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PubMed2005

A comparison between socially anxious and depressive symptomatology in youth: a focus on perceived family environment.

The current study employed present-oriented self-report measures to compare groups of socially anxious, depressed, mixed socially anxious and depressed, and comparison youth on perceptions of the family environment, as assessed via the Family Environment Questionnaire (FEQ). Results indicated that the mixed and depressed groups rated their parents as being overly concerned with others' opinions, feeling ashamed of their performance, and restricting family sociability more than the socially anxious and comparison groups. With respect to the latter two groups, the socially anxious group rated their family environment more negatively than the comparison group on each of these variables. Implications of the findings and directions for future research are discussed.

Adolescent↗

PubMed2006

Direct comparison between ion-exchange chromatography and aqueous two-phase processes for the partial purification of penicillin acylase produced by E. coli.

A direct comparison of a chromatography and an aqueous two-phase system (ATPS) processes for the partial purification of penicillin acylase (PA) produced by a recombinant strain of E. coli, was performed. An established chromatography process for the recovery of PA was selected as a model system and characterised for comparison with a developed ATPS prototype process. PEG-phosphate systems were selected for the recovery of PA over PEG-citrate systems, since higher enzyme recovery and increased purity was obtained. ATPS proved to be suitable to process highly concentrated disrupted extract (35%, w/w) and maintain a high top phase enzyme recovery. In the direct comparison of the processes, the superiority of the ATPS approach was highlighted since a reduction of the number of unit operations from 7 to 4 was achieved. An outline economic analysis based on the cost of separation agent of the processes favour the ATPS process, in which a gross cost reduction of 37% (from 0.47 to 0.30 US dollars) was achieved. Such result was obtained considering a potential re-use of up to 100 times of the resin used in the chromatography process. Additionally, by assuming that all the unit operations are equivalent in investment and operating cost, further reduction of approximately 43% of the respectively involved cost can be obtained when the ATPS process is used. Overall, the proposed ATPS process comprising of PEG1450-phosphate, tie-line length (TLL) of 48.5% (w/w), volume ratio (Vr) of 1.0, pH of 7.0 and 35% (w/w) PA crude extract loaded into the system proved to be more efficient, recovering 97% of PA at the top phase (PEG rich phase) with a purity factor of 3.5. It is clear that the results reported herein raise the consideration for the potential substitution of the chromatography process for PA recovery from E. coli as a first step for the development of an optimised and economic process with evident commercial application.

Chromatography, Ion Exchange↗

PubMed2006

The effects of the Roche AMPLICOR HIV-1 MONITOR UltraSensitive Test versions 1.0 and 1.5 viral load assays and plasma collection tube type on determination of response to antiretroviral therapy and the inappropriateness of cross-study comparisons.

BACKGROUND: Because there are limited head-to-head data comparing antiretroviral combinations, physicians are tempted to rely on cross-trial comparisons to evaluate the relative efficacy of HIV drugs. However, a variety of factors can confound these comparisons, resulting in misleading or invalid conclusions. OBJECTIVES: To compare and evaluate the use of: (i) versions 1.0 and 1.5 of the Roche AMPLICOR HIV-1 MONITOR UltraSensitive assay, and (ii) ethylenediaminetetraacetic acid (EDTA) and plasma preparation (PPT) tubes on the proportion of HIV-infected patients who would be classified as virological responders in a multinational clinical trial. STUDY DESIGN: The study utilized was a randomized, double-blind trial comparing the efficacy and safety of atazanavir with efavirenz, each in combination with fixed-dose zidovudine/lamivudine, in antiretroviral-naïve patients. To evaluate the effect of monitor kit version, paired plasma samples from 634 patients at week 48 were analyzed using both versions 1.0 and 1.5 of the monitor kit. To evaluate the effect of collection tube type, paired plasma samples collected from 584 patients at week 52 using both EDTA and PPT tubes were assayed. Patients were classified as responders if HIV-1 RNA levels were below a pre-determined level of quantification (LOQ), both 400 and 50 copies/ml. RESULTS AND CONCLUSIONS: Substantially higher HIV-1 RNA levels were observed with monitor kit version 1.5, resulting in lower response rates. The version 1.0 monitor kit resulted in a 7% increase in patients classified as responders at the LOQ of 400 copies/ml and a 13% increase at the LOQ of 50 copies/ml. Consistently higher response rates (11% higher at the LOQ of 400 copies/ml and 34% higher at the LOQ of 50 copies/ml) were also observed when samples were collected in EDTA tubes compared with PPT tubes. Differences in monitor kit sensitivity and plasma collection procedures are key factors in study results and suggest caution when performing cross-study comparisons.

