for future investigation into the role of neural oscillations and for optimizing tACS .

The intraparietal sulcus within the dorsal right posterior parietal cortex is associated with spatial orientation and attention in relation to egocentric reference frames, such as left or right hemifield. It remains unclear whether it plays a causal role in the human in the roll plane (i.e. when visual stimuli are tilted clockwise or anticlockwise) which this is an important aspect of egocentric visual processing with clinical relevance in vestibular disorders. The subjective visual vertical (SVV) task measures the deviation between an individual's subjective vertical perception and the veridical vertical, involves the integration of visual, and vestibular information, and relies on a distributed network of multisensory regions that shows right lateralization and inter-areal inhibition. This study used combined TMS-EEG to investigate the role of the human dorsal parietal cortex in verticality perception using the SVV task in darkness. Participants were sorted according to their baseline bias at this task i.e. those with either a slight counterclockwise versus clockwise bias when judging a line to be truly vertical. Right parietal TMS facilitated verticality perception, reducing the difference between groups. ERPs suggested that the behavioral TMS effect occurred through normalizing individual SVV biases, evident frontally and late in the trial, and which was abolished after right parietal TMS. Effects were site and task specific, shown with a homologous left hemisphere control, and a landmark task performed on the same stimuli. These results support a right lateralization of visual-vestibular cognition and a distinct representation of the roll plane for egocentric processing in dorsal parietal cortex.

This study investigates the causal contribution of the left frontopolar cortex (FPC) to the processing of violated expectations from learned target–distractor spatial contingencies during visual search. The experiment consisted of two phases: learning and test. Participants searched for targets presented either among repeated or nonrepeated target–distractor configurations. Prior research showed that repeated encounters of identically arranged displays lead to memory about these arrays, which then can come to guide search (contextual cueing effect). The crucial manipulation was a change of the target location, in a nevertheless constant distractor layout, at the transition from learning to test. In addition to this change, we applied repetitive transcranial magnetic stimulation (rTMS) over the left lateral FPC, over a posterior control site, or no rTMS at all (baseline; between-group manipulation) to see how FPC rTMS influences the ability of observers to adapt context-based memories acquired in the training phase. The learning phase showed expedited search in repeated relative to nonrepeated displays, with this context-based facilitation being comparable across all experimental groups. For the test phase, the recovery of cueing was critically dependent on the stimulation site: Although there was evidence of context adaptation toward the end of the experiment in the occipital and no-rTMS conditions, observers with FPC rTMS showed no evidence of relearning at all after target location changes. This finding shows that FPC plays an important role in the regulation of prediction errors in statistical context learning, thus contributing to an update of the spatial target–distractor contingencies after target position changes in learned spatial arrays.

It is unclear how the brain reaches the correct balance between temporal and spatial processing necessary to perceive motion across space. Here, we tested whether visual motion area V5/MT + plays a causal role in Ternus illusion. Ternus displays can be perceived as showing either group motion or element motion and are empirically useful for dissociating temporal and spatial grouping across visual fields. Online single-pulse TMS was applied to observers during the presentation of Ternus displays, either within or across hemifields, over left V5/MT + or, respectively, a control site in the left somatosensory cortex, or an additional ‘Sham’ control condition. In the cross-hemifields condition, observers perceived more element motion with TMS over left V5/MT + than in either control condition. By contrast, in the within-hemifield condition, observers reported more group motion after left V5/MT + TMS. Our findings demonstrate a causal role of left V5/MT+ in the spatio-temporal grouping of Ternus apparent motion, and in maintaining the balance of spatio-temporal processing both within and across individual hemifields.

