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Keywords: speech production; model; fMRI; Broca’s area; premotor cortex; motor cortex; speech acquisition; sensorimotor learning; neural transmission delays This paper describes a neural model of speech acquisition and production that accounts for a wide range of acoustic, kinematic, and neuroimaging data concerning the control of speech movements. The model is a neural network whose components correspond to regions of the cerebral cortex and cerebellum, including premotor, motor, auditory, and somatosensory cortical areas. Computer simulations of the model verify its ability to account for compensation to lip and jaw perturbations during speech. Specific anatomical locations of the model’s components are estimated, and these estimates are used to simulate fMRI experiments of simple syllable production. 1 1

Recent anatomic and functional data radically changed our ideas about the organization of the motor cortex in primates. Contrary to the classic view, the motor cortex does not consist of two main areas, primary and supplementary motor areas, but of a mosaic of cortical areas with specific connections and functional properties. The caudal sector of the frontal lobe was classically subdivided into two cytoarchitectonic areas, both devoid of granular cells: area 4 and area 6 (Ref. 1; see Fig. 1A). Area 4 and most of area 6 located on the lateral convexity were thought of as a single large functional area: the primary motor cortex or M1. Area 6 located on the mesial cortical surface was considered a second motor area, usually referred to as the supplementary motor area or SMA (Ref. 16; see Fig. 1B). A recent series of anatomic and functional studies showed that this picture of the agranular frontal cortex

Awareness of self-generated movements arises from comparing motor plans, and the accompanying (hypothetical) efference copy, with the visual and proprioceptive consequences of movement. Here we used repetitive transcranial magnetic stimulation (rTMS) to investigate the role of a posterior region in the superior parietal lobule (SPL) in this process. Nine healthy volunteers performed a finger extension actively and passively while wearing a CyberGlove; the glove recorded these (actual) finger movements and used this information in real time to move a virtual hand displayed on a computer screen. To assess the participant’s awareness of movement onset, we introduced a delay between the onset of the actual and virtual movement (60–270 ms, 30 ms increments); the task was to judge whether the virtual hand movements were delayed relative to the actual hand movements. Low-frequency rTMS (15 min, 0.6 Hz) was applied either over the left SPL or the left temporal cortex (control site) to decrease excitability of these regions and, in turn, test their role in the awareness of self-generated movement. Following the SPL stimulation, participants ’ assessments of asynchrony were impaired for active but not passive movements. No significant changes were observed after rTMS applied over the control site. We suggest that these findings are consistent with the role of the SPL in evaluating the temporal congruency of peripheral (visual) and central (efference copy) signals associated with selfgenerated movements. As such, this region may contribute to the sense of ‘agency’ and its disturbances in disorders such as apraxia and schizophrenia.

This essay is a sustained attempt to bring new light to some of the perennial problems in philosophy of mind surrounding phenomenal consciousness and introspection through developing an account of sensory and phenomenal concepts. Building on the information-theoretic framework of Dretske (1981), we present an informational psychosemantics as it applies to what we call sensory concepts, concepts that apply, roughly, to so-called secondary qualities of objects. We show that these concepts have a special informational character and semantic structure that closely tie them to the brain states realizing conscious qualitative experiences. We then develop an account of introspection which exploits this special nature of sensory concepts. The result is a new class of concepts, which, following recent terminology, we call phenomenal concepts: these concepts refer to phenomenal experience itself and are the vehicles used in introspection. On our account, the connection between sensory and phenomenal concepts is very tight: it consists in different semantic uses of the same cognitive structures underlying the sensory concepts, such as the concept of red. Contrary to widespread opinion, we show that information theory contains all the resources to satisfy internalist intuitions about phenomenal consciousness, while not offending externalist ones. A consequence of this account is that it explains

attention shift was across spatial representations than when it was within the same representation. The implications for action-oriented models of attention are discussed. Although almost everyone recognizes that space is a crucial issue in studies of attention, it is interesting to note that real three-dimensional space has seldom been taken explicitly into account, as models of attention usually deal only with a somewhat artificial two-dimensional space. Indeed, only a few studies have addressed the question of whether attention can be deployed along the third dimension (Andersen, 1990; Andersen & Kramer, 1993; Atchley, Kramer, Andersen, & Theeuwes, 1997; Downing & Pinker, 1985; Gawryszewski, Riggio, Rizzolatti, & Umilt, 1987; Ghiradelli & Folk, 1996; Iavecchia & Folk, 1994; Nakayama & Silverman, 1986; Theeuwes, Atchley, & Kramer, 1998). It is worth noting that the choice of Requests for reprints should be sent to Alessandro Couyoumdjian, PhD, Department of Psychology, University

■ Ideomotor theory claims that actions are cognitively represented and accessed via representations of the sensory effects they evoke. Previous studies provide support for this claim by showing that the presentation of action effects primes activation in corresponding motor structures. However, whether people actually use action-effect representations to control their motor behavior is not yet clear. In our fMRI study, we had participants prepare for manual or facial actions on a trial-by-trial basis, and hypothesized that preparation would be mediated by the cortical areas that code for the perceptual effects of these actions. Preparing for manual action induced higher activation of hand-related areas of motor cortex (demonstrating actual preparation) and of the extrastriatal body area, which is known to mediate the perception of body parts. In contrast, preparing for facial action induced higher activation of face-related motor areas and of the fusiform face area, known to mediate face perception. These observations provide further support for the ideomotor theory and suggest that visual imagery might play a role in voluntary action control. ■