Semantically reversible sentences, i.e., sentences wherein both characters can potentially perform the given action, have long been used to understand the various mechanisms involved in successful sentence comprehension. Over the decades, studies have established that sentences with non-canonical word-orders such as passive voice sentences are more difficult to process than canonical counterparts such as active voice sentences using psycholinguistic, neuroimaging, lesion-based, and more recently transcranial brain stimulation methods such as transcranial magnetic stimulation (TMS). In addition to understanding the cognitive processes involved, these studies have also attempted to uncover the underlying neural correlates. Various parts of the frontal, temporal, and parietal lobes have been thought to be critical for different functions. In the recent years, the parietal regions have garnered considerable attention. In particular, various studies have found the intraparietal sulcus (IPS) to be involved in the comprehension of semantically reversible sentences, particularly when they have non-canonical word-orders. In this thesis, I attempted to build on this literature and further understand the role of the IPS in sentence comprehension. More specifically I followed-up on two TMS studies by Finocchiaro and colleagues that looked at reversible Italian active and passive sentences. Online repetitive TMS (rTMS) to the posterior portion of the left IPS (henceforth, l-pIPS) affected only the processing of passive sentences in both experiments. In fact, one of the studies also found an effect on ‘passive’ pseudosentences, thus, prompting the authors to suggest that the l-pIPS affects passive sentences irrespective of semantic meaningfulness. The authors concluded that this region is likely to be involved in sentence comprehension, particularly at the stage where thematic reanalysis, i.e., a revision of the initially ascribed thematic roles, occurs. However, these studies were unable to discern if these effects were seen on reversible passives due to their reversibility, passive voice, or the non-canonical word-order seen in passive sentences. They also raised questions regarding whether the region is important in processing only thematic reversibility or is also involved in comprehending reversible sentences without thematic roles (e.g., comparative sentences). I ran three experiments to better understand these factors. In Chapter 1 I summarise the literature on the comprehension of reversible sentences. I discuss findings from behavioural, lesion-based, neuroimaging, and TMS studies that have formed the basis of the current thesis. I conclude by bringing to attention some of the questions raised by these studies that I have attempted to answer in the subsequent chapters. In Chapter 2 I attempted to understand the role of passive voice and reversibility in reanalysis and sentence comprehension. To do this I used a sentence comprehension task while administering online rTMS to the l-pIPS. Participants performed a forced-choice task where they were required to read reversible and irreversible Italian active and passive voice sentences and identify either the agent or the theme in alternate blocks. The experiment showed an effect of rTMS only on reversible passive sentences. While these results are in line with the previous studies, they also draw attention to a critical aspect of comprehension of passive voice sentences. They suggest that passive voice in itself may be insufficient to trigger reanalysis. Instead, it is likely that reanalysis is triggered by the co-occurrence of numerous factors such as voice and reversibility. However, as with the previous studies, this study still does not clarify the role of non-canonical word-order or passive voice per se. In an attempt to distinguish between the two, I ran an rTMS experiment with a sentence-picture verification task in Chapter 3. The experiment used reversible active and passive voice sentences in Hindi. The advantage that Hindi offers in this regard is that both actives and passives are typically presented in the agent-theme-action order. Consequently, such passives may not require the reassigning of originally established thematic roles. Stimulation to the l-pIPS showed no effects on these actives or passives. Interestingly, these null results serve as supporting evidence (albeit, weak) that non-canonical word-order may be essential for thematic reanalysis. If passive voice alone, or even a combination of passive voice and reversibility were sufficient to engender reanalysis, stimulation should have had effects on the passives even in the absence of a non-canonical word-order (as seen in the stimuli of this experiment). Finally, I attempted to understand if the region was involved only in comprehending reversible sentences with thematic role assignment, or also played a role in reversible sentences without thematic role assignment such as comparative sentences (where one of the two characters is the owner of a given property/feature). To do this, I ran the final rTMS experiment