When the brain accesses the meaning of a word, it undergoes two types of lexical-semantic processing: automatic and controlled. Automatic processes are not under conscious control, while controlled processes can be. The language networks involved in these types of processes differ in that automatic processes mostly recruit areas in the left temporal lobe while controlled processes recruit areas in both the left temporal lobe and the left prefrontal cortex. But describing the anatomical areas involved in certain processes can only give us a sense of the static network that supports these processes. We propose to investigate how a dynamic network for lexical-semantic processing may be created through the mechanism of synchronization of brain oscillations. It has been proposed that synchronization of brain oscillations is able to dynamically recruit local neural populations and connect far away populations for communication. Synchronization of oscillations can be measured using EEG and analyzing the time, frequency, phase, and amplitude of the data. We propose to use these methods in the novel application of studying automatic and controlled lexical-semantic processing.
The aims of this project are to study local synchronization in the left temporal and prefrontal cortices and long- distance synchronization over the left fronto-temporal network in automatic and controlled (specifically controlled single meaning selection) lexical-semantic processes;in this endeavor, we will utilize two semantic context paradigms. We will also examine how the dynamic formation of the lexical-semantic network may be disrupted in aphasics as a possible insight into their language comprehension impairments.
Some patients with an acquired disorder of language have trouble accessing the meanings of words. While we know which brain areas support this language function, we do not fully understand how these areas communicate. Disruptions in the communication of brain areas may be related to the patients'problems. This study will help researchers understand how brain areas communicate in both unimpaired and impaired language populations which are crucial steps towards understanding patients'deficits and possible treatment strategies.