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Showing posts with label Neuroscience. Show all posts
Showing posts with label Neuroscience. Show all posts

Monday, December 24, 2018

What is Dopamine

Dopamine is one of the brain’s neurotransmitters—a chemical that ferries information between neurons. Dopamine helps regulate movement, attention, learning, and emotional responses. It also enables us not only to see rewards, but to take action to move toward them. Since dopamine contributes to feelings of pleasures and satisfaction as part of the reward system, the neurotransmitter also plays a part in addiction. 



Neurotransmitters are chemicals made by nerve cells called neurons. They’re used to communicate messages across different parts of the brain and between the brain and the rest of the body.

Dopamine is involved mainly in controlling movement. An insufficient production of dopamine in part of the brain can lead to Parkinson’s disease. Parkinson’s diseases is a noncurable nervous system disorder that affects movement. It may cause stiffness, tremors, shaking, and other symptoms. How Dopamine Works Inside the Brain’s Reward System

Dopamine plays a role in the brain’s reward system, helping to reinforce certain behaviors that result in reward. A surge of dopamine, for instance, is what prompts a laboratory rat to repeatedly press a lever to get a pellet of food, or a human to take a second slice of pizza.
Recently, scientists have shown that dopamine can help with unlearning fearful associations. In a study published in June 2018 in the journal Nature Communications, researchers uncovered the role of dopamine in lessening fearful reactions over time, an important component of therapy for people with anxiety disorders, such as phobias or post-traumatic stress disorder (PTSD).
More on the Brain and Dopamine

Dopamine also helps to aid the flow of information to the brain regions responsible for thought and emotion. According to the National Institute of Mental Health, too little dopamine — or problems in the way the brain uses dopamine — may play a role in disorders such as schizophrenia or attention deficit hyperactivity disorder (ADHD).
Dopamine and the Body’s Stress Response

In other parts of the body, dopamine acts as type of hormone called a catecholamine. Catecholamines are made in the adrenal glands — small hormone production factories that sit on top of the kidneys.
There are three main catecholamines:

    Dopamine
    Epinephrine (adrenaline)
    Norepinephrine

These hormones get released into the bloodstream when the body is physically or mentally stressed. They cause biochemical changes that activate the so-called fight-or-flight response. That’s the body’s natural reaction to a real or perceived stress.
Dopamine has many functions outside the brain. It acts as a vasodilator, helping to widen blood vessels. It helps to increase urine output in the kidneys, and in the pancreas it reduces the production of insulin, a hormone involved in blood sugar regulation.
Dopamine and Digestion

Dopamine also plays a role in the digestive system, helping to make sure the contents of the gastrointestinal tract don’t pass through too quickly. In the immune system, dopamine dampens inflammation, normally helping to prevent the sort of runaway immune response seen in autoimmune diseases.
What Are Dopamine Receptors?

Dopamine receptors are proteins found in the brain and nerves throughout the body. If neurotransmitters are the nerve cells’ chemical messengers, then receptors are the nerve cells’ chemical receivers.
As a dopamine signal approaches a nearby neuron, it attaches to that neuron’s receptor. The receptor and neurotransmitter work like a lock and key. The dopamine attaches to the dopamine receptor, delivering its chemical message by causing changes in the receiving nerve cell.
Why Dopamine Receptors Are Key for Neurological and Physical Functions

Dopamine receptors play an important role in many neurological processes, including movement coordination and fine motor control, pleasure, cognition, memory, and learning.

Abnormally functioning dopamine receptors may play a role in several neurological and psychiatric illnesses. Therefore, dopamine receptors are a natural target for many drug therapies.

Some street drugs, including heroin, cocaine, and methamphetamine, also act on dopamine receptors in the brain. They can cause nerve cells to release too much dopamine or prevent the nervous system from recycling dopamine once it’s done its job, highjacking the brain’s reward system.
Euphoric Effects, Pleasure, and Dopamine

Dopamine creates feelings of pleasure. Certain drugs, such as cocaine, can cause large amounts of dopamine to flood the system, producing euphoric effects or a “high” that leave the user wanting more.
As these drugs are abused over time, dopamine’s pleasurable effects on the brain lessen.