Alkynes↗

PubMed2004

Magnitude comparison in preschoolers: what counts? Influence of perceptual variables.

This study examined numerosity comparison in 3-year-old children. Predictions derived from the analog numerical model and the object-file model were contrasted by testing the effects of size and ratio between numerosities to be compared. Different perceptual controls were also introduced to evaluate the hypothesis that comparison by preschoolers is based on correlated perceptual variables rather than on number per se. Finally, the relation between comparison performance and verbal counting knowledge was investigated. Results showed no evidence that preschoolers use an analog number magnitude or an object-file mechanism to compare numerosities. Rather, their inability to compare sets controlled for surface area suggests that they rely on perceptual cues. Furthermore, the development of numerosity-based representations seems to be related to some understanding of the cardinality concept.

Child, Preschool↗

PubMed2005

A new scaling method for topographical comparisons of event-related potentials.

Recent studies have demonstrated that comparisons of scalp topographical distributions of event-related potentials (ERPs) between experiment conditions may not correctly indicate underlying changes in neural sources if the signals are not scaled prior to the comparisons. This important issue was re-evaluated in this paper using both simulated and experimental data. Simulated data were generated according to 16 different brain models containing 2-4 dipole sources varying in strength, orientation, origin and number. The changes made in the strength, orientation and origin included relative changes between the sources or symmetrical changes in the sources. Experimental data were ERPs collected from 45 infants at 3 months of age. Influences of linked-ear and average references were examined. A scaling method based on relations of signal amplitudes between conditions was devised and compared with the vector method (McCarthy and Wood, 1985). While real topographic differences generated by complex changes in underlying sources were preserved, interactions between condition and electrode site due to mere strength changes were successfully identified by the new method, irrespective of reference method used. However, the vector method was not always reliable because failure to differentiate or mistakenly indicate changes in sources may occur when a linked-mastoid reference was used. The method presented in this paper is reliable and recommended prior to topographic comparisons to distinguish different types of changes in underlying neural sources.

Algorithms↗

PubMed2005

Electrochemical genosensing of the interaction between the potential chemotherapeutic agent, cis-bis(3-aminoflavone)dichloroplatinum(II) and DNA in comparison with cis-DDP.

The interaction of cis-diamminedichloroplatinum(II) (cis-DDP) and the potential novel chemotherapeutic agent, cis-bis(3-aminoflavone)dichloroplatinum(II) (cis-BAFDP) was studied electrochemically with calf thymus double-stranded DNA (dsDNA) by using differential pulse voltammetry (DPV) with disposable pencil graphite electrode (PGE) at the surface. These studies were prompted by beneficial biological properties of cis-BAFDP in comparison with cis-DDP, which were proven in vitro both in human normal and cancer cells and in vivo. The changes in the experimental parameters such as the concentration of cis-DDP and cis-BAFDP were studied by using DPV; in addition, the reproducibility of this genosensor and the detection limit for each compound were determined. After the interaction of cis-DDP with dsDNA, the DPV signal of guanine and adenine was found to be decreasing. In comparison with cis-DDP, a dramatic decrease at adenine signal was also obtained after the interaction of cis-BAFDP and dsDNA. Similar results were also found in solution phase after the latter compound interacts with poly[A]. The features of the proposed electrochemical method for the detection of cis-BAFDP with DNA in comparison with cis-DDP are discussed and compared with those methods previously reported for the other type of DNA-targeted agents in the literature.

