Blinking is a rapid closing and opening of the eyelid. Eye blinks with identical kinematical features can have different origins and meanings. For example, one can blink automatically, due to a simple reflex arc – such as when moistening the cornea – or one can blink voluntarily to communicate a fundamental message – such as when a locked-in patient communicates that he/she is happy or frustrated (Laureys, et al., 2005) The main aim of the present project is to find a brain-based objective way to know whether a given blink is a meaningless automatic neural event or the endpoint of a complex conscious process. The proposal builds up on the empirical work by Kornhuber & Deecke and Benjamin Libet, who showed that the awareness of intention to move is preceded by a recordable cerebral activity called “Readiness Potential”. The present proposal is relevant for two reasons: 1. In healthy subjects, automatic blinking occurs spontaneously every 5 seconds, or so. At the same time, healthy subjects can be instructed to blink voluntarily in a controlled fashion. In this way, blinking offers the ideal contrast between unconscious and conscious acts – the physical, kinematic aspects of the movement being equal. In this perspective, analyzing brain activity prior to automatic and voluntary blinks may offer a unique insight on the neural correlates of a conscious act. 2. In patients with severe brain injuries blinking is often the only motor act that can be reliably detected. By employing operant conditioning, we aim at training patients on the association between a specific eyelid closure and a positive reinforcement. Specifically, Readiness Potential like activity will be computed on the cortical activity preceding eye blinking as a measure of “volition,” first in healthy controls and then in vegetative and minimally conscious state patients undergoing operant conditioning. In healthy controls, we will contrast spontaneous blinks against voluntary blinks. The results of this experiment are meant to explore the dynamic range of the changes in brain activity that underlies voluntary vs. spontaneous blinks in controlled conditions. In patients, detecting a progressive increase in the strength or complexity of brain activity (up to the levels obtained in healthy subjects during voluntary blinks) during the course of the conditioning sessions will indicate that their blinking might reflect a voluntary act. Ultimately, this project, if successful, will link operant conditioning to the long-standing topic of the neural substrates of a wilful decision to act, bearing important scientific/ethical implications. The novelty of this project rests on: a. Exploring, empirically, the relationships between brain activity and the will. The underlying hypothesis guiding this project is that a wilful act should be reflected, to some measurable degree, in high levels of anticipatory brain dynamics. b. Taking Libet’s work one-step forward, by using slow cortical potentials such as the “Readiness Potential” as a neural marker of volition. c. Using the “Readiness Potential” to distinguish between spontaneous and voluntary blinks. d. Answering the critical question of whether the blinks produced by vegetative patients after a conditioning protocol are voluntary or not.
Il “blink” o “batter d’occhi” è un movimento di rapida chiusura e riapertura delle palpebre. Il “blink” può essere un movimento spontaneo, riflesso o volontario. “Blink” con identiche caratteristiche cinematiche possono avere differenti origini e significati. Per esempio, un blink può essere spontaneo quando ha la funzione fisiologica di creare un film lacrimale evitando la seccazione della cornea, può essere riflesso in riposta a stimoli esterni ed infine può essere volontario per comunicare un messaggio attraverso un canale comunicativo preservato, per esempio quando un paziente locked in cerca di comunicare gioia, accordo o disaccordo, frustrazione attraverso gli occhi (Laureys et al., 2005). Lo scopo principale di questo studio è stato quello di trovare una misura oggettiva relativa alla distinzione tra un blink spontaneo e uno volontario: il “potenziale di preparazione” (Readiness Potential). Il presente studio è quindi rilevante per due ragioni: 1. Nei soggetti sani, i blink spontanei appaiono con una frequenza di circa 1 ogni 5 secondi. Allo stesso tempo, i soggetti sani possono “controllare” il movimento spontaneo e riprodurlo in maniera intenzionale se opportunamente istruiti. In questo modo, il “blink” o “ammiccamento oculare” offre un contrasto ideale tra atto conscio e inconscio, a parità di cinematica. In questa prospettiva, l’analisi dell’attività cerebrale che precede un atto spontaneo o automatico messa a confronto con l’attività che precedere un “blink” volontario può offrire uno sguardo unico sui correlati neurali di un atto cosciente. 2. Nei pazienti con gravi cerebrolesioni, il “blink” è spesso l’unico atto motorio che può essere individuato. È infatti impossibile per molti pazienti effettuare movimenti più complessi. Per questo motivo, attraverso un condizionamento operante in cui ad uno specifico comportamento viene associato un rinforzo positivo, il nostro scopo è quello di indirizzare i pazienti ad associare un determinato tipo di “blink”, opportunamente selezionato, con un rinforzo positivo rappresentato da voci familiari/amiche che si suppone possano avere una valenza emotiva positiva per il paziente. Nella prima parte della tesi verranno introdotte le premesse teorico/sperimentali alla base dello studio e verranno presentati i materiali e metodi e i risultati relativi alla popolazione di controllo (soggetti sani). Nella seconda parte, verrà introdotto il “disturbo di coscienza” dal punto di vista clinico, il nuovo protocollo sperimentale applicato ai pazienti con disturbo di coscienza e i risultati preliminari. In conclusione, verranno valutate le potenzialità dello studio da un punto di vista teorico, da un punto di vista clinico/riabilitativo ed infine da un punto di vista etico.
