The multisensory function of the human primary visual cortex.
It has been nearly 10 years since Ghazanfar and Schroeder (2006) proposed that the neocortex is essentially multisensory in nature. However, it is only recently that sufficient and hard evidence that supports this proposal has accrued. We review evidence that activity within the human primary visual cortex plays an active role in multisensory processes and directly impacts behavioural outcome. This evidence emerges from a full pallet of human brain imaging and brain mapping methods with which multisensory processes are quantitatively assessed by taking advantage of particular strengths of each technique as well as advances in signal analyses. Several general conclusions about multisensory processes in primary visual cortex of humans are supported relatively solidly. First, haemodynamic methods (fMRI/PET) show that there is both convergence and integration occurring within primary visual cortex. Second, primary visual cortex is involved in multisensory processes during early post-stimulus stages (as revealed by EEG/ERP/ERFs as well as TMS). Third, multisensory effects in primary visual cortex directly impact behaviour and perception, as revealed by correlational (EEG/ERPs/ERFs) as well as more causal measures (TMS/tACS). While the provocative claim of Ghazanfar and Schroeder (2006) that the whole of neocortex is multisensory in function has yet to be demonstrated, this can now be considered established in the case of the human primary visual cortex.
The Laboratory for Investigative Neurophysiology (The LINE), Neuropsychology and Neurorehabilitation Service and Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; EEG Brain Mapping Core, Center for Biomedical Imaging (CIBM) of Lausanne and Geneva, Lausanne, Switzerland; Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA. Electronic address: micah.murray@chuv.ch.
Micah M
MM
Murray
Department of Hearing and Speech Sciences, Vanderbilt University Medical Center, Nashville, TN, USA.
Antonia
A
Thelen
Centre for Cognitive Neuroimaging, Institute of Neuroscience and Psychology, University of Glasgow, Glasgow G12 8QB, United Kingdom.
Gregor
G
Thut
Centre for Brain Science, Department of Psychology, University of Essex, Colchester, United Kingdom.
Vincenzo
V
Romei
Laboratory of Cognitive Neuroscience, Brain-Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Switzerland.
Roberto
R
Martuzzi
The Laboratory for Investigative Neurophysiology (The LINE), Neuropsychology and Neurorehabilitation Service and Department of Radiology, University Hospital Center and University of Lausanne, Lausanne, Switzerland; Attention, Brain, and Cognitive Development Group, Department of Experimental Psychology, University of Oxford, United Kingdom. Electronic address: pawel.matusz@chuv.ch.
Pawel J
PJ
Matusz
D000344:Afferent Pathways / Q000502:physiology*; D001931:Brain Mapping; D006801:Humans; D059906:Neuroimaging; D010465:Perception / Q000502:physiology*; D010812:Physical Stimulation; D014793:Visual Cortex / Q000098:blood supply / Q000502:physiology*
Brain imaging; Brain mapping; Cross-modal; Humans; Multisensory; Primary cortex; Vision