Informed consent for anaesthesia in Australia and New Zealand.

The legal and ethical requirements related to an anaesthetist's communication with patients in preparing them for anaesthesia, assisting them in making appropriate decisions and obtaining consent in a formal sense are complex. Doing these things well takes time, skill and sensitivity. The primary focus should be to adequately prepare patients for surgery and to ensure that they are sufficiently well informed to make the choices that best meet their own needs. This is just an affirmation of the importance of patient-centred care.

What are we telling our patients? A survey of risk disclosure for anaesthesia in Australia and New Zealand.

The aim of our study was to determine the range of risks disclosed in four commonly-encountered clinical scenarios: knee arthroscopy, lumbar laminectomy, laparoscopic appendicectomy and laparotomy, and then to determine how often five commonly-disclosed risks were disclosed for each scenario. We conducted a pilot survey of consultant anaesthetists in the Auckland City Hospital, the Royal Melbourne Hospital and the Austin Hospital (response rate 59%). A web survey was then sent to 500 randomly-selected Australian and New Zealand College of Anaesthetists Fellows (response rate 29%). In the pilot survey, a wide range of risks were disclosed: five (range 0 to 13) for knee arthroscopy, seven (0 to 16) for lumbar laminectomy, six (0 to 13) for appendicectomy and nine (0 to 24) for laparotomy. In the web survey the disclosure rates for all risks varied widely from "rarely" to "always". Respondents were more likely to disclose risks infrequently if they were male (odds ratio 5.7, P = 0.002) or exclusively in private practice (odds ratio 4.1, P = 0.02). Age > 45 years was not associated with disclosure frequency (odds ratio 1.65, P = 0.23). While the low response rate limits the validity and generalisability of many of our findings, we can nevertheless confidently conclude that risk disclosure varies widely in Australia and New Zealand. This large variation should be of concern to all anaesthetists. More work is needed to understand the reasons for this variation, and to develop a stronger consensus among anaesthetists about what risks should be disclosed.

Electrophysiological evidence of functional integration between the language and motor systems in the brain: a study of the speech Bereitschaftspotential.

OBJECTIVE: We investigated whether the Bereitschaftspotential (BP), an event related potential believed to reflect motor planning, would be modulated by language-related parameters prior to speech. We anticipated that articulatory complexity would produce effects on the BP distribution similar to those demonstrated for complex limb movements. We also hypothesized that lexical semantic operations would independently impact the BP. METHODS: Eighteen participants performed 3 speech tasks designed to differentiate lexical semantic and articulatory contributions to the BP. EEG epochs were time-locked to the earliest source of speech movement per trial. Lip movements were assessed using EMG recordings. Doppler imaging was used to determine the onset of tongue movement during speech, providing a means of identification and elimination of potential artifact. RESULTS: Compared to simple repetition, complex articulations produced an anterior shift in the maximum midline BP. Tasks requiring lexical search and selection augmented these effects and independently elicited a left lateralized asymmetry in the frontal distribution. CONCLUSIONS: The findings indicate that the BP is significantly modulated by linguistic processing, suggesting that the premotor system might play a role in lexical access. SIGNIFICANCE: These novel findings support the notion that the motor systems may play a significant role in the formulation of language.

Patients' knowledge of the qualifications and roles of anaesthetists.

Patients' knowledge of anaesthetists' qualifications and roles remains inaccurate despite the efforts of professional bodies worldwide. However, patients have not been surveyed on this subject in Australia for more than 20 years. We therefore surveyed 200 patients attending the pre-admission clinic prior to elective non-cardiothoracic surgery in an Australian teaching hospital to determine current knowledge. Most (90.5%) patients stated that anaesthetists are medically qualified and 83.5% stated that they are medical specialists. Younger age, an English-speaking background and previous experience with surgery predicted knowledge of anaesthetists' qualifications. Most patients believed that anaesthetists work in the operating theatre and are continually present during surgery, but few recognised their leading role in the care of patients during surgery or their other roles outside the operating theatre. Increased efforts are required to inform patients about the roles of anaesthetists in their care.

