Rule-based learning impairment in rats with lesions to the dorsal striatum.

The present study examined the effects of lesions to the dorsal striatum (DS) in Sprague-Dawley rats, when tested on the acquisition and successive shifts in the position of a goal arm in an eight-arm radial maze. In the procedure we used, rats had to retrieve the location of one baited arm among the eight arms of the maze after it had just been presented as a sample during a forced trial. After attainment of a fixed learning criterion, rats were submitted to five successive shifts in the goal location. Results showed that DS rats were able to learn the position of the goal arm during the acquisition phase as efficiently as sham-operated rats. In contrast, when the position of the goal arm was shifted, although DS rats were able to learn its new position, they made significantly more errors and required more sessions to reach criterion than sham-operated rats. These results suggested that both groups did not solve the task using the same behavioral strategy. The analysis of responses made suggested that sham-operated rats solved the task using the pairing rule between the forced and the free run (matching-to-sample rule), while DS rats solved the task using only visuo-spatial processing. These data therefore suggest that the dorsal striatum plays an important role in rule-learning ability.     

Psychophysiological Identification of Depression Subtypes in Older Adults: Problematic Diagnostic Heterogeneity in the DSM-III-R and DSM-IV

The DSM-IV does not subclassify patients with depression on the basis of anxiety level. Hence a significant confound may exist in all outcome studies that employ DSM definitions of depression. To establish that objectively identifiable anxious and nonanxious subtypes of depression do indeed exist, a psychophysiological assessment battery was used with 114 treatment-seeking older adults. Dichotomous criterion categorization as either Nonanxious Depressed or Anxious Depressed was based on (a) DSM-III-R/DSM-IV diagnosis, and (b) standardized questionnaires of psychopathology. Multivariate analyses revealed no differences between groups when DSM criteria were used to classify participants. However, identical analyses using phenomenological diagnostic criteria indicated that anxious and nonanxious depressed participants differed in their psychophysiological response to negative imagery. Although anxious and nonanxious depressed participants evince different psychophysiological response patterns, these differences unfortunately are obscured by the DSM. Consequently, a phenomenological classification system may be more appropriate with affective disorders.     

Avoidant personality disorder and implicit schema-congruent information processing bias: a pilot study with a pragmatic inference task.

Cognitive theory of personality disorders hypothesizes that each personality disorder is characterized by typical maladaptive schemes and that these schemas direct the processing of information resulting in schema-congruent biases. With regard to the avoidant personality disorder, these hypotheses were put to an initial test in a pilot study, using a self-report questionnaire to asses DSM-III-R personality pathology, a belief questionnaire to assess avoidant schemas and a pragmatic inference task to assess schema-congruent implicit attributional bias. Participants were students (n = 57) who scored high or low on DSM-III-R avoidant personality pathology. As predicted from cognitive theory, DSM-III-R avoidant personality pathology was associated with avoidant beliefs (t(45.1) = 4.68, p < 0.001) and avoidant beliefs were associated with schema-congruent information processing bias (t(55) = 2.17, p = 0.02, one-tailed test). However, DSM-III-R avoidant personality pathology was not associated with schema-congruent information processing bias (t(55) = 0.17, p = 0.43, one-tailed test). In addition to avoidant beliefs, low self-esteem was also related to the information processing bias. Social phobia and general personality pathology, two other control variables, were not. The findings warrant further study using the pragmatic inference task in a clinical group.     

Fear relevance and diminution of unconditioned skin conductance responses.

According to Donegan and Wagner's priming model [1987], a signalled UCS will elicit a smaller UCR than an unsignalled UCS. Assuming that fear-relevant CSs are good predictors of aversive UCSs, while fear-irrelevant CSs are relatively bad predictors of aversive UCSs, the present study examined the effect of fear relevance on electrodermal UCR diminution during the acquisition phase of a single cue conditioning procedure. Four groups were studied, each of which consisted of 12 subjects. Group 1 had a fear-relevant CS (a slide of an angry face) paired with a UCS (7 mA shock), whereas group 2 had a fear-irrelevant CS (a slide of a happy face) paired with a UCS. Groups 3 and 4 had unpaired presentations of the CS and UCS and served as control groups for 1 and 2. There were 4 habituation, 8 acquisition, 4 recovery (UCS-only), and 6 extinction (CS-only) trials. While overall UCR levels were lower in the paired than in the unpaired control groups, it was also found that the size of UCR decrement and subsequent recovery was greater in the angry face CS-paired group than in the happy face CS-paired group. This finding is in line with the predictions that flow from the Donegan and Wagner model.     