To regain these pleasurable effects, a user must increase the amount of drug taken. This phenomenon is called “tolerance.”
Dopamine Drugs

There are a few classes of medication that work on the dopamine pathways of the brain to treat disease. They include:

Levodopa (L-dopa) Levodopa is a drug used to treat Parkinson’s disease. Symptoms of Parkinson’s disease start to show up when dopamine-producing cells in the brain die. Levodopa, a precursor chemical to dopamine, helps to boost dopamine levels in the brain. Once levodopa reaches the brain, it transforms into dopamine.

Dopamine Agonists Dopamine agonists are a class of drugs that bind to and activate dopamine receptors in the brain. They mimic the action of naturally-occurring dopamine in the brain, causing the neurons to react as they would to dopamine.

Dopamine agonists trick the brain into thinking it’s getting the dopamine it needs.

Dopamine agonists are used to treat low dopamine conditions, including Parkinson’s disease and restless legs syndrome (RLS). RLS is a sleep disorder that causes an unpleasant tingling or twitching sensation in the legs when lying or sitting down, mostly at night, resulting in an irresistible urge to move them, and in insomnia. Like Parkinson’s disease, it too seems to be caused by a dopamine shortage in the brain.

Dopamine agonists also are sometimes used to treat depression and fibromyalgia.

Common dopamine agonist drugs include:
    Mirapex (ramipexole)
    Neupro (rotigotine)
    Requip (ropinirole)

Serious side effects associated with dopamine agonists include low blood pressure, dizziness when standing up, hallucinations, and impulse control disorders, such as pathological gambling, compulsive eating, and hypersexuality.

Dopamine Antagonists Dopamine antagonists are a class of drugs that bind to and block dopamine receptors. Dopamine antagonists turn down dopamine activity, which may be useful for the treatment of psychiatric conditions such as schizophrenia and bipolar disorder, which have been associated with an overactive dopamine system.

Many antipsychotic drugs are dopamine antagonists, working to block dopamine receptors in the brain.

Dopamine antagonists that act on dopamine receptors in the gastrointestinal tract may be used to treat nausea, or as anti-emetics to stop vomiting.

Dopamine antagonist drugs include:

    Thorazine or Largactil (chlorpromazine)
    Reglan (metoclopramide)
    Phenergan (promethazine)
    Invenga (paliperidone)
    Risperdal (risperidone)
    Seroquel (quetiapine)
    Clozaril (clozepine)

Dopamine Supplements and Supplementation

Dopamine is found in many types of food, but dopamine itself can’t cross into the brain from the bloodstream, so eating foods that contain dopamine won’t raise dopamine levels in the brain. But dopamine’s precursor molecule, tyrosine, can cross the blood-brain barrier, according to a review published in November 2015 in the Journal of Psychiatric Research.
Tyrosine is an amino acid found naturally in protein-rich foods, such as cheese, nuts, and meat. Under certain circumstances, tyrosine supplements can help boost dopamine levels in the brain, leading some to believe that tyrosine supplementation could help with neurological and mental health conditions involving low dopamine. In fact, the Parkinson’s disease drug Levodopa was originally synthesized from one form of tyrosine.

But scientific studies have failed to show that this is the case. Tyrosine supplements don’t appear to have much — if any — effect on physiology, thought, or behavior.


  



Dopamine is heavily involved in the motor system. When the brain fails to produce enough dopamine, it can result in Parkinson’s disease. A primary treatment for Parkinson’s disease, therefore, is a drug called L-dopa, which spurs the production of dopamine. Dopamine has also been implicated in schizophrenia and ADHD, but its role is not fully understood. People with low dopamine activity may also be more prone to addiction. The presence of a certain kind of dopamine receptor is associated with sensation-seeking, more commonly known as risk taking.

Thursday, November 22, 2018

A computational foundation for thalamic engagement in cognitive flexibility.

