Verbal Learning Impairment in Parkinson's Disease: Role of the Frontostriatal System in Working and Strategic Memory.

INTRODUCTION: Learning is a long-term memory process, influenced by working memory control processes, including recognition of semantic properties of items by which subjects generate a semantic structure of engrams. The aim of the study was to investigate the verbal learning strategies of individuals with Parkinson's disease (PD). METHODS: Thirty individuals with idiopathic PD and healthy control (HC) subjects were tested with a multi-trial word list learning, under two conditions: without cue and then with an explicit cue suggesting the categories in the list, respectively. RESULTS: In comparison to HC subjects, individuals with PD recalled fewer words and achieved a reduced number of categorical clusters; the strategical cue did not improve their performance. CONCLUSION: This suggests, besides a difficulty in identifying the correct learning strategy, a deficit in working memory, which undermines the strategy implementation.

Insular lobe surgery and cognitive impairment in gliomas operated with intraoperative neurophysiological monitoring.

BACKGROUND: For a long time, surgery of insular gliomas was considered at high risk for postoperative cognitive deficits, but recent studies highlighted the feasibility of the surgical approach. The aims of our study were to investigate the presence of language impairment before and after surgery and the relationship between language impairment and tumor volume preoperatively and extent of resection (EOR) 3 months after surgery. METHODS: Thirty-five patients with insular gliomas underwent an extensive language assessment before and few days after surgery, and after 3 months. Intraoperative neurophysiological monitoring (IOM) and brain mapping with direct electrical stimulation (DES) were used in all the cases; 8 patients underwent awake craniotomy. Statistical analysis was performed on the language tests administered. RESULTS: Patients with pure left insular lesion showed language impairment before and after surgery. Overall, patients with a left lesion showed a drop of performance after surgery followed by a partial recovery. Moreover, when the tumor involved the insula and adjacent networks, we observed a more severe deficit. No correlations were found between tumor volume, EOR, and language impairment. CONCLUSIONS: Left insular lobe is an important hub in language networks; its involvement determines pre- and postsurgical deficits, together with the involvement of white matter connections. Tumor volume and EOR are not risk factors per se directly related to language functioning. Surgery of insular gliomas is possible with a pre- and intraoperative extensive study of the patient with IOM and awake surgery, and encouraged by the trend of cognitive recovery highlighted.

Perspectives on (A)symmetry of Arcuate Fasciculus. A Short Review About Anatomy, Tractography and TMS for Arcuate Fasciculus Reconstruction in Planning Surgery for Gliomas in Language Areas.

Gliomas are brain tumors that are treated with surgical resection. Prognosis is influenced by the extent of resection and postoperative neurological status. As consequence, given the extreme interindividual and interhemispheric variability of subcortical white matter (WM) surgical planning requires to be patient's tailored. According to the "connectionist model," there is a huge variability among both cortical areas and subcortical WM in all human beings, and it is known that brain is able to reorganize itself and to adapt to WM lesions. Brain magnetic resonance imaging diffusion tensor imaging (DTI) tractography allows visualization of WM bundles. Nowadays DTI tractography is widely available in the clinical setting for presurgical planning. Arcuate fasciculus (AF) is a long WM bundle that connects the Broca's and Wernicke's regions with a complex anatomical architecture and important role in language functions. Thus, its preservation is important for the postoperative outcome, and DTI tractography is usually performed for planning surgery within the language-dominant hemisphere. High variability among individuals and an asymmetrical pattern has been reported for this WM bundle. However, the functional relevance of AF in the contralateral non-dominant hemisphere in case of tumoral or surgical lesion of the language-dominant AF is unclear. This review focuses on AF anatomy with special attention to its asymmetry in both normal and pathological conditions and how it may be explored with preoperative tools for planning surgery on gliomas in language areas. Based on the findings available in literature, we finally speculate about the potential role of preoperative evaluation of the WM contralateral to the surgical site.