| 1. |
- Koivisto, Mika, et al.
(författare)
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Subjective visual awareness emerges prior to P3
- 2016
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Ingår i: European Journal of Neuroscience. - : Wiley-Blackwell. - 0953-816X .- 1460-9568. ; 43:12, s. 1601-1611
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Tidskriftsartikel (refereegranskat)abstract
- Studies on the neural basis of visual awareness, the subjective experience of seeing, have found several potential neural corre- lates of visual awareness. Some of them may not directly correlate with awareness but with post-perceptual processes, such as reporting one’s awareness of the stimulus. We dissociated potential electrophysiological correlates of visual awareness from those occurring during response selection and thus co-occurring with post-perceptual processing. The participants performed two GO-NOGO conditions. In the aware-GO condition they responded with a key press when they were aware of the stimulus and withheld responding when they were unaware of it. In the unaware-GO condition they withheld responding when they were aware and responded when they were not aware of the stimulus. Thus, event-related potentials could be measured to aware and una- ware trials when responding was required and when not required. The results revealed that the N200 amplitude (180–280 ms) over the occipital and posterior temporal cortex was enhanced in aware trials as compared with trials without awareness. This effect (visual awareness negativity, VAN) did not depend on responding. The amplitude of P3 (350–450 ms) also was enhanced in aware trials as compared with unaware trials. In addition, the amplitudes in the P3 time window depended on responding: they were greater when awareness was mapped to GO-response than when not, suggesting that P3 reflects post-perceptual process- ing, that is, it occurs after awareness has emerged. These findings support theories of visual awareness that assume a relatively early onset of visual awareness before P3.
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| 2. |
- Koivisto, Mika, et al.
(författare)
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Unconscious response priming by shape depends on geniculostriate visual projection
- 2012
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Ingår i: European Journal of Neuroscience. - : Wiley-Blackwell. - 0953-816X .- 1460-9568. ; 35:4, s. 623-633
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that unconscious visual processing of some stimulus features might occur without the contribution of early visual cortex (V1/V2). In the present study, the causal role of V1/V2 in unconscious processing of simple shapes in intact human brain was studied by applying transcranial magnetic stimulation (TMS) on early visual cortex or lateral occipital cortex (LO) while observers performed a metacontrast-masked response priming task with arrow figures as visual stimuli. Magnetic stimulation of V1/V2 impaired masked priming 3090 ms after the onset of the prime. Stimulation of LO reduced the magnitude of masked priming at 90120 ms, but this effect occurred only in the early parts of the priming experiment. A control task measuring the visibility of masked primes indicated that the orientation of masked primes could not be consciously discriminated and that TMS did not influence the conscious visibility of the primes indirectly by reducing the effectiveness of the mask in the critical time windows. We conclude that feedforward sweep of processing from V1/V2 (3090 ms) to LO (90 ms and above) is necessary for unconscious priming of shape, whereas conscious perception requires also the contribution of recurrent (feedback) processing.
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| 3. |
- Nilsson, Martin, et al.
(författare)
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Region‐of‐interest analysis approaches in neuroimaging studies of body ownership : An activation likelihood estimation meta‐analysis
- 2021
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Ingår i: European Journal of Neuroscience. - : John Wiley & Sons. - 0953-816X .- 1460-9568. ; 54:11, s. 7974-7988
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Tidskriftsartikel (refereegranskat)abstract
- How do we feel that we own our body? By manipulating the integration of multisensory signals and creating the illusory experience of owning external body parts and entire bodies, researchers have investigated the neurofunctional correlates of body ownership. Recent attempts to synthesize the neuroimaging literature of body ownership through meta-analysis have shown partly inconsistent results. A large proportion of functional magnetic resonance imaging (fMRI) findings on body ownership include analyses based on regions of interest (ROIs). This approach can produce inflated findings when results are synthesized in meta-analyses. We conducted a systematic search of the fMRI literature of ownership of body parts and entire bodies. Three activation likelihood estimation (ALE) meta-analyses were conducted, testing the impact of including ROI-based findings. When both whole-brain and ROI-based results were included, frontal and posterior parietal multisensory areas were associated with body ownership. When only ROI-based results were included, larger areas of the frontal and posterior parietal cortices and the middle occipital gyrus were associated with body ownership. A whole-brain meta-analysis, excluding ROI-based results, found no significant convergence of activation across the brain. These findings highlight the difficulty of quantitatively synthesizing a neuroimaging field where a large part of the literature is based on findings from ROI-based analyses. We discuss these findings in the light of current practices within this field of research and highlight current problems of meta-analytic approaches of body ownership. We recommend the sharing of unthresholded data as a means to facilitate future meta-analyses of the neuroimaging literature of body ownership.
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