Cecile G. Tamura
Neural representations of task rules are maintained in the prefrontal cortex, the part of the brain responsible for planning action. 
A new study from MIT has found that a region of the thalamus is key to the process of switching between the rules required for different contexts. This region, called the mediodorsal thalamus, suppresses representations that are not currently needed. That suppression also protects the representations as a short-term memory that can be reactivated when needed.
:The findings could help guide the development of better artificial intelligence algorithms. The human brain is very good at learning many different kinds of tasks — singing, walking, talking, etc. However, neural networks (a type of artificial intelligence based on interconnected nodes similar to neurons) usually are good at learning only one thing. These networks are subject to a phenomenon called “catastrophic forgetting” — when they try to learn a new task, previous tasks become overwritten.
Halassa and his colleagues now hope to apply their findings to improve neural networks’ ability to store previously learned tasks while learning to perform new ones."
Interactions between the prefrontal cortex (PFC) and mediodorsal thalamus are critical for cognitive flexibility, yet the underlying computations are unknown. To investigate frontothalamic substrates of cognitive flexibility, we developed a behavioral task in which mice switched between different sets of learned cues that guided attention toward either visual or auditory targets. We found that PFC responses reflected both the individual cues and their meaning as task rules, indicating a hierarchical cue-to-rule transformation. Conversely, mediodorsal thalamus responses reflected the statistical regularity of cue presentation and were required for switching between such experimentally specified cueing contexts. A subset of these thalamic responses sustained context-relevant PFC representations, while another suppressed the context-irrelevant ones. Through modeling and experimental validation, we find that thalamic-mediated suppression may not only reduce PFC representational interference but could also preserve unused cortical traces for future use. Overall, our study provides a computational foundation for thalamic engagement in cognitive flexibility.

Friday, February 23, 2018

The reason for even a moth’s brain is smarter than an Artificial Intelligence

Insects can recognize odors after just a handful of exposures, but machines still need huge training data sets to learn.
"In moths, the successful recognition of an odor triggers a reward mechanism in which neurons spray a chemical neurotransmitter called octopamine into the antenna lobe and mushroom body.
This is a crucial part of the learning process. Octopamine seems to help reinforce the neural wiring that leads to success. It is a key part of Hebbian learning, in which “cells that fire together wire together.” Indeed, neuroscientists have long known that moths do not learn without octopamine. But the role it plays isn’t well understood.
Learning in machines is very different. It relies on a process called backpropagation, which tweaks the neural connections in a way that improves outcomes. But information essentially travels backward through the network in this process, and there is no known analogue of it in nature."

Sunday, July 30, 2017

Schizophrenia could largely be the result of defective cells

"It was through studies of mice with human glial cells that we succeeded in testing how dysfunctional glial cells may cause abnormalities in the formation of the brain's neural networks, which may in turn cause severe anxiety, anti-social behaviour and severe sleep problems," says lead researcher Steven Goldman
Glial cells come in a variety of forms and can be found throughout the nervous system, taking on a bunch of supportive tasks to allow the nerve cells do what they do... best – pass on messages. This could be in the form of support, wrapping themselves around the nerves, or by surrounding the nerves to clean up stray chemical messages.
While dysfunctional helper cells have been associated with schizophrenia before, it's been assumed to be less important than abnormalities in the neurons themselves.
In this research the scientists took glial progenitor cells from patients diagnosed with schizophrenia and transplanted them into the brains of young mice. They then compared them with the same kinds of cells taken from subjects without schizophrenia.
That way they could be confident that similar behaviours in the mice were the product of the same pathology in humans.
Sure enough, the stem cells derived from the subjects with schizophrenia showed an unusual pattern of migration as they spread through the mice brains, leading to lower numbers of a type of glial cell that was responsible for mopping up neurotransmitter chemicals in the gaps between neurons.
The research hints at a faulty mechanism telling the glial cells where to stop and change into cells that perform their jobs.
When the mice were observed for behavioural differences, they showed clear signs of anxiety, sleep disruption, and anhedonia.

