Differential patterns of multisensory interactions in core and belt areas of human auditory cortex Christoph Lehmann, a,b, * Marcus Herdener, a Fabrizio Esposito, c Daniela Hubl, a Francesco di Salle, d Klaus Scheffler, e Dominik R. Bach, a Andrea Federspiel, a Robert Kretz, b Thomas Dierks, a and Erich Seifritz a a University Hospital of Clinical Psychiatry, University of Bern, 3000 Bern, Switzerland b Neuroanatomy, Department of Medicine, University of Fribourg, 1700 Fribourg, Switzerland c Department of Neurological Sciences, University of Naples ‘‘Federico II’’, 80127 Naples, Italy d Department of Neuroscience, University of Pisa, 56126 Pisa, Italy e MR-Physics, Department of Medical Radiology, University of Basel, 4031 Basel, Switzerland Received 15 April 2005; revised 23 November 2005; accepted 7 December 2005 Available online 9 February 2006 The auditory cortex is anatomically segregated into a central core and a peripheral belt region, which exhibit differences in preference to bandpassed noise and in temporal patterns of response to acoustic stimuli. While it has been shown that visual stimuli can modify response magnitude in auditory cortex, little is known about differen- tial patterns of multisensory interactions in core and belt. Here, we used functional magnetic resonance imaging and examined the influence of a short visual stimulus presented prior to acoustic stimulation on the spatial pattern of blood oxygen level-dependent signal response in auditory cortex. Consistent with crossmodal inhibition, the light produced a suppression of signal response in a cortical region corresponding to the core. In the surrounding areas corresponding to the belt regions, however, we found an inverse modulation with an increasing signal in centrifugal direction. Our data suggest that crossmodal effects are differentially modulated according to the hierarchical core-belt organization of auditory cortex. D 2006 Elsevier Inc. All rights reserved. Introduction Cortical processing of auditory information takes place in a multitude of cortical areas, localized mainly on the superior surface of the temporal lobe. This surface is formed by the superior temporal gyrus and can be divided into three parts. From anterior to posterior these are the planum polare, the transverse temporal gyri (of Heschl), and the planum temporale (Di Salle et al., 2003). Primary auditory cortex is situated in the gyri of Heschl, whereas the planum polare and the planum temporale form the secondary auditory cortex. A further anatomical distinction into a central core and a surrounding belt region can be drawn. The peripheral belt displays a cytoarchitecture, called parakoniocortexis, which is less typical than the core and which can be divided into several subfields (Kaas and Hackett, 1998; Rauschecker et al., 1995). Core and belt not only differ with respect to structural but also with respect to functional properties. In analogy to the nonprimary visual areas, where information is spatially integrated over larger receptive fields and where neurons show a response preference to aggregated, more complex visual stimuli, nonprimary neurons in the auditory belt exhibit poor and inconsistent responses to conventional pure-tone stimuli. Instead, they exhibit stronger and more specific responses to narrow bands of noise in animals (Rauschecker et al., 1995) and humans (Wessinger et al., 2001). Furthermore, animal studies show that the temporal dynamics of the neural response of core and belt regions are different. They can be broadly classified into transient and sustained activity (Kilgard and Merzenich, 1998; Recanzone, 2000). In humans, functional magnetic resonance imaging (fMRI) studies demonstrate that blood oxygen level-dependent signal (BOLD) response is composed of temporally different constituents. These include a transient and a sustained component that originate predominantly in the core (sustained) or in the belt (transient) regions of the auditory cortex (Seifritz et al., 2002). This is supported by fMRI studies demonstrating that the neural activity of the belt, compared with that of the core, is most prominent at the onset and the offset of a sound stimulus (Harms et al., 2005; Harms and Melcher, 2002). Although there is a regional processing hierarchy in auditory cortex in which information proceeds from the core through the belt to the parabelt (Kaas and Hackett, 1998), it seems that several areas are processing in parallel and receive direct inputs from the 1053-8119/$ - see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2005.12.038 * Corresponding author. University Hospital of Clinical Psychiatry, Department of Psychiatric Neurophysiology, Bolligenstrasse 111, CH- 3000 Bern 60, Switzerland. Fax: +41319309961. E-mail address: lehmann@puk.unibe.ch (C. Lehmann). Available online on ScienceDirect (www.sciencedirect.com). www.elsevier.com/locate/ynimg NeuroImage 31 (2006) 294 – 300