As we move through our environment, our visual system is presented with optic flow, a potentially important cue for perception, navigation and postural control. How does the brain anticipate the optic flow that arises as a consequence of our own movement? Converging evidence suggests that stimuli are processed differently by the brain if occurring as a consequence of self-initiated actions, compared to when externally generated. However, this has mainly been demonstrated with auditory stimuli. It is not clear how this occurs with optic flow. We measured behavioural, neurophysiological and head motion responses of 29 healthy participants to radially expanding, vection-inducing optic flow stimuli, simulating forward transitional motion, which were either initiated by the participant’s own button-press (“self-initiated flow”) or by the computer (“passive flow”). Self-initiation led to a prominent and left-lateralized inhibition of the flow-evoked posterior event-related alpha desynchronization (ERD), and a stabilisation of postural responses. Neither effect was present in control button-press-only trials, without optic flow. Additionally, self-initiation also produced a large event-related potential (ERP) negativity between 130–170 ms after optic flow onset. Furthermore, participants’ visual induced motion sickness (VIMS) and vection intensity ratings correlated positively across the group – although many participants felt vection in the absence of any VIMS, none reported the opposite combination. Finally, we found that the simple act of making a button press leads to a detectable head movement even when using a chin rest. Taken together, our results indicate that the visual system is capable of predicting optic flow when self-initiated, to affect behaviour.

PurposeTo investigate the inter-reader agreement for grading of retinal alterations in age-related macular degeneration (AMD) using a reading center setting.MethodsIn this cross-sectional case series, spectral domain optical coherence tomography (OCT, Topcon 3D OCT, Tokyo, Japan) scans of 112 eyes of 112 patients with neovascular AMD (56 treatment-naive, 56 after three anti-vascular endothelial growth factor injections) were analyzed by four independent readers. Imaging features specific for AMD were annotated using a novel custom-built annotation platform. Dice score, Bland-Altman plots, coefficients of repeatability (CR), coefficients of variation (CV), and intraclass correlation coefficients (ICC) were assessed.ResultsLoss of ellipsoid zone, pigment epithelium detachment, subretinal fluid, and Drusen were the most abundant features in our cohort. The features subretinal fluid, intraretinal fluid, hypertransmission, descent of the outer plexiform layer, and pigment epithelium detachment showed highest inter-reader agreement, while detection and measures of loss of ellipsoid zone and retinal pigment epithelium were more variable. The agreement on the size and location of the respective annotation was more consistent throughout all features.ConclusionsThe inter-reader agreement depended on the respective OCT-based feature. A selection of reliable features might provide suitable surrogate markers for disease progression and possible treatment effects focusing on different disease stages.Translational RelevanceThis might give opportunities to a more time- and cost-effective patient assessment and improved decision-making as well as have implications for clinical trials and training machine learning algorithms.

Inhibitory interactions between the visual and motor systems are robustly found during the transient stimulation of either system. However, it is unknown how such interactions operate if both systems are continuously and simultaneously activated. To test this, we engaged the visual-oculomotor system in 14 right-handers with a large moving striped pattern that elicits characteristic eye movement responses, the optokinetic nystagmus (OKN). We also engaged the motor system with dynamic handgrip exercise simultaneous to OKN. We hypothesised that central versus occipital EEG upper-alpha (10-12 Hz) synchronisation would reflect systems-level inhibition between visual and motor processes. Optokinetic responses were recorded with eye tracking, and gripping force measured with dynamometry. First, when exploring whether continuous visual activation inhibits motor activity, we found that OKN increased alpha synchronisation over central electrodes, in line with classic findings of motor downregulation to transient visual stimuli. We found further evidence for the visual inhibition of motor-cortical activity, by comparing between visual conditions: increasing visual input, from closed eyes, to eye opening, to visual stimulation, produced progressively greater motor synchronisation into the inhibitory upper-alpha band. Second, we tested for the opposite interaction, that is, effects of motor engagement over ongoing visual and oculomotor processes. Behaviourally, left hand-grip exercise accelerated the ongoing OKN, increasing slow phase velocity. Electrophysiologically, performing this repetitive motor task with either hand interfered the occipital alpha desynchronization that OKN normally induces on EEG. These results support that mutual visual and motor inhibitory interactions persist during their simultaneous engagement, and show their effects on eye movements.Key pointsIncreasing levels of visual activation produced increasingly stronger signs of cortical inhibition.Hand motor activation interfered with visual cortical activation during visual stimulation.Hand motor activation altered oculomotor responses.Ongoing visual-motor interactions were reflected by the EEG alpha band.EEG can be reliably assessed during nystagmus.

