Claustrum
Encyclopedia
The claustrum, which is suspected to be present in all mammals, is a fairly thin (fraction of 1 mm to multiple mms) vertical curved sheet of subcortical gray matter
oriented sagittally
between the white matter tracts of the external capsule
and extreme capsule
. The claustrum is lateral to the putamen
and medial to the insular cortex
and is considered by some sources to be part of the basal ganglia
.
There are lateral and medial tracts connecting to many cortices and perhaps to the hippocampus
, the amygdala
, and the caudate nucleus
(connections with subcortical centers are a matter of debate).
One of the interesting features of the claustrum is the uniformity in the types and numbers of cells. Since there is no function segregation or structural inhomogeneity, when waves of information come through the claustrum, the neurons will be especially sensitive to the timing of the inputs. Experiments to discover the physiological role of the claustrum are performed much the same with other structures, primarily utilizing lesion experiments, single-cell recordings, and stimulation studies in animals, as well as clinical observations and imaging.
The analogy researchers Francis Crick
and Christof Koch
have used to describe the claustrum compares it to conductor of an orchestra. The different parts (cortical subregions) must play in harmony or else the result is a cacophony of sounds. The neurons must take in different types of data (color, motion) across various modalities (visual, sound) and coalesce and bind them. An interesting question to ask, however, is why the claustrum is located where it is, when all this information is brought from all over the brain
. Transmission might be much more efficient if its location were under the cortex
, decreasing the length of many of the loops. More studies on latency would be useful, since timing appears to be a primary function. Also, greater examination into how claustral neurons respond during a task of moderate complexity would be highly practical.
One big point of discussion with regard to the claustrum has been on the ontogeny
. One side, which Dr. Edelstein deems the pallial group, believes the claustrum is a derivative of the insular cortex. While some designated this as a certain distinguished area not to be confused with the rest of the cortex, they still ascertained that the ontogeny was based on the development of the cortex. The other side states that the claustrum is derived from basal ganglia. Ramon y Cajal supported this view, as did many other researchers. Based on more recent methods of looking at the development of both the human and animal mind, including fMRI among others, there has been increasing evidence against the claustrum's being a part of the cortex. They seem to have distinct developmental periods and are, therefore, deemed separate structures. The third view, which is where the majority of support is coming from at present, says that the claustrum is neither distinctly part of the cortex nor from the basal ganglia
complex. Based on a number of studies, including those that show projections on both sides of the claustrum, many believe the claustrum should be considered a seventh layer of the cortex, in the insular region. This hypothesis, which is growing support, including the aforementioned Dr. Larry Edelstein, is labeled as Filiminoff's hypothesis since he was estimated to be the first to come to this conclusion
As far as historical cases shedding light on the anatomy and function of the claustrum is concerned, there have not been many to date that survived the struggle of time. There was one documented case on an enlarged claustrum in a patient with epilepsy, as well as another case in which the insula was malformed but the claustrum remained. These cases have not lent very much toward the pursuit of truth regarding the claustrum. At this point in time, pathology involved with the claustrum remains unknown. Also, due to the location and complex integration of the claustrum with other parts of the brain, it is difficult to do lesion studies without affecting other regions. Likewise, ablation is not an effective option, either. Most studies involve either the removal and preservation of the brain or in vivo
scanning of the area of interest during different studies. This could involve fMRI, the newer Tractography
technology, or others.
The following is a notable quote about Francis Crick documenting the importance of the claustrum as well as other research performed at the Salk's Crick-Jacobs Center for Computational and Theoretical Biology:
"…Even in his last few moments, Francis was thinking about the new center. Several months ago he wrote a position paper suggesting the Center focus its work on the claustrum, a part of the brain amenable to both molecular and cellular analysis. Because the claustrum is not well understood, he set out to write a review paper on it, and he was working on the document literally hours before his death. Francis wrote that paper for us and for our research, not for himself…"
. It is on both sides of the brain, and can be found below the insular cortex, which deep to the temporal and parietal lobes at the deepest point of the lateral fissure, and above the outside of the putamen, which is a sub-structure of the basal ganglia. The sheet is approximately one to several millimeters thick, and can cover up to a couple centimeters length wise depending on the animal.
