Benefits of multinomial processing tree models with discrete and continuous variables in memory research: an alternative modeling proposal to Juola et al. (2019)

Signal detection theory (SDT) and two-high threshold models (2HT) are often used to analyze accuracy data in recognition memory paradigms. However, when reaction times (RTs) and/or confidence levels (CLs) are also measured, they usually are analyzed separately or not at all as dependent variables (DVs). We propose a new approach to include these variables based on multinomial processing tree models for discrete and continuous variables (MPT-DC) with the aim to compare fits of SDT and 2HT models. Using Juola et al.'s (2019, Memory & Cognition, 47[4], 855-876) data we have found that including CLs and RTs reduces the standard errors of parameter estimates and accounts for interactions among accuracy, CLs, and RTs that classical versions of SDT and 2HT models do not. In addition, according to the simulations, there is an increase in the proportion of correct model selections when relevant DV are included. We highlight the methodological and substantive advantages of MPT-DC in the disentanglement of contributing processes in recognition memory.

Progressive attenuation of visual global precedence across healthy aging and Alzheimer's disease

In the perception of Navon hierarchical stimuli (e.g., large letters made up of small letters), young adults identify large letters faster than small ones (known as 'global advantage') and identify more slowly small letters when they form a different (or incongruent) large letter (known as 'unidirectional global interference'). Since some global/local perceptual alterations might be occurring with aging, we investigated whether these effects vary across healthy aging and Alzheimer's disease (AD). Here, the Navon letter task was administered to 26 healthy elderly (HE), 21 adults with mild cognitive impairment (MCI), and 26 adults with AD. The same task was administered 1 year later, and different neuropsychological variables were incorporated into the analyses. The cross-sectional study revealed no global advantage but did reveal both global and local interferences in all groups when response times were analyzed. Regarding discrimination sensitivity, HE showed unidirectional global interference, while AD displayed better discrimination of local than global letters in the incongruent condition, which denotes less interference by global distractors than by local ones. The longitudinal study revealed that 1 year later the participants with MCI showed a slowdown in inhibiting local distractors in the global task, revealing a certain bias toward focus in their attention on small stimuli. The elders with AD reflected a generalized slowing of their responses with a clear bias toward local analysis of stimuli, also suggested by their better discrimination in the incongruent local task at the second moment of assessment. Furthermore, all response timing measures in the Navon task were correlated with several neuropsychological indexes of highly sensitive neuropsychological tests, suggesting that performance in this task may also have a potential diagnostic value for differentiating typical from atypical cognitive aging. All these results support the need for a multidomain approach to define neuropsychological markers of progression toward AD, including visual perceptual organization evaluated via measures of performance quality.

Both cute and threatening images drive narrowing of attention in men and women

Appraisal theories of emotion sustain that stimuli containing high biological relevance preferentially capture our attention, regardless of their valence. In this work, we study the priming effect of both cute and threatening pictures on global/local visual processing. Seventy-eight males and 168 females in different menstrual cycle phases performed the global/local Navon letter task immediately after observing cute (infants and baby animals), threatening (animals in aggressive poses) or neutral pictures. Hierarchical stimuli were made up of global and local letters that could be either congruent (e.g. global H, local_H) or incongruent (e.g. global H, local_S). While we observed no interaction between affective primes and sex/menstrual cycle phase, each of these variables did have an independent effect on the global/local task. Thus, letter identification was significantly slower in the global task (only) after cute vs. neutral primes. Relevantly, the local-minus-global RT index revealed an attentional narrowing after both cute and threatening primes (vs. neutral primes) in incongruent trials. As for sex effects, a facilitation of global vs. local processing was observed in both sexes. However, women registered slower RTs than men, whereas women in the luteal phase showed faster RTs than those in follicular phase in the local task. This suggests that women, mainly those in their luteal menstrual phase, tend to rely on a more analytical style of processing while attending to hierarchical stimuli. Most importantly, stimuli containing high biological significance drive narrowing of the attentional focus in global/local visual processing, especially in conditions of higher attentional demand.

