18 Nisan 2013 Perşembe

A Short Outline of Automatic motor activation in the executive control of action

For various performers on the field

[1] Automatic and unconscious processes are traditionally regarded as inflexible (e.g., Shiffrin and Schneider, 1977, 1984), quite distinct in quality from the flexible nature of “voluntary” processes. However, there is increasing evidence that automatic and subliminal processes can in fact be modulated by “top-down” processes of attention, intention (“task set” or current goals) and expectation.

[2] DISSOCIATIONS IN AUTOMATIC AND VOLUNTARY CONTROL
Recent work from Boy et al. (2010b) suggests that the important distinction is not between control that is automatic compared to control that is voluntary, but rather between pre- and poststimulus control

[3] PRE-STIMULUS VS. POST-STIMULUS COGNITIVE CONTROL
Control mechanisms that can override inappropriate response plans which have been automatically evoked by the environment not only act to inhibit responses after they have been evoked by the stimulus. Pre-stimulus control mechanisms also seem to play a role. Thus, task set and previous experience can modulate conflicting response tendencies in a preparatory manner.

[4] EVIDENCE FOR AUTOMATIC ACTIVATION OF MOTOR RESPONSES
Perceptual processing of a visual stimulus can result in motor responses even when the observer does not intend to act. One of the most well-studied of these phenomena is the “visual grasp reflex”, where an observer makes a fast, reflexive eye movement (saccade) toward a suddenly appearing—and irrelevant—visual stimulus, despite their intention to look elsewhere (e.g., Theeuwes et al., 1998; Irwin et al., 2000). ... But as response latencies increase, saccades are more likely to curve away from a distractor (e.g., Walker et al., 2006), revealing an inhibitory mechanism acting to suppress unwanted motor activity toward the irrelevant stimulus (e.g., Sheliga et al., 1995). 

[5] EVIDENCE FOR AUTOMATIC MOTOR ACTIVATION FROM “PARTIAL” ERRORS
However, it is possible that small amounts of force applied (erroneously) to a button might be insufficient to trigger a measurable response and thereby escape detection.  ... trials provides strong evidence that an irrelevant stimulus—or part of a stimulus—can automatically activate responses associated with it. These responses are not merely partially activated somewhere in the brain; the response can be measured in the muscles or in small hand movements with force transducers. 

[6] INVISIBLE INFLUENCES
In summary, shifts of attention and motor responses can be automatically and unconsciously triggered by visual stimuli. Effects of non-perceived stimuli such as these have provided key evidence that visual stimuli can automatically prime the observer to act.

[7] INHIBITION OF PRIMED ACTIONS
Thus, it is necessary to consider how brain systems inhibit or override responses that have been triggered automatically by the environment and are not relevant to our current goals....Processing by the fast, direct processing route is automatic, and occurs irrespective of task instructions. For example, the spatial location of a target stimulus in a Simon task would be processed quickly and automatically via the direct processing route. At the same time, processing of the task-relevant target attribute (e.g., target color in a Simon task) proceeds via a slower indirect processing route. On congruent trials, the same response is activated by both the direct and the indirect processing routes, producing fast, correct responses. On incongruent trials, however, the direct processing route and the indirect processing route activate different responses which results in increased error rates, and slower response times as the conflict between competing responses is resolved.

... Importantly, models of information processing in conflict tasks often include an active inhibition mechanism which acts to selectively suppress inappropriate response activation resulting from the direct processing route...

In conflict tasks, accuracy for compatible trials is near-perfect, while fast responses on incompatible trials are often near (e.g., Wylie et al., 2009) or below (e.g., Stins et al., 2007) chance level.

...that erroneous responses are activated quickly via the direct processing route, before being selectively suppressed by an inhibitory control mechanism. 

[8] UNCONSCIOUS CONTROL OVER UNWANTED RESPONSES
inhibition of primed responses only operates when stimuli are presented above—and not below—the threshold required for conscious awareness (e.g., Merikle et al., 1995 using the Stroop task).  However, when the interval between prime and mask was extended beyond around 100–150 ms, incompatible trials produced faster responses than compatible trials. In other words, the usual priming effect had reversed.  This negative compatibility effect (NCE) has now been widely reported with button-press responses, foot responses, and eye  movements



... Many researchers have suggested that this reversed priming results from an inhibitory mechanism in the motor system which acts to suppress sub-threshold motor activation evoked by the prime
[9] AUTOMATIC INHIBITION IN THE AFFORDANCE PARADIGM
visual stimuli automatically evoke motor responses, Overall, these studies suggest that actions which have been automatically primed by object affordances may also be subject to automatic control.

[10] AUTOMATIC TRIGGERING OF “ENDOGENOUS” CONTROL
However, recent work suggests that endogenous suppression of pre-potent responses can also be primed or evoked unconsciously and automatically (e.g., Verbruggen and Logan, 2009a; van Gaal et al., 2008, 2009, 2010a,b).

[11] AUTOMATIC PRE-STIMULUS CONTROL
 Many researchers have suggested that observers must consciously experience conflict in order for the pre-stimulus control mechanisms to be deployed (e.g., Kunde, 2003; Mayr, 2004; Ansorge et al., 2011). However, recent evidence from van Gaal et al. (2010a) suggests that some pre-stimulus control can be evoked automatically, without conscious awareness. ...unconsciously presented stimuli can automatically evoke these pre-stimulus conflict adaptation mechanisms, and can modulate the effects of subsequent conflicting stimuli.

 Edited by Ali R+ SARAL from[REF-1]

[1] Jennifer McBride1*, Frédéric Boy2, Masud Husain1 and Petroc Sumner2 ‘Automatic motor activation in the executive control of action
1 Institute of Cognitive Neuroscience and Institute of Neurology, University College London, London, UK
2 School of Psychology, Cardiff University, Cardiff, UK