One interesting aspect about the claustrum is the lack of cell types. In most parts of the brain, especially in the cortical regions, there is considerable differentiation of cell types, giving way to a number of functions. In the claustrum, as Dr. Crick and others pointed out, there are three main types of cells. The first, which is deemed Type 1, is large with spine-covered dendritic processes. These cells receive input as well as project back toward various regions, both laterally and medially. The other two types of cells do not have spines, but can be told apart based on the cell body size. However, both are restricted to the claustrum and, thus, are labeled interneurons.
It is clear that the claustrum projects to, and receives projections from, a number of cortices, including the primary motor, premotor, prefrontal, auditory
, and visual, among others. In one study conducted in France by Judith Tanne-Gariepy et al. (9), these projections were traced back to segregated areas, including differentiated areas along the dorsoventral axis for the pre-supplementary motor area and supplementary motor area – proper. Projections from the claustrum to various sub-regions of the motor cortex were shown to overlap somewhat, but did show a degree of local segregation. The truly interesting thing about the claustrum, however, is how it can take in multiple information modalities, including motor, visual, and auditory. It has even been shown that the same cells can process information across all these types, even though there is some semblance of segregation across a single type of information.
There has also been a number of interesting studies looking at the proteins inside the
claustrum. In one experiment performed at the University of South Carolina by J.R. Augustine et al., researchers looked at calcium-binding proteins in the rhesus monkey claustrum, including calbindin D28K, parvalbumin, and carretinin. After removing the brains and properly preserving them, the group used various antibodies and antiserum
s to detect the presence of the proteins. The calbindin proteins were shown as likely elements in the inhibitory circuitry of the claustrum, while the calretinin most likely served as calcium buffer to maintain homeostasis. Another study looked at the serotonergic innervation in the claustrum. The clear conclusion here was that, in the ventral claustrum where the visual projections are, the stained axons were short and arranged randomly. However, in the dorsal, non-visual section, of the claustrum, the fibers ran consistently in long lengths along the dorsal-ventral direction. Like many of the other studies, this is a good first step toward determining the true functions of the claustrum, although there is still much room for work.
and his colleague Christof Koch
, in which they discussed the claustrum as it could pertain to consciousness, many researchers have recently jumped on the proverbial bandwagon.
Through a number of different studies, summed up succinctly by Crick
and Koch
, it has been found that the claustrum is, it seems, crucial in modality
integration. Objects in real life have many different simultaneous characteristics such as: sound, shape, color, speed, weight, smell, etc. It is necessary for us to take in all of this information and integrate it together to potentially one object. In doing so, processing can take place, and the brain can determine the necessary actions to take. If this integration did not take place, one would not be able to converge all the information into a single percept, and would thus be perpetually confused. The claustrum is crucial in this process.
However, adequate studies are still lacking, and more research will be needed in order to attain the necessary detail and confidence regarding the claustrum.
and dementia with Lewy bodies
is often affected with Alpha-synuclein
neuron inclusions called Lewy bodies and Lewy neurites and Beta amyloid. This pathology strongly correlates with the presence of dementia in these conditions.
oriented sagittally
Sagittal plane
Sagittal plane is a vertical plane which passes from front to rear dividing the body into right and left sections.-Variations:Examples include:...
between the white matter tracts of the external capsule
External capsule
The external capsule is a series of white matter fiber tracts in the brain. These fibers run between the most lateral segment of the lentiform nucleus and the claustrum....
and extreme capsule
Extreme capsule
The extreme capsule is a long association fiber pathway of white matter in the brain that provides bidirectional communication between such areas as the claustrum and the insular cortex, and the inferior frontal gyrus and the middle-posterior portion of the superior temporal gyrus...
