Maintenance of persistent activity in a frontal thalamocortical loop

Persistent neural activity maintains information that connects past and future events. Models of persistent activity often invoke reverberations within local cortical circuits, but long-range circuits could also contribute. Neurons in the mouse anterior lateral motor cortex (ALM) have been shown to have selective persistent activity that instructs future actions. The ALM is connected bidirectionally with parts of the thalamus, including the ventral medial and ventral anterior–lateral nuclei. We recorded spikes from the ALM and thalamus during tactile discrimination with a delayed directional response. Here we show that, similar to ALM neurons, thalamic neurons exhibited selective persistent delay activity that predicted movement direction. Unilateral photoinhibition of delay activity in the ALM or thalamus produced contralesional neglect. Photoinhibition of the thalamus caused a short-latency and near-complete collapse of ALM activity. Similarly, photoinhibition of the ALM diminished thalamic activity. Our results show that the thalamus is a circuit hub in motor preparation and suggest that persistent activity requires reciprocal excitation across multiple brain areas. Thalamic neurons show selective persistent activity that predicts movement direction, and their photoinhibition decreases activity in the anterior lateral motor cortex, and vice versa, suggesting that persistent activity requires reciprocal excitation in a thalamocortical loop. Sustained neuron excitement aids motor planning Persistent neural activity is a hallmark of multiple brain regions, and it may represent a means of maintaining information that bridges past and future events. Neurons in mouse anterior lateral motor cortex (ALM) show persistent activity that is relevant for upcoming actions. Karel Svoboda and colleagues now show that, in mice, neurons in parts of the thalamus connected to the ALM also show persistent delay activity that predicted their direction of movement. They find that each area is necessary for sustained activity in the other, supporting a model in which persistent activity related to motor planning is maintained by recurrent excitation across multiple brain areas. Elsewhere in this issue, Michael Halassa and colleagues report further on the functional diversity of the thalamus, finding evidence that it can maintain rule representations and amplify local connectivity to guide attention, but does so without relaying categorical information.