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PubMed2003

Transmitral pulsed-Doppler echocardiography is a more accurate technique compared with two-dimensional echocardiography using dobutamine, in patients with one vessel coronary artery disease.

UNLABELLED: To examine the effects of dobutamine on pulsed-Doppler left ventricular filling indices and its utility for evaluation of CAD we studied 14 patients with normal coronary arteries (Group 1) and 39 patients with significant CAD (>70% diameter stenosis). Patients with coronary artery disease (CAD) were divided into two groups: patients with one-vessel coronary disease (Group 2); and those with multivessel CAD (Group 3). After stopping cardioactive treatment, patients underwent incremental dobutamine stress (5, 10, 20, 30 and 40 microg/kg/min) during pulsed-Doppler interrogation of diastolic filling with simultaneous heart rate and blood pressure measurements. The following transmitral Doppler variables were measured at baseline and at peak-dose of dobutamine: peak early (E) and peak atrial (A) velocity; E/A ratio; acceleration time (AT) and deceleration time (DT) of E wave; isovolumic relaxation time (IVRT); and time-velocity integral (TVI). Two-dimensional echocardiography was performed to detect regional asinergy and analyzed using a 16 segment model. RESULTS: Normals and CAD patients showed comparable changes in heart rate and blood pressure (P=NS between groups). Intergroup analysis of the changes of transmitral flow showed the significant changes for these indices (P<0.001): E velocity (-2.78+/-10.04, 12.4+/-9.4 and 16.47+/-10.65 cm/s); AT of E wave (1.66+/-2.47, -5.2+/-1.38 and -4.66+/-2.39 m/s(2)); DT of E wave (-0.23+/-0.18, 0.2+/-0.2 and 0.2+/-0.28 m/s(2)); and TVI of transmitral flow (-1.26+/-0.7, 3.5+/-1.75 and 4.1+/-1.66 cm), respectively for Groups 1, 2 and 3. All other transmitral Doppler variables showed insignificant changes (P=NS) to dobutamine between groups. It is important that the significance of these changes were the same for patients with one-vessel and those with multivessel coronary disease. In conclusion, during dobutamine stress testing, patients with CAD, had an abnormal response of these transmitral Doppler indices: E wave; AT of E wave; DT of E wave; and the TVI of transmitral flow. The abnormal responses of these Doppler indices of left ventricular filling are more accurate markers of significant single vessel CAD than new wall motion abnormalities during conventional DSE.

Adrenergic beta-Agonists↗

PubMed1981

Variable effect of nifedipine on myocardial blood flow at three grades of coronary occlusion in the dog.

The effect of nifedipine on myocardial blood flow at various grades of coronary stenosis is unknown, Thus 22 open-chest dogs underwent carotid to left anterior descending perfusion with flow and perfusion pressure monitoring. Grades of coronary occlusion were defined by minimum diastolic perfusion pressure. six dogs (group 1) underwent moderate occlusion to 50 to 55 mm Hg diastolic perfusion pressure; (group 2), severe occlusion to 40 mm Hg perfusion pressure; and six (group 3), more severe occlusion at 25 mm Hg. Regional myocardial blood flow was measured with radioactive microspheres before and after the intracoronary injection of 10 microgram of nifedipine. In group 1, nifedipine induced epicardial hyperemia and little change in endocardial flow in the ischemic zone. In group 2, nifedipine induced epicardial hyperemia from 1.06 to 1.39 mg/g per min, but endocardial flow decreased from 0.70 to 0.60 ml/g per min. In group 3, there was no change in blood flow. Thus the effect of nifedipine on myocardial blood flow depends on the extent of occlusion. Furthermore for certain degrees of occlusion, redistribution of blood flow from endocardium to epicardium has been shown to occur.

Animals↗

PubMed2004

Attenuation of the neural response to sad faces in major depression by antidepressant treatment: a prospective, event-related functional magnetic resonance imaging study.

