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How do subcortical and cortical brain structures interact in complex cognition? Our focus is on the role of the mediodorsal thalamus interacting with the frontal lobes during learning, memory and decision-making, via interconnected neural networks.

My group focuses on how the brain processes information as part of distributed neural circuits. Our particular interest is with the medial thalamus. We use behavioural and cognitive neuroscience methods to understand how the medial thalamus (in particular the mediodorsal thalamus) and interconnected cortical regions contribute to learning, memory and decision-making as well as other cognitive processes (e.g. executive functioning).

At present our focus is on the mediodorsal thalamus (it is the largest subdivision of the medial thalamus) and its interactions with the prefrontal cortex. The functions of the mediodorsal thalamus are still not yet well defined and its role in many neurological disorders and psychiatric diseases remains speculative.

We have recently provided the first causal evidence of the importance of interactions between the mediodorsal thalamus and prefrontal cortex during learning complex information on a trial-by-trial basis and adaptive decision-making in primates (Browning, Chakraborty, Mitchell, 2015, Cerebral Cortex).

Other recent findings show the critical role of the mediodorsal thalamus in updating reward-guided learning in uncertain or changing environments (Chakraborty, Kolling, Walton, Mitchell, 2016, eLife). We also have further causal evidence to demonstrate that the integrity of the mediodorsal thalamus is also critical in supporting the prefrontal cortex during tasks involving cognitive flexibility (Chakraborty, Mason, Mitchell, Bell, Buckley, Mitchell, in prep). 

We also have a particular interest in the interactions between the retrosplenial cortex and the anterior thalamic nuclei (also located within the medial thalamus) with our recent publication demonstrating the critical role for the retrosplenial cortex in retention of previously acquired information (Buckley and Mitchell, 2016, Cerebral Cortex).

We use a multidisciplinary approach to advancing fundamental knowledge about the interactions between nuclei of the medial thalamus and their cortical targets in cognition, combining cognitive and behavioural neuroscience techniques including electrophysiology, neuroimaging, neurocognitive testing, disruption to selective brain targets in animals, neuroanatomy, immunohistochemistry and immuno-electron microscopy. We also assess cognitive and behavioural changes in patients with medial thalamic strokes using neuropsychological testing and neuroimaging. 

Previously the lab has shown that the mediodorsal thalamus provides a more critical role in supporting new learning (anterograde amnesia) than in retention of information learned prior to brain injury (retrograde amnesia; Mitchell and Gaffan, 2008, J Neurosci). In contrast, selective targeted brain disruption to cortical regions (e.g. entorhinal cortex and retrosplenial cortex) produce more impairments in the retention of information compared with new learning. These findings demonstrate that learning and memory (and presumably other cognitive processes as well) are not unitary functions but instead depend on many subtly different processes that are supported by independent but interacting and partially overlapping neural networks in the brain (Mitchell and Gaffan, 2008, J Neurosci; Mitchell et al. 2008, J Neurosci; Buckley and Mitchell, 2016, Cerebral Cortex; Mitchell, 2015, Neurosci BioBeh Rev).

We also provided the first causal evidence in macaque monkeys of the critical role of the mediodorsal thalamus in adaptive decision-making (Mitchell et al. 2007, J Neurosci).

The team

Scientific meetings

  • Understanding local and global circuit mechanisms for cognition in primates - July 2016

    Understanding the circuit mechanisms of cognitive functions remain important issues in neuroscience. In particular, primate studies play an important role, providing both functional and anatomical models for the cognitive circuits in the human brain. This symposium provides recent findings on the functions of both thalamo-cortical global interactions and local interactions in the cortical microcircuits of primates, to further understand their computational principles important for cognition.

Related research themes