Review Articles

Sensory systems encode and interpret patterns of contrast in sensory signals to provide an accurate representation of an animal's environment. Maler and colleagues here outline our current understanding of the principles of contrast coding in the electrosensory system and make comparisons with contrast coding in the visual system.

Cortico–basal ganglia circuits are involved in goal-directed and habitual actions. Jahanshahiet al. review evidence for the involvement of the cortico–basal ganglia network in goal-directed and habitual inhibition, and propose that some of the symptoms of basal ganglia disorders represent an imbalance between goal-directed and habitual action and inhibition.

Type 2 diabetes mellitus is associated with an increased risk of cognitive dysfunction and Alzheimer disease. In this Review, Biessels and Reagan discuss findings from human studies and animal models which suggest that hippocampal insulin resistance is one of the mechanisms underlying the links between these disorders.

Ageing leads to the gradual loss of brain function and is a key risk factor for most late-onset neurological disease. In this Review, Chow and Herrup explore how the loss of DNA integrity drives brain ageing and contributes to the pathogenesis of many seemingly unrelated conditions.

The brain is particularly sensitive to changes in cell number, which can acutely affect neural function. Here, Knoblich and colleagues describe the proliferation control mechanisms that exist inDrosophila melanogasterand mammals, and their regulation by developmental age and by metabolic and nutritional status.

Attention processes allow the selection of salient information over competing inputs. In this Review, Amso and Scerif propose a framework for visual attention development that incorporates its interactions with visual and memory systems and may guide the design of training programmes to alleviate attention disorders.

Impairment of social cognition is an important feature of schizophrenia. Green and colleagues review the social processes that are affected in people with this disorder and consider empathy — a complex social cognitive function that involves several of these processes — in such individuals.

Cannabinoid receptors and their endogenous ligands, the endocannabinoids, are widely expressed in the brain, particularly in regions that are implicated in mediating reward. In this Review, Parsons and Hurd explore the role of endocannabinoid signalling in natural and drug-induced reward, as well as in addiction.

Fragile X syndrome (FXS) results from the loss of the RNA-binding protein fragile X mental retardation protein (FMRP). Here, Klann and colleagues discuss the ways in which FMRP loss disrupts mRNA translation in the brain and the outcomes of genetic and pharmacological attempts to reset translational homeostasis in FXS model mice.

Memory storage is thought to be mediated by lasting physical changes, or engrams, in the brain. In this Review, Josselyn and colleagues discuss characteristics of the engram and describe the recent progress that has been made in identifying neurons involved in specific engrams.

Schizophrenia is characterized by various neurocognitive deficits, including impairments in auditory function. In this Review, Javitt and Sweet examine the behavioural, neurophysiological and structural evidence for auditory cortical dysfunction in this disorder and explore some of the possible underlying mechanisms.

Recent years have seen considerable interest in the genetics of autism spectrum disorder (ASD). In this Review, Thomas Bourgeron examines the genetic architecture of this disorder and how ASD-linked mutations might affect synaptic plasticity, before exploring the synaptic homeostasis hypothesis of ASD.

Various lines of evidence suggest that immune system dysregulation has a key role in autism spectrum disorder (ASD). Estes and McAllister review this evidence, covering genetic and maternal immune system-related risk factors, chronic immune system changes in individuals with ASD and in animal models, and potential pathophysiological mechanisms.

Local circuit GABAergic inhibitory interneurons regulate almost all aspects of cortical and hippocampal circuitry. In this Review, Overstreet-Wadiche and McBain discuss how neurogliaform cells are emerging as an inhibitory interneuron type with unique cellular and signalling properties that diverge from canonical roles for interneurons.

The health of the vertebrate brain is dependent on appropriate levels of cerebrospinal fluid (CSF), which is secreted by the choroid plexus (ChP). In this Review, Lehtinen and colleagues examine ChP structure and development and explore recently discovered functions of the ChP–CSF system.

Bidirectional signalling between nociceptors and immune cells protects the host from potential threats to homeostasis. In this Review, McMahon and colleagues discuss how, when such signalling becomes uncontrolled or dysfunctional, it can contribute to immune-mediated diseases and persistent pain states.

Exposure to one stressor can lead to altered responses to subsequent stressors, implying that the neural circuits that mediate stress responses undergo adaptive changes. Bains and colleagues review mechanisms of synaptic plasticity in the paraventricular nucleus of the hypothalamus that may contribute to such responses.

Placebo effects are positive effects on health that arise from the response of the brain to the contextual information that accompanies the delivery of a treatment. In this Review, Wager and Atlas examine the neural mechanisms that underlie such effects, focusing on placebo analgesia.

Recent methodological progress has greatly facilitated the determination of the connectivity and functional characterization of complex neural circuits. In this Review, Tovote, Fadok and Lüthi examine studies that have adopted circuit-based approaches to gain insight into how the brain governs fear and anxiety.

It is now emerging that the neuroinflammation that is associated with Alzheimer disease may have a key role in driving this disease. In this Review, Heppner, Ransohoff and Becher examine the contribution of the immune system to the pathogenesis of this disorder.