BACKGROUND: Depression is associated with interpersonal difficulties related to abnormalities in affective facial processing. OBJECTIVES: To map brain systems activated by sad facial affect processing in patients with depression and to identify brain functional correlates of antidepressant treatment and symptomatic response. DESIGN: Two groups underwent scanning twice using functional magnetic resonance imaging (fMRI) during an 8-week period. The event-related fMRI paradigm entailed incidental affect recognition of facial stimuli morphed to express discriminable intensities of sadness. SETTING: Participants were recruited by advertisement from the local population; depressed subjects were treated as outpatients. PATIENTS AND OTHER PARTICIPANTS: We matched 19 medication-free, acutely symptomatic patients satisfying DSM-IV criteria for unipolar major depressive disorder by age, sex, and IQ with 19 healthy volunteers. Intervention After the baseline assessment, patients received fluoxetine hydrochloride, 20 mg/d, for 8 weeks. MAIN OUTCOME MEASURES: Average activation (capacity) and differential response to variable affective intensity (dynamic range) were estimated in each fMRI time series. We used analysis of variance to identify brain regions that demonstrated a main effect of group (depressed vs healthy subjects) and a group x time interaction (attributable to antidepressant treatment). Change in brain activation associated with reduction of depressive symptoms in the patient group was identified by means of regression analysis. Permutation tests were used for inference. RESULTS: Over time, depressed subjects showed reduced capacity for activation in the left amygdala, ventral striatum, and frontoparietal cortex and a negatively correlated increase of dynamic range in the prefrontal cortex. Symptomatic improvement was associated with reduction of dynamic range in the pregenual cingulate cortex, ventral striatum, and cerebellum. CONCLUSIONS: Antidepressant treatment reduces left limbic, subcortical, and neocortical capacity for activation in depressed subjects and increases the dynamic range of the left prefrontal cortex. Changes in anterior cingulate function associated with symptomatic improvement indicate that fMRI may be a useful surrogate marker of antidepressant treatment response.

Affect↗

PubMed1988

The BOR syndrome and renal agenesis--prenatal diagnosis and further clinical delineation.

This is the first report of prenatal diagnosis of a fetus with brachio-oto-renal dysplasia (BOR) syndrome with right-sided renal agenesis and severe left hypoplasia. The father of this fetus had malformed external ears, a left-sided preauricular pit and branchial cyst, and bilateral mild to moderate deafness without a demonstrable renal anomaly. This family highlights the variable expressivity seen in the autosomal dominant BOR syndrome, the importance of genetic counselling for families with BOR syndrome, and the aetiologic heterogeneity of renal agenesis.

Abnormalities, Multiple↗

PubMed2001

Human primary auditory cortex: cytoarchitectonic subdivisions and mapping into a spatial reference system.

The transverse temporal gyrus of Heschl contains the human auditory cortex. Several schematic maps of the cytoarchitectonic correlate of this functional entity are available, but they present partly conflicting data (number and position of borders of the primary auditory areas) and they do not enable reliable comparisons with functional imaging data in a common spatial reference system. In order to provide a 3-D data set of the precise position and extent of the human primary auditory cortex, its putative subdivisions, and its topographical intersubject variability, we performed a quantitative cytoarchitectonic analysis of 10 brains using a recently established technique for observer-independent definition of areal borders. Three areas, Te1.1, Te1.0, and Te1.2, with a well-developed layer IV, which represent the primary auditory cortex (Brodmann area 41), can be identified along the mediolateral axis of the Heschl gyrus. The cell density was significantly higher in Te1.1 compared to Te1.2 in the left but not in the right hemisphere. The cytoarchitectonically defined areal borders of the primary auditory cortex do not consistently match macroanatomic landmarks like gyral and sulcal borders. The three primary auditory areas of each postmortem brain were mapped to a spatial reference system which is based on a brain registered by in vivo magnetic resonance imaging. The integration of a sample of postmortem brains in a spatial reference system allows one to estimate the spatial variability of each cytoarchitectonically defined region with respect to this reference system. In future, the transfer of in vivo structural and functional data into the same spatial reference system will enable accurate comparisons of cytoarchitectonic maps of the primary auditory cortex with activation centers as established with functional imaging procedures.