Functional neuroanatomy of human vocalization: an H215O PET study.

Vocalization in lower animals is associated with a well-described visceromotor call system centered on the mesencephalic periacqueductal grey matter (PAG), which is itself regulated by paramedian cortical structures. To determine the role this phylogenetically older system plays in human phonation, we contrasted voiced and unvoiced speech using positron emission tomography and then evaluated functional connectivity of regions that significantly differentiated these conditions. Vocalization was associated with increased and highly correlated activity within the midline structures--PAG and paramedian cortices--described in lower mammalian species. Concurrent activation and connectivity of neocortical and subcortical motor regions--medial and lateral premotor structures and elements of basal ganglia thalamocortical circuitry--suggest a mechanism by which this system may have come under an increasing degree of voluntary control in humans. Additionally, areas in the temporal lobe and cerebellum were selectively activated during voiced but not unvoiced speech. These regions are functionally coupled to both visceromotor and neocortical motor areas during production of voiced speech, suggesting they may play a central role in self-monitoring and feedback regulation of human phonation.

Relating neuronal dynamics for auditory object processing to neuroimaging activity: a computational modeling and an fMRI study.

We investigated the neural basis of auditory object processing in the cerebral cortex by combining neural modeling and functional neuroimaging. We developed a large-scale, neurobiologically realistic network model of auditory pattern recognition that relates the neuronal dynamics of cortical auditory processing of frequency modulated (FM) sweeps to functional neuroimaging data of the type obtained using PET and fMRI. Areas included in the model extend from primary auditory to prefrontal cortex. The electrical activities of the neuronal units of the model were constrained to agree with data from the neurophysiological literature regarding the perception of FM sweeps. We also conducted an fMRI experiment using stimuli and tasks similar to those used in our simulations. The integrated synaptic activity of the neuronal units in each region of the model, convolved with a hemodynamic response function, was used as a correlate of the simulated fMRI activity, and generally agreed with the experimentally observed fMRI data in the brain areas corresponding to the regions of the model. Our results demonstrate that the model is capable of exhibiting the salient features of both electrophysiological neuronal activities and fMRI values that are in agreement with empirically observed data. These findings provide support for our hypotheses concerning how auditory objects are processed by primate neocortex.

Words in melody: an H(2)15O PET study of brain activation during singing and speaking.

We used H(2)15O PET to characterize the interaction of words and melody by comparing brain activity measured while subjects spoke or sang the words to a familiar song. Relative increases in activity during speaking vs singing were observed in the left hemisphere, in classical perisylvian language areas including the posterior superior temporal gyrus, supramarginal gyrus, and frontal operculum, as well as in Rolandic cortices and putamen. Relative increases in activity during singing were observed in the right hemisphere: these were maximal in the right anterior superior temporal gyrus and contiguous portions of the insula; relative increases associated with singing were also detected in the right anterior middle temporal gyrus and superior temporal sulcus, medial and dorsolateral prefrontal cortices, mesial temporal cortices and cerebellum, as well as in Rolandic cortices and nucleus accumbens. These results indicate that the production of words in song is associated with activation of regions within right hemisphere areas that are not mirror-image homologues of left hemisphere perisylvian language areas, and suggest that multiple neural networks may be involved in different aspects of singing. Right hemisphere mechanisms may support the fluency-evoking effects of singing in neurological disorders such as stuttering or aphasia.

The functional neuroanatomy of Tourette's syndrome: an FDG PET study III: functional coupling of regional cerebral metabolic rates.

Functional coupling of regional cerebral metabolic rates for glucose measured with [18F]-Fluoro-2-deoxy-D-glucose PET was compared in 18 drug-free patients with Tourette's Syndrome (TS) and 16 age- and sex-matched control subjects. Pearson product-moment correlation matrices containing correlations between metabolic rates in regions sampled throughout the brain were generated independently for TS patients and controls and compared. Significant differences between Z-transformed correlation coefficients were used to identify group differences, and revealed that the connectivity of the ventral striatum was most severely affected in TS. Changes in the coupling of other brain areas-primary motor areas, somatosensory association areas, and insula-also appeared to differentiate TS patients and controls. Evaluation of interrelationships between cortico-striato-thalamo-cortical circuits revealed the existence of functional connections between the motor and lateral orbitofrontal circuits in both groups, however, a reversal in the pattern of these interactions differentiated TS patients and controls. In controls, activity in these circuits appeared to be negatively correlated-i.e. increased activity in one is associated with relative inactivity the other. In TS patients, on the other hand, activity in the motor and lateral orbitofrontal circuits appears to be positively coupled. These results lend further credence to the hypothesis that altered limbic-motor interactions represent a pathophysiological hallmark of this disease.

