Variants of contextual fear conditioning induce differential patterns of Egr-1 activity within the young adult prefrontal cortex

Functional network of contextual and temporal memory has increased amygdala centrality and connectivity with the retrosplenial cortex, thalamus, and hippocampus

In fear conditioning with time intervals between the conditioned (CS) and unconditioned (US) stimuli, a neural representation of the CS must be maintained over time to be associated with the later US. Usually, temporal associations are studied by investigating individual brain regions. It remains unknown, however, the effect of the interval at the network level, uncovering functional connections cooperating for the CS transient memory and its fear association. We investigated the functional network supporting temporal associations using a task in which a 5-s interval separates the contextual CS from the US (CFC-5s). We quantified c-Fos expression in forty-nine brain regions of male rats following the CFC-5s training, used c-Fos correlations to generate functional networks, and analyzed them by graph theory. Control groups were trained in contextual fear conditioning, in which CS and US overlap. The CFC-5s training additionally activated subdivisions of the basolateral, lateral, and medial amygdala; prelimbic, infralimbic, perirhinal, postrhinal, and intermediate entorhinal cortices; ventral CA1 and subiculum. The CFC-5s network had increased amygdala centrality and higher amygdala internal and external connectivity with the retrosplenial cortex, thalamus, and hippocampus. Amygdala and thalamic nuclei were network hubs. Functional connectivity among these brain regions could support CS transient memories and their association.

Contextual fear conditioning with a time interval induces CREB phosphorylation in the dorsal hippocampus and amygdala nuclei that depend on prelimbic cortex activity

In temporal associations, a conditioned stimulus (CS) is separated by a time interval from the unconditioned stimulus (US), which activates the prelimbic cortex (PL) to maintain a CS representation over time. However, it is unknown whether the PL participates, besides the encoding, in the memory consolidation, and thus directly, with activity-dependent changes or indirectly, by modulation of activity-dependent changes in other brain regions. We investigated brain regions supporting the consolidation of associations with intervals and the influence of PL activity in this consolidation process. For this, we observed in Wistar rats the effect of pre-training PL inactivation by muscimol in CREB (cAMP response element-binding protein) phosphorylation, which is essential for memory consolidation, in subdivisions of the medial prefrontal cortex (mPFC), hippocampus, and amygdala 3 h after the training in the contextual fear conditioning (CFC) or CFC with 5-s interval (CFC-5s), fear associations without or with an interval between the CS and US, respectively. Both the CFC-5s and CFC training increased phosphorylation of CREB in the PL and infralimbic cortex (IL); lateral (LA) and basolateral (BLA) amygdala; dorsal CA1 (dCA1); dorsal (dDG), and ventral dentate gyrus, and the CFC-5s training in the central amygdala (CEA). PL activity was necessary for the CREB phosphorylation in the PL, BLA, CEA, dCA1, and dDG only in animals trained in the CFC-5s. The cingulate cortex, ventral CA1, and ventral subiculum did not have learning-induced phosphorylation of CREB. These results suggest that the mPFC, hippocampus, and amygdala support the consolidation of associations with or without intervals and that PL activity influences consolidation in the dorsal hippocampus and amygdala in temporal associations. Thereby, the PL contributes directly and indirectly by modulation to memory consolidation. The time interval engaged the PL early in recent memory consolidation. Results expanded PL's role beyond the time interval and remote memory consolidation.

Sex and age differences in cognitive bias and neural activation in response to cognitive bias testing

Cognitive symptoms of depression, including negative cognitive bias, are more severe in women than in men. Current treatments to reduce negative cognitive bias are not effective and sex differences in the neural activity underlying cognitive bias may play a role. Here we examined sex and age differences in cognitive bias and functional connectivity in a novel paradigm. Male and female rats underwent an 18-day cognitive bias procedure, in which they learned to discriminate between two contexts (shock paired context A, no-shock paired context B), during either adolescence (postnatal day (PD 40)), young adulthood (PD 100), or middle-age (PD 210). Cognitive bias was measured as freezing behaviour in response to an ambiguous context (context C), with freezing levels akin to the shock paired context coded as negative bias. All animals learned to discriminate between the two contexts, regardless of sex or age. However, adults (young adults, middle-aged) displayed a greater negative cognitive bias compared to adolescents, and middle-aged males had a greater negative cognitive bias than middle-aged females. Females had greater neural activation of the nucleus accumbens, amygdala, and hippocampal regions to the ambiguous context compared to males, and young rats (adolescent, young adults) had greater neural activation in these regions compared to middle-aged rats. Functional connectivity between regions involved in cognitive bias differed by age and sex, and only adult males had negative correlations between the frontal regions and hippocampal regions. These findings highlight the importance of examining age and sex when investigating the underpinnings of negative cognitive bias and lay the groundwork for determining what age- and sex-specific regions to target in future cognitive bias studies.

