Articles in 2015

Using fMRI multi-voxel pattern decoding, human superior IPS, but not occipital cortex, was found to closely track behavioral measures of information storage in visual short-term memory (VSTM) across distractor presence and predictability. This suggests that superior IPS, and not occipital cortex, has a central role in VSTM storage in the human brain.

Synaptic adhesion molecules are known to regulate synapse development, but growing evidence indicates that they also regulate synaptic function and plasticity. The authors report a novel synaptic adhesion molecule, IgSF11, that regulates excitatory synaptic transmission and plasticity through its dual interaction with the postsynaptic scaffold PSD-95 and AMPA receptors.

Via exome sequencing, the authors identified mutations in the NONO protein, a member of the DBHS family, as a likely cause of severe intellectual disability. Using animal and cell models, they found that nearly one-third of NONO-regulated transcripts were synaptosomal and that NONO depletion directly affected inhibitory synaptic structure.

Generalizing from past events to novel situations is common in animals. To have an adaptive value, this ability requires flexible control, especially in fearful situations. The authors demonstrate that fear generalization can be broken down to neural mechanisms involved separately in the detection of threat and its uncertainty.

Chronic neuropathic pain is associated with K⁺ channel downregulation in primary sensory neurons. The authors show that G9a, a histone-modifying enzyme, is required for transcriptional repression of K⁺ channel–associated gene families caused by nerve injury. G9a in primary sensory neurons is a key epigenetic regulator involved in acute-to-chronic pain transition.

To learn, the brain must be able to tell when it has made a mistake. A new study by Ohmae and Medina reveals the neural algorithm responsible for encoding error signals during cerebellar learning. A replica of this algorithm was previously found in dopamine neurons, suggesting the same elemental mechanism.

Proprioception, the sense of body and limb position, begins in nerve cells called proprioceptors that are activated by muscle or joint stretch. The molecular mechanism of mechanotransduction in mammalian proprioceptors is unknown. The authors show that the mechanically activated cation channel Piezo2 is the principal mechanotransducer in murine proprioceptors.

Orientation selectivity is a key property of neurons in the primary visual cortex. Using genetic silencing of cortical neurons throughout development, this study shows that initial formation of orientation selectivity is independent of neuronal activity. The initial selectivity is subsequently modified and this later process depends on spontaneous neuronal activity.

Optogenetic release of dopamine from midbrain inputs to the hippocampus produces a powerful bidirectional control over hippocampal information flow to CA1 pyramidal neurons that depends on the pattern of stimulation. In this manner, a switch in the state of dopaminergic activity may serve to select specific events for memory storage.

Experience-dependent synaptic modifications are one of the fundamental mechanisms of learning and memory, yet they are difficult to measure in vivo. Here the authors introduce a network model–based method that infers synaptic plasticity rules from the analysis of the statistics of neuronal responses to novel versus familiar stimuli.

Hippocampal place cells are active offline in ‘replay’ sequences reflecting speeded-up depictions of behavioral trajectories, suggesting a model of memory. The authors show that encoding of replay sequences requires behavioral experience and the activation of molecular mechanisms of synaptic plasticity, while retrieval does not.

By optogenetically silencing thalamus, the authors show that visual cortex does not sustain a response without thalamus for more than a few tens of milliseconds. This rapid cortical activity decay predicts the temporal dynamics of sensory activity transmission between thalamus and cortex in awake animals, whereas under anesthesia, the fidelity of thalamo-cortical connection is dominated by the effect of synaptic depression.

Stroke is the leading cause of adult disability. This study shows that the secreted factor GDF10 is a signal for the formation of new brain connections that lead to recovery after stroke and can be manipulated to enhance recovery and movement control in this disease.

PSD-95 is one of the most abundant proteins at synapses and underlies synapse development and function. Hruska and colleagues show that the synaptic localization and turnover of PSD-95 relies on a direct interaction with the trans-synaptic organizer ephrin-B3, which is negatively regulated by neuronal activity through MAPK-dependent phosphorylation of ephrin-B3.

Increased signal-to-noise in neural representations of sensory stimuli is thought to underlie the perceptual benefits of attention. Manipulating reward contingencies across two locations dissociates visual cortical activity from attentional behavior. These data argue that attention works by selecting and filtering the relevant and irrelevant information represented in visual cortex.

This study shows that every individual has a unique pattern of functional connections between brain regions. This functional connectivity profile acts as a ‘fingerprint’ that can accurately identify the individual from a large group. Furthermore, an individual's connectivity profile can predict his or her level of fluid intelligence.

Sleeping mammalian brains show high coherence of slow-wave activity. In mouse models of Alzheimer's disease, which have abnormal levels of amyloid-β, amyloid plaques and associated memory deficits, these waves are massively impaired. This impairment is related to the previously demonstrated neuronal hyperactivity. Pharmacological manipulations that reduce hyperactivity result in the reinstatement of slow-wave coherence and in memory improvement.

The basal forebrain (BF) is important for sleep-wake control. In this study, the authors performed cell type–specific recording and manipulation of four genetically defined BF cell types in freely moving mice and mapped their synaptic connections in slices, providing a BF circuit diagram for sleep-wake control.

The human ability to choose relies considerably on frontoparietal association cortex. Constructing unified perception from inconclusive sensory input also requires selection among alternatives. Combining fMRI with a novel visual stimulus, Brascamp and colleagues find evidence against frontoparietal involvement in such perceptual selection, instead suggesting choice capability in the visual system itself.

Contextual modulation is ubiquitous in sensory processing. This study shows that, in visual cortex, spatial contextual modulation for natural inputs is not well described by existing models. Instead, it can be explained by inference about statistical structure in images, with modulation evident only when images contain spatial redundancies.