Simulating transcranial magnetic stimulation during PET with a large-scale neural network model of the prefrontal cortex and the visual system.

Transcranial magnetic stimulation (TMS) exerts both excitatory and inhibitory effects on the stimulated neural tissue, although little is known about the neurobiological mechanisms by which it influences neuronal function. TMS has been used in conjunction with PET to examine interregional connectivity of human cerebral cortex. To help understand how TMS affects neuronal function, and how these effects are manifested during functional brain imaging, we simulated the effects of TMS on a large-scale neurobiologically realistic computational model consisting of multiple, interconnected regions that performs a visual delayed-match-to-sample task. The simulated electrical activities in each region of the model are similar to those found in single-cell monkey data, and the simulated integrated summed synaptic activities match regional cerebral blood flow (rCBF) data obtained in human PET studies. In the present simulations, the excitatory and inhibitory effects of TMS on both locally stimulated and distal sites were studied using simulated behavioral measures and simulated PET rCBF results. The application of TMS to either excitatory or inhibitory units of the model, or both, resulted in an increased number of errors in the task performed by the model. In experimental studies, both increases and decreases in rCBF following TMS have been observed. In the model, increasing TMS intensity caused an increase in rCBF when TMS exerted a predominantly excitatory effect, whereas decreased rCBF following TMS occurred if TMS exerted a predominantly inhibitory effect. We also found that regions both directly and indirectly connected to the stimulating site were affected by TMS.

Clinical performance and margin analysis of ariston pHc versus Solitaire I as posterior restorations after 1 year.

The resin composite Ariston pHc (pHc means pH control) was introduced as an alternative for fast amalgam replacement. The aim of the present study was to evaluate clinically the behaviour of this non-bonded resin composite material, promising the release of fluoride, calcium, and hydroxy ions, in comparison to a bonded resin composite (Solitaire I) in class I and II cavities. Ninety-nine cavities in 31 patients were restored in a controlled prospective clinical study. Fifty fillings were placed with Ariston pHc as per the manufacturer's instructions, i.e. neither with enamel etching nor with the use of rubber dam. The same patients received 49 Solitaire I restorations totally bonded with Solidbond using rubber dam. At baseline, after 6 months, and after 12 months, two investigators given the same instructions examined the restorations, according to modified USPHS codes and criteria. Forty selected restorations (20 Ariston, 20 Solitaire) were additionally analysed via replicas, using a stereo light microscope (SV 11, Zeiss, Germany) at 130x magnification. After 12 months, 95 restorations were rated clinically acceptable (6% failure rate for Ariston pHc; 2% for Solitaire). Statistically significant differences were computed for both materials regarding the criterion "filling integrity". Further statistically significant deterioration for Ariston pHc between the three evaluations has been detected for the criteria "tooth integrity" (enamel cracks) and "marginal adaptation" (gap formation/Friedman 2-way ANOVA; p<0.05). With Ariston the criterion "hypersensitivity" also increased significantly after 1 year in comparison to Solitaire. The microscopic margin analysis revealed significantly increasing marginal deficiencies over time for both materials regarding the criteria "perfect margin", "gap formation", and "negative step" (P<0.05; Friedman 2-way ANOVA).

The neural organization of discourse: an H2 15O-PET study of narrative production in English and American sign language.

