A systematic review of literature on occupational health and safety interventions for older workers

As the global population ages there is an imperative to enhance labour participation of older workers in ways that support good physical and psychological health. However, there is limited guidance for organisations on how to do this effectively. This systematic review examined literature identified through four databases and a targeted web-search, yielding 39 PRISMA records (32 scholarly, seven grey literature) reporting workplace interventions aimed at improving the injury outcomes of older workers. The review revealed that organisational and composite interventions may be most effective, although an absence of robust research in this area and a scarcity of empirical evidence-based interventions known to improve injury outcomes for older workers was noted. Responding to these shortcomings, this article presents 'A future research agenda for older worker health, safety and well-being interventions.' This systems-based approach has a dual focus on organisational and composite interventions combined with robust research design.Practitioner summary: We conducted a systematic literature review of studies focussed on workplace interventions to improve the physical and psychological safety of older workers. Within the existing literature, evidence for effective interventions and guidance for organisations is weak. We present a future research agenda with a systems approach to address these gaps.

"The Challenge is Not to Make Her Feel Old and Bad": Exploring Australian Family Member Experiences of Conversations About Driving With Older Adults Using an Online Survey

This study explored the experiences of Australian family members having conversations about driving with older adults. An exploratory cross-sectional design using an online survey was carried out with Australian family members of current or retired (former) older drivers. One hundred and fifty-six intergenerational family members across Australia completed the survey. Qualitative content analysis of free-text responses identified that the outcomes of conversations were impacted by a range of environmental and individual factors. The essence of conversations centered around two opposing (positive and negative) discourses. The findings highlighted that an individualized approach to the content of conversations is required due to; driver attributes and actions, variations in the level of support experienced by family members, differences in physical and cognitive declines with age, negative perceptions on the impact of driving retirement, and absence of acceptable alternatives to driving. We recommend using positive discourse and reappraisal techniques when initiating driving conversations with older adults.

Older Worker-Orientated Human Resource Practices, Wellbeing and Leave Intentions: A Conservation of Resources Approach for Ageing Workforces

At a time where there are ageing populations, global shortages of skilled labour, and migration pathways impacted by the COVID-19 pandemic, retaining older workers presents as a vital strategic initiative for organizations globally. This study examines the role of Human Resource Practices (HRPs), which are oriented towards accommodating the needs of an ageing workforce in mitigating psychological distress and turnover intentions. The study collected self-reported survey data from 300 Australian employees over the age of 45, over two time points. Using structural equation modelling, the study analyzed the extent to which Older Worker-oriented Human Resources Practices (OW-HRPs) translate into employee psychological health and retention within organizations, through the mediation of ageism and work-life conflict. The results support our hypothesis that OW-HRPs are associated with lower ageism, better work-life balance; and in combination these reduce psychological distress and help retain older workers in the workforce. We conclude that OW-HRPs can foster work environments conducive to older worker wellbeing, supporting the retention of talent and maintaining effectiveness, in the face of substantial labour supply challenges brought on by the COVID-19 pandemic and an ageing population.

What is the impact of dementia on occupational competence, occupational participation and occupational identity for people who experience onset of symptoms while in paid employment? A scoping review

BACKGROUND/AIM

Engagement in meaningful occupation, including paid work is considered an important determinant of health, impacted by injury or illness. Dementia is one neurodegenerative syndrome with potential to compromise capacity for remaining engaged in paid employment. In response to 'ageing' populations globally, policy shifts within developed economies are increasing workforce participation for those over 45 years and eligibility ages for retirement pensions. Dementia onset is not limited to 'older age', consequently an increased impact of dementia is likely for both older workers and those experiencing younger onset dementia. Therefore, identifying and addressing workforce participation issues confronting people with dementia is becoming increasingly important for occupational therapy practice.

METHOD

This scoping review draws on peer reviewed literature to explore the impact of dementia on workers across the three domains of occupational engagement: occupational competence; occupational participation; and occupational identity using the Model of Human Occupation (MOHO). International studies published in English including full-text translations between 2000 and 2017 were identified from an incremental search of electronic databases (Web of Science; Scopus; Proquest; MEDLINE; CINAHL; and Health Business Elite) and hand searched reference lists.

RESULTS

Six relevant papers were identified and retained for analysis, all reporting qualitative studies. Data were collated under the three domains of occupational engagement and further organised into emergent subcategories. While evidence was limited, person-centred approaches addressing dementia-related changes in occupational competence; workforce participation choices; and redefinition of occupational identity may mitigate negative experiences associated with transitioning from paid worker roles.

