Identifying the midline thalamus in humans in vivo.

The midline thalamus is critical for flexible cognition, memory, and stress regulation in humans and its dysfunction is associated with several neurological and psychiatric disorders, including Alzheimer's disease, schizophrenia, and depression. Despite the pervasive role of the midline thalamus in cognition and disease, there is a limited understanding of its function in humans, likely due to the absence of a rigorous noninvasive neuroimaging methodology to identify its location. Here, we introduce a new method for identifying the midline thalamus in vivo using probabilistic tractography and k-means clustering with diffusion weighted imaging data. This approach clusters thalamic voxels based on data-driven cortical and subcortical connectivity profiles and then segments the midline thalamus according to anatomical connectivity tracer studies in rodents and macaques. Results from two different diffusion weighted imaging sets, including adult data (22-35 years) from the Human Connectome Project (n = 127) and adolescent data (9-14 years) collected at Florida International University (n = 34) showed that this approach reliably classifies midline thalamic clusters. As expected, these clusters were most evident along the dorsal/ventral extent of the third ventricle and were primarily connected to the agranular medial prefrontal cortex (e.g., anterior cingulate cortex), nucleus accumbens, and medial temporal lobe regions. The midline thalamus was then bisected based on a human brain atlas into a dorsal midline thalamic cluster (paraventricular and paratenial nuclei) and a ventral midline thalamic cluster (rhomboid and reuniens nuclei). This anatomical connectivity-based identification of the midline thalamus offers the opportunity for necessary investigation of this region in vivo in the human brain and how it relates to cognitive functions in humans, and to psychiatric and neurological disorders.

Dual medial prefrontal cortex and hippocampus projecting neurons in the paraventricular nucleus of the thalamus.

The paraventricular nucleus (PVT) of the midline thalamus is a critical higher-order cortico-thalamo-cortical integration site that plays a critical role in various behaviors including reward seeking, cue saliency, and emotional memory. Anatomical studies have shown that PVT projects to both medial prefrontal cortex (mPFC) and hippocampus (HC). However, dual mPFC-HC projecting neurons which could serve a role in synchronizing mPFC and HC activity during PVT-dependent behaviors, have not been explored. Here we used a dual retrograde adenoassociated virus (AAV) tracing approach to characterize the location and proportion of different projection populations that send collaterals to mPFC and/or ventral hippocampus (vHC) in rats. Additionally, we examined the distribution of calcium binding proteins calretinin (CR) and calbindin (CB) with respect to these projection populations in PVT. We found that PVT contains separate populations of cells that project to mPFC, vHC, and those that innervate both regions. Interestingly, dual mPFC-HC projecting cells expressed neither CR nor CB. Topographically, CB+ and CR+ containing cells clustered around dual projecting neurons in PVT. These results are consistent with the features of dual mPFC-vHC projecting cells in the nucleus reuniens (RE) and suggestive of a functional mPFC-PVT-vHC system that may support mPFC-vHC interactions in PVT-dependent behaviors.

Dual projecting cells linking thalamic and cortical communication routes between the medial prefrontal cortex and hippocampus.

The interactions between the medial prefrontal cortex (mPFC) and the hippocampus (HC) are critical for memory and decision making and have been specifically implicated in several neurological disorders including schizophrenia, epilepsy, frontotemporal dementia, and Alzheimer's disease. The ventral midline thalamus (vmThal), and lateral entorhinal cortex and perirhinal cortex (LEC/PER) constitute major communication pathways that facilitate mPFC-HC interactions in memory. Although vmThal and LEC/PER circuits have been delineated separately we sought to determine whether these two regions share cell-specific inputs that could influence both routes simultaneously. To do this we used a dual fluorescent retrograde tracing approach using cholera toxin subunit-B (CTB-488 and CTB-594) with injections targeting vmThal and the LEC/PER in rats. Retrograde cell body labeling was examined in key regions of interest within the mPFC-HC system including: (1) mPFC, specifically anterior cingulate cortex (ACC), dorsal and ventral prelimbic cortex (dPL, vPL), and infralimbic cortex (IL); (2) medial and lateral septum (MS, LS); (3) subiculum (Sub) along the dorsal-ventral and proximal-distal axes; and (4) LEC and medial entorhinal cortex (MEC). Results showed that dual vmThal-LEC/PER-projecting cell populations are found in MS, vSub, and the shallow layers II/III of LEC and MEC. We did not find any dual projecting cells in mPFC or in the cornu ammonis (CA) subfields of the HC. Thus, mPFC and HC activity is sent to vmThal and LEC/PER via non-overlapping projection cell populations. Importantly, the dual projecting cell populations in MS, vSub, and EC are in a unique position to simultaneously influence both cortical and thalamic mPFC-HC pathways critical to memory. SIGNIFICANCE STATEMENT: The interactions between mPFC and HC are critical for learning and memory, and dysfunction within this circuit is implicated in various neurodegenerative and psychiatric diseases. mPFC-HC interactions are mediated through multiple communication pathways including a thalamic hub through the vmThal and a cortical hub through lateral entorhinal cortex and perirhinal cortex. Our data highlight newly identified dual projecting cell populations in the septum, Sub, and EC of the rat brain. These dual projecting cells may have the ability to modify the information flow within the mPFC-HC circuit through synchronous activity, and thus offer new cell-specific circuit targets for basic and translational studies in memory.

