P04.23 Functional MRI as a potential biomarker for concentration deficits in brain tumor patients

Abstract

INTRODUCTION: Brain tumor patients frequently complain about problems with concentration and focus. These problems can greatly affect the socio-professional quality of life of patients. Unfortunately, the underlying neurobiological cause of these problems is still largely unclear. In order to better understand these complaints, we are currently looking for functional MRI-biomarkers for concentration. We define concentration as a state of the brain that facilitates cognitive performance. In a previous fMRI study with healthy controls we found that concentration was specifically associated with inhibition of the brain activity in the extended area around the posterior cingulate (ePCC). Here, we present results of an ongoing patient study, where we compared brain activity in ePCC between HC and brain tumor patients before and after surgery, during tasks that required a high level of concentration on visual stimuli. MATERIALS AND METHODS: Participants performed a task in which they needed to detect the letter 'X' among other consonants presented visually in a fast sequence. While this task is relatively simple, it does require a high level of continuous concentration. At the time of submission of this abstract, functional MRI scans were acquired in 20 healthy controls (HC), as well as in 11 brain tumor patients pre-surgery (4 low grade glioma, 7 meningioma). Five patients were also scanned 3 months after surgery (2 low grade glioma, 3 meningioma). For all scans, we calculated the percentage signal change in the ePCC. The deactivation in ePCC was compared between HC and tumor patients pre-as well as post-surgery (independent sample t-tests). In addition, we compared activity in ePCC in the subgroup of patients with a pre-and post-surgery fMRI scan (paired sample t-test). RESULTS: All participants executed the task well, with very few incorrect responses. Before surgery, patients showed stronger deactivation in ePCC than HC, and this difference was near significant (t = 2.01, p = 0.053). After surgery, patients also showed stronger deactivation than HC (t = 5.51, p <0.001). In the small subgroup of patients with both pre-and post-surgery scans, we found a trend towards stronger deactivation in ePCC after surgery (t = 2.39, p = 0.076). CONCLUSIONS: Our study indicates that patients show greater deactivation of the ePCC during tasks that require a high level of concentration, while maintaining normal performance. Preliminary results indicate that this effect may become even larger after surgery. The greater deactivation may be caused by an increased vulnerability for interfering processes in the brain. Alternatively, it may be a result of a reduced capability to optimally tune the brain to the task.