Baseline Bias Research Articles

Automatic Versus Effortful Influences in the Processing of Traumatic Material in Acute Stress Disorder

The defining feature of the acute stress disorder (ASD) diagnosis is the emphasis on dissociative symptoms. The dissociation model posits that dissociative reactions are automatically activated in response to traumatic exposure, suggesting that the cognitive processing of individuals with ASD is characterized by automatic processes. In the present study, Jacoby’s (1991) process-dissociation model was applied to investigate the extent to which both automatic and effortful processing are involved in the processing of traumatic material in ASD. We employed a computer-based version of this paradigm to compare trauma-exposed participants with (n = 13) and without (n = 13) ASD. The results indicated no evidence for a greater contribution of automatic influences to the processing of trauma-related information in the ASD group. Overall participants demonstrated a baseline bias towards the completion of trauma-related word stems, irrespective of group status. Severity of psychopathology was negatively correlated with estimates of the contribution of both automatic and strategic processing of positive material. The findings suggest that ASD participants are not characterized by distinctive automatic information processing styles. Results are discussed in terms of the applicability of the process dissociation paradigm with traumatized populations.

Cognitive Bias in Panic Disorder: A Process Dissociation Approach to Automaticity

We applied a variant of Jacoby's (1991) process dissociation procedure to parse the relative contributions of automatic and controlled processes to word-stem completion performance involving threatening, positive, and neutral material in patients with panic disorder and healthy control participants. Contrary to prediction, processing of threatening (relative to nonthreatening) information in panic disorder was not disproportionately influenced by automatic processing. We found limited evidence, however, that panic patients exhibit a baseline bias for completing stems relevant to threat relative to nonthreat stems, perhaps indicating a proneness to engage in self-generated priming of threat material.

Determination of Hemoglobin Saturation in Patients With Acute Sickle Chest Syndrome: A Comparison of Arterial Blood Gases and Pulse Oximetry

To evaluate three different methods of measuring oxygen saturation in patients suffering from acute sickle chest syndrome. A prospective, descriptive study of 9 months' duration. A tertiary care university hospital. Adult patients with acute sickle chest syndrome scheduled to undergo RBC exchange transfusion. None. Baseline hemoglobin oxygen saturation was determined simultaneously by (1) calculation based on PaO2 and an oxyhemoglobin dissociation curve algorithm, (2) co-oximetry, and (3) pulse oximetry. These same measures were repeated after exchange transfusion. Baseline and postexchange hemoglobin electrophoresis was performed in all patients. Baseline calculated saturation overestimated true saturation (determined by co-oximetry) with a baseline mean bias (co-oximetry minus calculated saturation) of -6.78 +/- 2.63% (95% confidence interval for bias: -8.37% to -5.19%). Pulse oximetry was not different than co-oximetry at baseline with a baseline bias of +1.86 +/- 3.25% (95% confidence interval: -0.1% to 3.82%). After exchange transfusion, there was no bias between either co-oximetry and calculated saturation (mean difference: -0.17 +/- 1.31% [95% confidence interval: -0.95% to 0.61%]), or co-oximetry and pulse oximetry (mean difference: +0.3 +/- 1.53% [95% confidence interval: -0.62% to 1.22%]). Calculated saturation overestimates true saturation during acute sickle chest syndrome. This discrepancy abates after exchange transfusion. Pulse oximetry more closely follows co-oximetry than does calculated saturation during acute sickle chest syndrome.

A biased view of attention.

A biased view of attention.

Explicit and implicit memory bias in panic disorder with agoraphobia

Thirty patients with a diagnosis of panic disorder with agoraphobia and 30 normal controls were compared on explicit memory (cued recall) and implicit memory (word stem completion) for positive, neutral, social threat, and physical threat words. The panic patients showed an explicit memory bias, but no implicit memory bias, for physical threat words. The index of explicit memory bias for physical threat words was found to correlate with anxiety sensitivity and degree of agoraphobic fear and avoidance. The index of baseline bias for threat words on the word completion task, on the other hand, correlated with trait anxiety. Although there were no correlations between explicit and implicit memory bias for physical threat words, explicit memory bias for physical threat words correlated with explicit memory bias indexes for positive words and social threat words. The results are discussed in terms of the functional role of an explicit memory bias for physically threatening events in panic disorder. The negative results on implicit memory bias are discussed in relation to earlier studies, the use of different implicit memory tasks, and the role of baseline bias on implicit memory tasks. Finally, the hypothesis is suggested that explicit and implicit memory bias for emotional information may represent two different styles of information processing, which serve as vulnerability factors for different emotional disorders.

