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  • 1.
    Hurme, Mikko
    et al.
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Koivisto, Mika
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Revonsuo, Antti
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre. Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Railo, Henry
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Early processing in primary visual cortex is necessary for conscious and unconscious vision while late processing is necessary only for conscious vision in neurologically healthy humans2017In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 150, p. 230-238Article in journal (Refereed)
    Abstract [en]

    The neural mechanisms underlying conscious and unconscious visual processes remain controversial. Blindsight patients may process visual stimuli unconsciously despite their VI lesion, promoting anatomical models, which suggest that pathways bypassing the VI support unconscious vision. On the other hand, physiological models argue that the major geniculostriate pathway via VI is involved in both unconscious and conscious vision, but in different time windows and in different types of neural activity. According to physiological models, feedforward activity via VI to higher areas mediates unconscious processes whereas feedback loops of recurrent activity from higher areas back to VI support conscious vision. With transcranial magnetic stimulation (TMS) it is possible to study the causal role of a brain region during specific time points in neurologically healthy participants. In the present study, we measured unconscious processing with redundant target effect, a phenomenon where participants respond faster to two stimuli than one even when one of the stimuli is not consciously perceived. We tested the physiological feedforward-feedback model of vision by suppressing conscious vision by interfering selectively either with early or later VI activity with TMS. Our results show that early VI activity (60 ms) is necessary for both unconscious and conscious vision. During later processing stages (90 ms), VI contributes selectively to conscious vision. These findings support the feedforward-feedback-model of consciousness.

  • 2.
    Hurme, Mikko
    et al.
    Department of Psychology, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Koivisto, Mika
    Department of Psychology, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Revonsuo, Antti
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre. Department of Psychology, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland.
    Railo, Henry
    Department of Psychology, University of Turku, Finland / Turku Brain and Mind Centre, University of Turku, Finland / Department of Clinical Neurophysiology, University of Turku and Turku University Hospital, Finland.
    V1 activity during feedforward and early feedback processing is necessary for both conscious and unconscious motion perception2019In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 185, p. 313-321Article in journal (Refereed)
    Abstract [en]

    The study of blindsight has revealed a seminal dissociation between conscious vision and visually guided behavior: some patients who are blind due to V1 lesions seem to be able to employ unconscious visual information in their behavior. The standard assumption is that these findings generalize to the neurologically healthy. We tested whether unconscious processing of motion is possible without the contribution of V1 in neurologically healthy participants by disturbing activity in V1 using transcranial magnetic stimulation (TMS). Unconscious processing was measured with redundant target effect (RTE), a phenomenon where participants respond faster to two stimuli than to one stimulus, when the task is just to respond as fast as possible when one stimulus or two simultaneous stimuli are presented. We measured the RTE caused by a motion stimulus. V1 activity was interfered with different stimulus onset asynchronies (SOA) to test whether TMS delivered in a specific time window suppresses conscious perception (participant reports seeing only one of the two stimuli) but does not affect unconscious processing (RTE). We observed that at each SOA, when TMS suppressed conscious perception of the stimulus, the RTE was also eliminated. However, when visibility of the redundant target was suppressed with a visual mask, we found unconscious processing of motion. This suggests that unconscious processing of motion depends on V1 in neurologically healthy humans. We conclude that the neural mechanisms that enable motion processing in blindsight are modulated by neuroplastic changes in connectivity between subcortical areas and the visual cortex after the V1 lesion. Neurologically healthy observers cannot process motion unconsciously without functioning of V1. 

  • 3.
    Koivisto, Mika
    et al.
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland.
    Harjuniemi, Inari
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland.
    Railo, Henry
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland.
    Salminen-Vaparanta, Niina
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland.
    Revonsuo, Antti
    Department of Psychology, University of Turku, Finland / Centre for Cognitive Neuroscience, University of Turku, Finland.
    Transcranial magnetic stimulation of early visual cortex suppresses conscious representations in a dichotomous manner without gradually decreasing their precision2017In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 158, p. 308-318Article in journal (Refereed)
    Abstract [en]

