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In Nederland wordt er op ruim 200 ha Gerbera geteeld en door haar organisatiestructuur heeft de Gerberasector een uitgekiend onderzoeksprogramma. De Gerberateelt is zodoende een van de voorlopers van het doen van onderzoek naar, en vervolgens het toepassen van: Het Nieuwe Telen (HNT).

Contains fulltext : 153891.pdf (publisher's version ) (Open Access), Attention-deficit/hyperactivity disorder (ADHD) is accompanied by impairments in cognitive control, such as task-switching deficits. We investigated whether such problems, and their remediation by medication, reflect abnormal reward motivation and associated striatal dopamine transmission in ADHD. We used functional genetic neuroimaging to assess the effects of dopaminergic medication and reward motivation on task-switching and striatal BOLD signal in 23 adults with ADHD, ON and OFF methylphenidate, and 26 healthy controls. Critically, we took into account interindividual variability in striatal dopamine by exploiting a common genetic polymorphism (3'-UTR VNTR) in the DAT1 gene coding for the dopamine transporter. The results showed a highly significant group by genotype interaction in the striatum. This was because a subgroup of patients with ADHD showed markedly exaggerated effects of reward on the striatal BOLD signal during task-switching when they were OFF their dopaminergic medication. Specifically, patients carrying the 9R allele showed a greater striatal signal than healthy controls carrying this allele, whereas no effect of diagnosis was observed in 10R homozygotes. Aberrant striatal responses were normalized when 9R-carrying patients with ADHD were ON medication. These pilot data indicate an important role for aberrant reward motivation, striatal dopamine and interindividual genetic differences in cognitive processes in adult ADHD.

Contains fulltext : 153891.pdf (publisher's version ) (Open Access), Attention-deficit/hyperactivity disorder (ADHD) is accompanied by impairments in cognitive control, such as task-switching deficits. We investigated whether such problems, and their remediation by medication, reflect abnormal reward motivation and associated striatal dopamine transmission in ADHD. We used functional genetic neuroimaging to assess the effects of dopaminergic medication and reward motivation on task-switching and striatal BOLD signal in 23 adults with ADHD, ON and OFF methylphenidate, and 26 healthy controls. Critically, we took into account interindividual variability in striatal dopamine by exploiting a common genetic polymorphism (3'-UTR VNTR) in the DAT1 gene coding for the dopamine transporter. The results showed a highly significant group by genotype interaction in the striatum. This was because a subgroup of patients with ADHD showed markedly exaggerated effects of reward on the striatal BOLD signal during task-switching when they were OFF their dopaminergic medication. Specifically, patients carrying the 9R allele showed a greater striatal signal than healthy controls carrying this allele, whereas no effect of diagnosis was observed in 10R homozygotes. Aberrant striatal responses were normalized when 9R-carrying patients with ADHD were ON medication. These pilot data indicate an important role for aberrant reward motivation, striatal dopamine and interindividual genetic differences in cognitive processes in adult ADHD.

Contains fulltext : 153891.pdf (publisher's version ) (Open Access), Attention-deficit/hyperactivity disorder (ADHD) is accompanied by impairments in cognitive control, such as task-switching deficits. We investigated whether such problems, and their remediation by medication, reflect abnormal reward motivation and associated striatal dopamine transmission in ADHD. We used functional genetic neuroimaging to assess the effects of dopaminergic medication and reward motivation on task-switching and striatal BOLD signal in 23 adults with ADHD, ON and OFF methylphenidate, and 26 healthy controls. Critically, we took into account interindividual variability in striatal dopamine by exploiting a common genetic polymorphism (3'-UTR VNTR) in the DAT1 gene coding for the dopamine transporter. The results showed a highly significant group by genotype interaction in the striatum. This was because a subgroup of patients with ADHD showed markedly exaggerated effects of reward on the striatal BOLD signal during task-switching when they were OFF their dopaminergic medication. Specifically, patients carrying the 9R allele showed a greater striatal signal than healthy controls carrying this allele, whereas no effect of diagnosis was observed in 10R homozygotes. Aberrant striatal responses were normalized when 9R-carrying patients with ADHD were ON medication. These pilot data indicate an important role for aberrant reward motivation, striatal dopamine and interindividual genetic differences in cognitive processes in adult ADHD.

Choice between actions often requires the ability to retrieve action consequences in circumstances where they are only partially observable. This capacity has recently been argued to depend on orbitofrontal cortex; however, no direct evidence for this hypothesis has been reported. Here, we examined whether activity in the medial orbitofrontal cortex (mOFC) underlies this critical determinant of decision-making in rats. First, we simulated predictions from this hypothesis for various tests of goal-directed action by removing the assumption that rats could retrieve partially observable outcomes and then tested those predictions experimentally using manipulations of the mOFC. The results closely followed predictions; consistent deficits only emerged when action consequences had to be retrieved. Finally, we put action selection based on observable and unobservable outcomes into conflict and found that whereas intact rats selected actions based on the value of retrieved outcomes, mOFC rats relied solely on the value of observable outcomes.

Choice between actions often requires the ability to retrieve action consequences in circumstances where they are only partially observable. This capacity has recently been argued to depend on orbitofrontal cortex; however, no direct evidence for this hypothesis has been reported. Here, we examined whether activity in the medial orbitofrontal cortex (mOFC) underlies this critical determinant of decision-making in rats. First, we simulated predictions from this hypothesis for various tests of goal-directed action by removing the assumption that rats could retrieve partially observable outcomes and then tested those predictions experimentally using manipulations of the mOFC. The results closely followed predictions; consistent deficits only emerged when action consequences had to be retrieved. Finally, we put action selection based on observable and unobservable outcomes into conflict and found that whereas intact rats selected actions based on the value of retrieved outcomes, mOFC rats relied solely on the value of observable outcomes.