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PubMed2001

Structural MRI volumetric analysis in patients with organic amnesia, 2: correlations with anterograde memory and executive tests in 40 patients.

BACKGROUND: Cognitive-MRI correlations have often been studied in disorders in which there are multiple cognitive deficits and widespread cortical atrophy, such as Alzheimer's dementia. In such circumstances, the interpretation of any single cognitive-structural correlation is equivocal. Only by measuring differing cognitive functions and a wide range of brain structures in patients with a varying distribution of lesions or atrophy can specific brain-cognitive relations be determined in neurological disorder. METHOD: In the present study, a clear set of anatomical criteria and detailed MRI segmentation procedures were applied to measure whole brain, and left and right frontal, temporal lobe, anterolateral and medial temporal volumes, as well as thalamic cross sectional areas in 40 patients with organic amnesia (from various diseases) and 10 healthy controls. RESULTS: Within the total patient group, anterograde memory measures correlated significantly with medial temporal, hippocampal, and thalamic measurements. A spatial memory measure correlated significantly with hippocampal volume, and temporal context memory with frontal volume. After a factor analysis of the cognitive measures, the association between anterograde memory and hippocampal volume was corroborated. Forgetting rates and subjective memory evaluations did not show any significant MR correlations and, of executive tests employed, only card sorting categories correlated significantly with frontal volume. CONCLUSION: Loss of volume in key brain structures (for example, hippocampus, thalamus) is detectable on quantitative MRI, and this loss of volume correlates significantly with impaired performance on measures of anterograde memory function. Correlations with hippocampal volume did not indicate a specific role in either recall or verbal memory, as opposed to recognition or visual memory.

Alcohol Amnestic Disorder↗

PubMed2006

Correlation of radiologist rank as a measure of skill in screening and diagnostic interpretation of mammograms.

PURPOSE: To determine whether skill in the interpretation of screening mammograms is correlated with skill in the interpretation of diagnostic mammograms. MATERIALS AND METHODS: The institutional review board of the University of South Florida approved this study. This study was determined to be exempt from informed consent requirements because of the retrospective use of images and was conducted before HIPPA requirements were implemented. A total of 59 radiologists interpreted screening and diagnostic performance test sets of mammograms with a 1-year interval. Interpretations were recorded with modifications of the Breast Imaging and Reporting Data System. Radiologist skill was measured as the radiologist's ranking among his or her cohort in each of several measures of performance (ie, performance test receiver operating characteristic curve area, performance test screening sensitivity, performance test diagnostic sensitivity, and associated specificities). Correlations between radiologist rank in screening and rank in the diagnostic performance test measures were analyzed with the Spearman rank correlation statistical test. RESULTS: Radiologist rank in screening interpretations and in diagnostic interpretations was found to be significantly correlated in all measurements (P < .05). However, only two measurments (ie, receiver operating characteristic curve area rank correlation of 0.327 and sensitivity rank correlation of 0.402) remained significant after adjusting for multiple testing. The correlation between ranked screening specificity and ranked diagnostic specificity (0.296) was significant at only the .05 level. CONCLUSION: The interpretive performance of radiologists among their peers is moderately correlated between screening and diagnostic interpretations. Thus, proficiency in one area does not guarantee proficiency in the other area for some radiologists.

Clinical Competence↗

PubMed2006

Sensitivity of the cross-correlation between simulated surface EMGs for two muscles to detect motor unit synchronization.

The purpose of the study was to evaluate the use of cross-correlation analysis between simulated surface electromyograms (EMGs) of two muscles to quantify motor unit synchronization. The volume conductor simulated a cylindrical limb with two muscles and bone, fat, and skin tissues. Models of two motor neuron pools were used to simulate 120 s of surface EMG that were detected over both muscles. Short-term synchrony was established using a phenomenological model that aligned the discharge times of selected motor units within and across muscles to simulate physiological levels of motor unit synchrony. The correlation between pairs of surface EMGs was estimated as the maximum of the normalized cross-correlation function. After imposing four levels of motor unit synchrony across muscles, five parameters were varied concurrently in the two muscles to examine their influence on the correlation between the surface EMGs: 1) excitation level (5, 10, 15, and 50% of maximum); 2) muscle size (350 and 500 motor units); 3) fat thickness (1 and 4 mm); 4) skin conductivity (0.1 and 1 S/m); and 5) mean motor unit conduction velocity (2.5 and 4 m/s). Despite a constant and high level of motor unit synchronization among pairs of motor units across the two muscles, the cross-correlation index ranged from 0.08 to 0.56, with variation in the five parameters. For example, cross-correlation of EMGs from pairs of hand muscles, each having thin layers of subcutaneous fat and mean motor unit conduction velocities of 4 m/s, may be relatively insensitive to the level of synchronization across muscles. In contrast, cross-correlation of EMGs from pairs of leg muscles, with larger fat thickness, may exhibit a different sensitivity. These results indicate that cross correlation of the surface EMGs from two muscles provides a limited measure of the level of synchronization between motor units in the two muscles.