Calretinin and calbindin architecture of the midline thalamus associated with prefrontal-hippocampal circuitry.

The midline thalamus bidirectionally connects the medial prefrontal cortex (mPFC) and hippocampus (HC) creating a unique cortico-thalamo-cortical circuit fundamental to memory and executive function. While the anatomical connectivity of midline thalamus has been thoroughly investigated, little is known about its cellular organization within each nucleus. Here we used immunohistological techniques to examine cellular distributions in the midline thalamus based on the calcium binding proteins parvalbumin (PV), calretinin (CR), and calbindin (CB). We also examined these calcium binding proteins in a population of reuniens cells known to project to both mPFC and HC using a dual fluorescence retrograde adenoassociated virus-based tracing approach. These dual reuniens mPFC-HC projecting cells, in particular, are thought to be important for synchronizing mPFC and HC activity. First, we confirmed the absence of PV+ neurons in the midline thalamus. Second, we found a common pattern of CR+ and CB+ cells throughout midline thalamus with CR+ cells running along the nearby third ventricle (3V) and penetrating the midline. CB+ cells were consistently more lateral and toward the middle of the dorsal-ventral extent of the midline thalamus. Notably, single-labeled CR+ and CB+ zones were partially overlapping and included dual-labeled CR+ /CB+ cells. Within RE, we also observed a CR and CB subzone specific diversity. Interestingly, dual mPFC-HC projecting neurons in RE expressed none of the calcium binding proteins examined, but were contained in nests of CR+ and CB+ cells. Overall, the midline thalamus was well organized into CR+ and CB+ rich zones distributed throughout the region, with dual mPFC-HC projecting cells in reuniens representing a unique cell population. These results provide a cytoarchitectural organization in the midline thalamus based on calcium binding protein expression, and set the stage for future cell-type specific interrogations of the functional role of these different cell populations in mPFC-HC interactions.

A randomized comparison of long acting methylphenidate and cognitive behavioral therapy in the treatment of binge eating disorder.

Cognitive behavioral therapy (CBT) is a well-established treatment for binge eating disorder (BED); however, this treatment is underutilized, highlighting the need for additional treatment alternatives. Dopamine neurotransmission has been associated with dysregulated eating, and pharmaceutical agents targeting the dopamine system are associated with decreased binge eating and weight. The primary objective of the current investigation was to evaluate the efficacy of psychostimulant medication versus current best practices in the treatment of BED symptoms, in a randomized trial of methylphenidate versus CBT for BED. The secondary objective was to evaluate the ability of impulsivity to predict treatment outcomes. Female outpatients with BED were randomized to receive methylphenidate (n = 22) or CBT (n = 27) for 12 weeks. The primary outcome was objective binge episode frequency; secondary outcomes included subjective binge episode frequency, body mass index (BMI), BED symptoms, and quality of life. Results showed that both treatments had a significant impact on primary and secondary outcomes. Methylphenidate and CBT were associated with decreases in subjective and objective binge episodes; methylphenidate was associated with greater decreases in BMI. Two impulsivity traits predicted clinical outcomes. Results provide preliminary support for the therapeutic benefit of methylphenidate in BED treatment, and prognostic utility of impulsivity in this context.

