The subiculum (

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

for "support") is the most inferior component of the hippocampal formation. It lies between the

entorhinal cortex The entorhinal cortex (EC) is an area of the brain's allocortex, located in the medial temporal lobe, whose functions include being a widespread network hub for memory, navigation, and the perception of time.Integrating time from experience in ...

and the CA1 subfield of the hippocampus proper. The subicular complex comprises a set of related structures including (as well as subiculum proper) prosubiculum, presubiculum, postsubiculum and parasubiculum.

Name

The subiculum got its name from Karl Friedrich Burdach in his three-volume work ''Vom Bau und Leben des Gehirns'' (Vol. 2, §199). He originally named it subiculum cornu ammonis and so associated it with the rest of the hippocampal subfields.

Structure

It receives input from CA1 and entorhinal cortical layer III pyramidal neurons and is the main output of the hippocampus. The pyramidal neurons send projections to the nucleus accumbens, septal nuclei,

prefrontal cortex In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA ...

lateral hypothalamus The lateral hypothalamus (LH), also called the lateral hypothalamic area (LHA), contains the primary orexinergic nucleus within the hypothalamus that widely projects throughout the nervous system; this system of neurons mediates an array of cogn ...

nucleus reuniens The nucleus reuniens is a region of the thalamic midline nuclear group. In the human brain, it is located in the interthalamic adhesion (''massa intermedia''). The nucleus reuniens receives afferent input from a large number of structures, main ...

, mammillary nuclei,

and

amygdala The amygdala (; plural: amygdalae or amygdalas; also '; Latin from Greek, , ', 'almond', 'tonsil') is one of two almond-shaped clusters of nuclei located deep and medially within the temporal lobes of the brain's cerebrum in complex v ...

. The pyramidal neurons in the subiculum exhibit transitions between two modes of

action potential An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...

output:

bursting Bursting, or burst firing, is an extremely diverse general phenomenon of the activation patterns of neurons in the central nervous system and spinal cord where periods of rapid action potential spiking are followed by quiescent periods much longer ...

and single spiking. The transitions between these two modes is thought to be important for routing information out of the hippocampus. Four component areas have been described: parasubiculum (adjacent to the parahippocampal gyrus), presubiculum, postsubiculum, and prosubiculum.

Parasubiculum

The parasubiculum contains grid cells, which are neurons responsive to movements in particular directions over particular distances.

Presubiculum

The presubiculum is part of the posterior cortex corresponding to Brodmann area 27, and forms part of the cortical input to the entorhinal-hippocampal spatial/memory system.

Postsubiculum

The dorsal part of the presubiculum is more commonly known as the postsubiculum and is of interest because it contains head direction cells, which are responsive to the facing direction of the head.

Prosubiculum

Prosubiculum is a term often used in reference to monkey anatomy but rarely in rodents, referring to a region located between the CA1 region of the

hippocampus The hippocampus (via Latin from Greek , ' seahorse') 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 the subiculum, and distinguished by higher cell density and smaller cell sizes.

Function

It is believed to play a role in some cases of human

epilepsy Epilepsy is a group of non-communicable neurological disorders characterized by recurrent epileptic seizures. Epileptic seizures can vary from brief and nearly undetectable periods to long periods of vigorous shaking due to abnormal electrical ...

. It has also been implicated in

working memory Working memory is a cognitive system with a limited capacity that can hold information temporarily. It is important for reasoning and the guidance of decision-making and behavior. Working memory is often used synonymously with short-term memory, ...

and drug

addiction Addiction is a neuropsychological disorder characterized by a persistent and intense urge to engage in certain behaviors, one of which is the usage of a drug, despite substantial harm and other negative consequences. Repetitive drug use oft ...

. It has been suggested that the dorsal subiculum is involved in spatial relations, and the ventral subiculum regulates the hypothalamic-pituitary-adrenal axis.

Clinical significance

Potential role in Alzheimer's disease

Rat studies indicate that lesioning of the subiculum decreases the spread of amyloid-beta in rat models of Alzheimer's disease. Alzheimer's disease pathology is thought to have

prion Prions are misfolded proteins that have the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases in humans and many other animals. It ...

-like properties. The disease tends to spread in characteristic sequence from the entorhinal cortex through the subiculum.