Forest Before Trees: Letter Stimulus and Sex Modulate Global Precedence in Visual Perception

The global precedence effect (GPE), originally referring to processing hierarchical visual stimuli composed of letters, is characterised by both global advantage and global interference. We present herein a study of how this effect is modulated by the variables letter and sex. The Navon task, using the letters “H” and “S,” was administered to 78 males and 168 females (69 follicular women, 52 luteal women, and 47 hormonal contraceptive users). No interaction occurred between the letter and sex variables, but significant main effects arose from each of these. Reaction times (RTs) revealed that the letter “H” was identified more rapidly in the congruent condition both in the global and the local task, and the letter “S” in the incongruent condition for the local task. Also, although RTs showed a GPE in both males and females, males displayed shorter reaction times in both global and local tasks. Furthermore, luteal women showed higher d’ index (discrimination sensitivity) in the congruent condition for the local task than both follicular women and hormonal contraceptive users, as well as longer exploration time of the irrelevant level during the global task than males. We conclude that, according to the linear periodicity law, the GPE is enhanced for compound letters with straight vs. curved strokes, whereas it is stronger in males than in females. Relevantly, luteal phase of the menstrual cycle seems to tilt women to rely on finer grained information, thus exhibiting an analytical processing style in global/local visual processing.

Patient concerns regarding chronic hepatitis C infections

Counselling of patients with chronic hepatitis C infections is often limited to discussions regarding how the virus is transmitted and what can be done to decrease the risk of transmission to others. The purpose of the present study was to document the principal concerns of newly diagnosed and follow-up patients with chronic hepatitis C, and thereby enhance counselling strategies and content. Seventy newly diagnosed and 115 follow-up patients with chronic hepatitis C virus (HCV) infection were initially asked in an open-ended manner (volunteered concerns) and then to prioritize from a prepared list of seven potential concerns (prioritized concerns), to identify those concerns that were of utmost importance to them. The most common volunteered concerns of newly diagnosed patients in decreasing order were: disease progression (27%), premature death (19%), infecting family members (13%), side-effects of treatment (11%) and miscellaneous others. In decreasing order, prioritized concerns included: infecting family members, development of liver cancer, infecting others, development of cirrhosis, social stigma of having liver disease, need for liver transplant and loss of employment. The principal volunteered and prioritized concerns of follow-up patients were similar to those of newly diagnosed patients. Volunteered and prioritized concerns were relatively consistent across the different genders, age groups, ethnic backgrounds, education level, marital status, employment, modes of viral acquisition and in the case of follow-up patients, duration of follow-up. These results indicate that health care providers who focus counselling efforts exclusively on viral transmission are unlikely to address other important concerns of newly diagnosed and follow-up patients with chronic HCV infection.

Serological studies of West Nile virus in a liver transplant population

BACKGROUND

Solid organ transplant populations are at increased risk for serious clinical manifestations of West Nile virus (WNV) infection.

OBJECTIVE

To monitor liver transplant recipients during the 2003 WNV season in Manitoba and to identify incidence, clinical presentation and serology.

METHODS

Serial blood specimens were obtained from adult patients followed at the liver transplant outpatient clinic between May 2003 and October 2003. Studies for WNV infection included immunoglobulin (Ig) G and IgM enzyme immunoassay (EIA), hemagglutination inhibition (HI), plaque reduction neutralization test and reverse transcriptase-polymerase chain reaction.

RESULTS

None of the 79 patients had clinical presentations suggestive of WNV infection. On testing of the final serum specimen obtained, 14 patients (18%) had positive IgG anti-WNV by EIA and six patients (7%) had indeterminate IgG anti-WNV by EIA, although all were negative by IgM EIA. Four (20%) of the EIA-positive samples were reactive by HI, but all of these were negative by WNV plaque reduction neutralization test; this is consistent with the presence of non-West Nile flavivirus antibody in these sera. Blood specimens obtained throughout the season from EIA- and HI-positive individuals were uniformly negative for WNV-RNA by reverse transcriptasepolymerase chain reaction. Age, sex, hematology and biochemistry findings, hepatitis B or C virus status, immunosuppressive regimen (cyclosporin or tacrolimus) and pretransplant diagnosis of liver disease were similar for EIA-positive and EIA-negative patients. For the 10 patients with a positive IgG EIA maintained on cyclosporin, the cyclosporin level was 129.1+/-28.6 microg/L compared with 85.6+/-36.7 microg/L in 26 patients who were EIA-negative (P=0.002).

CONCLUSIONS

False-positive IgG EIA serology for WNV was common in this cohort of liver transplant recipients, and was associated with elevated serum cyclosporin levels.