Human theta rhythm modulation by syntactic information in a lexical decision task

FERNÁNDEZ FEIJÓO, EUGENIA; JAICHENCO, VIRGINIA; ZANUTTO, SILVANO; WAINSELBOIM, ALEJANDRO

Buenos Aires, Argentina

Congreso; 14th Biennial Meeting of the International Society for Comparative Psychology; 2008

International Society for Comparative Psychology

Rhythmic cortical activity has been studied as a measure of synchronized neural firing degree over distinct brain regions. Particularly, increases in human theta rhythms (4 to 8 Hz) have been seen while performing virtual navigation tasks and with increasing working memory load. Additionally, verbal memory tasks elicit greater increases in theta rhythms compared to non-verbal working memory tasks. Recently, studies have begun to analyze theta activity in relation to syntactic processing demands. The objective of the present work was to study human rhythmic cortical activity in relation to differences in syntactic information carried by verbs. 20 subjects performed a lexical decision task with 84 verbs matched by surface frequency, length and degree of surface similarity. All syntactic information was shared except for verbal mode in 50% of the verbs. Simultaneous electrical cortical activity recordings from 21 scalp electrodes showed that the presentation of verbs in the subjunctive mode elicited a higher level of theta activity compared to verbs in the present mode in C3, P3 and Pz, and a lower level in F7, T3 and T5 within 150 to 500 ms post stimulus presentation. The obtained results could be related to differences in verbal mode accessibility when accessing syntactic information.