Madelyn Hjort, PhD

This is an image of Dr. Madelyn Hjort, A blonde caucasian woman wearing a button up shirt

I am a neuroscientist that studies how the brain represents cognitive flexibility, which is how we learn to change behavior. My work links computational flexibility models and large scale neural recordings to inform targeted neuromodulation to promote flexible behavior.

I completed my doctoral work in Neuroscience at the University of Washington with Dr. Garret Stuber. Together, we described how medial prefrontal cortex and the ventral tegmental area work together to drive contingency degradation during flexible behavior.

I am currently a postdoctoral fellow at the University of Minnesota with Dr. Timothy Ebner. Together, we are characterizing how Purkinje cells across the cerebellum represent and contribute to processing of cognitive variables, including flexibility.

This is a schematic describing Dr. Hjort's work, using quantitative flexibility models and large-scale neural recordings to inform targeted optogenetics to investigate the circuits that drive flexible behavior

High level takeaways from my work are that learning takes time, and that it can take multiple errors before behavior starts to change.

Selected Work

A pseudocolored image (magma) of pyramidal neurons in the medial prefrontal cortex

Prefrontal to ventral tegmental area dynamics drive contingency degradation

DOI: Coming soon!

Read it now at: rdcu.be/fhfN4

We establish that some medial prefrontal cortex neurons, and those that project to the ventral tegmental area in particular, causally drive contingency degradation behavior. This provides a quantitative, mechanistic explanation for how certain prefrontal circuits permit flexibility to selectively stop learned behaviors though core subcortical reward systems.

An image of the striatum and a schematic showing the microprism visualization preparation

Microprisms enable enhanced throughput and resolution for longitudinal tracking of neuronal ensembles in deep brain structures

DOI: 10.1117/1.nph.11.3.033407

We detail a technique to track and image the activity of thousands of neurons over multiple days and weeks.

Pseudocolored heatmap images showing an increase in PFC cell activity after learning, and comparable activity across cue sets

A stable, distributed code for cue value in mouse cortex during reward learning

DOI: 10.7554/eLife.84604.3

We describe how prefrontal cortex develops value associations between cues and rewards, and quantify that this representation is stable over days, cue sets, and recording techniques.

Selected Work

Contact me at mmhjort@umn.edu