Poster Session A, Saturday, March 23, 1:30 pm - 3:30 pm, Pacific Concourse
Lexical-semantic and executive deficits revealed by computational modelling: a drift diffusion model perspective
Lara Todorova1, David Neville1, Vitoria Piai1,2; 1Radboud University, Donders Institute for Brain, Cognition and Behaviour, Donders Center for Cognition, Nijmegen, 2Department of Medical Psychology, Radboud University Medical Center, Nijmegen
When asked to match a word to a picture, participants are slower and less accurate for related word-picture pairs (word: banana, picture: apple) relative to unrelated pairs (word: banjo, picture: apple). The underlying nature - semantic or executive - of this interference effect is still debated. We analyzed the word-picture matching (WPM) performance of patients with stroke-induced lesions to the left-temporal (N = 6) or left-frontostriatal cortex (N = 6) and matched controls (N = 12) using drift diffusion model (DDM). DDM considers decision making as a process of stochastic evidence accumulation described by model parameters (i.e., decision boundary and drift rate), which have established cognitive interpretation. The model parameters were compared between controls and patients to investigate the mechanisms of WPM interference. WPM performance in controls tapped into the amount of information (decision boundary) needed to make a decision: a higher threshold was associated with related relative to unrelated word-picture pairs, but there was no difference in the quality of the evidence (drift rate). This suggests an executive rather than semantic mechanism underlying WPM interference. Patients with lesions to left-temporal cortex showed no differences either in drift rate or decision boundary between conditions. By contrast, patients with frontostriatal lesions exhibited both increased drift rate and decision boundary for unrelated relative to related pairs. Thus, left-frontostriatal and temporal damage affects the computations required by WPM differentially, resulting in systematic deficits across lexical-semantic memory or executive functioning. These results support a neuronal dissociation between lexical-semantic memory and semantic control mechanisms.
Topic Area: LANGUAGE: Semantic