1,721,058 research outputs found
Errare humanum est, avoiding the error even more: fMRI evidence of brain networks involved in response suppression
Full text linkRegional frontal injuries cause distinct impairments in cognitive control
No full textBackground: Lesions of the frontal lobes may impair the capacity of patients to control otherwise intact cognitive operations in the face of ambiguous sensory input or conflicting possible responses.
Objective: To address the question of whether focal lesions in different regions of the frontal lobes produced specific impairments in cognitive control.
Methods: We evaluated 42 patients with chronic frontal lesions and 38 control subjects on a modified Stroop test that allowed measurement of reaction times and errors. Planned, stratified analyses permitted identification of discrete frontal lesions that are critical for impaired performance.
Results: Lesions of the left ventrolateral region produced an increased number of incorrect responses to distractors. Lesions of a large portion of the right superior medial region, including anterior cingulate, supplementary motor area (SMA), pre-SMA, and dorsolateral areas, caused a slow reaction time and a decreased number of correct responses to targets.
Conclusion: Lesions in two distinct frontal regions impair cognitive control for a Stroop task, and the mechanisms of impairment are specific to the region of injury. This is support for a general proposal that the supervisory system is constructed of distinct subsystems
FMRI evidence of a functional network setting the criteria for withholding a response
Full text linkThat the left prefrontal cortex has a critical role setting response criteria for numerous tasks has been well established, but gaps remain in our understanding of the brain mechanisms of task-setting. We aimed at (i) testing the involvement of this region in setting the criteria for a non-response and (ii) assessing functional connectivity between this and other brain regions involved in task-setting. Fourteen young participants performed a go/nogo task during functional magnetic resonance imaging. The task included two nogo visual stimuli which elicit a high (distractor) or a low (other) tendency to respond, respectively. Two task blocks were examined to assess learning the criteria. First, a multivariate Partial Least Squares (PLS) analysis identified brain regions that co-varied with task conditions, as expressed by two significant Latent Variables (LVs). One LV distinguished go and nogo stimuli. The other LV identified regions involved in the first block when the criteria not to respond to distractors were established. The left prefrontal region was prominently involved. Second, a left ventrolateral prefrontal area was selected from this LV as a seed region to perform functional connectivity using a multi-block PLS analysis. Results showed a distributed network functionally connected with the seed, including superior medial prefrontal and left superior parietal regions. These findings extend our understanding of task-setting along the following dimensions: 1) even when a task requires withholding a response, the left prefrontal cortex has a critical role in setting criteria, and 2) this region responds to the task demands within a distinctive functional network
When time shapes behaviour: fMRI evidence of brain correlates of strategic preparation over time
No full textCognitive and neural correlates of normal aging in task-setting: interactive effects of practice, conflict and task complexity
No full textTemporal preparation in aging: a functional MRI study
No full textYoung and elderly adults performed a choice-RT task while scanned with functional magnetic resonance imaging. A foreperiod separated a warning and a response signal. In the variable condition, the foreperiod varied randomly between 1 and 3s. In the fixed conditions, it was kept constant at either 1 or 3s. Elderly subjects responded slower than controls in both task conditions. An interaction was observed between age and foreperiod in the variable condition only: in the young group, RT decreased with longer foreperiods, whereas the elderly participants showed the opposite tendency. This was accompanied by difference in brain activation. Right lateral prefrontal regions were more activated in the young than in the elderly group in the variable vs. fixed foreperiod contrast. These findings unveil the neural substrate of age-related preparation deficits, and confirm that the involvement of right lateral prefrontal cortex is essential for strategic preparation under uncertain timing conditions
Prefrontal Involvement in Switching Between Speed and Accuracy: An fMRI Study
No full textStrategically switching between rapid and accurate decision-making requires a top-down regulation of the response criteria. However, the brain mechanisms important to smoothly change the speed-accuracy strategy trial-by-trial remain mostly unclear. This issue was addressed here by testing 12 right-handed volunteers (6 females, age: 19-39 years) using fMRI. On each trial, participants had to stress speed or accuracy in performing a color discrimination task on a target stimulus according to the instructions given by an initial cue. As the behavioral data showed, participants were capable of trading speed for accuracy and vice versa. Standard GLM whole-brain analyses on cue-related activations revealed a significant recruitment of left middle frontal gyrus (Talairach coordinates = x: -32, y: 32, z: 26) and right cerebellum (32, -42, -30) when switching from speed to accuracy (vs. from accuracy to speed). Analysis of target-related activations suggested that the anterior cingulate cortex (-4, 24, 15) was more recruited during speeded (vs. accuracy) trials, especially when those were preceded by another speeded trial. The present results extend previous findings on the role of left lateral prefrontal cortex in initial task-setting and anterior cingulate in subsequent energization of the relevant processes to the control of speed-accuracy trade-off
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