Program Constructions that are Safe for Bisimulation

It has been known since the seventies that the formulas of modal logic are invariant for bisimulations between possible worlds models — while conversely, all bisimulation-invariant first-order formulas are modally definable. In this paper, we extend this semantic style of analysis from modal formulas to dynamic program operations. We show that the usual regular operations are safe for bisimulation, in the sense that the transition relations of their values respect any given bisimulation for their arguments. Our main result is a complete syntactic characterization of all first-order definable program operations that are safe for bisimulation. This is a semantic functional completeness result for programming, which may be contrasted with the more usual analysis in terms of computational power. The 'Safety Theorem' can be modulated in several ways. We conclude with a list of variants, extensions, and further developments.     

Socialism in One Country: A Reassessment

Until 1917 Lenin and Trotsky believed that an isolated revolutionary Russia would have no chance of survival. However, from 1917 to 1923 Lenin's standpoint on this matter underwent a complete reversal. First he came to the conclusion that socialism could be built in an isolated Russia, although it would remain incomplete in the absence of the world revolution. By 1923 he was abandoning that latter qualification too. The standpoint of Stalin and Bukharin in the debate on socialism in one country of 1925–26 was more orthodox-Leninist than the position taken by Trotsky, who had at first also embraced the notion of incomplete socialism, but subsequently returned to the old concept, abandoned by Lenin, that the restoration of capitalism was inevitable in the absence of the world revolution.     

Stability of memory for colour in context.

Memory for colours presented in isolation was compared with that for colours presented as part of a clip-art image or as part of a non-meaningful, Mondrian-like image. The area under the Receiver Operating Characteristic for deciding that two colours, presented at different delay intervals, were the same or different provided an index of memory for colour. The provision of a context reduced the decay of memory, regardless of whether the context was meaningful (clip-art images) or non-meaningful (Mondrian-like images). The result was seen as a generalisation of the auditory phenomenon of profile analysis, in which memory for the amplitude of a single component of a complex sound is more stable than that for the component in isolation.     

Interfering with the Central Executive by Means of a Random Interval Repetition Task

Four dual-task experiments are reported in which a short-term memory task is performed concurrently with a random interval repetition task, which was designed to interfere with functions normally attributed to the central executive in the working memory model of Baddeley and Hitch (1974). The task was found to interfere with supra-span serial recall and with backward memory span, but did not disrupt performance on a forward-memoryspan task. The effects were observed in dissociation with effects of articulatory suppression and matrix tapping, so that the locus of the effects of the new task is not due to the slave systems. In addition, single-task random-interval repetition performance was sampled and compared to performance in the dual-task conditions of all four experiments. Although quality of tapping performance differed between the single-task and the dual-task conditions, it was not related to recall performance. All the results are discussed with reference to the working memory model.     

Storage of verbal associations is sufficient to activate the left medial temporal lobe

Neuroimaging studies have shown that memory encoding activates the medial temporal lobe (MTL). Many believe that these activations are related to novelty but it remains unproven which is critical - novelty detection or the rich associative encoding it triggers. We examined MTL activation during verbal associative encoding using functional magnetic resonance imaging. First, associative encoding activated left posterior MTL more than single word encoding even though novelty detection was matched, indicating not only that associative encoding activates the MTL particularly strongly, but also that activation does not require novelty detection. Moreover, it remains to be convincingly shown that novelty detection alone does produce such activation. Second, repetitive associative encoding produced less MTL activation than initial associative encoding, indicating that priming of associative information reduces MTL activation. Third, re-encoding familiar associations in a well-established way had a minimal effect on both memory and MTL activation, indicating that MTL activation reflects storage of associations, not merely their initial representation.     

We almost had a great future behind us: The contribution of non-linear dynamics to developmental-science-in-the-making

Classical developmental theories, like those of Piaget, Werner and Vygotsky, were on the verge of developmental science, the study of phenomena from the point of view of development. Methodological and theoretical shifts in the 1960s changed the original goals and questions and turned developmental psychology into a discipline that is, on the whole, more like a subservient than a leading branch of psychology. Dynamic systems theory, which has its roots in mathematics and physics, can help developmental theory out of its current blind alley by providing the general theoretical frameworks and methods for bringing the dynamic aspects of change back to the fore. By doing so, it will help turn the scientific course back in the direction of developmental science.