Abnormal visual field maps in human cortex: a mini-review and a case report.
Human visual cortex contains maps of the visual field. Much research has been dedicated to answering whether and when these visual field maps change if critical components of the visual circuitry are damaged. Here, we first provide a focused mini-review of the functional magnetic resonance imaging (fMRI) studies that have evaluated the human cortical visual field maps in the face of retinal lesions, brain injury, and atypical retinocortical projections. We find that there is a fair body of research that has found abnormal fMRI activity, but also that this abnormal activity does not necessarily stem from cortical remapping. The abnormal fMRI activity can often be explained in terms of task effects and/or the uncovering of normally hidden system dynamics. We then present the case of a 16-year-old patient who lost the entire left cerebral hemisphere at age three for treatment of chronic focal encephalitis (Rasmussen syndrome) and intractable epilepsy. Using an fMRI retinotopic mapping procedure and population receptive field (pRF) modeling, we found that (1) despite the long period since the hemispherectomy, the retinotopic organization of early visual cortex remained unaffected by the removal of an entire cerebral hemisphere, and (2) the intact lateral occipital cortex contained an exceptionally large representation of the center of the visual field. The same method also indicates that the neuronal receptive fields in these lateral occipital brain regions are extraordinarily small. These features are clearly abnormal, but again they do not necessarily stem from cortical remapping. For example, the abnormal features can also be explained by the notion that the hemispherectomy took place during a critical period in the development of the lateral occipital cortex and therefore arrested its normal development. Thus, caution should be exercised when interpreting abnormal fMRI activity as a marker of cortical remapping; there are often other explanations.
Laboratory for Experimental Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; BCN Neuroimaging Center, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioral and Cognitive Neurosciences, University of Groningen, The Netherlands.
Koen V
KV
Haak
BCN Neuroimaging Center, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Otorhinolaryngology/Head and Neck Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioral and Cognitive Neurosciences, University of Groningen, The Netherlands.
Dave R M
DR
Langers
BCN Neuroimaging Center, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioral and Cognitive Neurosciences, University of Groningen, The Netherlands.
Remco
R
Renken
Department of Otorhinolaryngology/Head and Neck Surgery, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioral and Cognitive Neurosciences, University of Groningen, The Netherlands.
Pim
P
van Dijk
Sophia Children's Hospital, Erasmus University, Rotterdam, The Netherlands.
Johannes
J
Borgstein
Laboratory for Experimental Ophthalmology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; BCN Neuroimaging Center, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Graduate School of Medical Sciences, Research School of Behavioral and Cognitive Neurosciences, University of Groningen, The Netherlands. Electronic address: f.w.cornelissen@umcg.nl.
Frans W
FW
Cornelissen
D000293:Adolescent; D001931:Brain Mapping; D004827:Epilepsy / Q000503:physiopathology / Q000601:surgery; D007839:Functional Laterality / Q000502:physiology*; D038421:Hemispherectomy; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D010775:Photic Stimulation; D011612:Psychosurgery; D014793:Visual Cortex / Q000502:physiology* / Q000503:physiopathology; D014794:Visual Fields / Q000502:physiology*
Case report; Cortical reorganization; Hemispherectomy; Review; Visual field maps