The role of reuniens and rhomboid thalamic nuclei in spatial memory

Spatial working memory is the ability to encode and temporarily store information for future retrieval to guide behavioral responses. Two areas of the brain that are important for this process are prefrontal cortex (PFC) and hippocampus. The hippocampus has strong connections to medial PFC, however there are no direct return projections from medial PFC to hippocampus. The reuniens (Re) and rhomboid (Rh) nuclei of ventral midline thalamus have anatomical connections with PFC and hippocampus. This dissertation sought to provide behavioral evidence for the role of the ventral midline thalamic nuclei in spatial working memory. Four experiments were conducted in rats using different methods to elucidate the role of Re and Rh nuclei in memory. Experiment 1 temporarily inactivated Re and Rh with pharmacological manipulations. Experiment 2 used permanent excitotoxic lesions to selectively damage Re or Rh nuclei. Experiment 3 used similar lesions on areas surrounding Re and Rh to rule out any potential contributions of these areas and Experiment 4 used event-related deep brain stimulation in Re and Rh to distinguish when during the memory process these nuclei are important. Results revealed impairments for the Re and Rh nuclei on different behavioral measures of spatial working memory that depend on the proper functioning of PFC and/or hippocampus. Temporal specificity was found for the storage and retrieval stages of the delayed nonmatching to position measure (DNMTP) of spatial working memory. These findings provide evidence that the ventral midline thalamic nuclei play an important role in spatial working memory, specifically for the communication of information across memory delays to guide memory responses

Role of Reuniens Nucleus Projections to the Medial Prefrontal Cortex and to the Hippocampal Pyramidal CA1 Area in Associative Learning

We studied the interactions between short- and long-term plastic changes taking place during the acquisition of a classical eyeblink conditioning and following high-frequency stimulation (HFS) of the reuniens nucleus in behaving mice. Synaptic changes in strength were studied at the reuniens-medial prefrontal cortex (mPFC) and the reuniens-CA1 synapses. Input/output curves and a paired-pulse study enabled determining the functional capabilities of the two synapses and the optimal intensities to be applied at the reuniens nucleus during classical eyeblink conditioning and for HFS applied to the reuniens nucleus. Animals were conditioned using a trace paradigm, with a tone as conditioned stimulus (CS) and an electric shock to the trigeminal nerve as unconditioned stimulus (US). A single pulse was presented to the reuniens nucleus to evoke field EPSPs (fEPSPs) in mPFC and CA1 areas during the CS-US interval. No significant changes in synaptic strength were observed at the reuniens-mPFC and reuniens-CA1 synapses during the acquisition of eyelid conditioned responses (CRs). Two successive HFS sessions carried out during the first two conditioning days decreased the percentage of CRs, without evoking any long-term potentiation (LTP) at the recording sites. HFS of the reuniens nucleus also prevented the proper acquisition of an object discrimination task. A subsequent study revealed that HFS of the reuniens nucleus evoked a significant decrease of paired-pulse facilitation. In conclusion, reuniens nucleus projections to prefrontal and hippocampal circuits seem to participate in the acquisition of associative learning through a mechanism that does not required the development of LTP

The nucleus reuniens: a key node in the neurocircuitry of stress and depression

Uncorrected proofThe hippocampus and prefrontal cortex (PFC) are connected in a reciprocal manner: whereas the hippocampus projects directly to the PFC, a polysynaptic pathway that passes through the nucleus reuniens (RE) of the thalamus relays inputs from the PFC to the hippocampus. The present study demonstrates that lesioning and/or inactivation of the RE reduces coherence in the PFC-hippocampal pathway, provokes an antidepressant-like behavioral response in the forced swim test and prevents, but does not ameliorate, anhedonia in the chronic mild stress (CMS) model of depression. Additionally, RE lesioning before CMS abrogates the well-known neuromorphological and endocrine correlates of CMS. In summary, this work highlights the importance of the reciprocal connectivity between the hippocampus and PFC in the establishment of stress-induced brain pathology and suggests a role for the RE in promoting resilience to depressive illness.Greece for providing sertraline. This work was supported by an ‘Education and Lifelong Learning, Supporting Postdoctoral Researchers’, co-financed by the European Social Fund (ESF) and the General Secretariat for Research and Technology, Greece, the Life and Health Sciences Research Institute (ICVS), ON.2—O NOVO NORTE—North Portugal Regional Operational Program 2007/2013 of the National Strategic Reference Framework (NSRF) 2007/2013 through the European Regional Development Fund (ERDF), the Portuguese Foundation for Science and Technology (FCT; grant no. NMC-113934) and an InEurope program funded by International Brain Research Organizationinfo:eu-repo/semantics/publishedVersio

