Electrophysiological evidence for the effects of unitization on associative recognition memory in older adults

Normal aging is associated with greater decline in associative memory relative to item memory due to impaired recollection. Familiarity may also contribute to associative recognition when stimuli are perceived as a 'unitized' representation. Given that familiarity is relatively preserved in older adults, we explored whether age-related associative memory deficits could be attenuated when associations were unitized (i.e., compounds) compared with those non-unitized (i.e., unrelated word pairs). Young and older adults performed an associative recognition task while electroencephalogram (EEG) was recorded. Behavioral results showed that age differences were smaller for recognition of compounds than for unrelated word pairs. ERP results indicated that only compounds evoked an early frontal old/new effect in older adults. Moreover, the early frontal old/new effect was positively correlated with associative discrimination accuracy. These findings suggest that reduced age-related associative deficits under unitized condition may be associated with the presence of familiarity-based retrieval of compounds in older adults. (C) 2015 Elsevier Inc. All rights reserved

Beyond Homozygosity Mapping: Family-Control analysis based on Hamming distance for prioritizing variants in exome sequencing

A major challenge in current exome sequencing in autosomal recessive (AR) families is the lack of an effective method to prioritize single-nucleotide variants (SNVs). AR families are generally too small for linkage analysis, and length of homozygous regions is unreliable for identification of causative variants. Various common filtering steps usually result in a list of candidate variants that cannot be narrowed down further or ranked. To prioritize shortlisted SNVs we consider each homozygous candidate variant together with a set of SNVs flanking it. We compare the resulting array of genotypes between an affected family member and a number of control individuals and argue that, in a family, differences between family member and controls should be larger for a pathogenic variant and SNVs flanking it than for a random variant. We assess differences between arrays in two individuals by the Hamming distance and develop a suitable test statistic, which is expected to be large for a causative variant and flanking SNVs. We prioritize candidate variants based on this statistic and applied our approach to six patients with known pathogenic variants and found these to be in the top 2 to 10 percentiles of ranks

Sex-Specific Diurnal Immobility Induced by Forced Swim Test in Wild Type and Clock Gene Deficient Mice

Objective: The link between alterations in circadian rhythms and depression are well established, but the underlying mechanisms are far less elucidated. We investigated the circadian characteristics of immobility behavior in wild type (WT) mice and mice with mutations in core Clock genes. Methods: All mice were tested with forced swim test (FST) at 4 h intervals. Results: These experiments revealed significant diurnal rhythms associated with immobility behavior in both male and female WT mice with sex-different circadian properties. In addition, male mice showed significantly less immobility during the night phase in comparison to female mice. Female Per1(Brdm1) mice also showed significant rhythmicity. However, the timing of rhythmicity was very different from that observed in female wild type mice. Male Per1(Brdm1) mice showed a pattern of rhythmicity similar to that of wild type mice. Furthermore, female Per1(Brdm1) mice showed higher duration of immobility in comparison to male Per1(Brdm1) mice in both daytime and early night phases. Neither Per2(Brdm1) nor Clock(19) mice showed significant rhythmicity, but both female Per2(Brdm1) and Clock(19) mice had lower levels of immobility, compared to males. Conclusions: This study highlights the differences in the circadian characteristics of immobility induced by FST in WT, Clock(19), Per1, and Per2 deficient mice

A Stroop effect emerges in the processing of complex Chinese characters that contain a color-related radical

Three experiments examined whether a Stroop effect emerges in the processing of complex Chinese characters that contain a color-related radical. In Experiment 1, a Stroop effect occurred when participants responded to the black or white color of the simple characters (black) and (white) by making a left or right keypress. For Experiment 2, in which the stimuli were complex characters whose meanings were unrelated to color but that contained or as a radical, a Stroop effect also occurred, although it was smaller than in Experiment 1. Furthermore, this Stroop effect as a function of radical meaning was shown again in Experiment 3 for low-frequency complex characters but not high-frequency ones. These results suggest that the semantic representations of the complex characters' color-related radicals are accessed in the context of a Stroop color word task, especially for low-frequency characters. Reduction of the Stroop effect in complex characters composed of one radical with color meaning and one without is similar to dilution of the Stroop effect that occurs when a color word is accompanied by a neutral word. Possible implications of the results for accounts of Stroop dilution are discussed

Visuospatial characteristics of an elderly Chinese population: results from the WAIS-R block design test

