Neuroni specchio e linguaggio

Neuroni specchio e linguaggio Gloria Gagliardi [email protected] SOMMARIO Lezione del 17/11/2014: Quadro generale •  Cenni di morfologia delle aree cerebrali •  Le aree motorie (nella scimmia e nell’uomo) –  Neuroni canonici e affordances –  Neuroni specchio •  Neuroni specchio, leMura delle intenzioni ed empaNa •  “Embodied cogni2on” e teoria della mente SOMMARIO Lezione del 19/11/2014: Perché la scoperta dei neuroni specchio dovrebbe interessare al linguista? In che modo influenza la teoria del linguaggio? •  Filogenesi del linguaggio •  Ontogenesi del linguaggio –  Azione/Gesto/Linguaggio (studi di V. Volterra e ISTC-­‐CNR)
–  Case study acquisizione aNpica: l’auNsmo (V. Gallese; L. Brandi e S. Lucchesini) •  Neuroni specchio, percezione e comprensione linguisNca –  Liv. Fonologico (“Motor theory of speech percep2on”)
–  Liv. Lessicale-­‐semanNco
MORFOLOGIA delle AREE CEREBRALI (Rizzola_ e Sinigaglia, 2006) CitoarchiteMura del cervello di scimmia (Cercopiteco), mappa di Brodmann MORFOLOGIA delle AREE CEREBRALI CitoarchiteMura del cervello umano, mappa di Brodmann AREE MOTORIE Aree 4 e 6 di Brodmann, “corteccia agranulare” •  Area 4, corteccia motoria primaria, F1 •  Area 6, disNnta in 3 regioni principali (ciascuna divisa a sua volta in una parte rostrale ed una caudale): –  Regione Mesiale: F3, F6 –  Regione Dorsale: F2, F7 –  Regione Ventrale: F4, F5 AREE MOTORIE Area 4 •  Controllo del movimento volontario •  Organizzazione somatotopica Semiunculus di C. Woolsey Homunculus motorio di W. Penfield Controllo del Movimento La mano ha una struMura anatomica molto complessa: •  39 muscoli (estrinseci ed intrinseci) che agiscono su 18 giunN •  23 gradi di libertà dal punto di vista cinemaNco COME VIENE CONTROLLATO IL MOVIMENTO? Area F5 (scimmia) PROPRIETA’ GENERALE DELL’AREA F5 (Rizzola_ et al. 1988) Neuroni dell’area F5 hanno proprietà più complesse di quelle della corteccia motoria primaria. Codificano qualcosa di più astraMo del singolo movimento: scaricano in concomitanza di a_ motori specificamente goal-­‐related. “The funcNonal properNes of neurons located in the rostral part of inferior area 6 were studied in awake, parNally restrained macaque monkeys. The most interesNng property of these neurons was that their firing correlated with specific goal-­‐related motor acts rather than with single movements made by the animal.” “All together these neurons form a vocabulary where proximal and distal movement necessary for reaching, grasping, holding and bringing the food to the mouth are represented.” Una dimostrazione… Umiltà et al. 2008 “Primates are able to interact with objects not only by using their natural effectors, but also by using tools. Common tools, such as sNcks, stones, and rakes, act basically as funcNonal extensions of natural effectors. With pracNce, they become parts of the agent’s body schema.” LO STUDIO: •  Two adult macaque monkeys (Macaca nemestrina) were used. •  Single-­‐unit acNvity was recorded from areas F5 and F1 •  Before recording, the monkeys were trained to grasp food placed in front of them by using two types of tools. •  To grasp the object with normal pliers, the monkey has to close its hand (A), whereas with the reverse pliers, the monkey has to open its hand (B). “What could be the mechanism that allows a transformaNon of a goal into appropriate movements even when an opposite sequence of movements is necessary to achieve the goal? Our findings show that, aqer learning, the correct movement selecNon occurred immediately as soon as the monkey grasped one or the other type of pliers.” goal-­‐centered organizaNon of primate motor cortex Neuroni canonici Murata et al. 1997 •  Visual and motor properNes of single neurons of monkey ventral premotor cortex (area F5) were studied •  The employed objects were six different three-­‐dimensional (3-­‐D) geometric solids. • 
FINDINGS Two main types of neurons were disNnguished: motor neurons and visuomotor neurons. –  Motor neurons discharged in associaNon with grasping movements. Most of them discharged selecNvely during a parNcular type of grip. Different objects, if grasped in similar way, determined similar neuronal motor responses. –  Visuomotor neurons also discharged during acNve movements, but, in addiNon, they fired also in response to the presentaNon of 3-­‐D objects. • 
every Nme an object is presented, its visual features are automaNcally (regardless of any intenNon to move) ‘‘translated’’ into a potenNal motor acNon. This potenNal acNon describes the pragmaNc physical properNes of the objects. Neuroni canonici CaraMerisNche: •  Neuroni visuomotori che scaricano sia durante gli a_ motori, sia alla presentazione di ogge_ 3D. •  Ogni volta che un oggeMo viene percepito, le sue caraMerisNche fisiche vengono automaNcamente tradoMe in un potenziale motorio di azione. •  La visione di un oggeMo a_va immediatamente la selezione delle proprietà fisiche che permeMono di interagire con esso è AFFORDANCES Affordance ConceMo introdoMo da Gibson “The affordances of the environment are what it offers the animal, what it provides or furnishes, either for good or ill. The verb to afford is found in the dicNonary, the noun affordance is not. I have made it up. I mean by it something that refers to both the environment and the animal in a way that no exisNng term does. It implies the complementarity of the animal and the environment.” (Gibson 1979, 127) DeFelice (2013) “L'autore definisce le affordances come “possibilità d'azione” offerte dagli ogge_: il conceMo non va ridoMo però alle semplici proprietà fisiche e visivamente percepibili degli ogge_ in