Adult↗

PubMed1997

Variability of cerebral blood flow deficits in 99mTc-HMPAO SPECT in patients with Alzheimer's disease.

The purpose of this study was to analyse the frequency of the different pathological perfusion patterns in SPECT in a clinical, unselected population of patients with Alzheimer's disease. In 91 patients and 16 control subjects regional cerebral blood flow (rCBF) was measured with Single Photon Emission Computed Tomography (SPECT) using 99mTc-hexa-methyl-propyleneamine oxime (HMPAO). 95% confidence intervals obtained from the perfusion values of the control subjects were used to define normal perfusion ranges. The frequency of perfusion deficits in the left frontal, temporal, parietal and occipital lobes were 62.2%, 60.4%. 70.3% and 23.1%, respectively. In the right hemisphere the corresponding values were 60.4%, 58.2%, 63.7% and 9.9%. With the exception of the occipital lobes these frequencies were not significantly different. The analysis of the perfusion pattern of each patient revealed 35 different combinations of lobes with perfusion deficits. The temporo-parietal perfusion deficits were not more frequent than the temporofrontal perfusion deficits. These results suggest that in the clinical routine a high variety of heterogeneous rCBF patterns have to be expected.

Aged↗

PubMed1991

Intrapulmonary bronchial blood flow of rats as studied by the microsphere method.

The intrapulmonary bronchial blood flow of the left lung (systemic arterial blood flow to the left lung via the bronchial artery) was determined in 45 anesthetized and artificially ventilated male Wistar rats, weighing 263 +/- 5 g (mean +/- SEM). The microsphere method was employed and designed so that recirculating microspheres across the peripheral arteriovenous anastomoses were prevented from lodging in the left lung, and disturbances of the isovolemic state of the animals became minimal. Under normal conditions with a mean arterial pressure of 115 +/- 2 mmHg (n = 40), the bronchial blood flow of the left lung was found to be 0.307 +/- 0.033 ml/min on average, and amounted to 0.52 +/- 0.06% of the cardiac output. The flow (ml/min) normalized per kg body weight, 100 g wet lung, or 100 g dry lung was 1.14 +/- 0.12, 76 +/- 8, or 368 +/- 39, respectively. The total intrapulmonary bronchial blood flow of the left and right lungs could be estimated by multiplying the intrapulmonary bronchial flow of the left lung by the weight ratio (total:left) of 2.9. The variability of the flow data was small, as confirmed in a study with simultaneous injection of two differently radiolabeled microspheres. The reproducibility of duplicate measurements was excellent.

Animals↗

PubMed1999

Morphology, morphometry and probability mapping of the pars opercularis of the inferior frontal gyrus: an in vivo MRI analysis.

The pars opercularis occupies the posterior part of the inferior frontal gyrus. Electrical stimulation or damage of this region interferes with language production. The present study investigated the morphology and morphometry of the pars opercularis in 108 normal adult human cerebral hemispheres by means of magnetic resonance imaging. The brain images were transformed into a standardized proportional steoreotaxic space (i.e. that of Talairach and Tournoux) in order to minimize interindividual brain size variability. There was considerable variability in the shape and location of the pars opercularis across brains and between cerebral hemispheres. There was no significant difference or correlation between left and right hemisphere grey matter volumes. There was also no significant difference between sex and side of asymmetry of the pars opercularis. A probability map of the pars opercularis was constructed by averaging its location and extent in each individual normalized brain into Talairach space to aid in localization of activity changes in functional neuroimaging studies.

Adult↗

PubMed1981

The changing trend in surgical reconstruction of pectus excavatum.

