Stress, associative learning, and decision-making

Exposure to acute and chronic stress has significant effects on the basic mechanisms of associative learning and memory. Stress can both impair and enhance associative learning depending on type, intensity, and persistence of the stressor, the subject's sex, the context that the stress and behavior is experienced in, and the type of associative learning taking place. In some cases, stress can cause or exacerbate the maladaptive behavior that underlies numerous psychiatric conditions including anxiety disorders, obsessive-compulsive disorder, post-traumatic stress disorder, substance use disorder, and others. Therefore, it is critical to understand how the varied effects of stress, which may normally facilitate adaptive behavior, can also become maladaptive and even harmful. In this review, we highlight several findings of associative learning and decision-making processes that are affected by stress in both human and non-human subjects and how they are related to one another. An emerging theme from this work is that stress biases behavior towards less flexible strategies that may reflect a cautious insensitivity to changing contingencies. We consider how this inflexibility has been observed in different associative learning procedures and suggest that a goal for the field should be to clarify how factors such as sex and previous experience influence this inflexibility.

Neurotensin neurons in the extended amygdala control dietary choice and energy homeostasis

Obesity is a global pandemic that is causally linked to many life-threatening diseases. Apart from some rare genetic conditions, the biological drivers of overeating and reduced activity are unclear. Here, we show that neurotensin-expressing neurons in the mouse interstitial nucleus of the posterior limb of the anterior commissure (IPAC), a nucleus of the central extended amygdala, encode dietary preference for unhealthy energy-dense foods. Optogenetic activation of IPAC^Nts neurons promotes obesogenic behaviors, such as hedonic eating, and modulates food preference. Conversely, acute inhibition of IPAC^Nts neurons reduces feeding and decreases hedonic eating. Chronic inactivation of IPAC^Nts neurons recapitulates these effects, reduces preference for sweet, non-caloric tastants and, furthermore, enhances locomotion and energy expenditure; as a result, mice display long-term weight loss and improved metabolic health and are protected from obesity. Thus, the activity of a single neuronal population bidirectionally regulates energy homeostasis. Our findings could lead to new therapeutic strategies to prevent and treat obesity.

Sex-Specific Stress-Related Behavioral Phenotypes and Central Amygdala Dysfunction in a Mouse Model of 16p11.2 Microdeletion

Background

Substantial evidence indicates that a microdeletion on human chromosome 16p11.2 is linked to neurodevelopmental disorders, including autism spectrum disorder (ASD). Carriers of this deletion show divergent symptoms besides the core features of autism spectrum disorder, such as anxiety and emotional symptoms. The neural mechanisms underlying these symptoms are poorly understood.

Methods

We used mice heterozygous for a deletion allele of the genomic region corresponding to the human 16p11.2 microdeletion locus (i.e., 16p11.2 del/+ mice) and their sex-matched wild-type littermates for the study and examined their anxiety-related behaviors, auditory perception, and central amygdala circuit function using behavioral, circuit tracing, and electrophysiological techniques.

Results

Mice heterozygous for a deletion allele of the genomic region corresponding to the human 16p11.2 microdeletion locus (i.e., 16p11.2 del/+ mice) had sex-specific anxiety-related behavioral and neural circuit changes. Specifically, we found that female, but not male, 16p11.2 del/+ mice showed enhanced fear generalization-a hallmark of anxiety disorders-after auditory fear conditioning and displayed increased anxiety-like behaviors after physical restraint stress. Notably, such sex-specific behavioral changes were paralleled by an increase in activity in central amygdala neurons projecting to the globus pallidus in female, but not male, 16p11.2 del/+ mice.

Conclusions

Together, these results reveal female-specific anxiety phenotypes related to 16p11.2 microdeletion syndrome and a potential underlying neural circuit mechanism. Our study therefore identifies previously underappreciated sex-specific behavioral and neural changes in a genetic model of 16p11.2 microdeletion syndrome and highlights the importance of investigating female-specific aspects of this syndrome for targeted treatment strategies.

Giant hepatic hemangioma studied with intravenous total body arteriography technique. A case report

Hepatic hemangiomas are the most common benign tumors of the liver. They are usually single, small, and asymptomatic. However, giant hepatic hemangiomas have been reported in the past, usually detected as incidental findings. Radionuclide blood pool imaging studies are used to confirm the presence of a hemangioma. This report describes a case of a giant hepatic hemangioma detected using intravenous total-body arteriography, done as a part of radionuclide blood pool hemangioma study. This simple addition to the regular RBC blood pool hemangioma study helps to determine the size of the liver in the early arterial phase and shows obvious increased blood pool activity in the delayed phase. It is also useful in detecting lesions in other parts of the body when present.

