The cruciform model of striate generation of the early VEP, re-illustrated, not revoked: a reply to Ales et al. (2013)

Here we summarize the points raised in our dialog with Ales and colleagues on the cortical generators of the early visual evoked potential (VEP), and offer observations on the results of additional simulations that were run in response to our original comment. For small stimuli placed at locations in the upper and lower visual field for which the human VEP has been well characterized, simulated scalp projections of each of the visual areas V1, V2 and V3 invert in polarity. However, the empirically measured, earliest VEP component, "C1," matches the simulated V1 generators in terms of polarity and topography, but not the simulated V2 and V3 generators. We thus conclude that, 1) consistent with the title of Ales et al. (2010a), polarity inversion on its own is not a sufficient criterion for inferring neuroelectric sources in primary visual cortex; but 2) inconsistent with additional claims made in Ales et al. (2010a), the simulated topographies provide additional evidence for - not against - the tenet that the C1 component is generated in V1.

Exploiting individual primary visual cortex geometry to boost steady state visual evoked potentials

OBJECTIVE

The steady-state visual evoked potential (SSVEP) is an electroencephalographic response to flickering stimuli generated partly in primary visual area V1. The typical 'cruciform' geometry and retinotopic organization of V1 is such that certain neighboring visual regions project to neighboring cortical regions of opposite orientation. Here, we explored ways to exploit this organization in order to boost scalp SSVEP amplitude via oscillatory summation.

APPROACH

We manipulated flicker-phase offsets among angular segments of a large annular stimulus in three ways, and compared the resultant SSVEP power to a conventional condition with no temporal phase offsets. (1) We divided the annulus into standard octants for all subjects, and flickered upper horizontal octants with opposite temporal phase to the lower horizontal ones, and left vertical octants opposite to the right vertical ones; (2) we individually adjusted the boundaries between the eight contiguous segments of the standard octants condition to coincide with cruciform-consistent, early-latency topographical shifts in pattern-pulse multifocal visual-evoked potentials (PPMVEP) derived for each of 32 equal-sized segments; (3) we assigned phase offsets to stimulus segments following an automatic algorithm based on the relative amplitudes of vertically- and horizontally-oriented PPMVEP components.

MAIN RESULTS

The three flicker-phase manipulations resulted in a significant enhancement of normalized SSVEP power of (1) 202%, (2) 383%, and (3) 300%, respectively.

SIGNIFICANCE

We have thus demonstrated a means to obtain more reliable measures of visual evoked activity purely through consideration of cortical geometry. This principle stands to impact both basic and clinical research using SSVEPs.

Patient safety in vitreoretinal surgery: quality improvements following a patient safety reporting system

AIMS

Vitreoretinal (VR) surgery is complex. Most clinical conditions that VR surgeons manage have a high risk for blindness or severe visual impairment. Reporting of patient safety incidents (PSI) in VR surgery was introduced at the Moorfields Eye Hospital (MEH) in the 1990s. We examine the role of PSI reporting in making VR surgery safer at our institution.

METHODS

Qualitative review of PSIs from 1997 to 2009 at MEH, London, UK.

RESULTS

Over the 13-year study period, 38 789 VR procedures were undertaken and 579 VR PSIs occurring in theatre or inpatient were reported. Mean rate of PSI reporting was 1.49% (range 0.12-3.35). In comparison, the mean rate of PSI reporting over the same period across all National Health Service ophthalmology in England was 0.59% (range 0.36-0.49). Overall, 0.9% of VR PSI resulted in 'Severe' harm, 11.6% in 'Moderate' harm and 87.5% in 'No' or 'Low' harm. 15 (2.6%) of PSIs directly resulted in a change in clinical practice, 13 of which occurred in the first half of the study period. 12 (3.6%) critical incidents were violations of pre-existing protocols and guidelines, eight of which occurred in the second half of the study period. 61 (10.9%) of PSIs fell into nine main error subtypes that contributed to a change in practice. The most common were ocular hypotony (2.9%), medical device failure (2.8%) and delay in VR surgery (1.2%).

CONCLUSIONS

VR PSI reporting resulted in a change in clinical practice. Longitudinal analysis suggests an accompanying increase in patient safety.

Balancing risk in ophthalmic prescribing: assessing the safety of anti-VEGF therapies and the risks associated with unlicensed medicines

Vascular endothelial growth factor (VEGF) inhibitor medications such as ranibizumab, pegaptanib and bevacizumab are in use for the treatment of neovascular age-related macular degeneration (AMD) and other retinal conditions, although only ranibizumab and pegaptanib are approved for these conditions. In contrast, bevacizumab was developed for the intravenous systemic treatment of colorectal cancer and is not formulated for intravitreal use, but is commonly used off-label in ophthalmology. European Union legislation permits the use of drugs outside the terms of their licence ('off-label') only under certain circumstances, such as during clinical trials, compassionate/named patient use in the absence of a licensed alternative, emergency scenarios (e.g., pandemics) or at the discretion of a treating physician. In such cases, patients should be fully informed regarding their treatment and any potential risks involved. Off-label drug use can be an important tool to provide patients with treatment in cases of unmet medical need. However, the use of an unlicensed medicinal product, when a suitable licensed alternative is available, puts prescribing physicians at risk of liability if safety issues arise. Emerging clinical evidence suggests safety differences exist between ranibizumab and bevacizumab.

A supramodal accumulation-to-bound signal that determines perceptual decisions in humans

In theoretical accounts of perceptual decision-making, a decision variable integrates noisy sensory evidence and determines action through a boundary-crossing criterion. Signals bearing these very properties have been characterized in single neurons in monkeys, but have yet to be directly identified in humans. Using a gradual target detection task, we isolated a freely evolving decision variable signal in human subjects that exhibited every aspect of the dynamics observed in its single-neuron counterparts. This signal could be continuously tracked in parallel with fully dissociable sensory encoding and motor preparation signals, and could be systematically perturbed mid-flight during decision formation. Furthermore, we found that the signal was completely domain general: it exhibited the same decision-predictive dynamics regardless of sensory modality and stimulus features and tracked cumulative evidence even in the absence of overt action. These findings provide a uniquely clear view on the neural determinants of simple perceptual decisions in humans.