The purpose of this presentation is to review our experience in the correction of pectus excavatum deformity over the past 25 years, to draw attention to some details of importance in securing an excellent end result, and to describe a slight technical modification which improves the cosmetic effect of the surgical procedure. Seventy-five operations were performed between 1951 and 1975 at the North Middlesex Hospital, Regional Cardiothoracic Centre, Edmonton, London, according to the various techniques known during that period. Results were variable until the introduction, 10 years ago, of an operation combining extensive resection of costal-cartilages (34, 35) and stabilization of the sternum (2, 3). Of 37 operations performed during the last 10 years, 35 have given excellent long-term results. The cosmetic results in our hands have been achieved by the use of a stainless steel plate passed beneath the sternum and left in situ for not more than 6 months.

Adolescent↗

PubMed1992

Regional myocardial deoxyglucose uptake following electrical stimulation of canine efferent sympathetic cardiopulmonary nerves.

OBJECTIVE: The aim was to study the effect of stimulating individual acutely decentralised cardiopulmonary nerves on myocardial uptake of deoxyglucose. METHODS: In 17 open chest anaesthetised dogs the efferent axons of individual decentralised cardiopulmonary nerves were stimulated intermittently throughout 1 h while haemodynamic variables were measured. Tritiated 2-deoxyglucose was injected intravenously at the beginning of stimulation. Atropine was given when a cardiopulmonary nerve with efferent parasympathetic axons was studied. Distribution of label was detected using a multiwire proportional chamber. It was compared to blood concentration of deoxyglucose to permit quantitative mapping of regional myocardial uptake during the stimulation of each nerve. RESULTS: Neural stimulation of most of sympathetic efferent cardiopulmonary nerves increased deoxyglucose uptake in all myocardial tissue. Uptake was greatest in the left ventricle, less in the right ventricle, and least in the left and right atria. Regional myocardial uptake was also observed following individual cardiopulmonary nerve stimulation. Some nerves caused greater uptake than others. Cardiopulmonary nerves which are known to enhance inotropism when stimulated induced little increase of deoxyglucose uptake, whereas other nerves known to exert little positive inotropic effect induced considerable uptake. There was no correlation between haemodynamic changes and deoxyglucose uptake. CONCLUSIONS: It appears that (1) efferent sympathetic axons in one cardiopulmonary nerve can preferentially increase deoxyglucose uptake in specific regions of the myocardium and (2) the mechanisms responsible for enhancement of glucose uptake may differ from those responsible for inotropic responses.

Animals↗

PubMed1985

Coronary anatomy and left ventricular function in the first 12 hours of acute myocardial infarction: the Western Washington Randomized Intracoronary Streptokinase Trial.

The relationships among clinical variables, coronary anatomy, and left ventricular function during the early hours of acute myocardial infarction (AMI) were evaluated from data acquired in the Western Washington Intracoronary Streptokinase Trial. All patients had symptoms and electrocardiographic changes typical of AMI. All data were obtained before treatment with streptokinase. Mean time to catheterization was 4.1 hr after onset of symptoms. Coronary angiograms (n = 245) were analyzed for location of infarct-related occlusion and collateral flow to the infarct bed. Left ventricular ejection fraction and regional left ventricular function were quantitated in 227. Sixty-two percent of occlusions were in the most proximal segment of the involved coronary artery. Collateral circulation was seen in 42% overall, in 31% with left anterior descending artery (LAD) occlusion, and in 52% with right coronary artery (RCA) occlusion (p less than .005). Left ventricular ejection fraction was lowest and regional function was most abnormal in the group with proximal LAD occlusion. Hyperkinesis was present in 32%; in those with hyperkinesis, hyperkinetic segment length was longest in those with RCA or circumflex occlusion. Multivariate analysis identified proximal LAD occlusion as the factor most closely associated with left ventricular ejection fraction and with measures of left ventricular regional hypofunction. We conclude that (1) AMI is usually caused by occlusion or subtotal occlusion in the most proximal portion of the involved coronary artery, (2) collateral circulation is more frequent with RCA than with LAD occlusion, and (3) location of the infarct-related occlusion is the most important determinant of global and regional left ventricular function in the early hours of AMI.