. The claustrum is lateral to the putamen
Putamen
The putamen is a round structure located at the base of the forebrain . The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that comprises the basal ganglia. Through various pathways, the putamen is connected to the substantia nigra and globus pallidus...
and medial to the insular cortex
Insular cortex
In each hemisphere of the mammalian brain the insular cortex is a portion of the cerebral cortex folded deep within the lateral sulcus between the temporal lobe and the frontal lobe. The cortical area overlying it towards the lateral surface of the brain is the operculum...
and is considered by some sources to be part of the 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...
.
There are lateral and medial tracts connecting to many cortices and perhaps to 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...
, the amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
, and the caudate nucleus
Caudate nucleus
The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate nucleus is an important part of the brain's learning and memory system.-Anatomy:...
(connections with subcortical centers are a matter of debate).
One of the interesting features of the claustrum is the uniformity in the types and numbers of cells. Since there is no function segregation or structural inhomogeneity, when waves of information come through the claustrum, the neurons will be especially sensitive to the timing of the inputs. Experiments to discover the physiological role of the claustrum are performed much the same with other structures, primarily utilizing lesion experiments, single-cell recordings, and stimulation studies in animals, as well as clinical observations and imaging.
The analogy researchers Francis Crick
Francis Crick
Francis Harry Compton Crick OM FRS was an English molecular biologist, biophysicist, and neuroscientist, and most noted for being one of two co-discoverers of the structure of the DNA molecule in 1953, together with James D. Watson...
and Christof Koch
Christof Koch
Christof Koch is an American neuroscientist working on the neural basis of consciousness. He is the Lois and Victor Troendle Professor of Cognitive and Behavioral Biology at California Institute of Technology, where he has been since 1986...
have used to describe the claustrum compares it to conductor of an orchestra. The different parts (cortical subregions) must play in harmony or else the result is a cacophony of sounds. The neurons must take in different types of data (color, motion) across various modalities (visual, sound) and coalesce and bind them. An interesting question to ask, however, is why the claustrum is located where it is, when all this information is brought from all over the brain
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. Transmission might be much more efficient if its location were under the cortex
Cerebral cortex
The cerebral cortex is a sheet of neural tissue that is outermost to the cerebrum of the mammalian brain. It plays a key role in memory, attention, perceptual awareness, thought, language, and consciousness. It is constituted of up to six horizontal layers, each of which has a different...
, decreasing the length of many of the loops. More studies on latency would be useful, since timing appears to be a primary function. Also, greater examination into how claustral neurons respond during a task of moderate complexity would be highly practical.
Name
The name "claustrum" comes from Latin and means "barrier" or "fence". The similar word "claudere" means "to shut" or "to close".History
The claustrum has been studied for at least 191 years, according to Dr. Edelstein. Many researchers have looked at it through the ages as an interesting structure that could hold the key to a number of neuro-based questions. The claustrum has a phylogenetic background appearing predominantly in insectivores, Prosimians, and Marsupials. It is difficult to trace where the evolution of the structure originated.One big point of discussion with regard to the claustrum has been on the ontogeny
Ontogeny
Ontogeny is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan...
. One side, which Dr. Edelstein deems the pallial group, believes the claustrum is a derivative of the insular cortex. While some designated this as a certain distinguished area not to be confused with the rest of the cortex, they still ascertained that the ontogeny was based on the development of the cortex. The other side states that the claustrum is derived from basal ganglia. Ramon y Cajal supported this view, as did many other researchers. Based on more recent methods of looking at the development of both the human and animal mind, including fMRI among others, there has been increasing evidence against the claustrum's being a part of the cortex. They seem to have distinct developmental periods and are, therefore, deemed separate structures. The third view, which is where the majority of support is coming from at present, says that the claustrum is neither distinctly part of the cortex nor from the 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...