Adverse ophthalmic reaction in poppers users: case series of 'poppers maculopathy'

BACKGROUND

Poppers are a recreational substance of abuse belonging to the alkyl nitrite family of compounds. In the United Kingdom, where they are legal to purchase but illegal to sell for human consumption, 10% of the general population have tried them. They are considered low risk to physical and mental health. Two recent case series from France demonstrated foveal pathology in individuals associated with poppers use.

METHOD

A case series of seven patients presenting to four hospitals in the United Kingdom with visual impairment and maculopathy associated with inhalation of poppers.

RESULTS

All patients experienced visual symptoms associated with poppers use. The majority had impaired visual acuity, central scotomata, distortion, or phosphenes. Clinical signs on fundoscopy ranged from normal foveal appearance to yellow, dome-shaped lesions at the foveola. Spectral domain optical coherence tomography (SD-OCT) showed varying degrees of disruption of the presumed inner segment/outer segment (IS/OS) junction.

DISCUSSION

Although poppers have been in use for several decades, in 2007, following legislative changes, there was a change in the most commonly used compound from isobutyl nitrite to isopropyl nitrite. There were no reports of 'poppers maculopathy' before this. Poppers maculopathy may be missed if patients are not directly questioned about their use. The disruption or loss of the presumed IS/OS junction on SD-OCT are a characteristic feature. Further study of maculopathy in poppers users is now needed. Raising public awareness of the ocular risks associated with their use may be necessary.

Isolating early cortical generators of visual-evoked activity: a systems identification approach

The VESPA (visual-evoked spread spectrum analysis) method estimates the impulse response of the visual system using a continuously varying stimulus. It has been used recently to address both basic cognitive and neurophysiologic questions as well as those surrounding clinical populations. Although the components of the average VESPA response are highly reminiscent of the early components of the visual-evoked potential (VEP) when measured over midline occipital locations, the two responses are acquired in different ways and, thus, they cannot be regarded as being equivalent. To further characterize the relationship between the VESPA and the VEP and the generative mechanisms underlying them, we recorded EEG from 31 subjects in response to checkerboard-based VEP and VESPA stimuli. We found that, across subjects, the amplitudes of the VEP C1 component and the VESPA C1 component were highly correlated, whereas the VEP P1 and the VESPA P1 bore no statistical relationship. Furthermore, we found that C1 and P1 amplitudes were significantly correlated in the VESPA but not in the VEP. We believe these findings point to the presence of common generators underlying the VESPA C1 and the VEP C1. We argue further that the VESPA P1, in light of its strong relationship to the VESPA C1, likely reflects further activation of the same cortical generators. Given the lack of correlation between the VEP P1 and each of these three other components, it is likely that the underlying generators of this particular component are more varied and widespread, as suggested previously. We discuss the implications of these relationships for basic and clinical research using the VESPA and for the assessment of additive-evoked versus phase-reset contributions to the VEP.

Action on AMD. Optimising patient management: act now to ensure current and continual delivery of best possible patient care

In recent years, there have been significant advances in the clinical management of patients with wet age-related macular degeneration (wet AMD)—a rapidly progressing and potentially blinding degenerative eye disease. Wet AMD is responsible for more than half of registered severe sight impairment (blindness) in the United Kingdom, and patients who are being treated for wet AMD require frequent and long-term follow-up for treatment to be most effective. The clinical workload associated with the frequent follow-up required is substantial. Furthermore, as more new patients are diagnosed and the population continues to age, the patient population will continue to increase. It is thus vital that clinical services continue to adapt so that they can provide a fast and efficient service for patients with wet AMD. This Action on AMDdocument has been developed by eye health-care professionals and patient representatives, the Action on AMDgroup. It is intended to highlight the urgent and continuing need for change within wet AMD services. This document also serves as a guide for eye health-care professionals, NHS commissioners, and providers to present possible solutions for improving NHS retinal and macular services. Examples of good practice and service development are considered and can be drawn upon to help services meet the recommended quality of care and achieve best possible outcomes.

Penetrating eye injuries from writing instruments

PURPOSE

To consider the potential for ocular injury from writing implements by presenting four such cases, and to consider the incidence of such eye injuries from analysis of a national trauma database.

METHODS

The Home and Leisure Accident Surveillance System was searched for records of eye injuries from writing instruments to provide UK estimates of such injuries. Four patients with ocular penetrating injury from pens or pencils (especially when caused by children), and examined by the authors, are described which illustrate mechanisms of injury.

RESULTS

It is estimated that around 748 ocular pen injuries and 892 ocular pencil injuries of undetermined severity occurred annually in the UK during the database surveillance period 2000-2002. No eye injuries from swords, including toy swords and fencing foils, were reported.

CONCLUSION

Ocular perforation sometimes occur from writing instruments that are thrown in the community, especially by children. Implications for policy and prevention are discussed. Non-specialists should have a low threshold for referring patients with eye injuries if suspicious of ocular penetration, even where caused by everyday objects, such as writing instruments.

Teleophthalmology with optical coherence tomography imaging in community optometry. Evaluation of a quality improvement for macular patients

Purpose

To describe a quality improvement for referral of National Health Service patients with macular disorders from a community optometry setting in an urban area.

Methods

Service evaluation of teleophthalmology consultation based on spectral domain optical coherence tomography images acquired by the community optometrist and transmitted to hospital eye services.

Results

Fifty patients with suspected macular conditions were managed via telemedicine consultation over 1 year. Responses were provided by hospital eye service-based ophthalmologists to the community optometrist or patient within the next day in 48 cases (96%) and in 34 (68%) patients on the same day. In the consensus opinion of the optometrist and ophthalmologist, 33 (66%) patients required further “face-to-face” medical examination and were triaged on clinical urgency. Seventeen cases (34%) were managed in the community and are a potential cost improvement. Specialty trainees were supervised in telemedicine consultations.