Aged↗

PubMed2002

Frontoparietal cortical atrophy with gliosis in the gray matter of cerebral cortex: case report.

The case of a patient who suffered from progressive amnesia, depressive humor, language and visuospatial disturbances, and hallucination episodies with interference at the daily living activities is reported. She had moderate neuropsychological diffuse deficits at the first examination, especially at the executive and visuo-constructive functions. Her cerebrospinal fluid test presented high total protein. Magnetic resonance image showed slight white matter increase in periventricular, semi-oval center bilateral and left external capsule regions, besides light frontal and parietal lobe atrophy, bilaterally. Brain single photon emission computerized tomography revealed both a bilateral moderate frontal and a severe parietal lobe hypoperfusion, especially on the left side. Macroscopic examination showed cortical atrophy, severe on the frontal, moderate on the parietal and mild on the posterior third temporal lobes, bilaterally. There was a slight atrophy on the neostriatum in the basal ganglia. The histopathological findings of the autopsy showed severe neuronal loss with intensive gemioscytic gliosis and variable degrees of status spongiosus in cortical layer. Hematoxylin-eosin and Bielschowsky staining did not show neuronal swelling (balooned cell), argyrophilic inclusion (Pick's bodies), neurofibrillary tangles nor senile plaques. Immunohistochemical staining for anti-ubiquitin, anti-tau, anti-beta-amyloide, and anti-prion protein were tested negative.

Alzheimer Disease↗

PubMed1982

Radionuclide techniques for valvular regurgitant index: comparison in patients with normal and depressed ventricular function.

We compared contrast angiography with three techniques of quantitating valvular regurgitation from radionuclide ventriculograms in 70 patients: 45 with documented regurgitation graded 1-4+, and 25 without regurgitation. The radionuclide "regurgitant index" (ratio of L to R ventricular stroke counts) was measured from fixed end-diastolic regions of interest (method A), from separate end-diastolic and end-systolic regions of interest (method B), and from a "stroke-volume image" (method C). Sensitivities for detecting 1+ or more regurgitation were: method A = 57.8%, method B = 37.8% and method C = 62.2%. Sensitivities for detecting 2+ or more regurgitation were: method A = 74.2%, method B = 54.8%, and method C = 77.4%. All methods are greater than 97% specific. Interobserver coefficients of variability were: method A = 9.1%, method B = 19.2%, and method C = 5.4%. The sensitivity of each method was improved when left-ventricular ejection fractions were greater than 0.35. No method consistently differentiated between 2+, 3+, and 4+ valvular regurgitation.

Angiography↗

PubMed1998

Assessment of left ventricular systolic wall motion velocity with pulsed tissue Doppler imaging: comparison with peak dP/dt of the left ventricular pressure curve.

