Dr. Iain Stitt
Data Scientist and Neuroscientist
Research
During my time as a neuroscientist, I was primarily interested in understanding how widely distributed cortical and subcortical brain regions talk to each other, and how this communication supports cognition and behavior. I have investigated signatures of large-scale communication in three different networks: thalamo-cortical networks, cortico-cortical networks, and cortical-tectal networks. One research topic that I become known for was understanding the relationship between in biophysical interactions in neural networks and brain state.
If you are interested in my scientific publications, please look here.
Thalamo-cortical networks
Whether it be the daydreaming student in their least favoured class, or the intently focused surgeon operating to save a patient’s life, our brains exhibit the ability to rapidly transition between states of varying engagement with the external world. In this study I wanted to investigate how such ongoing shifts in mental state affect the interaction between thalamus and cortex.
To answer this question, I recorded neural activity from higher-order cortical and thalamic structures while simultaneously tracking fluctuations in pupil diameter - a non-invasive indicator of arousal.
Remarkably, I found that shifts in pupil-linked arousal were linked to the self-organized rerouting of thalamo-cortical communication. This dynamic rerouting was achieved by switching the direction and carrier frequency of thalamo-cortical effective connectivity.
To my knowledge, this study represents the first evidence of the systematic reorganization of inter-areal functional interaction with pupil-linked arousal. This project was performed in the lab of Dr. Flavio Frohlich at the University of North Carolina at Chapel Hill (USA).
Cortico-cortical networks
Throughout the daily cycle we experience drastic transitions in our state of vigilance and behavior. For example, when we fall asleep at night we go from being conscious and interacting with our surroundings, to unconscious and (mostly) non-receptive to the external environment. Given that the dynamic interaction of widely distributed brain regions is proposed to be crucial for the emergence of consciousness, I decided to investigate how patterns of large-scale cortical functional connectivity are reorganized according to transitions in brain state across the sleep/wake cycle.
To delineate brain state, I developed a procedure to project time-varying spectral signatures of micro-electrocorticogram recordings into lower dimensional 'state-space'. I then evaluated how patterns of synchronization between distant brain regions are modulated as a function of state space. This approach revealed that large-scale interaction in the brain is systematically reorganized as animals traverse the sleep/wake cycle, with deepest states of unconsciousness (non-REM sleep) characterized by the fragmentation of cortical networks, while more lucid states (awake and REM sleep) were characterized by greater synchronization between brain regions.
This project was performed in collaboration with my good friend Jonas Hollensteiner (shared first author) in the lab of Prof. Andreas Engel in Hamburg, Germany.
Cortico-tectal networks
The superior colliculus represents a fascinating interface from a systems neuroscience perspective: it receives both direct inputs from the retina as well as top-down inputs from low and high order cortical regions. How does this connectivity profile influence the intrinsic dynamics of the superior colliculus? To answer this question I embarked on a technically challenging set of experiments where I recorded from all layers of the superior colliculus and cortex, while simultaneously recording micro-electrocorticographic signals from the entire poster cortex (see figure).
This approach revealed that cortico-tectal functional interaction spans several carrier frequencies. Interestingly, correlation of high frequency signals closely resembled direct anatomical connectivity, and were tightly related to correlated spiking activity between cortex and superior colliculus. Lower frequencies displayed different correlation maps, suggesting that interaction in these bands is mediated by (indirect) connections through other subcortical nuclei, such as the pulvinar.
This project was performed in the lab of Prof. Andreas Engel in Hamburg, Germany.