In order to identify brain regions that play an essential role in the production of discourse, H2 15O-PET scans were acquired during spontaneous generation of autobiographical narratives in English and in American Sign Language in hearing subjects who were native users of both. We compared languages that differ maximally in their mode of expression yet share the same core linguistic properties in order to differentiate the stages of discourse production: differences between the languages should reflect later, modality-dependent stages of phonological encoding and articulation; congruencies are more likely to reveal the anatomy of earlier modality-independent stages of conceptualization and lexical access. Common activations were detected in a widespread array of regions; left hemisphere language areas classically related to speech were also robustly activated during sign production, but the common neural architecture extended beyond the classical language areas and included extrasylvian regions in both right and left hemispheres. Furthermore, posterior perisylvian and basal temporal regions appear to play an integral role in spontaneous self-generated formulation and production of language, even in the absence of exteroceptive stimuli. Results additionally indicate that anterior and posterior areas may play distinct roles in early and late stages of language production, and suggest a novel model for lateralization of cerebral activity during the generation of discourse: progression from the early stages of lexical access to later stages of articulatory-motor encoding may constitute a progression from bilateral to left-lateralized activation. This pattern is not predicted by the standard Wernicke-Geschwind model, and may become apparent when language is produced in an ecologically valid context.

Dissociated pattern of activity in visual cortices and their projections during human rapid eye movement sleep.

Positron emission tomography was used to measure cerebral activity and to evaluate regional interrelationships within visual cortices and their projections during rapid eye movement (REM) sleep in human subjects. REM sleep was associated with selective activation of extrastriate visual cortices, particularly within the ventral processing stream, and an unexpected attenuation of activity in the primary visual cortex; increases in regional cerebral blood flow in extrastriate areas were significantly correlated with decreases in the striate cortex. Extrastriate activity was also associated with concomitant activation of limbic and paralimbic regions, but with a marked reduction of activity in frontal association areas including lateral orbital and dorsolateral prefrontal cortices. This pattern suggests a model for brain mechanisms subserving REM sleep where visual association cortices and their paralimbic projections may operate as a closed system dissociated from the regions at either end of the visual hierarchy that mediate interactions with the external world.

Asymmetry of chimpanzee planum temporale: humanlike pattern of Wernicke's brain language area homolog.

The anatomic pattern and left hemisphere size predominance of the planum temporale, a language area of the human brain, are also present in chimpanzees (Pan troglodytes). The left planum temporale was significantly larger in 94 percent (17 of 18) of chimpanzee brains examined. It is widely accepted that the planum temporale is a key component of Wernicke's receptive language area, which is also implicated in human communication-related disorders such as schizophrenia and in normal variations such as musical talent. However, anatomic hemispheric asymmetry of this cerebrocortical site is clearly not unique to humans, as is currently thought. The evolutionary origin of human language may have been founded on this basal anatomic substrate, which was already lateralized to the left hemisphere in the common ancestor of chimpanzees and humans 8 million years ago.

Regional cerebral blood flow throughout the sleep-wake cycle. An H2(15)O PET study.