sé, ma è intrinsecamente relazionale, in quanto implica che sussista una complementarietà tra gli agenN e l'ambiente (e gli ogge_ che ne fanno parte)” DeFelice (2014), Definizione di Affordance: “invariant set of objects’ physical properNes that offer possibiliNes for acNons”. Affordances e neuroni canonici •  Where are Affordances grounded? CANONICAL NEURONS CIRCUITS •  La percezione di proprietà di ogge_ manipolabili a_va una sorta di simulazione dell’azione nei circuiN cerebrali •  Stre_ssima relazione tra azione e percezione: l’abilità di agire dipende dalla abilità di percepire. Neuroni Canonici nell’uomo Grezes et al. 2003a •  S2muli: color video recordings (3.5 s each) of objects, grasping pantomimes, and objects being grasped. •  The subjects viewed the videos and were required either to passively observe or to execute the appropriate grip on a manipulandum. –  In the observaNon context, subjects observed an object (OO), observed a grasp (OG), or observed an object being grasped (OGO). –  In the execuNon condiNons, the subjects executed the grasp appropriate for the object that they viewed (EO), imitated the pantomime they viewed (EG), or imitated the hand grasping an object (EGO). •  Two different objects were used; one had large opposiNon axes and would normally be grasped with a power grip. The other object was small and would normally be grasped by a precision grip. Power grip (thumb + surface of the palm + all other fingers) Precision grip (thumb + index finger) •  fMRI scanning •  The manipulandum employed for responses had two components. The first component consisted of a wooden cylinder […], that was used for the power grip response. AMached to the top part of the cylinder, the second component was made of a 2-­‐cm-­‐square and 1.5-­‐cm-­‐thick piece of wood and was used for the precision grip response. Both components contained a force transducer to record grip responses. Comparing those data with electrophysiological findings in monkeys, the concomitant acNvaNon of parietal and pre-­‐motor areas during passive observaNon of an object and during execuNon of a grasp toward that object seems to correspond to the circuit shown in the macaque brain, that is, the parietal area AIP and the premotor area F5, where canonical neurons have been recorded. Buccino et al. 2009 •  TMS: Transcranial MagneNc SNmulaNon1 •  STIMULI: The sNmuli set was made of 6 × 2 × 2 sNmuli, each object being represented in two horizontal orientaNons (one compaNble with a right-­‐hand grasp, the other with a leq-­‐hand grasp) and according to two different types of handle (one normal and compaNble with a hand grasp, the other broken). • 
• 
Motor programs for grasping objects are specifically related to some specific pragmaNc features of objects like, for example, handle orientaNon. The recruited motor programs are fine tuned to privileged components so that as soon as these are violated, the related motor programs are consequently interrupted, as tesNfied by MEPs recorded when objects were presented with the broken handle on the right side 1
Applicazione di un impulso magneNco alla corteccia. Se l’impulso è applicato alla corteccia motoria è possibile registrare i potenziali evocaN motori (MEP) nei muscoli controlaterali mediante eleMromiografia. Neuroni Specchio ScoperN negli anni ‘90, a Parma [Rizzola_, Gallese, Fadiga, Fogassi] Primi arNcoli: Rizzola_ et al. 1996; Gallese et al. 1996 Dove? Area F5 della scimmia Cosa sono? sistema di neuroni parNcolari, a_vi sia quando il soggeMo compie l’azione, che quando l’azione è compiuta da un altro agente e semplicemente osservata. cfr. Gallese et al. 1996: Registrazione di 532 neuroni dell’area F5. 92 hanno proprietà “mirror”. Di quesN: •  51 si a_vano durante l’osservazione di una singola, specifica azione compita con la mano. •  38 si a_vano per 2 o 3 azioni. •  3 si a_vano quando la scimmia osserva il ricercatore prendere cibo con la bocca o con la mano 25: mirror-­‐like, rispondono all’osservazione di azioni della mano ma non hanno proprietà motorie. Neuroni specchio nella scimmia: funzione e caraMerisNche HP: il sistema specchio gioca un ruolo nella comprensione delle azioni •  Il traMo visivo che a_va i neuroni specchio è l’interazione tra agente e oggeMo: la vista del solo agente o del solo oggeMo non produce scarica. •  I neuroni specchio della scimmia non scaricano se l’azione viene mimata dall’agente. •  I neuroni specchio si a_vano quando l’animale può prevedere la finalità dell’azione studi molto noN: –  Umiltà et al. 2001 –  Kohler et al. 2002; Keysers et al. 2003 Umiltà et al. 2001 •  Two basic experimental condiNons: –  “full vision” condiNon [the monkey was shown a fully visible acNon directed toward an object] –  “hidden” condiNon [the same acNon was presented but with its final criNcal part (hand-­‐ object interacNon) hidden]. •  The results showed that the majority of mirror neurons responded also in the hidden condiNon. •  “[…] a subset of mirror neurons becomes acNve during acNon presentaNon and also when the final part of the acNon, crucial in triggering the response in full vision, is hidden and can therefore only be inferred.” •  “This implies that the motor representaNon of an acNon performed by others can be internally generated in the observer’s premotor cortex, even when a visual descripNon of the acNon is lacking. The present findings support the hypothesis that mirror neuron acNvaNon could be at the basis of acNon recogniNon.” •  “Full visual informaNon about an acNon is not necessary to recognize its goal. AcNon understanding could be based on a mechanism that can trigger the internal motor representaNon of the acNon.” “Audiovisual” mirror neurons Kohler et al. 2002/Keysers et al. 2003 •  STIMULI= “noisy acNons” – 