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Middle-aged males had a greater negative cognitive bias than middle-aged females.

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Adult rats displayed a greater negative cognitive bias compared to adolescents.

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Greater neural activity in females than males in limbic and reward regions.

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Greater role of the frontal cortex activation in the cognitive bias of adults.

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Functional connectivity in response to cognitive bias differed by age and sex.

Beyond the hippocampus: The role of parahippocampal-prefrontal communication in context-modulated behavior

Multiple paradigms indicate that the physical environment can influence spontaneous and learned behavior. In rodents, context-dependent behavior is putatively supported by the prefrontal cortex and the medial temporal lobe. A preponderance of the literature has targeted the role of the hippocampus. In addition to the hippocampus proper, the medial temporal lobe also comprises parahippocampal areas, including the perirhinal and postrhinal cortices. These parahippocampal areas directly connect with multiple regions in the prefrontal cortex. The function of these connections, however, is not well understood. This article first reviews the involvement of the perirhinal, postrhinal, and prefrontal cortices in context-dependent behavior in rodents. Then, based on functional and anatomical evidence, we suggest that perirhinal and postrhinal contributions to context-dependent behavior go beyond supporting context representation in the hippocampus. Specifically, we propose that the perirhinal and postrhinal cortices act as a contextual-support network that directly provides contextual and spatial information to the prefrontal cortex. In turn, the perirhinal and postrhinal cortices modulate prefrontal input to the hippocampus in the service of context-guided behavior.

Prefrontal NMDA-receptor antagonism disrupts encoding or consolidation but not retrieval of incidental context learning

The Context Preexposure Facilitation Effect (CPFE) is a variant of contextual fear conditioning in which learning about the context, acquiring a context-shock association, and retrieval of this association occur separately across three phases (context preexposure, immediate-shock training, and retention). We have shown that prefrontal inactivation or muscarinic-receptor antagonism prior to any phase disrupts retention test freezing during the CPFE in adolescent rats (Heroux et al., 2017; Robinson-Drummer et al., 2017). Furthermore, the medial prefrontal cortex (mPFC) is the only region in which robust learning-related expression of the immediate early genes c-Fos, Arc, Egr-1 and Npas4 is observed during immediate-shock training in the CPFE (Asok et al., 2013; Heroux et al., 2018; Schreiber et al., 2014). However, the role of prefrontal NMDA-receptor plasticity in supporting preexposure- and training-day processes of the CPFE is not known. Therefore, the current study examined the effects of intra-mPFC infusion of the NMDA-receptor antagonist MK-801 or saline vehicle prior to context preexposure (Experiment 1) or immediate-shock training (Experiment 2) in adolescent Long-Evans male and female rats. This infusion given prior to context preexposure but not training abolished retention test freezing, with no difference between MK-801-infused rats and non-associative controls preexposed to an alternative context (pooled across drug). These results demonstrate a role of prefrontal NMDA-receptor plasticity in the acquisition and/or consolidation of incidental context learning (i.e., encoded in the absence of reinforcement). In contrast, this plasticity is not required for context retrieval, or acquisition, expression, or consolidation of a context-shock association during immediate-shock training in the CPFE. These experiments add to a growing body of work implicating the mPFC in Pavlovian contextual fear conditioning processes in rodents.

