Insights into a molecular switch that gates sensory neuron synapses during habituation in Aplysia

This review focuses on synaptic depression at sensory neuron-to-motor neuron synapses in the defensive withdrawal circuit of Aplysia as a model system for analysis of molecular mechanisms of sensory gating and habituation. We address the following topics:1. Of various possible mechanisms that might underlie depression at these sensory neuron-to-motor neuron synapses in Aplysia, historically the most widely-accepted explanation has been depletion of the readily releasable pool of vesicles. Depletion is also believed to account for synaptic depression at long interstimulus intervals in a variety of other systems.2. Multiple lines of evidence now indicate that vesicle depletion is not an important contributing mechanism to synaptic depression at Aplysia sensory neuron-to-motor neuron synapses. More generally, it appears that vesicle depletion does not contribute substantially to depression that occurs with those stimulus patterns that are typically used in studying behavioral habituation.3. Recent evidence suggests that at these sensory neuron-to-motor neuron synapses in Aplysia, synaptic depression is mediated by an activity-dependent, but release-independent, switching of individual release sites to a silent state. This switching off of release sites is initiated by Ca²⁺ influx during individual action potentials. We discuss signaling proteins that may be regulated by Ca²⁺ during the silencing of release sites that underlies synaptic depression.4. Bursts of 2–4 action potentials in presynaptic sensory neurons in Aplysia prevent the switching off of release sites via a mechanism called “burst-dependent protection” from synaptic depression.5. This molecular switch may explain the sensory gating that allows animals to discriminate which stimuli are innocuous and appropriate to ignore and which stimuli are more important and should continue to elicit responses.     

Accountability and dignity: Ethical issues in forensic and correctional practice

Our aim in the special issue is to address some of the more abstract and fundamental ethical problems evident in the criminal justice system and to inquire into their significance for those individuals who assess and deliver rehabilitation programs to offenders. In order to provide an appropriate theoretical framework for an investigation of ethical concerns in the forensic and correctional practice domains, we first outline an ethical framework that is intended to help practitioners reflect systematically on their practice [Ward, T., & Syversen, K., (2009). Vulnerable agency and human dignity: An ethical framework for forensic practice. Aggression and Violent Behavior, 14, 94–105]. Second, we explicitly examine the relationship between two normative frameworks evident within the criminal justice system, punishment and rehabilitation, and inquire into their relationship. Finally, we briefly describe each of the papers comprising the special issue.     

Does gratitude to R for ϕ-ing imply gratitude that R ϕ-ed?

Philosophical Studies - Many find it plausible that for a given beneficiary, Y, benefactor, R, and action, ?, Y’s being grateful to R for ?-ing implies Y’s being grateful that...     

Does Social Drinking Affect Memory in Older Adults?

The present study examines the possible impact of drinking status on objective memory performance in older adults. Subjects were 214 seniors who were participating in a memory research project and had been screened for cognitive impairment. Cognitive measures included the California Verbal Learning Test (CVLT) and the visual reproduction subtest of the Wechsler Memory Scale–Revised. Drinking status classification (i.e., abstinent, past drinker, light drinker, moderate drinker, and problem drinker) was based on the Alcohol Use Disorder Identification Test scores for the past year and report of past drinking history. Very few subjects were classified in the problem group, with the majority abstaining in the past year. Findings indicated that problem drinkers differed from moderate social drinkers on immediate visual memory, and also had a trend for more retroactive interference on the CVLT. There was no evidence that moderate social drinking (average 13.6 standard drinks) had an adverse impact on memory in this population.     

Iris Murdoch's Mortal Asymmetry

Iris Murdoch holds that the best sort of life is a figurative death of the self. This figurative death is informed by an acceptance of real mortality. A recognition of mortality is supposed to help redirect our attention away from self and towards others. Yet these others are also mortal but (unlike the self) remain worthy of love, care and consideration. That is to say, the significance of mortality for Murdoch depends on whose mortality is at issue, whether it is the mortality of the self or of the other that is in question. My rejection of two ways of making sense of this self/other asymmetry is used to motivate the view that her attitude towards death requires a prior commitment to unselfing. And this is a problematic moral project.     

Covert orienting to the locations of targets and distractors: Effects on response channel activation in a flanker task

The role of covert orienting of attention in response channel activation was examined using the flanker interference and precueing paradigms. Four experiments assessed the influence of distractors on the discrimination of a target colour patch under cueing conditions (three with non-informative, exogenous cues and one with informative, endogenous cues) that modulated attention at the flanker or target locations. Across all of the experiments, the amount of interference generated by the distractors was not modulated by the facilitation and inhibition of return induced by spatial attention precues. These results are consistent with previous reports of patients with neglect, which demonstrated that flanker interference proceeds at unattended locations (Audet, Bub, & Lecours, 1991; Cohen, Ivry, Rafal, & Kohn, 1995), and they suggest that response channel activation can occur independently from spatial attention.     

Neurocognitive correlates of white matter quality in adolescent substance users

Background

Progressive myelination during adolescence implicates an increased vulnerability to neurotoxic substances and enduring neurocognitive consequences. This study examined the cognitive manifestations of altered white matter microstructure in chronic marijuana and alcohol-using (MJ + ALC) adolescents.

Methods

Thirty-six MJ + ALC adolescents (ages 16–19) and 36 demographically similar controls were evaluated with diffusion tensor imaging (Bava et al., 2009) and neurocognitive tests. Regions of group difference in fractional anisotropy (FA) and mean diffusivity (MD) were analyzed in relation to cognitive performance.

Results

In users, lower FA in temporal areas related to poorer performance on attention, working memory, and speeded processing tasks. Among regions where users had higher FA than controls, occipital FA was positively associated with working memory and complex visuomotor sequencing, whereas FA in anterior regions was negatively associated with verbal memory performance.

Conclusions

Findings suggest differential influences of white matter development on cognition in MJ + ALC using adolescents than in non-using peers. Neuroadaptation may reflect additive and subtractive responses to substance use that are complicated by competing maturational processes.