In mouse hippocampal slices, long-term potentiation (LTP) at Schaffer collateral fiber synapses onto CA1 pyramidal cells could be induced by brief trains of 5-Hz synaptic stimulation (30 s) or by ...longer trains of 5-Hz stimulation (3 min) delivered during
β-adrenergic receptor activation. In contrast, 5-Hz stimulation, either alone or in the presence of the
β-adrenergic receptor agonist isoproterenol, failed to induce LTP at associational–commissural (assoc–com) fiber synapses onto CA3 pyramidal cells. Our results suggest that although CA3 pyramidal cells give rise to both the Schaffer collateral fiber synapses in CA1 and the assoc–com fiber synapses in CA3, the induction of LTP at these synapses may be regulated by different activity- and modulatory neurotransmitter-dependent processes.
Studies of neuropsychological patients and experimental animals have demonstrated that the striatum plays a role in implicit habit learning. Here, we examined the performance of patients with ...Parkinson's disease (PD) on a concurrent discrimination task that can be learned implicitly by neurologically intact individuals. Participants viewed a pair of shapes on each trial and, under a timed deadline, guessed which one concealed a smiling face. About half the control participants exhibited minimal awareness of the cue-reward relationships as assessed by a post-test evaluation. Nevertheless, these participants were able to perform the discrimination task; there was no correlation between awareness and performance on the task. In contrast, minimally aware patients with PD showed no learning, whereas those who were more aware of the relationships performed as well as control participants on the task. There was a significant correlation between awareness and performance in patients with PD. These data support the idea that the basal ganglia play a role in implicit habit learning and underscore the importance of using tests of awareness to assess the content and process of learning in humans.
Through protein interactions mediated by their cytoplasmic C termini the GluN2A and GluN2B subunits of NMDA receptors (NMDARs) have a key role in the formation of NMDAR signaling complexes at ...excitatory synapses. Although these signaling complexes are thought to have a crucial role in NMDAR-dependent forms of synaptic plasticity such as long-term potentiation (LTP), the role of the C terminus of GluN2A in coupling NMDARs to LTP enhancing and/or suppressing signaling pathways is unclear. To address this issue we examined the induction of LTP in the hippocampal CA1 region in mice lacking the C terminus of endogenous GluN2A subunits (GluN2Asuperscript deltaC/deltaC. Our results show that truncation of GluN2A subunits produces robust, but highly frequency-dependent, deficits in LTP and a reduction in basal levels of extracellular signal regulated kinase 2 (ERK2) activation and phosphorylation of AMPA receptor GluA1 subunits at a protein kinase A site (serine 845). Consistent with the notion that these signaling deficits contribute to the deficits in LTP in GluN2Asuperscript deltaC/deltaC mice, activating ERK2 and increasing GluA1 S845 phosphorylation through activation of Beta-adrenergic receptors rescued the induction of LTP in these mutants. Together, our results indicate that the capacity of excitatory synapses to undergo plasticity in response to different patterns of activity is dependent on the coupling of specific signaling pathways to the intracellular domains of the NMDARs and that abnormal plasticity resulting from mutations in NMDARs can be reduced by activation of key neuromodulatory transmitter receptors that engage converging signaling pathways.
Background Long-term acute care (LTAC) facilities admit patients with complex, advanced disease states. Study aims were to determine the burden posed on hospitals associated with LTAC exposure and ...analyze the differences between “present on admission” (POA) multidrug-resistant (MDR), gram-negative organisms (GNO) and POA MDR gram-positive organisms (GPO). Methods A multicenter retrospective study was conducted in 13 hospitals from southeast Michigan, from September 1, 2008, to August 31, 2009. Cultures obtained in the first 72 hours of hospitalization (ie, POA) of MDR-GPO and MDR-GNO were reviewed. LTAC exposures in the previous 6 months and direct admission from a LTAC were recorded. Results Overall, 5,297 patients with 7,147 MDR POA cultures were analyzed: 2,619 (36.6%) were MDR-GNO, and 4,528 (63.4%) were MDR-GPO. LTAC exposure in the past 6 months was present in 251 (5.2%) infectious episodes and was significantly more common among POA MDR-GNO than MDR-GPO (158 8.6% and 94 3.1%, respectively, odds ratio, 2.87; P < .001). Recent LTAC exposure was strongly associated with both carbapenem-resistant Enterobacteriaceae (CRE) (31.6% of all CRE cases, P < .001) and Acinetobacter baumannii (14.9% of all A baumannii cases, P < .001). Conclusion Nearly 10% of MDR-GNO POA had recent LTAC exposure. Hospital efforts to control the spread of MDR-GNO should focus on collaborations and communications with referring LTACs and interventions targeted towards patients with recent LTAC exposure.