Computer Simulation↗

PubMed2002

A simulation study to examine the use of cross-correlation as an estimate of surface EMG cross talk.

Cross-correlation between surface electromyogram (EMG) signals is commonly used as a means of quantifying EMG cross talk during voluntary activation. To examine the reliability of this method, the relationship between cross talk and the cross-correlation between surface EMG signals was examined by using model simulation. The simulation results illustrate an increase in cross talk with increasing subcutaneous fat thickness. The results also indicate that the cross-correlation function decays more rapidly with increasing distance from the active fibers than cross talk, which was defined as the normalized EMG amplitude during activation of a single muscle. The influence of common drive and short-term motor unit synchronization on the cross-correlation between surface EMG signals was also examined. While common drive did not alter the maximum value of the cross-correlation function, the correlation increased with increasing motor unit synchronization. It is concluded that cross-correlation analysis is not a suitable means of quantifying cross talk or of distinguishing between cross talk and coactivation during voluntary contraction. Furthermore, it is possible that a high correlation between surface EMG signals may reflect an association between motor unit firing times, for example due to motor unit synchronization.

Adipose Tissue↗

PubMed1975

Control by Preynaptic Correlation: a mechanism affecting information transmission from Ia fibers to motoneurons.

1. In the unanesthetized spinal cord of the cat, simultaneous intracellular recordings were made from two motoneurons belonging to the gastronemius motor nucleus. 2. Supramaximal iterative stimulation of small branches of the gastrocnemius nerve produced monosynaptic EPSPs (Ia EPSPs) of varying amplitude superimposed on a fluctuating base line. 3. In most cases the variance of the motoneuron membrane potential was increased above base-line levels with a time course approximately matching the Ia EPSP. This suggests that Ia EPSP fluctuations are greater than can be accounted for by the base-line fluctuations alone. 4. For a given series of Ia EPSPs, the smaller responses in the series had about the same decay phase as the larger EPSPs, suggesting that most of the Ia EPSP fluctuations were not due to systematic changes in postsynaptic conductances produced by ongoing activity, but rather to a presynaptic mechanism. 5. Simultaneous recording from two motoneurons showed that base-line fluctuations were positively correlated. In most cases, however, there was an additional increased correlation above base-line levels resembling the time course of the Ia EPSPs, indicating positive correlation between EPSP fluctuations which is attributed to a presynaptic mechanism. 6. Conditioning volleys to group I muscle afferents or to low-threshold cutaneous afferents reduced the variance of the Ia EPSPs and also their correlation in motoneuron pairs, often without changing the mean Ia EPSPs. 7. It is concluded that, in the unanesthetized spinal cord, in addition to the random process which governs transmitter release intrinsic to a given synaptic terminal, there is another stochastic process affecting, in a correlated manner, transmitter release in large sets of Ia synaptic terminals. Most likely, the correlation in transmitter release is achieved by membrane potential fluctuations imposed on the Ia terminal arborizations by ongoing activity of the segmental mechanism mediating primary afferent depolarization. 8. The effects of such a correlating influence on cell firing behavior have been analyzed. The results suggest that this mechanism, referred to as control by presynaptic correlation, is able to modulate the information transmitted from Ia fibers to motoneurons.

Animals↗

PubMed1996

Oscillatory firing and interneuronal correlations in squirrel monkey striate cortex.

