was the investigation of the neural dissociation of semantic knowledge for different object types. Warrington and Shallice [4] first reported that sensory attributes are salient features for the identification of animals or fruits. In turn, functional (motor) attributes are critical characteristics for the identification of tools. Another study demonstrated that this difference not only exists between categories but also within them, e.g., the specific contributions of motor channels within a modality-specific category of artifacts ([5] for reviews, see, [6,7]). Hence, the motor repertoire becomes a semantic repertoire. In the language understanding literature, this modality-specific activation in conceptual knowledge has been interpreted as reflecting a mental simulation, that is, an internal enactment of the sensory-motor experience during language comprehension [8–11]. Simulation theory has claimed that the internal enactment of motor language would engage specific areas of the motor cortex, which control the simulated effector of the action [12–18]. Recent reports based on ERP [19] and Magnetoencephalographic (MEG) studies [20] have confirmed that action words denoting motor programs of different effectors activate specific motor processes in the brain, and this activation occurs early after stimulus presen- tation. Nevertheless, some criticisms have been raised about the radical hypothesis of motor-language interaction (e.g., [21–24]). Specifically, it has been argued that the available empirical evidence does not support the claims of sensory-motor resonance as a causal mechanism for bringing language comprehension and human communication within the realm of the motor system. Far from adhering to or rejecting these hypotheses, we call upon a more balanced method to consider the brain basis of language and cognition as interplay between multiple cognitive domains. Large-scale neural networks are formed dynamically, involving several parts of the cortex that are needed for one specific task [22,25–28]. Meaning and comprehension appear to be general processes of cognition, and therefore, they are the bases of language, gestures, or action [29–40]. Thus, brain processes linked to body action should be engaged during comprehension. From this point of view, semantic content would be shared between motor processing and linguistic knowledge. When these two processes (motor and linguistic) are concurrently performed, the common neural resources should cooperate, and language should facilitate actual movement when compatible. Several studies have reported this facilitation effect with single action words [12,16,41– 46]. However, word properties (including their sensory-motor attributes) are contextually dependent [47–48] and not static. To investigate the interplay between action-language and the motor system towards access to meaning, it is necessary to consider how the sentence context modifies the action verb. Several behavioral studies have provided evidence for motor resonance during sentence comprehension. One particularly refined paradigm is the ACE that was first introduced by Glenberg and Kaschak [10]. In a sentence–sensibility–judgment task, subjects were presented with sentences encoding an action involving an upper limb movement either towards or away from the subject (e.g., sentence encoding movement away from the subject: you give Liz the toy). They controlled the movement required for the response to the sensibility-judgment task. Thus, the movement implied by the action of the sentence is either compatible or incompatible to the response action. As expected, sentence processing times were significantly faster in the compatible condition. ACE has been replicated in other experiments that have demonstrated the robustness of the effect (e.g., [49–57] for an overview see, [1]). Because only ACE behavioral paradigms have identified the cross-talk between motor structures and action-sentence comprehension, several questions Neural Signatures of ACE remain about the brain correlates of this process. Thus, an exploration of the neural markers of the ACE paradigm in semantic processing and the motor response may yield important advances in the neuroscience of action-sentence blending. Within the motor-language debate, the aim of our study was to investigate brain markers of bidirectional impact between language comprehension and motor process. It was our intention to account for a genuine and online interaction, hence we combined ACE and ERP for the first time regarding the motor-to- semantics direction in addition to the previously studied semantics- to-motor direction. Additionally, other relevant aspects of this study are detailed here: a) b) c) Since previous studies have investigated only general aspects of motor action such as the effectors or direction of motion [10], we aim to investigate the neural markers of the motor- language relationship at a subtle aspect of the action (hand-shape). Most of ACE experiments have utilized first person sentences, thus they do not avoid the possibility that the activation of motor processes is due to imagery processes and therefore explain the phenomenon using confounding variables. We aim to investigate cortical responses of ACE with no first person implicated stimuli to study the robustness of effect in low imagery processes. We look to explore motor-language integration with independence from the intention or attention of the subjects. This could be achieved by an ACE task with motor aspects that were not relevant to the task, then it would be suggested that the compatibility effect is automatic and independent from cognitive control (e.g., attention). The technique of ERPs is a precise tool regarding time resolution (on the order of milliseconds) that incorporates the recording of ongoing electrophysiological activity using electroen- cephalography (EEG). ERPs result from the synchronous activation of neural subpopulations that occur in response to events (sensory, motor or cognitive). ERPs are the sum of the activity of excitatory postsynaptic potential and inhibitory postsynaptic potential activated in response to each new stimulus. Semantic processing has been tracked with the N400 compo- nent, a large negative deflection in the ERP occurring approxi- mately 400 ms after the presentation of a word. Typically, the N400 is larger when a stimulus is difficult to integrate into a previous semantic context [58]. The N400 effect has been reported for semantic violations in language and for the processing of other meaningful stimuli (e.g., [29,59–61]). N400 is thought to reflect the activation of amodal semantic memory [62]. In our experiment, the content of the sentences was related to the hand- shape response. Consequently, the compatible or incompatible conditions were a combination of semantic processing and motor performance (participant hand-shape response). Because one of the meaningful parts of the incompatible condition of this experiment was not linguistic (motor response), we expected to find an N400-like modulation. N400-like effects are not restricted to linguistic stimuli [63]. The movement-related cortical potentials (MRCP) associated with self-paced movements are considered a measure of motor cortex excitability [64] and allow the exploration of cortical changes related to motor preparation and execution. The first component related to this study is a negativity measured over Cz beginning shortly before the response onset (290 ms) that has been called motor potential (MP; [65]) or late motor-related PLoS ONE | www.plosone.org 2 July 2010 | Volume 5 | Issue 7 | e11751