Is the prefrontal cortex necessary in conscious perception?
Poster No:
2466
Submission Type:
Abstract Submission
Authors:
Kavindu Bandara1, Elise Rowe2, Stefan Bode3, Marta Garrido4
Institutions:
1University of Melbourne, Carlton, Victoria, 2The University of Melbourne, MELBOURNE, VIC, 3University of Melbourne, Melbourne, Victoria, 4The University of Melbourne, Melbourne, Australia
First Author:
Co-Author(s):
Introduction:
The necessity of the prefrontal cortex (PFC) in generating consciousness remains a mystery. To date, empirical support has been largely mixed, with two theoretical camps suggesting two distinct brain regions involved in conscious perception. One family of theories (frontal theories) argues the PFC is necessary in the generation of consciousness, while the other (sensory theories) proposes that consciousness is accounted for by activity in posterior regions. Additionally, these sensory theories argue that PFC activity observed during conscious conditions may be contaminated by artefacts related to reporting one's percept – such as cognitive processes related to task-relevant processing (Tsuchiya et al., 2015).
Consciousness has typically been experimentally manipulated using various visual phenomena, such as inattentional blindness (IB). IB is a phenomenon in which a stimulus presented in plain sight fails to reach conscious perception in some participants (Mack, 2003). IB is a particularly useful paradigm for consciousness researchers as the information entering the visual system is kept constant across participants, yet the IB stimulus reaches awareness for some but remains subliminal for others. Thus, any differences in neural activity across aware and unaware groups in an IB experiment may be accounting for consciousness. Here, we re-analysed EEG data from a no-report inattentional blindness paradigm conducted by Shafto and Pitts (2015) to assess the role of the PFC in the conscious perception of faces.
Consciousness has typically been experimentally manipulated using various visual phenomena, such as inattentional blindness (IB). IB is a phenomenon in which a stimulus presented in plain sight fails to reach conscious perception in some participants (Mack, 2003). IB is a particularly useful paradigm for consciousness researchers as the information entering the visual system is kept constant across participants, yet the IB stimulus reaches awareness for some but remains subliminal for others. Thus, any differences in neural activity across aware and unaware groups in an IB experiment may be accounting for consciousness. Here, we re-analysed EEG data from a no-report inattentional blindness paradigm conducted by Shafto and Pitts (2015) to assess the role of the PFC in the conscious perception of faces.
Methods:
As shown in Figure 1, the task was designed to systematically manipulate awareness and task-relevance of face stimuli. Each phase was the same, with the only difference being experimental instructions, and all 30 participants completed the same experiment.
In order to adjudicate between these theories we used DCM, a technique which enables estimating the directed influence that a brain region has on another (David et al., 2005). DCM begins with an anatomically-informed generative model to simulate neural time series (EEG) data given some parameters (effective connectivity). Using a data-driven approach, we specified a neuronal network consisting of the left and right occipital, fusiform, and inferior frontal gyri. These regions were used as nodes in the DCM model and the model was fully connected at every level.
A second-level parametric empirical Bayes model was conducted over the modulatory connection parameters of the DCMs (Friston et al., 2016). This allowed us to estimate how connectivity was modulated at the group level across the main effects of awareness and task-relevancy.
In order to adjudicate between these theories we used DCM, a technique which enables estimating the directed influence that a brain region has on another (David et al., 2005). DCM begins with an anatomically-informed generative model to simulate neural time series (EEG) data given some parameters (effective connectivity). Using a data-driven approach, we specified a neuronal network consisting of the left and right occipital, fusiform, and inferior frontal gyri. These regions were used as nodes in the DCM model and the model was fully connected at every level.
A second-level parametric empirical Bayes model was conducted over the modulatory connection parameters of the DCMs (Friston et al., 2016). This allowed us to estimate how connectivity was modulated at the group level across the main effects of awareness and task-relevancy.
Results:
As shown in Figure 2, connectivity increased from right fusiform to the right PFC and decreased from the left PFC to the left occipital ROIs as a function of awareness (posterior probability > 0.95). This is surprising on multiple grounds. Firstly, various sensory theories predict feedback connectivity would increase under awareness within higher and lower-sensory regions – however this was not observed. Secondly, though frontal theories predict the PFC would increase feedback connectivity to sensory areas, instead a decrease was observed. Moreover, in line with neither theory, an increase in connectivity was observed from the right fusiform to the right PFC.
For the effect of task-relevancy, connectivity from the right fusiform to the right PFC decreased, while intrinsic connections to the right occipital, left PFC, and right PFC all increased. This was unexpected as both theories predict PFC connectivity to sensory regions should increase with task-relevancy.
For the effect of task-relevancy, connectivity from the right fusiform to the right PFC decreased, while intrinsic connections to the right occipital, left PFC, and right PFC all increased. This was unexpected as both theories predict PFC connectivity to sensory regions should increase with task-relevancy.
Conclusions:
While this study did not provide conclusive evidence to side with either family of theories, this study advances consciousness research forward toward establishing where the seat of consciousness lies in the brain. The PFC remains a critical point of contention among theories and establishing its role in conscious processing remains vital in isolating the neural basis of consciousness.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural) 2
EEG/MEG Modeling and Analysis
Novel Imaging Acquisition Methods:
EEG
Perception, Attention and Motor Behavior:
Consciousness and Awareness 1
Keywords:
Computational Neuroscience
Consciousness
Electroencephaolography (EEG)
Other - Dynamic Causal Modeling; Prefrontal Cortex;
1|2Indicates the priority used for review
·Figure 1
·Figure 2
Provide references using author date format
Dehaene, S. et al. (2006). Conscious, preconscious, and subliminal processing: A testable taxonomy. Trends in Cognitive Sciences, 10(5), 204–211. https://doi.org/10.1016/j.tics.2006.03.007
Friston, K. J. et al. (2016). Bayesian model reduction and empirical Bayes for group (DCM) studies. NeuroImage, 128, 413-431.
Mack, A. (2003). Inattentional blindness: Looking without seeing. Current Directions in Psychological Science, 12(5), 180–184. https://doi.org/10.1111/1467-8721.01256
Pitts, M., Metzler, S., & Hillyard, S. (2014). Isolating neural correlates of conscious perception from neural correlates of reporting one’s perception. Frontiers in Psychology, 5, 1078. https://doi.org/10.3389/fpsyg.2014.01078
Shafto, J. P. et al. (2015). Neural signatures of conscious face perception in an inattentional blindness paradigm. Journal of Neuroscience, 35(31), 10940–10948. https://doi.org/10.1523/JNEUROSCI.0145-15.2015
Tsuchiya, N. et al. (2015). No-report paradigms: Extracting the true neural correlates of consciousness. Trends in Cognitive Sciences, 19(12), 757–770. https://doi.org/10.1016/j.tics.2015.10.002