How it is possible to distinguish between the brain systems involved in primary timekeeper function and those related to attentional resources

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Slide 1 : How it is possible to distinguish between the brain systems involved in primary timekeeper function and those related to attentional resources?
Slide 2 : Grafton ST. Nature Neuroscience Vol.6(7) 2003.
Slide 3 : Grafton ST. Nature Neuroscience Vol.6(7) 2003.
Slide 4 : Literature “This brief overview of the brain imaging literature inthe field of timing thus points to a core of structures thatare often activated in timing tasks, irrespective of particularprocedural features. On these grounds, an inescapablequestion is whether the structures selected are actually involved in time processing or are related to otherprocesses that might be equivalent in non-temporal tasks,such as sensory and motor components, attentionaleffort, or memory load.Control tasks are one method of approaching thisproblem.”Macar F. Exp Brain Res (2002) 142:475–485.
Slide 5 : Our Hypothesis: In this work we are interested in discriminate between the brain structures related to processes modulated by attentional level and areas involved in time-keeper function (primary processes) when performing the sensorimotor synchronization to external visual stimuli task. To this aim we did: Motor Synchronization Vs VRandom Motor Synchronization Vs VRhythmic
Slide 6 : Our Hypothesis: 1) The simple perception of rhythmic isochronous stimuli (VRhythmic) demands a lower level of attention.2) While the simple perception of random stimuli (VRandom) could enhance the attentional level. To distinguish these brain structures, we used 2 Different Baseline conditions
Slide 7 : Background The neurophysiological study of Priming processes demonstrated that: 1) cell recordings in the monkey infero-temporal cortex showed that when the same visual stimulus was repeated, the neural activity evoked in sole of the cells was reduced. (Desimone R. PNAS, 1996) 2) The brain imaging priming experiments, in which a subject is exposed to a prime then to a target stimulus, reported a decreased in neural activity in many different regions: insula, parietal and prefrontal cortices, thalamus and basal ganglia. (Schacter et al. Science, 1996) The event-related design is better than block design in order to study brain activity correlated to priming processes because the subject’s attention could have varied across experimental blocks, with more attention being given to blocks in which the stimuli were more varied, respect to blocks with repetitive stimuli. (Naccache L et al. Cerebral Cortex, 2001)
Slide 8 : Results
Slide 9 : Results
Slide 10 : Results Differences of activations between conventional-baseline (red, Vrhy), visually cued motor synchronization task (green, VM) and random-baseline (yellow, Vran) in the bilateral caudate nucleus, the right ventral premotor cortex (vPMC), the right inferior frontal gyrus (IFG) and bilateral insula. Top: cluster localization; the cluster is superimposed on three orthogonal sections of the template image present in SPM. Bottom the diagram shows the effect sizes for the three conditions; the data arise from random effect analysis (one sample t test, P level <0.001 uncorrected, P < 0.05 corrected for multiple comparisons) of main effects.
Slide 11 : Discussion We found that brain areas with a documented role in basic time processing are detected independent of the baseline condition. These areas are the right cerebellum, bilateral putamen, left thalamus, left superior temporal gyrus, left sensorimotor cortex, left dorsal premotor cortex and supplementary motor area. The novel finding of the present work regards the activation of additional brain areas: caudate nucleus bilaterally, right vPMC, bilateral insula and right IFG that were detected only when the conventional-baseline condition (Vrhy) was used.
Slide 12 : Discussion Our results and the literature findings cited above confirm that by varying the predictability of stimulus onsets in the baseline condition the activation elicited by a visually cued motor synchronization task changes. While brain areas with a documented role in basic time processing (right cerebellum, bilateral putamen, left thalamus, left STG, left sensorimotor cortex, left dPMC and SMA) are detected independent of the baseline condition, the activation in right vPMC, bilateral caudate nucleus, bilateral insula and right IFG is influenced by neural activity related to rest periods.

 


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