CONCLUSION

There is a significant need for further research exploring the impact of dementia on engagement in paid work. Occupational therapists have an important part to play in enabling access to person-centred interventions that promote continued engagement in meaningful occupational roles, including opportunities to extend workforce participation and engage in supported transitions to retirement.

An integrative review: understanding driving retirement decisions for individuals living with a dementia

AIM

To synthesise primary research exploring decision making practices used to determine the time to retire from driving for individuals living with a dementia.

BACKGROUND

Driving requires complex cognitive and physical skills potentially compromised due to the progressive nature of dementia. Whilst on-road assessments are considered reliable indicators of driving capacity by clinicians, drivers with dementia disagree.

DESIGN

Integrative literature review informed by Whittemore & Knafl (2005).

DATA SOURCES

Electronic database search of Medline, CINAHL, Web of Science, Google Scholar 1997-2012; and incremental hand search.

REVIEW METHODS

Primary studies published in peer reviewed journals were appraised against quality assessment criteria using CASP methodological assessment tools.

RESULTS

A total of 43 studies were retained for synthesis. Key findings were abstracted and a themes matrix was generated to identify patterns of meaning. Six themes emerged: (i) dementia may compromise the complex task of driving; (ii) defining onset and severity of dementia is problematic; (iii) symptom progression impacts on driving skills; (iv) assessment of fitness to drive remains subjective; (v) some drivers are reluctant to accept negative assessment outcomes; and (vi) the search for effective strategies to enhance acceptance of driver retirement continues.

CONCLUSION

This integrative literature review identified a large body of knowledge exploring the issues of driving cessation for drivers with dementia. However a challenge remains for practitioners, drivers and their family carers regarding how best to address this highly emotive issue. Findings could inform a structured approach to address this sensitive topic in a timely manner.

Risk Stratification by Cardiac Biomarkers following Emergency Gastrointestinal Surgery

Perioperative cardiac complications are a major cause of death following emergency gastrointestinal surgery. Early diagnosis of subclinical myocardial injury and infarction may be improved by screening with cardiac biomarkers. The aim of this study was to assess the predictive value of troponin I (TnI) and B-type natriuretic peptide (BNP) in the early postoperative period after emergency gastrointestinal surgery. We prospectively recruited 48 patients undergoing major emergency surgery for gastrointestinal or colorectal pathology in a single district general hospital. The primary endpoint was mortality at 90 days following surgery. Overall survival was 81.3% (39/48), with 9 postoperative deaths. Elevated TnI (≥0.03 ng ) was the best predictor of mortality, associated with an odds ratio of death by 90 days of 14.3 (95% CI 1.50–337, ). A postoperative BNP concentration >408.5 pg  was associated with an odds ratio of death by 90 days of 13.6 (95% CI 2.03–106, ). A single measurement of postoperative BNP and TnI is a powerful predictor of short- to medium-term mortality in patients after emergency gastrointestinal surgery. Further work is required to demonstrate that cardiac biomarkers have independent predictive power and that patient outcomes can be improved.

Obstructive Sleep Apnea Syndrome:

To investigate the risk factors and characteristics of obstructive sleep apnea records were reviewed retrospectively of 88 patients at a European center (UK) during January-October 2005 and 198 patients at a Middle Eastern center (Qatar) from April 2002-April 2005. A greater percentage (83%) in the UK group had OSA (RDI-5 events/hr) compared to 55% in Qatar (p < 0.05). In both groups OSA was diagnosed more in males. Declared alcohol intake, smoking, insomnia, witnessed apnea and nocturia were associated significantly with OSA in the UK group (p < 0.05). BMI was significantly higher in the Qatar group (mean 34 kg/ m2) than the UK group (mean 31.2 kg/m2) (p < 0.05). The mean age, mean Epworth sleepiness score and associated vascular conditions were similar in both groups and hypertension was relatively common in both groups. It is concluded that obstructive sleep apnea in the West (UK) and the Middle East (Qatar) has similar risks and associations. That in the UK might arise from higher alcohol consumption and smoking of tobacco while mean BMI in Qatar is high although the exact contribution of these factors needs further evaluation.