Inhibitory control is an important executive function that is necessary to suppress premature actions and to block interference from irrelevant stimuli. Current experimental studies and models highlight proactive and reactive mechanisms and claim several cortical and subcortical structures to be involved in response inhibition. However, the involved structures, network mechanisms and the behavioral relevance of the underlying neural activity remain debated. We report cortical EEG and invasive subthalamic local field potential recordings from a fully implanted sensing neurostimulator in Parkinson's patients during a stimulus- and response conflict task with and without deep brain stimulation (DBS). DBS made reaction times faster overall while leaving the effects of conflict intact: this lack of any effect on conflict may have been inherent to our task encouraging a high level of proactive inhibition. Drift diffusion modelling hints that DBS influences decision thresholds and drift rates are modulated by stimulus conflict. Both cortical EEG and subthalamic (STN) LFP oscillations reflected reaction times (RT). With these results, we provide a different interpretation of previously conflict-related oscillations in the STN and suggest that the STN implements a general task-specific decision threshold. The timecourse and topography of subthalamic-cortical oscillatory connectivity suggest the involvement of motor, frontal midline and posterior regions in a larger network with complementary functionality, oscillatory mechanisms and structures. While beta oscillations are functionally associated with motor cortical-subthalamic connectivity, low frequency oscillations reveal a subthalamic-frontal-posterior network. With our results, we suggest that proactive as well as reactive mechanisms and structures are involved in implementing a task-related dynamic inhibitory signal. We propose that motor and executive control networks with complementary oscillatory mechanisms are tonically active, react to stimuli and release inhibition at the response when uncertainty is resolved and return to their default state afterwards.

Given recent controversies about the limitations of using unnatural experimental contexts and overly reductionist approaches, it is timely to illustrate how combined TMS-EEG can inform the study of normal cognition. The effect of TMS to visual cortices has been characterized with EEG, and related to specific aspects of normal perceptual cognition. Occipital regions act as one of multiple key trigger nodes in an attentional network that can function to some extent independently of awareness, and with a neural signature dissociable from that recorded after stimulating other nodes. The neural networks underlying cognition can be studied by comparing the neural and mental effects of stimulating different nodes. TMS pulses trigger a highly specific cascade of neural events and accompanying cognitive processes. This approach enables exploring how component processes aggregate together to give rise to perceptual cognition. The causal-mechanistic approach can provide evidence supporting particular psychological theories.

BackgroundThe ability to record brain activity in humans during movement, and in real world environments, is an important step towards understanding cognition. Electroencephalography (EEG) is well suited to mobile applications but suffers from the problem of artefacts introduced into the signal during movement. Steady state visually evoked potentials (SSVEPs) give an excellent signal-to-noise ratio and averaging a sufficient number of trials will eventually remove any noise not phase locked to the visual flicker.New MethodHere we present a method for producing SSVEPs of real world environments using modified LCD shutter glasses, which are commonly used for 3D TV, by adapting the lens to flicker at neurophysiologically relevant frequencies, in this case the alpha band. Participants viewed a room whilst standing and walking. Either the left or right side of the room was illuminated, to test if it is possible to recover the resulting SSVEPs when walking, as well as to probe the effect of walking on neural activity. Additionally, by using a signal generator to produce “simulated SSVEPs” on the scalp we can demonstrate that this method is able to accurately recover evoked neural responses during walking.ResultsThe amplitude of SSVEPs over right parietal cortex was reduced by walking. This finding is in line with converging evidence that visual-vestibular integration involves cortical lateralization with the right hemisphere being dominant in right handers. Furthermore, the waveform and phase of the SSVEPs is highly preserved between walking and standing, but was nevertheless sensitive to whether visual stimulation was presented to the left or right visual hemifield.ConclusionsThis method allows probing neural responses at a wide range of frequencies, during natural movements within real environments.

Strong stimuli may capture attention automatically, suggesting that attentional selection is determined primarily by physical stimulus properties. The mechanisms underlying capture remain controversial, in particular, whether feedforward subcortical processes are its main source. Also, it remains unclear whether only physical stimulus properties determine capture strength. Here, we demonstrate strong capture in the absence of feedforward input to subcortical structures such as the superior colliculus, by using transcranial magnetic stimulation (TMS) over occipital visual cortex as an attention cue. This implies that the feedforward sweep through subcortex is not necessary for capture to occur but rather provides an additional source of capture. Furthermore, seen cues captured attention more strongly than (physically identical) unseen cues, suggesting that the momentary state of the nervous system modulates attentional selection. In summary, we demonstrate the existence of several sources of attentional capture, and that both physical stimulus properties and the state of the nervous system influence capture.

