Response–reinforcer dependency and resistance to change

The effects of the response–reinforcer dependency on resistance to change were studied in three experiments with rats. In Experiment 1, lever pressing produced reinforcers at similar rates after variable interreinforcer intervals in each component of a two‐component multiple schedule. Across conditions, in the fixed component, all reinforcers were response‐dependent; in the alternative component, the percentage of response‐dependent reinforcers was 100, 50 (i.e., 50% response‐dependent and 50% response‐independent) or 10% (i.e., 10% response‐dependent and 90% response‐independent). Resistance to extinction was greater in the alternative than in the fixed component when the dependency in the former was 10%, but was similar between components when this dependency was 100 or 50%. In Experiment 2, a three‐component multiple schedule was used. The dependency was 100% in one component and 10% in the other two. The 10% components differed on how reinforcers were programmed. In one component, as in Experiment 1, a reinforcer had to be collected before the scheduling of other response‐dependent or independent reinforcers. In the other component, response‐dependent and ‐independent reinforcers were programmed by superimposing a variable‐time schedule on an independent variable‐interval schedule. Regardless of the procedure used to program the dependency, resistance to extinction was greater in the 10% components than in the 100% component. These results were replicated in Experiment 3 in which, instead of extinction, VT schedules replaced the baseline schedules in each multiple‐schedule component during the test. We argue that the relative change in dependency from Baseline to Test, which is greater when baseline dependencies are high rather than low, could account for the differential resistance to change in the present experiments. The inconsistencies in results across the present and previous experiments suggest that the effects of dependency on resistance to change are not well understood. Additional systematic analyses are important to further understand the effects of the response–reinforcer relation on resistance to change and to the development of a more comprehensive theory of behavioral persistence.     

Conditioned and unconditioned fear organized in the periaqueductal gray are differentially sensitive to injections of muscimol into amygdaloid nuclei

The lateral and basolateral nuclei of the amygdala (LaA and BLA, respectively) serve as a filter for unconditioned and conditioned aversive information that ascends to higher structures from the brainstem, whereas the central nucleus of the amygdala (CeA) is considered to be the main output for the defense reaction. It has been shown that the dorsal periaqueductal gray (dPAG) is activated by threatening stimuli and has important functional links with the amygdala through two-way anatomical connections. In this work, we examined the influence of chemical inactivation of these nuclei of amygdala on the freezing and escape responses induced by electrical stimulation through electrodes implanted in the dPAG of Wistar rats. Each rat also bore a cannula implanted in the LaA, BLA or CeA for injections of muscimol (0.5 microg/0.5 microL) or its vehicle. The duration of freezing behavior that outlasts electrical stimulation of the dPAG was also measured. On the following day, these animals were submitted to a contextual fear-conditioning using foot shocks as unconditioned stimulus. Conditioned freezing to contextual cues previously associated with foot shocks was also inhibited by injections of muscimol into these amygdaloid nuclei. The contextual conditioned freezing behavior is generated in the neural circuits of conditioned fear in the amygdala. The data obtained also show that injections of muscimol into the three amygdaloid nuclei did not change the aversive threshold of freezing, but disrupted the dPAG post-stimulation freezing. Previous findings that the latter freezing results directly from dPAG stimulation and that it is not sensitive to a context shift suggest that it is unconditioned in nature. Thus, the amygdala can affect some, but not all, aspects of unconditioned freezing. Post-stimulation freezing may reflect the process of transferring aversive information from dPAG to higher brain structures.     

Role of muscarinic M1 receptors in inhibitory avoidance and contextual fear conditioning

The objective of the present study was to observe the effects of pre-training or post-training administration of dicyclomine, a M1 muscarinic antagonist, on inhibitory avoidance (IA) and contextual fear conditioning (CFC) and to investigate if the effects observed with the pre-training administration of dicyclomine are state-dependent. For each behavioral procedure (IA and CFC) groups of Wistar male rats were treated with saline or dicyclomine either 30 min before training (pre-training), immediately after training or 30 min before training/30 min before test (pre-training/pre-test). The animals were tested 24 h after training. The acquisition of IA and CFC was impaired by pre-training administration of dicyclomine. The consolidation of both tasks was not affected by dicyclomine given immediately after training. Pre-training/pre-test administration of dicyclomine impaired both tasks, an effect similar to that observed in the group which only received pre-training administration. Pre-test treatment induced dissociation between both tasks, impairing CFC retrieval, without interfering with the animals avoidance response. These results show that the dicyclomine did not affect IA and CFC consolidation, suggesting specific involvement of M1 muscarinic receptor only in acquisition these tasks, and these effects was not state-dependent. However, it is possible that the retrieval of these tasks may be mediated, at least in part, by different neurochemical mechanisms and may be dissociated by dicyclomine.     

