Evidence for a monosynaptic connection between A1 and V1 in the human brain
Poster No:
1540
Submission Type:
Abstract Submission
Authors:
Samuel Paré1, James Lubell2, Sylvain Baillet3, Ron Kupers1, Maurice Ptito1
Institutions:
1Université de Montréal, Montréal, Quebec, 2University of Aarhus, Aarhus, Jutland, 3Montreal Neurological Institute, Montreal, Quebec
First Author:
Co-Author(s):
Introduction:
The conventional view of the visual cortex as a stimulus-driven, unimodal system with a hierarchical organization has been recently challenged (Qin & Yu, 2013). Both animal (Rockland & Ojima, 2003) and human (Ghazanfar & Schroeder, 2006) studies have demonstrated that the visual cortex responds to non-visual stimuli. However, the question as through which neural pathways non-visual information reaches the visual cortex is still a matter of debate. For instance, recent studies showed that tactile information can reach the visual cortex via a polysynaptic pathway between cortices (Ioannides et al., 2013; Müller et al., 2019). There is also evidence that auditory information may reach the occipital cortex (refs you showed before) but it is unclear whether this also involves a polysynaptic, or a monosynaptic, pathway. We took advantage of the millisecond time resolution of magnetoencephalography (MEG) to disentangle this question.
Methods:
Eighteen normal sighted control subjects participated in a MEG study in which we measured response latencies to monaural auditory stimulation in primary auditory cortex (A1), primary visual cortex (V1) and posterior thalamus, corresponding to the purported location of the lateral geniculate nucleus (LGN). Each trial began with an auditory cue (simple tone) presented to either the left or right ear, indicating participants to focus their attention on their left or right index finger, respectively. One second later, an electro-tactile stimulus was delivered to the left or right index finger (figure 1) and participants had to indicate as quickly as possible which hand had been stimulated. A part of the MEG data come from the Müller et al., (2019) study but we focus here on the time-locked responses to the preparatory auditory cue instead of the electro-tactile stimulus.
We used Brainstorm to preprocess the MEG data (Tadel et al., 2011). For source reconstruction, individual scalp and cortical surfaces were segmented from 3-D MRI data, using Freesurfer (Fischl, 2012). We used MEG forward and inverse modeling steps for source reconstruction that were subsequently completed with multi-sphere analytical approximation for head modeling and weighted minimum-norm estimation (wMNE) with unconstrained source orientation. Individual source data were then projected to the Colin27 brain template. To examine the time series of neural activity associated with auditory-visual connections, we used a multiple linear regression model that has increased sensitivity and consistency in detecting subcortical activity with MEG but is restricted to 3 or 4 ROIs (Coffey et al., 2016; Müller et al., 2019) which in our case, were posterior thalamus, A1 and V1.
We used Brainstorm to preprocess the MEG data (Tadel et al., 2011). For source reconstruction, individual scalp and cortical surfaces were segmented from 3-D MRI data, using Freesurfer (Fischl, 2012). We used MEG forward and inverse modeling steps for source reconstruction that were subsequently completed with multi-sphere analytical approximation for head modeling and weighted minimum-norm estimation (wMNE) with unconstrained source orientation. Individual source data were then projected to the Colin27 brain template. To examine the time series of neural activity associated with auditory-visual connections, we used a multiple linear regression model that has increased sensitivity and consistency in detecting subcortical activity with MEG but is restricted to 3 or 4 ROIs (Coffey et al., 2016; Müller et al., 2019) which in our case, were posterior thalamus, A1 and V1.
Results:
We found evidence for a distinct sequential activation pattern following a monaural auditory cue starting from the thalamus between 10-20 ms, followed by activity in A1 as early as 35 ms, and culminating in V1 10 to 15 ms later (50 ms post auditory cue) in both contralateral and ipsilateral hemispheres relative to the auditory cue.
Conclusions:
Considering that the monosynaptic transmission of information from one cortical area to another typically occurs within a time frame of approximately 10–15 ms (Molholm et al., 2002), this sequence of events suggests that in the human brain, auditory inputs reach the visual cortex via a monosynaptic A1-V1 connection. This is clearly distinct from our previous data which showed that tactile information is funneled to the occipital cortex via a polysynaptic pathway.
Supported by the Canadian Institutes of Health Research (CIHR 163014-2019).
Supported by the Canadian Institutes of Health Research (CIHR 163014-2019).
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural) 1
EEG/MEG Modeling and Analysis
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
Anatomy and Functional Systems 2
Cortical Anatomy and Brain Mapping
Normal Development
Keywords:
ADULTS
Cortex
MEG
MRI
NORMAL HUMAN
Source Localization
Structures
Vision
Other - Audition, Connectivity, Auditory-visual integration
1|2Indicates the priority used for review
Provide references using author date format
Coffey, E. B., Herholz, S. C., Chepesiuk, A. M., Baillet, S., & Zatorre, R. J. (2016). Cortical contributions to the auditory frequency-following response revealed by MEG. Nature communications, 7(1), 1-11.
Fischl, B. (2012). FreeSurfer. Neuroimage, 62(2), 774-781.
Ghazanfar, A. A., & Schroeder, C. E. (2006). Is neocortex essentially multisensory? Trends in cognitive sciences, 10(6), 278-285.
Ioannides, A. A., Liu, L., Poghosyan, V., Saridis, G. A., Gjedde, A., Ptito, M., & Kupers, R. (2013). MEG reveals a fast pathway from somatosensory cortex to occipital areas via posterior parietal cortex in a blind subject. Frontiers in human neuroscience, 7, 429.
Molholm, S., Ritter, W., Murray, M. M., Javitt, D. C., Schroeder, C. E., & Foxe, J. J. (2002). Multisensory auditory–visual interactions during early sensory processing in humans: a high-density electrical mapping study. Cognitive Brain Research, 14(1), 115-128.
Müller, F., Niso, G., Samiee, S., Ptito, M., Baillet, S., & Kupers, R. (2019). A thalamocortical pathway for fast rerouting of tactile information to occipital cortex in congenital blindness. Nature communications, 10(1), 1-9.
Qin, W., & Yu, C. (2013). Neural pathways conveying novisual information to the visual cortex. Neural plasticity, 2013.
Rockland, K. S., & Ojima, H. (2003). Multisensory convergence in calcarine visual areas in macaque monkey. International Journal of Psychophysiology, 50(1-2), 19-26.
Tadel, F., Baillet, S., Mosher, J. C., Pantazis, D., & Leahy, R. M. (2011). Brainstorm: a user-friendly application for MEG/EEG analysis. Computational intelligence and neuroscience, 2011.