Trends in Cognitive Sciences
ReviewPerceptual learning, motor learning and automaticitySwitching from automatic to controlled behavior: cortico-basal ganglia mechanisms
Section snippets
Breaking a routine: difficult but crucial
Driving to one's workplace is an easy task: a task that most of us do on a daily basis for several years. On our journey to work we see the same houses, the same trees and the same traffic lights. We might not be aware of our car accelerating or slowing down, despite being the driver. If there is unexpected congestion in the main road ahead then we can quickly decide to avoid the traffic jam by changing our route. But if the decision is late, even by only a second, the chance to turn and avoid
Two modes of behavioral switching
To understand the neural mechanisms of behavioral switching, it is important to determine what triggers such switching. Let us consider a situation in which procedure A is the appropriate behavior in order to obtain a reward in context α, whereas procedure B is the appropriate behavior in context β (Fig. 1), and a motivated subject has already learned these associations. Suppose the context changes from α to β. If the subject is unaware that the context has changed, s/he will perform procedure
The ACC and retroactive switching
The brain region that enables retroactive switching needs to be sensitive to negative feedback (e.g. reduced reward or punishment). It also needs to have access to the brain regions that implement alternative learned procedures. The ACC seems to fulfill both of these requirements.
First, many neurons in the monkey ACC are excited by negative feedback. In experiments using monkeys, the monkeys are trained to perform a task in order to obtain a certain amount of reward. If the reward is absent
The pre-SMA and proactive switching
A conflict in information processing characteristically occurs in proactive switching. The subject's performance on switch trials is much worse (high error rate and longer reaction time) than when the same context is repeated (non-switch trial), a phenomenon called ‘switch cost’ [1]. This is thought to occur because multiple cognitive operations are executed in response to the switch cue, which might include suppression of the old procedure and facilitation of the new procedure. The switch cost
The LPFC and rule implementation
Another cortical area that is thought to be essential for behavioral switching is the LPFC [47]. Subjects with prefrontal lesions show impairments in switching behaviors 48, 49, 50 or in inhibiting prepotent responses 51, 52. Similar to the pre-SMA, the LPFC is activated when response inhibition is required 36, 53. Other studies support the view that the LPFC is predominantly active when relevant rules are retrieved, maintained and implemented 13, 54. Strong activation of the LPFC occurs when
Cortico-basal ganglia mechanisms and behavioral switching
The outcome of behavioral switching is a change in motor behavior. A crucial aspect of behavioral switching, as we have suggested above, is the suppression of prepotent body movements. This is particularly clear for proactive switching, but is also true for retroactive switching in which performance often becomes slower after an erroneous trial 62, 63.
One possibility is that the switch-related cortical signals are mediated by an area that has a powerful capacity to inhibit motor areas. A
Concluding remarks
When the circumstances necessitate it, we make the important decision to change our behavior by breaking a routine. Recent studies with human and non-human primate subjects have begun to elucidate the neural mechanisms underlying such behavioral switching. These studies support the view that different areas in the medial and lateral frontal cortices play executive roles in behavioral switching and do so using different algorithms.
What triggers behavioral switching represents one aspect of the
References (88)
Task switching
Trends Cogn. Sci.
(2003)Action sets and decisions in the medial frontal cortex
Trends Cogn. Sci.
(2004)Conflict monitoring and anterior cingulate cortex: an update
Trends Cogn. Sci.
(2004)- et al.
Cingulate unit activity and delayed response
Brain Res.
(1976) Behavioral shifts and action valuation in the anterior cingulate cortex
Neuron
(2008)Top-down control-signal dynamics in anterior cingulate and prefrontal cortex neurons following task switching
Neuron
(2007)A midline dissociation between error-processing and response-conflict monitoring
Neuroimage
(2003)Error-specific medial cortical and subcortical activity during the stop signal task: a functional magnetic resonance imaging study
Neuroscience
(2008)- et al.
Subprocesses of performance monitoring: a dissociation of error processing and response competition revealed by event-related fMRI and ERPs
Neuroimage
(2001) ‘Error’ potentials in limbic cortex (anterior cingulate area 24) of monkeys during motor learning
Neurosci. Lett.
(1986)