Subthalamic Nucleus Stimulation Does Not Have Any Acute Effects on Verbal Fluency or on Speed of Word Generation in Parkinson’s Disease

Abstract

Background Deep brain stimulation of the subthalamic nucleus (STN-DBS) has been shown to be generally safe from a cognitive perspective, with consistent evidence that the major impact of STN-DBS in Parkinson's disease (PD) is on verbal fluency. Objective The aim of this study was first to identify the influence of acute manipulation of STN-DBS in PD on the number and time pattern of word generation on different verbal fluency (VF) tasks, phonemic, switching, and cued switching, and second to determine whether cueing improved VF and if cueing effects interacted with STN-DBS effects. Methods Parallel versions of these three verbal fluency tasks were completed by 31 patients with Parkinson's disease who had had bilateral DBS of the STN, twice, with DBS On and Off, with the order counterbalanced across patients. Results There was no effect of acute STN-DBS on the total number of words generated during verbal fluency. As expected, the number of words generated significantly declined over the six 10-second intervals of the verbal fluency tasks, but this time pattern of word generation was not altered by STN-DBS. External cueing significantly increased the number of words generated relative to an uncued switching verbal fluency task, but the cueing effect on VF was not altered by STN-DBS. Conclusion In conclusion, (i) acute STN-DBS manipulation did not alter either verbal fluency performance or the time pattern of word generation and (ii) external cueing significantly improved verbal fluency performance both with STN-DBS On and Off.

Deep brain stimulation effects on verbal fluency dissociated by target and active contact location

“…Moreover, we studied patients in their optimal medication and stimulation state and did not include a postoperative off stimulation state to dissociate potential surgical lesion from stimulation effects. Two recent studies that investigated the stimulation effect on verbal fluency, by comparing ON‐OFF stimulation performance, did not find a DBS effect 58,59 . Similarly, a review on DBS‐induced cognitive decline 14 suggested that verbal fluency appears to be largely a surgical implantation effect.…”

“…Two recent studies that investigated the stimulation effect on verbal fluency, by comparing ON-OFF stimulation performance, did not find a DBS effect. 58,59 Similarly, a review on DBS-induced cognitive decline 14 suggested that verbal fluency appears to be largely a surgical implantation effect. Others have pointed out the impact of stimulation parameters and contact location as contributing factors, especially in terms of individual variation in fluency effects.…”