Functional Intraoperative Mapping of the Left Temporal Lobe

Our research was devoted to the functional intraoperative mapping of the left temporal lobe. The goal was to compare the results of mapping, performed using a traditional task – object naming, and new task, developed based on modern neurocognitive models of language. The traditional task for language mapping is object naming as seeing a picture and producing a noun engages lexical-semantic input and output processes that are indispensable for everyday communication (Goodglass & Wingfield, 1977). Moreover, this task allows to map the process of lexical access, based on a distributed network of zones of the frontotemporal-parietal cortex. Despite the positive results, having object naming as the main component of assessment in awake surgery may not be always sufficient. There are language processes typically used in everyday language that cannot be assessed with object naming and the neural correlates of this task may be partially segregated from those of other processes. Thus, we designed a new task – the test for phonological judgement that allows mapping the superior temporal sulcus and is aimed at identifying impairments of phoneme perception. As a result of the study, it was found that the posterior part of the superior temporal gyrus was sensitive to both tasks. In addition to overlapping areas that were responsive to both tasks, we also found a dissociation between the two tests. The positive sites (with the stimulation of which the patient did not answer correctly), found when using the phoneme discrimination task, were located along the superior temporal sulcus, and when using the task for naming objects – in the middle and the posterior part of superior temporal gyrus and also in the inferior frontal gyrus. This confirms the functional segregation of the temporal lobe of the left hemisphere and emphasizes the importance of using specific linguistic tasks for intraoperative speech mapping in different parts of the brain.