Adenine↗

PubMed2005

A new method to model change in cutaneous blood flow due to mechanical skin irritation part I: comparison between experimental and numerical data.

Mechanical skin irritation creates vasodilation. Vasodilation of vascular networks induces increase in blood volume and blood velocity. Both can be measured by Laser Doppler Velocimetry. We propose in this article a method permitting comparison between experimental and numerical results. Experimental data was obtained by Laser Doppler Velocimetry. Numerical results were obtained by a continuous model of the vascular network. The model consists of three layers. First and last layer are described by anisotropic and heterogeneous porous media. They represent the irrigation and the drainage of the vascular system. The intermediate layer is described by a lumped parameter model that does not permit horizontal fluxes. All vessels are compliant. The permeabilities depend on the volumes of the specific layer. Skin irritation is modeled by a change in compliance of small arterial blood vessels. The comparison between experimental and numerical data is based on the model proposed by Bonner and Nossal [1981. Model for laser Doppler measurements of blood flow. Appl. Opt. 20, 2097-2107]. The model describes the Doppler frequency spectrum S(omega) as a function of the optical phenomena creating the frequency shift. The comparison is based on the model of the first moment M1 approximately integralomegaS(omega)domega. The variables of the first moment can be determined by results of the numerical model. We have shown, that it exists a linear relation between the change in compliance and the following increase in first moment. Using this linear relation experimental and numerical data can be compared.

Humans↗

PubMed2005

Evaluation of the clinical sensitivity for the quantification of human immunodeficiency virus type 1 RNA in plasma: Comparison of the new COBAS TaqMan HIV-1 with three current HIV-RNA assays--LCx HIV RNA quantitative, VERSANT HIV-1 RNA 3.0 (bDNA) and COBAS AMPLICOR HIV-1 Monitor v1.5.

The COBAS TaqMan HIV-1 test (Roche Diagnostics) was compared with the LCx HIV RNA quantitative assay (Abbott Laboratories), the Versant HIV-1 RNA 3.0 (bDNA) assay (Bayer) and the COBAS Amplicor HIV-1 Monitor v1.5 test (Roche Diagnostics), using plasma samples of various viral load levels from HIV-1-infected individuals. In the comparison of TaqMan with LCx, TaqMan identified as positive 77.5% of the 240 samples versus 72.1% identified by LCx assay, while their overall agreement was 94.6% and the quantitative results of samples that were positive by both methods were strongly correlated (r=0.91). Similarly, in the comparison of TaqMan with bDNA 3.0, both methods identified 76.3% of the 177 samples as positive, while their overall agreement was 95.5% and the quantitative results of samples that were positive by both methods were strongly correlated (r=0.95). Finally, in the comparison of TaqMan with Monitor v1.5, TaqMan identified 79.5% of the 156 samples as positive versus 80.1% identified by Monitor v1.5, while their overall agreement was 95.5% and the quantitative results of samples that were positive by both methods were strongly correlated (r=0.96). In conclusion, the new COBAS TaqMan HIV-1 test showed excellent agreement with other widely used commercially available tests for the quantitation of HIV-1 viral load.

HIV Infections↗

PubMed2004

Randomized comparison of 6-mm straight grafts versus 6- to 8-mm tapered grafts for brachial-axillary dialysis access.

