（１）

The thalamus is the major input to the cortex and interactions between these two structures are critical for cognition. While the it is often thought of as a simple relay carrying information to the cortex or between cortical regions, recent anatomical and functional data suggest that such an oversimplified model is unlikely to capture the involvement of the thalamus in many cognitive functions.  This is particularly true in the case of “higher-order” thalamic nuclei such as the mediodorsal (MD) and Lateral Posterior (LP).  Unlike the more extensively studied sensory thalamic nuclei, these higher-order nuclei are primarily connected to cortical circuits and receive little peripheral sensory input. Previous work has suggested that one of these nuclei, the MD helps to sustain attentional rules in its cortical counterpart, the prefrontal cortex (PFC) by selectively stabilizing task-relevant cortical networks. These results suggest that thalamic input may play a key role in short-term maintenance of information, a function that is essential for the ability to make inferences based on dynamically changing sensory stimuli. To determine whether this function is a general feature of higher-order thalamocortical networks, we have begun investigating interactions between posterior parietal cortex (PPC) and its thalamic counterpart, the LP. The PPC is a key player in sensory decision-making and recent evidence suggests that one of its roles is to influence processing of current inputs based on sensory history.  Using a novel sensory decision-making task, we found that the PPC maintains sensory history and that this function requires the LP. We also found that, similar to MD, LP activation enhanced connectivity in the PPC suggesting that it may play an analogous role in stabilizing cortical representations. Overall, these findings identify a potentially general circuit feature in the mammalian brain, thalamic control of functional cortical connectivity, and suggest that it is essential for diverse cognitive abilities that rely on short term maintenance of information.

（２）

In constantly changing environments, animals must adapt their behaviors based on informative sensory stimuli. Because the meaning of a given sensory input can vary depending on the situation, the brain must flexibly map each stimulus to its appropriate behavioral output depending on internal goals. The prefrontal cortex (PFC) plays a central role in implementing such transformations but how the PFC supports adaptive processing of information across multiple tasks without interference remains unclear. An important step in understanding flexible computations in the PFC is to examine how outputs (decoders) of this circuit are flexibly incorporated into its internal, task-specific networks. To investigate this, we employed well-controlled behavioral tasks that require cue to task-rule transformation in the PFC both to identify populations carrying relevant output information and to examine task-related activity in this population. More specifically, by applying a rule dependent cross-modal sensory selection task we sought to identify the PFC outputs that controlled sensory processing. Our findings demonstrated that PFC neurons projecting to different territories of the tail of striatum acted to "decode" rule information, providing outputs that controlled selection among competing sensory modalities by suppressing distracting input. These outputs were anatomically fixed, placing a fundamental constraint on the internal dynamics of the PFC. Overall, our results identify a key output of the PFC responsible for the control of sensory processing and introduce important principles governing how this circuit can remodel its internal network depending on the goal.