Highlights • During the normal waking state, the brain is in a constant state of internal exploration through the formation and dissolution of resting-state functional networks. • Based on large-scale computer models of the brain, the best fit to observed data comes when the networks are at the ‘edge of instability’. • Such a position is a distinct advantage for the efficiency and speed of network mobilization for perception and action. • We provide theoretical and empirical questions to better link resting-state networks to cognitive architectures.
Highlights • How proteinopathies damage brain networks is a key issue in neurodegenerative disease. • Here, we outline a solution based on the concept of ‘molecular nexopathies’. • The concept is founded on specific interactions of network and protein properties. • This new paradigm has far-reaching biological and clinical implications.
A basic feature of intelligent systems such as the cerebral cortex is the ability to freely associate aspects of perceived experience with an internal representation of the world and make predictions about the future. Here, a hypothesis is presented that the extraordinary performance of the cortex derives from an associative mechanism built in at the cellular level to the basic cortical neuronal unit: the pyramidal cell. The mechanism is robustly triggered by coincident input to opposite poles of the neuron, is exquisitely matched to the large- and fine-scale architecture of the cortex, and is tightly controlled by local microcircuits of inhibitory neurons targeting subcellular compartments. This article explores the experimental evidence and the implications for how the cortex operates.
The hallmarks of cancer described by Hanahan and Weinberg are properties that cancer cells must possess for successful transformation. It is believed that each of these hallmarks is independently driven. Although elongation of telomeres is thought to be the prime function of reactivated telomerase reverse transcriptase, this activity does not account for all its effects, such as increasing cell proliferation, resistance to apoptosis, and invasion. Recent studies suggest that the telomerase subunit telomerase reverse transcriptase (TERT) has novel molecular functions including transcriptional regulation and metabolic reprogramming. We summarize these functions and discuss how they could directly regulate the various hallmarks of cancer. Finally, we suggest that therapeutics targeting noncanonical telomerase functions may work better than those that target its role in telomere extension.
Conditioned place preference (CPP) is a learned behavior shown in many vertebrates, including humans. CPP occurs when a subject comes to prefer one place more than others because the preferred location has been paired previously with rewarding events. The CPP paradigm is widely used to explore the reinforcing effects of natural and pharmacological stimuli, including drugs of addiction. There is a general assumption that an acquired place preference is based on classical conditioning derived ‘incentive motivation’. However, this may be an oversimplification of the multiple learning processes involved. We argue that although CPP may appear as an incentive-driven behavior related to secondary reinforcers, it may also be a result of operant conditioning of behavior prevailing at the conditioning site, as well as a result of conditioned treatment effects. Here, we outline alternative explanations for an observed CPP, which may fundamentally affect the interpretation of results with this paradigm in its use as a screening tool for rewarding properties of treatments.
Drug repositioning is an innovation stream of pharmaceutical development that offers advantages for drug developers along with safer medicines for patients. Several drugs have been successfully repositioned to a new indication, with the most prominent of them being viagra and thalidomide, which have generated historically high revenues. In line with these developments, most of the recent articles and reviews on repositioning are focused on success stories, leaving behind the challenges that repositioned compounds have on the way to the clinic. Here, I analyze repositioning as a business opportunity for pharmaceutical companies, weighing both challenges and opportunities of repositioning. In addition, I suggest extended profiling as a lower-risk cost-effective repositioning model for pharmaceutical companies and elucidate the novel collaborative business opportunities that help to realize repositioning of shelved and marketed compounds.
DNA methylation in the form of 5-methylcytosine (5mC) is a key epigenetic regulator in mammals, and the dynamic balance between methylation and demethylation impacts various processes from development to disease. The recent discovery of the enzymatic generation and removal of the oxidized derivatives of 5mC, namely 5-hydroxymethylcysotine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) in mammalian cells has led to a paradigm shift in our understanding of the demethylation process. Interestingly, emerging evidence indicates that these DNA demethylation intermediates are dynamic and could themselves carry regulatory functions. Here, we discuss 5hmC, 5fC, and 5caC as new epigenetic DNA modifications that could have distinct regulatory functions in conjunction with potential protein partners.
Early-life stress lastingly affects adult cognition and increases vulnerability to psychopathology, but the underlying mechanisms remain elusive. In this Opinion article, we propose that early nutritional input together with stress hormones and sensory stimuli from the mother during the perinatal period act synergistically to program the adult brain, possibly via epigenetic mechanisms. We hypothesize that stress during gestation or lactation affects the intake of macro- and micronutrients, including dietary methyl donors, and/or impairs the dam's metabolism, thereby altering nutrient composition and intake by the offspring. In turn, this may persistently modulate gene expression via epigenetic programming, thus altering hippocampal structure and cognition. Understanding how the combination of stress, nutrition, and epigenetics shapes the adult brain is essential for effective therapies.
Antidepressant treatments enhance plasticity and increase neurogenesis in the adult brain, but it has been unclear how these effects influence mood. We propose that, like environmental enrichment and exercise, antidepressant treatments enhance adaptability by increasing structural variability within the nervous system at many levels, from proliferating precursors to immature synaptic contacts. Conversely, sensory deprivation and chronic stress reduce this structural variability. Activity-dependent competition within the mood-related circuits, guided by rehabilitation, then selects for the survival and stabilization of those structures that best represent the internal or external milieu. Increased variability together with competition-mediated selection facilitates normal function, such as pattern separation within the dentate gyrus and other mood-related circuits, thereby enhancing adaptability toward novel experiences.
Highlights • Circadian dysfunction is a growing concern in our society and interventions are needed. • Scheduled light exposure, meals, and exercise may strengthen circadian function. • Melatonin is among the best-studied circadian modulators available. • Promising new drugs may come from re-purposing known agents. • New high-throughput screens are identifying novel compounds.