1. This work explores a mechanism that the brain may use for linking related percepts. It has been proposed that temporal relationships in the firing of neurons may be important in indicating how the stimuli that activate those neurons are related in the external world. Such temporal relationships cannot be seen with conventional receptive field mapping but require cross-correlation and auto-correlation analysis. 2. In the cat and the macaque monkey, cells with similar receptive field properties show correlated firing even when their receptive fields do not overlap. Here I report that in the squirrel monkey, as in the cat, pairs of cells < or = 5 mm apart can show correlated firing, and these correlations between pairs of cells are often stronger when they are stimulated by a single contour. This suggests that the correlations reflect not only permanent connections between cells with similar receptive fields, but in addition may encode information that the activating stimuli are continuous or part of a single object. I also find that, as in the cat, and contrary to some other reports on experiments in monkeys, the correlated firing is often rhythmic. These recordings further indicate that periods of rhythmicity are associated with stronger interneuronal synchrony, which is consistent with the hypothesis that recurrent feedback loops are involved in generating both. 3. Pairs of cells in the same cortical column, but at different depths also showed correlated firing, but with several milliseconds difference in timing between layers. This was true for cells at different depths within layer 2/3 and for pairs of cells in different layers (2/3 vs. 4B or 4C alpha), providing evidence for cross-talk between the magno- and parvocellular streams.

Anesthesia↗

PubMed1997

Sympathetically correlated activity of dorsal horn neurons in spinally transected rats.

In mammals with an intact neuraxis, most sympathetic nerve activity is generated by brain stem systems. Therefore these systems have attracted much more attention than spinal systems that generate excitatory inputs to sympathetic preganglionic neurons. The purpose of this study was to determine whether, within hours of C1 spinal cord transection, spinal dorsal horn neurons (DHNs) play a role in generating sympathetic nerve activity. Experiments were conducted in chloralose-anesthetized rats. We recorded renal sympathetic nerve activity (RSNA) in the left renal nerve, and we recorded the activity of neurons located in the left dorsal horn at T2, T8, T10, T13, and L2. We also recorded the activity of neurons in the right dorsal horn at T10. The somatic fields and cutaneous modalities of most neurons were determined. Spike-triggered averaging was used to determine relationships between the ongoing activity of DHNs and ongoing RSNA. In the left dorsal horn, bursts of ongoing activity of 16% of DHNs at T8 and 43% of DHNs at T10 were positively correlated with bursts of ongoing RSNA at latencies of 59 +/- 8 (SE) ms. At no other level on the left side, nor in the T10 segment on the right side, was the activity of DHNs correlated with RSNA. DHNs with activity correlated with RSNA were located only in dorsal horn laminae III-V. Deeper laminae were not investigated in these experiments. The activity of all sympathetically correlated DHNs exhibited bursts of action potentials with interspike intervals of < 10 ms. All but one of the sympathetically correlated DHNs exhibited wide-dynamic-range modalities. The modalities of sympathetically uncorrelated neurons were more heterogeneous. Brief (5-10 s) noxious cutaneous stimulation of mid- and lower thoracic dermatomes on the left side excited all sympathetically correlated DHNs and simultaneously increased RSNA. The excitatory cutaneous fields of sympathetically correlated neurons were circumscribed by the excitatory fields for RSNA. The excitatory cutaneous fields of some sympathetically uncorrelated DHNs extended beyond the excitatory fields for RSNA. Noxious cutaneous stimulation of the extremities on the left side that decreased RSNA simultaneously decreased the activity of all sympathetically correlated DHNs. These data provide electrophysiological evidence that, in spinally transected rats, a population of DHNs may generate or convey excitatory input to renal sympathetic preganglionic neurons.

Action Potentials↗

PubMed1999

Desynchronizing responses to correlated noise: A mechanism for binaural masking level differences at the inferior colliculus.

We examined the adequacy of decorrelation of the responses to dichotic noise as an explanation for the binaural masking level difference (BMLD). The responses of 48 low-frequency neurons in the inferior colliculus of anesthetized guinea pigs were recorded to binaurally presented noise with various degrees of interaural correlation and to interaurally correlated noise in the presence of 500-Hz tones in either zero or pi interaural phase. In response to fully correlated noise, neurons' responses were modulated with interaural delay, showing quasiperiodic noise delay functions (NDFs) with a central peak and side peaks, separated by intervals roughly equivalent to the period of the neuron's best frequency. For noise with zero interaural correlation (independent noises presented to each ear), neurons were insensitive to the interaural delay. Their NDFs were unmodulated, with the majority showing a level of activity approximately equal to the mean of the peaks and troughs of the NDF obtained with fully correlated noise. Partial decorrelation of the noise resulted in NDFs that were, in general, intermediate between the fully correlated and fully decorrelated noise. Presenting 500-Hz tones simultaneously with fully correlated noise also had the effect of demodulating the NDFs. In the case of tones with zero interaural phase, this demodulation appeared to be a saturation process, raising the discharge at all noise delays to that at the largest peak in the NDF. In the majority of neurons, presenting the tones in pi phase had a similar effect on the NDFs to decorrelating the noise; the response was demodulated toward the mean of the peaks and troughs of the NDF. Thus the effect of added tones on the responses of delay-sensitive inferior colliculus neurons to noise could be accounted for by a desynchronizing effect. This result is entirely consistent with cross-correlation models of the BMLD. However, in some neurons, the effects of an added tone on the NDF appeared more extreme than the effect of decorrelating the noise, suggesting the possibility of additional inhibitory influences.