A multicenter study of the effect of dietary supplementation with fish oil omega-3 fatty acids on carprofen dosage in dogs with osteoarthritis.

OBJECTIVE: To determine the effects of feeding a diet supplemented with fish oil omega-3 fatty acids on carprofen dosage in dogs with osteoarthritis. DESIGN: Randomized, controlled, multisite clinical trial. ANIMALS: 131 client-owned dogs with stable chronic osteoarthritis examined at 33 privately owned veterinary hospitals in the United States. PROCEDURES: In all dogs, the dosage of carprofen was standardized over a 3-week period to approximately 4.4 mg/kg/d (2 mg/lb/d), PO. Dogs were then randomly assigned to receive a food supplemented with fish oil omega-3 fatty acids or a control food with low omega-3 fatty acid content, and 3, 6, 9, and 12 weeks later, investigators made decisions regarding increasing or decreasing the carprofen dosage on the basis of investigator assessments of 5 clinical signs and owner assessments of 15 signs. RESULTS: Linear regression analysis indicated that over the 12-week study period, carprofen dosage decreased significantly faster among dogs fed the supplemented diet than among dogs fed the control diet. The distribution of changes in carprofen dosage for dogs in the control group was significantly different from the distribution of changes in carprofen dosage for dogs in the test group. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that in dogs with chronic osteoarthritis receiving carprofen because of signs of pain, feeding a diet supplemented with fish oil omega-3 fatty acids may allow for a reduction in carprofen dosage.

Multicenter veterinary practice assessment of the effects of omega-3 fatty acids on osteoarthritis in dogs.

OBJECTIVE: To assess the effect of food containing high concentrations of fish oil omega-3 fatty acids and a low omega-6-omega-3 fatty acid ratio on clinical signs of osteoarthritis in dogs. DESIGN: Randomized, double-blinded, controlled clinical trial. ANIMALS: 127 client-owned dogs with osteoarthritis in 1 or more joints from 18 privately owned veterinary clinics. PROCEDURES: Dogs were randomly assigned to be fed for 6 months with a typical commercial food or a test food containing a 31-fold increase in total omega-3 fatty acid content and a 34-fold decrease in omega-6-omega-3 ratio, compared with the control food. Dog owners completed a questionnaire about their dog's arthritic condition, and investigators performed a physical examination and collected samples for a CBC and serum biochemical analyses (including measurement of fatty acids concentration) at the onset of the study and at 6, 12, and 24 weeks afterward. RESULTS: Dogs fed the test food had a significantly higher serum concentration of total omega-3 fatty acids and a significantly lower serum concentration of arachidonic acid at 6, 12, and 24 weeks. According to owners, dogs fed the test food had a significantly improved ability to rise from a resting position and play at 6 weeks and improved ability to walk at 12 and 24 weeks, compared with control dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Ingestion of the test food raised blood concentrations of omega-3 fatty acids and appeared to improve the arthritic condition in pet dogs with osteoarthritis.

Evaluation of the effects of dietary supplementation with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis.

OBJECTIVE: To evaluate the effects of a food supplemented with fish oil omega-3 fatty acids on weight bearing in dogs with osteoarthritis. DESIGN: Randomized, double-blinded, controlled clinical trial. ANIMALS: 38 client-owned dogs with osteoarthritis examined at 2 university veterinary clinics. PROCEDURES: Dogs were randomly assigned to receive a typical commercial food (n = 16) or a test food (22) containing 3.5% fish oil omega-3 fatty acids. On day 0 (before the trial began) and days 45 and 90 after the trial began, investigators conducted orthopedic evaluations and force-plate analyses of the most severely affected limb of each dog, and owners completed questionnaires to characterize their dogs' arthritis signs. RESULTS: The change in mean peak vertical force between days 90 and 0 was significant for the test-food group (5.6%) but not for the control-food group (0.4%). Improvement in peak vertical force values was evident in 82% of the dogs in the test-food group, compared with 38% of the dogs in the control-food group. In addition, according to investigators' subjective evaluations, dogs fed the test food had significant improvements in lameness and weight bearing on day 90, compared with measurements obtained on day 0. CONCLUSIONS AND CLINICAL RELEVANCE: At least in the short term, dietary supplementation with fish oil omega-3 fatty acids resulted in an improvement in weight bearing in dogs with osteoarthritis.