Entire set is called as hippocampal formation. Some anatomists divide it into hippocampus proper (Cornu ammonis CA), dentate gyrus (DG), subiculum, and entorhinal area (EC). Since hippocampus is a part of allocortex (archicortex), there is a zone that separates it from neocortex. Both of these parts are separated by hippocampal sulcus and curve into each other. Hippocampus contains two parts: Cornu ammonis (hippocampus proper) and dentate gyrus. Additionally though, known to play a major role in learning, memory and spatial navigation studies also indicate that this is increasingly emerging as a part of ‘moral brain.’ It has also been now implicated in recollecting the past experience and imagining future. Papez (1930) proposed that emotional response is organized in hippocampus and is expressed in cingulate gyrus via mammillary bodies. Thus, hippocampus is 100 times smaller in volume compared to cerebral cortex. In adult humans, the volume of the hippocampus on each side of the brain is about 3-3.5 cm 3 as compared to 320-420 cm 3 for the volume of the neocortex. Hippocampus is the posterior part of limbic lobe while frontal part is amygdala. It is concerned with hunger, motivation, sex drive, mood, pain, pleasure, appetite, and memory etc. Limbic system is considered to be a “primitive brain,” deep with-in brain. It is the earliest and most severely affected structure in several neuropsychiatric disorders such as Alzheimer's disease (AD), epilepsy etc. This part of brain has been one of the most extensively studied, and atrophy of this region has clinical consequence both potential and real. Note that hippocampus is a C-shaped structure having amygdaloid body at its anterior end, culminating deep into mammillary bodies ( Figure: courtesy AITBS publishers India) Relationship between limbic system and hippocampus.
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