The Minding Brain

Friday, November 25, 2016

Artificial Spinal Cord Wirelessly Restores Walking in Paralyzed Monkeys


Reversing paralysis : According to Dr. Andrew Jackson, a neuroscientist at Newcastle University in the UK, as early as the end of this decade, we may witness patients with spinal cord injuries regain control of their own two legs and walk again.
The field of brain-machine interfaces is moving so fast that blink, and you might miss the latest breakthrough. Within the past year or so, BMIs have allowed paralyzed patients to Google on a tablet with brain waves, grasp objects using robotic surrogates and control a variety of prosthetic hands and other devices. And just a few months ago, a surprisingly study showed that implants that directly stimulate the spinal cord helps paraplegic patients recover some voluntary movement of their own legs.

Yet even amongst this slew of incredible advances, Courtine’s study stands out.
By implanting a wireless neural prosthetic into the spinal cord of paralyzed monkeys, a team led by Dr. Grégoire Courtine at the Swiss Federal institute of Technology (EPFL) in Lausanne, Switzerland achieved the seemingly impossible: the monkeys regained use of a paralyzed lower limb a mere six days after their initial injury without requiring any training.
The close-looped system directly reads signals from the brain in real-time and works on the patients’ own limbs, which means it doesn’t require expensive exoskeletons or external stimulation of the patient’s leg muscles to induce the contractions necessary for walking. That’s huge: it means the system could be readily used by patients in their own homes without doctor supervision.
https://www.oximity.com/…/Artificial-Spinal-Cord-Wirelessly… …

Cecile G. Tamura

What is memory?


The mechanism of memory remains one of the great unsolved problems of biology. Grappling with the question more than a hundred years ago, the German zoologist Richard Semon formulated the concept of the engram, lasting connections in the brain that result from simultaneous “excitations”, whose precise physical nature and consequences were out of reach of the biology of his day. Neuroscientists now have the knowledge and tools to tackle this question, however, and this Forum brings together leading contemporary views on the mechanisms of memory and what the engram means today.

Fig. 1

Synaptic connectivity between engram cells as a mechanism for memory storage. a Cellular connectivity in a feedforward excitatory circuit, b synaptic configuration, c dendritic spine density, and d protein synthesis state, shown in a naïve circuit, a circuit during encoding, a circuit after consolidation, or a circuit in an amnesic condition. Engram circuit, cells, and synapses are displayed in green, non-engram in gray. In the naïve state, the circuit displays a variety of synaptic patterns, including strong (thick gray lines) and weak synapses (thin gray lines) as well as silent synapses (dotted lines) exclusively expressing NMDA receptors. During encoding, a network of engram cells is recruited. The preferential connection between engram cells occurs either by potentiation of existing connections (blue dotted circles) or by unsilencing synapses (red dotted circles). A spine density increase supports the synaptic changes. During consolidation, the steady state synthesis of AMPA receptors is shifted to a higher level and the disruption of consolidation with protein synthesis inhibitors (PSI) results in retrograde amnesia. However, during PSI-induced amnesia, memory storage persists within an engram-specific set of weak synaptic connections

Monday, November 7, 2016

SLEEP STAGES and the so-called "COGNITIVE MAP"


(note: This post appears to be about just "sleep" but it is mainly concerned with how we integrate "space" and "time" into "maps" and so situate our "Selves"...and nightlong alternation between Slow Wave Sleep and Dream Sleep is key )
This recent article from Scientific American is a great review of the epistemological difficulties entailed in the study of our “minding brain’s” map making and how that model of the brain needs to be updated.
Decoding Space and Time in the Brain
https://blogs.scientificamerican.com/…/decoding-space-and-…/
It begins this way: "...henceforth, space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union between the two will preserve an independent reality."
They go on, "This now iconic quote spoken by Hermann Minkowski in 1906 captured the spirit of Albert Einstein's recently published special theory of relativity. Einstein, in a stroke of mathematical genius, had shown that both space and time as independent mathematical constructs were mere illusions in the equations of relativity, conceding instead to a 4-dimensional construct which Minkowski adroitly termed space-time.
While most people are familiar with the ensuing influence Einstein's ideas had on both the academic and public conception of the physical universe, few people are aware a similar revolution against space and time is underway in the fields of experimental psychology and neuroscience.”
We have recently posted on a few "erudite" but fatally flawed publications on the nature of "dreams" and their integration into the Role of Sleep in Making our Way through our lives when we are Awake (we might call it the 'DayJob" rather than the ""Night Job"
We see here, again in this popular article, the customary narrative of how and why we cycle through sleep stages.
http://www.world-of-lucid-dreaming.com/the-stages-of-sleep.…
However, the account that is still so rampant in our popular culture and in our Paparazzi driven media, does not point to the direct linkages which we suspect must exist between Slow Wave Sleep and REM sleep and its dreams.