Postoperative cognitive dysfunction is made persistent with morphine treatment in aged rats

Postoperative cognitive dysfunction (POCD) is the collection of cognitive impairments, lasting days to months, experienced by individuals following surgery. Persistent POCD is most commonly experienced by older individuals and is associated with a greater vulnerability to developing Alzheimer's disease, but the underlying mechanisms are not known. It is known that laparotomy (exploratory abdominal surgery) in aged rats produces memory impairments for 4 days. Here we report that postsurgical treatment with morphine extends this deficit to at least 2 months while having no effects in the absence of surgery. Indeed, hippocampal-dependent long-term memory was impaired 2, 4, and 8 weeks postsurgery only in aged, morphine-treated rats. Short-term memory remained intact. Morphine is known to have analgesic effects via μ-opioid receptor activation and neuroinflammatory effects through Toll-like receptor 4 activation. Here we demonstrate that persistent memory deficits were mediated independently of the μ-opioid receptor, suggesting that they were evoked through a neuroinflammatory mechanism and unrelated to pain modulation. In support of this, aged, laparotomized, and morphine-treated rats exhibited increased gene expression of various proinflammatory markers (IL-1β, IL-6, TNFα, NLRP3, HMGB1, TLR2, and TLR4) in the hippocampus at the 2-week time point. Furthermore, central blockade of IL-1β signaling with the specific IL-1 receptor antagonist (IL-1RA), at the time of surgery, completely prevented the memory impairment. Finally, synaptophysin and PSD95 gene expression were significantly dysregulated in the hippocampus of aged, laparotomized, morphine-treated rats, suggesting that impaired synaptic structure and/or function may play a key role in this persistent deficit. This instance of long-term memory impairment following surgery closely mirrors the timeline of persistent POCD in humans and may be useful for future treatment discoveries.

Cholino-ncRNAs modulate sex-specific- and age-related acetylcholine signals

Acetylcholine (ACh) signaling orchestrates mammalian movement, mental capacities, and inflammation. Dysregulated ACh signaling associates with many human mental disorders and neurodegeneration in an individual‐, sex‐, and tissue‐related manner. Moreover, aged patients under anticholinergic therapy show increased risk of dementia, but the underlying molecular mechanisms are incompletely understood. Here, we report that certain cholinergic‐targeting noncoding RNAs, named Cholino‐noncoding RNAs (ncRNAs), can modulate ACh signaling, agonistically or antagonistically, via distinct direct and indirect mechanisms and at different timescales. Cholino‐ncRNAs include both small microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). The former may attenuate translation and/or induce destruction of target mRNAs that code for either ACh‐signaling proteins or transcription factors controlling the expression of cholinergic genes. lncRNAs may block miRNAs via ‘sponging’ events or by competitive binding to the cholinergic target mRNAs. Also, single nucleotide polymorphisms in either Cholino‐ncRNAs or in their recognition sites in the ACh‐signaling associated genes may modify ACh signaling‐regulated processes. Taken together, both inherited and acquired changes in the function of Cholino‐ncRNAs impact ACh‐related deficiencies, opening new venues for individual, sex‐related, and age‐specific oriented research, diagnosis, and therapeutics.

Aggression in BALB/cJ mice is differentially predicted by the volumes of anterior and midcingulate cortex

Anterior cingulate cortex (ACC) and midcingulate cortex (MCC) have been implicated in the regulation of aggressive behaviour. For instance, patients with conduct disorder (CD) show increased levels of aggression accompanied by changes in ACC and MCC volume. However, accounts of ACC/MCC changes in CD patients have been conflicting, likely due to the heterogeneity of the studied populations. Here, we address these discrepancies by studying volumetric changes of ACC/MCC in the BALB/cJ mouse, a model of aggression, compared to an age- and gender-matched control group of BALB/cByJ mice. We quantified aggression in BALB/cJ and BALB/cByJ mice using the resident–intruder test, and related this to volumetric measures of ACC/MCC based on Nissl-stained coronal brain slices of the same animals. We demonstrate that BALB/cJ behave consistently more aggressively (shorter attack latencies, more frequent attacks, anti-social biting) than the control group, while at the same time showing an increased volume of ACC and a decreased volume of MCC. Differences in ACC and MCC volume jointly predicted a high amount of variance in aggressive behaviour, while regression with only one predictor had a poor fit. This suggests that, beyond their individual contributions, the relationship between ACC and MCC plays an important role in regulating aggressive behaviour. Finally, we show the importance of switching from the classical rodent anatomical definition of ACC as cingulate area 2 and 1 to a definition that includes the MCC and is directly homologous to higher mammalian species: clear behaviour-related differences in ACC/MCC anatomy were only observed using the homologous definition.