Dual mycorrhizal colonization of forest-dominating tropical trees and the mycorrhizal status of non-dominant tree and liana species

The contribution of mycorrhizal associations to maintaining tree diversity patterns in tropical rain forests is poorly known. Many tropical monodominant trees form ectomycorrhizal (EM) associations, and there is evidence that the EM mutualism contributes to the maintenance of monodominance. It is assumed that most other tropical tree species form arbuscular mycorrhizal (AM) associations, and while many mycorrhizal surveys have been done, the mycorrhizal status of numerous tropical tree taxa remains undocumented. In this study, we tested the assumption that most tropical trees form AM associations by sampling root vouchers from tree and liana species in monodominant Dicymbe corymbosa forest and an adjacent mixed rain forest in Guyana. Roots were assessed for the presence/ absence of AM and EM structures. Of the 142 species of trees and lianas surveyed, three tree species (the mono-dominant D. corymbosa, the grove-forming D. altsonii, and the non-dominant Aldina insignis) were EM, 137 were exclusively AM, and two were non-mycorrhizal. Both EM and AM structures wer e observed in D. corymbosa and D. altsonii. These results provide empirical data supporting the assumption that most tropical trees form AM associations for this region in the Guiana Shield and provide the first report of dual EM/AM colonization in Dicymbe species. Dual colonization of the Dicymbe species should be further explored to determine if this ability contributes to the establishment and maintenance of site dominance.

Paper 22: Metal Surfaces in Contact under Normal Forces: Some Dynamic Stiffness and Damping Characteristics

This paper describes an experimental investigation into the dynamic stiffness characteristics of flat joints subjected to an alternating force superimposed on a steady pre-load. The joints consist of the interfaces between mild-steel discs arranged in a column, in sets with surfaces either turned or lapped together. The influences of pre-load and of alternating force frequency were investigated for both dry and oiled joints, for different values of surface finish, apparent joint area and oil viscosity. The ranges of the conditions considered are compatible with those existing in typical machine tool structures.

It was found that the dynamic stiffness of dry joints is independent of frequency and no energy dissipation is measurable. The stiffness is primarily a function of pre-load and surface finish, with apparent joint area becoming important only for very good surface finishes.

If oil is introduced into the joint interface, a quadrature stiffness component arises and is accompanied by an increase in the ‘in-phase’ stiffness component. The magnitudes of the oil film stiffness components decrease sharply with an increase in the effective oil film thickness, which is governed primarily by the surface roughness. They increase with oil viscosity, the apparent joint area and the frequency of vibration, and represent a potentially valuable source of vibration damping in engineering structures.

Machining Forces: Some Effects of Removing a Wavy Surface

Previous work has shown that during the removal of a surface waveform oscillating cutting force components arise which may have a phase difference with respect to the oscillating component of undeformed chip thickness; it has also shown that the shear angle is affected by the slopes of the surface waveform. However, no attempt to predict the oscillating force behaviour from the geometry of cutting has been reported. The present work attempts to achieve such a prediction by means of an analysis of the phase and magnitude of the oscillating force components acting in two directions; in the directions of the mean shear plane and of the tool rake face. In the analysis it is assumed that the shear angle oscillates in phase with and proportionally to the surface slope, and that the curvature of the chip varies with the undeformed chip thickness.

An experimental technique for cutting with variable undeformed chip thickness is described, together with a method for recording and measuring the oscillating components of force and undeformed chip thickness. Experimental results are presented which show the assumptions made in the analysis to be substantially valid; the predicted oscillating forces are shown to be in adequate agreement with experiment over a range of experimental conditions. It is shown that the oscillation of the shear angle is primarily dependent on the surface slope and that the frictional force behaviour is consistent with the characteristics of the two regions of friction, sticking and sliding, as found in work on cutting with constant undeformed chip thickness.

Depersonalization disorder: thinking without feeling

Patients with depersonalization disorder (DP) experience a detachment from their own senses and surrounding events, as if they were outside observers. A particularly common symptom is emotional detachment from the surroundings. Using functional magnetic resonance imaging (fMRI), we compared neural responses to emotionally salient stimuli in DP patients, and in psychiatric and healthy control subjects. Six patients with DP, 10 with obsessive-compulsive disorder (OCD), and six volunteers were scanned whilst viewing standardized pictures of aversive and neutral scenes, matched for visual complexity. Pictures were then rated for emotional content. Both control groups rated aversive pictures as much more emotive, and demonstrated in response to these scenes significantly greater activation in regions important for disgust perception, the insula and occipito-temporal cortex, than DP patients (covarying for age, years of education and total extent of brain activation). In DP patients, aversive scenes activated the right ventral prefrontal cortex. The insula was activated only by neutral scenes in this group. Our findings indicate that a core phenomenon of depersonalization--absent subjective experience of emotion--is associated with reduced neural responses in emotion-sensitive regions, and increased responses in regions associated with emotion regulation.

