Numerical Congruency Effect in the Sentence-Picture Verification Task.

In two experiments, we showed that irrelevant numerical information influenced the speed of sentence-picture verification. Participants were asked to verify whether the concept mentioned in a sentence matched the object presented in a subsequent picture. Concurrently, the number word attached to the concept in the sentence and the quantity of objects presented in the picture were manipulated (numerical congruency). The number of objects varied from one to four. In Experiment 1, participants read statements such as three dogs. In Experiment 2, they read sentences such as three dogs were wandering in the street. In both experiments, the verification speed revealed the interaction between response and numerical congruency. The verification times for concept-object match were faster when there was also numerical congruence (compared with incongruence) between the number word and quantity. On the other hand, there was no difference between numerical congruence and incongruence when the concept and object mismatched. The results are interpreted as evidence for the symbol grounding of number words in perceptual representation of small quantities, that is, quantities falling in the subitization range.

Resonant Dynamics of Grounded Cognition: Explanation of Behavioral and Neuroimaging Data Using the ART Neural Network.

Research on grounded cognition suggests that the processing of a word or concept reactivates the perceptual representations that are associated with the referent object. The objective of this work is to demonstrate how behavioral and functional neuroimaging data on grounded cognition can be understood as different manifestations of the same cortical circuit designed to achieve stable category learning, as proposed by the adaptive resonance theory (ART). We showed that the ART neural network provides a mechanistic explanation of why reaction times in behavioral studies depend on the expectation or attentional priming created by the word meaning (Richter and Zwaan, 2009). A mismatch between top-down expectation and bottom-up sensory data activates an orienting subsystem that slows execution of the current task. Furthermore, we simulated the data from functional neuroimaging studies of color knowledge retrieval that showed anterior shift (Chao and Martin, 1999; Thompson-Schill, 2003) and an overlap effect (Simmons et al., 2007; Hsu et al., 2011) in the left fusiform gyrus. We explain the anterior effect as a result of the partial activation of different components of the same ART circuit in the condition of passive viewing. Conversely, a demanding perceptual task requires activation of the whole ART circuit. This condition is reflected in the fMRI image as an overlap between cortical activation during perceptual and conceptual processing. We conclude that the ART neural network is able to explain how the brain grounds symbols in perception via perceptual simulation.

Attentional biases in irritable bowel syndrome patients.

BACKGROUND AND OBJECTIVE: According to the cognitive behavioural model of irritable bowel syndrome (IBS) selective attention to visceral stimuli is one of the pathophysiological mechanisms in IBS. We aimed to investigate attentional biases in patients with IBS and to explore the relationship between neuroticism, trait anxiety, visceral anxiety and indices of attentional biases. METHODS: Twenty-seven patients completed the global/local task and the modified Stroop task (using 4 word categories: neutral, symptom-related, emotionally and situationally relevant) while 28 healthy persons completed the Stroop task only. Both groups also filled out a set of psychological questionnaires. RESULTS: The results show two distinct attentional biases in patients with irritable bowel syndrome. The index of global precedence was negatively correlated with neuroticism (r=-.41, P<.05) while there was no correlation of global precedence with trait and visceral anxiety. We found Stroop facilitation (F[3,81]=3.98, P<.02) specifically for situational threat words. Also, there were positive correlations between trait anxiety, visceral anxiety and the Stroop facilitation index for situational threat words (r=.43 and r=.47, P<.05). In the control group, we found neither Stroop facilitation nor interference. But, facilitation index of emotional words was positively correlated with neuroticism (r=.40, P<.05), which is in line with the "emotion congruent attentional bias" in the general population. CONCLUSIONS: Neuroticism was associated with the reduction in global precedence observed in the global/local task. Trait anxiety and visceral anxiety were associated with Stroop facilitation elicited by situational threat words, which are of particular concern for patients with irritable bowel syndrome. These specific situations do not elicit an attentional bias in healthy participants, which might indicate that the observed facilitation to situational threat words is unique for IBS patients.

The evaluation of the stroke unit in Croatia at the University Hospital Sestre milosrdnice, Zagreb: 1995-2006 experience.