    Transcranial magnetic stimulation (TMS) of early visual cortex can suppresses visual perception at early stages of processing. The suppression can be measured both with objective forced-choice tasks and with subjective ratings of visual awareness, but there is lack of objective evidence on how and whether the TMS influences the quality of representations. Does TMS decrease the precision of representations in graded manner, or does it lead to dichotomous, "all-or-nothing" suppression. We resolved this question by using a continuous measure of the perceptual error: the observers had to perceive the orientation of a target (Landort-C) and to adjust the orientation of a probe to match that of the target. Mixture modeling was applied to estimate the probability of guess trials and the standard deviation of the non-guess trials. TMS delivered 60-150 ms after stimulus-onset influenced only the guessing rate, whereas the standard deviation (i.e., precision) was not affected. This suggests that TMS suppressed representations dichotomously without affecting their precision. The guessing probability correlated with subjective visibility ratings, suggesting that it measured visual awareness. In a control experiment, manipulation of the stimulus contrast affected the standard deviation of the errors, indicating that contrast has a gradual influence on the precision of representations. The findings suggest that TMS of early visual cortex suppresses perception in dichotomous manner by decreasing the signal-to-noise ratio by increasing the noise level, whereas reduction of the signal level (i.e., contrast) decreases the precision of representations.

  • 4.
    van Meer, Floor
    et al.
    University Medical Center Utrecht, the Netherlands.
    van der Laan, Laura N.
    Tilburg University, the Netherlands.
    Eiben, Gabriele
    University of Skövde, School of Health and Education. University of Skövde, Health and Education.
    Lissner, Lauren
    Göteborg University, Sahlgrenska Academy, Gothenburg.
    Wolters, Maike
    Leibniz Institute for Prevention Research and Epidemiology, Bremen, Germany.
    Rach, Stefan
    Leibniz Institute for Prevention Research and Epidemiology, Bremen, Germany.
    Herrmann, Manfred
    University of Bremen, Germany.
    Erhard, Peter
    University of Bremen, Germany.
    Molnár, Dénés
    University Medical School of Pécs, Hungary.
    Orsi, Gergely
    University Medical School of Pécs, Hungary / MTA-PTE Clinical Neuroscience MR Research Group, Pécs, Hungary.
    Viergever, Max A.
    University Medical Center Utrecht, the Netherlands.
    Adan, Roger A.H.
    University Medical Center Utrecht, the Netherlands.
    Smeets, Paul A.M.
    University Medical Center Utrecht, the Netherlands / Division of Human Nutrition & Health, Wageningen University & Research, the Netherlands.
    Development and body mass inversely affect children's brain activation in dorsolateral prefrontal cortex during food choice2019In: NeuroImage, ISSN 1053-8119, E-ISSN 1095-9572, Vol. 201, p. 1-10, article id 116016Article in journal (Refereed)
    Abstract [en]

    Childhood obesity is a rising problem caused in part by unhealthy food choices. Food choices are based on a neural value signal encoded in the ventromedial prefrontal cortex, and self-control involves modulation of this signal by the dorsolateral prefrontal cortex (dlPFC). We determined the effects of development, body mass (BMI Cole score) and body mass history on the neural correlates of healthy food choice in children. 141 children (aged 10-17y) from Germany, Hungary and Sweden were scanned with fMRI while performing a food choice task. Afterwards health and taste ratings of the foods were collected. In the food choice task children were asked to consider the healthiness or tastiness of the food or to choose naturally. Overall, children made healthier choices when asked to consider healthiness. However, children who had a higher weight gain per year chose less healthy foods when considering healthiness but not when choosing naturally. Pubertal development stage correlated positively while current body mass correlated negatively with dlPFC activation when accepting foods. Pubertal development negatively and current body mass positively influenced the effect of considering healthiness on activation of brain areas involved in salience and motivation. In conclusion, children in earlier stages of pubertal development and children with a higher body weight exhibited less activation in the dlPFC, which has been implicated in self-control during food choice. Furthermore, pubertal development and body mass influenced neural responses to a health cue in areas involved in salience and motivation. Thus, these findings suggest that children in earlier stages of pubertal development, children with a higher body mass gain and children with overweight may possibly be less susceptible to healthy eating interventions that rely on self-control or that highlight health aspects of food. 

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