The hippocampus is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, and plays important roles in the consolidation of information from short-term memory to long-term memory, and in spatial memory that enables navigation. The hippocampus is located under the cerebral cortex in the allocortex, and in primates it is in the medial temporal lobe. It contains two main interlocking parts: the hippocampus proper and the dentate gyrus.
Neuropil is any area in the nervous system composed of mostly unmyelinated axons, dendrites and glial cell processes that forms a synaptically dense region containing a relatively low number of cell bodies. The most prevalent anatomical region of neuropil is the brain which, although not completely composed of neuropil, does have the largest and highest synaptically-concentrated areas of neuropil in the body. For example, the neocortex and olfactory bulb both contain neuropil.
The neocortex, also called the neopallium and isocortex, is the part of the mammalian brain involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, spatial reasoning and language.
The triune brain is a model of the evolution of the vertebrate forebrain and behavior, proposed by the American physician and neuroscientist Paul D. MacLean. MacLean originally formulated his model in the 1960s and propounded it at length in his 1990 book The Triune Brain in Evolution. The triune brain consists of the reptilian complex, the paleomammalian complex, and the neomammalian complex (neocortex), viewed as structures sequentially added to the forebrain in the course of evolution. However, this hypothesis is no longer espoused by the majority of comparative neuroscientists in the post-2000 era. The triune brain hypothesis became familiar to a broad popular audience through Carl Sagan's Pulitzer prize winning 1977 book The Dragons of Eden. The theory has been embraced by some psychiatrists and at least one leading affective neuroscience researcher.
A cortical minicolumn is a vertical column through the cortical layers of the brain. Neurons within the microcolumn "receive common inputs, have common outputs, are interconnected, and may well constitute a fundamental computational unit of the cerebral cortex". Minicolumns comprise perhaps 80–120 neurons, except in the primate primary visual cortex (V1), where there are typically more than twice the number. There are about 2×108 minicolumns in humans. From calculations, the diameter of a minicolumn is about 28–40 µm. Minicolumns grow from progenitor cells within the embryo and contain neurons within multiple layers (2–6) of the cortex.
A cortical column, also called hypercolumn, macrocolumn, functional column or sometimes cortical module, is a group of neurons in the cortex of the brain that can be successively penetrated by a probe inserted perpendicularly to the cortical surface, and which have nearly identical receptive fields. Neurons within a minicolumn (microcolumn) encode similar features, whereas a hypercolumn "denotes a unit containing a full set of values for any given set of receptive field parameters". A cortical module is defined as either synonymous with a hypercolumn (Mountcastle) or as a tissue block of multiple overlapping hypercolumns.
On Intelligence: How a New Understanding of the Brain will Lead to the Creation of Truly Intelligent Machines is a 2004 book by Palm Pilot-inventor Jeff Hawkins with New York Times science writer Sandra Blakeslee. The book explains Hawkins' memory-prediction framework theory of the brain and describes some of its consequences.
In anatomy of animals, the archicortex or archipallium is the phylogenetically oldest region of the brain's pallium or cortex.
The allocortex is one of the two types of cerebral cortex, the other being the neocortex. It is characterized by having just three or four cell layers, in contrast with the six layers of the neocortex, and takes up a much smaller area than the neocortex. There are three subtypes of allocortex: the paleocortex, the archicortex, and the periallocortex – a transitional zone between the neocortex and the allocortex.
Pasko Rakic is a Yugoslav-born American neuroscientist, who presently works in the Yale School of Medicine Department of Neuroscience in New Haven, Connecticut. His main research interest is in the development and evolution of the human brain. He was the founder and served as Chairman of the Department of Neurobiology at Yale, and was founder and Director of the Kavli Institute for Neuroscience. He is best known for elucidating the mechanisms involved in development and evolution of the cerebral cortex. In 2008, Rakic shared the inaugural Kavli Prize in Neuroscience. He is currently the Dorys McConell Duberg Professor of Neuroscience, leads an active research laboratory, and serves on Advisory Boards and Scientific Councils of a number of Institutions and Research Foundations.
In anatomy of animals, the paleocortex, or paleopallium is a region within the telencephalon in the brain which is older in an evolutionary sense than the archicortex and the neocortex.
Hierarchical temporal memory (HTM) is a biologically constrained theory of intelligence, originally described in the 2004 book On Intelligence by Jeff Hawkins with Sandra Blakeslee. HTM is based on neuroscience and the physiology and interaction of pyramidal neurons in the neocortex of the mammalian brain.
The paralimbic cortex is an area of three-layered cortex that includes the following regions: the piriform cortex, entorhinal cortex, the parahippocampal cortex on the medial surface of the temporal lobe, and the cingulate cortex just above the corpus callosum.