Cystic fibrosis (CF) affects over 9,000 people in the UK and limits life expectancy. CF patients are susceptible to lung infections, most commonly Pseudomonas aeruginosa. Once infection is established, patients require lifetime treatment using nebulised antibiotics. Newer dry powder formulations of antibiotics may reduce treatment burden and improve compliance.Our objective was to evaluate the cost effectiveness of (i) colistimethate sodium dry powder for inhalation (DPI) and (ii) tobramycin DPI versus nebulised tobramycin for the treatment of chronic P. aeruginosa lung infection in patients with CF from the perspective of the National Health Service (NHS) and Personal Social Services (PSS).We developed a state transition model based on transitions between three strata of lung function measured in terms of forced expiratory volume in 1 second (FEV1) % predicted. Additional health states representing post-lung transplantation and dead are also modelled. The model structure was informed by systematic reviews of evidence concerning the plausibility of potential relationships between intermediate endpoints and final outcomes. The model assumes that treatment impacts on FEV1 trajectory, which manifest as changes in health-related quality of life. No survival benefit is assumed due to the absence of robust quantifiable evidence. Model parameters were informed by patient-level and aggregate data from two randomised controlled trials together with the best available evidence from the literature. Resource use and costs associated with drug acquisition, the management of exacerbations and reduced nebuliser maintenance were drawn from reference sources and expert opinion. Costs were valued at 2011/2012 prices. Costs and health outcomes were discounted at a rate of 3.5 %. Simple and probabilistic sensitivity analyses were undertaken, including additional analyses of Patient Access Scheme (PAS) price discounts offered by the manufacturers of both DPI products.Colistimethate sodium DPI is expected to produce fewer quality-adjusted life-years (QALYs) than nebulised tobramycin. Based on its list price, colistimethate sodium DPI is expected to be dominated by nebulised tobramycin. When the PAS is incorporated, the incremental cost-effectiveness ratio (ICER) for colistimethate sodium DPI versus nebulised tobramycin is expected to be approximately £288,600 saved per QALY lost. Based on its current list price, the ICER for tobramycin DPI versus nebulised tobramycin is expected to be approximately £124,000 per QALY gained. When the proposed PAS is included, tobramycin DPI is expected to dominate nebulised tobramycin.Under their list prices, neither DPI product is likely to represent good value for money for the NHS given current cost-effectiveness thresholds. The PAS discounts have a significant impact upon the economic attractiveness of both DPI products compared against nebulised tobramycin. The clinical effectiveness and cost effectiveness of the DPIs against other nebulised antibiotics, such as aztreonam and inhaled colistimethate sodium, remains unclear.

Abstract: C.J. Taylor's memoir begins with a brief account of his formative undergraduate years at Simon Fraser University in the 1960s and describes some of his experiences as a graduate student at Carleton University in the 1970s and 1980s. Much of the memoir is devoted to his years working as a Parks Canada historian between 1974 and 2009. He became interested in the history of the historic sites program while writing agenda papers and plaque texts for the Historic Sites and Monuments Board of Canada. After moving to Calgary in 1989 he became involved in national parks history, primarily the mountain parks of Banff, Jasper, Waterton Lakes, Yoho, and Kootenay, but also the new west coast park of Gwaii Haanas.

Visually induced vection is the illusory sensation of self-motion caused by visual stimuli (such as a dot cloud) that emulate what is seen when an agent moves through space. The sufficient stimulus parameters to generate vection are unknown, but elucidating this is of interest in the study of higher (cognitive) neurological disorders where the relationship between visual and vestibular processing is disturbed. Here, we selectively eliminate that radial motion angle from vection displays and show that vection is still present, although weaker than during normal optic flow, and that vection strength was strikingly variable across individuals.

