Changes in cortical activity during language processing and effects of affective context

Heim, S., Keil, A., Eulitz, C., and Elbert, T.
Department of Psychology, University of Konstanz, Germany

In an earlier study involving language-impaired children, we observed that improvements in various literacy skills following linguistic training are mirrored in altered magnetic brain activity. One of the questions that emerged from this finding was whether changes in cortical activity are influenced by context properties such as affective or motivational variables. In the current study, we used a classical conditioning paradigm to investigate effects of learned motivational significance in normal adult subjects. Stimuli were syllables of a /ba/-/da/ continuum based on pre-experimental identification-task data of 20 healthy adults (pre-experimental group). In the experimental group, aversive white noise (UCS) was paired with two exemplars of /ba/ stimuli (CS+) near the category boundary of the continuum. Two /da/ stimuli in the vicinity of the category border served as the CS- and signaled absence of white noise. The control group was exposed to the same syllables without presentation of the UCS. In both the experimental and control condition, the electroencephalogram (EEG) was recorded while subjects passively listened to the stimuli. Before and after recordings subjects were asked to identify the syllables in a categorical perception task. Ongoing analyses of the EEG data obtained within the experimental group revealed amplitude modulations as a function of stimulus properties (CS+ vs. CS-). No differential response to the syllables was found for the control group. However, only the control group perceived stimuli near the category boundary differently after than before the EEG session. Our preliminary results point to the role of affective/motivational context in language processing.