Conclusion

Innovation and quality improvement were demonstrated in both optometry to ophthalmology referrals and in primary optometric care by use of telemedicine with spectral domain optical coherence tomography images. E-referral of spectral domain optical coherence tomography images assists triage of macular patients and swifter care of urgent cases. Teleophthalmology is also, in the authors’ opinion, a tool to improve interdisciplinary professional working with community optometrists. Implications for progress are discussed.

The N1 auditory evoked potential component as an endophenotype for schizophrenia: high-density electrical mapping in clinically unaffected first-degree relatives, first-episode, and chronic schizophrenia patients

The N1 component of the auditory evoked potential (AEP) is a robust and easily recorded metric of auditory sensory-perceptual processing. In patients with schizophrenia, a diminution in the amplitude of this component is a near-ubiquitous finding. A pair of recent studies has also shown this N1 deficit in first-degree relatives of schizophrenia probands, suggesting that the deficit may be linked to the underlying genetic risk of the disease rather than to the disease state itself. However, in both these studies, a significant proportion of the relatives had other psychiatric conditions. As such, although the N1 deficit represents an intriguing candidate endophenotype for schizophrenia, it remains to be shown whether it is present in a group of clinically unaffected first-degree relatives. In addition to testing first-degree relatives, we also sought to replicate the N1 deficit in a group of first-episode patients and in a group of chronic schizophrenia probands. Subject groups consisted of 35 patients with schizophrenia, 30 unaffected first-degree relatives, 13 first-episode patients, and 22 healthy controls. Subjects sat in a dimly lit room and listened to a series of simple 1,000-Hz tones, indicating with a button press whenever they heard a deviant tone (1,500 Hz; 17% probability), while the AEP was recorded from 72 scalp electrodes. Both chronic and first-episode patients showed clear N1 amplitude decrements relative to healthy control subjects. Crucially, unaffected first-degree relatives also showed a clear N1 deficit. This study provides further support for the proposal that the auditory N1 deficit in schizophrenia is linked to the underlying genetic risk of developing this disorder. In light of recent studies, these results point to the N1 deficit as an endophenotypic marker for schizophrenia. The potential future utility of this metric as one element of a multivariate endophenotype is discussed.

A review of safety incidents in England and Wales for vascular endothelial growth factor inhibitor medications

PURPOSE

To learn from patient safety incidents (PSIs) following recent introduction of vascular endothelial growth factor inhibitor medications (anti-VEGF) in ophthalmic care, as reported via a national incident reporting database.

METHODS

Thematic retrospective review of anti-VEGF medications PSIs as reported via clinical incident reporting methods in NHS care in England and Wales from 2003 to 2010, ascertained from database mining at the National Patient Safety Agency (NPSA).

RESULTS

In all, 166 relevant anti-VEGF incidents were reported. Reports have increased year on year from 2006. Incident severity as reported: 10 were reported as 'severe harm' and 23 as 'moderate harm'. The remainder were 'low' or 'no harm' events. The incident themes and/or causes found and by order of severity included: intra-ocular inflammation/endophthalmitis (n=16); treatment or follow-up delays (n=45); wrong medication (n=26); wrong eye/patient injection (n=17); missing records (n=12). Other problems included medication availability and refrigeration failures. We reflect on potential solutions for addressing the matters found. Systemic safety matters, stroke, subdural hemorrhage, and myocardial infarction (total n=3) followed anti-VEGF treatments.

CONCLUSION

Although infrequent, anti-VEGF medication PSIs or errors do occur and are thus a threat to quality. This review also provides supporting evidence to existing concerns and challenges surrounding age-related macular degeneration service pressures and provision. Lessons for improvement of care from a national incident reporting database for a frequently undertaken and recently introduced ophthalmic procedure were found. Suggestions are proposed for improving quality by reducing such problems based on analysis of such reports. Endophthalmitis reports following intra-vitreal injections suggest rigorous infection control measures are required.

The neurophysiology of human biological motion processing: a high-density electrical mapping study

The neural processing of biological motion (BM) is of profound experimental interest since it is often through the movement of another that we interpret their immediate intentions. Neuroimaging points to a specialized cortical network for processing biological motion. Here, high-density electrical mapping and source-analysis techniques were employed to interrogate the timing of information processing across this network. Participants viewed point-light-displays depicting standard body movements (e.g. jumping), while event-related potentials (ERPs) were recorded and compared to ERPs to scrambled motion control stimuli. In a pair of experiments, three major phases of BM-specific processing were identified: 1) The earliest phase of BM-sensitive modulation was characterized by a positive shift of the ERP between 100 and 200 ms after stimulus onset. This modulation was observed exclusively over the right hemisphere and source-analysis suggested a likely generator in close proximity to regions associated with general motion processing (KO/hMT). 2) The second phase of BM-sensitivity occurred from 200 to 350 ms, characterized by a robust negative-going ERP modulation over posterior middle temporal regions bilaterally. Source-analysis pointed to bilateral generators at or near the posterior superior temporal sulcus (STS). 3) A third phase of processing was evident only in our second experiment, where participants actively attended the BM aspect of the stimuli, and was manifest as a centro-parietal positive ERP deflection, likely related to later cognitive processes. These results point to very early sensory registration of biological motion, and highlight the interactive role of the posterior STS in analyzing the movements of other living organisms.

MRSA and cataract surgery - reflections for practice

INTRODUCTION

Postoperative bacterial endophthalmitis is a devastating complication of cataract surgery. Methicillin-resistant Staphylococcus aureus (MRSA) endophthalmitis is rare. Recent debate over MRSA screening in United Kingdom (UK) National Health Service (NHS) hospital services has implications for cataract patients and ophthalmology services.

AIMS

To discuss issues for clinical practice as based on reflective experience at a UK district general NHS hospital in relation to care of MRSA-positive cataract patients.

METHODS

Retrospective case series and reflective practice.

RESULTS

Three cases presented highlight practice points around cataract patients colonized with MRSA. Known or determined MRSA-colonized patients should be treated with anti-microbial agents at time of cataract surgery known to be active against MRSA. Preventative treatment with intracameral vancomycin or intravenous teicoplanin alongside appropriate topical treatments may be of merit. Importantly fluoroquinolones, often prescribed by cataract surgeons, may have a selective effect favoring the proliferation of MRSA.

