OGGETTI, AZIONI, LINGUAGGIO: CORRELATI NEUROFISIOLOGICI

Language can be loosely defined as the ability to associate sounds and meanings through grammar rules. The problem of its origin, the definition of its characteristics and its social and philosophical implications are a constant factor crossing the disciplines and fields of research which are very distant with each other, ranging from religion to linguistics, from anthropology to archeology, from psychology to neuroscience. More recently, two subjects of particular interest for this work have taken a great interest in the origin of language: prehistoric archeology and neuroscience, which have merged in what Renfrew (2008) defines "neuroarcheology". The approach taken in this work aims to integrate the data derived from the ancient technical behavior with the data of neurophysiology to support the motor theory about the origin of language, according to the intuition of Liberman (1985, 1991, 2000) who identifies the last constituents of speech not in the sounds, but in the articulatory gestures evolved exclusively in the service of language. The study is based on the assumption that language production and lithics assemblages possess a common neural substrate, to be found in the involvement of the motor system in cognitive processes (Fadiga, Craighero 2006; Fadiga, Craighero 2007; Rizzolatti, Arbib 1998). As shown by recent data, Broca's area (area which is located at the foot of the third frontal convolution of the left hemisphere, corresponding to the Broadmann areas 44 and 45 ), in addition to its traditional functions (linguistic production, activation during listening), seems also involved in motor tasks such as the execution of actions and the observation of similar actions performed by others (Arbib 2000; Buccino 2005). Broca's area, in fact, is involved in the production and observation of manual and orofacial gestures. These data allowed to hypothesize that this area may represent a central hub for the connection between language, movement and sensory-motor processes (Fadiga, Craighero 2006). The immediacy with which we understand the actions of others has suggested the existence of a mechanism of direct and immediate understanding where the actions performed by others are directly represented in the observer's motor system, which contains, therefore, a motor copy of the actions observed by allowing a better understanding, prior to any process of cognitive elaboration. The mechanism underlying the ability to understand others is represented by the "mirror neurons" (Rizzolatti et al. 1996). Human language may be regarded, therefore, as the evolutionary refinement of an implicit communication system based on finalist representations of actions of hand and mouth, as the precursor of Broca's area was equipped, before the emergence of language, with a system of gesture recognition through the organization and interpretation of motor sequences in terms of goals for the actions (Rizzolatti, Arbib 1998). It can be assumed, therefore, that our ancestors were endowed with a brain region in which objectives and programs were represented in a syntactic way (Fadiga, Craighero 2007). The activation of the Broca's area to the observations of the actions could therefore constitute the neurobiological connection to the motor origin of the well-contructed speech and, functionally speaking, the tool-making the intermediate step between the representation of actions and the verbal communication (Fadiga et al. 2007; Peeters et al. 2009). To support what is outlined in these theoretical premises, experimental data will be shown in order to study the cortical representation during the observation of tools (that is of tools easy to grasp with a functional purpose) by detecting cortical excitability.