Form and Function of Sleep Spindles across the Lifespan

Figure 1

Spindles generation within the CT-TRN-TC circuit. (a) Sleep spindles are generated through reciprocal interactions of the TRN (green) and TC (red) neurons. Spindles can be initiated by excitatory input from CT (blue) neurons, which also synchronize spindle oscillations across the thalamocortical network. Representative neural firing patterns (right) show the order and organization of firing for CT, TRN, and TC neurons, respectively (adapted from [9]). As TC neurons fire, they provide input to both cortical and TRN neurons, and these populations phase-lock their firing. As cortical, TRN, and TC neurons desynchronize their firing, the spindle oscillation wanes. (b) The CT-TRN-TC circuit may also generate local spindles following waking experience. For example, training on a motor task leads to increased sleep spindles over the contralateral motor cortex during subsequent sleep (left; adapted from [10]). There are several possible mechanisms by which changes to CT-TRN-TC circuitry during waking could cause subsequent local spindle increases (right). TC projections may show changes to dynamics (e.g., firing rate or bursting) based on prior waking experience (1). Experience may alter TRN excitability or bursting during subsequent sleep (2). CT feedback may be altered by experience to increase synchronization or amplification of spindles (3). Finally, intracortical plasticity could amplify spindles locally (4).

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