CONCLUSION

MRSA screening may cause unnecessary delays in cataract care and may represent a patient safety concern in its own right. Patients colonized with MRSA may safely undergo cataract surgery provided there is no evidence of periorbital infection and provided appropriate infection control and antibiotic prophylaxis measures are used. The well-prepared cataract surgeon needs to be aware of developments in infection control and should liaise with local clinical microbiology colleagues in relation to bacterial resistance to antibiotics.

Prepare for conflict: EEG correlates of the anticipation of target competition during overt and covert shifts of visual attention

When preparing to make a saccadic eye movement in a cued direction, perception of stimuli at the target location is enhanced, just as it is when attention is covertly deployed there. Accordingly, the timing and anatomical sources of preparatory brain activity accompanying shifts of covert attention and saccade preparation tend to exhibit a large degree of overlap. However, there is evidence that preparatory processes are modulated by the foreknowledge of visual distractor competition during covert attention, and it is unknown whether eye movement preparation undergoes equivalent modulation. Here we examine preparatory processes in the electroencephalogram of human participants during four blocked versions of a spatial cueing task, requiring either covert detection or saccade execution, and either containing a distractor or not. As in previous work, a typical pattern of spatially selective occipital, parietal and frontal activity was seen in all task versions. However, whereas distractor presence called on an enhancement of spatially selective visual cortical modulation during covert attention, it instead called on increased activity over frontomedial oculomotor areas in the case of overt saccade preparation. We conclude that, although advance orienting signals may be similar in character during overt and covert conditions, the pattern by which these signals are modulated to ameliorate the behavioral costs of distractor competition is highly distinct, pointing to a degree of separability between the overt and covert systems.

Distraction index as a risk factor for osteoarthritis associated with hip dysplasia in four large dog breeds

OBJECTIVE

To determine if age, breed, gender, weight or distraction index (DI) influenced the risk of radiographic osteoarthritis (OA) of canine hip dysplasia (CHD) in four common dog breeds; the American bulldog, Bernese mountain dog, Newfoundland and standard poodle.

MATERIALS AND METHODS

This was a cross sectional prevalence study with 4349 dogs. Canine hips were evaluated using 3 radiographic projections: the hip-extended view, the compression view and the distraction view. The hip-extended view was examined for the presence of OA. The PennHIP distraction view was utilized to calculate the DI. For all breeds, a multiple logistic regression model incorporating age, weight, gender, and DI was created. For each breed, disease-susceptibility curves grouping dogs on the basis of age were constructed. Receiver-operating characteristic (ROC) curves were developed for each breed regardless of age.

RESULTS

For all breeds, DI was the most significant risk factor for the development of OA associated with CHD. Weight and age were also significant risk factors in all four breeds, but gender was not.

CLINICAL SIGNIFICANCE

Results from this study support previous findings, that irrespective of breed, the probability of radiographic OA increases with hip joint laxity as measured by the DI. Breed-specific differences in this relationship, however, warrant investigation of all breeds affected by CHD to determine inherent dependency of hip OA on joint laxity. Such findings guide veterinarians in helping dog breeders to make evidence-based breeding decisions and in informing dog owners to implement preventative treatments for CHD for dogs found to be at risk.

Smoking cessation support in community pharmacies: is the association of smoking and eye disease an additional tool to increase uptake?

Objective

Community pharmacists have a central role in provision of smoking-cessation support. Evidence is growing that tobacco smoking is associated with development and progression of several potentially blinding eye diseases. As part of an ongoing programme of raising awareness of this link, we investigated whether community pharmacists are aware of this association and incorporate relevant advice into their smoking-cessation guidance.

Setting

Two-thousand and eighty community pharmacists in north west England, UK.

Method

A postal self-completion questionnaire asked pharmacists about their current practice with regard to smoking habits of their clients. Data were extracted and entered onto a database for statistical analyses.

Key findings

The response rate was 50.5%; 685 (65.2%) pharmacists asked clients about smoking habits; the most common situation was when clients complained of respiratory symptoms. Of these pharmacists, 52.7% always/usually recommended that smokers should stop and 37.2% always/usually assessed motivation to succeed. Help provided by pharmacists included brief advice on smoking cessation, leaflets, more structured support, referral to smoking-cessation services, and nicotine replacement therapies. The most common reason why pharmacists did not ask about smoking was lack of time (83.1%); 52.0% were aware of the causal association of smoking with eye disease, and 19.8% of those who asked about smoking habits mentioned this association when discussing smoking cessation.

Conclusion

Our study shows that community pharmacists are actively involved in smoking cessation. Many pharmacists are aware of the causal association between smoking and eye disease, but few are actively counselling patients about the eye heath risks of smoking. Community pharmacists could include this information in their advice to clients who smoke, as an additional means to promote smoking cessation.

Toxoplasma retinochoroiditis in pregnancy: Using current evidence to inform management

Toxoplasma retinochoroiditis in pregnancy may create considerable patient anxiety and is a dilemma for the treating ophthalmologist. A case report highlighting this clinical issue is presented followed by a review of the literature. Consensus in relation to the management of toxoplasma retinochoroiditis in pregnancy is lacking and is discussed.

The strength of anticipatory spatial biasing predicts target discrimination at attended locations: a high-density EEG study

Cueing relevant spatial locations in advance of a visual target results in modulated processing of that target as a consequence of anticipatory attentional deployment, the neural signatures of which remain to be fully elucidated. A set of electrophysiological processes has been established as candidate markers of the invocation and maintenance of attentional bias in humans. These include spatially-selective event-related potential (ERP) components over the lateral parietal (around 200-300 ms post-cue), frontal (300-500 ms) and ventral visual (> 500 ms) cortex, as well as oscillatory amplitude changes in the alpha band (8-14 Hz). Here, we interrogated the roles played by these anticipatory processes in attentional orienting by testing for links with subsequent behavioral performance. We found that both target discriminability (d') and reaction times were significantly predicted on a trial-by-trial basis by lateralization of alpha-band amplitude in the 500 ms preceding the target, with improved speed and accuracy resulting from a greater relative decrease in alpha over the contralateral visual cortex. Reaction time was also predicted by a late posterior contralateral positivity in the broad-band ERP in the same time period, but this did not influence d'. In a further analysis we sought to identify the control signals involved in generating the anticipatory bias, by testing earlier broad-band ERP amplitude for covariation with alpha lateralization. We found that stronger alpha biasing was associated with a greater bilateral frontal positivity at approximately 390 ms but not with differential amplitude across hemispheres in any time period. Thus, during the establishment of an anticipatory spatial bias, while the expected target location is strongly encoded in lateralized activity in parietal and frontal areas, a distinct non-spatial control process seems to regulate the strength of the bias.