reported in Chapter 4. Participants received online stimulation to the l-pIPS while performing a sentence-picture verification task. The stimuli sentences consisted of reversible Italian declarative active and passive sentences, and comparative of majority or minority sentences. Comparatives were used because unlike Italian actives and passives, both types of comparatives are identical in word-order and other morphosyntactic features. In an attempt to maintain the visual complexity across stimuli pictures, same pictures were used to depict the relationships in both declarative and comparative sentences. The results of this study are rather puzzling. Unlike previous studies no effects were found on passive sentences. In terms of the comparative sentences, a selective effect was seen on the ‘easier’ comparatives of majority. These results call into question previous findings which have found an effect on the more ‘difficult’ sentence type, i.e., the passives. The effect of TMS on the comparatives of majority indicates the involvement of the l-pIPS in sentence comprehension yet again. However, these results to do not clarify what specific features of a sentence the l-pIPS helps comprehend. Moreover, given the consistent effect of rTMS on reversible Italian passives in the previous experiments, and the effect on comparatives of majority, it is possible that the current results may have been confounded by the use of complex stimuli. Coupled with the findings from the Finocchiaro studies, this thesis establishes the role of the l-pIPS in sentence comprehension. In particular, the results of the two Finocchiaro studies and Chapter 2 suggest that the co-occurrence of passive voice and reversibility is essential for reanalysis. While the results of Chapter 3 concur with these findings, they also strongly indicate that these features must co-occur with a third factor, namely a non-canonical word-order, to trigger reanalysis. Lastly, the results of Chapter 4 clarify the l-pIPS’ involvement in sentence comprehension. However, it leaves the exact role of the l-pIPS unclear in comprehending reversible sentences without thematic role assignment. The current thesis has advanced our understanding of some key factors responsible for reanalysis, and its neural correlates. Future studies can aim to understand these factors better by exploiting parallel versions of the same sentence type, and by studying different sentence types in isolation. For example, Hindi passives can be presented in both agent-theme-action and theme-agent-action word-orders. Contrasting such versions may help answer questions pertaining to word-order. On the other hand, studying sentences like declaratives and comparatives in separate experiments or even separate sessions may help simplify stimuli, thereby giving us clearer results.

<p>The ultimate goal of the nervous systems of all animals is conceptually simple: Manipulate the external environment to maximize one's own survival and reproduction. The myriad means animals employ in pursuit of this goal are astoundingly complex, but constrained by common factors. For example, to ensure survival, all animals must acquire the necessary nutrients to sustain metabolism. Similarly, social interaction of some form is necessary for mating and reproduction. For some animals, the required social interaction goes far beyond that necessary for mating. Humans and many other primates exist in complex social environments, the navigation of which are essential for adaptive behavior. This dissertation is concerned with processes of transforming sensory stimuli regarding both nutritive and social information into motor commands pursuant to the goals of survival and reproduction. Specifically, this dissertation deals with these processes in the rhesus macaque. Using a task in which monkeys make decisions simultaneously weighing outcomes of fruit juices and images of familiar conspecifics, I have examined the neurophysiology of social and nutritive factors as they contribute to choice behavior; with the ultimate goal of understanding how these disparate factors are weighed against each other and combined to produce coherent motor commands that result in adaptive social interactions and the successful procurement of resources. I began my investigation in the lateral intraparietal cortex, a well-studied area of the primate brain implicated in visual attention, oculomotor planning and control, and reward processing. My findings indicate the lateral intraparietal cortex represents social and nutritive reward information in a common neural currency. That is, the summed value of social and nutritive outcomes is proportional to the firing rates of parietal neurons. I continued my investigation in the striatum, a large and functionally diverse subcortical nuclei implicated in motor processing, reward processing and learning. Here I find a different pattern of results. Striatal neurons generally encoded information about either social outcome or juice rewards, but not both, with a medial or lateral bias in the location of social or juice information encoding neurons, respectively. In further contrast to the lateral intraparietal cortex, the firing rates of striatal neurons coding social and nutritive outcome information is heterogeneous and not directly related to the value of the outcome. This dissertation represents a few incremental steps toward understanding how social information and the drive toward social interaction are incorporated with other motivators to influence behavior. Understanding this process is a necessary step for elucidating, treating, and preventing pathologies</p> / Dissertation

