Why people see things that are not there: a novel Perception and Attention Deficit model for recurrent complex visual hallucinations

As many as two million people in the United Kingdom repeatedly see people, animals, and objects that have no objective reality. Hallucinations on the border of sleep, dementing illnesses, delirium, eye disease, and schizophrenia account for 90% of these. The remainder have rarer disorders. We review existing models of recurrent complex visual hallucinations (RCVH) in the awake person, including cortical irritation, cortical hyperexcitability and cortical release, top-down activation, misperception, dream intrusion, and interactive models. We provide evidence that these can neither fully account for the phenomenology of RCVH, nor for variations in the frequency of RCVH in different disorders. We propose a novel Perception and Attention Deficit (PAD) model for RCVH. A combination of impaired attentional binding and poor sensory activation of a correct proto-object, in conjunction with a relatively intact scene representation, bias perception to allow the intrusion of a hallucinatory proto-object into a scene perception. Incorporation of this image into a context-specific hallucinatory scene representation accounts for repetitive hallucinations. We suggest that these impairments are underpinned by disturbances in a lateral frontal cortex-ventral visual stream system. We show how the frequency of RCVH in different diseases is related to the coexistence of attentional and visual perceptual impairments; how attentional and perceptual processes can account for their phenomenology; and that diseases and other states with high rates of RCVH have cholinergic dysfunction in both frontal cortex and the ventral visual stream. Several tests of the model are indicated, together with a number of treatment options that it generates.     

Kanizsa's shrinkage illusion produced by a misapplied 3-D corrective mechanism

In order to include the monocular areas from the left and the right eye in the cyclopean view, the visual system displaces the occluded elements which would result in a horizontal elongation of the shape but does not occur thanks to a correction mechanism which preserves the shape. We hypothesised that this mechanism causes Kanizsa's amodal shrinkage illusion (the apparent elongation of a partially occluded square) when it is incorrectly applied by the visual system to a two-dimensional stimulus. Four experiments tested this hypothesis: (i) one-eyed observers were less susceptible to the illusion than people with normal binocular vision because, for them, the correction for shape is unnecessary; (ii) the illusion was stronger with binocular than with monocular vision since binocularity induces the visual system to correct for the shape distortion; (iii) the illusion diminished when the stimulus was rotated 90 degrees given that displacement and compression are not required for vertical occlusion; (iv) the magnitude of the illusion was a function of the width of the occluder because, as previous research has shown, the edges of a partially occluded square are less displaced the farther they are from the edges of the occluder. The data from the four experiments support our hypothesis even though no condition was able to eliminate the illusion; other possible causes are discussed.     

Differences between golden hamsters (Mesocricetus auratus) and Norway rats (Rattus norvegicus) in preference for the sole diet that they are eating

D. DiBattista (2002) reported that hamsters but not rats showed reduced preferences for the sole diet they had eaten for 10 days. In the current study, the authors fed Norway rats (Rattus norvegicus) a nutritious diet for either 3 or 10 days, then tested them either immediately or 1 or 3 days later. The authors found that like golden hamsters (Mesocricetus auratus), rats exhibited reduced preferences for a prefed diet but only if tested either immediately or 1 day after prefeeding, not if tested 3 days later (when D. DiBattista tested his hamsters). Rats and hamsters differed in the longevity, not the development, of reduced preferences for a palatable food eaten for several consecutive days. Such a response might aid dietary generalists in constructing balanced diets when no single available food is nutritionally adequate.     

Cystic Fibrosis Prenatal Screening in Genetic Counseling Practice: Recommendations of the National Society of Genetic Counselors

For over a decade, prenatal screening for cystic fibrosis (CF) has been considered a model for the integration of genetic testing into routine medical practice. Data from pilot studies and public policy discourse have led to recommendations by some professional organizations that CF screening should be offered or made available to pregnant women and their partners, and to couples planning a pregnancy. It is crucial that genetic counselors gain thorough understanding of the complexities of CF and the implications of positive test results, so that they may serve as a reliable, educated referral base and resource for health care providers and their patients. While not all pregnant women will be referred for genetic counseling prior to CF carrier testing, genetic counselors often will be asked to counsel clients after they have a positive test result, or who are found to be at increased risk. Genetic counselors can play an important role in providing accurate and current information as well as support for patients informed decisions. These recommendations were created by a multicenter working group of genetic counselors with expertise in CF and are based on personal clinical experience, review of pertinent English language medical articles, and reports of expert committees. The recommendations should not be construed as dictating an exclusive course of management, nor does the use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care providers professional judgment based on the clinical circumstances of a particular client.     