Visual sensory processing deficits in patients with bipolar disorder revealed through high-density electrical mapping

BACKGROUND

Etiological commonalities are apparent between bipolar disorder and schizophrenia. For example, it is becoming clear that both populations show similar electrophysiological deficits in the auditory domain. Recent studies have also shown robust visual sensory processing deficits in patients with schizophrenia using the event-related potential technique, but this has not been formally tested in those with bipolar disorder. Our goal here was to assess whether early visual sensory processing in patients with bipolar disorder, as indexed by decreased amplitude of the P1 component of the visual evoked potential (VEP), would show a similar deficit to that seen in those with schizophrenia. Since the P1 deficit has already been established as an endophenotype in schizophrenia, a finding of commonality between disorders would raise the possibility that it represents a measure of common genetic liability.

METHODS

We visually presented isolated-check stimuli to euthymic patients with a diagnosis of bipolar disorder and age-matched healthy controls within a simple go/no-go task and recorded VEPs using high-density (72-channel) electroencephalography.

RESULTS

The P1 VEP amplitude was substantially reduced in patients with bipolar disorder, with an effect size of f = 0.56 (large according to Cohen's criteria).

LIMITATIONS

Our sample size was relatively small and as such, did not allow for an examination of potential relations between the physiologic measures and clinical measures.

CONCLUSION

This reduction in P1 amplitude among patients with bipolar disorder represents a dysfunction in early visual processing that is highly similar to that found repeatedly in patients with schizophrenia and their healthy first-degree relatives. Since the P1 deficit has been related to susceptibility genes for schizophrenia, our results raise the possibility that the deficit may in fact be more broadly related to the development of psychosis and that it merits further investigation as a candidate endophenotype for bipolar disorder.

Absence of the 7-repeat variant of the DRD4 VNTR is associated with drifting sustained attention in children with ADHD but not in controls

Many genetic studies have demonstrated an association between the 7-repeat (7r) allele of a 48-base pair variable number of tandem repeats (VNTR) in exon 3 of the DRD4 gene and the phenotype of attention deficit hyperactivity disorder (ADHD). Previous studies have shown inconsistent associations between the 7r allele and neurocognitive performance in children with ADHD. We investigated the performance of 128 children with and without ADHD on the Fixed and Random versions of the Sustained Attention to Response Task (SART). We employed time-series analyses of reaction-time data to allow a fine-grained analysis of reaction time variability, a candidate endophenotype for ADHD. Children were grouped into either the 7r-present group (possessing at least one copy of the 7r allele) or the 7r-absent group. The ADHD group made significantly more commission errors and was significantly more variable in RT in terms of fast moment-to-moment variability than the control group, but no effect of genotype was found on these measures. Children with ADHD without the 7r allele made significantly more omission errors, were significantly more variable in the slow frequency domain and showed less sensitivity to the signal (d') than those children with ADHD the 7r and control children with or without the 7r. These results highlight the utility of time-series analyses of reaction time data for delineating the neuropsychological deficits associated with ADHD and the DRD4 VNTR. Absence of the 7-repeat allele in children with ADHD is associated with a neurocognitive profile of drifting sustained attention that gives rise to variable and inconsistent performance.

Visual sensory processing deficits in Schizophrenia and their relationship to disease state

CONTEXT

Visual Evoked Potential (VEP) abnormalities have been a fairly consistent finding in patients with schizophrenia, and it has been suggested that electrophysiological markers of early sensory processing may be useful as trait markers for the illness, and for development as potential diagnostic measures.

OBJECTIVE

Clear amplitude reductions in the occipital P1 component of the VEP (approximately 100 ms), have been repeatedly demonstrated in patients with schizophrenia. Here, we investigated whether the extent of this deficit was related to age, clinical symptoms, medication status and length of illness, in a large cohort of ethnically homogenous patients.

DESIGN, SETTING AND PARTICIPANTS

VEP responses to simple isolated-check stimuli were examined in 52 DSM-IV diagnosed patients with schizophrenia, and compared with responses from 26 healthy age-matched control subjects. Using high-density electrical scalp recordings, we assessed the integrity of the visual P1 component across the two groups. This study was conducted at St.Vincent's Psychiatric Hospital in Fairview, Dublin, Ireland.

RESULTS

Substantially reduced P1 amplitude was demonstrated in the patient group compared to controls. The deficit was not linked to age, length of illness or medication status. A small positive correlation, accounting for about 11% of the variance, was found between P1 amplitude and clinical symptoms scales (BPRS and SANS). In addition, we found that a slightly later (~110 ms) fronto-central component was relatively increased in the patient group, and was inversely correlated with the occipital P1 amplitude in the patients, but not in the healthy control subjects.

CONCLUSIONS

Our findings clearly demonstrate a deficit in early visual processing in patients with schizophrenia (with a large effect size; Cohen's d = 0.7) that is unrelated to chronicity. The results are consistent with recent findings showing that the P1 deficit is endophenotypic of the disorder and related to genetic risk factors rather than the disease process itself.

