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The ability to prepare for an action improves the speed and accuracy of its performance. While many studies indicate that behavior performance continues to improve throughout childhood and adolescence, it remains unclear whether or how preparatory processes change with development. Here, we used a rapid event-related fMRI design in three age groups (8-12, 13-17, 18-25years) who were instructed to execute either a prosaccade (look toward peripheral target) or an antisaccade (look away from target) task. We compared brain activity within the core fronto-parietal network involved in saccade control at two epochs of saccade generation: saccade preparation related to task instruction versus saccade execution related to target appearance. The inclusion of catch trials containing only task instruction and no target or saccade response allowed us to isolate saccade preparation from saccade execution. Five regions of interest were selected: the frontal, supplementary, parietal eye fields which are consistently recruited during saccade generation, and two regions involved in top down executive control: the dorsolateral prefrontal and anterior cingulate cortices. Our results showed strong evidence that developmental improvements in saccade performance were related to better saccade preparation rather than saccade execution. These developmental differences were mostly attributable to children who showed reduced fronto-parietal activity during prosaccade and antisaccade preparation, along with longer saccade reaction times and more incorrect responses, compared to adolescents and adults. The dorsolateral prefrontal cortex was engaged similarly across age groups, suggesting a general role in maintaining task instructions through the whole experiment. Overall, these findings suggest that developmental improvements in behavioral control are supported by improvements in effectively presetting goal-appropriate brain systems. [ABSTRACT FROM AUTHOR]

Cognitive decline during aging includes impairments in frontal executive functions like reduced inhibitory control. However, decline is not uniform across the population, suggesting individual brain response variability to the aging process. Here we tested the hypothesis, within the oculomotor system, that older adults compensate for age-related neural alterations by changing neural activation levels of the oculomotor areas, or even by recruiting additional areas to assist with cognitive performance. We established that the observed changes had to be related to better cognitive performance to be considered as compensatory. To probe this hypothesis we used the antisaccade paradigm and analyzed the effect of aging on brain activations during the inhibition of prepotent responses to visual stimuli. While undergoing a fMRI scan with concurrent eye tracking, 25 young adults (21.7 y/o ± 1.9 SDM) and 25 cognitively normal older adults (66.2 y/o ± 9.8 SDM) performed an interleaved pro/antisaccade task consisting of a preparatory stage and an execution stage. Compared to young adults, older participants showed a larger increase in antisaccade reaction times, while also generating more antisaccade direction errors. BOLD signal analyses during the preparatory stage, when response inhibition processes are established to prevent an automatic response, showed decreased activations in the anterior cingulate and the supplementary eye fields in the older group. Moreover, older adults also showed additional recruitment of the frontal pole not seen in the younger group, and larger activations in the dorsolateral prefrontal cortex during antisaccade preparation. Additional analyses to address the performance variability in the older group showed distinct behavioral-BOLD signal correlations. Larger activations in the saccade network, including the frontal pole, positively correlated with faster antisaccade reaction times, suggesting a functional recruitment of this area. However, only the activation in the dorsolateral prefrontal cortex during the antisaccade events showed a negative correlation with the number of errors across older adults. These findings support the presence of two dissociable age-related plastic mechanisms that result in different behavioral outcomes. One related to the additional recruitment of neural resources within anterior pole to facilitate modulation of cognitive responses like faster antisaccade reaction times, and another related to increased activation of the dorsolateral prefrontal cortex resulting in a better inhibitory control in aging. [ABSTRACT FROM AUTHOR]

Abstract: Recent evidence has shown that patients with Parkinson''s disease (PD) often display deficits in executive functions, such as planning for future behavior, and these deficits may stem from pathologies in prefrontal cortex and basal ganglia circuits that are critical to executive control. Using the antisaccade task (look away from a visual stimulus), we show that when the preparatory ‘readiness’ to perform a given action is dissociated from the actual execution of that action, PD patients off and on dopamine medication display behavioral impairments and reduced cortical brain activation that cannot be explained by a pathology related to dysfunction in movement execution. Rather, they show that the appropriate task set signals were not in place in motor regions prior to execution, resulting in impairments in the control of subsequent voluntary movement. This is the first fMRI study of antisaccade deficits in Parkinson''s disease, and importantly, the findings point to a critical role of the basal ganglia in translating signals related to rule representation (executive) into those governing voluntary motor behavior. [Copyright &y& Elsevier]