Action selection requires choosing one of all the possible conflicting action plans that are available. There is currently a debate as to whether the dorsal medial frontal cortex (dMFC) merely detects or actively resolves response conflict. We used combined on-line transcranial magnetic stimulation and electroencephalographic recording (TMS–EEG) to test whether human dMFC plays a critical causal role in conflict resolution, and whether the mechanism for such a function is via interactions with primary motor cortex. In an Eriksen flanker task, subjects discriminated the direction of the centermost arrow in an array of five, responding with the left or right hand. The lateralized readiness potential (LRP), a measure of relative levels of activity in left and right motor cortices, was also recorded. Reaction times and error rates were higher on incongruent than congruent trials, and incongruent trials produced a positive LRP deflection reflecting initial partial activation of the incorrect response. On one-half of trials, repetitive TMS was applied to left dMFC starting 100 ms before visual stimulus onset and ending 100 ms afterward. TMS disrupted performance by selectively increasing error rates on contralateral (right hand) incongruent trials. TMS also only modulated the LRP on incongruent trials, causing an increased positive deflection (associated with preparation of the incorrect response) starting 180 ms after visual stimulus onset. TMS of a control site did not interfere with behavior or motor cortical activity. dMFC has a direct causal role in resolving conflict during action selection, and the mechanism involves the top–down modulation of primary motor cortical activity.

A key problem in reinforcement learning is how an animal is able to learn a sequence of movements when the reward signal only occurs at the end of the sequence. We describe how a hierarchical dynamical model of motor function is able to solve the problem of delayed reward in learning movement sequences using associative (Hebbian) learning. At the lowest level, the motor system encodes simple movements or primitives, while at higher levels the system encodes sequences of primitives. During training, the network is able to learn a high level motor program composed of a specific temporal sequence of motor primitives. The network is able to achieve this despite the fact that the reward signal, which indicates whether or not the desired motor program has been performed correctly, is received only at the end of each trial during learning. Use of a continuous attractor network in the architecture enables the network to generate the motor outputs required to produce the continuous movements necessary to implement the motor sequence.

Probing brain functions by brain stimulation while simultaneously recording brain activity allows addressing major issues in cognitive neuroscience. We review recent studies where electroencephalography (EEG) has been combined with transcranial magnetic stimulation (TMS) in order to investigate possible neuronal substrates of visual perception and attention. TMS-EEG has been used to study both pre-stimulus brain activity patterns that affect upcoming perception, and also the stimulus-evoked and task-related inter-regional interactions within the extended visual-attentional network from which attention and perception emerge. Local processes in visual areas have been probed by directly stimulating occipital cortex while monitoring EEG activity and perception. Interactions within the attention network have been probed by concurrently stimulating frontal or parietal areas. The use of tasks manipulating implicit and explicit memory has revealed in addition a role for attentional processes in memory. Taken together, these studies helped to reveal that visual selection relies on spontaneous intrinsic activity in visual cortex prior to the incoming stimulus, their control by attention, and post-stimulus processes incorporating a re-entrant bias from frontal and parietal areas that depends on the task.

During priming of pop-out, performance at discriminating a pop-out feature target in visual search is affected by whether the target on the previous trial was defined by the same feature as on the upcoming trial. Recent studies suggest that priming of pop-out relies on attentional processes. With the use of simultaneous, combined transcranial magnetic stimulation and event-related potential recording (TMS-ERP), we tested for any critical role of the right angular gyrus (rANG) and left and right frontal eye fields (FEFs)—key attentional sites—in modulating both performance and the ERPs evoked by such visual events. Intertrial TMS trains were applied while participants discriminated the orientation of a color pop-out element in a visual search array. rANG TMS disrupted priming of pop-out, reducing reaction time costs on switch trials and speeding responses when the color of the pop-out target switched. rANG TMS caused a negativity in the ERP elicited in response to the visual stimulus array, starting 210 ms after stimulus onset. Both behavioral and ERP effects were apparent only after rANG TMS, on switch trials, and when the target in the visual search array was presented in the left visual field, with no effects after left or right FEF TMS. These results provide evidence for an attentional reorienting mechanism, which originates in the rANG and is modulated by the implicit memory of the previous trial. The rANG plays a causal role on switch trials during priming of pop-out by interacting with visual processing, particularly in the ipsilateral hemisphere representing the contralateral hemifield.