L-theanine and caffeine in combination affect human cognition as evidenced by oscillatory alpha-band activity and attention task performance

Recent neuropharmacological research has suggested that certain constituents of tea may have modulatory effects on brain state. The bulk of this research has focused on either L-theanine or caffeine ingested alone (mostly the latter) and has been limited to behavioral testing, subjective rating, or neurophysiological assessments during resting. Here, we investigated the effects of both L-theanine and caffeine, ingested separately or together, on behavioral and electrophysiological indices of tonic (background) and phasic (event-related) visuospatial attentional deployment. Subjects underwent 4 d of testing, ingesting either placebo, 100 mg of L-theanine, 50 mg of caffeine, or these treatments combined. The task involved cued shifts of attention to the left or right visual hemifield in anticipation of an imperative stimulus requiring discrimination. In addition to behavioral measures, we examined overall, tonic attentional focus as well as phasic, cue-dependent anticipatory attentional biasing, as indexed by scalp-recorded alpha-band (8-14 Hz) activity. We found an increase in hit rate and target discriminability (d') for the combined treatment relative to placebo, and an increase in d' but not hit rate for caffeine alone, whereas no effects were detected for L-theanine alone. Electrophysiological results did not show increased differential biasing in phasic alpha across hemifields but showed lower overall tonic alpha power in the combined treatment, similar to previous findings at a larger dosage of L-theanine alone. This may signify a more generalized tonic deployment of attentional resources to the visual modality and may underlie the facilitated behavioral performance on the combined ingestion of these 2 major constituents of tea.

Auditory scene analysis: the interaction of stimulation rate and frequency separation on pre-attentive grouping

Segregation of auditory inputs into meaningful acoustic groups is a key element of auditory scene analysis. Previously, we showed that two interwoven sets of tones differing widely along multiple feature dimensions (duration, pitch and location) were pre-attentively separated into different groups, and that tones separated in this manner did not elicit the mismatch negativity component with respect to each other. Grouping was studied with human subjects using a stimulus rate too slow to induce streaming. Here, we varied the separation of tone sequences along a single feature dimension, i.e. frequency. Frequency differences were either 24 Hz (small) or 1054 Hz (large). Two relatively slow stimulus rates were used (2.7 or 1 tone/s) to explicitly investigate grouping outside the so-called 'streaming effect', which requires rates of about 4 tones/s or faster. Two tones were presented in a quasi-random manner with embedded trains of one to four identical tones in a row. Deviants were defined as frequency switches after trains of four identical tones. Mismatch negativity was only elicited for small frequency switches at the slower stimulation rate. The data indicate that pre-attentive grouping of tones occurred when the frequency difference that separated them was large, regardless of stimulation rate. For small frequency differences, inputs were only grouped separately when the stimulation rate was relatively fast.

Isolating endogenous visuo-spatial attentional effects using the novel visual-evoked spread spectrum analysis (VESPA) technique

In natural visual environments, we use attention to select between relevant and irrelevant stimuli that are presented simultaneously. Our attention to objects in our visual field is largely controlled endogenously, but is also affected exogenously through the influence of novel stimuli and events. The study of endogenous and exogenous attention as separate mechanisms has been possible in behavioral and functional imaging studies, where multiple stimuli can be presented continuously and simultaneously. It has also been possible in electroencephalogram studies using the steady-state visual-evoked potential (SSVEP); however, it has not been possible in conventional event-related potential (ERP) studies, which are hampered by the need to present suddenly onsetting stimuli in isolation. This is unfortunate as the ERP technique allows for the analysis of human physiology with much greater temporal resolution than functional magnetic resonance imaging or the SSVEP. While ERP studies of endogenous attention have been widely reported, these experiments have a serious limitation in that the suddenly onsetting stimuli, used to elicit the ERP, inevitably have an exogenous, attention-grabbing effect. Recently we have shown that it is possible to derive separate event-related responses to concurrent, continuously presented stimuli using the VESPA (visual-evoked spread spectrum analysis) technique. In this study we employed an experimental paradigm based on this method, in which two pairs of diagonally opposite, non-contiguous disc-segment stimuli were presented, one pair to be ignored and the other to be attended. VESPA responses derived for each pair showed a strong modulation at 90–100 ms (during the visual P1 component), demonstrating the utility of the method for isolating endogenous visuo-spatial attention effects.

Spatial attention modulates initial afferent activity in human primary visual cortex

It is well established that spatially directed attention enhances visual perceptual processing. However, the earliest level at which processing can be affected remains unknown. To date, there has been no report of modulation of the earliest visual event-related potential component "C1" in humans, which indexes initial afference in primary visual cortex (V1). Thus it has been suggested that initial V1 activity is impenetrable, and that the earliest modulations occur in extrastriate cortex. However, the C1 is highly variable across individuals, to the extent that uniform measurement across a group may poorly reflect the dynamics of V1 activity. In the present study we employed an individualized mapping procedure to control for such variability. Parameters for optimal C1 measurement were determined in an independent, preliminary "probe" session and later applied in a follow-up session involving a spatial cueing task. In the spatial task, subjects were cued on each trial to direct attention toward 1 of 2 locations in anticipation of an imperative Gabor stimulus and were required to detect a region of lower luminance appearing within the Gabor pattern 30% of the time at the cued location only. Our data show robust spatial attentional enhancement of the C1, beginning as early as its point of onset (57 ms). Source analysis of the attentional modulations points to generation in striate cortex. This finding demonstrates that at the very moment that visual information first arrives in cortex, it is already being shaped by the brain's attentional biases.

Candida endophthalmitis: A critical diagnosis in the critically ill

Three cases of candida endophthalmitis complicating critical illness in young adult surgical patients with implications for safer practice are presented. We highlight how early ophthalmological examination can aid in the management of such critically ill patients. Clinicians need to be vigilant for the early diagnosis and aggressive treatment of hospital acquired opportunistic candida infection in at risk patients. Time may be of the essence as sight and life are at risk.

Glaucoma in the United States and europe: predicting costs and surgical rates based upon stage of disease

PURPOSE

Primary open-angle glaucoma is a significant health-economic burden in both the United States and Europe that is likely to increase. This study compared treatment patterns and cost among patients with primary open-angle glaucoma in these locations.

METHODS

Retrospective medical chart reviews were conducted in the United States (1990 to 2002) and Europe (1995 to 2003). A total sample of 151 US charts and 194 European charts was studied, and patients were assigned a baseline intraocular pressure (IOP) and baseline stage, using a 6-stage visual functional glaucoma staging algorithm. Resource utilization and direct costs were assessed by stage of disease using publicly available United States and European costs. Cox Proportional Hazards modeling were used to examine covariates predicting glaucoma surgery. Total cost was predicted, adjusting for covariates using Generalized Linear Models, with baseline stage as the independent variable.

