Hello everyone! This is Matt from Kenhub, and in this tutorial, we are going to be looking at one of the commissures of the brain, the fornix.
The fornix is one of the commissural fibers of the cerebral hemispheres. So, what exactly are commissural fibers? Well, commissural fibers can be defined as a category of white matter of the cerebral hemispheres that connect identical areas of the cortices on the left and right side of the cerebral hemisphere. And although the fornix is one of the commissural fibers of the brain, its function is not limited to connecting two identical parts of the cerebral hemispheres.
Along with connecting identical areas across the two cerebral hemispheres, the fornix also serves to connect different structures that have common functions. Now, before we go into the function of the fornix, let's first look at the structure of the fornix.
The fornix is a C-shaped bundle of nerve fibers extending from the hippocampus to the mammillary bodies of the hypothalamus and the anterior nuclei of the thalamus forming an arch over the thalamus. The fornix is situated on both sides of the medial aspects of the cerebral hemispheres with its components lying on both sides of the midsagittal plane and connecting across the plane. It is comprised of the columns of the fornix anteriorly, a body which forms the midline part of the fornix and is suspended from the corpus callosum by the septum pellucidum, a posterior part known as the crura which further extends posteriorly as the alveus, and finally, the fimbriae of the hippocampus.
The primary function of the fornix is to connect the hippocampus to the mammillary bodies of the hypothalamus, the mammillary bodies to the anterior nuclei of the thalamus and the hippocampus to the septal nuclei and the nuclei accumbens.
The fornix forms an integral part of the limbic system. The limbic system is involved in motivation, learning, emotion, memory and other cognitive functions and it forms an area of the brain where the subcortical structures meet the cerebral cortex. The limbic system is comprised of numerous brain structures including the hippocampus, hypothalamus, thalamus, septal nuclei, the amygdala, the cingulate cortex, the entorhinal cortex, the perirhinal cortex, the parahippocampal cortex, the reticular formation of the midbrain, and the olfactory areas. The fornix is an integral part of the limbic system and it is important for the transfer of complex cognitive information between the cerebral hemispheres.
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