Evidence suggests that scalp-recorded occipital alpha-band (8–13 Hz) oscillations reflect phasic information transfer in thalamocortical neurons projecting from lateral geniculate nucleus to visual ...cortex 1–5. In animals, the phase of ongoing alpha oscillations has been shown to modulate stimulus discrimination and neuronal spiking 6. Human research has shown that alpha phase predicts visual perception of near-threshold stimuli 7–11 and subsequent neural activity 12–14 and that the frequency of these oscillations predicts reaction times 15, as well as the maximum temporal interval necessary for perceived simultaneity 16. These phasic effects have led to the hypothesis that conscious perception occurs in discrete temporal windows, clocked by the frequency of alpha oscillations 17–21. Under this hypothesis, variation in the frequency of occipital alpha oscillations should predict variation in the temporal resolution of visual perception. Specifically, when two stimuli fall within the same alpha cycle, they may be perceived as a single stimulus, resulting in perception with lower temporal resolution when alpha frequency is lower. We tested this by assessing the relationship between two-flash fusion thresholds (a measure of the temporal resolution of visual perception) and the frequency of eyes-closed and task-related alpha rhythms. We found, both between and within subjects, that faster alpha frequencies predicted more accurate flash discrimination, providing novel evidence linking alpha frequency to the temporal resolution of perception.
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•Individuals with higher alpha frequencies have vision with finer temporal resolution•Eyes-closed and prestimulus peak alpha frequency both show this relationship•Within an individual, spontaneous fluctuations in alpha frequency predict perception•Alpha oscillations may dictate the resolution of conscious visual updating
Samaha and Postle demonstrate that individuals’ temporal resolution of visual perception, as measured by two-flash fusion thresholds, can be predicted by the speed of their occipital alpha rhythm. Both within and between subjects, higher alpha frequencies correspond with a finer-grained resolution of visual processing.
For more than 50 years, psychologists and neuroscientists have recognized the importance of a working memory to coordinate processing when multiple goals are active and to guide behavior with ...information that is not present in the immediate environment. In recent years, psychological theory and cognitive neuroscience data have converged on the idea that information is encoded into working memory by allocating attention to internal representations, whether semantic long-term memory (e.g., letters, digits, words), sensory, or motoric. Thus, information-based multivariate analyses of human functional MRI data typically find evidence for the temporary representation of stimuli in regions that also process this information in nonworking memory contexts. The prefrontal cortex (PFC), on the other hand, exerts control over behavior by biasing the salience of mnemonic representations and adjudicating among competing, context-dependent rules. The "control of the controller" emerges from a complex interplay between PFC and striatal circuits and ascending dopaminergic neuromodulatory signals.
Highlights • Diverse animal models of depression and anxiety have impaired neurogenesis. • Neurogenesis is consistently boosted by antidepressants in animal models when animals are stressed. • ...Ablation of neurogenesis in animal models impairs cognitive functions relevant to depression, but only a minority of studies find that ablation causes depression or anxiety. • Recent human neuroimaging and postmortem studies are consistent with the neurogenic theory, but they are indirect. • A novel drug developed based on the neurogenic theory is promising in animal models.
The extent and biological impact of RNA cytosine methylation are poorly understood, in part owing to limitations of current techniques for determining the targets of RNA methyltransferases. Here we ...describe 5-azacytidine-mediated RNA immunoprecipitation (Aza-IP), a technique that exploits the covalent bond formed between an RNA methyltransferase and the cytidine analog 5-azacytidine to recover RNA targets by immunoprecipitation. Targets are subsequently identified by high-throughput sequencing. When applied in a human cell line to the RNA methyltransferases DNMT2 and NSUN2, Aza-IP enabled >200-fold enrichment of tRNAs that are known targets of the enzymes. In addition, it revealed many tRNA and noncoding RNA targets not previously associated with NSUN2. Notably, we observed a high frequency of C→G transversions at the cytosine residues targeted by both enzymes, allowing identification of the specific methylated cytosine(s) in target RNAs. Given the mechanistic similarity of RNA cytosine methyltransferases, Aza-IP may be generally applicable for target identification.
The regulation of gene transcription involves a dynamic balance between packaging regulatory sequences into chromatin and allowing transcriptional regulators access to these sequences. Access is ...restricted by the nucleosomes, but these can be repositioned or ejected by enzymes known as nucleosome remodellers. In addition, the DNA sequence can impart stiffness or curvature to the DNA, thereby affecting the position of nucleosomes on the DNA, influencing particular promoter 'architectures'. Recent genome-wide studies in yeast suggest that constitutive and regulated genes have architectures that differ in terms of nucleosome position, turnover, remodelling requirements and transcriptional noise.
The physical nature of the bacterial cytoplasm is poorly understood even though it determines cytoplasmic dynamics and hence cellular physiology and behavior. Through single-particle tracking of ...protein filaments, plasmids, storage granules, and foreign particles of different sizes, we find that the bacterial cytoplasm displays properties that are characteristic of glass-forming liquids and changes from liquid-like to solid-like in a component size-dependent fashion. As a result, the motion of cytoplasmic components becomes disproportionally constrained with increasing size. Remarkably, cellular metabolism fluidizes the cytoplasm, allowing larger components to escape their local environment and explore larger regions of the cytoplasm. Consequently, cytoplasmic fluidity and dynamics dramatically change as cells shift between metabolically active and dormant states in response to fluctuating environments. Our findings provide insight into bacterial dormancy and have broad implications to our understanding of bacterial physiology, as the glassy behavior of the cytoplasm impacts all intracellular processes involving large components.
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•The motion of large cytosolic components is drastically reduced upon metabolic arrest•Dynamics and apparent fluidity of the cytosol depend on metabolism and particle size•The bacterial cytoplasm displays properties characteristic of glass-forming liquids.
Tracking of cytoplasmic particles in bacteria demonstrates that the mobility of large cytoplasmic constituents depends on the metabolic activity of the cell and that glass-like properties of the cytosol result in caged-like behavior of large components.
The packaging of chromosomal DNA by nucleosomes condenses and organizes the genome, but occludes many regulatory DNA elements. However, this constraint also allows nucleosomes and other chromatin ...components to actively participate in the regulation of transcription, chromosome segregation, DNA replication, and DNA repair. To enable dynamic access to packaged DNA and to tailor nucleosome composition in chromosomal regions, cells have evolved a set of specialized chromatin remodeling complexes (remodelers). Remodelers use the energy of ATP hydrolysis to move, destabilize, eject, or restructure nucleosomes. Here, we address many aspects of remodeler biology: their targeting, mechanism, regulation, shared and unique properties, and specialization for particular biological processes. We also address roles for remodelers in development, cancer, and human syndromes.
Cells utilize diverse ATP-dependent nucleosome-remodelling complexes to carry out histone sliding, ejection or the incorporation of histone variants, suggesting that different mechanisms of action ...are used by the various chromatin-remodelling complex subfamilies. However, all chromatin-remodelling complex subfamilies contain an ATPase-translocase 'motor' that translocates DNA from a common location within the nucleosome. In this Review, we discuss (and illustrate with animations) an alternative, unifying mechanism of chromatin remodelling, which is based on the regulation of DNA translocation. We propose the 'hourglass' model of remodeller function, in which each remodeller subfamily utilizes diverse specialized proteins and protein domains to assist in nucleosome targeting or to differentially detect nucleosome epitopes. These modules converge to regulate a common DNA translocation mechanism, to inform the conserved ATPase 'motor' on whether and how to apply DNA translocation, which together achieve the various outcomes of chromatin remodelling: nucleosome assembly, chromatin access and nucleosome editing.
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