A new method for the estimation of the onset of the lateralized readiness potential (LRP)

The aim of this work was to develop a new method for the estimation of the onset of the lateralized readiness potential (LRP). In contrast to the known methods that use only restricted data segments for estimation, the proposed segmented regression (SR) method employs the LRP trace from the stimulus onset to the LRP peak. Comparison of the SR with two other methods, done with both simulated and real data, shows that the SR method yields a relatively unbiased absolute onset time that is not affected by different LRP gradients before and after the onset. Moreover, the SR estimator proved to be quite sensitive to subtle onset differences across conditions.     

Reid’s Account of the “Geometry of Visibles”: Some Lessons from Helmholtz

Drawing on work done by Helmholtz, I argue that Reid was in no position to infer that objects appear as if projected on the inner surface of a sphere, or that they have the geometric properties of such projections even though they do not look concave towards the eye. A careful consideration of the phenomena of visual experience, as further illuminated by the practice of visual artists, should have led him to conclude that the sides of visible appearances either look straight, in which case their angles appear to approximate Euclidean measures, or their angles do not appear to approximate Euclidean measures for straight line figures, in which case their sides do not look straight.     

The Role of Gender in Worry and Efforts to Cope during Stressful Waiting Periods

Sex Roles - Waiting for personally significant news is a near-universal experience, but people differ in how they cope with these acute moments of uncertainty. The present study examined whether...     

Response selection and response execution in task switching: evidence from a go-signal paradigm

The present study used a go/no-go signal delay (GSD) to explore the role of response-related processes in task switching. A go/no-go signal was presented at either 100 ms or 1,500 ms after the stimulus. Participants were encouraged to use the GSD for response selection and preparation. The data indicate that the opportunity to select and prepare a response (i.e., long GSD) resulted in a substantial reduction of task-shift costs (Experiment 1) and n-2 task-repetition costs (i.e., backward inhibition; Experiment 2) in the current trial. These results suggest that interference from the preceding trial can be resolved during response selection and preparation. Furthermore, the shift costs and the n-2 repetition costs after no-go trials with long GSD (i.e., response selection but no execution) were markedly smaller than after go trials. These findings suggest that the interference that gives rise to shift costs and n-2 repetition costs is related not solely to response selection but also to response execution. Thus, the present study demonstrates dissociable contributions of response selection and response execution to interference effects in task switching.     

ERP components in Go/Nogo tasks and their relation to inhibition.

In visual Go/Nogo tasks the ERP usually shows a frontal negativity after Nogo stimuli ("Nogo-N2"), which possibly reflects an inhibition process. However, the Nogo-N2 appears to be very small after auditory stimuli, which is evidence against the inhibition hypothesis. In the present study we tested this hypothesis by evaluating performance differences between subjects. Assuming that for Ss with a high false alarm rate the inhibition process is weakened and/or delayed, they should reveal a smaller and/or later Nogo-N2 than Ss with a low false alarm rate. This prediction was confirmed, which supports the inhibition hypothesis. However, the Nogo-N2 was again much smaller and had a different topography after auditory than after visual stimuli despite similar performance in both modalities. This modality asymmetry was explained by assuming that the inhibitory mechanism reflected in the Nogo-N2 is located at a pre-motor rather than at the motor level. In the second part of the study we compared the Nogo-N2 with a similar phenomenon, the error negativity (Ne), which occurs in trials with commission errors (false alarms). Earlier work suggests that the Ne is a correlate of error detection or inhibition. This raises the possibility that the Ne is a delayed Nogo-N2, i.e., the Ne may reflect a late and hence unsuccessful attempt to inhibit the response after a nontarget. However, the Ne amplitude showed no difference between performance groups and stimulus modalities, as found for the Nogo-N2. Moreover, Ne and Nogo-N2 had different scalp topographies. This suggests that different mechanisms and generators underlie the Ne and the Nogo-N2.     

Temporal dynamics of interference in Simon and Eriksen tasks considered within the context of a dual-process model

Behavioral and brain potential measures were employed to compare interference in Eriksen and Simon tasks. Assuming a dual-process model of interference elicited in speeded response tasks, we hypothesized that only lateralized stimuli in the Simon task induce fast S–R priming via direct unconditional processes, while Eriksen interference effects are induced later via indirect conditional processes. Delays to responses for incongruent trials were indeed larger in the Eriksen than in the Simon task. Only lateralized stimuli in the Simon task elicited early S–R priming, maximal at parietal areas. Incongruent flankers in the Eriksen task elicited interference later, visible as a lateralized N2. Eriksen interference also elicited an additional component (N350), which accounted for the larger behavioral interference effects in the Eriksen task. The findings suggest that interference and its resolution involve different processes for Simon and Eriksen tasks.     

Predictors of PTSD Improvement with Cognitive/Exposure Group Interventions in Operation Enduring Freedom/Operation Iraqi Freedom Female Veterans

Predictors of successful PTSD outcome have been examined through individually delivered treatments. We examined predictors using a group protocol with cognitive, exposure, and skills modules. Assessments included self-report and interview (CAPS, SCID-I/II) measures at baseline, post, and six months; treatment was a 16-week, three-member group for 32 OEF/OIF women Veterans. A regression analysis showed major depressive disorder and no baseline psychiatric medication predicted PTSD improvement. PTSD improvement predicted fewer outpatient medical visits at follow-up. The results supported past research and challenged other findings (e.g., sexual assault predicts less improvement). An additional unique contribution was examining predictors in a group treatment format.     

Psychosocial Adjustment and Substance Use of Cambodian and Vietnamese Immigrant Youth

Southeast Asians living in the United States are a unique Asian immigrant population. They are considered one of the "newer" Asian immigrant groups, tend to be less affluent compared with their East and South Asian counterparts, and are steadily growing in number (U.S. Bureau of the Census, 2000). Unfortunately, few studies exist specifically about Southeast Asian immigrants. The lack of studies, coupled with the community's growing mental health issues, suggests the need for increased research on this population. This study contributes to the literature by examining the extent to which identification with Vietnamese or Cambodian culture, peer relationships, and coping behaviors affect substance use among Cambodian and Vietnamese immigrant youth. A sample of 102 participants, age 12-18 years, completed self-report measures regarding these variables. Overall, results indicate that identification with one's culture of origin and coping behaviors moderate the relationship between deviant peer association and substance use. Results are discussed within a contextual model of problem behavior among Southeast Asian youth.