BEHIND AN EYE BLINK: A NEW EMPIRICAL PERSPECTIVE ON INTENTIONAL ACTION / C.c. Derchi ; supervisors:M. Massimini, S. Casarotto. DIPARTIMENTO DI SCIENZE BIOMEDICHE E CLINICHE "L. SACCO", 2018 Mar 06. 30. ciclo, Anno Accademico 2017. [10.13130/derchi-chiara-camilla_phd2018-03-06].
BEHIND AN EYE BLINK: A NEW EMPIRICAL PERSPECTIVE ON INTENTIONAL ACTION
C.C. Derchi
2018
Abstract
Blinking is a rapid closing and opening of the eyelid. Eye blinks with identical kinematical features can have different origins and meanings. For example, one can blink automatically, due to a simple reflex arc – such as when moistening the cornea – or one can blink voluntarily to communicate a fundamental message – such as when a locked-in patient communicates that he/she is happy or frustrated (Laureys, et al., 2005) The main aim of the present project is to find a brain-based objective way to know whether a given blink is a meaningless automatic neural event or the endpoint of a complex conscious process. The proposal builds up on the empirical work by Kornhuber & Deecke and Benjamin Libet, who showed that the awareness of intention to move is preceded by a recordable cerebral activity called “Readiness Potential”. The present proposal is relevant for two reasons: 1. In healthy subjects, automatic blinking occurs spontaneously every 5 seconds, or so. At the same time, healthy subjects can be instructed to blink voluntarily in a controlled fashion. In this way, blinking offers the ideal contrast between unconscious and conscious acts – the physical, kinematic aspects of the movement being equal. In this perspective, analyzing brain activity prior to automatic and voluntary blinks may offer a unique insight on the neural correlates of a conscious act. 2. In patients with severe brain injuries blinking is often the only motor act that can be reliably detected. By employing operant conditioning, we aim at training patients on the association between a specific eyelid closure and a positive reinforcement. Specifically, Readiness Potential like activity will be computed on the cortical activity preceding eye blinking as a measure of “volition,” first in healthy controls and then in vegetative and minimally conscious state patients undergoing operant conditioning. In healthy controls, we will contrast spontaneous blinks against voluntary blinks. The results of this experiment are meant to explore the dynamic range of the changes in brain activity that underlies voluntary vs. spontaneous blinks in controlled conditions. In patients, detecting a progressive increase in the strength or complexity of brain activity (up to the levels obtained in healthy subjects during voluntary blinks) during the course of the conditioning sessions will indicate that their blinking might reflect a voluntary act. Ultimately, this project, if successful, will link operant conditioning to the long-standing topic of the neural substrates of a wilful decision to act, bearing important scientific/ethical implications. The novelty of this project rests on: a. Exploring, empirically, the relationships between brain activity and the will. The underlying hypothesis guiding this project is that a wilful act should be reflected, to some measurable degree, in high levels of anticipatory brain dynamics. b. Taking Libet’s work one-step forward, by using slow cortical potentials such as the “Readiness Potential” as a neural marker of volition. c. Using the “Readiness Potential” to distinguish between spontaneous and voluntary blinks. d. Answering the critical question of whether the blinks produced by vegetative patients after a conditioning protocol are voluntary or not.File | Dimensione | Formato | |
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