Ramp Metering (RM) utilises traffic lights at the on-ramp entrances to limit access to the main carriageway of the motorway, in order to maintain flow close to capacity. In comparison to linear design, adaptive or predictive control systems can offer improved performance, albeit with the disadvantage of increased complexity, which can be prohibitive in the context of RM. By contrast, the present article develops a state dependent parameter (SDP) approach to traffic modelling and an associated non-linear pole assignment RM algorithm that is relatively straightforward to implement. Although the SDP model describes occupancy, its parameters are functionally dependent on other variables in the system, such as average velocity. In this manner, SDP models capture the time varying and non-linear dynamics of motorway flows but can, nonetheless, be estimated off-line. The paper illustrates the approach using telemetered measurements from near Southampton in the UK. Algebraic solutions to the control problem are similarly derived off-line and evaluated on-line using a macroscopic simulation model.

To investigate how we orient our spatial attention, previous studies have recorded neural activity while participants are instructed where to attend. Here we contrast this classical instructed attention condition with a novel condition in which the focus of voluntary attention is not specified by the experimenter but rather is freely chosen by the participant. Central cues prompted fixating participants either to choose which of two peripheral spatial locations to covertly attend or formed an instruction. Either type of cueing initiated selective attention demonstrated behaviorally by enhanced performance at a visual detection task in comparison to a separate divided attention condition. We used functional magnetic resonance imaging to measure which areas were more active during choice than instruction. Choosing where to attend activated a large cluster of medial frontal cortical regions similar to those that have been previously implicated in the free selection of overt action. We then addressed a potential confound in contrasting choice with instruction: participants may remember their behavior more when choosing. In a separate block, and interleaved with choice trials, “memory” trials were introduced in which participants were instructed to remember where they had attended on the previous trial. The presupplementary eye fields and lateral frontal eye fields were specialized for choice-guided attentional orienting over and above any memory confound. This evidence suggests a common mechanism may underlie free selection, whether for covert attention or overt saccades.

This paper describes the automation of a vibro-lance for ground improvement on a construction site. Here, a vibrating probe is lowered into the ground and penetrates downwards by means of a two-arm excavator, compacting the surrounding soil. The control system is straightforward to install on a conventional, hydraulically controlled excavator, such as the one utilised for the field tests reported in the paper. The new system supports the operator by automatically maintaining the verticality of the probe, increasing the speed of operation by a factor of three, whilst also yielding improved accuracy and, therefore, a potential increase in tool life. In particular, the research demonstrates the successful design and implementation of Proportional-Integral-Plus (PIP) control systems for joint control on-site. To the authors' knowledge, this represents the first operational use of automation for vibro-lance ground compaction.

This paper considers proportional-integral-plus (PIP) control of non-linear systems defined by state-dependent parameter models, with particular emphasis on three practical demonstrators: a microclimate test chamber, a 1/5th-scale laboratory representation of an intelligent excavator, and a full-scale (commercial) vibrolance system used for ground improvement on a construction site. In each case, the system is represented using a quasi-linear state-dependent parameter (SDP) model structure, in which the parameters are functionally dependent on other variables in the system. The approach yields novel SDP-PIP control algorithms with improved performance and robustness in comparison with conventional linear PIP control. In particular, the new approach better handles the large disturbances and other non-linearities typical in the application areas considered.

When humans perform two tasks simultaneously, responses to the second task are increasingly delayed as the interval between the two tasks decreases (psychological refractory period). This delay of the second task is thought to reflect a central processing limitation at the response selection stage. However, the neural mechanisms underlying this central processing limitation remain unclear. Using transcranial magnetic stimulation (TMS), we examined the role of the dorsal medial frontal cortex (dMFC) in a dual-task paradigm in which participants performed an auditory task 1 and a visual task 2. We found that dMFC TMS, relative to control conditions, reduced the psychological refractory period for task 2 processing, whereas we observed no dMFC TMS effects on task 1 processing. This suggests a causal role of the dMFC in coordinating response selection processes at the central bottleneck.

