B.J.Casey et al./Biological Psychology54(200)241-257 251 2.2.Attention and inhibition Which prefrontal systems are involved in selective attention when there is interference from competing sources,either during input or output?Two examples of developmental fMRI studies addressing this question are described below. One classic paradigm for examining selective attention when there is interference no-go At least one fMRI study using a ve sion and Nine chre -12 yaranddu d to years)were scanned while performing a version of the task.The task required that the subject simply press a button to all sequentially presented letters except the letter'X'.Stimulus duration was 500 ms and the interstimulus interval was 1500 ms. The percentage of targets(non-Xs)was maintained at 75%to increase the degree of interfer ence in the output by building prep otent tendency to re ond.Gradien echo echo 600 0128×64 c isiti rix)we acquired in igh t shages TR mm contiguou coronal slice loc ns during three conditions:(1)inhibitory trials defined by the presence of 50%nontargets (i.e.Xs) (2)control trials consisting of 100%targets (i.e.non Xs);and (3)control trials consisting of 100%targets,but with interstimulus intervals of 3500 ms,resulting in an equal number of motor responses as the inhibitory condition.The two compari- son conditions thus controlled for stimulus parameters (number of stimuli and interstimulus val) esponse parameters(number of r espo ses and inter-re- sponse interval),respectively An analysis of variance with a Bonferroni adjustment showed reliable activation in the anterior cingulate,inferior and middle frontal gyri,and orbitofrontal gyri for both the children and adults.In this investigation,the general location of activation in prefrontal cortex did not differ for children as compared to adults.but overall volume of prefrontal activation.particularly in dorsolateral prefrontal regions.was ndu (refer to i)This dier ence in volume of activity was due to a lack of robust activity in this area for p≤0 1500 <05 Middle Frontal Gyrus Superior Frontal Gyrus Fig.5.Volume of brain activation in the superior and middle frontal gyri for children and adults during the performance of a go no-go task.B.J. Casey et al. / Biological Psychology 54 (2000) 241–257 251 2.2. Attention and inhibition Which prefrontal systems are involved in selective attention when there is interference from competing sources, either during input or output? Two examples of developmental fMRI studies addressing this question are described below. One classic paradigm for examining selective attention when there is interference during output is the go no-go paradigm. At least one fMRI study using a version of the go no-go paradigm with healthy children and adults has been published to date (Casey et al., 1997). Nine children (7–12 years) and nine young adults (21–24 years) were scanned while performing a version of the task. The task required that the subject simply press a button to all sequentially presented letters except the letter ‘X’. Stimulus duration was 500 ms and the interstimulus interval was 1500 ms. The percentage of targets (non-Xs) was maintained at 75% to increase the degree of interference in the output by building a prepotent tendency to respond. Gradient￾echo, echo planar images TR=6000, TE=40, 128×64 acquisition matrix) were acquired in eight 5 mm contiguous coronal slice locations during three task conditions: (1) inhibitory trials defined by the presence of 50% nontargets (i.e. Xs); (2) control trials consisting of 100% targets (i.e. non Xs); and (3) control trials consisting of 100% targets, but with interstimulus intervals of 3500 ms, resulting in an equal number of motor responses as the inhibitory condition. The two compari￾son conditions thus controlled for stimulus parameters (number of stimuli and interstimulus interval) and response parameters (number of responses and inter-re￾sponse interval), respectively. An analysis of variance with a Bonferroni adjustment showed reliable activation in the anterior cingulate, inferior and middle frontal gyri, and orbitofrontal gyri for both the children and adults. In this investigation, the general location of activation in prefrontal cortex did not differ for children as compared to adults, but overall volume of prefrontal activation, particularly in dorsolateral prefrontal regions, was greater for children than adults (refer to Fig. 5). This difference in volume of dorsolateral prefrontal activity was due to a lack of robust activity in this area for Fig. 5. Volume of brain activation in the superior and middle frontal gyri for children and adults during the performance of a go no-go task