HOW SEX RULES OUR DREAMS? IS FREUD BACK?
An entertaining and nice BEDTIME STORY
https://www.facebook.com/neuroendocrinology/photos/a.1633019730259383.1073741835.1576160679278622/1870502433177777/?type=3&theater
Today, we have realized how much crucial "consolidation' occurs during Slow Wave Sleep, enabling the hippocampal repository of 'episodically" described moments and experience to be somehow transferred or shared with cortical processes for use in the our next day's and subsequent days' experience and our management of our responses to the events that follow.
There's a fine review of Sleep Consolidation and the exquisite coordinations between parts of the brain going as we sleep available here:
About Sleep's Role in Memory
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768102/
Just how this ongoing synergy between hippocampus and cortical areas goes on is not yet discussed in any clear manner by neuroscience...although there is increasing aware of the characteristic charting of waves frequency and amplitudes that is associated with that correspondence, much of which arises during the nonREM Slow Wave Sleep periods of our nights.
Once of the prevalent ways of speaking, we have had since Tolman introduced his "cognitive map" notion in the 1940s as a counter to simplistic behaviorist narratives of the mind...is the treatment of the 'minding brain" as one which somehow relies on maps that are formed over the course of experience to guide us in our lives...or "navigating" through, not just mazes and geography but the other aspects of life.
As we have noted here on numerous occasions, the problem with the map narrative is that it is not sufficiently understood by those who speak in terms of the concept. It is universally acknowledged that maps are not the actual territory, but then it is presumed that line between the objective world and the linguistic world is found in structure and that some dedicative rendering provides the isomorphism.
The tendency to think that a 'map", any map, is actually some kind of "picture" of a "territory" is quite insufficient, and, as we see it, mostly misguided.
The cognitive map concept suffers from the same problems as the concept of 'maps" in general Most of us know by now the famous quote by Korzybski, a polymath of the beginning of the last century, "The Map is NOT the Territory"
"Two important characteristics of maps should be noticed. A map is not the territory it represents, but, if correct, it has a similar structure to the territory, which accounts for its usefulness"
But here we have to differ. The 'map" any map is not truly founded on creating an isomorphism between points in space or any territory and some equivalent drops of pigment on a canvas somewhere in our brain, or, more recently the 'hippocampus
This is obvious but it is usually forgotten by those who speak in the 'lingo" of the map. More recently (see below) investigations into the nature of the hippocampus have begun to focus on this aspect of any 'map" rather than its composite via some sort of little "memory" chunks to resemble a territory or space in which we find ourselves.
This kind of 'Map" that somehow mirrors "all' of our Reality would be an incredibly complex and vast map. The question of "storage" of all this information naturally comes up to those who have happened to think this way.
Recently, even the Mosers, have succumbed to this logical mis-step, based on the assumed relation between "territory" and "map" and found themselves ruminating about the 'storage" for such an infinite collection of mapped detail.
"Probing the brain's extensive capacity for storing memories
http://www.sciencedaily.com/releases/2014/…/141208152518.htm
The brain creates and stores memories in small networks of brain cells, with the memories of events and places stored in a structure called the hippocampus.
Researchers have long wondered if there is an upper limit to our capacity to store memories. Nor do they fully understand how we are able to remember so many events without mixing up events that are very similar.
"This indicates that the brain has an enormous capacity for storage. The ability to create a unique memory or map for every locale explains how we manage to distinguish between very similar memories and how the brain prevents us from mixing up events."
This issue of "storage"is a gross mis-step, and one to which the unfortunate language of neuroscience predisposes those who speak of "maps"
As we see it, the problem is not one of 'storage" but of having available a 'gas station" at which to stop and just pick up and put together the maps you need for that particular trip. Or if you're not driving but walking the streets to get another sort of mapping. The brain must do this on the fly in response to salient cues derived from the events of that moment in time and 'what is' doing" and "where it's going".
For example, we have such maps as roadmaps, or subway maps, or pedestrian street maps, or airplane flying maps, and so on. These are based on the "mode of movement" and the possibilities and limitations of how the "vehicle" or movements themselves.
