Abstract
The timing of networked brain activity subserving motion driven attention in humans is currently unclear. Functional MRI (fMRI)-neuronavigated chronometric transcranial magnetic stimulation (TMS) was used to investigate critical times of parietal cortex involvement in motion driven attention. In particular, we were interested in the relative critical times for two intraparietal sulcus (IPS) sites in comparison to that previously identified for motion processing in area V5, and to explore potential earlier times of involvement. fMRI was used to individually localize V5 and middle and posterior intraparietal sulcus (mIPS; pIPS) areas active for a motion driven attention task, prior to TMS neuronavigation. Paired-pulse TMS was applied during performance of the same task at stimulus onset asynchronies (SOAs) ranging from 0 to 180 ms. There were no statistically significant decreases in performance accuracy for trials where TMS was applied to V5 at any SOA, though stimulation intensity was lower for this site than for the parietal sites. For TMS applied to mIPS, there was a trend toward a relative decrease in performance accuracy at the 150 ms SOA, as well as a relative increase at 180 ms. There was no statistically significant effect overall of TMS applied to pIPS, however, there appeared a potential trend toward a decrease in performance at the 0 ms SOA. Overall, these results provide some patterns of potential theoretical interest to follow up in future studies.
Highlights
Speed of response to an oncoming obstacle is evolutionarily consequential
The current paper focuses on critical times of intraparietal sulcus (IPS) and V5 involvement in motion driven attention, while acknowledging the context of the complex systems in which these areas are functionally situated
For middle and posterior intraparietal sulcus (mIPS) transcranial magnetic stimulation (TMS), there was a significant effect of stimulus onset asynchronies (SOAs) with a large effect size, F(6,48) = 2.724, p = 0.023, η2 = 0.255 (Figure 3B)
Summary
Speed of response to an oncoming obstacle is evolutionarily consequential. research to better understand the neural mechanisms associated with motion driven attention networks in the human brain is theoretically important.Seminal hierarchical models of the visual system derived from work in macaque established an initial feedforward sweep of information from retina through thalamus and superior colliculus, Motion Driven Attention Investigated with TMS via primary visual cortex (V1) on to a range of increasingly higher order areas including parietal and temporal cortex (Van Essen and Maunsell, 1983; Felleman and Van Essen, 1991; Van Essen et al, 1992). In Bullier’s model, rapidly activated neurons with high conduction velocity axons and large receptive fields ‘retroinject’ approximate information about a visual scene onto neurons with small receptive fields, those in V1 and V2, thereby influencing or focusing the processing in such lower order areas. This mechanism may be consistent with the concept of attentional salience mapping or gain control (Saalmann et al, 2007) such as is attributed to lateral intraparietal area (LIP) in macaque (Bisley and Goldberg, 2003; Gottlieb, 2007). Investigating relative timing of LIP neurons in macaque, Saalmann et al (2007) found that in the first 300 ms poststimulus in a spatial attention task, activity in LIP could be shown to directly precede that in area MT in a percentage of trials. Ruff et al (2008) demonstrated top-down influence from parietal cortex in humans with concurrent transcranial magnetic stimulation-functional MRI (TMS-fMRI), finding that stimulation of parietal cortex led to BOLD activity changes in V1
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