Cortico-spinal modularity in the parieto-frontal system: a new perspective on action control

: Classical neurophysiology suggests that the motor cortex (MI) has a unique role in action control. In contrast, this review presents evidence for multiple parieto-frontal spinal command modules that can bypass MI. Five observations support this modular perspective: (i) the statistics of cortical connectivity demonstrate functionally-related clusters of cortical areas, defining functional modules in the premotor, cingulate, and parietal cortices; (ii) different corticospinal pathways originate from the above areas, each with a distinct range of conduction velocities; (iii) the activation time of each module varies depending on task, and different modules can be activated simultaneously; (iv) a modular architecture with direct motor output is faster and less metabolically expensive than an architecture that relies on MI, given the slow connections between MI and other cortical areas; (v) lesions of the areas composing parieto-frontal modules have different effects from lesions of MI. Here we provide examples of six cortico-spinal modules and functions they subserve: module 1) arm reaching, tool use and object construction; module 2) spatial navigation and locomotion; module 3) grasping and observation of hand and mouth actions; module 4) action initiation, motor sequences, time encoding; module 5) conditional motor association and learning, action plan switching and action inhibition; module 6) planning defensive actions. These modules can serve as a library of tools to be recombined when faced with novel tasks, and MI might serve as a recombinatory hub. In conclusion, the availability of locally-stored information and multiple outflow paths supports the physiological plausibility of the proposed modular perspective

Investigation of neuronal structures and networks on the modulation of decision-making and impulse control by temporary inactivation via local microinfusion of the GABAA receptor agonist muscimol in rats

Impulsivity is determined by deficits in decision-making (impulsive choice) and impulse control (impulsive action). Using reversible inactivation via microinfusion of the GABAA receptor agonist muscimol the thesis aimed to elucidate the participation of the ventral medial prefrontal cortex (vmPFC), the nucleus accumbens (NAc) core and shell as well as the connections of the vmPFC and the NAc subregions in both forms of impulsivity in rats. The present results indicate that impulse control is regulated by both structures, while impulsive decision-making is principally modulated by the NAc, and not the vmPFC. The current investigation suggests both functional dissociations and close interactions between the vmPFC and NAc in terms of impulsive action, depending on the involved accumbal subregion. The NAc shell constitutes the critical region mediating both types of impulsivity, whereas the NAc core seems to be implicated in non-specific impairments beyond impulsive choice. Consequently, this work points towards various specific frontostriatal systems differentially contributing to delay-based decision-making and particularly impulse control

Does “Task Difficulty” Explain “Task-Induced Deactivation?”

The “default mode network” is commonly described as a set of brain regions in which activity is suppressed during relatively demanding, or difficult, tasks. But what sort of tasks are these? We review some of the contrasting ways in which a task might be assessed as being difficult, such as error rate, response time, propensity to interfere with performance of other tasks, and requirement for transformation of internal representations versus accumulation of perceptual information. We then describe a fMRI study in which 18 participants performed two “stimulus-oriented” tasks, where responses were directly cued by visual stimuli, alongside a “stimulus-independent” task, with a greater reliance on internally generated information. When indexed by response time and error rate, the stimulus-independent task was intermediate in difficulty between the two stimulus-oriented tasks. Nevertheless, BOLD signal in medial rostral prefrontal cortex (MPFC) – a prominent part of the default mode network – was reduced in the stimulus-independent condition in comparison with both the more difficult and the less difficult stimulus-oriented conditions. By contrast, other regions of the default mode network showed greatest deactivation in the difficult stimulus-oriented condition. There was therefore significant functional heterogeneity between different default mode regions. We conclude that task difficulty – as measured by response time and error rate – does not provide an adequate account of signal change in MPFC. At least in some circumstances, a better predictor of MPFC activity is the requirement of a task for transformation and manipulation of internally represented information, with greatest MPFC activity in situations predominantly requiring attention to perceptual information

The role of the cerebellum in unconsciuos and conscious processing of emotions: a review

