John O’Keefe (b. 1939)
Andrew P. Wickens in Key Thinkers in Neuroscience, 2018
John O'Keefe is a Nobel winning neuroscientist, who is famous for his discovery of place cells in the hippocampus – neurons that encode an animal's location in its geographic space and which are involved in navigation and creating a cognitive map of the environment. O'Keefe and Nadel suggested that similar hippocampal neural mechanisms might underlie other types of cognition including episodic memory and even the deep structure of language. O'Keefe is optimistic that an understanding of the hippocampus will allow us to find out more about Alzheimer's disease, and to this end, is intent on developing mouse models of place cell function to show how hippocampus physiology can become dysfunctional during disease progression. Convincing evidence that hippocampal place cells utilise landmark-based information that is dependent on the array of spatial cues came from a study O'Keefe performed with research student Dulcie Conway.
Drug abuse
William T. Blows in The Biological Basis of Mental Health, 2016
Dementia means loss of mind' and is one of two mind-destroying disorders, the other being schizophrenia. Dementia with cortical Lewy bodies (DCLB) accounts for about 10" of all dementias, but about 20" of AD patients also have cortical Lewy bodies. The hippocampus is situated within the hippocampal fissure, close to the parahippocampal gyrus, part of the temporal lobes on both sides. This area is sometimes called the hippocampal complex or hippocampal formation, because several structures occur close together and have many interconnections with each other. The hippocampus has several important roles. These include the conversion of short-term memory to long-term memory and influencing thinking through connections with the frontal cortex. Pick's disease, also called frontotemporal dementia (FTD) or frontotemporal lobar degeneration (FTLD) was described in 1892 by Arnold Pick, earlier than the description of Alzheimer's disease.
Paul Donald MacLean (1913–2007)
Andrew P. Wickens in Key Thinkers in Neuroscience, 2018
Paul Donald MacLean is best known for identifying the limbic system with "visceral" emotional behaviour and for his theory that the mammalian brain has three evolutionary distinct anatomical parts, each with their own behavioural repertoire. MacLean began a research project assessing the bioelectrical activity of the anterior medial temporal lobe region that includes the hippocampus. MacLean was particularly interested in establishing what parts of the temporal lobes were triggering these emotions and designed nasopharyngeal electrodes that could be slipped up the sides of the nose, which lay only about 2 cm from the tissue of the anterior medial temporal lobe. These electrodes would show the seizure activity and emotionally charged auras most often arose from areas surrounding the hippocampal formation. In 1948, MacLean managed to spend a few days learning neuroanatomy in Papez's Cornell University laboratory – a visit he would describe as life-changing.
Proliferation, Migration, and Neuronal Differentiation of the Endogenous Neural Progenitors in Hippocampus after Fimbria Fornix Transection
Published in International Journal of Neuroscience, 2010
Linqing Zou, Guohua Jin, Xinhua Zhang, Jianbing Qin, Huixia Zhu, Meiling Tian, Xuefeng Tan
ABSTRACT Neurogenesis in the hippocampus continues throughout adult life and can be regulated by the local microenvironment. To determine whether denervation stimulates neurogenesis in hippocampus, proliferation, migration, and differentiation of local neural stem cells (NSCs) in dentate gyrus was investigated after fimbria fornix transection. In the denervated hippocampus, NSCs proliferated markedly and migrated along the subgranular layer, and more newborn cells differentiated into neurons or astrocytes. After denervation, more newborn cells in the deafferented hippocampus expressed Brn-4 and differentiated into β-Tubulin III positive neurons. It is concluded that the local NSCs in hippocampus may proliferate and migrate into granule cell layer, in which changes in the deafferented hippocampus provided a suitable microenvironment for hippocampal neurogenesis and the increased Brn-4 in denervated hippocampus may be involved in this process.
Functional connectivity of the posterior hippocampus is more dominant as we age
Published in Cognitive Neuroscience, 2014
Sonja Blum, Christian Habeck, Jason Steffener, Qolamreza Razlighi, Yaakov Stern
The role of the hippocampus in memory is dependent on its interaction with distributed brain areas. Anterior and posterior hippocampus have different roles in memory processing, and are impacted differently by aging in terms of structural decline, however, functional connectivity of these hippocampal regions in aging is not well understood. Young (age 17–30) and aging (age 60–69) cognitively normal subjects underwent resting-state functional MRI revealing a shift from anterior hippocampus dominant hippocampus connectivity in younger age group to posterior hippocampus dominant connectivity in aging subjects. We identified a subset of neocortical regions that are connected to the anterior hippocampus in younger adults but to the posterior hippocampus among older subjects, suggesting an age-related reorganization of hippocampal networks supporting normal cognitive function. We also performed volumetric analysis which revealed no significant structural differences between groups. These findings provide evidence that “functional anatomy” which supports normal memory performance changes across the life span.
Remembering and imagining differentially engage the hippocampus: A multivariate fMRI investigation
Published in Cognitive Neuroscience, 2014
C. Brock Kirwan, Stefania R. Ashby, Michelle I. Nash
It has been proposed that imagining the future depends on the ability to retrieve episodic details from past experiences in order to recombine them into novel possible experiences; consequently, the processes of remembering and imagining rely on similar neural substrates, including the hippocampus. We used fMRI and both univariate and multivariate analysis techniques to test this prediction. Unbiased univariate analysis did not reveal differences in the hippocampus between remembering and imagining; however, multivariate analyses revealed evidence that patterns of activity within the hippocampus distinguish between remembering and imagining. Thus, while the hippocampus seems to be involved in both remembering the past and imagining the future, the pattern of activity within the hippocampus distinguishes between these two different tasks.
Related Knowledge Centers
- Brain
- Cerebral Cortex
- Limbic System