Acoustic Stimulation↗

PubMed2000

Ongoing and stimulus-evoked activity of sympathetically correlated neurons in the intermediate zone and dorsal horn of acutely spinalized rats.

We have shown previously that in the acutely spinalized anesthetized rat the activities of many dorsal horn interneurons (DHN) at the T(10) level are correlated positively with both ongoing and stimulus-evoked renal sympathetic nerve activity (RSNA) and therefore may belong to networks generating RSNA after acute, cervical, spinal transection. In the present study, we recorded from both DHN and interneurons in the intermediate zone (IZN) of the T(10) spinal segment in acutely C(1)-transected, chloralose-anesthetized, artificially respired rats. The activities of a similar percentage of IZN and DHN were correlated positively with ongoing RSNA, but the peaks of spike-triggered averages of RSNA based on the activity of IZN were larger, relative to dummy averages, than spike-triggered averages of RSNA based on the activity of DHN. Sympathetically correlated DHN and IZN differed in their responses to noxious somatic stimuli. Most correlated DHN had relatively simple somatic fields; they were excited by noxious stimulation of the T(10) and nearby dermatomes and inhibited by stimulation of more distal dermatomes. As we have shown previously, the excitatory and inhibitory fields of these neurons were very similar to fields that, respectively, excited and inhibited RSNA. On the other hand, the somatic fields of 50% of sympathetically correlated IZN were significantly more complex, indicating a difference between either the inputs or the processing properties of IZN and DHN. Sympathetically correlated IZN and DHN also differed in their responses to colorectal distension (CRD), a noxious visceral stimulus. CRD increased RSNA in 11/15 rats and increased the activity of most sympathetically correlated T(10) IZN. On the other hand, CRD decreased the activity of a majority of sympathetically correlated T(10) DHN. These observations suggest that the same stimulus may differentially affect separate, putative, sympathoexcitatory pathways, exciting one and inhibiting the other. Thus the magnitude and even the polarity of responses to a given stimulus may be determined by the modality and location of the stimulus, the degree to which multiple pathways are affected by the stimulus, and the ongoing activity of presympathetic neurons, at multiple rostrocaudal levels, before stimulation. A multipathway system may explain the variability in autonomic responses to visceral and somatic stimuli exhibited in spinally injured patients.

Action Potentials↗

PubMed2006

The prognostic value and overexpression of cyclin A is correlated with gene amplification of both cyclin A and cyclin E in breast cancer patient.

UNLABELLED: Deregulation of cell cycle control is a hallmark of cancer. The primary cyclins (A, B1, D1, D3 and E) are crucial for cell cycle progression. Secondary cyclins (C and H) have putative indirect effects on cell cycle propulsion and are not previously evaluated in breast cancer. We have examined protein expression and gene amplification of cyclins in breast carcinomas and correlated the findings with clinical follow-up data. We have previously demonstrated that over-expression of cyclin A is associated with poor prognosis in breast cancer patients. In this study we wanted to evaluate the mechanisms behind overexpression of cyclin A, as well as the impact of other cyclins, both at the gene level and at the protein level, on prognosis of breast cancer patients. The impact of TP53 gene mutations on gene amplification of cyclins was also evaluated. METHODS: Real-Time Quantitative PCR was used to detect gene amplification of cyclins in tumour tissue from 86 patients operated for invasive breast carcinomas, while immunohistochemistry was applied to detect protein expression of the same cyclins. RESULT: Of the 80-breast tumour samples available for cyclin A gene amplification analyses, 26.7% (23/80) was defined to have cyclin A gene amplification. 37.2% (32/79) had cyclin B1 gene amplification, 82.6% (71/82) of the samples harboured amplification of cyclin C gene, 74.4% (64/82) had cyclin D1 gene amplification, 41.9% (36/86) had cyclin D3 gene amplification, 29.1% (25/81) of the patients had cyclin E gene amplification and 9.3% (8/86) of the samples showed amplification of the cyclin H gene. When correlation between gene amplification and protein expression was evaluated, we observed a statistical significant correlation between gene amplification and protein expression of cyclin A (p=0.009) and cyclin D3 (p<0.001). However, the correlation between gene amplification and protein expression of cyclin A, as well as the prognostic value of cyclin A overexpression, was affected by gene amplification of cyclin E. Gene amplification of none of the other cyclins was associated with patient prognosis. There was a statistical significant correlation between TP53 gene mutations and gene amplification of cyclins A, D3 and B1. No correlation was observed between gene amplification of secondary cyclins (H and C) and TP53 gene mutations. CONCLUSIONS: The overexpression of cyclin A is correlated to gene amplification of both cyclin A and cyclin E. Over-expression of cyclin A is associated with poor prognosis in breast cancer patients. When analysed in a multivariate analyses model, gene amplification as well as protein expression of none of the other cyclins than cyclin A are associated with patient prognosis in breast carcinomas. TP53 gene mutation seems to correlate with gene amplification of primary, but not secondary cyclins.

