mystery of yawning
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
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La parakinésie brachiale oscitante
Yawning: its cycle, its role
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Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
Le bâillement foetal
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mise à jour le
19 février 2012
Cogn Neurosci.
2011;2(3-4):227-243
On the functional anatomy of the urge-for-action
Jackson SR, Parkinson A, Kim SY, Schüermann M, Eickhoff SB
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Department of Brain and Cognitive Engineering, Korea University, Seoul

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Abstract
 
Several common neuropsychiatric disorders (e.g., obsessive-compulsive disorder, Tourette syndrome (TS), autistic spectrum disorder) are associated with unpleasant bodily sensations that are perceived as an urge for action. Similarly, many of our everyday behaviors are also characterized by bodily sensations that we experience as urges for action. Where do these urges originate? In this paper, we consider the nature and the functional anatomy of "urges-for-action," both in the context of everyday behaviors such as yawning, swallowing, and micturition, and in relation to clinical disorders in which the urge-for-action is considered pathological and substantially interferes with activities of daily living (e.g., TS). We review previous frameworks for thinking about behavioral urges and demonstrate that there is considerable overlap between the functional anatomy of urges associated with everyday behaviors such as swallowing, yawning, and micturition, and those urges associated with the generation of tics in TS. Specifically, we show that the limbic sensory and motor regions-insula and mid-cingulate cortex-are common to all of these behaviors, and we argue that this "motivation-for-action" network should be considered distinct from an "intentional action" network, associated with regions of premotor and parietal cortex, which may be responsible for the perception of "willed intention" during the execution of goal-directed actions.

Many of our everyday behaviors are characterized by bodily sensations that we experience either as an urge or a desire for action. For instance, we may experience a sensation that our bladder is full that is accompanied, to a greater or lesser extent, by an urge or desire to urinate (micturate). In extreme cases, this sense of fullness can be quite uncomfortable and the urge to urinate can be hard to suppress. Similarly, we may experience a tickle in our throat that is associated with an urge to cough or to swallow that can also be difficult to suppress voluntarily.
 
However, not all urges for action are necessarily preceded by bodily sensations of which we are aware. For example, we may suddenly experience a strong urge to yawn, or even fmd ourselves yawning, without being aware of a sensory "trigger" for the action. In this paper, we consider the nature and the functional anatomy of these "urges-for-action," both in the context of everyday behaviors such as yawning, swallowing, and urinating, and in relation to clinical disorders in which the urgefor-action is considered pathological and substantially interferes with activities of daily living (e.g., Tourette syndrome, obsessive-compulsive disorder, addiction).
 
 
A CONCEPTUAL MODEL OF THE URGE-FOR-ACTION
 
In common usage, the terms "urge" and "desire" are frequently encountered as both a verb (as in to "urge someone on"-i.e., to motivate, impel, or stimulate a person toward an action) and as a noun (as in "he felt an urge to shout"-i.e., a force, drive, or impulse that impels toward a goal). Furthermore, these terms are often used interchangeably with one another, and are frequently listed as synonyms.
 
Nevertheless, it has been suggested that there is an important distinction to be made between urges and desires (e.g., Cameron, 2002; Davenport, 2008). Thus, Cameron (2002), when discussing interoception, and the relationship between conscious awareness and visceral events, makes a distinction between "detection," which is an organism's reflexive response based solely upon afferent physiological information, and "perception," which refers to an organism's response based upon all information available to the organism (which might include learned information and expectations that might be generated as a result of learning). Similarly, Davenport, when discussing mechanisms associated with the urge-tocough, defines an urge as a physical need to respond to a sensory stimulus, and a desire as the translation of an urge into what he refers to as "a central neural targeted goal" (Davenport, Sapienza, & BoIser, 2002). Davenport's motivation-to-action model is presented in Figure 1.
 
