This issue of Nature Reviews Neuroscience features articles on olfactory perception, the neural code, psychedelic drugs and the influence of socioeconomic status (SES) on development.

In a Review article on page 628, Gottfried highlights principles that underlie central mechanisms of odour object perception. He reviews data showing that the piriform cortex is the site for the identification, categorization and discrimination of olfactory objects.

Reliable propagation of spiking activity in the brain is vital for the encoding, decoding and processing of information. On page 615, Kumar and colleagues review theoretical studies that have described asynchronous and synchronous propagation of spiking activity as two non-overlapping propagation modes. The authors propose a conceptual framework that considers both modes to be extremes of a continuum and offer experimental strategies to test this framework.

In a Perspective article on page 642, Vollenweider and Kometer discuss findings that psychedelic drugs can aid the treatment of depression and anxiety, and review data indicating that psychedelic drugs might achieve this by affecting glutamate and serotonin circuits. The authors argue that, despite the controversial nature of these drugs, more research into their potential as therapeutics for the treatment of mood and affective disorders is warranted.

How does SES during childhood influence neural development? In a Science and Society article on page 651, Hackman and colleagues describe how prenatal factors, parent–child interactions and cognitive stimulation vary with SES and contribute to behavioural and cognitive development. They call for a review of the programmes and policies that aim to reduce SES-related disparities in mental health and academic achievement between children.