OBJECTIVE: This report presents the results of a prospective randomized study that compared 2 grafts of different diameter: 6 mm, and 8 mm tapered to 6 mm at the arterial site, placed in the upper arm for hemodialysis in a selected population of patients younger than 71 years without diabetes. METHODS: Seventy consecutive patients younger than 71 years without diabetes who required an upper arm graft between January 1997 and January 2002 and without previous access in the same limb were randomly allocated to receive either a 6-mm graft or 6- to 8-mm graft. Graft flow was measured every 3 months with the Doppler dilution technique. When access flow was less than 600 mL/min, fistulography was performed, and any stenosis was surgically treated with venous outflow replacement. Thrombectomy and associated stenosis treatment in the same stage was performed in all cases immediately after detection of thrombosis. Complication rate, and primary, assisted primary, and secondary patency rates were compared between the two groups with the Student t test and life table analysis. RESULTS: Mean access flow was 975 mL/min for 6-mm grafts (range, 600-1500 mL/min; 95% confidence interval [CI], 889-1070), and for 6- to 8-mm grafts was 1397 mL/min (range, 1122-2700 mL/min; 95% CI, 1122-1672). This difference was significant (P <.01). Complication rate was 0.45 episodes per graft-year in 6-mm grafts, and 0.19 episodes per graft-year in 6- to 8-mm grafts (P <.01). At 1, 2, and 3 years, primary patency rates were 62%, 58%, and 44%, respectively, for 6-mm grafts, and 85%, 78%, and 73% for 6- to 8-mm grafts; log-rank comparison between curves was P =.0259. At 1, 2, and 3 years, secondary patency rates were 85%, 85%, and 85%, respectively, for 6-mm grafts, and 90%, 90%, and 90% for 6- to 8-mm grafts; log-rank comparison between curves was not significant, at P =.0603. At 1, 2, and 3 years, assisted primary patency rates were 84%, 79%, and 76%, respectively, for 6-mm grafts, and 90% for 6- to 8-mm grafts; log-rank comparison was P =.0414. CONCLUSIONS: The results of this study show an advantage in terms of primary and assisted primary patency rates, and complication rate for upper arm grafts with diameter 6 mm to 8 mm over grafts with 6-mm diameter in a patient population younger than 70 years without diabetes. The finding of a similar secondary patency rate in both groups is probably due to the surveillance program with sequential measurement of access flow and prompt surgical treatment of stenosis. However, we needed twice the number of rescue procedures in 6-mm grafts to achieve a similar patency rate as with large-bore grafts. These study results must be carefully evaluated, taking into consideration the small number of patients and the selected patient population.

Arteriovenous Shunt, Surgical↗

PubMed2006

Automated computation of the Gyrification Index in prefrontal lobes: methods and comparison with manual implementation.

In this paper, we introduce an automated method of calculating Gyrification Index (GI), a measure of cortical folding. Automated GI (A-GI) is an in vivo GI implementation applied to MRI T1 weighted scans and is designed as an extension to the SPM analysis package. The A-GI tool is unbiased in its application, and is unlimited in the size of test cohort to which it can be applied. In comparison to manual methods, A-GI substantially reduces the time costs and improves repeatability. The current A-GI implementation is limited to analysis of prefrontal lobes, but an extension to provide whole brain A-GI is under consideration. In determination of the GI inner contour, A-GI traces high spatial frequencies typically missed in manual tracing, and thus, A-GI reports a high GI value. We examine the operation of this tool in two scan cohorts. We establish that the tool has good repeatability through its application to a cohort where 5 well individuals were scanned 5 times over a period of 6 months. This indicates that A-GI has low susceptibility to scanner noise and is not affected by the variability in brain representation given by repeat scans. We demonstrate replication of hand tracing results by comparisons with a manual GI study that has shown differences between high risk subjects who go on to develop schizophrenia and those who are at high risk but remain well. Direct scan by scan comparisons are carried out between manual and A-GI methods. In respect of scan orientation and coronal sampling, the methods differ, and these considerations contribute to a between methods right prefrontal ICC of 0.67 and left prefrontal ICC of 0.63. The replication results demonstrate that A-GI has discriminatory power equivalent to manual methods. A-GI is therefore a reliable measure of cortical folding that could be usefully applied to a number of MRI data sets of the brain in health and disease.

