Neuroscience
You can’t possibly process everything that’s going on around you. Instead you’re armed with an attentional spotlight that selects areas and objects of interest for preferential processing. An anomalous consequence of this, is that we judge objects appearing where our attention is focused to have appeared earlier than objects located elsewhere, even if they really appeared at the same time. It could be that information arising from the attended object is transmitted through the brain’s sensory pathways more quickly than information arising from the unattended object, thus resulting in the perception that the attended stimulus occurred first. But now, using electroencephalography (EEG) to record electrical activity in the brain, John McDonald and colleagues refute this suggestion, arguing instead that selective attention increases the size of the neural signal arising from the attended object, not its speed.
Twenty-eight participants sat through hundreds of trials in which an irrelevant sound first grabbed their attention to the left or right, before two lights flashed up, one on their left, the other on their right. Consistent with past research, the light that flashed up on the same side as the sound (where the participants’ attention had been drawn to), was perceived to have occurred earlier than the other light, even if they had both appeared at the same time. However, EEG recordings of the brain’s electrical activity showed that although the light on the same side as the sound was perceived to have occurred earlier, it wasn’t processed more quickly in the brain. It was, however, associated with a larger neural signal (over the contra-lateral ventral occipital cortex), than the unattended light.
“…attention-induced effects on time-order perception may arise from changes in the strength of neural signals in ventral occipital areas that underlie visual object perception”, the authors said. “It follows from this hypothesis that attention-induced enhancements in signal strength that occur at early stages of visual processing are interpreted as a timing difference by a later comparator mechanism”.
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McDonald, J.J., Teder-Salejarvi, W.A., Russo, F.D. & Hillyard, S.A. (2005). Neural basis of auditory-induced shifts in visual time-order perception. Nature Neuroscience, Advance Online Publication: DOI: 10.1038/nn1512.
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
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Neuroscience
Judging what came first
You can’t possibly process everything that’s going on around you. Instead you’re armed with an attentional spotlight that selects areas and objects of interest for preferential processing. An anomalous consequence of this, is that we judge objects appearing where our attention is focused to have appeared earlier than objects located elsewhere, even if they really appeared at the same time. It could be that information arising from the attended object is transmitted through the brain’s sensory pathways more quickly than information arising from the unattended object, thus resulting in the perception that the attended stimulus occurred first. But now, using electroencephalography (EEG) to record electrical activity in the brain, John McDonald and colleagues refute this suggestion, arguing instead that selective attention increases the size of the neural signal arising from the attended object, not its speed.
Twenty-eight participants sat through hundreds of trials in which an irrelevant sound first grabbed their attention to the left or right, before two lights flashed up, one on their left, the other on their right. Consistent with past research, the light that flashed up on the same side as the sound (where the participants’ attention had been drawn to), was perceived to have occurred earlier than the other light, even if they had both appeared at the same time. However, EEG recordings of the brain’s electrical activity showed that although the light on the same side as the sound was perceived to have occurred earlier, it wasn’t processed more quickly in the brain. It was, however, associated with a larger neural signal (over the contra-lateral ventral occipital cortex), than the unattended light.
“…attention-induced effects on time-order perception may arise from changes in the strength of neural signals in ventral occipital areas that underlie visual object perception”, the authors said. “It follows from this hypothesis that attention-induced enhancements in signal strength that occur at early stages of visual processing are interpreted as a timing difference by a later comparator mechanism”.
_________________________________
McDonald, J.J., Teder-Salejarvi, W.A., Russo, F.D. & Hillyard, S.A. (2005). Neural basis of auditory-induced shifts in visual time-order perception. Nature Neuroscience, Advance Online Publication: DOI: 10.1038/nn1512.
Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.
- Early Visual Areas Of The Brain May Have A Role In Memory
The traditional view is that perceptual information is processed in early sensory regions of the brain, such as primary visual cortex, before being passed on to memory systems subserved by "high-order" brain areas, such as the prefrontal and inferotemporal...
- The Brain Invigorated By Light
Twenty minutes of bright white light delays sleepiness, and sends a stimulating wave through the brain, enhancing neural activity even during tasks that have nothing to do with vision. Gilles Vandewalle and colleagues used an optic fibre to shine bright...
- Paying Attention To What You're Ignoring
Because there’s too much information out there for us to process all at once, we have to selectively attend to some things at the expense of others. Indeed, psychologists have spent a lot of time examining how we select certain things for preferential...
- The Woman In The Mirror
Imagine if wherever you looked, you saw a translucent mirror image of yourself, about one metre in front of you. It’s wearing the same clothes as you and if you wave your right hand, it waves back in identical fashion (but with its left hand, just like...
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Attention (everyone knows what that1 is) is often described as having "bottom-up" and "top-down" components (referring to the direction of information flow from sensory to high-order cortical regions, and vice versa). ThinkGeek (bottoms up!) In a recent...