Gain of memory guided saccades is modulated by prefrontal dopamine J Billino1, J Hennig2, K R Gegenfurtner3 |
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1Justus-Liebig University of Giessen, Germany |
| Memory guided saccades require the subject not only to control occulomotor behavior voluntarily, but also to encode and remember the spatial position of a target precisely. Here we were interested in how supposed differences in prefrontal dopaminergic activation in healthy adults affect accuracy and precision of saccades to remembered targets. 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 in prefrontal cortex and accordingly to higher dopamine levels. We investigated memory guided saccades in 105 subjects and determined the individual genotypes. While subjects were fixating a target was presented for 200 ms at one of three randomly varied horizontal positions (4, 10, and 16 deg). After a delay of 1500ms the fixation point changed its color and subjects were supposed to saccade to the remembered target position. We found a significant effect of genotype on average gain (F(1, 105)=4.11, p=.045, h2=.04) and a statistical trend for gain variability (F(1, 105)=3.00, p=.086, h2=.03). Met homozygotes (n=31) showed lower average gain and higher gain variability than val allele carriers. Our results provide evidence of dopaminergic modulation of saccadic accuracy and precision. |
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