The ganglionic eminence (GE) is a transitory structure in the development of the nervous system that guides cell and axon migration. It is present in the embryonic and fetal stages of neural development found between the thalamus and caudate nucleus. The eminence is divided into three regions of the ventral ventricular zone of the telencephalon, where they facilitate tangential cell migration during embryonic development. Tangential migration does not involve interactions with radial glial cells; instead the interneurons migrate perpendicularly through the radial glial cells to reach their final location. The characteristics and function of the cells that follow the tangential migration pathway seem to be closely related to the location and precise timing of their production, and the GEs contribute significantly to building up the GABAergic cortical cell population. Another structure that the GEs contribute to is the basal ganglia. The GEs also guide the axons growing from the thalamus into the cortex and vice versa. In humans, the GEs disappear by one year of age. During development, neuronal migration continues until the extinction of the germ layer, at which point the remnants from the germ layer make up the eminences.
Gyrification is the process of forming the characteristic folds of the cerebral cortex. The peak of such a fold is called a gyrus, and its trough is called a sulcus. The neurons of the cerebral cortex reside in a thin layer of gray matter, only 2–4 mm thick, at the surface of the brain. Much of the interior volume is occupied by white matter, which consists of long axonal projections to and from the cortical neurons residing near the surface. Gyrification allows a larger cortical surface area and hence greater cognitive functionality to fit inside a smaller cranium. In most mammals, gyrification begins during fetal development. Primates, cetaceans, and ungulates have extensive cortical gyri, with a few species exceptions, while rodents generally have none. Gyrification in some animals, for example the ferret, continues well into postnatal life.
Leah Krubitzer is an American neuroscientist, Professor of Psychology at University of California, Davis, and head of the Laboratory of Evolutionary Neurobiology. Her research interests center on how complex brains in mammals evolve from simpler forms. To do this, she focuses on anatomical connections and electrophysiological characteristics of neurons in the neocortex. Using comparative studies, she determines which features of the neocortex are shared by all mammals and how new features of the neocortex have evolved. This allows her to reconstruct evolutionary phylogenies of the neocortex together with their relationship to functional changes. Thus, her work aims to explain the diversity in mammalian behavioral and perceptual abilities by investigating how evolutionarily old developmental mechanisms constrain evolutionary change while also providing the variation needed for the evolution of the diversity of brains found in mammals.
Sharp waves and ripples (SWRs) are oscillatory patterns in the mammalian brain hippocampus seen on an EEG during immobility and sleep. There are three major network oscillation patterns in the hippocampus: theta waves, SWRs and gamma waves. Gamma oscillations are found in all major brain structures, whereas theta and sharp waves are specific to the hippocampus and its neighbouring areas. SWRs are composed of large amplitude sharp waves in local field potential and associated fast field oscillations known as ripples. SWRs are shown to be involved in memory consolidation and the replay of wakefulness-acquired memory. These network oscillations are the most synchronous patterns in the brain, making them susceptible to pathological patterns such as epilepsy.
In vertebrate organisms, the ventricular zone (VZ) is a transient embryonic layer of tissue containing neural stem cells, principally radial glial cells, of the central nervous system (CNS). The VZ is so named because it lines the ventricular system, which contains cerebrospinal fluid (CSF). The embryonic ventricular system contains growth factors and other nutrients needed for the proper function of neural stem cells. Neurogenesis, or the generation of neurons, occurs in the VZ during embryonic and fetal development as a function of the Notch pathway, and the newborn neurons must migrate substantial distances to their final destination in the developing brain or spinal cord where they will establish neural circuits. A secondary proliferative zone, the subventricular zone (SVZ), lies adjacent to the VZ. In the embryonic cerebral cortex, the SVZ contains intermediate neuronal progenitors that continue to divide into post-mitotic neurons. Through the process of neurogenesis, the parent neural stem cell pool is depleted and the VZ disappears. The balance between the rates of stem cell proliferation and neurogenesis changes during development, and species from mouse to human show large differences in the number of cell cycles, cell cycle length, and other parameters, which is thought to give rise to the large diversity in brain size and structure.
The neomammalian brain is one of three aspects of Paul MacLean’s Triune Theory of the human brain. MacLean was an American physician and neuroscientist that formulated his model in the 1960s, which was published in his own 1990 book ‘The Triune Brain in Evolution’ 2. MacLean’s three-part theory explores how the human brain has evolved from ancestors over millions of years, consisting of the reptilian, paleomammalian and neomammalian complexes. 25 MacLean proposes that the neomammalian complex is only found in higher order mammals,4 for example, the human brain, accounting for increased cognitive ability such as motor control, memory, improved reasoning and complex decision making 1
