PT - JOURNAL ARTICLE AU - Daniel P. Newman AU - Gerard M. Loughnane AU - Simon P. Kelly AU - Redmond G O'Connell AU - Mark A Bellgrove TI - Visuospatial asymmetries arise from differences in the onset time of perceptual evidence accumulation AID - 10.1523/JNEUROSCI.3512-16.2017 DP - 2017 Feb 27 TA - The Journal of Neuroscience PG - 3512-16 4099 - http://www.jneurosci.org/content/early/2017/02/27/JNEUROSCI.3512-16.2017.short 4100 - http://www.jneurosci.org/content/early/2017/02/27/JNEUROSCI.3512-16.2017.full AB - Healthy subjects tend to exhibit a bias of visual attention whereby left hemifield stimuli are processed more quickly and accurately than stimuli appearing in the right hemifield. It has long been held that this phenomenon arises from the dominant role of the right cerebral hemisphere in regulating attention, however, methods that would allow for a more precise understanding of the mechanisms underpinning visuospatial bias have remained elusive. We sought to finely trace the temporal evolution of spatial biases by leveraging a novel bilateral dot motion detection paradigm. In combination with electroencephalography (EEG), this paradigm enables isolation of discrete neural signals reflecting the key neural processes needed for making these detection decisions; including spatial attention, early target selection, evidence accumulation and motor preparation. Using this method we established that three key neural markers accounted for unique between-subject variation in visuospatial bias: hemispheric asymmetry in posterior alpha power measured prior to target onset which is related to the distribution of preparatory attention across the visual field; asymmetry in the peak latency of the early N2c target selection signal and, finally, asymmetry in the onset time of the subsequent neural evidence accumulation process with earlier onsets for left hemifield targets. Our development of a single paradigm to dissociate distinct processing components that track the temporal evolution of spatial biases not only advances our understanding of the neural mechanisms underpinning normal visuospatial attention bias, but may also in the future aid differential diagnoses in disorders of spatial attention.Significance StatementThe significance of this research is twofold. First, it shows that individual differences in how humans direct their attention between left and right space reflects physiological differences in how early the brain starts to accumulate evidence for the existence of a visual target. Second, the novel methods developed here may have particular relevance to disorders of attention, such as unilateral spatial neglect. In the case of spatial neglect, pathological inattention to left space could have multiple underlying causes including biased attention, impaired decision formation, or a motor deficit related to one side of space. Our development of a single paradigm to dissociate each of these components may aid differential diagnosis in such heterogeneous disorders to an unprecedented level.