Studies from the past three decades have demonstrated that there is cerebellar involvement in the emotional domain. Emotional processing in humans requires both unconscious and conscious mechanisms. A significant amount of evidence indicates that the cerebellum is one of the cerebral structures that subserve emotional processing, although conflicting data have been reported on its function in unconscious and conscious mechanisms. This review discusses the available clinical, neuroimaging and neurophysiological data on this issue. We also propose a model in which the cerebellum acts as a mediator between the internal state and external environment for the unconscious and conscious levels of emotional processing

Hierarchical control over effortful behavior by rodent medial frontal cortex : a computational model

The anterior cingulate cortex (ACC) has been the focus of intense research interest in recent years. Although separate theories relate ACC function variously to conflict monitoring, reward processing, action selection, decision making, and more, damage to the ACC mostly spares performance on tasks that exercise these functions, indicating that they are not in fact unique to the ACC. Further, most theories do not address the most salient consequence of ACC damage: impoverished action generation in the presence of normal motor ability. In this study we develop a computational model of the rodent medial prefrontal cortex that accounts for the behavioral sequelae of ACC damage, unifies many of the cognitive functions attributed to it, and provides a solution to an outstanding question in cognitive control research-how the control system determines and motivates what tasks to perform. The theory derives from recent developments in the formal study of hierarchical control and learning that highlight computational efficiencies afforded when collections of actions are represented based on their conjoint goals. According to this position, the ACC utilizes reward information to select tasks that are then accomplished through top-down control over action selection by the striatum. Computational simulations capture animal lesion data that implicate the medial prefrontal cortex in regulating physical and cognitive effort. Overall, this theory provides a unifying theoretical framework for understanding the ACC in terms of the pivotal role it plays in the hierarchical organization of effortful behavior

Investigating the neural basis of self-awareness deficits following traumatic brain injury

Self-awareness deficits are a common and disabling consequence of traumatic brain injury (TBI). ‘On-line’ awareness is one facet of self-awareness that can be studied by examining how people monitor their performance and respond to their errors. Performance monitoring, like many of the cognitive functions disrupted after TBI, is believed to depend on the coordinated activity of neural networks. The fronto-parietal control network (FPCN) is one such network that contains a sub-network called the salience network (SN). The SN consists of the dorsal anterior cingulate (dACC) and bilateral insulae cortex and is thought to monitor salient events (e.g. errors). I used advanced structure and function MRI techniques to investigate these networks and test two overarching hypotheses: first, performance monitoring is regulated by regions within the FPCN; and second, dysfunction of the FPCN leads to impaired self-awareness after TBI. My first study demonstrated two distinct frontal networks that respond to different error types. Predictable/internally signalled errors caused SN activation; whereas unpredictable/externally signalled errors caused activation of the ventral attentional network, a network thought to respond to unexpected events. This suggested the presence of parallel performance monitoring systems within the FPCN. My second study established that the ‘driving’ input into the SN originated in right anterior insula and subsequent behavioural adaptation was regulated by enhanced effective connectivity from the dACC to the left anterior insula. In my third study I identified a large group of TBI patients with impaired performance monitoring. These patients had additional metacognitive evidence of impaired self-awareness and demonstrated reduced functional connectivity between the dACC and the remainder of the FPCN at ‘rest’, and abnormally large insulae activation in response to errors. These studies clarified how the brain monitors and responds to salient events; and, provided evidence that self-awareness deficits after TBI are due to FPCN dysfunction, identifying this network as a potential target for future treatments.Open Acces

The role of ventrolateral prefrontal cortex in performance of spatial self-ordered response sequences in the marmoset