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18124号 / 医博第3844号 / 新制||医||1001(附属図書館) / 30982 / 京都大学大学院医学研究科医学専攻 / (主査)教授 金子 武嗣, 教授 大森 治紀, 教授 渡邉 大 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

<p>To solicit the attention or determine the intentions of another, we use our eyes. While many animals appear to use eyes as an important behavioral cue, for humans, these cues are especially critical. The power of the eyes to attract and direct attention shapes human behavior from an early age and likely serves as a foundation for social skill acquisition, ranging from simple, friendly eye contact to complex, spoken language, even to our almost mystical ability to empathize and "see the world through another's eyes". Humans have transformed our environment through our economic alliances and military competitions, and our individual successes and failures depend critically on social skills built on a foundation of shared attention. When these abilities break down, as in autism, pervasive social awkwardness can challenge the close relationship of individuals with their friends, family, and community. Nonetheless, we know almost nothing about the brain mechanisms that have evolved to process social cues and convert them into a rich experience of shared attention. To investigate this process, we explored the ability of human and nonhuman primates to follow the attention of other individuals. First, we characterized natural gaze-following behavior using a novel telemetric device in socially-interacting prosimian primates, and later in monkeys and humans responding to gaze cues in the lab. Finally, we examined the neuronal responses to gaze cues in a macaque posterior parietal area implicated in attention control--the lateral intraparietal area, LIP. Our findings suggest that gaze-following abilities may be widespread in social primates, relying on conserved, homologous brain pathways; and that they may not be informationally-encapsulated reflexes, but rather are densely interwoven with diverse social processes. Indeed, we found gaze cues influenced neurons in LIP, part of the dorsal frontoparietal attention network. Finally, we report that "mirror" neurons in parietal areas may thus play a role not only in representing perceived bodily actions, but also perceived mental states such as observed attention.</p> / Dissertation

Regarder ou saisir un objet constituent, à première vue, des actes simples et triviaux. De tels mouvements nécessitent, entre autres, l’existence de complexes processus entre entrées sensorielles et sorties motrices afin de compenser l’effet de la variabilité sensorimotrice inhérente au système. Un concept clé décrit ces processus de contrôle : les modèles internes. Il s’agit de représentations dynamiques de l’état de nos appareils sensorimoteurs, inscrites au sein d’un réseau d’aires cérébrales, permettant la comparaison entre un mouvement désiré (parfait) et le mouvement réalisé (bruité). Lorsqu’une différence est perçue suite à cette comparaison, un signal d’erreur motrice (EM) serait envoyé afin d’ajuster le mouvement en cours d’exécution. Nous avons réalisé une première étude chez l’Homme afin de définir le rôle des modèles internes lors d’un acte sensorimoteur simple: la saccade oculaire. Une tâche originale nous a permis d’introduire du bruit moteur artificiel (saut de cible intrasaccadique) durant une séquence saccadique. Les résultats valident l’existence d’un mécanisme de contrôle sensorimoteur optimal et confirme la prédiction d’un modèle basé sur la théorie des filtres de Kalman, pondérant la «confiance» accordée aux mouvements désirés versus réalisés en fonction de leur fiabilité (l’inverse de leur variance). Nous nous sommes alors attachés à rechercher les substrats cérébraux du calcul de l’EM en adaptant nos paradigmes chez le macaque rhésus. Nous avons enregistré l’activité électrophysiologique neuronale unitaire puis réalisé des inactivations réversibles au sein de l’aire latérale intrapariétale (LIP), région clé pour l’intégration visuo-saccadique. Nos résultats suggèrent que le cortex pariétal serait impliqué dans l’ajustement moteur du système saccadique. Le cortex pariètal pourrait ainsi accumuler des évidences (signaux d’erreur donnés par la copie d’efférence et les retours sensoriels) quant à la présence d’erreur oculomotrice puis inciter le reste du réseau saccadique à corriger cette dernière. Ce mécanisme permettrait alors d’optimiser la plupart des actions motrices réalisées dans des contextes sensorimoteurs