complex. Based on a number of studies, including those that show projections on both sides of the claustrum, many believe the claustrum should be considered a seventh layer of the cortex, in the insular region. This hypothesis, which is growing support, including the aforementioned Dr. Larry Edelstein, is labeled as Filiminoff's hypothesis since he was estimated to be the first to come to this conclusion
As far as historical cases shedding light on the anatomy and function of the claustrum is concerned, there have not been many to date that survived the struggle of time. There was one documented case on an enlarged claustrum in a patient with epilepsy, as well as another case in which the insula was malformed but the claustrum remained. These cases have not lent very much toward the pursuit of truth regarding the claustrum. At this point in time, pathology involved with the claustrum remains unknown. Also, due to the location and complex integration of the claustrum with other parts of the brain, it is difficult to do lesion studies without affecting other regions. Likewise, ablation is not an effective option, either. Most studies involve either the removal and preservation of the brain or in vivo
In vivo
In vivo is experimentation using a whole, living organism as opposed to a partial or dead organism, or an in vitro controlled environment. Animal testing and clinical trials are two forms of in vivo research...
scanning of the area of interest during different studies. This could involve fMRI, the newer Tractography
Tractography
In neuroscience, tractography is a procedure to demonstrate the neural tracts.It uses special techniques of magnetic resonance imaging , and computer-based image analysis.The results are presented in two- and three-dimensional images....
technology, or others.
The following is a notable quote about Francis Crick documenting the importance of the claustrum as well as other research performed at the Salk's Crick-Jacobs Center for Computational and Theoretical Biology:
"…Even in his last few moments, Francis was thinking about the new center. Several months ago he wrote a position paper suggesting the Center focus its work on the claustrum, a part of the brain amenable to both molecular and cellular analysis. Because the claustrum is not well understood, he set out to write a review paper on it, and he was working on the document literally hours before his death. Francis wrote that paper for us and for our research, not for himself…"
Anatomy
The claustrum is a telencephalic subcortical structure. It is a thin sheet of grey matter underneath the inner part of the neocortexNeocortex
The neocortex , also called the neopallium and isocortex , is a part of the brain of mammals. It is the outer layer of the cerebral hemispheres, and made up of six layers, labelled I to VI...
. It is on both sides of the brain, and can be found below the insular cortex, which deep to the temporal and parietal lobes at the deepest point of the lateral fissure, and above the outside of the putamen, which is a sub-structure of the basal ganglia. The sheet is approximately one to several millimeters thick, and can cover up to a couple centimeters length wise depending on the animal.
One interesting aspect about the claustrum is the lack of cell types. In most parts of the brain, especially in the cortical regions, there is considerable differentiation of cell types, giving way to a number of functions. In the claustrum, as Dr. Crick and others pointed out, there are three main types of cells. The first, which is deemed Type 1, is large with spine-covered dendritic processes. These cells receive input as well as project back toward various regions, both laterally and medially. The other two types of cells do not have spines, but can be told apart based on the cell body size. However, both are restricted to the claustrum and, thus, are labeled interneurons.
It is clear that the claustrum projects to, and receives projections from, a number of cortices, including the primary motor, premotor, prefrontal, auditory
Auditory system
The auditory system is the sensory system for the sense of hearing.- Outer ear :The folds of cartilage surrounding the ear canal are called the pinna...
, and visual, among others. In one study conducted in France by Judith Tanne-Gariepy et al. (9), these projections were traced back to segregated areas, including differentiated areas along the dorsoventral axis for the pre-supplementary motor area and supplementary motor area – proper. Projections from the claustrum to various sub-regions of the motor cortex were shown to overlap somewhat, but did show a degree of local segregation. The truly interesting thing about the claustrum, however, is how it can take in multiple information modalities, including motor, visual, and auditory. It has even been shown that the same cells can process information across all these types, even though there is some semblance of segregation across a single type of information.
There has also been a number of interesting studies looking at the proteins inside the
claustrum. In one experiment performed at the University of South Carolina by J.R. Augustine et al., researchers looked at calcium-binding proteins in the rhesus monkey claustrum, including calbindin D28K, parvalbumin, and carretinin. After removing the brains and properly preserving them, the group used various antibodies and antiserum
Antiserum
Antiserum is blood serum containing polyclonal antibodies. Antiserum is used to pass on passive immunity to many diseases. Passive antibody transfusion from a previous human survivor is the only known effective treatment for Ebola infection .The most common use of antiserum in humans is as...
s to detect the presence of the proteins. The calbindin proteins were shown as likely elements in the inhibitory circuitry of the claustrum, while the calretinin most likely served as calcium buffer to maintain homeostasis. Another study looked at the serotonergic innervation in the claustrum. The clear conclusion here was that, in the ventral claustrum where the visual projections are, the stained axons were short and arranged randomly. However, in the dorsal, non-visual section, of the claustrum, the fibers ran consistently in long lengths along the dorsal-ventral direction. Like many of the other studies, this is a good first step toward determining the true functions of the claustrum, although there is still much room for work.