Frontal Lobe↗

PubMed2006

Spatially weighted BOLD signal for comparison of functional magnetic resonance imaging and near-infrared imaging of the brain.

We introduce a weighted spatial average of the functional magnetic resonance imaging (fMRI) BOLD signal (blood oxygen level-dependent) that is appropriate for comparison with the changes in oxy- and deoxy-hemoglobin concentrations measured with near-infrared spectroscopy (NIRS) during brain activation. Because the BOLD signal shows a spatial dependence (both in shape and amplitude) within the region of activation, the location of the optical probe with respect to the region of BOLD activation should be taken into account for comparison of the BOLD and NIRS signals. Our new method is based on combining weighted contributions of the BOLD signal from each activated voxel, with a weight given by a hitting density function for photons migrating between a given pair of illumination and collection points. We present a case study where we have found that the new spatially weighted BOLD signal shows a high spatial and temporal correlation with the oxy- and deoxy-hemoglobin concentration changes measured with NIRS during a hand-tapping protocol. These findings reinforce the idea that fMRI and NIRS are sensitive to similar underlying hemodynamic changes, and indicate that the proposed weighted BOLD signal is needed for a quantitative comparison of BOLD and NIRS signals.

Brain↗

PubMed2005

Body composition assessment in adults with cystic fibrosis: comparison of dual-energy X-ray absorptiometry with skinfolds and bioelectrical impedance analysis.

OBJECTIVE: We compared body composition measurement in adults with cystic fibrosis (CF) by using non-invasive methods (skinfold thicknesses and bioelectrical impedance analysis [BIA]) with dual-energy X-ray absorptiometry (DXA). METHODS: Seventy-six adults with CF (mean age 29.9 +/- 7.9 y, mean body mass index 21.5 +/- 2.5 kg/m(2)) were studied. Body composition was measured to calculate fat-free mass (FFM) using DXA, the sum of four skinfold thicknesses, and BIA (predictive equations of Lukaski and of Segal). RESULTS: Mean FFM values +/- standard deviation measured using DXA were 54.8 +/- 7.3 kg in men and 41.2 +/- 3.9 kg in women. Mean FFM values measured using BIA/Lukaski were 51.5 +/- 7.8 kg in men and 40.4 +/- 4.9 kg in women (P < 0.0005 for men, not significant for women for comparison with DXA). Mean FFM values measured using BIA/Segal were 54.2 +/- 7.5 kg for men and 44.1 +/- 5.9 kg for women (not significant for men, P < 0.0005 for women for comparison with DXA). Mean FFM values measured using skinfolds were significantly higher than those for FFM with DXA (57.2 +/- 7.2 kg in men, 43.3 +/- 4.3 kg in women, P < 0.0005 for comparison with DXA). The 95% limits of agreement with FFM using DXA were, for men and women, respectively, -8.3 to 1.7 kg and -6.4 to 4.8 kg for BIA/Lukaski, -4.8 to 3.6 kg and -3.1 to 8.9 kg for BIA/Segal, and -2.8 to 7.3 kg and -1.5 to 5.7 kg for skinfolds. CONCLUSION: This study suggests that skinfold thickness measurements and BIA will incorrectly estimate FFM in many adults with CF compared with DXA measurements of FFM. These methods have limited application in the assessment of body composition in individual adult patients with CF.

Absorptiometry, Photon↗

PubMed2004

White matter hyperintensities in subjects with cocaine and opiate dependence and healthy comparison subjects.

