Constructing the mammalian neocortex: the role of intrinsic factors.
The mammalian neocortex is subdivided into regions that are specialised for the processing of particular forms of information. These regions are distinct in terms of their cytoarchitecture, electrophysiology, and connectivity. How this regional diversity is generated through development is currently a topic of considerable interest and has centered upon two main issues. First, to what extent are these regions prespecified by intrinsic genetic mechanisms? Second, what is the influence of extrinsic activity in transmitting signals that ultimately shape functional regions? Historically, experimental evidence has tended to emphasise the role of extrinsic influences, but the identification and analysis of several genes that are expressed asymmetrically in the developing neocortex have tempered this viewpoint. We review current literature from the standpoint that intrinsic influences act early in neocortical development to generate molecular patterning whose main role is the guidance of long-range projections from the dorsal thalamus. Extrinsic influences appear to generate receptive fields for peripheral input, the summation of which determines the areal extent of particular neocortical region.
Brain Development Laboratory, Howard Florey Institute, The University of Melbourne, Parkville, Victoria, Australia.
Christopher
C
Job
Seong-Seng
SS
Tan
D000818:Animals; D000941:Antigens / Q000502:physiology; D001931:Brain Mapping; D051838:COUP Transcription Factor I; D015816:Cell Adhesion Molecules, Neuronal / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology; D005136:Eye Proteins; D058851:GPI-Linked Proteins; D018398:Homeodomain Proteins / Q000235:genetics / Q000502:physiology; D006801:Humans; D008322:Mammals; D051379:Mice; D008822:Mice, Transgenic; D008954:Models, Biological; D009024:Morphogenesis; D019579:Neocortex / Q000033:anatomy & histology* / Q000196:embryology* / Q000502:physiology; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D013788:Thalamus / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology; D000099260:Empty Spiracles Homeobox Proteins
D000941:Antigens; D051838:COUP Transcription Factor I; D015816:Cell Adhesion Molecules, Neuronal; D004268:DNA-Binding Proteins; D005136:Eye Proteins; D058851:GPI-Linked Proteins; D018398:Homeodomain Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D014157:Transcription Factors; D000099260:Empty Spiracles Homeobox Proteins; C084958:GBX2 protein, human; C513182:Gbx2 protein, mouse; C086812:Lxn protein, rat; C497589:NR2F1 protein, human; C497590:Nr2f1 protein, mouse; C000605730:PAX6 protein, human; C000605732:Pax6 protein, mouse; C000605733:Pax6 protein, rat; C095362:limbic system-associated membrane protein