Repetition effects for words and nonwords as indexed by event-related fMRI: a preliminary study

We have previously shown differential effects of stimulus familiarity on the repetition-related responses in right fusiform cortex to both faces and symbols. Repetition of familiar stimuli produced a response decrease, whereas repetition of unfamiliar stimuli produced a response increase. In the present experiment, we used words and nonwords as the familiar and unfamiliar stimuli respectively. In this case, the only fusiform region showing the familiarity-by-repetition interaction was in anterior left fusiform. This left-lateralisation of the fusiform interaction is consistent with our hypothesis that these repetition-related effects occur in the same regions responsible for perceptual recognition of familiar stimuli.     

The congruency effect: just what is being learned?

G. H. Bower, S. Thompson-Schill, and E. Tulving (1994) found that when stimulus-response sets in A-B, A-C learning belong to unique categories (congruent-triads), learning appropriate responses appear rapid and memory performance on a modified modified free recall (MMFR) test is enhanced. Bower et al. assumed that category cues protect associations from interpair interference, allowing more rapid learning. However, unlike arbitrary pairs, congruent pairs also allow a reliance on preexperimental associations. As a result, MMFR test performance may not be an unbiased test of what was learned. In the present experiment, free recall (FR) demonstrated that responses were learned approximately equally in all conditions and that the pattern of clustering was compatible with the hypothesis that preexperimental associations continue to play a major role in FR test performance.     

Response to Difficult Patients in Group Analysis: The Personification of I:A/M

The author focuses on the application of Hopper's proposal of an additional basic assumption (I:A/M) using a model of clinicians' theories: bridging theory, psychological theory, and clinical theory (Michels, 1999). This paper will describe the potential for advances in understanding particular group formations seen in clinical practice and other settings.     

Distributing working memory resources during problem solving

This study examines how problem solvers distribute working memory demands over internal and external resources. Participants recorded notes while performing an arithmetic task. They recorded a majority of intermediate results and labeled many of those results (e.g., "C = 10"). When more effort was required to take notes, participants recorded fewer results. Participants with a consistent goal structure recorded fewer results and with practice labeled fewer recorded results than those with varied goal structures. When notes were displayed in a consistent spatial arrangement participants labeled fewer recorded results than when notes appeared in varied locations. These findings indicate that individuals use explicit and implicit strategies for indexing intermediate results. The data support the view that individuals flexibly distribute working memory over internal and external resources in response to situational cost-benefit considerations.     

Circadian phase-shifted rats show normal acquisition but impaired long-term retention of place information in the water task

It is thought that circadian rhythms may influence learning and memory processes. However, research supporting this view does not dissociate a mnemonic impairment from other performance deficits. Furthermore, published reports do not specify the type of memory system influenced by the circadian system. The present study assessed the effects of phase shifting on acquisition and expression of place navigation in the water maze, a task sensitive to hippocampal dysfunction. The results showed that phase-shifting circadian rhythms in rats impaired the expression of place information on a retention test but not initial acquisition or encoding of place information. These results suggest that disruption of circadian rhythms may impair consolidation of previously encoded hippocampal place information.     

Effects of excitotoxic brain lesions on taste-mediated odor learning in the rat

The association learning between taste and odor is important in ingestive behavior. For a better understanding of this learning, we have developed a convenient and useful paradigm to assess the taste-mediated odor learning. In the training session, Wistar male rats drank water from two bottles in their home cages and from eight small glass dishes. In the learning session they were exposed in their home cages and also in a circular open-field apparatus to 0.005 M Na-saccharin and 0.02 M quinine hydrochloride which contained either banana or almond odors. One learning trial consisted of this pair of exposures. The preceding behavioral experiment has shown that these two odors are not aversive and are differentially perceived by rats. In the test session, the animals were put in the open-field apparatus equipped with eight dishes: four contained water with banana, and another four, with almond. Normal control rats preferred to drink water with the odor previously associated with saccharin. Stronger and more persistent preference was attained after two or three learning trials. To elucidate the brain sites responsible for this taste-mediated odor learning, the same procedure was assessed on brain-lesioned rats. Rats with lesions in the amygdala showed rapid extinction of preference to the saccharin-associated odor, whereas control rats did not. However, rats with lesions in the insular cortex showed retention of learning similar to that of the control rats. Rats with lesions in the sulcal prefrontal or cingulate cortices showed moderate disruptive effects on preference to the saccharin-associated odor. In conclusion, the odor learning established in our experimental paradigm is based on the association between the quality of odor and hedonics of taste. The amygdala may play a role in the formation, at least in the retention process, of this taste-odor association learning.     

Learning and memory in S100-beta transgenic mice: an analysis of impaired and preserved function

S100-beta, a calcium-binding astrocytic protein from chromosome 21, has been implicated in CNS function generally and the hippocampus in particular. Elevated levels of S100-beta have been observed reliably in the brains of patients with Alzheimer's Disease and Down Syndrome. Groups of transgenic mice, carrying multiple S100-beta gene copies, and nontransgenic controls were administered a series of behavioral tests (delayed spatial and nonspatial non-matching-to-sample, radial arm maze, socially acquired food preference) that assessed a wide range of cognitive functions. Consistent with the widespread presence of S100-beta throughout the brain, transgenic mice exhibited learning or memory impairment on all tasks. The dementia-like cognitive profile of S100-beta mice represents a promising model for studying comparable cognitive deficits associated with neurodegenerative diseases.     

Cognitive complexity and the validity of clinicians' judgments

Efforts to explain why some neuropsychologists are more accurate than others have been unsuccessful. In the present study, the relation between the cognitive complexity of clinicians and the validity of their judgments was investigated. Forty-two neuropsychologists completed a measure of cognitive complexity. The hypothesis that neuropsychologists who are high in cognitive complexity will be more accurate than those who are low in cognitive complexity was not supported. It is not clear why cognitive complexity was not significantly related to the validity of diagnostic ratings: One explanation is that the measure of cognitive complexity used in this study was inadequate but another possibility is that neuropsychologists who are low in cognitive complexity may still be able to achieve high levels of accuracy if they attend to normative data when they interpret test results.     

Evading detection on the MMPI-2: does caution produce more realistic patterns of responding?

Studies on MMPI and MMPI-2 malingering indexes often sacrifice generalizability in an attempt to control internal validity. This study improves external validity while still maintaining internal validity by providing graduate student participants with a realistic context for malingering on the MMPI-2 (n=94) and MMPI (n=30). Contextual parameters include a realistic life predicament, psychological knowledge, an incentive, the presence versus absence of a specific diagnosis, and a caution to be realistic. This study found that cautioning participants not to overexaggerate their responses significantly improves their ability to evade detection on the MMPI-2 and MMPI. Standard malingering indexes (Infrequency, F; Back Side, F, Fb; F-Correction, F-K; and Infrequency-Psychopathology, F(p)) were insufficiently sensitive in identifying simulators using common cutoff scores for these cautious simulators.