Inhibitory inputs from thalamus promote resilient spiking in tail of striatum

Understanding how sensory information shapes striatal processing is central to explaining how animals learn, adapt, and initiate appropriate actions. In recent years, interest has expanded beyond the well-studied rostral striatum toward more caudal territories, such as the tail of the striatum (TS)—a region increasingly recognized for its role in sensory-guided learning and value assignment. The research group led by Laura M. Haetzel and colleagues investigates how thalamostriatal pathways support these functions, with a particular focus on projections arising from the medial geniculate body (MGB), the auditory thalamus.

Thalamic afferents are known to form glutamatergic synapses onto striatal medium spiny neurons (MSNs), but most functional studies have examined rostral domains. Far less is known about how thalamic signals modulate neuronal output in TS, despite the region’s emerging importance. The study addresses this gap by examining how MGB inputs regulate MSN activity within the TS. Using optogenetics-assisted circuit mapping and whole-cell recordings in ex vivo slices, the researchers demonstrate that activation of MGB terminals enhances MSN firing, but only under conditions of strong postsynaptic depolarization.

Beyond these excitatory connections, the researchers also uncover a sparse population of higher-order MGB GABAergic projection neurons that inhibit TS MSNs through a GABA(_B)-receptor-dependent mechanism. Together, these findings propose a new framework in which the MGB exerts state-dependent, bidirectional control over striatal output, shaping how sensory information is transformed into action-relevant signals.