Research articles

It has been widely believed that a key function of sleep is to actively clear metabolites and toxins from the brain. Miao, Luo et al. show in mice that brain clearance is markedly reduced—not increased—during sleep and anesthesia.

Physiologically relevant stimulation of dopamine neurons does not function as a reward and does not endow cues with a reward representation. However, high-frequency stimulation is represented as a sensory-specific goal that motivates behavior.

Muller et al. show that some neurons in the cortex learn faster from better-than-expected outcomes compared to worse-than-expected ones; others do the converse, resulting in simultaneous optimism and pessimism, as predicted by distributional reinforcement learning.

In this study the authors show that in the mouse anterior thalamus, the activity of head-direction cells is selectively modulated by sensory stimuli and by the animal’s behavioral state.

The biological meaning of eye pupil size is a subject of intense research. This study shows that pupil fluctuations reveal information about hypothalamic orexin cells, which control pupil size via a noradrenaline neural circuit.

Using depth electrodes in human patients, scientists at the Mayo Clinic found that the map of the body in motor cortex extends deep into the central sulcus. Unexpectedly, the nonsomatotopic ‘Rolandic motor association’ (RMA) area interrupts this organization.

This study mapped the developmental trajectory of transmission speed in the human brain by using electrical pulses and intracranial recordings. The authors found that these pulses travel with increasing speeds up to at least the age of 30.

Oligodendrocyte precursor cells (OPCs) have functions beyond oligodendrogenesis. Here the authors show that OPCs can engulf thalamocortical presynapses in response to sensory experience in mice.

Fiber photometry can record brain dynamics, but the biological source of the signal remains unclear. The authors report that fiber photometry in striatum mainly reflects nonsomatic, and not somatic or spiking-related, changes in calcium.

The structural and functional development of the human cerebellum is not well known. The cerebellum shows a gradient of tissue properties across its lobules, each of which develops at a unique rate and closely follows changes in function across childhood.

Consumption of excessive high-fat diet (HFD) induces compulsive feeding. Here the authors show HFD-induced microglia activation in the anterior paraventricular nucleus of the thalamus plays a crucial role in promoting compulsive eating behavior.

fMRI reveals similar topography, selectivity and inter-connectedness of language brain areas across 45 languages. These properties may allow the language system to handle the shared features of languages, shaped by biological and cultural evolution.

The authors found that the expression of spatial maps in the hippocampus is modulated by the internal state of an animal. Thus, the brain’s code for spatial positions within an environment can transform even without changes to the external world.

Mazzitelli, Smyth and colleagues show that cerebrospinal fluid gains direct access to skull bone marrow niches via dura–skull channels, allowing for the CNS context-dependent regulation of immune supply to the meninges.

Oligodendrocyte precursor cells exist in abundance throughout the brain lifelong, with unclear functions. Xiao et al. show that, in zebrafish, these cells regulate the precise formation of retinal ganglion cell arbors and fine-tune visual processing.

Neely et al. investigated the regeneration of different oligodendrocytes after demyelination. They found that newly generated cells exhibit much more proficient remyelination than those that survive demyelination, with implications for MS.

This study shows that Aβ from transgenic host tissue is able to enter and deposit within wild-type grafts via microglia, thus identifying microglia as carriers of Aβ deposition into previously unaffected brain tissue.

The conventional view is that the cortex generates brain oscillations, while subcortical structures control global sleep–wake switching. This study shows that the cortex plays an important role in both global state control and sleep homeostasis.

Hippocampal ~8-Hz theta rhythmicity is enhanced in virtual reality, seen in the local field potential, pyramidal cells and interneurons. It is accompanied by the emergence of a novel ~4-Hz eta rhythm, seen in the local field potential and interneurons.

Eiselt et al. report conditions under which mice confuse thirst for hunger, similar to some human decisions that lead to over-eating. Evaluation of physiological need state requires consuming food or water and depends on the prefrontal cortex.