– 
– 
– 
– 
– 
Peanut breaking Paper ripping PlasNc crumpling Metal hi_ng metal Paper shaking SNck dropping •  three ‘sensory’ condiNons: –  vision-­‐and-­‐sound (‘V+S’) –  vision-­‐only (‘V’) –  sound-­‐only (‘S’) •  “[…] some neurons in the ventral premotor cortex (area F5) of the monkey responding during the execuNon of acNons also respond to the vision and/or the sound of these acNons.” •  “[…] for half of the tested audiovisual mirror neurons, the amplitude of the response does not differ significantly whether the preferred acNon is heard, seen or both heard and seen.” •  “This finding is important, as it suggests that the neurons code the acNon in an abstract way, which does not depend on the source of informaNon (auditory or visual) from which the evidence about the presence of the acNon is taken.” •  cornerstone in the evoluNon of language? Non solo F5: Mirror-­‐neuron circuit (Rizzola_ e Sinigaglia, 2006) Il sistema dei neuroni specchio è bilaterale e include ampie porzioni della corteccia parietale e premotoria. •  F5 •  Area PF of Von Economo (rostral part of the inferior parietal lobule, IPL) “It receives input from STS and sends an important output to the ventral premotor cortex including area F5. PF neurons are funcNonally heterogeneous. Most of them (about 90%) respond to sensory sNmuli, but about 50% of them also have motor properNes discharging when the monkey performs specific movements or acNons”). •  STS (superior temporal sulcus) STS neurons respond to the observaNon of acNons done by but do not appear to be endowed with motor properNes.) “The corNcal mirror neuron circuit is formed by two main regions: the rostral part of the inferior parietal lobule and the ventral premotor cortex. STS is strictly related to it but, lacking motor properNes, cannot be considered part of it.” (Rizzola_ & Craighero, 2004) Neuroni specchio: funzione “The mirror system provides a way to match observa2on and execu2on od events.” [Gallese et al. 1996] Generazione di una rappresentazione interna del movimento (“simulazione”), che può avere varie funzioni: •  comprensione del significato dell’azione osservata •  leMura delle intenzioni dell’individuo che agisce (Fogassi et al. 2005) Fogassi et al. 2005 • 
• 
• 
• 
IPL (inferior parietal lobe) neurons were studied when monkeys performed motor acts embedded in different acNons and when they observed similar acts done by an experimenter. Most motor IPL neurons coding a specific act (e.g., grasping) showed markedly different acNvaNons when this act was part of different acNons (e.g., for eaNng or for placing). Many motor IPL neurons also discharged during the observaNon of acts done by others. Most responded differenNally when the same observed act was embedded in a specific acNon. e.g.: -­‐ 
intense firing when the monkey grasped a fruit to bring it to its mouth. -­‐ 
weaker response when the monkey grasped the food to place it in a container. -­‐ 
intense response when the monkey watched an experimenter perform the grasp-­‐to-­‐eat gesture. -­‐ 
weaker response to the grasp-­‐to-­‐place acNon. These neurons not only code the observed motor act but also allow the observer to understand the agent’s intenNons. Neuroni specchio nell’uomo COME? Evidenze indireMe •  EsperimenN di Npo neurofisiologico –  EEG -­‐ eleMroencefalografia: Registrazione del mu-­‐rhythm (cfr. studi di Gastaut) –  TMS -­‐ Transcranial magneNc sNmulaNon • 
brain-­‐imaging –  PET -­‐ Tomografia a emissione di positroni –  fMRI-­‐ Risonanza magneNca funzionale DOVE? Osservazione di azioni compiute da altri comporta anche nell’uomo l’a_vazione di un network complesso di aree: •  Aree visive (occipitali, temporali e parietali) •  regioni corNcali eminentemente motorie –  parte rostrale del lobulo parietale inferiore IPL –  parte inferiore del giro precentrale –  parte posteriore del giro frontale inferiore Omologo di F5 nell’uomo? AREA DI BROCA Area di Broca • 
Non è un’area esclusivamente linguisNca! • 
Corrisponde alle aree di Brodmann 44 e 45. -­‐ 
-­‐ 
• 
Area 44, Pars opercularis del giro frontale inferiore: in aggiunta alla rappresentazione del linguaggio conNene, così come F5 nella scimmia, le rappresentazioni motorie dei movimenN della mano. Area 45, pars triangularis del giro frontale inferiore: a_vata da elemenN linguisNci, sia verbali che segnaN. Connessa all’area di Wernicke aMraverso il fascicolo arcuato scimmia uomo Buccino et al. 2001 •  fRMI •  AIM: –  to localize brain areas that were acNve during the observaNon of acNons made by another individual –  to assess whether the observaNon of acNons made with different effectors would acNvate specific parts of the premotor cortex in accord with the somatotopic motor organizaNon of the region •  STIMULI: Object-­‐ and non-­‐object-­‐related acNons made with different effectors (mouth, hand and foot) were presented. –  mouth acNons: •  biNng an apple •  chewing –  hand acNons: •  reaching and grasping a ball or a liMle cup with the hand •  mimicking these acNons without the object –  foot acNons •  kicking a ball •  pushing a brake •  mimicking these acNons without the object FINDINGS: •  “ObservaNon of both object-­‐ and non-­‐object-­‐related acNons determined a somatotopically organized acNvaNon of premotor cortex. The somatotopic paMern was similar to that of the classical motor cortex homunculus.” •  “During the observaNon of object-­‐related acNons, an acNvaNon, also somatotopically organized, was addiNonally found in the posterior parietal lobe.” •  The mirror