Functional brain imaging as a looking-glass into the degraded brain: reviewing evidence from Alzheimer disease in relation to normal aging

Research on the real-time relationship between brain activity and mental performance is intense. However, relatively few studies have been devoted to patients with different diseases or lesions. Such studies may cast light on certain aspects of brain activity, such as plasticity. This review summarizes studies on Alzheimer's disease (AD) patients where the techniques to map brain activity in relation to mental performance have been utilized. Research findings suggest, that there is a spectrum of changes in AD patients that is distinct from that seen in healthy aging. These changes include: (i) loss of activated regions, (ii) reduced activation possibly due to brain degeneration typical of AD, (iii) the emergence of newly activated regions in order to compensate for minor brain deterioration (e.g., an enlargement of activated regions sometimes manifested as an increased bilaterality or a hemispheric shift of activation, and dedifferentiation), (iv) decreased level of activation, and (v) no change at all, which may occur in easy tasks or tasks that do not involve regions exposed to brain atrophy. In conclusion, the pattern of activation in AD depends on interactions between the clinical stage of patients, and the pattern of brain degeneration, as well as the task difficulty and specific networks necessary for solving the task.     

Mood, personality disorder symptoms and disability in obsessive compulsive hoarders: a comparison with clinical and nonclinical controls

Hoarding is a symptom of obsessive compulsive disorder (OCD), as well as a diagnostic criterion for obsessive compulsive personality disorder (OCPD). One recent study suggests that people who suffer from compulsive hoarding report more general psychopathology than people who do not [Frost, R.O., Krause, M.S., & Steketee, G. (1996). Hoarding and obsessive compulsive symptoms. Behavior Modification, 20, 116-132]. The present study addressed whether persons with OCD hoarding exhibit more depression, anxiety, OCD and personality disorders symptoms than community controls, OCD nonhoarders, or other anxiety disorder patients. Disability was also examined. Hoarding subjects were older than the other three groups, but age did not account for any of the differences observed among the groups. Compared to controls, OCD hoarding, nonhoarding OCD and anxiety disorder patients showed elevated YBOCS scores, as well as higher scores on depression, anxiety, family and social disability. Compared to nonhoarding OCD and anxiety disorder patients, OCD hoarding patients scored higher on anxiety, depression, family and social disability. Hoarding subjects had greater personality disorder symptoms than controls. However, OCD hoarding subjects differed from OCD nonhoarding and anxiety disorder subjects only on dependent and schizotypal personality disorder symptoms. The findings suggest that hoarding is associated with significant comorbidity and impairment compared to nonhoarding OCD and other anxiety disorders.     

Self-appraised social problem solving abilities, emotional reactions and actual problem solving performance

Self-report measures of social problem solving abilities have yet to be associated with objective problem solving performance in any consistent manner. In the present study, we investigated the relation of social problem solving abilities--as measured by the Social Problem Solving Skills Inventory--Revised (SPSI-R [Maydeu-Olivares, A. & D'Zurilla, T. J. (1996). A factor analytic study of the Social Problem Solving Inventory: an integration of theory and data. Cognitive Therapy and Research, 20, 115-133])--to performance on a structured problem solving task. Unlike previous studies, we examined the relation of problem solving skills to performance curves observed in repeated trials, while controlling for affective reactions to each trial. Using hierarchical modeling techniques, a negative problem orientation was significantly predictive of performance and this effect was not mediated by negative affectivity. Results are discussed as they pertain to contemporary models of social problem solving.     

The concreteness effect: evidence for dual coding and context availability

The term concreteness effect refers to the observation that concrete nouns are processed faster and more accurately than abstract nouns in a variety of cognitive tasks. Two models have been proposed to explain the neuronal basis of the concreteness effect. The dual-coding theory attributes the advantage to the access of a right hemisphere image based system in addition to a verbal system by concrete words. The context availability theory argues that concrete words activate a broader contextual verbal support, which results in faster processing, but do not access a distinct image based system. We used event-related fMRI to detect the brain regions that subserve to the concreteness effect. We found greater activation in the lower right and left parietal lobes, in the left inferior frontal lobe and in the precuneus during encoding of concrete compared to abstract nouns. This makes a single exclusive theory unlikely and rather suggests a combination of both models. Superior encoding of concrete words in the present study may result from (1) greater verbal context resources reflected by the activation of left parietal and frontal associative areas, and (2) the additional activation of a non-verbal, perhaps spatial imagery-based system, in the right parietal lobe.     

