Dissertation
The human subthalamic nucleus inhibits neural representations of attentional engagement
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2023
DOI: 10.25820/etd.006853
Abstract
The subthalamic nucleus (STN) of the basal ganglia is key to the inhibitory control of movement (Jahanshahi et al., 2015). Accordingly, it is a primary target for the neurosurgical treatment of movement disorders like Parkinson’s Disease, where modulating the STN via deep-brain stimulation (DBS) can release excess inhibition of thalamo-cortical motor circuits (Benabid et al., 2009; Lofredi et al., 2021; Wessel et al., 2022). However, the STN is also anatomically connected to other thalamo-cortical circuits, including those underlying cognitive processes like attention (Haynes & Haber, 2013; Bingham et al., 2023). This suggests that the STN may also contribute to the inhibition of those processes. We here tested this hypothesis in humans. We used a novel, wireless outpatient method to record intracranial local field potentials from STN DBS implants (Gilron et al., 2021; Feldmann et al., 2022) during a visual attention task (Soh & Wessel, 2021). We also modulated STN via DBS. In both cases, we simultaneously recorded high-density EEG to extract the steady-state visual evoked potential (SSVEP), a neural measure of visual attentional engagement (Muller et al., 1998). Introducing unexpected, distracting sounds lead to a momentary reduction of this SSVEP. This suppression was preceded by sound-related γ-frequency (>60Hz) activity in STN, which scaled with each sound’s surprisal value. The STN activity statistically mediated the suppressive effect of surprisal on the SSVEP. Finally, modulating STN activity via DBS reduced the sound-related SSVEP-suppression. Together, these findings provide the first causal evidence that the human STN contributes to the inhibition of attention, a non-motor process. Beyond their support for a domain-general inhibitory role of the STN, these findings also suggest a mechanism underlying known cognitive side-effects of STN DBS (Parsons et al., 2006; Heo et al., 2008; Combs et al., 2015).
Details
- Title: Subtitle
- The human subthalamic nucleus inhibits neural representations of attentional engagement
- Creators
- Cheol Soh
- Contributors
- Jan R Wessel (Advisor)Cathleen Moore (Committee Member)Eliot Hazeltine (Committee Member)Kai Hwang (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Psychology
- Date degree season
- Autumn 2023
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.006853
- Number of pages
- viii, 59 pages
- Copyright
- Copyright 2023 Cheol Soh
- Language
- English
- Date submitted
- 11/28/2023
- Description illustrations
- illustrations, tables, graphs
- Description bibliographic
- Includes bibliographical references (pages 34-50).
- Public Abstract (ETD)
- A brain region called the subthalamic nucleus (STN) is a small structure situated deep in the human brain. The STN has been primarily shown to play a key role in rapidly suppressing motor processes. However, recent evidence suggests that the STN is capable of inhibiting even cognitive processes that are independent of motor processes, such as visual attention. To test this hypothesis, we recruited Parkinson’s patients and measured brain activity at the scalp that reflected sustained visual selective attention. We also simultaneously acquired direct recordings from the STN, hypothesized to modulate the suppression of sustained visual attention. We found that the neural representation of visual attention was transiently reduced as we introduced unexpected sounds, and the degree of this disruption could be explained by the STN activity. In the second experiment, we tested if this attentional interruption could be causally eliminated after stimulating the STN using DBS, which is a typical treatment for Parkinsonian symptoms like tremors. Indeed, we found that STN DBS reduced the degree of attentional interruption. Current findings provided causal evidence that the STN can non-selectively suppress visual attention. This expands the scope of processes that were traditionally thought to be suppressed by the STN beyond motor activities. Lastly, our findings provide an explanation of the neural mechanisms behind the side effects of STN DBS, like attentional impairment.
- Academic Unit
- Psychological and Brain Sciences
- Record Identifier
- 9984546943902771
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