To assess the usefulness of the tissue Doppler imaging variables for the evaluation of left ventricular (LV) systolic function, we compared variables obtained by the pulsed Doppler method with the LV ejection fraction (%EF) and the maximum value for the first derivative of LV pressure (peak dP/dt). We examined 65 patients, including 15 patients with noncardiac chest pain, 15 with ischemic heart disease, 15 with dilated cardiomyopathy, 10 with hypertensive heart disease, and 10 with asymmetric septal hypertrophic cardiomyopathy. The subendocardial systolic wall motion velocity patterns were recorded for LV posterior wall and ventricular septum in the parasternal LV long-axis view. The peak dP/dt was significantly lower in the hypertensive heart disease, hypertrophic cardiomyopathy, and dilated cardiomyopathy groups. The peak systolic velocity was lower and the time from the electrocardiographic Q wave to the peak of the systolic wave for the posterior wall was longer in the hypertensive heart disease (5.9 +/- 0.5 cm/sec and 215 +/- 21 msec, respectively), hypertrophic cardiomyopathy (6.2 +/- 0.9 cm/sec and 217 +/- 17 msec, respectively), and dilated cardiomyopathy (5.2 +/- 0.8 cm/sec and 235 +/- 26 msec, respectively) groups than in the noncardiac chest pain (7.7 +/- 0.9 cm/sec and 187 +/- 24 msec, respectively) and the ischemic heart disease (7.6 +/- 0.8 cm/sec and 184 +/- 22 msec, respectively) groups. In all groups, the peak systolic velocity and the time from the electrocardiographic Q wave to the peak of the systolic wave for the posterior wall correlated directly and inversely, respectively, with the %EF (r = 0.59, p < 0.0001; r = -0.59, p < 0.0001) and the peak dP/dt (r = 0.75, p < 0.0001; r = -0.68, p < 0.0001). Both tissue Doppler variables for the ventricular septum did not correlate with the %EF but roughly correlated with peak dP/dt. We conclude that the systolic LV wall motion velocity parameters obtained by pulsed tissue Doppler imaging may be useful for noninvasive evaluation of global LV systolic function in patients with no regional asynergy.

Cardiac Catheterization↗

PubMed2026

Initial 4-Year Experience With Microaxial Flow Pumps Within a Tertiary Centre in Regional Australia.

BACKGROUND & AIM: The Microaxial Flow Pump (MFP) is a miniaturised rotary pump that aspirates blood from the left ventricle and expels it into the ascending aorta. It unloads the left ventricle and increases mean arterial pressure and cardiac output. MFP is most commonly utilised in cardiogenic shock, for protected percutaneous coronary intervention (PCI), and for ventricular offloading in veno-arterial extracorporeal membrane oxygenation (VA-ECMO). METHOD: We conducted a retrospective review of all patients who underwent MFP insertion at John Hunter Hospital, Australia. Categorical data are represented as counts and percentages, with continuous variables described as means with standard deviations. RESULTS: Twenty-three MFP devices were inserted between September 2020 and May 2024. Five (22%) were for protected PCI, three (13%) for venting with VA-ECMO (ECPELLA), and 15 (65%) for acute coronary syndrome (ACS) and cardiogenic shock. The median age for the overall cohort was 62 years, with a 74% male predominance. Eighty percent of the protected PCI cohort were elective outpatient procedures, and there were no deaths in this cohort. The mortality in the ECPELLA group was 67%. Thirteen (87%) of the patients with cardiogenic shock presented with an anterior infarct, and 53% had cardiac arrest on admission. The overall morality in the cardiogenic shock cohort was 40%. Complications in this cohort included limb ischaemia in four patients (17%) and site bleeding in seven patients (30%). Four patients (17%) required vascular surgery intervention. CONCLUSION: Our initial experience showed the use of MFP in a tertiary centre was safe and feasible, allowing progression from protected percutaneous intervention to acute cardiogenic shock.

Humans↗

PubMed1991

Evaluation of dipyridamole-Doppler echocardiography for detection of myocardial ischemia and coronary artery disease.