Effects of directionality in deductive reasoning: I. The comprehension of single relational premises

Four experiments involving 123 university students tested directionality effects in the comprehension of spatial relations, quantified statements, and propositional connectives with a sentence-picture verification task. Presentation of the referents of terms in the statements was separated by 1 s, and presentation order was congruent or incongruent with the order of terms in the statement. Some relations showed faster verification times for congruent display order, others for incongruent display order, and still others showed no directionality effect. The authors proposed a 2-step process model for the construction of semantic representations of relational statements, in which a reference object is established first, and then the second object is attached in relation to it. This theory explains the various directionality effects as a general preference to process information about the reference object before information about the target object.     

The effect of familial sinistrality on the relation between schizophrenialike thinking and pseudoneglect

We have recently reported a correlation between schizophrenialike symptoms and the degree of pseudoneglect in healthy right-handers. We aimed to investigate the effect of familial sinistrality (FS) on this relation. Seventy-six healthy right-handers were divided into four groups on the basis of gender and FS. A computerized version of Corsi's task was used as the visuospatial task. Subjects filled in the Magical Ideation Scale (MI), which asked for delusionlike beliefs, and performed the Corsi's task using each hand. Performance of both hemispaces was separately evaluated. In all groups, performance of the left hemispace was better than that of the right hemispace and FS+ subjects performed better than FS- subjects. When the right hand was used, performance was correlated to MI scores only for FS- groups. Findings suggest that the correlation between right-sided neglect and proneness to schizotypy in normal right-handers is affected by FS.     

Model complexity: The fit to random data reconsidered

A recent controversy in the field of depth perception has highlighted an important aspect of model testing concerning a model's complexity, defined as the prior propensity of the model to fit arbitrary data sets. The present article introduces an index of complexity, called the mean minimum distance, defined as the average squared distance between an arbitrary data point and the prediction range of the model. It may also be expressed as a dimensionless quantity called the scaled mean minimum distance. For linear models, theoretical values for the scaled mean minimum distance and the variance of the scaled minimum distance can be readily obtained and compared against empirical estimates obtained from fits to random data. The approach is applied to resolving the question of the relative complexity of the Linear Integration model and the Fuzzy Logic of Perception model, both of which have been the subject of controversy in the field of depth perception. It is concluded that the two models are equally complex. Received: 10 October 1998 / Accepted: 22 December 1998     

Form and movement in stereokinetic cycloids: motion lost and found

In exploring stereokinesis, we devised flat cycloidal display figures which, when rotated on a disc in the frontal plane, are perceived as illusory three-dimensional forms with movement in depth; the dominant percepts were of twisted loops with an internal writhing motion. These dominant forms could be convincingly represented by stereo pairs derived from the flat display; related forms, not seen in the illusion, could also be constructed, seeming to show a selectivity for preferred stereokinetic forms by the perceptual system. Models were made of the stereo forms; when rotated, they showed similar illusions and selectivity. We suggest that the illusions arise because some components of the real motion do not appear in the sensory field. The perceptual system accommodates for this by constructing percepts which are not necessarily veridical but do reconcile form and motion into a coherent unity. The results are discussed in relation to concepts of invariance and rigidity, and with regard to the creative response to sensory data by the perceptual system.     

Development of object permanence in food-storing magpies (Pica pica)

The development of object permanence was investigated in black-billed magpies (Pica pica), a food-storing passerine bird. The authors tested the hypothesis that food-storing development should be correlated with object-permanence development and that specific stages of object permanence should be achieved before magpies become independent. As predicted, Piagetian Stages 4 and 5 were reached before independence was achieved, and the ability to represent a fully hidden object (Piagetian Stage 4) emerged by the age when magpies begin to retrieve food. Contrary to psittacine birds and humans, but as in dogs and cats, no "A-not-B error" occurred. Although magpies also mastered 5 of 6 invisible displacement tasks, evidence of Piagetian Stage 6 competence was ambiguous.