System “is not restricted to the ventral premotor cortex, but involves several somatotopically organized motor circuits.” L’ESPERIMENTO DIMOSTRA INOLTRE CHE: •  Il sistema specchio nell’uomo non è circoscriMo alla mano. •  Nell’uomo anche l’osservazione di pantomine determina l’a_vazione nei neuroni specchio. (cfr. Umiltà et al. 2001) Buccino et al. 2004 •  fRMI •  AIM: “to assess the corNcal areas acNve during the observaNon of mouth acNons performed by humans and by individuals belonging to other species (monkey and dog).” •  STIMULI: Two types of acNons were presented: biNng and oral communicaNve acNons (speech reading, lip-­‐smacking, barking). FINDINGS: •  “The results showed that when the observed acNon is common to animals and humans, there is a clear overlap between the acNvated areas, in spite of the enormous differences in the visual aspects of the observed sNmuli. In contrast, during the observaNon of acNons that, like oral communicaNve acNons, have a common goal, but are expressed differently in the three species, there is a clear difference in the distribuNon and extent of acNvaNons.” •  “Taken together, the results of the present experiment suggest that acNons made by other individuals may be recognized in different ways. AcNons belonging to the motor repertoire of the observer are mapped on his/her motor system. AcNons that do not belong to this repertoire appear to be recognized essenNally based on their visual properNes.” •  “AcNons that are not part of the motor repertoire of the observer and that therefore cannot be reproduced appear to be recognized in nonmotor terms. They are most likely understood based on visual descripNon of the observed events and inferences of their consequences and/or goals.” Neuroni specchio ed empaNa Simulazione incarnata e rispecchiamento di emozioni e sensazioni. Comprensione esperienziale delle emozioni di base, ad es. Disgusto è BASE BIOLOGICA DELL’EMPATIA Wicker et al. 2003 •  fRMI •  STIMULI: –  parNcipants inhaled odorants producing a strong feeling of disgust. –  the same parNcipants observed video clips showing the emoNonal facial expression of disgust. • 
Observing such faces and feeling disgust acNvated the same sites in the anterior insula and to a lesser extent in the anterior cingulate cortex. “Simulazione Incarnata” • 
Il meccanismo funzionale che sta alla base del doppio paMern di a_vazione dei neuroni specchio è stato definito “simulazione incarnata” (“embodied simula2on”) • 
Nuova concezione delle a_vità mentali e della cognizione: embodied (V. Gallese) / grounded (Barsalou) da meccanismo di manipolazione di simboli astra_ e rappresentazioni, basato su regole formali e processi è a ciò che emerge dall’azione del corpo nel suo contesto reale • 
• 
Capacità perce_ve e motorie non sono separabili. Da esse si sono sviluppate probabilmente anche le facoltà “superiori”. Il sistema sensomotorio di cui fano parte i neuroni specchio ha caraMere mulNmodale, e non modulare! Riassumendo •  Peculiarità dell’area F5: neuroni a_vi somatotopicamente in rapporto alla funzione, ovvero “sparano” in concomitanza di a_ motori, non di singoli movimenN. •  2 popolazioni di neuroni nella scimmia nell’uomo, con distribuzione corNcale omologa: Neuroni Canonici (Neuroni visuomotori che scaricano sia durante gli a_ motori, sia alla presentazione di ogge_ 3D) Neuroni Specchio (Neuroni visuomotori che scaricano sia durante gli a_ motori, sia durante l’osservazione dello stesso aMo motorio compiuto da un altro agente) •  SoMoclasse dei neuroni specchio audiovisivi •  Funzione dei Neuroni specchio : comprensione dell’azione + leMura dell’intenzione •  Peculiarità del sistema specchio nell’uomo: –  Non è circoscriMo alla mano –  Si a_va anche in caso di pantomina –  Simulazione incarnata: le azioni che sono fuori dal repertorio della specie non hanno risonanza motoria nell’osservatore. •  Neuroni specchio ed empaNa •  Simulazione incarnata: quali implicazioni per la teoria della mente? Perché la scoperta dei neuroni specchio dovrebbe interessare al linguista? •  Filogenesi del linguaggio •  Ontogenesi del linguaggio •  Neuroni specchio, percezione e comprensione linguisNca –  Liv. Fonologico –  Liv. Lessicale-­‐semanNco MA PRIMA… Neuroni specchio nella scimmia: altri effeMori Cfr. Buccino et al. 2001 il sistema specchio nell’uomo non è circoscriMo alla mano Ferrari et al. 2003: “NEURONI SPECCHIO DELLA BOCCA” Purpose of the experiments: “to study the responses of F5 neurons motorically coding mouth acNons to the observaNon of mouth acNons made by another individual.” Results: •  “35% of mouth motor neurons discharged when the monkey observed mouth acNons (mouth mirror neurons).” •  “The majority of mouth mirror neurons (85%) discharged during the observaNon of ingesNve mouth acNons, others (15%) during the observaNon of communicaNve acNons.” INGESTIVE MOUTH-­‐MIRROR NEURONS •  “The funcNonal properNes of ingesNve mouth-­‐mirror neurons are very similar to those of hand mirror neurons.” –  “As hand mirror neurons, mouth mirror neurons require an interacNon between an effector and an object in order to be triggered. The presentaNon of an object alone or of a not goal-­‐directed movement is insufficient to acNvate the neurons.” –  “They show congruence between the effecNve observed and the effecNve executed acNon.” •  “these findings extend the previous concept of the mirror system as a system matching acNon observaNon and acNon execuNon from hand to mouth acNons.” COMMUNICATIVE MIRROR NEURONS •  “communicaNve mirror neurons, unlike other mirror neurons, discharge in response to acNons such as lip-­‐smacking or tongue