Summary: Deep brain stimulation (DBS) of the subthalamic nucleus, a widely used treatment for Parkinson’s disease, reliably improves motor symptoms such as tremor and rigidity. New research from the University of Iowa shows that the same intervention can also alter how the brain redirects attention, revealing a likely neural basis for some cognitive and behavioral side effects reported by patients.
In a controlled study, researchers compared attention shifts in Parkinson’s patients with their DBS devices turned on versus turned off. While DBS relieved motor impairment, it reduced patients’ ability to disengage from visual focus when presented with an unexpected auditory distraction. These findings implicate the subthalamic nucleus not only in motor control but also in the inhibition and reallocation of attention.
Key Facts:
- DBS of the subthalamic nucleus is effective for improving motor symptoms in Parkinson’s disease but can influence cognitive functions related to attention and impulse control.
- The study measured attentional shifts using auditory distractions and electrophysiological markers; patients with active DBS were less able to redirect visual attention toward unexpected sounds.
- Evidence points to the subthalamic nucleus as a hub that contributes to inhibitory control across motor and non-motor domains, helping explain some cognitive side effects of STN-DBS.
Source: University of Iowa
Researchers at the University of Iowa linked the subthalamic nucleus to the brain’s ability to redirect attention during distractions. The work sheds light on cognitive and behavioral changes that can follow deep brain stimulation treatment for Parkinson’s disease.
The subthalamic nucleus (STN) is a small but crucial node in the basal ganglia circuitry that regulates movement. In Parkinson’s disease, excessive inhibitory influence from the STN is thought to contribute to motor symptoms such as tremor and slowed movement. Deep brain stimulation—an implanted electrode that delivers continuous, rhythmic electrical pulses—reduces that excessive inhibition, often producing dramatic improvements in motor function.
Although DBS is often described as transformative—“people come in with Parkinson’s, surgeons turn the electrode on, and their tremor goes away,” says Jan Wessel, associate professor of Psychological and Brain Sciences and Neurology at Iowa—some patients report problems with attention, impulsivity, and risky behavior after implantation. These reports prompted Wessel and his team to test whether the STN contributes directly to the suppression and redirection of attention.
The researchers ran two complementary experiments. In one, they recorded intracranial local field potentials (LFPs) from STN implants in an outpatient setting while simultaneously measuring high-density scalp EEG. Participants focused on a visual task while occasional, unpredictable chirping sounds were presented to distract them. The steady-state visual evoked potential (SSVEP) served as a neural measure of visual attention: a drop in SSVEP amplitude indicates that attention has been diverted.
The intracranial recordings revealed that transient gamma-band activity in the STN preceded sound-related reductions in the SSVEP, and statistical modeling showed that STN activity mediated the suppressive effect of distraction on visual attention. In a second experiment, the team causally tested this relationship by comparing performance and SSVEP responses with DBS turned on versus off. When DBS was inactive, patients’ visual attention shifted away from the screen in response to sounds, as expected. When DBS was active, however, patients failed to divert their visual attention in response to the chirps.
“We found they no longer can break or suppress their focus of attention in the same way,” Wessel explains. The data indicate that DBS alters the STN’s normal role in transiently inhibiting ongoing attention, which helps explain why some patients display attentional deficits or increased impulsivity after treatment.
Importantly, the study does not call for abandoning DBS for Parkinson’s disease. Wessel emphasizes the clear motor benefits of stimulation while noting that different STN subregions may modulate motor and attentional systems separately. The goal of ongoing research is to refine stimulation strategies so clinicians can preserve motor improvements while minimizing cognitive side effects.
The study, “The human subthalamic nucleus transiently inhibits active attentional processes,” was published online March 4 in the journal Brain. The first author is Cheol Soh (Department of Psychological and Brain Sciences, University of Iowa). Other contributing authors include Mario Hervault, Nathan H. Chalkley, Cathleen M. Moore, Jeremy Greenlee, Andrea Rohl, Qiang Zhang, and Ergun Uc.
Funding: The research was funded by the National Institutes of Health and the National Science Foundation through a CAREER award to Jan Wessel.
About this neuroscience research news
Author: Richard Lewis
Source: University of Iowa
Contact: Richard Lewis – University of Iowa
Image: The image is credited to Neuroscience News
Abstract (condensed)
This research demonstrates that the human STN contributes to transient inhibition of attention, in addition to its established role in motor control. Using outpatient LFP recordings alongside scalp EEG, the team showed that sound-related STN activity precedes and mediates distraction-induced reductions in visual attentional engagement (SSVEP). Modulating the STN with DBS reduced these attentional interruptions, providing causal evidence that STN-DBS can alter non-motor inhibitory processes. The findings support a domain-general inhibitory function of the STN and suggest a neural mechanism for some cognitive side effects observed following STN-DBS therapy.