Modeling violations of the race model inequality in bimodal paradigms: co-activation from decision and non-decision components

The redundant-signals paradigm (RSP) is designed to investigate response behavior in perceptual tasks in which response-relevant targets are defined by either one or two features, or modalities. The common finding is that responses are speeded for redundantly compared to singly defined targets. This redundant-signals effect (RSE) can be accounted for by race models if the response times do not violate the race model inequality (RMI). When there are violations of the RMI, race models are effectively excluded as a viable account of the RSE. The common alternative is provided by co-activation accounts, which assume that redundant target signals are integrated at some processing stage. However, “co-activation” has mostly been only indirectly inferred and the accounts have only rarely been explicitly modeled; if they were modeled, the RSE has typically been assumed to have a decisional locus. Yet, there are also indications in the literature that the RSE might originate, at least in part, at a non-decisional or motor stage. In the present study, using a distribution analysis of sequential-sampling models (ex-Wald and Ratcliff Diffusion model), the locus of the RSE was investigated for two bimodal (audio-visual) detection tasks that strongly violated the RMI, indicative of substantial co-activation. Three model variants assuming different loci of the RSE were fitted to the quantile reaction time proportions: a decision, a non-decision, and a combined variant both to vincentized group as well as individual data. The results suggest that for the two bimodal detection tasks, co-activation has a shared decisional and non-decisional locus. These findings point to the possibility that the mechanisms underlying the RSE depend on the specifics (task, stimulus, conditions, etc.) of the experimental paradigm

Response Selection modulates Visual Search Within and Across Dimensions.

In feature search tasks, uncertainty about the dimension on which targets differ from the nontargets hampers search performance relative to a situation in which this dimension is known in advance. Typically, these cross-dimensional costs are associated with less efficient guidance of attention to the target. In the present study, participants either had to perform a feature search task or had to perform a nonsearch task, that is, respond to a target presented without nontargets. The target varied either in one dimension or across dimensions. The results showed similar effects both in search and nonsearch conditions: Preknowledge of the target dimension gave shorter response times than when the dimension was unknown. Similar results were found using a trial-by-trial cueing. It is concluded that effects that typically have been attributed to early top-down modulation of attentional guidance may represent effects that occur later in processing. Copyright 2005 by the American Psychological Association

Sequential modulations of the Simon effect depend on episodic retrieval

Sequential modulations of conflict effects, like the reduction of the Simon effect after incompatible trials, have been taken to reflect the operation of a proactive control mechanism commonly called conflict monitoring. However, such modulations are often contaminated by episodic effects like priming and stimulus-response feature integration. It has previously been observed that if the episodic representation of a conflicting trial is altered by rotating the stimulus framing 180° around its axis, the subsequent “conflict adaptation” pattern is eliminated. In Experiment 1, we replicate the findings and provide the basic episodic interpretation. In Experiment 2, we extend the framework to include rotations of 90°, and verify that the episodic effects generalize to scenarios of neutral compatibility. Finally, in Experiment 3, we add complete, 360° rotations, and show that the episodic manipulation by itself does not eliminate the conflict adaptation patterns – as long as conditions favor episodic retrieval. The experiments are argued to demonstrate that an episodic account of the conflict adaptation effect can most parsimoniously account for the behavioral effects without relying on higher order cognition. Accordingly, we conclude that conflict adaptation can be understood either as critically depending on episodic retrieval, or alternatively reflecting only episodic retrieval itself

Neural Correlates of Visual Aesthetics – Beauty as the Coalescence of Stimulus and Internal State

How do external stimuli and our internal state coalesce to create the distinctive aesthetic pleasures that give vibrance to human experience? Neuroaesthetics has so far focused on the neural correlates of observing beautiful stimuli compared to neutral or ugly stimuli, or on neural correlates of judging for beauty as opposed to other judgments. Our group questioned whether this approach is sufficient. In our view, a brain region that assesses beauty should show beauty-level-dependent activation during the beauty judgment task, but not during other, unrelated tasks. We therefore performed an fMRI experiment in which subjects judged visual textures for beauty, naturalness and roughness. Our focus was on finding brain activation related to the rated beauty level of the stimuli, which would take place exclusively during the beauty judgment. An initial whole-brain analysis did not reveal such interactions, yet a number of the regions showing main effects of the judgment task or the beauty level of stimuli were selectively sensitive to beauty level during the beauty task. Of the regions that were more active during beauty judgments than roughness judgments, the frontomedian cortex and the amygdala demonstrated the hypothesized interaction effect, while the posterior cingulate cortex did not. The latter region, which only showed a task effect, may play a supporting role in beauty assessments, such as attending to one's internal state rather than the external world. Most of the regions showing interaction effects of judgment and beauty level correspond to regions that have previously been implicated in aesthetics using different stimulus classes, but based on either task or beauty effects alone. The fact that we have now shown that task-stimulus interactions are also present during the aesthetic judgment of visual textures implies that these areas form a network that is specifically devoted to aesthetic assessment, irrespective of the stimulus type

