Action and the fallacy of the ‘internal’: Comment on Passingham et al

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.

Can neuroscience enlighten the philosophical debate about free will?

Free will has been at the heart of philosophical and scientific discussions for many years. However, recent advances in neuroscience have been perceived as a threat to the commonsense notion of free will as they challenge two core requirements for actions to be free. The first is the notion of determinism and free will, i.e., decisions and actions must not be entirely determined by antecedent causes. The second is the notion of mental causation, i.e., our mental state must have causal effects in the physical world, in other words, actions are caused by conscious intention. We present the classical philosophical positions related to determinism and mental causation, and discuss how neuroscience could shed a new light on the philosophical debate based on recent experimental findings. Overall, we conclude that the current evidence is insufficient to undermine free will.

Check or Go? Impact of Doubt on the Hierarchical Organization of the Mediofrontal Area

BACKGROUND

Based on numerous imaging and electrophysiological studies, the presupplementary motor area (pre-SMA) and the rostral cingulate motor area are cortical regions considered to be essential to voluntary movement initiation and behavioral control. However, their respective roles and functional interactions remain a long-standing and still debated question.

METHODS

Here, we trained 2 rhesus monkeys (Macaca mulatta) in a complex cognitive task to compare the neuronal activity of these 2 regions on the medial wall during both perceptual and internally guided decisions.

RESULTS

We confirmed the implication of both areas throughout the decision process. Critically, we demonstrate that instead of a stable invariant role, the pre-SMA and rostral cingulate motor area manifested a versatile hierarchical relationship depending on the mode of movement initiation. Whereas pre-SMA neurons were primarily engaged in decisions based on perceptual information, rostral cingulate motor area neurons preempted the decision process in case of an internally doubt-driven checking behavior, withholding pre-SMA recruitment during the time spent inhibiting the habitual action.

CONCLUSIONS

We identified a versatile hierarchical organization of the mediofrontal area that may substantially affect normal and pathological decision processes because adaptive behaviors, such as doubt-checking and its compulsive counterpart, rely on this subtle equilibrium in controlling action initiation.

Feeling free: External influences on endogenous behaviour

When we are presented with two equally appealing options, how does the brain break the symmetry between them and make a choice? Recent research has proposed that when no clear information can guide decisions, we use irrelevant noise to tip the scale in favour of one alternative and decide how to act. In the present study, we investigated this issue exploring how human decisions were influenced by noise in a visual signal that cued instructed or free choice. Participants were presented with random-dot kinematograms, moving unidirectionally either upwards or downwards (in instructed trials) or both upwards and downwards simultaneously (free-choice trials). By varying the coherence of dot motion, we were able to test how moment-to-moment fluctuations in motion energy could influence action selection processes. We also measured participants' awareness of such influence. Our results revealed three novel findings: Participants' choices tended to follow fluctuations in dot motion, showing that sensory noise biased "free" selection between actions, irrespective of the clarity of the free cue. However, participants appeared to remain unaware of that influence, because subjective ratings of freedom did not correlate with the degree of sensory biasing. In one exception to this general rule, we found that, when participants resisted the bias and made a choice opposite to the one suggested by the stimulus, they reported strong subjective sense of having chosen independently of the stimulation. This result suggests that inhibitory control is tightly linked to the sense of freedom of choice.

Two Distinctions That Help to Chart the Interplay Between Conscious and Unconscious Volition

Research initiated by Benjamin Libet suggests that short-term conscious intentions are not the onsets of bodily actions. However, other research, particularly on longer-term intentions, seems to show that at least some conscious intentions are effective. This leads to the idea that volition is a complex interplay between conscious and unconscious processes. The nature and structure of this interplay is mostly uncharted territory. In this article, I will highlight two currently neglected distinctions that will help to chart the territory. The first distinction is between intentions we become conscious of (passive) and consciously formed intentions (active). The second is Fred Dretske’s distinction between structuring and triggering causes. I will introduce both distinctions by discussing how they tie in with and strengthen recent criticism of free selection paradigms and support the idea that consciously self-initiated action issues from processes of conscious deliberation and/or information integration. I will argue that consciously self-initiated action typically involves consciously formed intentions that are the structuring causes of our actions. This notion of conscious intentional action allows us to identify at least four stages in which unconscious processes co-determine our actions—without undermining their self-initiated character.

Freely chosen and instructed actions are terminated by different neural mechanisms revealed by kinematics-informed EEG

Neurophysiological accounts of human volition are dominated by debates on the origin of voluntary choices but the neural consequences that follow such choices remain poorly understood. For instance, could one predict whether or not an action was chosen voluntarily based only on how that action is motorically executed? We investigated this possibility by integrating scalp electroencephalograms and index-finger accelerometer recordings acquired while people chose between pressing a left or right button either freely or as instructed by a visual cue. Even though freely selected and instructed actions were executed with equal vigor, the timing of the movement to release the button was comparatively delayed for freely selected actions. This chronometric difference was six-times larger for the β-oscillations over the sensorimotor cortex that characteristically accompany an action's termination. This surprising modulation of an action's termination by volition was traceable to volition-modulated differences in how the competing yet non-selected action was represented and regulated.

Elucidating the neural circuitry underlying planning of internally-guided voluntary action

In an attempt to elucidate the neural circuitry of planning of internally guided voluntary action, Ariani et al. (2015) used a delayed-movement design and multivariate pattern analysis of functional MRI data and found areas decoding internally elicited action plans, stimulus-elicited action plans, and both types of plans. In interpreting their results in the context of a heuristic decision model of voluntary action, encompassing "what" action to perform, "when" to perform it, and "whether" to perform it at all, we highlight at least some neural dissociation of these components. More to that, we note that the exact neural circuitry of each component might vary depending on the performed action type, and finally, we underscore the importance of understanding the temporal specifics of such circuitries to further elucidate how they are involved and interact during voluntary action planning.

