Effects of Age on the Generalization and Incubation of Memory in the F344 Rat

Freezing (immobility) in the presence of aversive stimuli is a species-specific behavior that is used as an operational measure of fear. Conditioning of this response to discrete sensory stimuli and environmental context cues has been used as a tool to study the neuropsychology of memory dynamics and their development over the lifespan. Three age groups of F344 rats (3, 9, and 27 month) received tone–foot shock pairing (or tone only) in a distinctive chamber on two consecutive days. Separate subgroups of rats from each age group were then tested, at retention intervals of 1, 20, 40, or 60 days, for context-mediated fear in the environment in which they were trained, for generalization of the fear response to a novel chamber, and for fear of the tone. Beginning at day 20, the 27-month-old rats exhibited less freezing behavior than did younger rats when tested in the conditioning context. This age difference was a result of freezing behavior becoming progressively stronger with time in the two younger age groups, a phenomenon that has been referred to as memory incubation. Incubation of the contextual fear response was not detected in the old rats. In a novel context, all age groups exhibited significantly more freezing than did control animals. There was also pronounced incubation of this generalized freezing response, and the extent of incubation declined significantly with age. In the novel context, the freezing response to the tone was robust in all age groups and increased over time, in constant proportion to the degree of freezing elicited by the novel context itself, prior to tone onset. The fact that old animals are known to be relatively selectively impaired in forms of memory that depend on a functional hippocampus suggests a possible explanation for the reduced incubation effects seen in old rats; however, whether the increased expression of fear over time is mediated by a hippocampal-dependent memory consolidation process or whether it reflects a generalized increase in the gain of the circuitry mediating the fear response itself, remains to be determined.     

Bilateral Ablation of Auditory Cortex in Mongolian Gerbil Affects Discrimination of Frequency Modulated Tones but not of Pure Tones

This study examines the role of auditory cortex in the Mongolian gerbil in differential conditioning to pure tones and to linearly frequency-modulated (FM) tones by analyzing the effects of bilateral auditory cortex ablation. Learning behavior and performance were studied in a GO/NO-GO task aiming at avoidance of a mild foot shock by crossing a hurdle in a two-way shuttle box. Hurdle crossing as the conditioned response to the reinforced stimulus (CR+), as false alarm in response to the unreinforced stimulus (CR−), intertrial activity, and reaction times were monitored. The analysis revealed no effects of lesion on pure tone discrimination but impairment of FM tone discrimination. In the latter case lesion effects were dependent on timing of lesion relative to FM tone discrimination training. Lesions before training in naive animals led to a reduced CR+ rate and had no effect on CR− rate. Lesions in pretrained animals led to an increased CR− rate without effects on the CR+ rate. The results suggest that auditory cortex plays a more critical role in discrimination of FM tones than in discrimination of pure tones. The different lesion effects on FM tone discrimination before and after training are compatible with both the hypothesis of a purely sensory deficit in FM tone processing and the hypothesis of a differential involvement of auditory cortex in acquisition and retention, respectively.     

Nosology and Causal Necessity; The Relation BetweenDefining a Disease and Discovering its Necessary Cause

The problem of disease definition is related to theproblem of proving that a certain agent is thenecessary cause of a certain disease. Natural kindterms like rheumatoid arthritis and AIDS refer toessences which are discoverable rather thanpredeterminate. No statement about such diseases isa priori necessarily true. Because theories onnecessary causes involve natural kind semantics,Koch's postulates cannot be used to falsify or verifysuch theories. Instead of proving that agent A is thenecessary cause of disease D, we include A in atheoretical definition of D, take this to representthe real meaning of D, and discard thepretheoretical definition. This is illustrated byKoch's own attempt to prove he had discovered thenecessary cause of tuberculosis. Methodologicalarguments about disease causation require a clear viewof our use of diagnostic terms. Medical lexicographersshould do more to provide such a view.     

Adjunctive psychotherapy for bipolar disorder: effects of changing treatment modality

In a randomized, controlled trial, the authors studied an adjunctive, individual psychotherapy, interpersonal and social rhythm therapy (IPSRT) for bipolar disorder. After stabilizing participants with episode appropriate pharmacotherapy and either IPSRT or intensive clinical management (CM), participants were reassigned to IPSRT or CM in conjunction with pharmacotherapy for 2 years of preventative treatment. Early results (n = 82) suggest that altering participants' treatment assignment at entry to the preventative phase is related to risk of recurrence. Participants remaining in the same treatment for both acute and preventative phases had lower rates of recurrence (< 20% vs. > 40%) and levels of symptomatology over the subsequent 52 weeks than those reassigned to the alternate modality. This finding, consistent with the authors' philosophy that bipolar patients benefit from stable routines, suggests that disruptions in the psychosocial treatment plan contribute to worse outcomes.     

Multiple reinforcement contingencies to reduce aggression,self-injury and dysfunctional verbal behaviors in an adult who is sensory impaired

Differential reinforcement of other behavior (DRO) and differential reinforcement of low rates of responding (DRL) have been effective techniques in reducing maladaptive behaviors in therapeutic settings. Reported studies of these reinforcement-based procedures indicate that they are usually implemented in isolation, targeting only a single behavior or class of behaviors. In this study, multiple DRO and DRL contingencies were utilized concurrently in reducing two distinct classes of behaviors with a 26 year-old blind man with moderate retardation. One class of behaviors included socially inappropriate verbalizations, while the other included aggressive, self-injurious and environmentally destructive behaviors. Distinct contingencies were established according to the functions of the targeted behaviors and their severity and separate schedules of reinforcement were derived from baseline frequencies. Over a period of 20 months, the differential reinforcement interventions resulted in rapid reduction of behaviors in both classes to near-zero rates and frequencies were maintained at this low level while contingency schedules were systematically lengthened. Collateral effects are discussed including performance in functional academics and participation in community integration activities.     

Cognitive differentiation in women and pioneer-traditional vocational choices

In order to test the hypothesis that women who went into male dominated fields (pioneers) were more cognitively complex in social relationships than women who went into female dominated fields (traditionals), 83 college seniors were classified and tested using a grid for cognitive complexity in their roles. As predicted, the pioneers were more differentiated (p < .05) in their perception of various social roles and supported the research in cognitive complexity in vocational behavior.     

J. J. Katz' logic of questions: New departure or dead end?

Philosophical Studies -     

Indefinite probability statements

Conclusion Indefinite probability statements can be analysed in terms of statements which attribute probability to propositions. Therefore, there is no need to find a special place in probability theory for them; once we have an adequate account of statements that straightforwardly attribute probability to propositions, we will automatically have an adequate account of indefinite probability statements.