Moreover, when we, or anyone, as we used to do in the good old days, takes a trip, they must decide which of many maps that are available they wish to use on that given occasion.
Similarly as with the drivers of those days, any talk of a "cognitive map cannot be limited to a depiction of an entire vast "reality" in which the user might find themselves. On the contrary, what the brain must do...as any smart travel must do is constantly make choices of just which map and what sort of map is to be relevant on a given occasion.
In the quest to try to understand the hippocampus, for example, this issue has arisen time and again where the hippocampus was found to have 'place cells" and the researchers were off and running in speaking of the map and of something called "allocentric" space.....so that for them the "outside world" or 'space" in which the animal was navigating was "represented" in some simplistic fashion in a pictorially based hippocampus
These issues were addressed by John O'Keefe and his colleagues in the 1970s through a series of studies that cumulated in an elegant theory proposed in the aptly titled book The Hippocampus as a Cognitive Map (1976).
Strikingly, the locations in which place cells fire appears fixed over repeated exposure to an environment, anchoring themselves to environmental landmarks. O'Keefe and Nadel believed that these place cells form the neurological basis of a cognitive map - a map defined by the interrelations of the different elements that compose an environment.
Does hippocampal activity embody the cognitive map? One should expect the neural instantiation of Tolman’s cognitive map to contain units (neurons) that are fully allocentric, that is, identify places in the environment independent of the subject’s perspective (egocentric direction) and ongoing behavior.
We excerpt a few points from a recent neuroscience study below, which expands on the concept we use to speak of the hippocampus in greater detail than most, tells us: Eventually, as they go through seeking to point to "place cell's as points on the map, then "time cells" (see below) and then have to rely on 'grid cells" (see below). the realization arises that a map is not a picture of a space. but is emergent from the movements and possibilities of the 'user" of the map as he navigates
Complementary Roles of Hippocampus and Medial Entorhinal Cortex in Episodic Laboratory of Neurophysiology of Memory,
http://dx.doi.org/10.1155/2008/258467
"Furthermore, one should expect that the neural ensemble composed of these units would be holistic; that is, all the neuronal representations should be tied to one another and change together between environments. And, if the map is to suit the purpose Tolman proposed in guiding behavior according to expectancies, the map should signal the locations of current goals.
Initially, hippocampal place cells seemed to satisfy key criteria for elements of Tolman’s cognitive map. The first complete study characterized place cells as signaling an animal’s location in the environment independent of egocentric direction and ongoing behavior, as would be expected of the units in an allocentric representation
An expansive literature followed on the initial observations, and many interpreted the results as support for the claim that the neural substrate for the cognitive map lies in the circuitry of the hippocampus
As they say, "In sum, place cells do identify where the animal is when important things happen. But place cells do not carry a reliable allocentric signal, and populations of place cells do not operate as a holistic representation of space or anticipate the locations of goals. Therefore, hippocampal neurons do not have the requisite properties to support Tolman's cognitive map.
By contrast, the findings indicate that hippocampal neurons represent events in the places where they occur, consistent with current views of hippocampal involvement in episodic memory .
The recent discovery of spatial firing patterns in the cortex immediately adjacent to the hippocampus has refocused the search for the cognitive map to a zone within the medial entorhinal area
A majority of the data describes the spatial firing patterns of principal neurons in the medial entorhinal cortex, and more specifically how a proportion of these neurons, the so-called “grid cells,” exhibit an intriguing and unique spatial firing pattern with several interesting properties.
First, the relative angles and densities of peaks within grids of neighboring cells remain invariant both across environments and in response to changes in local cues Second, while grid fields of medial entorhinal neurons remain stable in response to modest environmental manipulation, hippocampal CA3 neurons change their rate of firing (“rate remapping,”
The regularity observed in the firing patterns of grid cells does not appear to be derived from environmental features, or any type of sensory information.
Rather, they appear to code a spatial structure that is generated internally within the brain and use it to scaffold the external environment, much in the same manner that Kant had anticipated.
