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Using EEG to Examine the Cognitive and Neural Mechanisms of Action Semantics in Primary Progressive Aphasia and Parkinson’s Disease
Poster Session D, Saturday, September 13, 5:00 - 6:30 pm, Field House
Amy Lebkuecher1,2, Laurel Buxbaum2, Chia-Lin Lee3, Kristen Li1, Branch Coslett1; 1Laboratory for Cognition and Neural Stimulation, University of Pennsylvania, Philadelphia, PA, USA, 2Cognition and Action Laboratory, Moss Rehabilitation Research Institute, Philadelphia, PA, USA, 3Graduate Institute of Linguistics, Department of Psychology, Graduate Institute of Brain and Mind Sciences, and Neurobiology and Cognitive Neuroscience Center National Taiwan University, Taipei, Taiwan
The extent to which gesture and language access a common repository of semantic representations or separate stores of semantic knowledge remains a topic of theoretical debate (e.g., Leshinskaya & Caramazza, 2016). Within this debate, there is further disagreement concerning the involvement of sensorimotor brain regions in semantic representations. Investigating the relationship between gesture and language comprehension across neurodegenerative populations with and without prominent motor deficits will further inform these debates. The current study uses EEG to explore the role of action semantics in the comprehension of nouns and verbs in Primary Progressive Aphasia (PPA), a neurodegenerative disease without prominent motor deficits characterized by language impairment, and Parkinson’s Disease (PD), a neurodegenerative disease with prominent motor deficits. For the purposes of the current project, action semantics is defined as long-term knowledge about actions (e.g., manual gestures) that is accessible to language and is activated during the execution, observation, and mental simulation of actions. Specifically, this study examines neurophysiological and behavioral evidence that the observation of gestures facilitates language comprehension in at least some individuals with PPA and PD. Our experiment uses an event-related paradigm to investigate whether observing a video of a manual gesture facilitates the comprehension of a semantically related, auditorily presented noun or verb. Participants are asked to indicate via keypress whether the gesture and word match or mismatch. We present data from a total of 10 individuals with PPA, 10 individuals with PD, and 20 age-matched neurotypical controls. To examine whether sensorimotor disruption affects gestural facilitation in these populations, we evaluated event-related desynchronization of the β oscillation and µ rhythm as indicators of sensorimotor aspects of action semantics (e.g., Schaller et al., 2017). If the sensorimotor aspect of action semantics is intact, we expected to observe greater event-related desynchronization of the β oscillation or µ rhythm in response to a matching gestural prime and target word. If this desynchronization is reduced or absent, then this would suggest sensorimotor disruption may contribute to any observed action semantics deficits. We examined the N400 as an index of semantic priming across gesture and target word, as well as how this effect relates to behavioral evidence for priming (e.g., faster response time to matching gestural primes and target words). We expected individuals with impaired comprehension to exhibit a reduced response time (RT) benefit for trials where a matching gesture precedes the target word and a reduced or absent N400 effect in response to mismatches. Data collected to date demonstrate that individuals with semantic impairment exhibit faster RT for trials with a matching gestural prime and target word relative to mismatch trials. Conversely, individuals with intact semantic abilities demonstrated equally fast RT on trials with matching and mismatching gestural primes. Additionally, the behavioral differences appear to be associated with individual differences in N400 amplitude and location as well as differences in desynchronization of the β oscillation and µ rhythm. Finally, we consider differences in the EEG components of interest across neurodegenerative populations.
Topic Areas: Signed Language and Gesture, Multisensory or Sensorimotor Integration