The induction of long-term potentiation (LTP) and long-term depression (LTD) at excitatory synapses in the hippocampus can be strongly modulated by patterns of synaptic stimulation that otherwise ...have no direct effect on synaptic strength. Likewise, patterns of synaptic stimulation that induce LTP or LTD not only modify synaptic strength but can also induce lasting changes that regulate how synapses will respond to subsequent trains of stimulation. Collectively known as metaplasticity, these activity-dependent processes that regulate LTP and LTD induction allow the recent history of synaptic activity to influence the induction of activity-dependent changes in synaptic strength and may thus have an important role in information storage during memory formation. To explore the cellular and molecular mechanisms underlying metaplasticity, we investigated the role of metaplasticity in the induction of LTP by theta-frequency (5-Hz) synaptic stimulation in the hippocampal CA1 region. Our results show that brief trains of theta-frequency stimulation not only induce LTP but also activate a process that inhibits the induction of additional LTP at potentiated synapses. Unlike other forms of metaplasticity, the inhibition of LTP induction at potentiated synapses does not appear to arise from activity-dependent changes in NMDA receptor function, does not require nitric oxide signaling, and is strongly modulated by beta-adrenergic receptor activation. Together with previous findings, our results indicate that mechanistically distinct forms of metaplasticity regulate LTP induction and suggest that one way modulatory transmitters may act to regulate synaptic plasticity is by modulating metaplasticity.
Own body perception, and differentiating and comparing one's body to another person's body, are common cognitive functions that have relevance for self‐identity and social interactions. In several ...psychiatric conditions, including anorexia nervosa, body dysmorphic disorder, gender dysphoria, and autism spectrum disorder, self and own body perception, as well as aspects of social communication are disturbed. Despite most of these conditions having skewed prevalence sex ratios, little is known about whether the neural basis of own body perception differs between the sexes. We addressed this question by investigating brain activation using functional magnetic resonance imaging during a Body Perception task in 15 male and 15 female healthy participants. Participants viewed their own body, bodies of same‐sex, or opposite‐sex other people, and rated the degree that they appeared like themselves. We found that men and women did not differ in the pattern of brain activation during own body perception compared to a scrambled control image. However, when viewing images of other bodies of same‐sex or opposite‐sex, men showed significantly stronger activations in attention‐related and reward‐related brain regions, whereas women engaged stronger activations in striatal, medial‐prefrontal, and insular cortices, when viewing the own body compared to other images of the opposite sex. It is possible that other body images, particularly of the opposite sex, may be of greater salience for men, whereas images of own bodies may be more salient for women. These observations provide tentative neurobiological correlates to why women may be more vulnerable than men to conditions involving own body perception.