The ventrolateral prefrontal cortex (vlPFC) in primates plays an important role in cognitive control and working memory, but as argued in the Introduction its contribution to those aspects of goal-directed behaviour such as planning and executing spatial response sequences requires further analysis, using more refined methods than have been employed hitherto. These studies investigated the role of vlPFC in performance of self-ordered response sequences using intra-cerebral microinfusions of specific pharmacologic agents in the common marmoset. Following a description of the necessary methodology, including behavioural training and surgical details (Chapter 2), a causal role for vlPFC in performance of spatial-self ordered sequences was confirmed in Chapter 3 by demonstrating that local inactivation of vlPFC using muscimol/baclofen infusions impairs sequencing. This effect was shown to be selective to performance of sequences that varied spatially from trial to trial; thus, no effects of vlPFC inactivation were observed for performance of a fixed response sequence. Once animals could learn a heuristical strategy for a self-ordered fixed sequence, vlPFC inactivation no longer impaired performance. Chapter 4 investigated the effects of the chemical neuromodulation of vlPFC on self-ordered sequencing using microinfusions of dopamine receptor D2 antagonist, sulpiride, and 5HT2A receptor antagonist, M100907 on performance of variable sequences. These drugs produced contrasting, dose-dependent impairments. M100907 impaired accuracy, while sulpiride impaired error correction. Chapter 5 studied effects of blocking glutamatergic receptors in a region of the caudate nucleus to which the vlPFC projects, but no significant effects on sequencing accuracy were observed, although there were large effects on perseverative errors in 2 out of 3 animals. The findings are discussed in Chapter 6 in terms of the functioning of the vlPFC and its possible role in controlling flexible response sequencing and working memory. The findings are shown to be of relevance for psychiatric disorders such as obsessive compulsive disorder (OCD) and schizophrenia, which show functional dysconnectivity of the vlPFC in association with response sequencing impairments

The neural correlates of ongoing conscious thought

A core goal in cognitive neuroscience is identifying the physical substrates of the patterns of thought that occupy our daily lives. Contemporary views suggest that the landscape of ongoing experience is heterogeneous and can be influenced by features of both the person and the context. This perspective piece considers recent work that explicitly accounts for both the heterogeneity of the experience and context dependence of patterns of ongoing thought. These studies reveal that systems linked to attention and control are important for organizing experience in response to changing environmental demands. These studies also establish a role of the default mode network beyond task-negative or purely episodic content, for example, implicating it in the level of vivid detail in experience in both task contexts and in spontaneous self-generated experiential states. Together, this work demonstrates that the landscape of ongoing thought is reflected in the activity of multiple neural systems, and it is important to distinguish between processes contributing to how the experience unfolds from those linked to how these experiences are regulated. Cognitive Neuroscience; Psychology; Techniques in Neuroscienc

The neural architecture of emotional intelligence.

Emotional Intelligence (EI) is a nebulous concept that permeates daily interpersonal communication. Despite prolific research into its benefits, EI subjective measurement is difficult, contributing to an enigmatic definition of its core constructs. However, neuroimaging research probing socioaffective brain mechanisms underlying putative EI constructs can add an objective perspective to existing models, thereby illuminating the nature of EI. Therefore, the primary aim of this dissertation is to identify brain networks underlying EI and examine how EI arises from the brain’s functional and structural neuroarchitecture. EI is first defined according to behavioral data, which suggests EI is made up of two core constructs: Empathy and Emotion Regulation (ER). The interaction of brain networks underlying Empathy and ER is then investigated using a novel neuroimaging analysis method: dynamic functional connectivity (dynFC). The results suggest efficient communication and (re)configuration between the CEN, DMN, SN underlie both ER and RME task dynamics, and that these temporal patterns relate to trait empathy and ER tendency. Given the demonstrated behavioral and neurobiological relationship between empathy and ER, our second aim is to examine each of these constructs individually through detailed experiments using a variety of neuroimaging methodologies. The dissertation concludes by proposing EI is an ability that arises from the effective, yet flexible communication between brain networks underlying Empathy and ER. The dissertation is divided into five chapters. Chapter I describes the foundational concept of EI as originally described by a variety of psychological figures and the lacuna that exists in terms of its neural correlates. Chapter II presents behavioral data that proposes EI is best predicted by Empathy and ER. Chapter III explores the dynamic relationship between brain networks underlying Empathy and ER, with the aim of elucidating their neurobiological associations, and investigate how such associations may combine to create EI. Chapter IV examines Empathy closely, by probing its neurobiological relationship to interoception and anxiety. Chapter V examines ER closely, by investigating whether gender plays a role in ER, and its neurobiological relationship to hormones. Chapter VI links the general findings from Chapters III, IV and V, and proposes an integrative neurocognitive EI model. The dissertation concludes by providing clinical and non-clinical applications for the model