Thalamic neuromodulation and its implications for executive networks

The thalamus is a key structure that controls the routing of information in the brain. Understanding modulation at the thalamic level is critical to understanding the flow of information to brain regions involved in cognitive functions, such as the neocortex, the hippocampus, and the basal ganglia. Modulators contribute the majority of synapses that thalamic cells receive, and the highest fraction of modulator synapses is found in thalamic nuclei interconnected with higher order cortical regions. In addition, disruption of modulators often translates into disabling disorders of executive behavior. However, modulation in thalamic nuclei such as the midline and intralaminar groups, which are interconnected with forebrain executive regions, has received little attention compared to sensory nuclei. Thalamic modulators are heterogeneous in regards to their origin, the neurotransmitter they use, and the effect on thalamic cells. Modulators also share some features, such as having small terminal boutons and activating metabotropic receptors on the cells they contact. I will review anatomical and physiological data on thalamic modulators with these goals: first, determine to what extent the evidence supports similar modulator functions across thalamic nuclei; and second, discuss the current evidence on modulation in the midline and intralaminar nuclei in relation to their role in executive function

Shared Responsibility of Highly Effective Co-teachers in Middle School Mathematics Classrooms

Currently, most students with disabilities (SWDs) receive a majority of their education in the general education classroom (U.S. Department of Education, 2019). This inclusive practice reflects educational and accountability requirements described in the Individuals with Disabilities Education Improvement Act (2004) and the Every Student Succeeds Act (2015). To address these requirements, schools seek service delivery models that support SWDs and close achievement gaps (Murawski & Goodwin, 2014). In this study, the researcher investigated the lived experiences of highly effective middle school teachers using co-teaching as a service delivery model to support SWDs in the general education classroom. The researcher used a phenomenological qualitative approach for this study. The research was conducted in a large urban district in the western United States. The researcher conducted face-to-face interviews with individual teachers with three pairs of co-teachers assigned to a co-teach model in a middle school mathematics classroom. The researcher was also able to observe one planning session between one pair of co-teachers. Using a spiral analysis procedure, three themes emerged from the interview and observation data as well as six subthemes. The three themes were (a) collaboration of lesson development, (b) student learning, and (c) parity. The researcher described the themes using thick, rich descriptions, provides a connection between research and the findings, and suggests recommendations for future research

There\u27s Only One You

https://stars.library.ucf.edu/diversefamilies/3122/thumbnail.jp

Central Thalamic Stimulation

Central thalamus regulates forebrain arousal, influencing activity in distributed neural networks that give rise to organized actions during alert, wakeful states. Central thalamus has been implicated in working memory by the effects of lesions and microinjected drugs in this part of the brain. Lesions and drugs that inhibit neural activity have been found to impair working memory. Drugs that increase activity have been found to enhance and impair memory depending on the dose tested. Electrical deep brain stimulation (DBS) similarly enhances working memory at low stimulating currents and impairs it at higher currents. These effects are time dependent. They were observed when DBS was applied during the memory delay (retention) or choice response (retrieval) but not earlier in trials during the sample (acquisition) phase. The effects of microinjected drugs and DBS are consistent with the Yerkes-Dodson law, which describes an inverted-U relationship between arousal and behavioral performance. Alternatively these results may reflect desensitization associated with higher levels of stimulation, spread of drugs or current to adjacent structures, or activation of less sensitive neurons or receptors at higher DBS currents or drug doses