Depression is a commonly occurring symptom in obsessive-compulsive disorder (OCD), and is associated with worse functional impairment, poorer quality of life, and poorer treatment response. ...Understanding the underlying neurochemical and connectivity-based brain mechanisms of this important symptom domain in OCD is necessary for development of novel, more globally effective treatments. To investigate biopsychological mechanisms of comorbid depression in OCD, we examined effective connectivity and neurochemical signatures in the pregenual anterior cingulate cortex (pACC), a structure known to be involved in both OCD and depression. Resting-state functional magnetic resonance imaging (fMRI) and
H magnetic resonance spectroscopy (MRS) data were obtained from participants with OCD (n=49) and healthy individuals of equivalent age and sex (n=25). Granger causality-based effective (directed) connectivity was used to define causal networks involving the right and left pACC. The interplay between fMRI connectivity,
H MRS and clinical data was explored by applying moderation and mediation analyses. We found that the causal influence of the right dorsal anterior midcingulate cortex (daMCC) on the right pACC was significantly lower in the OCD group and showed significant correlation with depressive symptom severity in the OCD group. Lower and moderate levels of glutamate (Glu) in the right pACC significantly moderated the interaction between right daMCC-pACC connectivity and depression severity. Our results suggest a biochemical-connectivity-psychological model of pACC dysfunction contributing to depression in OCD, particularly involving intracingulate connectivity and glutamate levels in the pACC. These findings have implications for potential molecular and network targets for treatment of this multi-faceted psychiatric condition.
Anorexia nervosa (AN) and body dysmorphic disorder (BDD) share distorted perceptions of appearance with extreme negative emotion, yet the neural phenotypes of emotion processing remain underexplored ...in them, and they have never been directly compared. We sought to determine if shared and disorder-specific fronto-limbic connectivity patterns characterize these disorders. FMRI data was obtained from three unmedicated groups: BDD (
= 32), weight-restored AN (
= 25), and healthy controls (HC;
= 37), while they viewed fearful faces and rated their own degree of fearfulness in response. We performed dynamic effective connectivity modeling with medial prefrontal cortex (mPFC), rostral anterior cingulate cortex (rACC), and amygdala as regions-of-interest (ROI), and assessed associations between connectivity and clinical variables. HCs exhibited significant within-group bidirectional mPFC-amygdala connectivity, which increased across the blocks, whereas BDD participants exhibited only significant mPFC-to-amygdala connectivity (
< 0.05, family-wise error corrected). In contrast, participants with AN lacked significant prefrontal-amygdala connectivity in either direction. AN showed significantly weaker mPFC-to-amygdala connectivity compared to HCs (
= 0.0015) and BDD (
= 0.0050). The mPFC-to-amygdala connectivity was associated with greater subjective fear ratings (
= 0.11,
= 0.0016), eating disorder symptoms (
= 0.33,
= 0.0029), and anxiety (
= 0.29,
= 0.0055) intensity scores. Our findings, which suggest a complex nosological relationship, have implications for understanding emotion regulation circuitry in these related psychiatric disorders, and may have relevance for current and novel therapeutic approaches.
Abstract Individuals with body dysmorphic disorder (BDD) and obsessive–compulsive disorder (OCD) are categorized within the same major diagnostic group and both show regional brain hyperactivity in ...the orbitofrontal cortex (OFC) and the basal ganglia during symptom provocation. While recent studies revealed that degree connectivity of these areas is abnormally high in OCD and positively correlates with symptom severity, no study has investigated degree connectivity in BDD. We used functional magnetic resonance imaging (fMRI) to compare the local and distant degree of functional connectivity in all brain areas between 28 unmedicated BDD participants and 28 demographically matched healthy controls during a face-processing task. Correlational analyses tested for associations between degree connectivity and symptom severity assessed by the BDD version of the Yale-Brown obsessive–compulsive scale (BDD-Y-BOCS). Reduced local amygdalar connectivity was found in participants with BDD. No differences in distant connectivity were found. BDD-Y-BOCS scores significantly correlated with the local connectivity of the posterior-lateral OFC, and distant connectivity of the posterior-lateral and post-central OFC, respectively. These findings represent preliminary evidence that individuals with BDD exhibit brain-behavioral associations related to obsessive thoughts and compulsive behaviors that are highly similar to correlations previously found in OCD, further underscoring their related pathophysiology. This relationship could be further elucidated through investigation of resting-state functional connectivity in BDD, ideally in direct comparison with OCD and other obsessive–compulsive and related disorders.
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