Visuospatial deficits have long been recognized as a potential predictor of dementia, with visuospatial ability decline having been found to accelerate in later stages of dementia. We, therefore, believe that the visuospatial performance of patients with mild cognitive impairment (MCI) and dementia (Dem) might change with varying visuospatial task difficulties. This study administered the Wechsler Adult Intelligence Scale-Revised (WAIS-R) Block Design Test (BDT) to determine whether visuospatial ability can help discriminate between MCI patients from Dem patients and normal controls (NC). Results showed that the BDT could contribute to the discrimination between MCI and Dem. Specifically, simple BDT task scores could best distinguish MCI from Dem patients, while difficult BDT task scores could contribute to discriminating between MCI and NC. Given the potential clinical value of the BDT in the diagnosis of Dem and MCI, normative data stratified by age and education for the Chinese elderly population are presented for use in research and clinical settings

Effects of working memory load on uncertain decision-making: evidence from the Iowa Gambling Task

The Iowa Gambling Task (IGT) simulates uncertain gains and losses in real life situations and thus is a good measure of uncertain decision-making. The role of working memory (WM) in IGT performance still remains unclear. The present study aimed to examine the effect of WM on IGT performance. Three groups of participants matched on gender ratio were randomly assigned to no WM load, low WM load, and high WM load conditions. Initially the three groups did not show significant difference in WM capacity. They finished a modified version of IGT and then their implicit learning effect and explicit cognition on IGT were assessed. Results indicated a linear increasing trend of IGT performance among high WM load, low WM load and no WM load groups; participants in the no WM load and low WM load groups revealed implicit learning effect, while participants in the high WM load group did not; all participants showed explicit cognition on IGT to the same level. These results suggested that participants in the high WM load group showed good explicit cognition to IGT but showed poor performance. This pattern is similar to frontal patients. Further studies should be conducted to explore this issue

There is no relationship between preferred viewing location and word segmentation in Chinese reading

In Chinese, as there are no spaces between words to mark word boundaries, readers usually do not target their eyes to the centre of the word as readers of English do. Previous studies showed that the distribution of the initial landing positions on a word (the PVL curve) peaked at the beginning of a word when there was more than one fixation; but peaked at the centre of a word if there was only one fixation on the word. Based on this phenomenon, it was argued that Chinese readers move their eyes to the beginning of a word if they cannot correctly segment words in the parafovea, but move to the centre of a word if they can. In the present study, we implemented a natural sentence reading task in Experiment 1 and a shuffled-character reading task in Experiment 2 to test whether the above PVL phenomenon was in fact caused by word segmentation. In both experiments, we found that the different PVL patterns in multiple- and single-fixation cases occurred not only for a 3-character word region but also for a 3-character nonword region. These results suggest that the different PVL curves in multiple- and single-fixation cases are likely to be due to a statistical artefact instead of parafoveal word segmentation

The effects of unitization on the contribution of familiarity and recollection processes to associative recognition memory: Evidence from event-related potentials

Familiarity and recollection are two independent cognitive processes involved in recognition memory. It is traditionally believed that both familiarity and recollection can support item recognition, whereas only recollection can support associative recognition. Here, using a standard associative recognition task, we examined whether associative retrieval of unitized associations involved differential patterns of familiarity and recollection processes relative to non-unitized associations. The extent of engagement of familiarity and recollection processes during associative retrieval was estimated by using event-related potentials (ERPs). Twenty participants studied compound words and unrelated word pairs during encoding. Subsequently, they were asked to decide whether a presented word pair was intact rearranged, or a new pair while electroencephalogram (EEG) was recorded. ERP results showed that compound words evoked a significant early frontal old/new effect (associated with familiarity) between ERPs to intact and rearranged word pairs, whereas this effect disappeared for the unrelated word pairs. In addition, the left parietal old/new effect (associated with recollection) between ERPs to intact and rearranged word pairs was greater for compounds than for unrelated word pairs. These findings suggest that unitization enhances the contribution of both familiarity and recollection processes to associative recognition. (C) 2015 Elsevier B.V. All rights reserved

Saccade target selection in Chinese reading

In Chinese reading, there are no spaces to mark the word boundaries, so Chinese readers cannot target their saccades to the center of a word. In this study, we investigated how Chinese readers decide where to move their eyes during reading. To do so, we introduced a variant of the boundary paradigm in which only the target stimulus remained on the screen, displayed at the saccade landing site, after the participant's eyes crossed an invisible boundary. We found that when the saccade target was a word, reaction times in a lexical decision task were shorter when the saccade landing position was closer to the end of that word. These results are consistent with the predictions of a processing-based strategy to determine where to move the eyes. Specifically, this hypothesis assumes that Chinese readers estimate how much information is processed in parafoveal vision and saccade to a location that will carry novel information