eLife digest | An inhibitory corticostriatal pathway

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An inhibitory corticostriatal pathway

eLife digest

Affiliation details

University of Texas at San Antonio, United States

The striatum is located beneath the cerebral cortex, where it contributes to processes including learning and movement. The Spanish anatomist Ramon y Cajal, working in the early 20th century, was the first to observe individual neurons extending from the cortex to the striatum. Cajal published drawings of these neurons in his now celebrated anatomical papers, but knew little about their properties.

In the 1980s, advances in techniques for labeling individual cells made it possible to study these neurons in detail. The results suggested that the pathways are exclusively excitatory: that is, the cortical neurons always increase the activity of their partners in the striatum. However, this result made it difficult to explain why electrically stimulating the cortex can sometimes reduce or inhibit the activity of the striatum. To reconcile these facts, most people assumed that inhibition must occur when excitatory cortical neurons activate networks of inhibitory cells within the striatum itself.

Rock et al. now challenge this view by providing anatomical and physiological evidence for the existence of long-range inhibitory pathways from the cortex to the striatum in the mouse brain. These inhibitory neurons project from the auditory and motor regions of the cortex, and contain a substance called somatostatin. These neurons form connections with a specific type of striatal neuron called medium spiny neurons, which in turn project to other brain regions outside the striatum. The inhibitory cortical neurons can alter the activity of the medium spiny neurons, and can therefore directly control the output of the striatum.

The discovery that the striatum receives both excitatory and inhibitory inputs from cortex suggests that the timing and relative strength of these inputs can affect the activity of the striatum. Future experiments should examine whether this is a general mechanism by which sensory stimuli can influence the processes controlled by the striatum, such as movement.

DOI: http://dx.doi.org/10.7554/eLife.15890.002