Articles in 2013

Here the authors report evidence for the neural correlates of confidence in the primate pulvinar, a visual thalamic nucleus. Data from electrophysiological recordings, functional silencing and theoretical modeling indicate that pulvinar activity encodes a subject's certainty of visual categorization and contributes to perceptual confidence, which potentially underlies visual awareness.

In this study, the authors show that Dscam, a gene that has been implicated in Down syndrome, is targeted by the translation suppressor and Fragile X–linked protein FMRP. Loss of FMRP or overexpression of Dscam in Drosophila led to synaptic targeting errors and an impairment in perception of mechanical stimuli.

Making informed decisions requires taking into account how reliably choices produce expected outcomes. This study shows that primate anterodorsal septal neurons encode an uncertainty signal sensitive to reward size but do not carry information about the uncertainty of punishments.

Early-life stress, acting through corticotrophin-releasing hormone (CRH) and its receptor CRHR1, can have long-lasting effects on animals' behavior. Nectin-3 is a cell adhesion molecule whose heterodimeric interaction with presynaptic nectin-1 organizes the postsynaptic afadin–actin–N-cadherin complex to shape synaptic structure and function. Here, the authors show that structural synaptic adaptation and cognitive dysfunction in adulthood following early-life stress are dependent on CRH signaling acting through Nectin-3.

In this study, the authors show that MGE-derived interneuron progenitors, when engrafted into the adult hippocampus, can migrate long distances and functionally integrate into the host tissue. In addition, if these cells are engrafted into the brain after the initiation of epilepsy, seizure frequency and behavioral deficits are reduced.

Temporal and spatial integration of synaptic inputs onto dendrites can display linear, sublinear and supralinear motifs in vitro. A study now examines this issue in vivo in mouse binocular visual cortex. It shows that dendritic integration of binocular information is sublinear, leading to a divisive form of gain control that linearizes the output of binocular neurons and enhances orientation selectivity.

Long-term exposure to glucocorticoids following chronic stress is detrimental to cognitive processes including learning and memory. Even so, short term glucocorticoid surges can facilitate cognition. Here the authors show that the circadian oscillation in circulating glucocorticoids is important for motor skill learning–induced dendritic spine remodeling. They also show that circadian glucocorticoid-mediated synaptic modification acts through non-transcriptional mechanism involving cytoskeleton remodeling and correlates with long-term memory retention.

In this study, the authors identify the ER-localized protein Meigo as a modulator of dendritic and axonal targeting of olfactory neurons. They find that Meigo is essential for maintaining protein levels and N-glycosylation of Ephrin in the ER, thereby regulating its function in axonal and dendritic refinement.

In response to the movement of its visual world, Drosophila is capable of optomotor response in head and body turning, as well as a visual fixation response. This study shows that blocking the visual pathway activity responsible for optokinetic response in flies does not affect the visual fixation response, suggesting two distinct pathways for processing each set of information. By doing so, the authors also devised a neural and behavioral hierarchy in fly visual system where fixation behavior and the neurons mediating fixation response are upstream of optokinetic response as performed by lobula plate neurons.

In this study, the authors use time-lapse in vivo two-photon imaging to elucidate the dynamics of NG2⁺ gial cells in the cortex. They find that proliferation and migration of these cells is intimately linked to the loss of neighboring cells to cell death or differentiation.

Prevailing models have suggested that grid cell firing in the entorhinal cortex for spatial navigation relies on theta rhythmic inputs from head direction cells. Here, the authors show how head direction cells can skip theta cycles in a regular and organized manner in which two head direction cells will alternate theta skipping in opposing cycles. This so-called theta skipping is dependent on the input from the septum, and these results propose a possible mechanism of spatial computation.

In primary visual cortex (V1), adaptation controls the responsiveness of individual neurons and shifts their visual selectivity. Here the authors examine adaptation at the population level. They conclude that adaptation in V1 acts as a mechanism of homeostasis, enforcing a tendency towards equality and independence in neural activity across the population.

The authors use functional magnetic resonance imaging to measure how the semantic representation changes when searching for different object categories in natural movies. They find tuning shifts that expand the representation of the attended category and of semantically related, but unattended, categories, and compress the representation of categories semantically dissimilar to the target.

How are goal-directed actions directed and motivated? This paper presents behavioral and electrophysiological data in rats to dissect the differential role of the ventral striatum (VS) and dorsomedial striatum (DMS) in action-selection and motivation. The work suggests that the DMS is important in encoding the net expected return, sensitizing the rats to the local average reward value in a block of trials.

Wamsteeker Cusulin and colleagues report that stress-induced glucocorticoid release can trigger metaplasticity at GABAergic synapses on neuroendocrine neurons of the hypothalamus in rodents. Following stress, these GABAergic synapses gain the ability to undergo long-term depression in vitro, which involves amplification of mGluR signaling and retrograde suppression of synaptic transmission via persistent activation of presynaptic μ-opioid receptors. This form of plasticity may serve as a mechanism for behavioral stress adaptation.

Relative amounts of amyloid-β peptides of different length are altered in the brains of Alzheimer's disease patients. Here the authors show that neuronal patterns differentially regulate the production of amyloid-β isoforms by modifying the molecular conformation of presenilin-1, the catalytic subunit of γ-secretase that cleaves amyloid precursor protein to release amyloid-β.

Touch information is conveyed by a receptorless whisker hair to the follicle mechanoreceptors that provide input to the brain. Here the authors show that information processing goes on even at the level of the whisker, which suggests a role for pre-neuronal morphological computation in active vibrissal touch.

Inoue and colleagues find that stress triggers a noradrenaline-dependent metaplastic change at GABAergic synapses onto paraventricular neurons of the hypothalamus in rodents. This metaplasticity depends on mGluR1, enables these synapses to undergo long-term potentiation during afferent bursts stimulation in vitro and possibly contributes to the neuroendocrine sensitization to stress.

Oligodendrocytes form myelin sheaths and provide metabolic support to axons. Using in vivo genetic fate tracing in a mouse model of amyotrophic lateral sclerosis (ALS), this study shows that there is extensive degeneration of oligodendrocytes near motor neurons prior to behavioral manifestation of disease. Although oligodendrocytes were regenerated from resident progenitors, they failed to mature and restore myelin, a feature also observed in brain and spinal cord tissue from ALS patients. Selective deletion of ALS-linked mutant SOD1 from the oligodendrocyte lineage greatly delayed disease onset, suggesting that this mutant protein impairs their ability to support motor neurons.

Wang et al. find that deletion of FIP200, a protein essential for autophagy, leads to deficits in the maintenance and differentiation of postnatal neural stem cells (NSC). These effects are rescued by an antioxidant treatment, suggesting that FIP200-mediated autophagy regulates neurogenesis by controlling the oxidative state of NSC.