Habenula
Encyclopedia
In neuroanatomy
, habenula (diminutive of Latin habena meaning rein
) originally denoted the stalk of the pineal gland
(pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the pineal gland was believed to be associated, the habenular nucleus. The habenular nucleus is a set of well conserved structures in all vertebrate
animals.
Currently, the Terminologia Anatomica
term refers exclusively to this separate cell mass in the caudal and dorsal aspect of the dorsal thalamus
(the epithalamus
), embedded in the posterior end of the medullary stria
from which it receives most of its afferent
fibers. By way of the retroflex fasciculus (habenulointerpeduncular tract) it projects to the interpeduncular nucleus
and other paramedian cell groups of the midbrain tegmentum
.
The habenula receives input from the brain via the stria medullaris
thalami and outputs to many midbrain areas involved in releasing neuromodulators, such as dopamine
, norepinephrine
, and serotonin
.
(bringing input from the hippocampus
and lateral septum), the ventral pallidum (bringing input from the nucleus accumbens
and mediodorsal nucleus of the thalamus
), the lateral hypothalamus
, and the internal segment of the globus pallidus
(bringing input from other basal ganglia
structures).
Neurons in the lateral habenula are ‘reward-negative’ as they are activated by stimulus associated with unpleasant events, the absence of the reward or punishment especially when this is unpredictable. Reward information to the lateral habenula comes from the internal part of the globus pallidus.
The outputs of the lateral habenula target dopaminergic regions (substantia nigra
pars compacta
and the ventral tegmental area), serotinergic regions (median raphe and dorsal raphe nuclei), and a cholinergic region (the laterodorsal tegmental nucleus
). This output inhibits dopamine neurons in substantia nigra pars compacta and the ventral tegmental area, with activation in the lateral habenula linking to deactivation in them, and vice versa, deactivation in the lateral habenula with their activation. The lateral habenula functions to oppose the action of the laterodorsal tegmental nucleus in the acquisition of avoidance response
s but not the processing of avoidance later on when it is a memory, motivation or its execution.
(the fimbrialis septi and triangularis septi nuclei), dopaminergic inputs from the interfascicular nucleus of the ventral tegmental area, noradrenergic inputs from the locus ceruleus
, and GABAergic inputs from the diagonal band of Broca
.
The medial habenula sends outputs of substance P
and acetylcholine
to the interpeduncular nucleus
as well as to the pineal gland.
. Deep brain stimulation
of the major afferent bundle (i.e., stria medullaris thalami) of the lateral hebenuala has been used for treatment of depression where it is severe, protracted and therapy-resistant.
Neuroanatomy
Neuroanatomy is the study of the anatomy and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defined nervous systems, and thus we can begin to speak of...
, habenula (diminutive of Latin habena meaning rein
Rein
Reins are items of horse tack, used to direct a horse or other animal used for riding or driving. Reins can be made of leather, nylon, metal, or other materials, and attach to a bridle via either its bit or its noseband.-Use for riding:...
) originally denoted the stalk of the pineal gland
Pineal gland
The pineal gland is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions...
(pineal habenula; pedunculus of pineal body), but gradually came to refer to a neighboring group of nerve cells with which the pineal gland was believed to be associated, the habenular nucleus. The habenular nucleus is a set of well conserved structures in all vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
animals.
Currently, the Terminologia Anatomica
Terminologia Anatomica
Terminologia Anatomica is the international standard on human anatomic terminology. It was developed by the Federative Committee on Anatomical Terminology and the International Federation of Associations of Anatomists and was released in 1998. It supersedes the previous standard, Nomina...
term refers exclusively to this separate cell mass in the caudal and dorsal aspect of the dorsal thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
(the epithalamus
Epithalamus
The epithalamus is a dorsal posterior segment of the diencephalon which includes the habenula, the stria medullaris and the pineal body...
