Volume 20 Issue 4, April 2017

Addictive substances hijack the reward system partly via synaptic plasticity onto dopamine neurons. Cadherins may contribute to cocaine-evoked adaptations, supporting the notion that drug addiction is a synaptic disease.

Hippocampal place cells are traditionally thought to represent locations where animals currently are or predict where they are headed. However, new results reveal that place cells also represent distant places that are actively avoided.

The rate of development of the brain connectome distinguishes adolescents with and without psychiatric symptoms. Those with symptoms exhibit delayed development of connectome distinctiveness as compared to healthy adolescents.

Reinforcement learning (RL) is the behavioral process of learning to associate rewards with actions or objects. Conceptual and theoretical accounts of RL have focused on the striatum. However, recent data shows that the amygdala also plays an important role in RL.

This study on neurodevelopment of functional networks reveals a network tuning process that transforms the human connectome into a stable, individualized wiring pattern. Delay in this tuning was associated with disordered mental health, revealing the detrimental paths that brain plasticity can take during adolescence, when initial symptoms of mental illness occur.

Shi et al. performed a systematic clonal analysis and revealed an intricate ontogenetic logic of structural development and functional organization of the mammalian thalamus. Notably, neurons in cognitive versus sensory or motor nuclei as well as in first-order versus high-order sensory or motor nuclei across different modalities exhibit distinct progenitor origin and spatial configuration.

The authors show that activation of GluK2-containing kainate receptors on hippocampal neurons, by either agonist application or high-frequency synaptic stimulation, leads to a new form of NMDA-receptor-independent LTP. Induction of this form of plasticity requires the metabotropic action of postsynaptic kainate receptors, which triggers spine growth and potentiation of AMPA-receptor-mediated transmission.

Drugs of abuse alter the strength of synaptic connections within the mesocorticolimbic dopamine system. The current study demonstrates that this is dependent on the recruitment of cadherin to the synaptic membrane. Increased cadherin at dopaminergic synapses impairs cocaine-induced synaptic plasticity, resulting in a reduction in cocaine preference.

The authors use a variety of techniques to isolate and manipulate retinal inputs to direction-selective neurons in the mouse superior colliculus. They show that these cells inherit their selectivity from the retina by combining inputs from similarly tuned ganglion cells, which are further amplified in the colliculus without altering selectivity.

Entorhinal cortex transfers multimodal information to hippocampus CA1 neurons via indirect and direct pathways. The authors show that excitatory projections from lateral entorhinal cortex selectively target a subpopulation of morphologically complex, calbindin-expressing pyramidal cells in CA1, forming a distinct direct circuit that is required for olfactory associative learning.

How hippocampal place cells participate in fear memory retrieval is unknown. Wu et al. show that, when rats retrieve prior shock experience prompting them to avoid a shock zone, precise place cell activity patterns encoding paths from animals’ current locations to the shock zone are replayed in association with high-frequency ripple oscillations.

A long-standing idea in modern neuroscience is that the brain computes inferences about the outside world rather than passively observing its environment. The authors record from midbrain dopamine neurons during tasks with different reward contingencies and show that responses are consistent with a learning rule that harnesses hidden-state inference.

Using single-neuron recordings in the human brain during a working-memory task, the authors show both stimulus-specific and nonspecific types of persistent activity in neurons of the medial frontal and medial temporal lobes. Persistent activity in hippocampus and amygdala was predictive of memory content and displayed dynamic attractor patterns.

Yuen et al. developed a cloud-based database with 5,205 whole genomes from families with autism spectrum disorder (ASD). They identified 18 new candidate ASD-risk genes and approximately 100 risk genes and copy-number loci, which account for 11% of the cases. They also found that individuals bearing mutations in ASD-risk genes had lower adaptive ability.

The authors use fiber-based fabrication to create flexible biocompatible probes with integrated optical, electrical and microfluidic capabilities. Functionality is demonstrated by characterizing the temporal dynamics of opsin expression following viral delivery, long-term tracking of individual neuron action potentials and modulation of neural circuits in the context of mouse behavior.

The authors built a simple optical module that generates axially extended Bessel foci, optimized for in vivo brain imaging. Easily incorporated into existing two-photon fluorescence microscopes, this module allowed 30-Hz volumetric functional imaging of sparsely labeled brains at synaptic resolution in a variety of model organisms in vivo.