This study evaluate the effects of the Stroke Unit (SU) in Croatia by comparing the in-hospital case fatality rate in the period before (1995-2000) and after (2001-2006) the implementation of SU and to compare the prevalence of risk factors, such as hypertension, diabetes mellitus (DM), atrial fibrillation (AF) and ischemic heart disease (IHD) among the patients who died. The study was conducted in twelve-year period during which 10,901 stroke patients were admitted to hospital and 1818 of them died. The endpoints were in-hospital case fatality rate and prevalence of risk factors among the patients who died. Before the SU period the case fatality rate was 20.1%, whereas afterwards it decreased significantly to 12.8% (p < 0.001). The relative risk (RR) was 1.57, while the estimate of the odds ratio (OR) showed a 71% increase in chances of death in the pre-SU period. The prevalence of DM, IHD and AF increased significantly, while hypertension was the only risk factor which significantly decreased (p < 0.001). The results showed that the implementation of SU care is associated with a significant reduction of in-hospital case fatality rate of acute stroke patients which strongly suggests that development of the SU network in Croatia should be given priority in the health management.

Modeling the top-down influences on the lateral interactions in the visual cortex.

Attention modulates the amount of excitatory and inhibitory lateral interactions in the visual cortex. A recurrent neural network is proposed to account for modulatory influence of top-down signals. In the model, two types of inhibitions are distinguished: dendritic and lateral inhibitions. Dendritic inhibition regulates the amount of impact that surrounding cells may exert on a target cell via the dendrites of excitatory neurons and the dendrites of subpopulation of inhibitory neurons mediating lateral inhibition. Attention increases the amount of dendritic inhibition and prevents contextual interactions, while it has no effect on the target cell when there is no surround input. Computer simulations showed that the proposed model is able to exhibit properties of attentional gating. In the condition of focused attention, neural activity in the presence of surrounding stimuli is restored to the level as when the target stimulus is presented alone. Moreover, the model is able to show contrast gain and response gain on the contrast sensitivity function depending on the strength of the dendritic inhibition.

Effects of isolation and inbreeding on human quantitative traits: an example of biochemical markers of hemostasis and inflammation.

Isolation is a known force in evolutionary biology and one of the main factors in speciation. One of the main consequences of severe isolation is reduced mate choice, which results in the occurrence of inbreeding as a result of isolation. We investigated the effects of individual genome-wide heterozygosity measured as the multilocus heterozygosity (MLH) on biochemical markers of hemostasis and inflammation in 1,041 individuals from the island of Vis, Croatia, where inbreeding is prevalent and a wide range of variation in the genome-wide heterozygosity is expected. Assessment of individual genome-wide heterozygosity was based on genome-wide scans using 800 microsatellite (STR) and 317,503 single nucleotide (SNP) polymorphic markers in each examinee. In addition, for each examinee we defined a personal genetic history (PGH) based on genealogical records. The association between PGH and MLH and fibrinogen, D-dimer (Dd), von Willebrand factor (vWF), tissue plasminogen activator (tPA), and C-reactive protein (CRP) was performed with a mixed model, controlling for possible confounding effects. PGH was a significant predictor only for tPA (P < 0.001), whereas neither of the two MLH measures exhibited significant association with any of the investigated traits. The effects of individual genome-wide heterozygosity are most likely expressed in highly polygenically determined traits or in traits that are mediated by rare and recessive genetic variants. Weak associations between PGH and MLH and markers of hemostasis and inflammation suggest that their genetic control may not be highly polygenic and that they could be promising targets for genetic association studies.

A feedback model of figure-ground assignment.

A computational model is proposed in order to explain how bottom-up and top-down signals are combined into a unified perception of figure and background. The model is based on the interaction between the ventral and the dorsal stream. The dorsal stream computes saliency based on boundary signals provided by the simple and the complex cortical cells. Output from the dorsal stream is projected to the surface network which serves as a blackboard on which the surface representation is formed. The surface network is a recurrent network which segregates different surfaces by assigning different firing rates to them. The figure is labeled by the maximal firing rate. Computer simulations showed that the model correctly assigns figural status to the surface with a smaller size, a greater contrast, convexity, surroundedness, horizontal-vertical orientation and a higher spatial frequency content. The simple gradient of activity in the dorsal stream enables the simulation of the new principles of the lower region and the top-bottom polarity. The model also explains how the exogenous attention and the endogenous attention may reverse the figural assignment. Due to the local excitation in the surface network, neural activity at the cued region will spread over the whole surface representation. Therefore, the model implements the object-based attentional selection.