), embedded in the posterior end of the medullary stria
Stria medullaris
The stria medullaris, also known as stria medullaris thalami, is a fiber bundle containing efferent fibers from the septal nuclei, lateral preoptico-hypothalamic region, and anterior thalamic nuclei to the habenula...
from which it receives most of its afferent
Afferent nerve
In the nervous system, afferent neurons , carry nerve impulses from receptors or sense organs towards the central nervous system. This term can also be used to describe relative connections between structures. Afferent neurons communicate with specialized interneurons...
fibers. By way of the retroflex fasciculus (habenulointerpeduncular tract) it projects to the interpeduncular nucleus
Interpeduncular nucleus
The Interpeduncular nucleus is a unpaired, ovoid cell group at the base of the midbrain tegmentum. It is located in the mesencephalon below the interpeduncular fossa...
and other paramedian cell groups of the midbrain tegmentum
Midbrain tegmentum
The midbrain tegmentum is the part of the midbrain extending from the substantia nigra to the cerebral aqueduct in a horizontal section of the midbrain. It forms the floor of the midbrain which surrounds the cerebral aqueduct.-External links:*...
.
The habenula receives input from the brain via the stria medullaris
Stria medullaris
The stria medullaris, also known as stria medullaris thalami, is a fiber bundle containing efferent fibers from the septal nuclei, lateral preoptico-hypothalamic region, and anterior thalamic nuclei to the habenula...
thalami and outputs to many midbrain areas involved in releasing neuromodulators, such as dopamine
Dopamine
Dopamine is a catecholamine neurotransmitter present in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this substituted phenethylamine functions as a neurotransmitter, activating the five known types of dopamine receptors—D1, D2, D3, D4, and D5—and their...
, norepinephrine
Norepinephrine
Norepinephrine is the US name for noradrenaline , a catecholamine with multiple roles including as a hormone and a neurotransmitter...
, and serotonin
Serotonin
Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...
.
Anatomy
The habenula was traditionally divided into lateral (limbic) and medial (motor) parts. Detailed examination of the region in the rat, however, suggested that the lateral part should be further divided into ten distinct subnuclei and the medial into five distinct subnuclei.Lateral habenula
The primary input regions to the lateral habenula are the lateral preoptic areaPreoptic area
The preoptic area is a region of the hypothalamus. According to the MeSH classification, it is considered part of the anterior hypothalamus. There are four nuclei in this region, according to Terminologia Anatomica .-Functions:The preoptic area is responsible for thermoregulation and receives...
(bringing input from the hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
and lateral septum), the ventral pallidum (bringing input from the nucleus accumbens
Nucleus accumbens
The nucleus accumbens , also known as the accumbens nucleus or as the nucleus accumbens septi , is a collection of neurons and forms the main part of the ventral striatum...
and mediodorsal nucleus of the thalamus
Thalamus
The thalamus is a midline paired symmetrical structure within the brains of vertebrates, including humans. It is situated between the cerebral cortex and midbrain, both in terms of location and neurological connections...
), the lateral hypothalamus
Hypothalamus
The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...
, and the internal segment of the globus pallidus
Globus pallidus
The globus pallidus also known as paleostriatum, is a sub-cortical structure of the brain. Topographically, it is part of the telencephalon, but retains close functional ties with the subthalamus - both of which are part of the extrapyramidal motor system...
(bringing input from other basal ganglia
Basal ganglia
The basal ganglia are a group of nuclei of varied origin in the brains of vertebrates that act as a cohesive functional unit. They are situated at the base of the forebrain and are strongly connected with the cerebral cortex, thalamus and other brain areas...
structures).
Neurons in the lateral habenula are ‘reward-negative’ as they are activated by stimulus associated with unpleasant events, the absence of the reward or punishment especially when this is unpredictable. Reward information to the lateral habenula comes from the internal part of the globus pallidus.
The outputs of the lateral habenula target dopaminergic regions (substantia nigra
Substantia nigra
The substantia nigra is a brain structure located in the mesencephalon that plays an important role in reward, addiction, and movement. Substantia nigra is Latin for "black substance", as parts of the substantia nigra appear darker than neighboring areas due to high levels of melanin in...
pars compacta
Pars compacta
-Anatomy:In humans, the nerve cell bodies of the pars compacta are coloured black by the pigment neuromelanin. The degree of pigmentation increases with age. This pigmentation is visible as a distinctive black stripe in brain sections and is the origin of the name given to this area. The neurons...
and the ventral tegmental area), serotinergic regions (median raphe and dorsal raphe nuclei), and a cholinergic region (the laterodorsal tegmental nucleus
Laterodorsal tegmental nucleus
The laterodorsal tegmental nucleus is a nucleus situated in the brainstem, spanning the midbrain tegmentum and the pontine tegmentum...