Interestingly, grid cells have been identified primarily within an area of the brain called the entorhinal cortex, one of the primary neural inputs to the hippocampus, suggesting that grid cells provide a source of the spatial framework upon which cognitive maps of environments are formed.
One of our tenets here is that the ostensible involvement of our hippocampus in two seemingly distinct functions, episodic memory and navigation in space, is really very tragically flawed. First, we believe that there have to be principles by means of which these two activities are seen as dependent on similar functionality in the hippocampal area. Secondly, these two aspects are both evidenced right there in the same tissue for more than mere coincidence because we believe that both of those functions of the hippocampus must come into play in the course of either one of them being the apparent focus function.
One of the key aspects of the use of any map is what we are told when we visit any mall and try to find our way. The informational map says, "You are Here Now"...without that we do not have any way of using that map. That too is a key aspect of any 'cognitive map' use....the awareness of the "now" in terms of its integration into the map. That is where the map use starts.
In a more recent very interesting review by the Mosers , called "Mapping Your Every Move" ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4087187/) they try to work their way out of the vocabulary "muddle" which they inherited via inheritance ofancient notions of "memory" and "maps" and they state:
"We were surprised to find that cells that have no role in our sense of location actually send signals to place cells, because until now, the specific kinds of brain cells found to be involved in navigation—place cells, head direction cells, and grid cells—all have specific jobs. What is the role of the cells that are not actually part of the sense of direction? They send signals to place cells, but what do they actually do? This remains a mystery."
"We also wonder," they tell us, "how the cells in the hippocampus are able to sort out the various signals they receive. Do they “listen” to all of the cells equally effectively all the time, or are there some cells that get more time than others to “talk” to place cells?""
The rather sloppily defined so called "episodic memories" of which so much is made in psychology talk are not more pictures or representations of the past events...just as the map of the hippocampus is not a picture either. In fact these "episodic memories' are inferred because the person is asked about them and then they must speak and recall what and where they were at that "TIME".
In fact, there was a failure by researchers until relatively recently to appreciate that rodents and other mammals might even have the equivalent of 'episodic memory" function in areas of their hippocampus because the poor creatures could not be asked questions and then have to report on those.
Unsurprisingly all sorts of recent research points to the importance of the lateralized specialization of the hippocampus, where the left side tends to be more involved with performance in response to the demands for 'episodic memory" and indeed in a variety of other types of language use, while the right side is more devoted to the navigation in space.
However, what is also found is that these two sides, two facets of the hippocampus must work together....just as the corpus collosum integrates left and right in general for our brains..so the two sides of the hippocampus both must come into play ..either when traveling in space or via episodic memory, traveling in time.
Any one who has ever tried to travel and avoid getting lost, whether with a map or a GPS or by their own devices, realizes that moving through space is a product of both the allowing oneself to be guided by rules of a GPS or map and simply following those AND additionally the use of landmarks or aspects that are recalled from ones experience. We don't do one or the other. IF we do we find ourselves in the typical GPS predicament where we don't verify via integration of our current spatial frame with our previous temporal frame, whether or not the instructions make sense.
This critical interplay between the lateralized aspects of the Hippocampus is discussed in more detail here, one side being prominent in sequential organization that is describable via the flow of time, and the other side being prominent in spatial organization that is describable via movements in space, with both working together….
Lateralized human hippocampal activity predicts navigation based on sequence or place memory
http://www.pnas.org/content/107/32/14466
“The hippocampus is crucial for both spatial navigation and episodic memory,” they say, “suggesting that it provides a common function to both. Here we adapt a spatial paradigm, developed for rodents, for use with functional MRI in humans to show that activation of the right hippocampus predicts the use of an allocentric spatial representation, and activation of the left hippocampus predicts the use of a sequential egocentric representation.
Both representations can be identified in hippocampal activity before their effect on behavior at subsequent choice-points.