protrusion, acNons that are not object-­‐directed.” •  “the effecNve motor acNon is not idenNcal to the effecNve observed one. All studied communicaNve mirror neurons discharged during acNve ingesNve acNons made by the monkey.” Why should ingesNon and communicaNon share a common neural substrate? Filogenesi del linguaggio Come è possibile che da tale sistema, così streMamente legato all’oggeMo, si sia sviluppato un sistema aperto capace di descrivere azioni e ogge_ senza necessariamente riferirvisi? Rizzola_ & Arbib 1998 The “observaNon/execuNon matching system provides a necessary bridge from doing to communica2ng” “The link between actor and observer becomes a link between the sender and the receiver of each message.” Filogenesi del linguaggio •  “The development of the human lateral speech circuit is a consequence of the fact that the precursor of Broca’s area was endowed, before speech appearance, with a mechanism for recognizing acNons made by others. This mechanism was the neural prerequisite for the development of interindividual communicaNon and finally of speech.” •  HP: “the mimeNc capacity inherent to F5 and Broca’s area had the potenNal to produce various types of closed systems related to the different types of motor fields present in that area (hand, mouth and larynx)” •  “the first open system to evolve en route to human speech was a manual gestural system that exploited the observaNon and execuNon matching system described earlier” •  gestural communicaNon è
vocalizaNons è
speech Filogenesi del linguaggio Neuroni specchio della bocca [Ferrari et al. 2003] HP: il sistema ingesNvo, controllato dalle aree motorie ventrali, si è evoluto nel sistema comunicaNvo •  “IngesNon and communicaNon share a common neural substrate” •  “ethological and evoluNonary data that strongly suggest that these two funcNons are strictly linked.” •  “monkey communicaNve gestures (e.g. lip-­‐smacking, lips protruded face) are ritualizaNons of ingesNve acNons that are used for affiliaNve purposes. […] In other words, the knowledge common to the communicator and the recipient of communicaNon about food and ingesNve acNon became the common ground for social communicaNon. IngesNve acNons are the basis on which communicaNon is built.” cfr. MacNeilage 1998: “human vocal communicaNon derived from the cyclic open-­‐close mandibular alternaNon originally evolved for food ingesNon.” Ontogenesi del linguaggio (Capirci et al. 2005; Stefanini et al. 2009; Congestrì et al. 2010; PeMenaN et al. 2010) Ruolo centrale del gesto nell’ontogenesi del linguaggio, sia nelle primissime fasi dello sviluppo comunicaNvo, sia nelle fasi successive. ConNnuità tra le forme linguisNche e prelinguisNche (ovvero tra azione-­‐gesto-­‐parola) “Progression from acNon to word through gesture” “There is a conNnuity between the producNon of the first acNon schemes, the first gestures and the first words produced by children. The relaNonship between gesture and words changes over Nme.” 1 anno: comunicazione intenzionale inizia mediante vocalizzazione e gesN dei_ci (“poinNng”) •  Gesto: –  ProdoMo da solo –  ProdoMo in combinazione con vocalizzazioni –  ProdoMo in combinazione con 1word-­‐uMerance • 
Cross modal combinaNon gesture/word combinaNon • 
Two-­‐word stage Gestualità negli adulN Contributo delle neuroscienze: approccio globale, integrato e mulNmodale all’analisi dei processi comunicaNvi. •  I gesN sono parte integrante del processo comunicaNvo •  Il linguaggio è un sistema integrato gesto-­‐parlato (cfr. Kendon 2004; McNeill 2000, 2005). “As a close examinaNon of the coordinaNon of gesture with speech suggests, these two forms of expression are integrated, produced together under the guidance of a single aim.” (Kendon, 2004: 2-­‐3) •  Nel linguaggio adulto i gesN sono coespressivi e sincronici rispeMo al parlato: gesN e parole, pur usando modalità differenN, sono inseparabili (“Unbreakable bond”, McNeill 2005) ed esprimono un’unica idea soMostante, ovvero sono espressioni diverse dello stesso sistema. •  Ruolo del gesto nell’acquisizione di L1 Gestualità negli adulN: case study (Gagliardi, 2014) •  Analisi della gestualità di sogge_ adulN ed anziani in un test di visual confronta2on naming di azioni (daN della taratura della baMeria SMAAV, Seman2c Memory Assessment on Ac2on verb) •  Analisi linguisNca + analisi delle produzioni gestuali degli informanN durante la somministrazione della baMeria. •  Focus sui “GesN rappresentaNvi” (“representa2onal”) ovvero gesN che forniscono una rappresentazione piMografica del significato associato ad un oggeMo o ad un evento. Denotano un preciso referente. Il contenuto semanNco di base rimane relaNvamente stabile nelle diverse situazioni. –  “Ac2on gesture” (o “enactment”): una parte del corpo compie un paMern di azioni che hanno caraMerisNche in comune con il paMern di azioni che funge da referente ; –  “size-­‐shape gesture” (o “modeling / depic2on”): il gesto richiama dimensione, forma o caraMerisNche perce_ve dell’evento o dell’oggeMo. (Ad esempio, le mani assumono una configurazione che riproduce la forma dell’oggeMo a cui il gesto si riferisce o eseguono un movimento per creare l’oggeMo nell’aria.) FINDINGS: •  In accordo con quanto è riportato in leMeratura, i significaN convogliaN da gesto e risposta vocale sono simili (match semanNco) •  Lo stroke del gesto (ovvero la parte centrale del gesto, obbligatoria, dotata di significato, in cui è concentrato lo sforzo energeNco) è prodoMo sincronicamente al parlato, con cui partecipa alla costruzione del senso degli enunciaN. •  La coespressività di gesto e risposta vocale può declinarsi in varie maniere: talvolta il gesto sembra configurarsi come espressione parallela, ridondante rispeMo al significato espresso verbalmente, mentre in altre occasioni precisa e restringe l’applicazione dell’eNcheMa lessicale. •  Sebbene in alcuni casi il gesto sembri subentrare nel momento in cui vi siano difficoltà nel recupero lessicale il rapporto tra esso e il parlato non è mai di pura compensazione. •  Probabile a_vazione somatotopica. Acquisizione ANpica: Sindrome dello SpeMro AuNsNco CARATTERISTICHE del DISTURBO: – 
