Reading, hearing, and the planum temporale Bradley R. Buchsbaum, * Rosanna K. Olsen, Paul F. Koch, Philip Kohn J. Shane Kippenhan, and Karen Faith Berman Department of Health and Human Services, Unit on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD, USA Received 22 April 2004; revised 16 August 2004; accepted 19 August 2004 Available online 11 November 2004 Many neuroimaging studies of single-word reading have been carried out over the last 15 years, and a consensus as to the brain regions relevant to this task has emerged. Surprisingly, the planum temporale (PT) does not appear among the catalog of consistently active regions in these investigations. Recently, however, several studies have offered evidence suggesting that the left posteromedial PT plays a role in both speech production and speech perception. It is not clear, then, why so many neuroimaging studies of single-word reading—a task requiring speech production—have tended not to find evidence of PT involve- ment. In the present work, we employed a high-powered rapid event- related fMRI paradigm involving both single pseudoword reading and single pseudoword listening to assess activity related to reading and speech perception in the PT as a function of the degree of spatial smoothing applied to the functional images. We show that the speech area of the PT [Sylvian–parietal–temporal (Spt)] is best identified when only a moderate (5 mm) amount of spatial smoothing is applied to the data before statistical analysis. Moreover, increasing the smoothing window to 10 mm obliterates activation in the PT, suggesting that failure to find PT activation in past studies may relate to this factor. D 2004 Elsevier Inc. All rights reserved. Keywords: Planum temporale; fMRI; Sylvian–parietal–temporal Introduction The planum temporale (PT) is emerging as a site of critical importance in several strands of neuroscientific research in the domain of language and auditory processing. The well-known observation of a leftward asymmetry in the size of the PT and its central location within the classically language-crucial Wernicke’s area has made the PT a bprime suspectQ when it comes to seeking the neural basis of abnormal linguistic behavior such as that seen in dyslexia (poor reading) and schizophrenia (e.g., auditory halluci- nations and thought disorder) that cannot be easily explained by low level sensory dysfunction (Josse and Tzourio-Mazoyer, 2004; Josse et al., 2003; Shapleske et al., 1999). In the cognitive neuroscience community, the PT is increasingly viewed as a relay station between the auditory-sensory cortex of the superior temporal lobe and other, mainly motor-oriented, cortical areas. For instance, Griffiths and Warren (2002) see the PT as a bcomputational hubQ that btransform[s] incoming auditory patterns into information about acoustic objects and position that could be used in other cortical areas.Q In a similar vein, Hickok and Poeppel (2004) have posited that the posterior PT acts as an auditory-motor interface that transforms sound-based representa- tions of speech in auditory cortex to their articulatory counterparts in frontal cortex. Both of these ideas place the PT within an auditory bdorsal streamQ that has recently been proposed (Hickok and Poeppel, 2000; Rauschecker and Tian, 2000) in analogy to the well-known dorsal stream of the visual system (Ungerleider and Mishkin, 1982), and for which an anatomical basis has been established in the monkey (Romanski et al., 1999). While dorsal stream processing in vision has traditionally been aligned with spatial bwhereQ functions, there is a growing literature that demonstrates the existence of visuomotor integration systems in the visual dorsal stream (Andersen, 1997; Milner and Goodale, 1995; Rizzolatti et al., 1996). Thus, many argue that the perceptual analysis of visual stimuli is not limited to a passive reconstruction of the external world, but rather involves a mode of analysis that has been termed bperception for actionQ (Fuster, 1997; Milner and Goodale, 1995)—a process that moves from the determination of an object’s identity and spatial location (bwhatQ and bwhereQ) to an assessment of that object’s potentialities and prospective uses (bhowQ), especially those that would necessitate quick action on the part of the observer. In the exercise of natural language, it is easy to see a similar perception-action cycle at work: conversation proceeds from speaker to hearer and back again, with each new message depending largely on that which preceded it. At the developmental level, it is clear that for a child to acquire language, he must learn 1053-8119/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2004.08.025 * Corresponding author. Department of Health and Human Services, Unit on Integrative Neuroimaging, Clinical Brain Disorders Branch, National Institute of Mental Health, National Institutes of Health, IRP, 9000 Rockville Pike, Building 10, Room 4C-101, Bethesda, MD 20892- 1365. Fax: +1 301 496 7437. E-mail address: brad.buchsbaum@nih.gov (B.R. Buchsbaum). Available online on ScienceDirect (www.sciencedirect.com). www.elsevier.com/locate/ynimg NeuroImage 24 (2005) 444 – 454