A long-neglected layer of cells at the very bottom of the cerebral cortex may play a central role in how the brain directs and sustains attention, according to a new paper published in Neuron. In a Perspective article, Matthew Larkum from Humboldt University of Berlin, Tim Zolnik and Britta Eickholt from the Charité – Universitätsmedizin Berlin, and Zoltán Molnár from University of Oxford, propose that layer 6b, a thin band of neurons once thought to be merely a developmental remnant, acts as a powerful controller of attention-related brain activity. Layer 6b is the adult descendant of the subplate, a transient structure that plays a crucial role during early brain development. Although subplate neurons are essential for wiring the cortex in infancy, their surviving counterparts in the adult brain have largely been ignored. The new work argues that this assumption is no longer tenable and suggests that these neurons are ideally positioned to control some of the brain’s most important circuits—those involved in attention, arousal, and awareness.
A strategic position in the brain.
The review outline how layer 6b neurons are uniquely connected within the brain. Despite being relatively few, they send targeted projections to higher-order thalamic nuclei and to layer 5 pyramidal neurons, key components of cortico–thalamic feedback loops that are widely believed to underpin attention and conscious perception (Figure 1). Crucially, layer 6b neurons are also exceptionally sensitive to neuromodulators associated with arousal and motivation, including orexin, dopamine, neurotensin, acetylcholine and noradrenaline. Orexin is a master regulator of wakefulness and is known to be deficient in narcolepsy. By integrating these chemical signals with top-down input from higher cortical areas, the authors propose that layer 6b can rapidly and precisely switch attention-related circuits on or off, sustain them over time, and flexibly redirect them when attention shifts.
Read the full story on the Department of Physiology, Anatomy and Genetics website.