Breast Neoplasms↗

PubMed2005

Visualizing chromosomes as transcriptome correlation maps: evidence of chromosomal domains containing co-expressed genes--a study of 130 invasive ductal breast carcinomas.

Completion of the working draft of the human genome has made it possible to analyze the expression of genes according to their position on the chromosomes. Here, we used a transcriptome data analysis approach involving for each gene the calculation of the correlation between its expression profile and those of its neighbors. We used the U133 Affymetrix transcriptome data set for a series of 130 invasive ductal breast carcinomas to construct chromosomal maps of gene expression correlation (transcriptome correlation map). This highlighted nonrandom clusters of genes along the genome with correlated expression in tumors. Some of the gene clusters identified by this method probably arose because of genetic alterations, as most of the chromosomes with the highest percentage of correlated genes (1q, 8p, 8q, 16p, 16q, 17q, and 20q) were also the most frequent sites of genomic alterations in breast cancer. Our analysis showed that several known breast tumor amplicons (at 8p11-p12, 11q13, and 17q12) are located within clusters of genes with correlated expression. Using hierarchical clustering on samples and a Treeview representation of whole chromosome arms, we observed a higher-order organization of correlated genes, sometimes involving very large chromosomal domains that could extend to a whole chromosome arm. Transcription correlation maps are a new way of visualizing transcriptome data. They will help to identify new genes involved in tumor progression and new mechanisms of gene regulation in tumors.

Breast Neoplasms↗

PubMed1993

Correlation analysis between bovine populations, other farm animals, house pets, and multiple sclerosis prevalence.

In a previous study we analyzed the possible relationship between dairy product consumption and multiple sclerosis (MS) worldwide. We showed that a good correlation (Spearman rank p = 0.836), statistically strongly significant (p < 0.0001), existed between liquid cow milk consumption and MS prevalence. The interpretation of this strong correlation between MS and milk consumption is still unclear: fresh milk could be considered as a cofactor, but it could also reflect a much stronger association with MS of another unstudied factor, well correlated with milk consumption (yet, this is not the case for latitude). Obviously, the bovine population in each country and, particularly milk cows, has to be considered. In the present study, we analyze the correlations existing between the figures of national cow milk production and MS prevalence in 20 countries. We also analyze the correlations with the whole bovine, ovine, caprine, porcine, horse, poultry, cat and dog populations. Here again we find significant correlations between (i) cow milk production per inhabitant, (ii) national bovine density per inhabitant, and (iii) local bovine geographic density, and MS prevalence. However, these correlations are relatively weaker than that found with fresh liquid milk consumption in our previous study. No correlation is found with other farm animals or with pets in the same countries. The epidemiological significance of these results, suggesting a preponderant role of fresh cow milk, is discussed.

Animals↗

PubMed1997

Influence of gender on the correlation between plasma growth hormone profiles and urinary growth hormone excretion.