Links Between Reactive Attachment Disorder,Caregiving and Temperament: A Differential Susceptibility Perspective

Abstract

The links between Reactive Attachment Disorder (RAD) and temperament received relatively little research attention, in spite of their clinical and social relevance. Children with RAD sustain disproportionate burdens of early adversity related to their caregiving environment. However, there seem to be important individual differences in susceptibility to adversity, since only a small number of children show signs of RAD. Based on the work of Zeanah and Fox, this review aims to bring new insights to this relevant clinical issue in light of recent research. A differential susceptibility hypothesis will be considered as a promising and innovative approach toward a further understanding of the links between temperament and RAD.     

Tactile spatial acuity differs between fingers: a study comparing two testing paradigms

Tactile spatial acuity (TSA) is a reliable and reproducible measure of somatosensory system function that has been used to study abroad range of subject populations. Although TSA is most often assessed at the fingertip, published studies employing identical stimuli disagree on whether TSA differs between the fingers of neurologically normal subjects. Using a validated grating orientation discrimination task, we determined TSA bilaterally at the index and ring fingers of 16 healthy young adults. Motivated by earlier work, we utilized two stimulus presentation paradigms, the method of constant stimuli (MCS) and a staircase (SC) method. We found that TSA was significantly higher (the discrimination threshold was lower) at the index than at the ring finger, which was consistent with a prior study. Although mean thresholds at both fingers were higher when measured with the SC than with the MCS paradigm, this difference did not reach statistical significance (p = .14). These findings should facilitate both design and interpretation of future studies investigating TSA.     

Approaches to Cognitive Remediation of Neuropsychological Deficits in Schizophrenia: A Review and Meta-Analysis

A review and critique of the literature pertaining to the use of cognitive remediation techniques in patients with schizophrenia is presented. The review is organized into three sections, according to the neuropsychological deficit targeted for remediation: 1) executive-function, 2) attention, and 3) memory. With regards to executive-function, despite an initial report suggesting that Wisconsin Card Sorting Test performance cannot be remediated, subsequent studies suggest that performance can be improved on a variety of dependent measures including perseverative errors, categories achieved, and conceptual level responses. These observations were confirmed by a meta-analytic investigation that revealed large mean effects sizes (d ₊ = 0.96) for these studies. Effect sizes were homogenous across discrepant remediation strategies and dependent measures. With regards to attention, serial scanning can be improved with instruction and reinforcement, whereas there is mixed evidence suggesting that practice-based attention drills can improve performance on measures of sustained attention in schizophrenia. With regards to memory, relatively simple semantic and affective elaborate encoding strategies elevates verbal list-learning memory in patients with schizophrenia to levels consistent with controls. A similar encoding procedure, combined with vigilance training, produces substantial improvement in social cue recognition. Avenues for future research are discussed.     

Unraveling the Relationship between Well-Being,Sustainable Consumption and Nature Relatedness: a Study of University Students

Many empirical studies have found an association between sustainable consumption and well-being. However, the direction of causality between these constructs remains unclear. Well-being could be an antecedent of sustainable consumption or, sustainable consumption a driver of well-being; also, there could be a reciprocal relationship between these two constructs. Alternatively, both well-being and sustainable consumption could be outcomes of another construct that could be masking a relationship between well-being and sustainable consumption. This study aims to advance the well-being and sustainable consumption research by testing these three relationships in a longitudinal study with young consumers (n = 369). The findings show that when controlling for the constructs at Time 1, the relationship between the focal constructs is no longer significant. Results lead to support the hypothesis that sustainable consumption and well-being are explained by a particular trait of the individual, nature relatedness, so that individuals with greater nature relatedness are more likely to adopt a sustainable lifestyle and have greater well-being. Nature relatedness thus acts as a predictor of both focal constructs. This result implies that by nurturing nature relatedness, societies will achieve the double dividend of well-being and sustainability.