To assess dynamic changes in brain function throughout the sleep-wake cycle, CBF was measured with H2(15)O and PET in 37 normal male volunteers: (i) while awake prior to sleep onset; (ii) during Stage 3-4 sleep, i.e. slow wave sleep (SWS); (iii) during rapid eye movement (REM) sleep; and (iv) upon waking following recovery sleep. Subjects were monitored polysomnographically and PET images were acquired throughout the course of a single night. Stage-specific contrasts were performed using statistical parametric mapping. Data were analysed in repeated measures fashion, examining within-subject differences between stages [pre-sleep wakefulness-SWS (n = 20 subjects); SWS-post-sleep wakefulness (n = 14); SWS-REM sleep (n = 7); pre-sleep wakefulness-REM sleep (n = 8); REM sleep-post-sleep wakefulness (n = 7); pre-sleep wakefulness-post-sleep wakefulness (n = 20)]. State dependent changes in the activity of centrencephalic regions, including the brainstem, thalamus and basal forebrain (profound deactivations during SWS and reactivations during REM sleep) are consistent with the idea that these areas are constituents of brain systems which mediate arousal. Shifts in the level of activity of the striatum suggested that the basal ganglia might be more integrally involved in the orchestration of the sleep-wake cycle than previously thought. State-dependent changes in the activity of limbic and paralimbic areas, including the insula, cingulate and mesial temporal cortices, paralleled those observed in centrencephalic structures during both REM sleep and SWS. A functional dissociation between activity in higher order, heteromodal association cortices in the frontal and parietal lobes and unimodal sensory areas of the occipital and temporal lobes appeared to be characteristic of both SWS and REM sleep. SWS was associated with selective deactivation of the heteromodal association areas, while activity in primary and secondary sensory cortices was preserved. SWS may not, as previously thought, represent a generalized decrease in neuronal activity. On the other hand, REM sleep was characterized by selective activation of certain post-rolandic sensory cortices, while activity in the frontoparietal association cortices remained depressed. REM sleep may be characterized by activation of widespread areas of the brain, including the centrencephalic, paralimbic and unimodal sensory regions, with the specific exclusion of areas which normally participate in the highest order analysis and integration of neural information. Deactivation of the heteromodal association areas (the orbital, dorsolateral prefrontal and inferior parietal cortices) constitutes the single feature common to both non-REM and REM sleep states, and may be a defining characteristic of sleep itself. The stages of sleep could also be distinguished by characteristic differences in the relationships between the basal ganglia, thalamic nuclei and neocortical regions of interest.

Altered patterns of cerebral activity during speech and language production in developmental stuttering. An H2(15)O positron emission tomography study.

To assess dynamic brain function in adults who had stuttered since childhood, regional cerebral blood flow (rCBF) was measured with H2O and PET during a series of speech and language tasks designed to evoke or attenuate stuttering. Speech samples were acquired simultaneously and quantitatively compared with the PET images. Both hierarchical task contrasts and correlational analyses (rCBF versus weighted measures of dysfluency) were performed. rCBF patterns in stuttering subjects differed markedly during the formulation and expression of language, failing to demonstrate left hemispheric lateralization typically observed in controls; instead, regional responses were either absent, bilateral or lateralized to the right hemisphere. Significant differences were detected between groups when all subjects were fluent-during both language formulation and non-linguistic oral motor tasks-demonstrating that cerebral function may be fundamentally different in persons who stutter, even in the absence of stuttering. Comparison of scans acquired during fluency versus dysfluency-evoking tasks suggested that during the production of stuttered speech, anterior forebrain regions-which play an a role in the regulation of motor function-are disproportionately active in stuttering subjects, while post-rolandic regions-which play a role in perception and decoding of sensory information-are relatively silent. Comparison of scans acquired during these conditions in control subjects, which provide information about the sensorimotor or cognitive features of the language tasks themselves, suggest a mechanism by which fluency-evoking maneuvers might differentially affect activity in these anterior and posterior brain regions and may thus facilitate fluent speech production in individuals who stutter. Both correlational and contrast analyses suggest that right and left hemispheres play distinct and opposing roles in the generation of stuttering symptoms: activation of left hemispheric regions appears to be related to the production of stuttered speech, while activation of right hemispheric regions may represent compensatory processes associated with attenuation of stuttering symptoms.

Interactions between D1 and D2 dopamine receptor family agonists and antagonists: the effects of chronic exposure on behavior and receptor binding in rats and their clinical implications.

Functional interactions between dopamine receptor subtypes may affect behavioral and biochemical responses which serve as models for neuropsychiatric illnesses and the clinical effects of drug therapy. We evaluated the effects of chronic exposure to the selective D1 receptor antagonist SCH 23390, and the selective D2 receptor antagonist metoclopramide, on spontaneous and drug-induced behavior and receptor density in rats, and then determined how these effects would be modified by concurrent administration of antagonists or agonists [SKF 38393, LY 171555 (quinpirole)] selective for the complementary receptor subtype. Administered alone, both the D1 and D2 antagonists had acute cataleptic effects to which animals became tolerant following chronic treatment, but the selective antagonists had opposing effects on spontaneous locomotor activity. Both antagonists produced equivalent, supersensitive behavioral responses to apomorphine, and resulted in an increase in D2 receptor density. Coadministration of the D1 and D2 antagonists had a synergistic effect on catalepsy, attenuated the effects on spontaneous locomotor activity observed with either drug alone, and had an additive effect on both apomorphine-induced stereotypic behavior and D2 receptor proliferation. On the other hand, when either selective antagonist was combined with the agonist selective for the complementary receptor subtype, both D2 receptor proliferation and behavioral supersensitivity were completely blocked. Combined antagonist-agonist treatments had opposing effects on the development of tolerance to antagonist-induced catalepsy. D2 - but not D1 - receptor densities were correlated with animals' behavioral responses to apomorphine. There results support and extend the notion that complex functional interactions between D1 and D2 receptor families occur within the central nervous system, and suggest that novel effects might be derived from combined administration of receptor selective agonists and antagonists.

