Effects of intermodal attention on the auditory steady-state response and the event-related potential KATJA SAUPE, ANDREAS WIDMANN, ALEXANDRA BENDIXEN, MATTHIAS M. MU ¨ LLER, and ERICH SCHRO ¨ GER Institute of Psychology I, University of Leipzig, Leipzig, Germany Abstract The aim of the present study was to simultaneously measure and compare intermodal attention effects in event-related brain potentials (ERPs) and auditory steady-state responses (ASSRs). For this purpose, 40-Hz amplitude modulated tones and a visual fixation cross were presented concurrently. By means of target detection tasks either on the sounds or on the fixation cross, participants’ attention was directed to the respective modality. Attended sounds elicited a negative difference (Nd) in the ERP relative to unattended sounds. Nd was divided into an early and a late part as often observed for intramodal attention. Moreover, attention to the sounds led to a significant enhancement of the ASSR. This modulation of the ASSR by intermodal attention is demonstrated for the first time in the EEG. The present data suggest that ASSRs could provide a useful tool for the investigation of the neural dynamics of intermodal attentional processes. Descriptors: Event-related potentials, Auditory steady-state response, Intermodal attention, Negative difference effect An important function of attention is the selection of informa- tion from our complex sensory environment. It is generally as- sumed that a collection of hierarchical filters provides various levels of selection (Hansen & Hillyard, 1983; Heslenfeld, 1998, cited in Talsma & Kok, 2001). One of these levels is considered to select information among sensory modalities, which leads to amplified processing of stimuli in the attended modality com- pared to stimuli in the unattended modality. The relevance of this mechanism can be illustrated by the example of trying to ignore the background noise in an open-plan office while focusing on a visual task on the computer monitor. For the synchronized in- terplay in an orchestra, it can also be advantageous to concen- trate only on visual information, given by the conductor while ignoring the time-delayed auditory input from other distant players. A reversed situation would be, for instance, the concen- tration on the auditory information during an important tele- phone call while ignoring the surrounding visual input. The difference in the processing of a stimulus in one modality when attention is devoted to this stimulus versus when attention is allocated to a different modality is described in the literature as intermodal attention (Alho, Woods, & Algazi, 1994; Alho, Woods, Algazi, & Na¨a¨ta¨nen, 1992; de Ruiter, Kok, & van der Schoot, 1998; Eimer & Schro¨ger, 1998; Talsma & Kok, 2001, 2002; Woods, Alho, & Algazi, 1992). The aim of the present study was to simultaneously measure and compare intermodal attention effects in event-related brain potentials (ERPs) and auditory steady-state responses (ASSR). ERP effects of intermodal attention are well investigated. Similar to intramodal attention situations (Alho, Teder, La- vikainen, & & Na¨ a¨ ta¨ nen, 1994; Alho, Woods, et al., 1994; Arnott & Alain, 2002; Hansen & Hillyard, 1980, 1984; Hillyard, Hink, Schwent, & Picton, 1973; Na¨a¨ ta¨ nen, 1992), selective attention during intermodal designs leads to a negative difference (Nd) effect between ERPs for sounds when the auditory modality is attended and the same sounds when instead the visual (Alho, Woods, et al., 1994; Eimer & Schro¨ger, 1998; Talsma & Kok, 2001, 2002; Woods et al., 1992) or the somatosensory (Ho¨ tting, Ro¨ sler, & Ro¨ der, 2003) modalities are attended. Little is known, however, about intermodal attention effects on the ASSR. Therefore, one major question of the present study was whether intermodal attention effects can also be shown in ASSR measured in the electroencephalogram (EEG). Steady- state responses are continuous oscillatory brain responses elicited by periodic stimulations, like flickering of a visual stimulus or amplitude modulations in a sound. The almost sinusoidal wave- form of the steady-state response has the same fundamental fre- quency as the periodic rhythm of the stimulation (Regan, 1989). Attentional modulations of steady-state responses have been demonstrated in the EEG both for the visual and somatosensory modalities in a large number of studies (e.g., Giabbiconi, Tru- jillo-Barreto, Gruber, & Mu¨ ller, 2007; Mu¨ ller, Picton, et al., 1998; Mu¨ ller, Teder-Sa¨leja¨rvi, & Hillyard, 1998). This work was supported by a stipend of the German Research Foundation (graduate program ‘‘Function of attention in cognition’’; DFG 1182). The experiment was realized using Cogent 2000, developed by the Cogent 2000 team at the FIL and the ICN. Address reprint requests to: Katja Saupe, Institute of Psychology I, University of Leipzig, Seeburgstr. 14–20, D-04103 Leipzig, Germany. E-mail: saupe@uni-leipzig.de Psychophysiology, 46 (2009), 321–327. Wiley Periodicals, Inc. Printed in the USA. Copyright r 2009 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2008.00765.x 321