Browsing by Subject "Default mode network"

Anhedonia refers to the loss of motivation to engage in previously enjoyable activities. While anhedonia is most often characterized as a symptom of psychiatric disorders such as depression, schizophrenia, and post-traumatic stress disorder, it can also present on its own. In spite of this, it is typically overlooked as a primary focus of research studies due to limitations inherent to our current diagnostic system. Therefore, no targeted treatments for anhedonia exist despite the significant impairment it causes. Moreover, very few studies to date have explored underlying neuropsychological characteristics of anhedonia, which is essential to the development of effective treatments for this clinical target. Because anhedonia is a core clinical target spanning many disorders as well as existing as its own disorder, transdiagnostic treatment approaches are of critical scientific importance to improve population mental health.The present study addresses this gap in the literature by taking a graph theoretical approach to characterizing state-based (i.e., reward anticipation, rest) network dynamics in a transdiagnostic sample of adults with clinically significant anhedonia (n = 77). Analyses focused on three canonical brain networks: the Salience Network (SN), the Default Mode Network (DMN) and the Central Executive Network (CEN). Owing to the direct inputs from reward-related regions to the SN, hypotheses centered on anhedonia relating to deficits in connectivity within the SN, as well as between the SN and the other networks. Two models were tested. First, a multiple linear regression assessed to what extent connectivity within the SN, as well as between the SN and the other two networks (i.e., CEN, DMN) during reward anticipation related to anhedonic symptoms. To build on these findings and assess dynamic state changes as they relate to anhedonia, a second multiple linear regression explored whether the magnitude of topographical reorganization that took place within the SN as well as between the SN and the other two networks predicted anhedonic severity in this sample. Contrary to hypotheses, neither connectivity within the SN or between the SN and the CEN or DMN during reward anticipation, nor reorganization within the SN or between the SN and the CEN or DMN when transitioning from rest to reward anticipation were associated with anhedonia severity in this sample. Exploratory analyses looked beyond the SN and found a significant association between anhedonia severity and DMN reorganization from rest to reward anticipation. Specifically, greater anhedonia severity was associated with less reorganization in response to reward anticipation. This finding suggests that anhedonia may be associated with DMN hyposensitivity, such that individuals with more severe anhedonia may have a difficult time disengaging from their internal world in the context of potentially rewarding experiences. Very little is known about the internal experience of anhedonia, and future work should focus on examining what internal thought processes these individuals may be having difficulty disengaging from. Nonetheless, an impaired ability to attend to the external world when potential reinforcers are present can prevent individuals from coming into contact with rewarding experiences in their environments and be a key maintaining factor of anhedonia. Although preliminary, these findings challenges the centrality of the SN in anhedonia and suggests the importance of the DMN. Future studies should aim to replicate this finding and explore potential clinical implications. Specifically, treatments that foster the ability to flexibility redirect attention to the present moment, such as mindfulness-based cognitive therapies, or non-invasive neuromodulatory therapies that target the DMN, may be particularly promising interventions for anhedonia.

It has been suggested that primate brains are inherently biased towards gathering and processing the social information present in the world. In fact, the neural network that mediates our engagement with the external world - the default mode network (DMN) ¬- is strongly convergent with the neural circuitry for social cognition. The posterior cingulate (PCC) is believed to be a key node in both the DMN and in social cognition. Human and non-human primate studies have demonstrated a role for the PCC in outcome monitoring: it tracks rewards, subjective values of choices, task engagement and global choice strategies. It is also implicated in social cognition. Human studies show that PCC activity varies with the recall of autobiographical memories and exposure to social stimuli. While several electrophysiological studies explicate the response of PCC neurons to non-social outcome monitoring and valuation, there is a lack of similar studies for social valuation. This thesis is concerned with characterizing the neuronal responses in the PCC to social stimuli and determining whether social valuation occurs in the PCC in a manner similar to that previously described for non-social outcomes. I recorded the single unit activity of neurons in the PCC of rhesus macaques while they performed behavioral tasks that required attending to the faces of high-status or low-status individuals. Monkeys valued the faces of high-status individuals more than low-status individuals, though they were equally likely to identity and overtly attend to faces of both social classes. This differential valuation of face stimuli was represented in the firing activity of PCC neurons, with higher neuronal activity seen in response to subordinate faces as compared to dominant ones. Cells in the PCC did not track the individual identity of the presented faces. Furthermore, neuronal activity in the PCC predominantly tracked social value, and not non-social reward delivery as previously reported. Neuronal activity also predicted task engagement, with higher firing rates being predictive of a decrease in task engagement. To summarize, the PCC is biased towards social information processing, and neuronal activity in the PCC tracks social category information and the level of task engagement.

