Related Experiment Videos
The neocortex. An overview of its evolutionary development, structural organization and synaptology
1Department of Anatomy and Embryology, University of Nijmegen, The Netherlands.
Anatomy and Embryology
|October 1, 1994
Summary
The evolution of the neocortex shows a progression from simple structures in reptiles to complex six-layered formations in mammals, primarily driven by the development of pyramidal neurons. These neurons form the core communication network within the neocortex.
Area of Science:
- Neuroscience
- Evolutionary Biology
- Comparative Anatomy
Background:
- The neocortex, a defining feature of mammalian brains, has evolved from simpler cortical structures found in reptiles.
- Neocortical neurons are broadly classified into pyramidal and nonpyramidal types, with pyramidal cells constituting the majority and playing a crucial role in neural circuitry.
Purpose of the Study:
- To outline the evolutionary origin and development of the neocortex.
- To describe the characteristics and evolutionary trajectory of neocortical pyramidal neurons.
Main Methods:
- Comparative analysis of cortical structures across different vertebrate classes (amphibians, reptiles, mammals).
- Morphological and functional characterization of neocortical neurons, particularly pyramidal cells.
- Tracing the evolutionary lineage of pyramidal neurons from ancestral forms to their mammalian counterparts.
Main Results:
- A three-layered cortex is present in reptiles, evolving into a six-layered neocortex in mammals, alongside two three-layered structures (prepiriform cortex and hippocampus).
- Pyramidal neurons, comprising at least 70% of neocortical cells, exhibit distinct morphological features and are central to neocortical communication.
- The evolutionary path of pyramidal neurons shows a progression from simpler 'extraverted' neurons in amphibians to complex 'psychic cells' in mammals, with variations and reductions observed in later stages.
Conclusions:
- The neocortex, particularly its six-layered structure and dominant pyramidal neurons, represents a significant evolutionary advancement in mammals.
- Pyramidal neurons are fundamental to neocortical function, forming extensive intra-cortical networks and serving as the source for other neuronal types.
- Understanding the evolution of pyramidal neurons provides insight into the development of complex cognitive functions associated with the mammalian neocortex.