Functional magnetic resonance imaging of odor identification: the effect of aging

BACKGROUND

Sense of smell declines with age and impairment in olfaction has been observed in some neurodegenerative disorders such as Alzheimer's disease. Functional neuroimaging techniques enable researchers to observe brain regions activated by olfactory stimuli.

METHODS

We gave three mainly olfactory-mediated odors (limonene, methylsalicylate, and eugenol) to six young and six elderly subjects and observed the areas activated by using blood oxygen level dependent contrast functional magnetic resonance imaging.

RESULTS

The group mapping of young subjects showed extensive activation in the orbitofrontal cortex, commonly believed to be the olfactory cortex, some limbic areas (the hippocampus and the thalamus), regions involved with gustatory sensation (the anterior insula and the inferior postcentral gyrus), superior and inferior temporal gyri, and cerebellum. In the elderly group, only the left inferior temporal gyrus and the primary visual cortex reached accepted significance levels.

CONCLUSIONS

We have therefore confirmed previous reports of brain regions involved in olfactory processing in young volunteers and demonstrated decreased activation in elderly volunteers.

An fMRI study of reduced left prefrontal activation in schizophrenia during normal inhibitory function

Functional magnetic resonance imaging (fMRI) was used to investigate the hypothesis that schizophrenia is associated with a dysfunction of prefrontal brain regions during motor response inhibition. Generic brain activation of six male medicated patients with schizophrenia was compared to that of seven healthy comparison subjects matched for sex, age, and education level while performing 'stop' and 'go-no-go' tasks. No group differences were observed in task performance. Patients, however, showed reduced BOLD signal response in left anterior cingulate during both inhibition tasks and reduced left rostral dorsolateral prefrontal and increased thalamus and putamen BOLD signal response during stop task performance. Despite good task performance, patients with schizophrenia thus showed abnormal neural network patterns of reduced left prefrontal activation and increased subcortical activation when challenged with motor response inhibition.

Dispersed activation in the left temporal cortex for speech-reading in congenitally deaf people

Does the lateral temporal cortex require acoustic exposure in order to become specialized for speech processing? Six hearing participants and six congenitally deaf participants, all with spoken English as their first langugage, were scanned using functional magnetic resonance imaging while performing a simple speech-reading task. Focal activation of the left lateral temporal cortex was significantly reduced in the deaf group compared with the hearing group. Activation within this region was present in individual deaf participants, but varied in location from person to person. Early acoustic experience may be required for regions within the left temporal cortex in order to develop into a coherent network with subareas devoted to specific speech analysis functions.

Motor response suppression and the prepotent tendency to respond: a parametric fMRI study

In the present study we utilised functional magnetic resonance imaging (fMRI) to examine cerebral activation during performance of a classic motor task in which response suppression load was parametrically varied. Linear increases in activity were observed in a distributed network of regions across both cerebral hemispheres, although with more extensive involvement of the right prefrontal cortex. Activated regions included prefrontal, parietal and occipitotemporal cortices. Decreasing activation was similarly observed in a distributed network of regions. These response forms are discussed in terms of an increasing requirement for visual cue discrimination and suppression/selection of motor responses, and a decreasing probability of the occurrence of non-target stimuli and attenuation of a prepotent tendency to respond. The results support recent proposals for a dominant role for the right-hemisphere in performance of motor response suppression tasks that emphasise the importance of the right prefrontal cortex.

Cerebral regions associated with verbal response initiation, suppression and strategy use

Cerebral activation associated with performance on a novel task involving two conditions was investigated with functional magnetic resonance imaging (fMRI). In the response initiation condition, subjects nominated the general superordinate category to which each of a series of exemplars (concrete nouns) belonged. In the response suppression condition, subjects were required to nominate a general superordinate category to which each exemplar did not belong, with the instruction that they were not to nominate the same category response twice in a row. Both conditions produced distinct patterns of activation relative to an articulation control condition employing identical stimuli. When initiation and suppression conditions were directly compared, response suppression produced activation in the right frontal pole, orbital frontal cortex and anterior cingulate, left dorsolateral prefrontal cortex and posterior cingulate, and bilaterally in the precuneus, visual association cortex and cerebellum. Response latencies were significantly longer in the suppression condition. Two broadly-defined strategies associated with the correct production of words during the suppression condition were a self-ordered selection from among the superordinate categories identified during the first section of the task and the generation of novel category responses. The neuroanatomical correlates of response initiation, suppression and strategy use are discussed, as are the respective roles of response suppression and strategy generation.