Evaluation of Klippel-Trenaunay syndrome with radionuclide total body angiography. A case report

A 21-year-old Italian woman with extensive Klippel-Trenaunay syndrome (KTS) developed recurrent pulmonary embolism in spite of the insertion of a Greenfield filter in the inferior vena cava. Clinical and radiologic diagnostic tests failed to demonstrate the pathway of the emboli. Radionuclide venography and intravenous radionuclide total body arteriography were performed. These radionuclide procedures helped to evaluate the extent of KTS and to detect the route of the emboli. This is the first case of KTS studied with intravenous total body arteriography reported in the literature.

Obstruction of the iliac veins due to markedly distended urinary bladder demonstrated by radionuclide venography. A case report

An unusual case of obstruction of the iliac veins by a markedly distended urinary bladder (UB) is presented. Initial radionuclide venography (RNV) was positive, revealing obstruction of the iliac veins associated with marked dilatation of the UB. After the UB was emptied, RNV was negative.

Use of i.v. radionuclide total body arteriography to evaluate arterial bypass shunts--a new method--a review of several cases

Currently, Doppler ultrasound and contrast angiography are the main imaging procedures being used to evaluate arterial bypass shunts. IV radionuclide total body arteriography (TBA) is another useful imaging procedure for evaluation of bypass shunts. The authors reviewed 33 patients, 19 women and 14 men, ranging in age from forty-three to eighty-five, who had TBA done after arterial bypass surgery. Ten patients had multiple shunts and 5 had multiple follow-up studies. In total there were 80 shunts, including 43 femoropopliteal, 16 axillofemoral, 1 axillopopliteal, 13 crossover femorofemoral, and 7 aortofemoral shunts. Sixty-two of the 80 shunts were patent, 14 were occluded, and 4 had partial occlusion. The results were confirmed by Doppler studies, contrast angiograms, and/or surgical exploration without false positives or false negatives. Since the radiotracer used was 99mTc-labeled red blood cells, a MUGA study can also be performed immediately following TBA in the same injection. Twenty-eight patients had gated cardiac blood pool studies (MUGA) done; 16 had abnormal wall motion and diminished ventricular function. TBA requires only a single IV injection of radiotracer (less than 1 cc) in the upper limb. The imaging times for total body arterial and perfusion images are seventy seconds and five minutes respectively. Both total body arterial and perfusion images clearly demonstrated the entire course of shunts (single or multiple); underlying and coexisting arterial abnormalities, e g, occlusive disease (27 patients), or aneurysm (3 patients); and related perfusion changes in the extremities. TBA has unique features. It permits a complete, excellent visualization of the bypass graft without the hazard of contrast media injection. It is a simple and a virtually noninvasive procedure, particularly useful for preoperative workups and postoperative follow-ups.

Cutaneous fistula communicating with the hip in a patient with a painful total hip prosthesis. Demonstration by radionuclide arthrography

Radionuclide arthrography is becoming increasingly useful in the evaluation of femoral component loosening in patients with a painful total hip prosthesis. Additional potential advantages of radionuclide arthrography include detection of abnormal communications with the hip, such as bursae, abscess cavities, and fistulas. A case of cutaneous fistula communicating with the hip in a patient with loosening and infection of the femoral component of the total hip prosthesis that is clearly demonstrated by radionuclide arthrography is presented.

Intravenous radionuclide total body arteriography: a new technique

We have developed a technique using a blood pool agent Tc-99m labeled red blood cells and a detector head set moving at a high speed to obtain total body arterial and blood pool images with only a single intravenous injection. Previously with an intravenous radiotracer injection, only regional arterial images could be obtained. Now, with this simple, non-invasive technique, we can evaluate the major arterial system, organs, and soft tissues in the whole body, as well as cardiac function. On reviewing 500 cases, more than 90% of the first-pass arterial phase images clearly demonstrated the aorta, ilio-femoral arteries, and, to a lesser extent, the more distal arteries in the lower extremities. The second-pass blood pool images revealed the anatomical and morphological status of the solid organs, as well as perfusion changes in various organs and soft tissues.

IV radionuclide total-body arteriography: a new noninvasive whole-body screening procedure--a case report

Recently the authors introduced a new technique of intravenous (IV) radionuclide total-body arteriography. The major arterial system, multiple organs of the whole body, and cardiac function can be evaluated with one small IV injection in the arm. After analyzing more than 1000 cases, they have found that many pathologies can be detected and/or confirmed in this procedure. This new technique may be used as a general whole-body screening test for those patients at high risk for disease.

Successful removal of a severed transvenous pacemaker electrode

The ease and simplicity of the transvenous approach to permanent pacing continue to be among its greatest advantages. However in a small proportion of transvenously paced patients complications can occur. A rare complication is an incompletely removed pacing catheter with subsequent embolization to more central parts of the cardiovascular system. This communication reports the migration of a severed transvenous pacemaker electrode and its removal from the left iliac vein with a femoral-ventricular pigtail catheter.