Anxiety modulates the degree of attentive resources required to process emotional faces

The present study contributes to the ongoing debate over the extent to which attentive resources are required for emotion perception. Although fearful facial expressions are strong competitors for attention, we predict that the magnitude of this effect may be modulated by anxiety. To test this hypothesis, healthy volunteers who varied in their self-reported levels of trait and state anxiety underwent an attentional blink task. Both fearful and happy facial expressions were subject to a strong attentional blink effect for low-anxious individuals. For those reporting high anxiety, a blink occurred for both fearful and happy facial expressions, but the magnitude of the attentional blink was significantly reduced for the fearful expressions. This supports the proposals that emotion perception is not fully automatic and that anxiety is related to a reduced ability to inhibit the processing of threat-related stimuli. Thus, individual differences in self-reported anxiety are an important determinant of the attentional control of emotional processing.     

Individual differences in trait rumination and the neural systems supporting cognitive reappraisal

Cognitive reappraisal can alter emotional responses by changing one’s interpretation of a situation’s meaning. Functional neuroimaging has revealed that using cognitive reappraisal to increase or decrease affective responses involves left prefrontal activation and goal-appropriate increases or decreases in amygdala activation (Ochsner, Bunge, Gross, & Gabrieli, 2002; Ochsner, Ray, et al., 2004). The present study was designed to examine whether patterns of brain activation during reappraisal vary in relation to individual differences in trait rumination, which is the tendency to focus on negative aspects of one’s self or negative interpretations of one’s life. Individual differences in rumination correlated with increases in amygdala response when participants were increasing negative affect and with greater decreases in prefrontal regions implicated in self-focused thought when participants were decreasing negative affect. Thus, the propensity to ruminate may reflect altered recruitment of mechanisms that potentiate negative affect. These findings clarify relations between rumination and emotion regulation processes and may have important implications for mood and anxiety disorders.     

The Association between Religious Discrimination and Health: Disaggregating by Types of Discrimination Experiences,Religious Tradition,and Forms of Health

Research finds that experiences of religious discrimination are often associated with poorer health outcomes. However, there remain important questions to consider gaps, including whether religious discrimination has similar health impacts on religious minority groups and religious majority groups, whether religious discrimination is equally harmful for both mental and physical health, and whether specific types of discrimination have different impacts on health. Using survey data from a probability sample of U.S. adults and measures representing a variety of discrimination experience types, our analyses suggest that religious discrimination is indeed harmful for health, but that experiences of religious discrimination do not universally affect mental and physical health in the same ways. Rather than significant differences in the health impacts of religious discrimination across different religious groups, we find more variation in the health impacts of different types of experiences with discrimination. Further, we find that mental health is negatively impacted by a wider range of experiences with religious discrimination than physical health. These findings are in line with social psychological research on the differential health impacts of discrimination, and they highlight the importance of context in studies of the health effects of religious discrimination.     

Sentence Comprehension Deficits in Alzheimer''s Disease: A Comparison of Off-Line vs. On-Line Sentence Processing

Two studies explored whether sentence comprehension impairments in Alzheimer's disease (AD) are due to deficits in syntactic processing or memory. Study 1 used a picture-pointing sentence comprehension task to measure the final outcome of comprehension in an off-line fashion. It showed the comprehension of 30 patients with AD to be impaired, but suggested that the deficits could not be attributed solely to syntactic impairments. Study 2 investigated the effects of memory on sentence comprehension by comparing off-line (grammaticality judgment) with on-line (cross-modal naming) language processing in 11 AD and 9 control subjects. The results revealed impaired performance in the off-line task but normal performance in the on-line task using the same sentences. Performance on the off-line task correlated with independent measures of verbal working memory. These data are used to argue that sentence comprehension impairments are related to verbal working memory deficits in AD.     

Perceptual grouping and visual selective attention

The present study demonstrates that incongruent distractor letters at a constant distance from a target letter produce more response competition and negative priming when they share a target’s color than when they have a different color. Moreover, perceptual grouping by means of color, attenuated the effects of spatial proximity. For example, when all items were presented in the same color, near distractors produced more response competition and negative priming than far distractors (Experiment 3A). However, when near distractors were presented in a different color and far distractors were presented in the same color as the target, the response competition × distractor proximity interaction was eliminated and the proximity × negative priming interaction was reversed (Experiment 3B). A final experiment demonstrated that distractors appearing on the same object as a selected target produced comparable amounts of response competition and negative priming whether they were near or far from the target. This suggests that the inhibitory mechanisms of visual attention can be directed to perceptual groups/objects in the environment and not only to unsegmented regions of visual space.