Functional frontalisation with age: mapping neurodevelopmental trajectories with fMRI

The aim of this study was to investigate whether previously observed hypofrontality in adolescents with attention deficit-hyperactivity disorder (ADHD) during executive functioning [Rubia K, Overmeyer S, Taylor E, Brammer M, Williams S, Simmons A, Andrew C, Bullmore ET. Hypofrontality in attention deficit hyperactivity disorder during higher order motor control: a study using fMRI. Am J Psychiatry 1999;156(6):891-896] could be attributed to delayed maturation of frontal cortex. Brain activation of 17 healthy subjects, 9 adolescents and 8 young adults, during performance of a motor response inhibition task and a motor timing task was measured using functional magnetic resonance imaging (fMRI). The effect of age on brain activation was estimated, using the analysis of variance and regression, at both voxel and regional levels. In the delay task, superior performance in adults was paralleled by a significantly increased power of response in a network comprising prefrontal and parietal cortical regions and putamen. In the stop task, alternative neuronal routes--left hemispheric prefrontal regions in adults and right hemispheric opercular frontal cortex and caudate in adolescents--seem to have been recruited by the two groups for achieving comparable performances. A significant age effect was found for the prefrontal activation in both task, confirming the hypothesis of a dysmaturational pathogenesis for the hypofrontality in ADHD.

Corpus callosum may be similar in children with ADHD and siblings of children with ADHD

No previous studies have used morphological neuroimaging to compare children with ADHD with siblings of children with ADHD. To test the hypothesis that the total size of the corpus callosum is altered in children with hyperkinetic disorder, the corpus callosum was outlined from a single midline protondensity weighted slice (containing the septum pellucidum). Fifteen boys with a refined phenotype of ADHD (mean age 10.2 years) and 15 healthy male siblings of children with ADHD (mean age 10.6 years) were enrolled in the study. The two groups were compared for global brain size and the callosal areas of Witelson. No significant differences were found between the study and comparison groups for any of the corpus callosum areas, even after age, global brain size, and handedness were covaried (using MANOVA). In addition, corpus callosum sizes do not seem to differ between children with ADHD and unaffected siblings of children with ADHD. Clinicians should not base their pathophysiological diagnosis of this disorder on an abnormality of callosal development.

Trophic effects of purines in neurons and glial cells

In addition to their well known roles within cells, purine nucleotides such as adenosine 5' triphosphate (ATP) and guanosine 5' triphosphate (GTP), nucleosides such as adenosine and guanosine and bases, such as adenine and guanine and their metabolic products xanthine and hypoxanthine are released into the extracellular space where they act as intercellular signaling molecules. In the nervous system they mediate both immediate effects, such as neurotransmission, and trophic effects which induce changes in cell metabolism, structure and function and therefore have a longer time course. Some trophic effects of purines are mediated via purinergic cell surface receptors, whereas others require uptake of purines by the target cells. Purine nucleosides and nucleotides, especially guanosine, ATP and GTP stimulate incorporation of [3H]thymidine into DNA of astrocytes and microglia and concomitant mitosis in vitro. High concentrations of adenosine also induce apoptosis, through both activation of cell-surface A3 receptors and through a mechanism requiring uptake into the cells. Extracellular purines also stimulate the synthesis and release of protein trophic factors by astrocytes, including bFGF (basic fibroblast growth factor), nerve growth factor (NGF), neurotrophin-3, ciliary neurotrophic factor and S-100beta protein. In vivo infusion into brain of adenosine analogs stimulates reactive gliosis. Purine nucleosides and nucleotides also stimulate the differentiation and process outgrowth from various neurons including primary cultures of hippocampal neurons and pheochromocytoma cells. A tonic release of ATP from neurons, its hydrolysis by ecto-nucleotidases and subsequent re-uptake by axons appears crucial for normal axonal growth. Guanosine and GTP, through apparently different mechanisms, are also potent stimulators of axonal growth in vitro. In vivo the extracellular concentration of purines depends on a balance between the release of purines from cells and their re-uptake and extracellular metabolism. Purine nucleosides and nucleotides are released from neurons by exocytosis and from both neurons and glia by non-exocytotic mechanisms. Nucleosides are principally released through the equilibratory nucleoside transmembrane transporters whereas nucleotides may be transported through the ATP binding cassette family of proteins, including the multidrug resistance protein. The extracellular purine nucleotides are rapidly metabolized by ectonucleotidases. Adenosine is deaminated by adenosine deaminase (ADA) and guanosine is converted to guanine and deaminated by guanase. Nucleosides are also removed from the extracellular space into neurons and glia by transporter systems. Large quantities of purines, particularly guanosine and, to a lesser extent adenosine, are released extracellularly following ischemia or trauma. Thus purines are likely to exert trophic effects in vivo following trauma. The extracellular purine nucleotide GTP enhances the tonic release of adenine nucleotides, whereas the nucleoside guanosine stimulates tonic release of adenosine and its metabolic products. The trophic effects of guanosine and GTP may depend on this process. Guanosine is likely to be an important trophic effector in vivo because high concentrations remain extracellularly for up to a week after focal brain injury. Purine derivatives are now in clinical trials in humans as memory-enhancing agents in Alzheimer's disease. Two of these, propentofylline and AIT-082, are trophic effectors in animals, increasing production of neurotrophic factors in brain and spinal cord. Likely more clinical uses for purine derivatives will be found; purines interact at the level of signal-transduction pathways with other transmitters, for example, glutamate. They can beneficially modify the actions of these other transmitters.