The prevalence, severity, and location of white matter signal hyperintensities (WMH) on brain magnetic resonance images were compared in patients with cocaine or opiate dependence and healthy subjects. Patients with cocaine (n=32) and opiate dependence (n=32), whose diagnoses were confirmed with the Structured Clinical Interview for DSM-IV, and age- and sex-matched healthy subjects (n=32) were scanned using a 1.5 T whole body GE magnetic resonance scanner. Axial proton-density and T2-weighted images were obtained as well as fluid-attenuated inversion recovery axial images. The severity of WMH was assessed separately for deep (and insular) and periventricular WMH, using a modified composite version of the rating scales of Fazekas and Coffey. The cocaine-dependent group had greater severity of WMH than the opiate-dependent group, which in turn had greater severity of WMH than the healthy comparison group (odds ratios=2.54 and 2.90, respectively). The cocaine-dependent group had greater lesion severity of deep and insular WMH than the opiate-dependent group and the healthy comparison group (odds ratio>3.25 for deep WMH; odds ratio>4.38 for insular WMH). For periventricular WMH, there were no significant differences between the three groups. The frontal lobes were the predominant locations of WMH in both substance-dependent groups. The greater prevalence and severity of WMH in cocaine-dependent subjects than in opiate-dependent subjects may reflect the fact that cocaine induces more ischemia via vasoconstriction than opiates. Also, there was a trend for lower WMH severity in substance-dependent women relative to the healthy comparison group, possibly due to estrogen's protective effect against cerebrovascular accidents.

Adult↗

PubMed2005

Interannual variability of surface heat fluxes in the Adriatic Sea in the period 1998-2001 and comparison with observations.

Surface heat fluxes of the Adriatic Sea are estimated for the period 1998-2001 through bulk formulae with the goal to assess the uncertainties related to their estimations and to describe their interannual variability. In addition a comparison to observations is conducted. We computed the components of the sea surface heat budget by using two different operational meteorological data sets as inputs: the ECMWF operational analysis and the regional limited area model LAMBO operational forecast. Both results are consistent with previous long-term climatology and short-term analyses present in the literature. In both cases we obtained that the Adriatic Sea loses 26 W/m2 on average, that is consistent with the assessments found in the literature. Then we conducted a comparison with observations of the radiative components of the heat budget collected on offshore platforms and one coastal station. In the case of shortwave radiation, results show a little overestimation on the annual basis. Values obtained in this case are 172 W/m2 when using ECMWF data and 169 W/m2 when using LAMBO data. The use of either Schiano's or Gilman's and Garrett's corrections help to get even closer values. More difficult is to assess the comparison in the case of longwave radiation, with relative errors of an order of 10-20%.

Hot Temperature↗

PubMed2006

The efficacy comparison of ibuprofen, acetaminophen-codeine, and placebo premedication therapy on the depth of anesthesia during treatment of inflamed teeth.

The purpose of this study was to elucidate whether premedication therapy with acetaminophen-codeine or ibuprofen is able to increase the depth of anesthesia in inflamed teeth. Sixty patients with the diagnosis of irreversible pulpitis in 1 mandibular tooth requiring root canal therapy (RCT) were selected. Two other teeth in the same quadrant were selected as controls. An electric pulp tester (EPT) was used to evaluate pulp sensitivity at the baseline and after drug administration and anesthesia injection. The subjects were divided into 3 groups randomly, and in each group 1 of the 3 drugs including acetaminophen-codeine, ibuprofen, and placebo were administered 1 hour before anesthesia delivery. After 1 hour, anesthesia was injected and after a waiting period, the EPT measurement was recorded. The reversed EPT scale was used to evaluate the depth of anesthesia achieved during RCT. Data were analyzed to statistically compare the results before and after intervention in cases and controls of each group and among different groups. Significanly lower tooth sensitivity levels (TSLs) were observed after intervention in acetaminophen-codeine and ibuprofen groups, which was more significant in the ibuprofen group. The comparison of inflamed teeth TSLs in the acetaminophen-codeine group and the placebo group after anesthesia and drug administration showed significant differences (P = .001). This comparison between ibuprofen and placebo groups also showed significant differences (P approximately 0). Also, significantly lower TSL of inflamed teeth was observed in the ibuprofen group in comparison with the acetaminophen-codeine group (P = .002). This study reflected preoperative administration of ibuprofen, if not contraindicated, as a drug of choice 1 hour before local anesthesia injection as an effective method for achieving a deep anesthesia during RCT of teeth with irreversible pulpitis.