A lot of interest has been directed towards the measurement of urinary growth hormone (GH) excretion instead of plasma GH profiles or provocation tests. We investigated the factors influencing the relationship between 24- and 3-hour plasma GH profiles and urinary GH excretion in a cohort of 113 pediatric patients with growth disorders and healthy volunteers. Plasma and urinary GH were measured by polyclonal immunoassays differing in cross-reactivity with 20 kD GH (100 versus 46%), but not with 22-kD, dimer, deamidated and pituitary GH. In the 24-hour urine samples, only urinary GH excretion expressed as nanograms per 24 h correlated with plasma GH parameters, whereas the correlations for short-term samples were strongest if urinary GH excretion was expressed as nanograms per gram creatinine (r = 0.70-79, p < 0.00005-0.0001). In short-term samples urinary GH excretion depends on urinary volume and should thus be expressed in nanograms per gram creatinine, whereas 24-hour samples correlate best when urinary GH is expressed as nanograms per period. We found a significant sex difference (p < 0.02) in the correlation between 24-hour plasma GH profiles and urinary GH excretion with strong correlations in the female group (r = 0.63-0.78, p < 0.00005-0.0002) and a lack of correlation in the male group. The sex difference in the correlations between serum and urinary GH may reflect sex differences in GH profiles and metabolism, with urinary GH better reflecting the basal and slowly clearing portion of plasma GH than spontaneous GH peaks. The difference in cross-reactivities of molecular GH forms in polyclonal assays may have an impact on the correlation between plasma and urinary GH. Thus, the diagnostic value of urinary GH measurement as compared to serum GH profiles needs to be further evaluated.

Adolescent↗

PubMed1977

Correlation of mean pulmonary artery wedge pressure, left atrial dimention, and PTF-V1 in patients with acute myocardial infarction.

The mean pulmonary artery wedge pressure (PAWP), left atrial dimension (LAD) by echocardiography, and PTF-V1 in the electrocardiogram were correlated with each other in 16 patients with acute myocardial infarction in the control period and after therapeutic intervention with either Dextran or furosemide and/or nitroprusside. No significant correlation was found between a normal control PAWP and the LAD. An increased control PAWP correlated well with an increased LAD (r = 0.98). No significant correlation was found between the LAD and the PAWP whether normal or elevated after therapeutic intervention. No significant correlation was found between the PAWP whether normal or elevated and the PTF-V1. No significant correlation was found between the LAD and the PTF-V1. We conclude in acute myocardial infarction 1) the PTF-V1 is not useful in assessing PAWP before or after therapeutic intervention, 2) the LAD correlates poorly with a normal control PAWP but correlates well with an elevated control PAWP, and 3) the LAD cannot be used to assess PAWP after therapeutic intervention.

Acute Disease↗

PubMed1994

Blood pressure inversely correlates with thrombin-evoked calcium rise in platelets.

Earlier investigations showed a positive correlation between basal cytosolic free calcium in human platelets and blood pressure; however, recent studies have failed to show this relation. We undertook the present work to examine which platelet cytosolic calcium parameters (namely, cytosolic calcium in resting or stimulated states in calcium-containing and calcium-free media) present the least variability and best correlation with blood pressure. We studied 17 healthy white men on three different occasions separated by 1- and 4-week intervals. Their manual and ambulatory automated 24-hour blood pressure measurements were correlated with cytosolic calcium in resting and stimulated (thrombin-treated) fura 2-loaded platelets. The following cytosolic calcium parameters were measured in 1 mmol/L calcium and calcium-free media: basal cytosolic calcium, peak thrombin-evoked cytosolic calcium, and post-transient cytosolic calcium 5 minutes after thrombin treatment. The highest and lowest coefficients of variation were respectively shown by the basal cytosolic calcium (22.8%) and peak thrombin-evoked cytosolic calcium (10.1%) in calcium medium. Basal cytosolic calcium did not correlate with any of the blood pressure parameters. Of the cytosolic calcium parameters, peak thrombin-evoked cytosolic calcium in calcium medium demonstrated consistent (negative) correlations with blood pressure, with better correlations shown with diastolic than systolic blood pressure of both automated and manual blood pressure readings. Peak thrombin-evoked cytosolic calcium in calcium medium showed similar correlations with nighttime and daytime automated blood pressure measurements. There were no correlations between peak thrombin-evoked cytosolic calcium in calcium-free medium and blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2003

Cerebral autoregulation in carotid artery occlusive disease assessed from spontaneous blood pressure fluctuations by the correlation coefficient index.