IMPACT OF MORNING STIFFNESS, EDUCATION, AND AGE ON THE FUNCTIONAL STATUS OF PATIENTS WITH RHEUMATOID ARTHRITIS

Svrha istraživanja bila je proučiti i usporediti odnos izmeđ funkcionalnog statusa i trajanja jutarnje zakočenosti u šakama s obzirom na dob, razinu obrazovanja i spol u bolesnika s reumatoidnim artritisom (RA). Istražena je povezanost tih čimbenika u odnosu na postojanje reumatoidnog faktora, odnosno serološki status. Ova retrospektivna studija provedena je u 250 bolesnika s klasičnim oblikom RA (186 žena, 64 muškarca). Ispitanici su bili u dobi između 25 i 60 godina, (x=49.96) s trajanjem bolesti od jedne do 27 godina (x =6.41) i nisu ispunjavali revidirane dijagnostičke kriterije ACR-a (American College of Rheumatology – 1987). Svi ispitanici pripadali su II. i III. funkcionalnom razredu prema Steinbrockerovoj klasifi kaciji. Odnos između funkcionalnih razreda i odabranih varijabli (trajanje jutarnje ukočenosti u rukama, spol, dob i stupanj obrazovanja) u odnosu na serostatus mjeren je point-biserijalnim koefi cijentom korelacije. Nađena je pozitivna, iako niska korelacija između trajanja jutarnje ukočenosti i funkcionalnih klasa [(r=0.10, y=0.00x 2.37, p> 0.05) seronegativni, (r=0.12, y=0.00x 2.30, p>0.05) seropozitivni]. Visoke pozitivne vrijednosti dobivene su pri određivanju koefi cijenta linearne korelacije između trajanja bolesti i funkcionalnih klasa (p<0.01). Također su visoke vrijednosti dobivene za koefi cijent korelacije između dobi i funkcionalnih klasa [(r=0.29, p<0.01) seronegativni, (r=0.47, p<0.01) seropozitivni]. Slabije obrazovani bolesnici bili su znatno više zastupljeni u III. funkcionalnom razredu [23 (50%) seronegativni, 19 (42.2%) seropozitivni] nego u II. funkcionalnom razredu [16 (20.3%) seronegativni, 22 (27.5%) seropozitivni]. Zaključno, prema ovoj studiji bolesnika s reumatoidnim artritisom dulje trajanje jutarnje zakočenosti bilo je povezano sa stupnjem funkcionalne nesposobnosti. Funkcionalna nesposobnost bila je povećana s trajanjem bolesti, ovisna o dobi i obrazovnoj razini te je izraženija u starijoj dobi, bez obzira na RA serološki status. U odnosu na serološki status i spol, razlike nisu znatne.Th e purpose of this study was to explore the relationship between disability status and duration of morning stiff ness in hands with regard to age, level of education, and gender in patients with rheumatoid arthritis (RA). Also, the authors wanted to investigate this relationship with regard to the presence of rheumatoid factor, i.e., the serological status. A retrospective study was conducted in 250 patients with the classic form of RA (186 females, 64 males, mean age Xb = 49.96 years, range 25-60 years, disease duration 1-27 years, Xb = 6.41) previously diagnosed with RA according to the ACR (American College of Rheumatology 1987 criteria). All patients were in Steinbrocker functional classes II and III. Th e probability level was expressed by p < 0.01 and p < 0.05. Th e relationship between the variables was measured by point-biserial correlation. Th e correlation between duration of morning stiff ness and functional class was positive but low [(r = 0.10, y = 0.00x + 2.37, p > 0.05) seronegative, (r = 0.12, y = 0.00x + 2.30, p > 0.05) seropositive]. High positive values were obtained for the linear correlation coeffi cient between duration of the disease and functional class (p < 0.01). Also, high values were obtained regarding the coeffi cient of correlation between age and functional class [(r = 0.29, p < 0.01) seronegative, (r = 0.47, p < 0.01) seropositive]. Uneducated patients were signifi cantly more represented in functional class III [23 (50%) seronegative, 19 (42.2%) seropositive] than in functional class II [16 (20.3%) seronegative, 22 (27.5%) seropositive]. In conclusion, in this study of patients with rheumatoid arthritis, increased duration of morning stiff ness was associated with functional disability. Functional disability increased with the duration of the disease, depended on age and educational level, and was more pronounced in older age, regardless of RA serological status. With regard to serological status and sex, the diff erences were non-signifi cant

Task-related modulation of anterior theta and posterior alpha EEG reflects top-down preparation

<p>Abstract</p> <p>Background</p> <p>Prestimulus EEG alpha activity in humans has been considered to reflect ongoing top-down preparation for the performance of subsequent tasks. Since theta oscillations may be related to poststimulus top-down processing, we investigated whether prestimulus EEG theta activity also reflects top-down cognitive preparation for a stimulus.</p> <p>Results</p> <p>We recorded EEG data from 15 healthy controls performing a color and shape discrimination task, and used the wavelet transformation to investigate the time course and power of oscillatory activity in the signals. We observed a relationship between both anterior theta and posterior alpha power in the prestimulus period and the type of subsequent task.</p> <p>Conclusions</p> <p>Since task-differences were reflected in both theta and alpha activities prior to stimulus onset, both prestimulus theta (particularly around the anterior region) and prestimulus alpha (particularly around the posterior region) activities may reflect prestimulus top-down preparation for the performance of subsequent tasks.</p