constamment bruités / Looking at or grasping an object are simple and trivial actions. However, these types of movements require complex processing of sensory and motor information in order to compensate for the natural variability within the sensorimotor system. A key concept describes these control processes: internal models. These models are dynamical representations of the state of our effectors, supported by a network of cerebral areas, which allow the comparison between the desired movement (perfect) and the realised movement (noisy). When a difference is perceived, a motor error (ME) signal is sent in order to adjust the ongoing movement. We performed a first study with human subjects to define the role of internal models during a simple sensorimotor action: a saccade. We developed an original task in order to introduce artificial motor noise (intrasaccadic target jump) during a sequence of saccades. These results validates the existence of an optimal sensorimotor control mechanism and confirms the predictions of a model based on the Kalman filter theory. This optimal control implies a balance between the reliability given to the desired movements versus the executed movements as a function of their uncertaincy (correlate to their variability). We then investigated the neural substrates of the ME estimation by adapting our protocols for use with rhesus monkeys. We recorded the electrophysiological activity of unitary neurons and performed reversible inactivations in the lateral intraparietal area (LIP), a key area for visuo-saccadic integration. Our results suggest, therefore, that the parietal cortex plays a role in the motor adjustment of the saccadic system. We postulate that parietal cortex could accumulate evidence (i.e. error signal given by efferent copy and sensorial feedback) on the necessity to perform a corrective saccade. When the amount of evidence exceeds an error threshold, the decision to trigger a correction could be made. This process could allow the optimization of these motor actions within noisy sensorimotor context

L’attention visuelle est un phénomène primordial pour la perception visuelle de notre environnement. Elle correspond à l’ensemble des mécanismes qui permettent la sélection d’information visuelle dans le but de la traiter en particulier. Lorsque volontaire, son orientation est considérée comme lente, contrairement à l’orientation de l’attention visuelle involontaire, qui est rapide et réflexive. Grâce à une étude de psychophysique humaine, nous montrons que le déplacement volontaire de l’attention est rapide mais qu’un ensemble de processus cognitifs ont jusqu’à présent masquer ce phénomène.Au niveau cérébral, l’orientation de l’attention visuelle est sous tendue par un réseau d’aires,impliquant le champ oculomoteur frontal (FEF) et l’aire latérale intrapariétale (LIP). En enregistrant l’activité unitaire des neurones de ces 2 aires de 2 macaques Rhésus impliqués dans une tâche de détection de cible nécessitant l’orientation volontaire de l’attention visuelle,nous montrons que ces 2 aires jouent un rôle différent. Ainsi FEF semble impliqué dans l’orientation des capacités attentionnellles et représente également la sélection de l’objet important. LIP n’est pas impliqué dans l’orientation de l’attention visuelle, en revanche, ses neurones présentent une réponse cognitive spécifique de la détection de la cible. Nos résultats suggèrent que FEF contrôle l’orientation volontaire de l’attention visuelle alors que LIP sert à la détection de la cible.Qui plus est, nous montrons l’existence dans FEF d’une nouvelle classe de cellules impliqués dans le contrôle exécutif des fonctions cognitives et notamment attentionnelles / Visual attention is a critical process to a correct perception of our visual environment.This term includes all mechanisms involved in the selection of information in order to processit in priority. It is generally proposed that voluntary orientation of attentional capacity is a220slow and sustained process, while unvoluntary orientation is fast. We show here by apsychophysical study that voluntary orientation is in fact a rapid process that is easely maskedby others cognitiv process of general engagement.This phenomenon is sustained by a large network of cerebral areas, including the Frontal Eye Field (FEF), and the Lateral IntraParietal area (LIP). We recorded neuronal activity of 2monkey’s FEF and LIP neuronal activity while they were engaged in a attentional task. Weshow here that these 2 areas play 2 crucial differents roles. Contrary to FEF, that is highlyinvolved in attentional orientation and engagement, LIP neuronal activity present few attentional modulations. LIP and FEF cells present large cognitive activities selectives to selection of the important event of the task. We hypothesis that FEF controles the voluntary orientation of visual attention while LIP detects the target.More over, we highly the existence of a new FEF’s cell category involved in the executive control of cognitives function (as attentional).

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