The cognitive and neural basis of option generation and subsequent choice

Decision-making research has thoroughly investigated how people choose from a set of externally provided options. However, in ill-structured real-world environments, possible options for action are not defined by the situation but have to be generated by the agent. Here, we apply behavioral analysis (Study 1) and functional magnetic resonance imaging (Study 2) to investigate option generation and subsequent choice. For this purpose, we employ a new experimental task that requires participants to generate options for simple real-world scenarios and to subsequently decide among the generated options. Correlational analysis with a cognitive test battery suggests that retrieval of options from long-term memory is a relevant process during option generation. The results of the fMRI study demonstrate that option generation in simple real-world scenarios recruits the anterior prefrontal cortex. Furthermore, we show that choice behavior and its neural correlates differ between self-generated and externally provided options. Specifically, choice between self-generated options is associated with stronger recruitment of the dorsal anterior cingulate cortex. This impact of option generation on subsequent choice underlines the need for an expanded model of decision making to accommodate choice between self-generated options.

Neurocognitive mechanisms of perception-action coordination: a review and theoretical integration

The present analysis aims at a theoretical integration of, and a systems-neuroscience perspective on, a variety of historical and contemporary views on perception-action coordination (PAC). We set out to determine the common principles or lawful linkages between sensory and motor systems that explain how perception is action-oriented and how action is perceptually guided. To this end, we analyze the key ingredients to such an integrated framework, examine the architecture of dual-system conjectures of PAC, and endeavor in an historical analysis of the key characteristics, mechanisms, and phenomena of PACs. This analysis will reveal that dual-systems views are in need of fundamental re-thinking, and its elements will be amalgamated with current views on action-oriented predictive processing into a novel integrative theoretical framework (IMPPACT: Impetus, Motivation, and Prediction in Perception-Action Coordination theory). From this framework and its neurocognitive architecture we derive a number of non-trivial predictions regarding conative, motive-driven PAC. We end by presenting a brief outlook on how IMPPACT might present novel insights into certain pathologies and into action expertise.

Information gain in the brain's resting state: A new perspective on autism

Along with the study of brain activity evoked by external stimuli, an increased interest in the research of background, “noisy” brain activity is fast developing in current neuroscience. It is becoming apparent that this “resting-state” activity is a major factor determining other, more particular, responses to stimuli and hence it can be argued that background activity carries important information used by the nervous systems for adaptive behaviors. In this context, we investigated the generation of information in ongoing brain activity recorded with magnetoencephalography (MEG) in children with autism spectrum disorder (ASD) and non-autistic children. Using a stochastic dynamical model of brain dynamics, we were able to resolve not only the deterministic interactions between brain regions, i.e., the brain's functional connectivity, but also the stochastic inputs to the brain in the resting state; an important component of large-scale neural dynamics that no other method can resolve to date. We then computed the Kullback-Leibler (KLD) divergence, also known as information gain or relative entropy, between the stochastic inputs and the brain activity at different locations (outputs) in children with ASD compared to controls. The divergence between the input noise and the brain's ongoing activity extracted from our stochastic model was significantly higher in autistic relative to non-autistic children. This suggests that brains of subjects with autism create more information at rest. We propose that the excessive production of information in the absence of relevant sensory stimuli or attention to external cues underlies the cognitive differences between individuals with and without autism. We conclude that the information gain in the brain's resting state provides quantitative evidence for perhaps the most typical characteristic in autism: withdrawal into one's inner world.

Imaging volition: what the brain can tell us about the will

The question of how we can voluntarily control our behaviour dates back to the beginnings of scientific psychology. Currently, there are two empirical research disciplines tackling human volition: cognitive neuroscience and social psychology. To date, there is little interaction between the two disciplines in terms of the investigation of human volition. The aim of the current article is to highlight recent brain imaging work on human volition and to relate social psychological concepts of volition to the functional neuroanatomy of intentional action. A host of studies indicate that the medial prefrontal cortex plays a crucial role in voluntary action. Accordingly, we postulate that social psychological concepts of volition can be investigated using neuroimaging techniques, and propose that by developing a social cognitive neuroscience of human volition, we may gain a deeper understanding of this fascinating and complex aspect of the human mind.

Frontostriatal mechanisms in instruction-based learning as a hallmark of flexible goal-directed behavior

The present review intends to provide a neuroscientific perspective on the flexible (here: almost instantaneous) adoption of novel goal-directed behaviors. The overarching goal is to sketch the emerging framework for examining instruction-based learning and how this can be related to more established research approaches to instrumental learning and goal-directed action. We particularly focus on the contribution of frontal and striatal brain regions drawing on studies in both, animals and humans, but with an emphasize put on human neuroimaging studies. In section one, we review and integrate a selection of previous studies that are suited to generally delineate the neural underpinnings of goal-directed action as opposed to more stimulus-based (i.e., habitual) action. Building on that the second section focuses more directly on the flexibility to rapidly implement novel behavioral rules as a hallmark of goal-directed action with a special emphasis on instructed rules. In essence, the current neuroscientific evidence suggests that the prefrontal cortex and associative striatum are able to selectively and transiently code the currently relevant relationship between stimuli, actions, and the effects of these actions in both, instruction-based learning as well as in trial-and-error learning. The premotor cortex in turn seems to form more durable associations between stimuli and actions or stimuli, actions and effects (but not incentive values) thus representing the available action possibilities. Together, the central message of the present review is that instruction-based learning should be understood as a prime example of goal-directed action, necessitating a closer interlacing with basic mechanisms of goal-directed action on a more general level.