The relationship between attention and consciousness: the brain-body dynamic

Resumo

Our environment contains large amounts of information, which gives us the impression of perceiving perceptual scenes that are rich in detail. However, when it comes to describing or reporting specific information, our ability to do so is more limited. This raises the question of whether perceptual consciousness is rich or limited. The answer to this question has prompted an important debate, along with many other unresolved issues related to the study of consciousness. Block (2011) proposed a classification of perceptual consciousness into access consciousness and phenomenological consciousness. Access consciousness has a limited capacity, allowing us to report only a few items at a time. In contrast, phenomenological consciousness involves a subjectively rich experience of the environment, which can sometimes contain erroneous information. Attention plays a crucial role facilitating access consciousness or creating perceptual experiences (Baars, 1997). Although numerous studies have demonstrated the fundamental role of attention in consciousness, not all types of attention produce comparable effects. Different theories discuss the role of attention in conscious processing. For example, Dehaene and Changeux's (2011) Global Workspace Theory suggests that attention is a prerequisite for perceptual consciousness, although attention is insufficient to produce a conscious experience. Other theories, such as Lamme and Roelfsema's Recurrent Theory (2000), emphasize the need for feedforward and feedback communications between primarily sensory regions for gaining consciousness, with attention possibly playing a collaborative role in the process. These theories theorize about how activity in the central nervous system enables conscious experience. However, the subjective neural framework approach proposed by Park and Tallon-Baudry (2014) emphasizes the importance of the interaction between the state of the organism and the brain for conscious processing, which, by definition, takes place from a first-person perspective (I see). This ongoing debates, concerning the necessity of attention and the role of brain-body communication, has inspired the questions and studies that constitute this dissertation. The main goal of this thesis was to explore the interactions between attention and perceptual consciousness, as well as to investigate this relationship in terms of brain-body modulations. In our studies, brain dynamics were measured throughout brain oscillations, while body dynamics were examined using measures of the peripheral nervous system, such as heart rate. To achieve these goals, four studies were conducted to analyze how different attentional processes interact, or not, with phenomenological and access consciousness. One of these studies examines brain dynamics in a feature integration task (used as a measure of phenomenological consciousness), while two studies investigate peripheral nervous system activity, specifically heart rate measures, in tasks related to both access and phenomenological consciousness (feature integration). The first experimental study (Chapter 6) of this thesis explores the relationship between phasic alerting and access consciousness, as well as their modulations in heart rate. Participants were required to detect the presence of a stimulus at the threshold of consciousness, which could be preceded (in 50% of trials) by an alerting signal. In the second study (Chapter 7), a new experimental line was developed to explore phenomenological consciousness using a feature integration paradigm. Participants were briefly presented with a string of characters of different shapes and colors (e.g., 8OL8). Their goal was to report the color of the letter L. According to the example given, if participants answered "green", the trial was considered a hit (correct integration of shape and color features); if they answered "blue", the trial was considered a perceptual illusion (integration error produced by using the color of the distractor); and if they answered "red", a color that was not presented on screen, the trial was considered an error. Perceptual illusions are a useful tool that allows the study of phenomenological consciousness, because when they occur, the subjective experience is rich, but has been produced erroneously. In addition, this study was composed of 3 different experiments in which attention was manipulated prior to the presentation of the target stimulus. Following Posner and Petersen's (2012) classification, the executive system (divided attention), the endogenous orienting system, and the exogenous orienting system were manipulated. In Experiments 2 and 3 of this study, an expectancy manipulation was included at the end of the experiment by unexpectedly presenting the target stimulus in an unexpected color (white). In the third study (Chapter 8) the feature integration paradigm was used in order to explore brain dynamics in different frequency bands related to correct or incorrect feature integration. Since previous studies had concentrated solely on a single frequency, the objective of this study was to broaden the exploration of the brain oscillations that distinguish between correct and incorrect subjective experiences. Finally, the fourth study (Chapter 9) explored the relationship between phasic alerting and phenomenological consciousness, as well as their modulations in heart rate. Using the same paradigm as in Chapters 7 and 8, we presented an alerting tone in half of the trials before the target stimulus was presented while measuring the participants' cardiac response. Overall, the results of this thesis have shown that phasic alerting enhances access consciousness, but not phenomenological consciousness (as measured by the ability to integrate features). In the case of access consciousness, previous studies have shown improvements in conscious detection by attentional orienting (especially exogenous, Chica & Bartolomeo, 2012), and less consistent modulation by executive attention (Colás et al., 2017; Martín-Signes et al., 2018). In phenomenological consciousness, we have found clear modulations by attentional orienting, but not by executive attention. Furthermore, expectancy violations clearly influenced the feature integration process. Results on brain dynamics showed that phenomenologically represented information depends on preparatory processes (early alpha), distractor inhibition (late alpha), and a reliable representation of information (late alpha and beta). Finally, the results of peripheral measures, in particular heart rate, show clear modulations of this peripheral system both when we access consciousness and when we integrate features, although the modulatory pattern is very different depending on the type of consciousness. In conclusion, this doctoral thesis highlights the need to explore the relationship between attention and consciousness using measures of the central and peripheral nervous system. Studying the behavior of both systems allows us to emphasize the importance of the communication between the brain and the organism during perceptual consciousness, as well as to incorporate this aspect into future models that attempt to explain consciousness