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Jutta Billino, Jürgen Hennig, Karl Gegenfurtner; Dopaminergic modulation of saccadic control. Journal of Vision 2012;12(9):1260. doi: 10.1167/12.9.1260.
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Processing pathways involved in saccadic control have been elaborately described over the last years, however little is known about the dynamic modulation of saccades by specific neurotransmitters. Clinical as well as recent experimental evidence suggests that prefrontal dopamine not only plays an important role in cognitive functions, but also in sensorimotor processes. We were interested in saccadic latency in healthy adults with supposed differences in dopaminergic activation. Catechol-O-methyltransferase (COMT) plays a major role in the regulation of prefrontal dopamine levels. The COMT val158met polymorphism modulates enzyme activity in that met alleles lead to less active dopamine degradation and accordingly to higher dopamine levels. We investigated latency of reflexive saccades in 110 subjects (91 females, age M=23.2, SD=4.9) and determined the individual genotypes (ValVal n=24, ValMet n=54, MetMet n=32). Subjects had to make horizontal saccades to targets presented either in an overlap or a gap condition. In the overlap condition, the fixation stimulus remained present during target presentation, in the gap condition, the fixation stimulus disappeared 200ms before target onset. Introducing a gap has been shown to substantially reduce saccadic latencies by inducing a preparatory process. Analysis of saccade latencies revealed significant differences between genotypes in the overlap condition (F(2, 109)=10.2, p<.001), but not in the gap condition (F(2, 109)=0.6, p=.573). In the overlap condition Met allele carriers showed higher latencies than Val homozygotes. We confirmed a significant interaction between genotype and gap condition (F(2, 107)=8.4, p<.001). The gap condition elicited a greater latency reduction in Met allele carriers. Our results provide evidence of dopaminergic modulation of saccadic control in healthy subjects. We relate our findings to the tonic-phasic dopamine hypothesis proposing that higher prefrontal dopamine levels trigger increased stability and decreased flexibility of subcortical network activation. We suppose that this pattern might be a disadvantage when preparatory processes are minimized.
Meeting abstract presented at VSS 2012
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