Interleaved Propofol-Ketamine Maintains DBS Physiology and Hemodynamic Stability: A Double-Blind Randomized Controlled Trial.

BACKGROUND: The gold standard anesthesia for deep brain stimulation (DBS) surgery is the "awake" approach, using local anesthesia alone. Although it offers high-quality microelectrode recordings and therapeutic-window assessment, it potentially causes patients extreme stress and might result in suboptimal surgical outcomes. General anesthesia or deep sedation is an alternative, but may reduce physiological testing reliability and lead localization accuracy. OBJECTIVES: The aim is to investigate a novel anesthesia regimen of ketamine-induced conscious sedation for the physiological testing phase of DBS surgery. METHODS: Parkinson's patients undergoing subthalamic DBS surgery were randomly divided into experimental and control groups. During physiological testing, the groups received 0.25 mg/kg/h ketamine infusion and normal saline, respectively. Both groups had moderate propofol sedation before and after physiological testing. The primary outcome was recording quality. Secondary outcomes included hemodynamic stability, lead accuracy, motor and cognitive outcome, patient satisfaction, and adverse events. RESULTS: Thirty patients, 15 from each group, were included. Intraoperatively, the electrophysiological signature and lead localization were similar under ketamine and saline. Tremor amplitude was slightly lower under ketamine. Postoperatively, patients in the ketamine group reported significantly higher satisfaction with anesthesia. The improvement in Unified Parkinson's disease rating scale part-III was similar between the groups. No negative effects of ketamine on hemodynamic stability or cognition were reported perioperatively. CONCLUSIONS: Ketamine-induced conscious sedation provided high quality microelectrode recordings comparable with awake conditions. Additionally, it seems to allow superior patient satisfaction and hemodynamic stability, while maintaining similar post-operative outcomes. Therefore, it holds promise as a novel alternative anesthetic regimen for DBS. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Neural Representations of Emotional Experiences Are More Similar Than Those of Neutral Experiences.

Stimuli that evoke the same feelings can nevertheless look different and have different semantic meanings. Although we know much about the neural representation of emotion, the neural underpinnings of emotional similarity are unknown. One possibility is that the same brain regions represent similarity between emotional and neutral stimuli, perhaps with different strengths. Alternatively, emotional similarity could be coded in separate regions, possibly those sensitive to emotional valence and arousal. In behavior, the extent to which people consider similarity along emotional dimensions when they evaluate the overall similarity between stimuli has never been investigated. Although the emotional features of stimuli may dominate explicit ratings of similarity, it is also possible that people neglect emotional dimensions as irrelevant to that judgment. We contrasted these hypotheses in (male and female) healthy controls using two measures of similarity and two picture databases of complex negative and neutral scenes, the second of which provided exquisite control over semantic and visual attributes. The similarity between emotional stimuli was greater than between neutral stimuli in the inferior temporal cortex, the fusiform face area, and the precuneus. Additionally, only the similarity between emotional stimuli was significantly represented in early visual cortex, anterior insula and dorsal anterior cingulate cortex. Intriguingly, despite the stronger neural similarity between emotional stimuli, the same participants did not rate them as more similar to each other than neutral stimuli. These results contribute to our understanding of how emotion is represented within a general conceptual workspace and of the overgeneralization bias in anxiety disorders.SIGNIFICANCE STATEMENT We tested differences in similarity between emotional and neutral scenes. Arousal and negative valence did not increase similarity ratings. When conditions were equated on semantic similarity, participants rated emotional stimuli as similar to each other as neutral ones. Despite this equivalence, the similarity among the neural representations of emotional compared with neutral stimuli was higher in regions, which also expressed similarity between neutral stimuli and in unique regions. We report a striking difference between behavioral and neural similarity; strong neural similarity between emotional pictures did not influence similarity judgements in the same participants in the behavioral rating task after the scan. These findings may have an impact on research about the neural representations of emotional categories and the overgeneralization bias in anxiety disorders.