). This output inhibits dopamine neurons in substantia nigra pars compacta and the ventral tegmental area, with activation in the lateral habenula linking to deactivation in them, and vice versa, deactivation in the lateral habenula with their activation. The lateral habenula functions to oppose the action of the laterodorsal tegmental nucleus in the acquisition of avoidance response
Avoidance response
An avoidance response is a form of escape behavior present in animals in which the subject evades an aversive event. This can be due to anxiety or a frightening situation. Avoidance response is a response that is not necessarily conditioned before being exposed to in the stressful or fearful...
s but not the processing of avoidance later on when it is a memory, motivation or its execution.
Medial habenula
Input to the medial habenula comes from a variety of regions and carries a number of different chemicals. Input regions include septal nucleiSeptal nuclei
The septal area are structures that lie below the rostrum of corpus callosum in front of lamina terminalis , composed of medium-size neurons grouped into medial, lateral, and posterior groups...
(the fimbrialis septi and triangularis septi nuclei), dopaminergic inputs from the interfascicular nucleus of the ventral tegmental area, noradrenergic inputs from the locus ceruleus
Locus ceruleus
The locus coeruleus , is a nucleus in the brainstem involved with physiological responses to stress and panic. It was discovered in the 18th century by Félix Vicq-d'Azyr....
, and GABAergic inputs from the diagonal band of Broca
Diagonal band of Broca
The diagonal band of Broca forms the medial margin of the anterior perforated substance.-Contents:It consists of fibers that are said to arise in the parolfactory area, the gyrus subcallosus and the anterior perforated substance, and course backward in the longitudinal striae to the dentate gyrus...
.
The medial habenula sends outputs of substance P
Substance P
In the field of neuroscience, substance P is a neuropeptide: an undecapeptide that functions as a neurotransmitter and as a neuromodulator. It belongs to the tachykinin neuropeptide family. Substance P and its closely related neuropeptide neurokinin A are produced from a polyprotein precursor...
and acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
to the interpeduncular nucleus
Interpeduncular nucleus
The Interpeduncular nucleus is a unpaired, ovoid cell group at the base of the midbrain tegmentum. It is located in the mesencephalon below the interpeduncular fossa...
as well as to the pineal gland.
Functions
The habenular nuclei have been shown to be involved in many functions, including pain processing, reproductive behavior, nutrition, sleep-wake cycles, stress responses, and learning. Recent demonstrations using fMRI and single unit electrophysiology have closely linked the function of the lateral habenula with reward processing, in particular with regard to encoding negative feedback or negative rewards. Matsumoto and Hikosaka suggested in 2007 that this reward and reward-negative information in the brain might "be elaborated through the interplay among the lateral habenula, the basal ganglia, and monoaminergic (dopaminergic and serotonergic) systems" and that the lateral habenula may play a pivotal role in this "integrative function". Recent evidence suggests that neurons in the lateral habenula signal signed information-prediction errors in addition to signed reward-prediction errors .Depression
Both the medial and lateral habenula show reduced volume in those with depression. Neuron cell numbers were also reduced on the right side. Such changes are not seen in those with schizophreniaSchizophrenia
Schizophrenia is a mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests itself as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social...
. Deep brain stimulation
Deep brain stimulation
Deep brain stimulation is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain...
of the major afferent bundle (i.e., stria medullaris thalami) of the lateral hebenuala has been used for treatment of depression where it is severe, protracted and therapy-resistant.
External links
- NIF Search - Habenula via the Neuroscience Information FrameworkNeuroscience Information FrameworkThe Neuroscience Information Framework is a repository of global neuroscience web resources, including experimental, clinical, and translational neuroscience databases, knowledge bases, atlases, and genetic/genomic resources.-Description:...