Doppler assessment of left ventricular filling and ejection during dipyridamole stress may supplement wall motion analysis for detection of myocardial ischemia and coronary artery disease (CAD). Thirty-four patients taking no cardioactive therapy were studied using intravenous dipyridamole (0.6 mg/kg) during 2-dimensional and pulsed Doppler echocardiography. Twelve patients had normal coronary arteries (group 1) and the remainder, who had significant CAD, were divided into groups 2 (n = 11) and 3 (n = 11). Only subjects in group 2 developed myocardial ischemia manifest as reversible regional asynergy and ST-segment depression. Heart rate increased (16 +/- 9 beats/min, p less than 0.01) and mean blood pressure decreased (-5 +/- 8 mm Hg, p = not significant) uniformly across groups. Exaggerated hyperkinesia of normally contracting wall segments was the common response to dipyridamole infusion in patients with CAD. The respective mean percent changes in peak early diastolic velocity, peak atrial velocity, their ratio and ejection peak velocity, and mean acceleration for groups 1 (20, 42, -13, 20 and 23%), 2 (22, 32, -2, 10 and 14%) and 3 (23, 33, -6, 16 and 18%) were similar. Comparisons between normal patients and those with CAD and between groups 2 and 3 revealed no significant differences in the effect of dipyridamole on any variable. However, a decrease in both peak velocity and mean acceleration of left ventricular ejection was seen in 3 of 4 group 2 patients who developed severe ischemia. Dipyridamole-Doppler echocardiography is insensitive for detection of CAD and appears unable to identify myocardial ischemia unless this is severe. Hemodynamic changes and compensatory wall motion induced by dipyridamole may explain these findings.

Adult↗

PubMed2007

Analysis of intersubject variability in activation: an application to the incidental episodic retrieval during recognition test.

Since the brain may engage different neuronal systems for a single behavioral goal, activation may show intersubject variability expressed in the systematic recruitment of multiple distinct networks. We apply a principal component analysis (PCA) to activation over task conditions and subjects to reveal cortical networks that may underlie this intersubject variability. Normal subjects were presented with novel meaningless objects, which appeared in personally familiar or unfamiliar places. During a subsequent, event-related functional MRI (fMRI) experiment, each subject was presented with learned or novel objects in isolation and performed a learned/novel judgment. Recollection of places was not essential for the task, and may exhibit large intersubject variations. The right posterodorsal posterior cingulate cortex (pPCC) and left retrosplenial cortex, whose involvement in place-recognition has been previously established, were selected as regions of interest for the PCA. Neural responses to objects associated with familiar relative to unfamiliar places in pPCC, but not in the retrosplenial cortex, were negatively correlated with task-related activation (common over all objects) in the right anterolateral prefrontal cortex and the left intraparietal sulcus. The latter areas have been implicated previously in cognitive control and object recognition, respectively. These results suggest right prefrontal control over neural processes both in the left parietal cortex, related to object-recognition (enhancement), and pPCC, related to nonessential recollection of place-memory (suppression), but not in the retrosplenial cortex, related to the sense of familiarity. This analysis revealed an important aspect of functional anatomy that was not detectable using a conventional analysis of average activations.

Adolescent↗

PubMed2004

Response of human jaw muscles to axial stimulation of a molar tooth.

The reflexes of the main jaw-closer muscles (masseter and anterior temporalis) on both sides of the jaw were investigated using surface electromyography to observe reflex activity following mechanical stimulation of the 1st right upper-molar tooth at various forces under a number of levels of jaw-muscle activity. As with analogous studies performed on the incisor, three distinct reflex events were identified in the EMG before the earliest conscious subject reaction: early excitation, inhibition and late excitation. However, contrary to observations found during studies on the incisor, excitation, not inhibition was the primary reflex response. The application of a local anaesthetic block around the stimulated molar showed that the primary agents in eliciting the observed reflexes were not contained within the periodontium of the stimulated tooth. A diminished representation of periodontal mechanoreceptors around the molar teeth and more elaborate root structures, hence a more solid connection to the jaw and consequently less tooth movement, were deemed the likely reason for the distinction between the reflex responses of the incisal and molar regions. In addition to the reflex studies, the minimum reaction time of a number of subjects was determined to permit the distinction of a reflex event and an event that could be a conscious subject reaction. It was found that the reaction time of the temporalis muscles was significantly shorter than those of the masseter, while no significant difference was found between the left and right sides. Overall, the data showed that the presence or absence of background muscle activity and subject variability were the main causes of changes in the reflex response, provided the level of the stimulus was greater than 3 N. The application of local anaesthetic had no impact on the reflexes evoked.

Adolescent↗