Cortico-hippocampal Schemas Enable NMDAR-Independent Fear Conditioning in Rats

The neurobiology of memory formation has been studied primarily in experimentally naive animals, but the majority of learning unfolds on a background of prior experience. Considerable evidence now indicates that the brain processes initial and subsequent learning differently. In rodents, a first instance of contextual fear conditioning requires NMDA receptor (NMDAR) activation in the dorsal hippocampus, but subsequent conditioning to another context does not. This shift may result from a change in molecular plasticity mechanisms or in the information required to learn the second task. To clarify how related events are encoded, it is critical to identify which aspect of a first task engages NMDAR-independent learning and the brain regions that maintain this state. Here, we show in rats that the requirement for NMDARs in hippocampus depends neither on prior exposure to context nor footshock alone but rather on the procedural similarity between two conditioning tasks. Importantly, NMDAR-independent learning requires the memory of the first task to remain hippocampus dependent. Furthermore, disrupting memory maintenance in the anterior cingulate cortex after the first task also reinstates NMDAR dependency. These results reveal cortico-hippocampal interactions supporting experience-dependent learning.

Contextual fear retrieval-induced Fos expression across early development in the rat: An analysis using established nervous system nomenclature ontology

The neural circuits underlying the acquisition, retention and retrieval of contextual fear conditioning have been well characterized in the adult animal. A growing body of work in younger rodents indicates that context-mediated fear expression may vary across development. However, it remains unclear how this expression may be defined across the full range of key developmental ages. Nor is it fully clear whether the structure of the adult context fear network generalizes to earlier ages. In this study, we compared context fear retrieval-induced behavior and neuroanatomically constrained immediate early-gene expression across infant (P19), early and late juvenile (P24 and P35), and adult (P90) male Long-Evans rats. We focused our analysis on neuroanatomically defined subregions and nuclei of the basolateral complex of the amygdala (BLA complex), dorsal and ventral portions of the hippocampus and the subregions of the medial prefrontal cortex as defined by the nomenclature of the Swanson (2004) adult rat brain atlas. Relative to controls and across all ages tested, there were greater numbers of Fos immunoreactive (Fos-ir) neurons in the posterior part of the basolateral amygdalar nuclei (BLAp) following context fear retrieval that correlated statistically with the expression of freezing. However, Fos-ir within regions having known connections with the BLA complex was differentially constrained by developmental age: early juvenile, but not adult rats exhibited an increase of context fear-dependent Fos-ir neurons in prelimbic and infralimbic areas, while adult, but not juvenile rats displayed increases in Fos-ir neurons within the ventral CA1 hippocampus. These results suggest that juvenile and adult rodents may recruit developmentally unique pathways in the acquisition and retrieval of contextual fear. This study extends prior work by providing a broader set of developmental ages and a rigorously defined neuroanatomical ontology within which the contextual fear network can be studied further.

Age and experience dependent changes in Egr-1 expression during the ontogeny of the context preexposure facilitation effect (CPFE)

The context preexposure facilitation effect (CPFE) is a variant of contextual fear conditioning in which acquisition of the contextual representation and association of the retrieved contextual memory with an immediate foot-shock are separated by 24 h. During the CPFE, learning- related expression patterns of the early growth response-1 gene (Egr-1) vary based on training phase and brain sub-region in adult and adolescent rats (Asok, Schreiber, Jablonski, Rosen, & Stanton, 2013; Schreiber, Asok, Jablonski, Rosen, & Stanton, 2014; Chakraborty, Asok, Stanton, & Rosen, 2016). The current experiments extended our previous findings by examining Egr-1 expression in infant (PD17) and juvenile (PD24) rats during the CPFE using preexposure protocols involving single-exposure (SE) or multiple-exposure (ME) to context. Following a 5 min preexposure to the training context (i.e. the SE protocol), Egr-1 expression in the medial prefrontal cortex (mPFC), dorsal hippocampus (dHPC) and lateral nucleus of the amygdala (LA) was differentially increased in PD24 rats relative to PD17 rats. In contrast, increased Egr-1 expression following an immediate foot-shock (2s, 1.5 mA) did not differ between PD17 and PD24 rats, and was not learning-related. Interestingly, increasing the number of exposures to the training chamber on the preexposure day (i.e. ME protocol) altered training-day expression such that a learning-related increase in expression was observed in the mPFC in PD24 but not PD17 rats. Together, these results illustrate a clear maturation of Egr-1 expression that is both age- and experience-dependent. In addition, the data suggest that regional activity and plasticity within the mPFC on the preexposure but not the training day may contribute to the ontogenetic profile of the effect. Further studies are necessary to elucidate the causal role of sub-region-specific neuroplasticity in the ontogeny of the CPFE.