Explicit and implicit memory bias in social phobia. The role of subdiagnostic type

Fourty-five patients with social phobia and 45 normal controls were compared on explicit memory (cued recall) and implicit memory (word stem completion) for positive, neutral, social threat, and physical threat words. Although there were no significant differences between the social phobics and the normal controls, the subgroup of patients with non-generalized social phobia showed an implicit memory bias for social threat words. The results are discussed in terms of a critical analysis of the concept of implicit memory bias, which is operationalized as the difference between a bias on primed and unprimed words, and where the latter represents a “baseline bias”. In the present study, this baseline word completion bias for social threat words showed a strong negative correlation ( r = − 0.72) with the implicit memory bias for social threat words, and showed positive correlations with several psychopathology-related measures among the social phobics. It is suggested that future research should consider results on both implicit memory bias and its corresponding baseline bias. The possibility is discussed that implicit memory bias and baseline bias may serve as indexes of externally and internally generated priming effects, and that the relative contributions of external and internal priming may differ in different subtypes of social phobia.

Nicotine conditions place preferences after intracerebral administration in rats

A single-trial place conditioning procedure, one treatment and one non-treatment during two daily conditioning sessions followed by a single test session on the 3rd day, was used to examine the place conditioning effects of intracerebrally administered nicotine. In the first series of experiments, Sprague-Dawley male rats were implanted unilaterally with guide cannulas aimed at the lateral ventricle. After 1 week, rats received either "treatment" (nicotine in 2 microliters phosphate buffer or 2 microliters of buffer alone) or "no treatment" (no injections) before being placed in the black or white compartment of a three-compartment place-conditioning apparatus for 20 min. The next day the rats received the opposite treatment before being conditioned in the opposite compartment. On day 3, animals had free access to the entire apparatus for 15 min and the time spent in each compartment was recorded automatically. Even though the rats exhibited a baseline bias for the black compartment, intracerebroventricular nicotine induced positive place preferences relative to buffer control, i.e. if treatments were paired with the black compartment, nicotine enhanced the preference for the black compartment, and if the treatments were paired with the white compartment, nicotine induced a preference for the white compartment. In addition, the nicotine-induced preference response was antagonized by the co-intraventricular administration of mecamylamine. In a second series of experiments, animals were implanted unilaterally with guide cannulas aimed at the pendunculopontine tegmental nucleus of the mesopontine tegmentum. Nicotine microinjection, 1.2-18.5 nmol in 0.5 microliter buffer, induced a dose-dependent positive place preference response.(ABSTRACT TRUNCATED AT 250 WORDS)

Estimation of travel times for source location in a laterally heterogeneous Earth

A method is presented to obtain travel times from estimates of tectonically regionalized P-wave tau functions and slowness-dependent source and receiver corrections (Tralli and Johnson). A quadratic programming algorithm interpolates the tau estimates constrained by the analytical properties of tau and the statistical uncertainties. The regionalized travel-time estimates are used to locate seismic sources in the epicentral distance range 15–95°. Since all the information on lateral velocity variations is contained in the tau functions, seismic sources in a laterally heterogeneous Earth are located without explicitly defining a laterally varying velocity model. The formulation is efficient in that the travel-time estimates and corrections are obtainable for any source and receiver pair on the globe and requires minimal computation time. The P travel-time data are provided by the Bulletin of the ISC. Twenty-eight disclosed nuclear explosions at Nevada Test Site (NTS) allow estimation of a travel-time baseline bias. Azimuthal corrections for NTS events are also obtained. Nuclear explosions at NTS are then located, as are events in Eastern Kazakh and Novaya Zemlya in the Soviet Union, and in the Tuamotu Archipelago in French Polynesia. Three earthquakes along the San Andreas fault zone in west central California are also relocated for comparison with hypocentral parameters provided by local seismographic networks. All events are also located using the Jeffreys-Bullen P Tables and PREM (Dziewonski and Anderson) with a set of azimuthal station corrections (Dziewonski). A comparison of the reduction in sample variances of travel-time residuals provides a measure of the ability of tectonically regionalized tau functions to characterize lateral variations in mantle and crustal P velocities. Mean epicentral mislocations for NTS events are about 3 km whereas mislocations using J-B and PREM are about 7 km. For NTS and particularly Eastern Kazakh, the tau formulation yields consistently smaller sample variances, with a mean reduction of 30% compared to using J-B and 15% compared to using PREM.