Memory Retrieval Has a Dynamic Influence on the Maintenance Mechanisms That Are Sensitive to ζ-Inhibitory Peptide (ZIP).

In neuroscientists' attempts to understand the long-term storage of memory, topics of particular importance and interest are the cellular and system mechanisms of maintenance (e.g., those sensitive to ζ-inhibitory peptide, ZIP) and those induced by memory retrieval (i.e., reconsolidation). Much is known about each of these processes in isolation, but less is known concerning how they interact. It is known that ZIP sensitivity and memory retrieval share at least some molecular targets (e.g., recycling α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, AMPA, receptors to the plasma membrane); conversely, the fact that sensitivity to ZIP emerges only after consolidation ends suggests that consolidation (and by extension reconsolidation) and maintenance might be mutually exclusive processes, the onset of one canceling the other. Here, we use conditioned taste aversion (CTA) in rats, a cortically dependent learning paradigm, to test this hypothesis. First, we demonstrate that ZIP infusions into gustatory cortex begin interfering with CTA memory 43-45 h after memory acquisition-after consolidation ends. Next, we show that a retrieval trial administered after this time point interrupts the ability of ZIP to induce amnesia and that ZIP's ability to induce amnesia is reengaged only 45 h after retrieval. This pattern of results suggests that memory retrieval and ZIP-sensitive maintenance mechanisms are mutually exclusive and that the progression from one to the other are similar after acquisition and retrieval. They also reveal concrete differences between ZIP-sensitive mechanisms induced by acquisition and retrieval: the latency with which ZIP-sensitive mechanisms are expressed differ for the two processes. SIGNIFICANCE STATEMENT: Memory retrieval and the molecular mechanisms that are sensitive to ζ-inhibitory peptide (ZIP) are the few manipulations that have been shown to effect memory maintenance. Although much is known about their effect on maintenance separately, it is unknown how they interact. Here, we describe a model for the interaction between memory retrieval and ZIP-sensitive mechanisms, showing that retrieval trials briefly (i.e., for 45 h) interrupt these mechanisms. ZIP sensitivity emerges across a similar time window after memory acquisition and retrieval; the maintenance mechanisms that follow acquisition and retrieval differ, however, in the latency with which the impact of ZIP is expressed.

Assessing a Science Graduate School Recruitment Symposium.

Ciencia Puerto Rico, a non-profit organization dedicated to promoting science, research and scientific education among Latinos, organized an educational symposium to provide college science majors the tools, opportunities and advice to pursue graduate degrees and succeed in the STEM disciplines. In this article we share our experiences and lessons learned, for others interested in developing large-scale events to recruit underrepresented minorities to STEM and in evaluating the effectiveness of these efforts.

Genetically induced cholinergic hyper-innervation enhances taste learning.

Acute inhibition of acetylcholine (ACh) has been shown to impair many forms of simple learning, and notably conditioned taste aversion (CTA). The most adhered-to theory that has emerged as a result of this work - that ACh increases a taste's perceived novelty, and thereby its associability - would be further strengthened by evidence showing that enhanced cholinergic function improves learning above normal levels. Experimental testing of this corollary hypothesis has been limited, however, by side-effects of pharmacological ACh agonism and by the absence of a model that achieves long-term increases in cholinergic signaling. Here, we present this further test of the ACh hypothesis, making use of mice lacking the p75 pan-neurotrophin receptor gene, which show a resultant over-abundance of cholinergic neurons in sub-regions of the basal forebrain (BF). We first demonstrate that the p75-/- abnormality directly affects portions of the CTA circuit, locating mouse gustatory cortex (GC) using a functional assay and then using immunohistochemisty to demonstrate cholinergic hyper-innervation of GC in the mutant mice - hyper-innervation that is unaccompanied by changes in cell numbers or compensatory changes in muscarinic receptor densities. We then demonstrate that both p75-/- and wild-type (WT) mice learn robust CTAs, which extinguish more slowly in the mutants. Further testing to distinguish effects on learning from alterations in memory retention demonstrate that p75-/- mice do in fact learn stronger CTAs than WT mice. These data provide novel evidence for the hypothesis linking ACh and taste learning.

State dependence of olfactory perception as a function of taste cortical inactivation.

As anyone who has suffered through a head cold knows, food eaten when the olfactory system is impaired tastes 'wrong', an experience that leads many to conclude that taste stimuli are processed normally only when the olfactory system is unimpaired. Evidence that the taste system influences olfactory perception, however, has been vanishingly rare. We found just such an influence; if taste cortex was inactivated when an odor was first presented, later presentations were properly appreciated only if taste cortex was again inactivated.

Modulation of affect after chronic exposure to the anabolic steroid 17alpha-methyltestosterone in adult mice.

A battery of behavioral tasks in C57BL/6J mice was used to assess changes in affective components of behavior after systemic exposure to the anabolic-androgenic steroid (AAS) 17alpha-methyltestosterone (7.5 mg/kg). Gonadal weight in both sexes was reduced after 16 days of AAS exposure. Changes in discrete components of social behaviors were observed. No changes were recorded in the elevated plus-maze, the light-dark transition, and defensive behavior tests on exposure to 17alpha-methyltestosterone. When compared with controls, AAS-exposed females received a greater number of shocks, and AAS-exposed males displayed a shorter recovery time to consume water after a negative reinforcer in the modified Vogel conflict test. Results show that systemic exposure to a single AAS modified social behaviors, whereas minimal effects on anxiety-related behaviors were observed according to sex.