Differential expression of the immediate early genes c-Fos, Arc, Egr-1, and Npas4 during long-term memory formation in the context preexposure facilitation effect (CPFE)

The context preexposure facilitation effect (CPFE) is a contextual fear conditioning paradigm in which learning about the context, acquiring the context-shock association, and retrieving/expressing contextual fear are temporally dissociated into three distinct phases (context preexposure, immediate-shock training, and retention). The current study examined changes in the expression of plasticity-associated immediate early genes (IEGs) during context and contextual fear memory formation on the preexposure and training days of the CPFE, respectively. Using adolescent Long-Evans rats, preexposure and training day expression of the IEGs c-Fos, Arc, Egr-1, and Npas4 in the medial prefrontal cortex (mPFC), dorsal hippocampus (dHPC), and basolateral amygdala (BLA) was analyzed using qPCR as an extension of previous studies from our lab examining Egr-1 via in situ hybridization (Asok, Schreiber, Jablonski, Rosen, & Stanton, 2013; Schreiber, Asok, Jablonski, Rosen, & Stanton, 2014). In Expt. 1, context preexposure induced expression of c-Fos, Arc, Egr-1 and Npas4 significantly above that of home-cage (HC) controls in all three regions. In Expt. 2, immediate-shock was followed by a post-shock freezing test, resulting in increased mPFC c-Fos expression in a group preexposed to the training context but not a control group preexposed to an alternate context, indicating expression related to associative learning. This was not seen with other IEGs in mPFC or with any IEG in dHPC or BLA. Finally, when the post-shock freezing test was omitted in Expt. 3, training-related increases were observed in prefrontal c-Fos, Arc, Egr-1, and Npas4, hippocampal c-Fos, and amygdalar Egr-1 expression. These results indicate that context exposure in a post-shock freezing test re-engages IEG expression that may obscure associatively-induced expression during contextual fear conditioning. Additionally, these studies suggest a key role for long-term synaptic plasticity in the mPFC in supporting the CPFE.

Tet1 overexpression leads to anxiety-like behavior and enhanced fear memories via the activation of calcium-dependent cascade through Egr1 expression in mice

Ten-eleven translocation methylcytosine dioxygenase 1 (Tet1) initiates DNA demethylation by converting 5-methylcytosine (5-mC) to 5-hydroxymethylcytosine (5-hmC) at CpG-rich regions of genes, which have key roles in adult neurogenesis and memory. In addition, the overexpression of Tet1 with 5-hmC alteration in patients with psychosis has also been reported, for instance in schizophrenia and bipolar disorders. The mechanism underlying Tet1 overexpression in the brain; however, is still elusive. In the present study, we found that Tet1-transgenic (Tet1-TG) mice displayed abnormal behaviors involving elevated anxiety and enhanced fear memories. We confirmed that Tet1 overexpression affected adult neurogenesis with oligodendrocyte differentiation in the hippocampal dentate gyrus of Tet1-TG mice. In addition, Tet1 overexpression induced the elevated expression of immediate early genes, such as Egr1, c-fos, Arc, and Bdnf, followed by the activation of intracellular calcium signals (i.e., CamKII, ERK, and CREB) in prefrontal and hippocampal neurons. The expression of GABA receptor subunits (Gabra2 and Gabra4) fluctuated in the prefrontal cortex and hippocampus. We evaluated the effects of Tet1 overexpression on intracellular calcium-dependent cascades by activating the Egr1 promoter in vitro Tet1 enhanced Egr1 expression, which may have led to alterations in Gabra2 and Gabra4 expression in neurons. Taken together, we suggest that the Tet1 overexpression in our Tet1-TG mice can be applied as an effective model for studying various stress-related diseases that show hyperactivation of intracellular calcium-dependent cascades in the brain.-Kwon, W., Kim, H.-S., Jeong, J., Sung, Y., Choi, M., Park, S., Lee, J., Jang, S., Kim, S. H., Lee, S., Kim, M. O., Ryoo, Z. Y. Tet1 overexpression leads to anxiety-like behavior and enhanced fear memories via the activation of calcium-dependent cascade through Egr1 expression in mice.