Function
There is still very little known about the actual function of the claustrum. While it has been studied for a considerable amount of time, it is still a minor structure in the brain. Anatomical hindrances combined with a lack of case studies have left many holes in the research of the claustrum. Also, until recently, there has not been much of a reason to study the claustrum. With the paper written by Francis CrickFrancis Crick
Francis Harry Compton Crick OM FRS was an English molecular biologist, biophysicist, and neuroscientist, and most noted for being one of two co-discoverers of the structure of the DNA molecule in 1953, together with James D. Watson...
and his colleague Christof Koch
Christof Koch
Christof Koch is an American neuroscientist working on the neural basis of consciousness. He is the Lois and Victor Troendle Professor of Cognitive and Behavioral Biology at California Institute of Technology, where he has been since 1986...
, in which they discussed the claustrum as it could pertain to consciousness, many researchers have recently jumped on the proverbial bandwagon.
Integration of modalities
Through a number of different studies, summed up succinctly by Crick
Crick
- People :* Bernard Crick, British political scientist* Francis Crick , British scientist and joint discoverer of the structure of DNA* Harold Crick, protagonist of a 2006 film, Stranger than Fiction* Mark Crick, British author and photographer...
and Koch
Koch
Koch may refer to:* Koch , a type of Arctic boat* Koch people , an ethnic group originally from the ancient Koch kingdom in north east India* Koch , people with this surname* Koch, Łódź Voivodeship, a village in central Poland...
, it has been found that the claustrum is, it seems, crucial in modality
Modality
-Humanities:* In law: the basis of legal argumentation in United States constitutional law* In theology: Modality : the organization and structure of the church, as distinct from sodality or parachurch organizations...
integration. Objects in real life have many different simultaneous characteristics such as: sound, shape, color, speed, weight, smell, etc. It is necessary for us to take in all of this information and integrate it together to potentially one object. In doing so, processing can take place, and the brain can determine the necessary actions to take. If this integration did not take place, one would not be able to converge all the information into a single percept, and would thus be perpetually confused. The claustrum is crucial in this process.
Role in Functional timing
Perhaps just as important as the ability to take in multiple modalities is the claustrum's capacity for functional timing. Few latency experiments have been performed (more would definitely be useful), but it is clear that the claustrum in one way or another is a big part of taking all the different sources of information and integrating them together so they are processed at the same time. Without this ability, the inherent differences in processing timing for vision vs. hearing and other types would take over and one would never be able to combine information and have a single percept.However, adequate studies are still lacking, and more research will be needed in order to attain the necessary detail and confidence regarding the claustrum.
Pathology
The claustrum in those with Parkinson's diseaseParkinson's disease
Parkinson's disease is a degenerative disorder of the central nervous system...
and dementia with Lewy bodies
Dementia with Lewy bodies
Dementia with Lewy bodies , also known under a variety of other names including Lewy body dementia, diffuse Lewy body disease, cortical Lewy body disease, and senile dementia of Lewy type, is a type of dementia closely allied to both Alzheimers and Parkinson's Diseases...
is often affected with Alpha-synuclein
Alpha-synuclein
Alpha-synuclein is a protein that, in humans, is encoded by the SNCA gene. An alpha-synuclein fragment, known as the non-Abeta component of Alzheimer's disease amyloid, originally found in an amyloid-enriched fraction, is shown to be a fragment of its precursor protein, NACP, by cloning of the...
neuron inclusions called Lewy bodies and Lewy neurites and Beta amyloid. This pathology strongly correlates with the presence of dementia in these conditions.
External links
- NIF Search - Claustrum 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:...