The functional neuroanatomy of Tourette's syndrome: an FDG-PET Study. II: Relationships between regional cerebral metabolism and associated behavioral and cognitive features of the illness.

We analyzed F-18 fluoro-deoxyglucose PET scans carried out in 18 drug-free patients with Tourette's syndrome (TS) in order to evaluate relationships between cerebral metabolism and complex cognitive and behavioural features commonly associated with this disorder. These features (obsessions and compulsions, impulsivity, coprolalia, self-injurious behavior, echophenomena, depression, and measures of attentional and visuospatial dysfunction) were associated with significant increases in metabolic activity in the orbitofrontal cortices. Similar increases, although less robust, were observed in the putamen and, in the case of attentional and visuospatial measures, in the inferior portions of the insula. On the other hand, behavioral and cognitive features were not associated with metabolic rates in other subcortical (midbrain, ventral striatum), paralimbic (parahippocampal gyrus), or sensorimotor regions (supplementary motor area, lateral premotor or Rolandic cortices), in which metabolism had, in some cases more robustly, distinguished these TS patients from controls (Braun et al., 1993). These results suggest that a subset of regions in which metabolic activity appears to be associated with the diagnosis of TS per se, may be explicitly associated with the emergence of complex behavioral and cognitive features of the illness. This is most conspicuous in the orbitofrontal cortices, and it is consistent with the observation that these features resemble the elements of a behavioral syndrome typically seen in patients with lesions of the orbitofrontal cortex.

Prefrontal cortical and hippocampal modulation of haloperidol-induced catalepsy and apomorphine-induced stereotypic behaviors in the rat.

Effects of prefrontal cortical or hippocampal excitotoxic lesions on behavioral parameters related to dopaminergic transmission in the basal ganglia were investigated in the rat. We examined haloperidol-induced catalepsy and apomorphine-induced stereotypic behaviors after ibotenic acid lesions of the medial prefrontal cortex (MPFC), dorsal (DH), or ventral hippocampus (VH) in adult rats. Haloperidol-induced (1 mg/kg) catalepsy was decreased in rats with either MPFC or VH but not DH lesions. While both DH and VH lesioned animals demonstrated a reduction in apomorphine-induced (0.75 mg/kg) stereotypic behaviors, the VH lesioned animals also showed an enhancement of locomotor activity. MPFC lesioned rats tended towards potentiation of stereotypic behaviors and reduced locomotion after apomorphine administration. These data indicate that loss of prefrontal cortical or hippocampal modulation leads to an enhancement of DA transmission within the basal ganglia, though the pattern of augmentation depends on the area lesioned.

A kinetic comparison of [18F]2-fluoro-2-deoxyglucose and [18F]2-fluoro-2-deoxymannose using positron emission tomography.

Rate constants and fractional metabolic rates were estimated for the stereoisomers [18F]2-fluoro-2-deoxyglucose (FDG) and [18F]2-fluoro-2-deoxymannose (FDM) in 5 male baboons using positron emission tomography. Each animal, serving as its own control, was injected with both compounds under controlled physiological conditions. Results indicate that there is a 20% reduction in apparent cerebral metabolic rates for glucose when FDM is used as the analogue. This suggests that as supplies of 18O become depleted, the presence of FDM as an impurity should warrant consideration in the choice of alternatives to no-carrier-added FDG synthesis.