Distinct In Vivo Electrophysiological Profiles of Mediodorsal Thalamus Subdivisions

The mediodorsal nucleus of the thalamus (MD) is crucial for complex cognitive functions, and its dysfunction is associated with various neurological and psychiatric disorders. This nucleus is subdivided into three distinct regions - central, medial, and lateral (MDc, MDm, and MDl) - which differ in their anatomical connections, molecular makeup, and electrophysiological properties.

To investigate this further, researchers conducted single-neuron electrophysiological recordings in behaving adult mice. The findings unveiled significant disparities in the extracellular waveforms, spiking activity, and burst firing patterns among the MD subdivisions.

The central MD subdivision (MDc) neurons exhibited notably higher waveform amplitudes, elevated spontaneous firing rates, and increased burst firing compared to their medial (MDm) and lateral (MDl) counterparts. Importantly, these electrophysiological features were sufficient to accurately classify neurons into their respective anatomical subdivisions.

When subjected to hierarchical clustering analysis, the MDc neurons emerged as distinctly different from the MDm and MDl neurons, with a closer resemblance to non-MD thalamic nuclei.

Taken together, these observations underscore the presence of unique in vivo electrophysiological profiles for each of the MD subdivisions. These distinct profiles may have significant implications for understanding the role of the MD thalamus in health and disease, and could potentially pave the way for targeted therapeutic interventions.