BACKGROUND AND PURPOSE: Estimation of dynamic cerebral autoregulation from spontaneous fluctuations of arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) is an attractive monitoring option for cerebral hemodynamic impairment. We evaluated the correlation coefficient index method in patients with severe obstructive carotid disease and compared it with transfer function analysis (frequency domain approach to cerebral autoregulation) and CO2 vasomotor reactivity. METHODS: In 139 patients with severe unilateral carotid stenosis (>or=70%) or occlusion, CBFV (transcranial Doppler) and ABP (Finapres method) were recorded over 10 minutes. Correlations between systolic pressure, diastolic pressure, and mean ABP and CBFV oscillations over 1-minute epochs were averaged over 10 minutes to form the correlation coefficient indexes (Sx, Dx, Mx, respectively). Transfer function parameters (phase shift and gain between ABP and CBFV oscillations) were determined from the entire 10-minute period. CO2 reactivity was assessed by inhalation of 7% CO2. RESULTS: The correlation indexes Dx and Mx were significantly higher ipsilateral to stenosis and increased with degree of stenosis, indicating increasing dependence of CBFV on ABP and thus impairment of cerebral autoregulation. Dx and Mx correlated moderately but highly significantly with transfer function parameters and CO2 reactivity and showed a good level of agreement in detecting pathological values. Patients with a small variance of the 1-minute source correlations of Dx and Mx showed clearly better correlation values. Transfer function parameters and CO2 reactivity but not Dx and Mx were significantly poorer in patients with symptomatic stenosis or occlusion. CONCLUSIONS: The potential of the correlation coefficient indexes Dx and Mx in detecting hemodynamic impairment in patients with carotid stenosis is comparable to that of transfer function analysis and CO2 reactivity testing. In future, a combination of various hemodynamic tests might help to identify patients at risk for ischemic events.

Aged↗

PubMed2005

Motor impairment and recovery in the upper limb after stroke: behavioral and neuroanatomical correlates.

BACKGROUND AND PURPOSE: Motor recovery after stroke is associated with cerebral reorganization. However, few studies have investigated the relationship directly, and findings are equivocal. We therefore aimed to characterize the relationship between motor impairment, motor recovery, and task-related changes in regional cerebral blood flow (DeltarCBF) longitudinally. METHODS: We obtained a profile of motor impairment and recovery in the upper limb and conducted positron emission tomography motor activation studies using a simple finger-tapping task in 9 stroke patients 2 to 7 weeks after stroke and 6 months later. For correlation analysis, mean images of task-related DeltarCBF for each individual were linearly regressed with motor impairment scores. Motor recovery was correlated with longitudinal DeltarCBF images. RESULTS: Patients (7 males; 72.0+/-9.8 years) demonstrated a wide range of impairment severity and variable recovery. Upper-limb motor function was linearly correlated with task-related DeltarCBF. Importantly, sites of correlated DeltarCBF differed over time. Subacutely correlated DeltarCBF was observed in supplementary motor area (SMA), bilateral cingulate, and contralesional insula with a small area in ipsilesional primary sensorimotor cortex (SM1). Conversely, at the 6-month study, correlated DeltarCBF was primarily in ipsilesional SM1, extending to the cingulate gyrus. Better motor recovery was correlated with reduction in contralesional activity and increase in ipsilesional SM1. CONCLUSIONS: Upper-limb motor function and recovery are correlated with DeltarCBF in SMA, cingulate, insula, and SM1, highlighting the role of these areas in the recovery process. The dynamic nature of the relationship suggests ongoing adaptation within motor networks.

Aged↗

PubMed2000

Weak, stochastic temporal correlation of large scale synaptic input is A major determinant of neuronal bandwidth.

We determine the bandwidth of a model neurone to large-scale synaptic input by assessing the frequency response between the outputs of a two-cell simulation that share a percentage of the total synaptic input. For temporally uncorrelated inputs, a large percentage of common inputs are required before the output discharges of the two cells exhibit significant correlation. In contrast, a small percentage (5%) of the total synaptic input that involves stochastic spike trains that are weakly correlated over a broad range of frequencies exert a clear influence on the output discharge of both cells over this range of frequencies. Inputs that are weakly correlated at a single frequency induce correlation between the output discharges only at the frequency of correlation. The strength of temporal correlation required is sufficiently weak that analysis of a sample pair of input spike trains could fail to reveal the presence of correlated input. Weak temporal correlation between inputs is therefore a major determinant of the transmission to the output discharge of frequencies present in the spike discharges of presynaptic inputs, and therefore of neural bandwidth.

Action Potentials↗