– 
– 
– 
– 
– 
incapacità di relazione interpersonale mancanza di aMenzione tendenza all’isolamento evitamento dello sguardo considerazione dell’altro come un oggeMo … Gallese 2006 • 
“embodied mechanisms involving the acNvaNon of the sensory-­‐motor system seem to play a major role in social cogniNon.” • 
“all the deficits can be explained as instanNaNons of intenNonal aMunement deficits produced by defecNve embodied simulaNon, likely underpinned by a malfuncNoning of the mirror neuron systems.” Evidenze che vi sia un malfunzionamento nel sistema specchio: –  EleMroencefalografia: gli individui auNsNci non mostrano soppressione del ritmo mu durante l’osservazione delle azioni DapreMo et al. 2006 •  fRMI • 
• 
• 
10 High-­‐funcNoning children with auNsm and 10 typically developing children AIM: “to invesNgate neural acNvity during the imitaNon and observaNon of facial emoNonal expressions” STIMULI: 80 faces expressing five different emoNons: – 
– 
– 
– 
– 
• 
anger fear happiness neutrality sadness FINDINGS: “The evidence […] suggests that although both groups performed the imitaNon task as requested, the neural strategies adopted by typically developing children and those with ASD are quite different.” Reliable acNvity during imitaNon of emoNonal expressions. (a,b) AcNvity in bilateral pars opercularis of the inferior frontal gyrus is seen in the typically developing group (a) but not in the ASD group (b). A between-­‐group comparison (c) •  “Typically developing children can rely upon a right hemisphere–mirroring neural mechanism—interfacing with the limbic system via the insula— whereby the meaning of the imitated (or observed) emoNon is directly felt and hence understood. In contrast, this mirroring mechanism is seemingly not engaged in children with ASD, who must then adopt an alternaNve strategy of increased visual and motor aMenNon whereby the internally felt emoNonal significance of the imitated facial expression is probably not experienced.” ASD: Comprensione in termini cogniNvi, non esperienziali! Examina2on of “the rela2onship between ac2vity in regions with mirror neuron proper2es and symptom severity, as indexed by children’s scores on the Au2sm Diagnos2c Observa2on Schedule–Generic (ADOS-­‐G) and the Au2sm Diagnos2c Observa2on Interview–
Revised (ADI-­‐R) reliable negaNve correlaNons!!! Linguaggio nel bambino auNsNco Brandi & Bigagli 2004 “le caraMerisNche del disturbo portano a sospeMare la crucialità, anche per lo sviluppo del linguaggio, di ciò che cogniNvamente manca al bambino auNsNco: la capacità di relazione intersogge_va, la capacità di rappresentare lo stato mentale altrui, la capacità di imitare.” uno degli indicatori fondamentali della presenza del disturbo auNsNco è l’incapacità nell’esecuzione di giochi simbolici (tra 3 e 5 anni) LINGUAGGIO (Brandi 2005) “È ormai noto che l’auNsmo, oltre ad essere propriamente un deficit di Npo socio-­‐
comportamentale, porN con sé anche disturbi di caraMere streMamente linguisNco: a seconda della gravità della sindrome è possibile assistere ad un vero e proprio muNsmo, oppure ad un notevole ritardo nello sviluppo del linguaggio (talvolta le prime sillabe appaiono intorno agli oMo anni), o ancora, nel caso di uno sviluppo linguisNco tardivo, esso può manifestarsi aMraverso la produzione di stereoNpie” Disturbo complesso e di conseguenza eterogeneo per quanto riguarda la manifestazione dei sintomi. Varie tipologie di comportamento linguisNco. (vedi Brandi 2005) STEREOTIPIE: dissociazione tra forma e funzione nell’acquisizione del linguaggio è  dissociazione tra abilità sinta_co-­‐semanNca e abilità pragmaNca marcata asincronia tra lo sviluppo della funzione comunicaNva e l’acquisizione della grammaNca Sono gli aspe_ pragmaNci del linguaggio a presentarsi sistemaNcamente disturbaN nei sogge_ auNsNci Neuroni specchio e linguaggio: livello fonologico Fadiga et al. 2002 •  TMS • 
• 
Subjects were instructed to listen carefully to a sequence of acousNcally presented verbal and nonverbal sNmuli. e.g. WORDS: birra, carro, ferro, porro, terra PSEUDO-­‐WORDS: berro, furra, parro, vurro Motor-­‐ evoked potenNals (MEPs) were recorded from opponens pollicis and tongue muscles FINDINGS: •  during speech listening, there is an increase of motor-­‐evoked potenNals recorded from the listeners' tongue muscles when the presented words strongly involve, when pronounced, tongue movements. • 