Novelty and fear conditioning induced gene expression in high and low states of anxiety

Emotional states influence how stimuli are interpreted. High anxiety states in humans lead to more negative, threatening interpretations of novel information, typically accompanied by activation of the amygdala. We developed a handling protocol that induces long-lasting high and low anxiety-like states in rats to explore the role of state anxiety on brain activation during exposure to a novel environment and fear conditioning. In situ hybridization of the inducible transcription factor Egr-1 found increased gene expression in the lateral nucleus of the amygdala (LA) following exposure to a novel environment and contextual fear conditioning in high anxiety-like rats. In contrast, low state anxiety-like rats did not generate Egr-1 increases in LA when placed in a novel chamber. Egr-1 expression was also examined in the dorsal hippocampus and prefrontal cortex. In CA1 of the hippocampus and medial prefrontal cortex (mPFC), Egr-1 expression increased in response to novel context exposure and fear conditioning, independent of state anxiety level. Furthermore, in mPFC, Egr-1 in low anxiety-like rats was increased more with fear conditioning than novel exposure. The current series of experiments show that brain areas involved in fear and anxiety-like states do not respond uniformly to novelty during high and low states of anxiety.

Differential involvement of the medial prefrontal cortex across variants of contextual fear conditioning

The context preexposure facilitation effect (CPFE) is a contextual fear conditioning paradigm in which learning about the context, acquiring the context-shock association, and retrieving/expressing contextual fear are temporally dissociated into three distinct phases. In contrast, learning about the context and the context-shock association happens concurrently in standard contextual fear conditioning (sCFC). By infusing the GABA_A receptor agonist muscimol into medial prefrontal cortex (mPFC) in adolescent Long-Evans rats, the current set of experiments examined the functional role of the mPFC in each phase of the CPFE and sCFC. In the CPFE, the mPFC is necessary for the following: acquisition and/or consolidation of context memory (Experiment 1), reconsolidation of a context memory to include shock (Experiment 2), and expression of contextual fear memory during a retention test (Experiment 3). In contrast to the CPFE, inactivation of the mPFC prior to conditioning in sCFC has no effect on acquisition, consolidation, or retention of a contextual fear memory (Experiment 4). Interestingly, the mPFC is not required for acquiring a context-shock association (measured by post-shock freezing) in the CPFE or sCFC (Experiment 2b and 4). Taken together, these results indicate that the mPFC is differentially recruited across stages of learning and variants of contextual fear conditioning (CPFE versus sCFC). More specifically, separating out learning about the context and the context-shock association necessitates activation of the medial prefrontal cortex during early learning and/or consolidation.

Antagonism of muscarinic acetylcholine receptors in medial prefrontal cortex disrupts the context preexposure facilitation effect

Cholinergic function plays a role in a variant of context fear conditioning known as the context preexposure facilitation effect (CPFE; Robinson-Drummer, Dokovna, Heroux, & Stanton, 2016). In the CPFE, acquisition of a context representation, the context-shock association, and expression of context fear occur across successive phases, usually 24h apart. Systemic administration of scopolamine, a muscarinic acetylcholine receptor antagonist, prior to each phase (context preexposure, immediate-shock training, and testing) disrupts the CPFE in juvenile rats (Robinson-Drummer et al., 2016). Dorsal hippocampal (dHPC) cholinergic function contributes significantly to this effect, as local infusion of scopolamine into the dHPC prior to any individual phase of the CPFE produces a disruption identical to systemic administration (Robinson-Drummer et al., 2016). The current experiment extended these findings to another forebrain region implicated in the CPFE, the medial prefrontal cortex (mPFC). Adolescent rats received bilateral infusions of scopolamine (35μg/side) or PBS 10min before all three phases of the CPFE or only prior to a single phase. Intra-mPFC administration of scopolamine prior to all three phases significantly impaired fear conditioning suggesting that mPFC cholinergic function is necessary for successful CPFE performance. Analyses of the individual infusion days revealed a significant impairment of the CPFE when infusions occurred prior to preexposure or training (i.e. immediate footshock) but not prior to testing. In total, these findings suggests a role of mPFC cholinergic function in the acquisition and/or consolidation of a contextual representation and the context-shock association but not in retrieval or expression of fear memory. Implications for mPFC involvement in contextual fear conditioning and neurological dysfunction following neonatal alcohol exposure are discussed.