The Role of Sensorimotor Grounding of Concepts in Semantic Memory Retrieval
Semantic memory accumulates, stores, and organizes knowledge. Proper retrieval from semantic memory is necessary for human adaptive behavior – perception, attention, thinking, and verbal communication. Neuroimaging studies have revealed that controlled semantic processing utilizes the left prefrontal cortex (PFC). However, the functional role of the PFC remains poorly understood. The non-invasive transcranial direct-current stimulation (tDCS) technique has become an increasingly popular way to understand cognitive processing. Marko and Riečanský  found that stimulation of the left PFC supports inhibitory processing during semantic memory retrieval. The purpose of this master thesis is to study the role of left PFC during automatic and controlled semantic memory retrieval in more depth. We will focus on the problem from the perspective of the theory of grounded cognition which proposes that cognitive processes are shaped by our bodily experiences and that concepts are grounded in sensory and motor experiences . Therefore, we will explore the effect of the sensorimotor grounding of words on semantic memory processing and retrieval using the tDCS. In the first data collection phase, we will collect sensorimotor ratings of Slovak words. Participants will be given a list of words and after reading the instructions, they will be asked to rate on the 7-point rating scale the degree of grounding in distinct modalities (sound, shape, color, taste, smell, manipulation, and motion). In the second phase of data collection, we will use a double-blind, randomized, placebo-controlled experiment. Participants from three distinct groups will receive anodal (tDCS) over the left lateral PFC, a control tDCS over the right lateral PFC, or sham stimulation. Cognitive tests will be administered in three blocks: baseline, online, and offline with respect to stimulation (tDCS). During the automatic retrieval task, the participants will be presented with a word on a computer screen and they will be asked to type on the keyboard a word associated with the stimulus word. Conversely, during the controlled retrieval task, they will be asked to type in a word not associated with the stimulus. We will measure the retrieval speed, number of errors, and number of intrusions during the execution of the tasks (incorrect words that “pop up” in mind, before the participant comes up with a correct answer). After collecting the data, we will try to answer whether the sensorimotor grounding predicts the participants' performance on the semantic memory tasks. Furthermore, we will try to explain the role of the left PFC in semantic memory retrieval and processing depending on the degree of sensorimotor grounding of the stimulus words.
 M. Marko and I. Riečanský, ‘The left prefrontal cortex supports inhibitory processing during semantic memory retrieval’, Cortex, vol. 134, pp. 296–306, 2021.
 D. Kemmerer, Cognitive Neuroscience of Language, 1st ed. Psychology Press, 2014.