when an individual listens to verbal sNmuli there is an acNvaNon of the speech related motor centres. Most interesNngly, they show also that this acNvaNon is highly specific. Watkins et al. 2003 •  TMS (Transcranial magneNc sNmulaNon) was applied to the face area of primary motor cortex to elicit motor-­‐evoked potenNals in the lip muscles. •  AIM: to examine whether auditory percepNon of speech modulated the excitability of the motor system underlying speech producNon. •  EXPERIMENTAL CONDITIONS –  (1) Speech condiNon: listening to speech (conNnuous prose) while viewing visual noise. –  (2) Non-­‐verbal condiNon: listening to non-­‐verbal sounds (e.g. glass breaking, bells ringing, guns firing) while viewing visual noise. –  (3) Lips condiNon: viewing speech-­‐related lip movements while listening to white noise. –  (4) Eyes condiNon: viewing eye and brow movements while listening to white noise. •  FINDINGS: “The results demonstrate that speech percepNon, either by listening to speech or by visual observaNon of speech-­‐related lip movements, enhanced excitability of the motor units underlying speech producNon.” SinteNzzando: •  Il sistema motorio si a_va durante percezione del linguaggio (effeMori: lingua, labbra). •  HP: Coinvolgimento del circuito dei neuroni specchio nel processing linguisNco: l’ascoltatore percepisce e decodifica i suoni linguisNci mappando l’input sul repertorio di comandi motori necessari per produrre qui suoni, che anche lui possiede. •  Simulazione incarnata della fonazione CoarNcolazione e il “problema dell’invarianza” COARTICOLAZIONE “A fundamental problem in speech percepNon is that the realizaNon of speech sounds is highly context dependent. Successive speech sounds are produced by vocal tract gestures that overlap temporally. The consequence of coarNculaNon is that there is no one-­‐to-­‐one correspondence between an acousNc event and the repertoire of phonemes or phoneNc features in the language.” “PROBLEMA DELL’INVARIANZA”: Invarianza del sistema che soggiace alla competenza linguisNca vs. variabilità del parlato. E’ comunque necessario un livello di rappresentazione fonologica? Soluzione classica: “A view that is shared by many in the field of speech percepNon is that speech is perceived by exploiNng the same auditory mechanisms that analyse other classes of environmental sounds. On the way to acNvaNng word forms in the mental lexicon (lexical access), the acousNc informaNon gives way to an intermediate input representaNon.” •  Phonemic level of representaNon •  AlternaNve “unit of percepNon” (e.g. syllabe, stress unit…) “Motor theory of speech percepNon” ALTERNATIVA RADICALE! Haskins Laboratories Liberman et al. 1967; Liberman e Ma_ngly 1985, Galantucci et al. 2006 •  PrimiNvi linguisNci: i gesN arNcolatori. •  Il linguaggio parlato viene percepito confrontando tali gesN arNcolatori con il repertorio motorio dell’ascoltatore. •  Percezione e produzione del linguaggio uNlizzano il medesimo repertorio di primiNvi motori. •  Carenza di evidenze sperimentali al momento della presentazione della teoria. La scoperta dei neuroni specchio ha portato nuovi argomenN. •  HP: A_vazione delle rappresentazioni motorie rilevanN fonologicamente. Risonanza motoria durante la percezione. Toni et al. 2008 •  “the listener does not solve the invariance problem in the auditory domain, but instead in the motor domain. The acousNc paMerns might be different, but the arNculatory gestures that are needed to produce them are the same.” •  “A listener will understand speech by virtue of being a speaker.” •  “The neuromotor commands provide the required invariance” Fadiga et al. 2002 •  “A cogniNve translaNon into phonology is not necessary because the arNculatory gestures are phonologic in nature. Furthermore, speech percepNon and speech producNon processes use a common repertoire of motor primiNves that, during speech producNon, are at the basis of arNculatory gesture generaNon, while during speech percepNon, are acNvated in the listener as the result of an acousNcally evoked motor `resonance'.” SI PUO’ FARE A MENO DI UN LIVELLO DI RAPPRESENTAZIONE FONOLOGICO? Neuroni specchio e linguaggio: livello semanNco Buccino et al. 2005 •  TMS • 
AIM: “to assess whether listening to acNon-­‐related sentences modulates the acNvity of the motor system.” • 
“By means of single-­‐pulse TMS, either the hand or the foot/leg motor area in the leq hemisphere was sNmulated in disNnct experimental sessions, while parNcipants were listening to sentences expressing hand and foot acNons. Listening to abstract content sentences served as a control. Motor evoked potenNals (MEPs) were recorded from hand and foot muscles.” • 
STIMULI: Fiqeen hand-­‐acNon-­‐related and 15 foot-­‐acNon-­‐related sentences were presented. As control sNmuli, 15 sentences with verbs expressing an abstract content were delivered. All sentences were in Italian. All acNon-­‐related sentences expressed a concrete acNon on an appropriate object (e.g., cuciva la gonna […]). All abstract content sentences expressed an abstract acNon on an appropriate object (e.g., amava la patria […]). All verbs were formed by three syllables and were conjugated in the third person of the past tense. Hand-­‐acNon-­‐related sentences: Girava la chiave, Prendeva la tazza, scriveva il tema… Foot-­‐acNon-­‐related sentences: Marciava sul posto, saltava il muro, pestava le foglie… Abstract content sentences: Soffriva il freddo, scordava la data, temeva la pena… •  Results showed that MEPs recorded from hand muscles were specifically modulated by listening to hand-­‐acNon-­‐related sentences, as were MEPs recorded from foot muscles by listening to foot-­‐acNon-­‐related sentences. Hauk et al. 2004 •  fMRI •  AIM: “The predicNon under invesNgaNon in the present study concerns possible differences between the corNcal acNvaNon paMerns elicited by acNon words of different semanNc subcategories and, more specifically, their relaNon to motor areas” •  STIMULI: “50 words from each of the three semanNc subcategories (i.e. acNon words referring to face, arm, leg acNons) were selected and presented in a passive reading task to 14 right-­‐handed volunteers, while hemodynamic acNvity was monitored using event-­‐related fMRI.” •  “To idenNfy the motor cortex in each volunteer individually, localizer scans were also performed, during which subjects had to move