Poster E26, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall
Catetholaminergic modulation of evoked power related to semantic processing
Yingying Tan1, Ashley Lewis2, Peter Hagoort1,2;1Max Planck Institute of Psycholinguistics, 2Radboud University
Introduction Catecholamine neurotransmitters have been shown to play a critical role in many cognitive functions, including language processing [1, 2]. However, the neural underpinnings of the link between catecholamine and language processing remain unclear. In this study, by combining electroencephalographic and pharmacological methods, we examined the modulation effect of a catecholamine agonist (i.e., methylphenidate) on neural oscillations previously linked to semantic processing. Based on previous results [3, 4, 5], our analyses focused on four frequency bands: theta (3-7 Hz), alpha (8-12 Hz), low beta (13 – 19 Hz), and high beta (20 – 30 Hz). Methods Forty-eight healthy participants were tested in two pharmacological conditions (20 mg methylphenidate vs. Placebo), using a within-subject, double-blind, randomized design. In each condition, participants read 180 sentences where for half of the sentences the target word (TW) was semantically congruent and for the other half the TW was incongruent. To further probe whether the catecholamine effect on language comprehension is task-dependent, in one block (90 sentences), after reading the sentence participants had to judge whether the sentence was semantically congruent (Semantic-task). In the other block, participants only had to judge whether a probe word presented after the sentence was of the same font size as the words comprising the sentence (Font-task). Participants’ brain responses were recorded from 28 EEG electrodes. A sliding-window approach was used to compute time-resolved spectral power from 2 to 30 Hz. Statistical comparisons were conducted between 0 – 1000 ms after TW onset using cluster-based permutations statistics. Results In the Semantic-task, alpha/beta power was lower (600 – 1000 ms) and theta power was higher (410 – 730 ms) in the semantically incongruent condition. In the Font-task, only higher theta power in the semantically incongruent condition was evident (290 - 610 ms). Both effects have previously been linked to semantic congruency manipulations [3, 4], but interestingly the beta effect appears to depend on the task. Moreover, a modulation effect of methylphenidate was only observed in the Semantic-Task. Alpha power was lower (770 – 1000 ms), while high beta power was higher (570 - 970 ms) in the methylphenidate condition. No interaction between methylphenidate and semantic congruency was observed. Discussion Our results demonstrated a task-dependent effect of catecholamine on language processing. When semantic processing was task-relevant, a higher level of catecholamine led to an overall suppression of alpha/beta across the entire task, possibly reflecting increased attention to semantic information [6, 7]. Importantly, a higher level of catecholamine did not influence semantic processing in the same way when semantic information was task-irrelevant. Speculatively, the striatum-PFC projections, which contain a large number of catecholamine receptors, may be responsible for these modulatory effects. References [1] Grossman, M., et al., (2001). JoNS. [2] Copland, D. A., et al., (2009). Cortex. [3] Lewis, A. G., et al., (2015). Brain & Language. [4] Bastiaansen, M. C. M., et al., (2006). Prog Brain Res. [5] Dockree, P., et al., (2017). Biological Psychiatry. [6] Jensen, O., et al., (2010). Front HumNeurosci. [7] Loo, S., et al., (2004). J Clinical Neurophysiology.
Themes: Meaning: Combinatorial Semantics, Control, Selection, and Executive Processes
Method: Electrophysiology (MEG/EEG/ECOG)