A differential neural response to threatening and non-threatening negative facial expressions in paranoid and non-paranoid schizophrenics

Several studies have demonstrated impaired facial expression recognition in schizophrenia. Few have examined the neural basis for this; none have compared the neural correlates of facial expression perception in different schizophrenic patient subgroups. We compared neural responses to facial expressions in 10 right-handed schizophrenic patients (five paranoid and five non-paranoid) and five normal volunteers using functional Magnetic Resonance Imaging (fMRI). In three 5-min experiments, subjects viewed alternating 30-s blocks of black-and-white facial expressions of either fear, anger or disgust contrasted with expressions of mild happiness. After scanning, subjects categorised each expression. All patients were less accurate in identifying expressions, and showed less activation to these stimuli than normals. Non-paranoids performed poorly in the identification task and failed to activate neural regions that are normally linked with perception of these stimuli. They categorised disgust as either anger or fear more frequently than paranoids, and demonstrated in response to disgust expressions activation in the amygdala, a region associated with perception of fearful faces. Paranoids were more accurate in recognising expressions, and demonstrated greater activation than non-paranoids to most stimuli. We provide the first evidence for a distinction between two schizophrenic patient subgroups on the basis of recognition of and neural response to different negative facial expressions.

Event-Related changes of band power and coherence: methodology and interpretation

Event-related calculation of band power changes can be used to quantify event-related desynchronization, event-related synchronization, and event-related coherence (ERCoh). It is shown that in the case of a motor task especially, the ERCoh time course depends on the type of EEG derivation used, whereby referenced EEG data can result in a bilateral coherence increase, although both hemispheres generate independent sensorimotor rhythms. It is further shown that not only Rolandic mu rhythms but also central beta rhythms display a lack of interhemispheric linear phase coupling.

Lack of bilateral coherence of post-movement central beta oscillations in the human electroencephalogram

Voluntary finger movement results in attenuation or desynchronization of the Rolandic mu and central beta rhythms some seconds before movement, followed by a post-movement synchronization of the central beta activity (post-movement beta synchronization). Although it has been demonstrated that the Rolandic mu rhythms show a lack of bilateral coherence, the coherence between post-movement central beta oscillations over left and right hemispheres has, as yet, not been investigated. In this study, post-movement changes in central beta activity over left and right sensorimotor hand areas are investigated in 13 healthy subjects by calculation of event-related coherence (ERCoh). The ERCoh time course allows the investigation of linear phase-coupling before, during and after voluntary movement. It is shown that no interhemispheric coherence exists between post-movement beta oscillations.