Combining these two ideas we might conclude that an urge-as in a drive for action-need not enter conscious awareness, but that we are always aware of our desires. An example might help make this distinction clearer. Imagine that you are driving your car and you suddenly become aware of an uncomfortable sensation that your bladder is full, which you experience as the urge to urinate. Given that you can in all likelihood control this urge, you may then form a desire to urinate in which you construct a goal or plan which includes a representation of the behaviors required to complete the action (e.g., remembering that you passed a filling station a mile back and knowing that filling stations usually have public toilets) and a representation of the likely outcomes of the action. Can an urge exist if we are not aware of it? What factors determine whether an urge enters awareness? How is an urge to act different from an intention to act? These issues are discussed below.
 
 
ARE URGES SIMPLY REFLEXES?
 
As outlined above, urges are often defmed as the drives or impulses that impel us to act. Nevertheless, it is argued that actions can, and frequently do, occur in the absence of any awareness of such drivers, as in the case where one fmds oneself yawning without previously being aware of either the desire to yawn or of any bodily sensation that might reasonably be identified as giving rise to the yawn. Instead, one simply fmds oneself yawning. In this case, it might be argued that this is a reflexive behavior and not an urge-for-action.
 
One possible distinguishing feature of urges, as distinct from reflexes, may be that urges are chiefly associated with actions that cannot be realized immediately and must be held in check until an appropriate time when they might be released. For instance, when we become aware of having a full bladder, we experience an "urgeto-void" because we do not simply void our bladder, but instead employ a coordinated set of central, autonomic, and peripheral neural mechanisms to withhold micturition until we are in an appropriate behavioral context. Similarly, in the case of yawning, we might defme the urge-to-yawn as arising in circumstances where we are forced to try to stifle the yawn rather than in the situation where we fmd that we are yawning.
 
 
 
HOW ARE URGES RELATED TO AWARENESS?
 
One factor that may determine whether an urge enters awareness is the intensity of the physiological afferent. It has been demonstrated in the context of the urge-tocough that the perceived strength of the urge that is experienced is related to the intensity of stimulation. Specifically, when capsaicin is added to the breathing circuit, it results in a sensation that is perceived as an urge-to-cough. Furthermore, increasing capsaicin levels leads to a reliable increase in estimates of this urge (Davenport, Sapienza, & BoIser, 2002). Similarly, in our own unpublished studies of the effects of oropharyngeal stimulation on the urge-to-swallow, we have found that oropharyngeal stimulation using pulses of air produces both an urge-to-swallow and overt swallowing (for similar findings, see also Lowell et al., 2008). More importantly, we have found that increasing the intensity of oropharyngeal stimulation leads to an increase in the strength of the perceived urge-to-swallow. An important question therefore concerns the role of awareness, and by implication "desire," in the initiation of urge-related actions.
 
According to the motivation-to-action model represented in Figure 1, actions are initiated only after a desire to perform an action has been formed. However, we do not see this step as necessary and would amend this model, so as to allow for actions to be initiated directly, without the need to first construct an explicit "desire for action." Two factors motivate this amendment. First, it strikes us that in many instances actions (e.g., yawning) can be triggered without our necessarily being aware of any explicit desire. Second, in many clinical conditions (e.g., Tourette syndrome), as we shall see below, unwanted actions or behaviors, which individuals struggle actively to suppress, are nevertheless preceded by strong premonitionary urges. In our view, it is difficult to reconcile the concept of a "desire," which is often defmed as "a longing or craving for something that brings satisfaction or enjoyment," with unwanted actions, the execution of which is experienced as unpleasant and distressing.
 
If we accept the premise outlined above that urges-foraction are often accompanied by bodily sensations, then it strikes us that an important distinction can be drawn between being aware of a bodily sensation and being aware of an urge-for-action. This distinction can be best illustrated by considering the following examples. In the case of an itch, we may be aware of experiencing both an itch (bodily sensation) and an urge to scratch the itch (urge-for-action). By contrast, while we may become aware of an urge-to-yawn, it is not entirely clear that we are ever aware of the bodily sensation that gives rise to the urge to yawn. Furthermore, this becomes more important if we accept the argument outlined above that urges occur primarily in circumstances in which actions may need to be suppressed or their execution deferred. In such circumstances, we might distinguish between suppression of the
 
action associated with the urge-for-action, or suppression of the bodily sensation giving rise to the urge. This distinction has important clinical implications (see below), and an interesting issue for future research will be to detemiine whether the suppression of bodily sensations and the suppression of urges-for-action differ in terms of their functional anatomy.
 
