Update on Limbic Connections in Human Brain: A Possible Closer Relationship Between Brain Processes and Visceral Information
Journal Title: Radiology – Open Journal - Year 2017, Vol 2, Issue 1
Abstract
The limbic system includes cortical and subcortical brain structures involved in several functions, first of all emotional and memory processes and integration. Two key structures of the limbic network are hippocampus and amygdala; their connections with the other brain regions are allowed through a number of white matter pathways, including cingulum, uncinate fasciculus and fornix.1 All these pathways were studied by means of invasive approaches in animals as well as by means of MRI techniques, e.g. diffusion based tractography. These methods resulted very useful for the non-invasive study, in vivo, of these limbic brain connections,1 as well as to show new possible pathways, e.g. the cerebellar limbic one.2 Recently, new insights regarding possible limbic functions came from a study conducted by means of advanced tractographic algorithms.3 The main goal of the latter paper was to investigate subtentorial limbic connections in healthy humans; this was an interesting point, since these connections were previously investigated only in animals by means of viral tracing techniques.4 These previous studies revealed extensive connections of both amygdala and hippocampus with brainstem nuclei, as well as connections with the periphery of the body through spinal projections.5,6 By means of constrained spherical deconvolution (CSD)7 based tractography, Arrigo and colleagues3 reported and described hippocampal and amygdalar connections with midbrain, pons and bulb as well as connections with cervical spinal cord (Figure 1). These represented novel findings in humans, suggesting that functional speculation based on animals studies might be adopted also in human brain. Amygdalar connections with brainstem were proposed to be related with faster answers to fear stimuli, in order to establish a more efficient alerting mechanism.8-10Based on findings provided by animal studies, other authors proposed a role of amygdalar-brainstem pathways in the visceral control as well as in the control of the appetite.11,12 With respect to hippocampal-brainstem pathways, these were previously reported in animals13,14; those results allowed to advance the hypothesis of a larger learning and memory connectivity network, involving also brainstem structures, which might influence the limbic system during memory and learning elaboration.
Authors and Affiliations
Alessandro Arrigo
Keywords
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- EP ID EP554302
- DOI 10.17140/ROJ-2-e004
- Views 111
- Downloads 0
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