their leq or right foot, leq or right index finger, or tongue.” FINDINGS: •  “Our present results indicate that such acNon-­‐related acNvaNon can involve primary motor cortex and does not require a linguisNc task (e.g., naming) but is elicited by sNmulus words per se, even in a passive reading task.” •  “[…] the paMern of corNcal acNvaNon elicited by an acNon word reflects the corNcal representaNon of the acNon to which the word refers.” Esperimento replicato molteplici volte! Ad esempio Te4aman5 et al. 2005 In sintesi… Pulvermuller 2005 “Hearing a word seems to be associated with acNvaNon of its arNculatory motor program, and understanding an acNon word seems to lead to the immediate and automaNc thought of the acNon to which it refers.” “If acNon words are semanNcally related to the movements of the face or arNculators, arm or hand, or leg or foot, the distributed neuronal ensembles would include semanNc neurons in perisylvian (face-­‐related words), lateral (arm-­‐related words) or dorsal (leg-­‐related words) motor and premotor cortex. Therefore, this semanNc somatotopy model of acNon words implies that there are differently distributed networks for the English words ‘lick’, ‘pick’ and ‘kick’” Memoria SemanNca: definizione •  La memoria semanNca, o conoscenza conceMuale, è l’aspeMo della memoria umana che corrisponde alla conoscenza generale del significato delle parole e di ogge_, fa_ e persone, senza connessione ad un parNcolare tempo o luogo. “Seman2c memory is the memory necessary for the use of language. It is a mental thesaurus, organized knowledge a person possesses about words and other verbal symbols, their meanings and referents, about rela2ons among them, and about rules, formulas, and algorithms for the manipula2on of these symbols, concepts and rela2ons.” (Tulving 1972) •  Vs. Memoria Episodica •  Substrato neurale? Memoria SemanNca: correlaN neurali •  Le posizioni teoriche correnN sulla memoria semanNca condividono l’idea che gran parte del contenuto della conoscenza conceMuale sia collegata alla percezione ed all’azione, e sia dunque un network neurale distribuito, rappresentato somatotopicamente in regioni cerebrali sovrapponibili o coincidenN con le aree senso-­‐motorie •  Due visioni contrapposte della rappresentazione neuroanatomica della memoria semanNca (PaMerson et al. 2007): –  distributed-­‐only view: queste regioni cerebrali distribuite, e le connessioni neurali che le collegano, esauriscono per intero la base neurale della memoria semanNca –  distributed-­‐plus-­‐hub view: le rappresentazioni provenienN dalle aree senso-­‐motorie e linguisNche sarebbero connesse e coordinate da un “hub” amodale (o eteromodale) situato nel lobo temporale. Distribuzione neuroanatomica dei network semanNci (PaMerson et al. 2007) Classi di parole nel cervello Gli aMribuN semanNci connessi all’azione e al movimento, generalmente lessicalizzaN nei verbi, risiedono in struMure corNcali frontali, ovvero nelle aree corNcali primariamente deputate alla programmazione ed esecuzione motoria. Il processing dei nomi avviene nell’area temporale anteriore e mesiale. Però: –  La generalizzazione non sembra estendersi al lessico nominale e verbale astraMo (es. libertà, e2ca). –  La generalizzazione non sembra estendersi al linguaggio metaforico (cfr. ad esempio la review di Aziz-­‐Zadeh & Damasio 2008) –  conce_ logici (es. IF, NOT)? •  Lesioni focali e “doppie dissociazioni” La scoperta di una doppia dissociazione tra nomi e verbi come forme lessicali è stata considerata a parNre dagli anni novanta un’evidenza del faMo che la classe grammaNcale sia un principio organizzaNvo della conoscenza lessicale nel cervello (Hillis & Caramazza, 1995), rappresentata in network neurali disNnN e separaN (Damasio & Tranel, 1993). •  Ipotesi alternaNve: –  la differenza di classe lessicale emerge a livello morfologico: non sono nomi e verbi in sé ad essere elaboraN in network separaN, ma i processi morfo-­‐
sinta_ci che si applicano al lessico nominale e verbale sarebbero computaN in reN neurali disNnte (Shapiro & Caramazza, 2003; Shapiro et al., 2006) –  La dissociazione non è tanto tra nomi e verbi come classi lessicali, quanto tra parole riferite ad ogge_ e parole riferite ad azioni (Vigliocco et al. 2006, 2011) Fino a che punto è possibile generalizzare? Toni et al. 2008 •  “The discovery of mirror neurons in macaques and of a similar system in humans has provided a new and ferNle neurobiological ground for rooNng a variety of cogniNve faculNes.” •  Three claims that deal with the relaNonship between language and the motor system: –  Does language comprehension require the motor system? –  Was there an evoluNonary switch from manual gestures to speech as the primary mode of language? –  Is human communicaNon explained by automaNc sensorimotor resonances? CRITICAL REVIEW •  “We are not arguing against important links and interacNons between language and motor systems in the brain. For the semanNcs of certain word classes the acNon system might be invoked. Clearly at the level of phoneNc realizaNons the motor system plays a crucial role. This could even be in language comprehension when under condiNon of high predictability the predicted word forms might actually be produced in the form of internal speech. However, all this does not imply that the highly complicated communicaNon system of natural language can be fully reduced to sensorimotor properNes and the contribuNon of sensorimotor areas.” •  “Language goes beyond acNon. Without denying the enormous importance of the discovery of mirror neurons, their explanatory power for understanding human communicaNon is limited.”