Acetaminophen↗

PubMed2002

Basal ganglia volumes in first-episode schizophrenia and healthy comparison subjects.

BACKGROUND: Previous studies suggest that dysfunction of cortico-striato-pallido-thalamic (CSPT) circuitry may be involved in the pathophysiology of schizophrenia but also show that basal ganglia structure is highly plastic and may be influenced by antipsychotic treatments. Controversy remains about whether basal ganglia pathology can be detected in vivo among treatment-naïve patients. We conducted a magnetic resonance imaging (MRI) study to examine basal ganglia structures and the limbic forebrain in first episode schizophrenia and healthy comparison subjects. METHODS: Fifty-one patients with first-episode schizophrenia and 28 healthy comparison subjects participated in the study. A high-resolution, special contrast (white matter nulling) MRI sequence was used to measure the caudate nucleus, nucleus accumbens, putamen, and subcommissural limbic forebrain. RESULTS: Volumes of the basal ganglia regions of interest (adjusted for total brain volume and age) did not differ significantly between the groups. Age correlated significantly with caudate and putamen volumes bilaterally in the healthy comparison group, but not among patients. CONCLUSIONS: The findings suggest that there are no volumetric abnormalities in basal ganglia before treatment in first-episode schizophrenia. The lack of a negative correlation between age and striatal volume among patients may implicate illness-associated factors that alter normal age-related changes in basal ganglia size.

Adult↗

PubMed1997

P50 suppression among schizophrenia and normal comparison subjects: a methodological analysis.

The present report investigated the relationship between P50 suppression and habituation among 20 schizophrenia and 20 normal comparison subjects. Subjects were presented with clicks delivered over headphones in a S1-S2 paradigm (clicks were separated by 500 msec; average intertrial interval was 8 sec). There were 60 total trials; the data were analyzed separately for the first and second 30 trials. The groups did not differ either on the number of usable trials or on the morphology of their P50 responses. Consistent with previous reports, schizophrenia patients demonstrated deficient P50 suppression. The overall suppression effect was not due to a group difference on S1 P50 amplitudes, but was associated with schizophrenia patients having smaller S1-S2 P50 amplitude difference scores than normal comparison subjects. Furthermore, the suppression effect appears to be more pronounced during the first than during the second block of trials. Thus, it may be important to evaluate changes in P50 responses over time among schizophrenia and normal comparison subjects.

Arousal↗

PubMed1997

Impaired attention-dependent augmentation of MMN in nonparanoid vs paranoid schizophrenic patients: a comparison with obsessive-compulsive disorder and healthy subjects.

Mismatch negativity (MMN), in the deviant-minus-standard event-related potential (ERP) difference-waveform, may represent a working memory trace of the tone difference. Most but not all studies find MMN reduced in schizophrenic patients. This report investigates if differences may be attributable to experimental condition (diffuse vs focused attention), component identification (N1-like vs N2-like), topographic distribution, and clinical condition (with/without paranoid-hallucinatory symptoms, PH/NP). Comparisons were made for 12 PH, 12 NP schizophrenic patients with 13 obsessive compulsive and 25 normal control subjects. Frontal MMN reduction in schizophrenics largely resulted from an absence of an increase in focused attention conditions as in comparison groups. But there was a marked temporal activity locus in NP patients. These features were not reflected in other components except for a visible but nonsignificant N1-like temporal locus in NP patients. Further, schizophrenic patients did not show an increase in late positivity with focused attention like the comparison groups. The results show that so-called automatic processing deficits (amount and locus of MMN) are best seen in situations requiring the activation of controlled attentional processes. It is suggested that impaired processing of irrelevant stimuli and reduced frontal MMN in NP patients may reflect reduced dopaminergic responsivity.

Adolescent↗