Chapter 7 - Network convergence zones in the anterior midcingulate cortex
Introduction
The rostral cingulate cortex is a diverse cortical structure. It has classically been conceptualized as being comprised of several subdivisions, each with distinct structural features and patterns of connectivity that enable a range of self-regulatory functions. Broadly, a subdivision rostral to the genu of the corpus callosum is known as the anterior cingulate cortex (ACC) and is thought to play a crucial role in initiation, motivation, and goal-directed behaviors (Devinsky et al., 1995), while the caudal subdivision, referred to as the midcingulate cortex (MCC), is implicated in action monitoring and motoric processes (Amodio and Frith, 2006). An early meta-analysis of human neuroimaging studies of rostral cingulate function described regionally specific patterns of activation suggesting an anterior and posterior midcingulate cortex (aMCC, pMCC, respectively) vs subcallosal ACC, and limbic vs paralimbic subdivisions (Paus et al., 1998). Subsequent research corroborated the notion that the rostral cingulate is comprised of subdivisions with distinct anatomic and functional properties and linked the commonly observed anterior-to-posterior gradient with affective and cognitive functions, respectively (Koski and Paus, 2000). Taken in context, these lines of research suggest that the rostral cingulate contributes to behavior by modifying responses, particularly in reaction to challenges requiring effortful cognitive control (Gasquoine, 2013), and that it may serve an integrative function of translating intentions into actions (Paus, 2001).
This chapter aims to situate a specific portion of the rostral cingulate—the aMCC—along this complex processing stream. We begin by describing its topography based on studies of cortical microstructure and connectivity. We then turn to the complex and, at times, contentious functional literature, offering a parsimonious summary of functional gradients that situate aMCC at the motoric and control end of the spectrum. Finally, we turn to the recent literature on large-scale functional networks, describing the participation of aMCC in several functional systems subserving attention and control processes, with special attention to the widely studied salience network (Seeley et al., 2007; Uddin, 2015). By establishing the salience network between caudal motoric systems and rostral affect regulation circuitry (Ochsner and Gross, 2005) and the default mode network (Greicius et al., 2003), these lines of research support interpretation of the aMCC as a crucial nexus of control along a macroscale gradient of cortical function.
Section snippets
Delineating the aMCC
To situate the aMCC within large-scale cortical networks and functional hierarchies, we begin by clarifying its location along the cingulate cortex. This definition is necessary at the outset, as the aMCC is often described in the cognitive neuroimaging literature using the anterior cingulocentric nomenclature of “dorsal anterior cingulate cortex” to describe what is in fact one of the most frequently activated cortical regions (Yarkoni et al., 2011). However, based on the proximity of its cyto
Functions of the aMCC
In one of the earliest positron emission tomography (PET) studies of language, Petersen et al. (1989) observed aMCC activation during semantic association tasks. They suggested that this activation might reflect nonspecific arousal from either task difficulty or selection for action (Petersen et al., 1989). Since this work, human neuroimaging studies have reported aMCC activation across a range of paradigms. One striking observation from meta-analytic findings summarizing thousands of fMRI task
aMCC and the Salience Network
A significant portion of the literature in neuroscience and psychology deals with the topic of salience detection and processing, where salience is defined as objects, ideas, or events that are very important or noticeable and thus attract attention. Salience is well defined and relatively straightforward to operationalize in vision research and computational models of attention. However, the term is also used in other contexts to mean personal relevance, where stimuli or events that are
Conclusions
The findings reviewed here, while partially consistent with traditional views of a subdivisional organization within the cingulate cortex, leave room for a view that incorporates recent evidence for functional gradients that capture the overarching layout. While the classic conceptualization of an anterior-to-posterior gradient delineating affective and cognitive functions of the ACC still holds up under many circumstances, other lines of empirical work point to alternate, more gradual
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