RESULTS

Glaucoma surgery requirement was highly associated with baseline disease stage and IOP increase before surgery in the United States and somewhat associated with these factors in Europe. Within both locations, baseline IOP was highly associated with glaucoma surgery requirement. Controlling for covariates, patients at higher baseline stages incurred greater costs in the United States (P=0.0017) and Europe (P=0.0715). Surgery and medication were also highly predictive of increased cost (P<0.0001). Cost of care differed greatly between the European countries, with costs lowest in Italy.

CONCLUSIONS

Increases in annual cost were related to higher baseline IOP, higher baseline stage, medication, and surgery. Thus, significant potential savings and reductions in annual healthcare burden are possible if patients are diagnosed and treated at earlier stages of glaucoma.

Attitudes of community optometrists to smoking cessation: an untapped opportunity overlooked?

AIM

To assess community optometrists' attitudes and current behaviour regarding provision of smoking cessation advice in their practice.

METHODS

A self-completion postal questionnaire was sent to community optometrists in north-west England identified from the General Optical Council's practice lists.

RESULTS

Of 709 optometrists identified, 71.8% (509/709) returned the completed questionnaire. Few community optometrists routinely asked about smoking habits: only 6.2% (95% CI: 4.1-8.3) (n = 31) at new patient consultations, and 2.2% (95% CI: 0.9-3.5) (n=11) at follow-up visits. Reasons for optometrists not routinely providing smoking cessation advice included: not their role (35.4%, n=180), lack of time (22.0%, n=112) and forgetting to ask (21.4%, n=109). Overall 67.6% (95% CI: 63.5-71.7) (n=344) of community optometrists wanted to improve their knowledge of smoking and visual impairment with 56.2% (95% CI: 51.9-60.5) (n=286) requesting further training.

CONCLUSION

Despite low levels of current involvement, many optometrists were keen to receive training on smoking cessation topics. We suggest that there are untapped opportunities to develop brief interventions to promote smoking cessation services in community optometry settings.

Multisensory processing of naturalistic objects in motion: A high-density electrical mapping and source estimation study

In everyday life, we continuously and effortlessly integrate the multiple sensory inputs from objects in motion. For instance, the sound and the visual percept of vehicles in traffic provide us with complementary information about the location and motion of vehicles. Here, we used high-density electrical mapping and local auto-regressive average (LAURA) source estimation to study the integration of multisensory objects in motion as reflected in event-related potentials (ERPs). A randomized stream of naturalistic multisensory-audiovisual (AV), unisensory-auditory (A), and unisensory-visual (V) "splash" clips (i.e., a drop falling and hitting a water surface) was presented among non-naturalistic abstract motion stimuli. The visual clip onset preceded the "splash" onset by 100 ms for multisensory stimuli. For naturalistic objects early multisensory integration effects beginning 120-140 ms after sound onset were observed over posterior scalp, with distributed sources localized to occipital cortex, temporal lobule, insular, and medial frontal gyrus (MFG). These effects, together with longer latency interactions (210-250 and 300-350 ms) found in a widespread network of occipital, temporal, and frontal areas, suggest that naturalistic objects in motion are processed at multiple stages of multisensory integration. The pattern of integration effects differed considerably for non-naturalistic stimuli. Unlike naturalistic objects, no early interactions were found for non-naturalistic objects. The earliest integration effects for non-naturalistic stimuli were observed 210-250 ms after sound onset including large portions of the inferior parietal cortex (IPC). As such, there were clear differences in the cortical networks activated by multisensory motion stimuli as a consequence of the semantic relatedness (or lack thereof) of the constituent sensory elements.

‘Smoke gets in your eyes’: a research-informed professional education and advocacy programme

Smoking is associated with common sight-threatening eye conditions. We suspected that this link was little known and it might be a potent novel health promotional tool. We therefore developed a programme ultimately aiming to reduce the burden of eye disease attributable to smoking. The programme aims were to (1) raise awareness of the link between smoking and eye disease and advocate changes in relevant policies and (2) investigate and promote change in professional practice so that smokers are identified and routinely offered smoking cessation advice/support in eyecare settings. An inter-professional team developed a programme of research and education targeting policy-makers, healthcare professionals, the public and patients. We reviewed evidence about the causal link between smoking and eye disease, researched current awareness of the link, researched current practice of eyecare health professionals, produced health education materials and campaigned for policy changes. The series of projects was completed successfully, achieving media coverage, confirming the causal link between smoking and eye disease and demonstrating low awareness of this association. Healthcare leaders and policy-makers were engaged in our programme resulting in commitment, in principle, from the UK's Chief Medical Officer and the European Commission to consider including warning labels related to blindness on cigarette packets.

Teenagers' perceptions of blindness related to smoking: a novel message to a vulnerable group

BACKGROUND

Cigarette smoking often starts in teenage years. It is not known whether teenagers are aware of the association of smoking with eye disease and blindness.

AIM

To explore the knowledge of the link between smoking, and eye diseases and blindness, and the likely impact of this knowledge among teenagers in UK.

METHODS

A cross-sectional survey, using a structured interview of teenagers attending four organised social events, was conducted. Awareness and fear of blindness, and of three smoking-related diseases (lung cancer, heart disease and stroke) and a distractor condition (deafness) was investigated. The likelihood of smokers quitting on developing early signs of each condition was determined.

RESULTS

A 92% "opt in" response rate was achieved. Out of 260 teenagers (16-18 years), 15%, 27% and 81% believed that smoking caused stroke, heart disease and lung cancer, respectively. Only 5% believed smoking caused blindness. Subjects ranked their fear of each of the five conditions, scoring five for the most feared and one for the least feared. Subjects were significantly (p<0.01) more fearful (mean scores in brackets) of blindness (4.2) than of lung cancer (3.4), heart disease (2.3) and deafness (1.2). More teenagers (p<0.01) said they would stop smoking on developing early signs of blindness compared with early signs of lung or heart disease.