The objective of this paper is to develop non-linear proportional-integral-plus (PIP) control algorithms for regulating ventilation rate in mechanically ventilated agricultural buildings. State-dependent parameter (SDP) models are developed for an environmental test chamber, representing a section of a livestock building or glasshouse. Here, the system is modelled using the quasi-linear SDP model structure in which the parameters are functionally dependent on other variables in the system. The model is subsequently utilised to develop a new approach to control system design, based on non-linear PIP pole assignment, with a discrete-time Smith Predictor to handle the sampled time delays. Implementation results for the test chamber demonstrate improved control of ventilation rate, with a faster response to disturbances in comparison with both linear and conventional (linearised) scheduled PIP control. The approach has application to a wide class of other non-linear systems, as demonstrated by simulation examples.

Transcranial magnetic stimulation (TMS) is one of the most recent techniques to have been used in investigations of the parietal cortex but already a number of studies have employed it as a tool in investigations of attentional and sensorimotor processes in the human parietal cortices. The high temporal resolution of TMS has proved to be a particular strength of the technique and the experiments have led to hypotheses about when circumscribed regions of parietal cortex are critical for specific attentional and sensorimotor processes. A consistent theme that runs through many reports is that of a critical contribution of parietal areas when attention or movements are re-directed and representations for attention or action must be updated.

Microsensors have been fabricated consisting of TiO/sub 2/ and SnO/sub 2/ sensing films prepared by chemical vapor deposition (CVD) on microelectromechanical systems array platforms. Response measurements from these devices to the chemical warfare (CW) agents GA (tabun), GB (sarin), and HD (sulfur mustard) at concentrations between 5 nmol/mol (ppb) and 200 ppb in dry air, as well as to CW agent simulants CEES (chloroethyl ethyl sulfide) and DFP (diisopropyl fluorophosphate) between 250 and 3000 ppb, are reported. The microsensors exhibit excellent signal-to-noise and reproducibility. The temperature of each sensor element is independently controlled by embedded microheaters that drive both the CVD process (375/spl deg/C) and sensor operation at elevated temperatures (325/spl deg/C-475/spl deg/C). The concentration-dependent analyte response magnitude is sensitive to conditions under which the sensing films are grown. Sensor stability studies confirm little signal degradation during 14 h of operation. Use of pulsed (200 ms) temperature-programmed sensing over a broad temperature range (20/spl deg/C-480/spl deg/C) enhances analyte selectivity, since the resulting signal trace patterns contain primarily kinetic information that is unique for each agent tested.

This paper is concerned with proportional-integral-plus (PIP) control of ventilation rate in mechanically ventilated agricultural buildings. The PIP controller can be interpreted as a logical extension of conventional proportional-integral/proportional-integral-derivative (PI/PID) controllers, but with inherent model-based predictive control action. In particular, the paper considers the design of an optimal, scheduled gain PIP algorithm for a 22 m3 forced ventilation test chamber at the Katholieke Universiteit Leuven. Such a PIP approach proves more robust to pressure disturbances than an equivalent PID design and constitutes a preliminary step towards the development of the complete micro-climate controller.

Polycrystalline cubic boron nitride (PcBN) cutting tools are used for the machining of ferrous alloys at high speeds and temperatures where the use of diamond is precluded due to graphitisation. To accurately predict the life of these tool materials it is necessary to understand inter alia the deformation and relevant mechanisms that occur at the temperatures and pressures associated with cutting. This paper uses Vickers indentation as a means of assessing the role of cBN content, binder phase and cBN grain size on the mechanical properties of a number of polycrystalline cubic boron nitride materials. It will be shown that as experimental temperatures increase, a change in deformation mechanism occurs in the tool materials, confirming that the indentation method is useful in the identification of such changes.

The pancreas secretes a bicarbonate-rich fluid containing digestive enzymes via the ampulla of Vater into the duodenum. Defective secretion leads to maldigestion of fat and protein with increased faecal losses. Cystic fibrosis (CF) is the major cause of pancreatic exocrine failure in childhood, whereas pancreatic insufficiency in adults is commonly associated with chronic pancreatitis and alcohol ingestion. In cystic fibrosis, pancreatic function correlates with genotype; pancreatic-sufficient (PS) patients have a milder course of respiratory disease, improved survival and lower mean sweat chloride concentrations than those with pancreatic insufficiency. Recent observations suggest that mutant CF alleles are over-represented in patients with chronic pancreatitis. Few show evidence of sino-pulmonary disease or high sweat electrolyte concentrations.