Cerebral correlates of preserved cognitive skills in autism: a functional MRI study of embedded figures task performance

When considering the cognitive abilities of people with autism, the majority of studies have explored domains in which there are deficits. However, on tests of local processing and visual search, exemplified by the Embedded Figures Task (EFT), people with autism have been reported to demonstrate superiority over normal controls. This study employed functional MRI of subjects during the performance of the EFT to test the hypothesis that normal subjects and a group with autism would activate different brain regions and that differences in the patterns of these regional activations would support distinct models of cerebral processing underlying EFT performance in the two groups. It was found that several cerebral regions were similarly activated in the two groups. However, normal controls, as well as demonstrating generally more extensive task-related activations, additionally activated prefrontal cortical areas that were not recruited in the group with autism. Conversely, subjects with autism demonstrated greater activation of ventral occipitotemporal regions. These differences in functional anatomy suggest that the cognitive strategies adopted by the two groups are different: the normal strategy invokes a greater contribution from working memory systems while the autistic group strategy depends to an abnormally large extent on visual systems for object feature analysis. This interpretation is discussed in relation to a model of autism which proposes a predisposition towards local rather than global modes of information processing.

Prefrontal involvement in "temporal bridging" and timing movement

Brain activity exclusively related to a temporal delay has rarely been investigated using modern brain imaging. In this study we exploited the temporal resolution of functional magnetic resonance imaging (fMRI) to characterise, by sinusoidal regression analysis, differential neuroactivation patterns induced in healthy subjects by two sensorimotor synchronization tasks different in their premovement delay of either 0.6 s or 5 s. The short event rate condition required rhythmic tapping, while the long event rate condition required timing of intermittent movements. Left rostral prefrontal cortex, medial frontal cortex, SMA and supramarginal gyrus demonstrated increased MR signal intensity during low frequency synchronization, suggesting that these brain regions form a distributed neural network for cognitive time management processes, such as time estimation and motor output timing. Medial frontal cortex showed a biphasic pattern of response during both synchronization conditions, presumably reflecting frequency-independent motor output related attention. As predicted, sensorimotor and visual association areas demonstrated increased MR signal intensity during high frequency synchronization.

The trophic effects of purines and purinergic signaling in pathologic reactions of astrocytes

This article reviews the effects of extracellular purine bases, nucleosides, and nucleotides as intracellular signaling molecules with trophic effects on cells after insults to the brain and spinal cord. Astrocytes are the principal source of extracellular purines in brain after injury, ischemia, or trauma. In vitro and in vivo extracellular purines have both immediate and long-term trophic effects, including stimulation of astrocyte and neuronal differentiation, mitosis, morphogenesis, apoptosis, and stimulation of growth and trophic factor synthesis. The effects of the nucleoside adenosine and the nucleotide adenosine triphosphate (ATP) are mediated principally via specific receptors on the cell surface coupled to a series of signaling cascades. Unlike adenosine and ATP, guanosine and guanosine triphosphate (GTP) do not act at classical purine receptors. However, they exert similar effects on astrocytes, apparently by causing the astrocytes to release large amounts of adenosine and ATP over prolonged periods. The release of adenosine and ATP may be related to the effects of guanosine on the purine nucleoside transporters in the cell membrane, whereas the release of ATP may be due to the effects of GTP on the ATP-binding cassette (ABC) proteins. Physiologically, the effects of guanosine are important because this nucleoside, unlike adenosine, remains elevated for prolonged periods after brain injury.

Neural responses to facial and vocal expressions of fear and disgust

Neuropsychological studies report more impaired responses to facial expressions of fear than disgust in people with amygdala lesions, and vice versa in people with Huntington's disease. Experiments using functional magnetic resonance imaging (fMRI) have confirmed the role of the amygdala in the response to fearful faces and have implicated the anterior insula in the response to facial expressions of disgust. We used fMRI to extend these studies to the perception of fear and disgust from both facial and vocal expressions. Consistent with neuropsychological findings, both types of fearful stimuli activated the amygdala. Facial expressions of disgust activated the anterior insula and the caudate-putamen; vocal expressions of disgust did not significantly activate either of these regions. All four types of stimuli activated the superior temporal gyrus. Our findings therefore (i) support the differential localization of the neural substrates of fear and disgust; (ii) confirm the involvement of the amygdala in the emotion of fear, whether evoked by facial or vocal expressions; (iii) confirm the involvement of the anterior insula and the striatum in reactions to facial expressions of disgust; and (iv) suggest a possible general role for the perception of emotional expressions for the superior temporal gyrus.