 
HOW IS AN URGE TO ACT DIFFERENT FROM AN INTENTION TO ACT?
 
The kinds of actions that we have considered as representative of urges-for-action are highly automatic, habitual responses that occur primarily in response to sensory stimulation. These might include brushing an insect off your aim, scratching an itch, yawning when tired, coughing in response to a tickle in your throat, etc. While such actions can, in some circumstances, be executed with little or no awareness of the sensory stimulation that triggered the action, as when one finds oneself yawning or coughing, we have argued that a key characteristic of urges-for-action is that they involve the suppression or deferment of an action. Such actions might therefore be contrasted to intentional, goal-directed, forms of action.
 
The circumstances in which the "willed intention" to execute an action can be shown to follow the brain processes involved in the preparation for action were famously studied by Benjamin Libet (Libet, Gleason, Wright, & Pearl, 1983), and more recently by Patrick Haggard and colleagues (e.g., Haggard, 2005; Haggard & Eimer, 1999; Sirigu et al., 2004). In Libet's task, participants fixated on a time-varying, rotating visual spot and were instructed to make a voluntary hand movement whenever they felt the "urge" to do so. Participants were asked to indicate the location occupied by the moving spot when they had first felt the urge to move their hand. Libet showed that this "W judgment" occurred some 200 ms prior to movement onset, but, more importantly, he also showed that the preparatory brain activity that precedes voluntary action, the socalled "readiness potential," itself preceded the "Wjudgment" by several hundred milliseconds. Such readiness potentials arise in the premotor regions of cortex, including both the supplementary motor area (SMA) and the presupplementary motor area (pre-SMA), regions that have been linked to the planning and preparation of intentional, goal-directed, actions and sequences of actions (Deecke & Kornhuber, 1978).
 
Haggard has argued that conscious awareness of our intention to act arises during the preparatory processes that precede an action, and is linked to the joint activity of premotor and parietal brain areas (Haggard, 2005).In support of this view, he has shown that patients with damage to the parietal cortex show a specific impairment in reporting when they became aware of their intention to move (i.e., Libet's "W judgment"). The proposal that the parietal cortex may maintain a dynamically updated state estimate of the current postural configuration of the body (the body schema) is well supported by neuropsychological (e.g., Wolpert, Goodbody, & Husain, 1998) and recent fMRI studies (e.g., Parkinson, Condon, & Jackson, 2010; Pellijeff Bonilha, Morgan, McKenzie, & Jackson, 2006).
 
While it is clearly the case that in such experiments individuals can report when they first perceived themselves to have fonned an "intention" to move, it is another thing entirely to argue that such conscious "intentions" typically precede everyday actions. Thus, when I am sitting at my desk typing and I break off to reach for my coffee cup I am not aware of foiming an intention prior to each keystroke that I make or of forming an intention to reach for my coffee. Instead, I am aware of the actions I am making. Similarly, while it is clearly demonstrated that our actions are preceded by neural activity, as discussed by Libet and by Haggard and colleagues, it is currently unclear how these activations relate to the phenomenology of intention.
 
Haggard and others (e.g., Blakemore, Wolpert, & Frith, 2002; Haggard, 2005) have argued that the sense-of-agency that typically accompanies the execution of voluntary movements arises as a result of internal forward sensory models that generate a prediction of the sensory consequences of an action that is then matched against afferent sensory signals. It has been proposed that in cases where the link between these sensory predictions and confirmatory sensory input is broken, neurological syndromes such as anosagnosia (lack of awareness of injury) or somatoparaphrenia (denial of limb ownership) may occur (Tsakiris, 2010). Interestingly, both of these disorders have been linked to damage of the anterior insular cortex of the right hemisphere (Baier & Karnath, 2008; Karnath, Baier, & Nagele, 2005). However, it is important to note that this sense of agency may in fact have a significant postdictive or reconstructive component (Moore, Lagnado, Deal, & Haggard, 2009; Wegner, 2002) and thus is not necessarily an unambiguous index of intentionality.