CONCLUSIONS

Awareness of the risk of blindness from smoking is low among teenagers, but fear of blindness may be more likely to motivate teenagers to stop smoking than fear of lung or heart disease. Teenagers should be made more aware of the ocular risks of cigarette smoking as a novel public health measure.

The role of cingulate cortex in the detection of errors with and without awareness: a high-density electrical mapping study

Error-processing research has demonstrated that the brain uses a specialized neural network to detect errors during task performance but the brain regions necessary for conscious awareness of an error are poorly understood. In the present study we show that two well-known error-related event-related potential (ERP) components, the error-related negativity (ERN) and error positivity (Pe) have a differential relationship with awareness during performance of a manual response inhibition task optimized to examine error awareness. While the ERN was unaffected by the participants' conscious experience of errors, the Pe was only seen when participants were aware of committing an error. Source localization of these components indicated that the ERN was generated by a caudal region of the anterior cingulate cortex (ACC) while the Pe was associated with contributions from a more anterior ACC region and the posterior cingulate-precuneus. Tonic EEG measures of cortical arousal were correlated with individual rates of error awareness and showed a specific relationship with the amplitude of the Pe. The latter finding is consistent with evidence that the Pe represents a P3-like facilitation of information processing modulated by subcortical arousal systems. Our data suggest that the ACC might participate in both preconscious and conscious error detection and that cortical arousal provides a necessary setting condition for error awareness. These findings may be particularly important in the context of clinical studies in which a proper understanding of self-monitoring deficits requires an explicit measurement of error awareness.

Dissociation in performance of children with ADHD and high-functioning autism on a task of sustained attention

Attention deficit hyperactivity disorder (ADHD) and autism are two neurodevelopmental disorders associated with prominent executive dysfunction, which may be underpinned by disruption within fronto-striatal and fronto-parietal circuits. We probed executive function in these disorders using a sustained attention task with a validated brain-behaviour basis. Twenty-three children with ADHD, 21 children with high-functioning autism (HFA) and 18 control children were tested on the Sustained Attention to Response Task (SART). In a fixed sequence version of the task, children were required to withhold their response to a predictably occurring no-go target (3) in a 1–9 digit sequence; in the random version the sequence was unpredictable. The ADHD group showed clear deficits in response inhibition and sustained attention, through higher errors of commission and omission on both SART versions. The HFA group showed no sustained attention deficits, through a normal number of omission errors on both SART versions. The HFA group showed dissociation in response inhibition performance, as indexed by commission errors. On the Fixed SART, a normal number of errors was made, however when the stimuli were randomised, the HFA group made as many commission errors as the ADHD group. Greater slow-frequency variability in response time and a slowing in mean response time by the ADHD group suggested impaired arousal processes. The ADHD group showed greater fast-frequency variability in response time, indicative of impaired top-down control, relative to the HFA and control groups. These data imply involvement of fronto-parietal attentional networks and sub-cortical arousal systems in the pathology of ADHD and prefrontal cortex dysfunction in children with HFA.

Optimal sustained attention is linked to the spectral content of background EEG activity: greater ongoing tonic alpha (∼10 Hz) power supports successful phasic goal activation

Efficient executive control frequently requires the timely activation or re-activation of a task-goal to enable purposeful behaviour. Additionally, more generalized factors such as alertness or neurological health will influence the efficiency with which control can be implemented. Goal-directed processes have been investigated by examining event-related potentials (ERPs), but much less is known about the involvement of background or 'tonic' processes reflected in the ongoing electroencephalogram (EEG), and how these affect the phasic processes expressed in the broad-band ERP. Here, we investigate the relationship between a key attention-sensitive tonic process--the alpha rhythm--and relevant phasic processes observed during a sustained attention paradigm in neurologically healthy subjects. We report that subjects with relatively higher tonic alpha power (approximately 10 Hz) show a larger-amplitude late positive ERP component that is thought to index goal activation and has been found to predict good sustained attention performance as defined by correct response patterns. Source localization results suggest that the neural generators responsible for oscillatory alpha activity, which are found primarily in the parietal and occipital lobes, are distinct from those giving rise to the late positive component. The results are discussed in terms of increased alpha synchrony facilitating goal-directed behaviour.

A comparison of covert and overt attention as a control option in a steady-state visual evoked potential-based brain computer interface

EEG data were recorded from occipital scalp regions of subjects who attended to an alternating checkerboard stimulus in one visual field while ignoring a similar stimulus of a different frequency in the opposite visual field. Classification of left/right spatial attention is attempted by extracting steady-state visual evoked potentials (SSVEPs) elicited by the stimuli to assess the potential use of such a spatial selective attention paradigm in a brain computer interface (BCI). Experimental setup and analysis procedure in a previous study in which eye movement is permitted are replicated in order to quantify differences in classification performance using overt and covert attention. Four variations of the basic paradigm, involving both feedback and addition of extra mental load, are studied for comparison. The average accuracy is found to be reduced by approximately 20% in the switch from overt to covert attention when no other specifications of the task are changed.

Response variability in attention deficit hyperactivity disorder: evidence for neuropsychological heterogeneity

Response time (RT) variability is a common finding in ADHD research. RT variability may reflect frontal cortex function and may be related to deficits in sustained attention. The existence of a sustained attention deficit in ADHD has been debated, largely because of inconsistent evidence of time-on-task effects. A fixed-sequence Sustained Attention to Response Task (SART) was given to 29 control, 39 unimpaired and 24 impaired-ADHD children (impairment defined by the number of commission errors). The response time data were analysed using the Fast Fourier Transform, to define the fast-frequency and slow-frequency contributions to overall response variability. The impaired-ADHD group progressively slowed in RT over the course of the 5.5min task, as reflected in this group's greater slow-frequency variability. The fast-frequency trial-to-trial variability was also significantly greater, but did not differentially worsen over the course of the task. The higher error rates of the impaired-ADHD group did not become differentially greater over the length of the task. The progressive slowing in mean RT over the course of the task may relate to a deficit in arousal in the impaired-ADHD group. The consistently poor performance in fast-frequency variability and error rates may be due to difficulties in sustained attention that fluctuate on a trial-to-trial basis.