Investigation of facial recognition memory and happy and sad facial expression perception: an fMRI study

We investigated facial recognition memory (for previously unfamiliar faces) and facial expression perception with functional magnetic resonance imaging (fMRI). Eight healthy, right-handed volunteers participated. For the facial recognition task, subjects made a decision as to the familiarity of each of 50 faces (25 previously viewed; 25 novel). We detected signal increase in the right middle temporal gyrus and left prefrontal cortex during presentation of familiar faces, and in several brain regions, including bilateral posterior cingulate gyri, bilateral insulae and right middle occipital cortex during presentation of unfamiliar faces. Standard facial expressions of emotion were used as stimuli in two further tasks of facial expression perception. In the first task, subjects were presented with alternating happy and neutral faces; in the second task, subjects were presented with alternating sad and neutral faces. During presentation of happy facial expressions, we detected a signal increase predominantly in the left anterior cingulate gyrus, bilateral posterior cingulate gyri, medial frontal cortex and right supramarginal gyrus, brain regions previously implicated in visuospatial and emotion processing tasks. No brain regions showed increased signal intensity during presentation of sad facial expressions. These results provide evidence for a distinction between the neural correlates of facial recognition memory and perception of facial expression but, whilst highlighting the role of limbic structures in perception of happy facial expressions, do not allow the mapping of a distinct neural substrate for perception of sad facial expressions.

Do changes in coherence always reflect changes in functional coupling?

It is well known that the rhythmic activity within the alpha band in the central area may be composed of two different types of rhythms: (i) the Rolandic mu rhythm, representing the intrinsic activity of the sensorimotor area, and (ii) rhythmic activity believed to be generated within parieto-occipital areas and to extend into central regions through volume conduction (the 'classical alpha rhythm'). In this paper we clearly demonstrate that this second type of rhythmic activity is not due to volume conduction from parieto-occipital areas. We also demonstrate the significant impact of the coexistence of these two types of rhythms on the interpretation of interhemispheric coherence measurements.

A specific neural substrate for perceiving facial expressions of disgust

Recognition of facial expressions is critical to our appreciation of the social and physical environment, with separate emotions having distinct facial expressions. Perception of fearful facial expressions has been extensively studied, appearing to depend upon the amygdala. Disgust-literally 'bad taste'-is another important emotion, with a distinct evolutionary history, and is conveyed by a characteristic facial expression. We have used functional magnetic resonance imaging (fMRI) to examine the neural substrate for perceiving disgust expressions. Normal volunteers were presented with faces showing mild or strong disgust or fear. Cerebral activation in response to these stimuli was contrasted with that for neutral faces. Results for fear generally confirmed previous positron emission tomography findings of amygdala involvement. Both strong and mild expressions of disgust activated anterior insular cortex but not the amygdala; strong disgust also activated structures linked to a limbic cortico-striatal-thalamic circuit. The anterior insula is known to be involved in responses to offensive tastes. The neural response to facial expressions of disgust in others is thus closely related to appraisal of distasteful stimuli.

Functional MR imaging during odor stimulation: preliminary data

PURPOSE

To determine the locations and extent of activation in areas of the brain at functional magnetic resonance (MR) imaging with olfactory stimulation and to determine whether accommodation or amplification of brain activation occurs with sequential olfactory stimulation.

MATERIALS AND METHODS

Five adult men with normal senses of smell underwent multisection, gradient-echo, echo-planar imaging according to a blood-oxygen-level-dependent experimental paradigm. Odorants that nearly exclusively stimulate the olfactory system and odorants that stimulate the olfactory and trigeminal nerves were compared by using repetitive imaging procedures.

RESULTS

Activation with olfactory nerve-mediated odorants was demonstrated in the orbitofrontal cortex (Brodmann area 11) with a right-sided predominance. Mild cerebellar stimulation was also observed. With repeated testing, overall activation with olfactory nerve-mediated odorants declined. Odorants that also stimulated the trigeminal nerve produced additional cingulate, temporal, cerebellar, and occipital activation. Activation with combined trigeminal and olfactory system odors increased more than sixfold with repeated testing.

CONCLUSION

Olfactory nerve-mediated and combined olfactory and trigeminal nerve-mediated odorants activate different regions of the brain. Orbitofrontal stimulation spreads to all parts of the brain when a trigeminal component is added. Habituation (deactivation) occurs with repeated testing of olfactory nerve-mediated odorants, while, paradoxically, activation increases with repeated exposure to odors that also stimulate the trigeminal nerve.