The structure of this dissertation comprises an introduction and four chapters, which contain three original musical compositions and one article. The first composition is a piece for wind symphony, the second one works with a string quartet, and the third explores the bass clarinet and electronics combination. The article comprises research on musical composition creativity and its pedagogical possibilities.

Chapter 1, “To Pernambuco with Love for Wind Symphony,” is a three-movement composition written as a tribute to the people of Pernambuco, one of the most musical and creative Brazilian states. During its 18 minutes, the piece explores some regional genres, such as the traditional Frevo and Maracatú, as well as the contemporary Maguebeat style. The first movement addresses the historical development of Frevo “Fanfarras” and “Orquestras,” which are musical ensemble sculpted in the roots of Pernambucan culture. The second movement still deals with Frevo. It starts with a percussion interlude, very common during frevo parades, followed by another particular manifestation of this genre: the clash of the bands. Different bands start to parade at different places in Pernambuco, in particular in its capital, Recife, and a surrounding city, Olinda. Eventually, some of those bands cross each other and start a beautiful sound battle to entice the people who were following the other band. Finally, the third movement expresses my personal admiration for Maracatú and Manguebeat. The former, a genre strongly connected with its Afro-Brazilian roots with a very characteristic complex percussive pattern. The latter, a genre born in the 1990s which expresses very well how people in Brazil cope with cultural globalization: they adjust any international cultural commodity to Brazilian unique flavors and roots.

The chapter 2, “String Quartet No. 1,” is a 19-minute piece that explores the traditional instrumentation of this ensemble with non-traditional musical material. Thus, the sonic result of the use of the digital delay effect inspires the first movement of this piece. Although there was no used resource other than the traditional instruments, the piece intends to emulate this and other effects acoustically. It works as a kind of stylized canon, with different dynamic layers. The second movement explores the sonorities derived from the amplitude modulation and frequency modulation synthesis. The complex harmonic result of such manipulations leads the group to represent it in complex chords with quarter-tone intervals. The last movement explores a Brazilian marginalized urban musical genre called Funk Carioca. It is inspired by the rhythmic and overall sonic quality of the genre, which encompasses some characteristic sounds provided by analogic drum machines that are represented by the string quartet instruments.

Chapter 3 presents the piece “Maco Light,” a piece for bass clarinet and prerecorded electronics that lasts exactly 7 minutes and 41 seconds. This piece is named after a North Carolinian legend originated in 1867. The railroad conductor Joe Baldwin died in a tragic train accident. Few weeks after this event people started to see apparitions of mysterious lights close to where the accident happened, the Maco station. This phenomenon, real or not, was reported dozens of times until the 1970s when Maco station was closed. Thus, this piece explores this story and uses the electronics to manipulate train sounds that engage in constant dialogue with the bass clarinet and with the story behind the music.

In chapter 4, the article “Educating for Composition Creativity” exposes how musical improvisation skills can be beneficial to the development of creative compositional strategies. It argues that improvisation should be part of the composition curriculum for college students and a particular subject in composition textbooks. Through an intense literature review in the fields of Neuroscience, Psychology, and Composition Pedagogy, this chapter makes evident that improvisation can allow different kinds of insights to happen during the compositional task. In particular, we used a framework that establishes three different modes of cognitive processing for creativity: deliberate, spontaneous, and flow mode. The neuroscientific evidence is thus interpreted over this framework which allowed the proposition of different strategies in coping creativity, depending on how well-defined or not the objective of a compositional work is.