A Soft Handoff of Attention between Cerebral Hemispheres

Abstract

SummaryEach cerebral hemisphere initially processes one half of the visual world. How are moving objects seamlessly tracked when they traverse visual hemifields? Covertly tracking lateralized objects evokes a difference between slow wave electrophysiological activity observed from contralateral and ipsilateral electrodes in occipto-parietal regions. This ERP waveform, known as Contralateral Delay Activity (CDA) [1,2], is sensitive to the number of objects tracked [1,2], and responds dynamically to changes in this quantity [3]. When a tracked object crosses the midline, an inversion in CDA polarity revealed the dropping of the object's representation by one hemisphere and its acquisition by the other. Importantly, our data suggest that the initially tracking hemisphere continues to represent the object for a period after that object crosses the midline. Meanwhile, the receiving hemisphere begins to represent the object before the object crosses the midline, leading to a period in which the object is represented by both hemispheres. Further, this overlap in representation is reduced if the midline crossing is unpredictable. Thus, this process is sensitive to observer expectations and does not simply reflect overlapping receptive fields near the midline. Results and DiscussionWe recorded event-related potentials (ERPs) from healthy young adults as they covertly tracked a vertically or horizontally moving object while holding central fixation (see Supplemental Materials for additional information on eye-movements). As shown in Fig 1A, on each trial, a pair of objects was presented in each quadrant. A brief (500 ms) cue informed the observer which object to track. ERP waveforms were time-locked to the onset

Singularity and consciousness: A neuropsychological contribution

“…In contrast to the claims stating that 'change blindness' is driven by consciousness bottlenecks, it is evident that you experience a lot of visual information at the same time without needing attention. Parallel processing even occurs in attention as has been shown by 'multiple object tracking' studies Drew, Mance, Horowitz, Wolfe, & Vogel, 2014) and 'functional split-brain' (Sasai et al, 2016) investigations. In all these perceptual examples, there is no place in the brain where all the visual information comes together.…”