Question Transcranial alternating current stimulation (tACS) has until now mostly been administered as a sinusoidal wave. As tACS is a relatively new technique there is a huge parameter space of unexplored possibilities which may prove superior or complimentary to the traditional sinusoidal waveform. Evidence from animal models suggests that the gradient and direction of an electric current are important factors for the subsequent neural firing rate; we compared positive and negative ramp sawtooth waves to test this using a novel method for simultaneous EEG and tACS. Methods An advantage of sawtooth waves is that the resulting artefact in the EEG recording is significantly simpler to remove than a sine wave as we can clearly see whether a residual artefact remains by the distinctive harmonics which can be seen when the cleaned data is viewed in the frequency domain. As such we can be sure the artefact has been successfully removed and are able to both observe alpha oscillations and recover event related potentials (ERPs) during stimulation. Results We have found that positive ramp sawtooth, but not negative ramp, significantly enhances alpha power during stimulation, demonstrating that current direction and gradient are important factors in tACS. In addition, we are able to gradually ramp up the intensity of the current and observe the point at which the tACS starts to modulate visually evoked ERPs. Conclusions The ability to observe on-going EEG activity is likely to significantly increase the usefulness of tACS in future research. A current limitation for all transcranial electrical stimulation is the inter-subject variation in effects due to differences in skull thickness, cerebrospinal fluid etc. Modulation of ERPs during tACS is an objective measure of the effect of the stimulation online, much like the motor evoked potential used for TMS research, which can be used to determine individualised current intensities and to test the effect of different electrode montages. This also opens up the possibility of real time feedback systems which can modulate neural oscillations. In addition, the fact that the effect of positive and negative ramp sawtooth waves is different, but the frequency, current density and skin sensations are identical, means this could serve as a better control condition in future studies.

Background Visual search performance is sensitive to changes in the environment. Attention is sensitive to trial history, in terms of both perception and response. Although the bases of these sensorimotor interactions remain unclear, both behaviorally and neurally, converging evidence from a variety of methods indicates that the right angular gyrus (rANG) may be important. Objective/hypothesis The present study tests whether the rANG plays a causal role in generating these inter-trial effects. Methods Participants performed a compound task for feature singleton targets. We applied rTMS over the rANG (or a control site, or no TMS) during the inter-trial interval and measured effects both on behavior and on neural activity using psychophysics and event-related potential (ERP) recording. Results rANG TMS during the inter-trial interval improved performance to the upcoming stimuli only when the target-defining dimension and the response-defining feature both repeated across successive trials. rANG TMS also increased the amplitude of the visual N1 component evoked by the upcoming stimuli. These effects did not occur after control TMS. Conclusion rANG plays a causal role in the formation of combined expectancies binding together stimulus- and response-characteristics of the previous trial to optimize visual search performance. This supports a visuomotor theory of parietal cortex and the dimension weighting account of attention. We suggest current models of inter-trial effects in visual search need to be expanded to include an interactive component representing both perceptual and motoric inter-trial expectancies, affecting the early analysis of stimulus features in the upcoming trial.

The paper develops an exact linearization by feedback approach for State Dependent Parameter (SDP), Proportional-Integral-Plus (PIP) control. The method is demonstrated using a simple automated belt driven by a DC motor equipped with a single board Reconfigurable Input-Output (sbRIO-9631) card, within a Field Programmable Gate Array (FPGA), and with a real time processor for control. The demonstrator is first modelled using a discrete-time SDP model structure, in which the parameters are functionally dependent on measured system states. An exact linearization step returns a linear model with unity coefficients, which is subsequently used to design a PIP control algorithm based on linear system design strategies, including pole assignment and optimal linear quadratic design. Preliminary experimental results demonstrate that the new approach yields an acceptable control performance for the nonlinear system.