Our findings support the idea of lateralized hippocampal involvement during spatial navigation. The right hippocampus is involved in allocentric or map-based navigation, whereas the left hippocampus is involved in the sequential organization of successive choices. Both representations are active in parallel during the training phase of the task. Overall, we suggest that involvement of the left human hippocampus in remembering narrative prose, learning novel sequences, and in supporting sequential egocentric representations in our study, could reflect a more general role in associative processing of sequential elements of an episode.
Our results suggest that, rather than providing a single common function, the two hippocampi provide complementary representations for navigation, concerning places on the right and temporal sequences on the left, both of which likely contribute to different aspects of episodic memory.”
We should note that, to the extent, that there is any occasion to talk about "the self" by current consciousness devotees, they should consider that the team work between the hippocampus and the cortex and the founding of that teamwork on the integration of left and right sides, verbal movement through time and physical movement through space, both must come into play...and form the basis of any 'self concept" before it is further shaped and massaged by other aspects of our brain.
As the Scientific American article says, " Researchers found that the hippocampus is crucial for encoding the order of visual stimuli - whether pictures on a computer screen or landmarks in an environment - and that it expresses unique patterns of activity during overlapping segments of routes through an environment.
The latter finding is particularly important, as it counters a purely place cell model of hippocampal function during navigation.
In such a model it would be expected that hippocampal activity is consistent during overlapping route segments, as a person's physical location is the same through these portions of an environment.
“Time has proven to be a much more elusive concept for both psychology and neuroscience”, they write. “Despite numerous decades of research, the majority of what we know about time representation in the brain comes from two lines of research: how overlapping events are parsed into discrete episodes and the sequential ordering of those events into a temporal framework
This suggests that the hippocampus is involved in representing more than simply the spatial layout of an environment.
A key breakthrough in identifying which types additional information the hippocampus processes was provided by Howard Eichenbaum and his colleagues at Boston University. In a 2011 paper, the authors proposed a new type of neuron population within the hippocampus which they labeled as 'time cells'.
Through a series of studies with rats, it was found that time cell activity could uniquely code successive events and were able to disambiguate overlapping sequences in temporally organized episodes.
As we believe here that final integration depends as well on the mathematical sense that we have, and many of our other species have as well and which is centered in the parietal cortex (but that will have to await another post)
It is there however that vast amounts of information from all areas of the brain are integrated and decisions made in regard to any such "maps" that we may have and how they might relate to "where we are" in our experiences during the events of daily life."
The Mosers ( "Mapping Your Every Move") are now shifting focus to this more sophisticated analysis,
' It is easy to forget,"they say, "as we move effortlessly from home to job, or from job to supermarket to home, the enormous number of processes and steps that make up our ability to navigate. We are now working our way through different aspects of the brain’s navigational system to better understand how all these pieces fit together.
At the moment we are studying what we have dubbed speed cells—cells that react exclusively to the speed of an animal’s movement—and how these types of cells factor in to the navigational equation.
We’re also looking at decision-making. As an animal moves through a labyrinth, it must choose which way to go or what turn to make next. The neurons involved in this decision-making can be found in the prefrontal cortex, which connects to the hippocampus via a small nucleus in the thalamus."
Our belief here s that there is a direct and highly active connecting path between the posterior parietal cortex, where just about every mathematical related function of our brains is centered and evident, via the retrosplenial cortex right down to that area where the still mysterious "grid cells" are located, the entorhinal cortex, which is constantly the means and mode of interface between the hippocampus and the prefrontal cortex. That deeper aspect of brain coordination will , we believe, to rooted in the math genius of the parietal cortex to integrate a wide range of inputs and allow "decisions to be made".
For those who wish to inquire into this aspect here is a good review of the role of the Parietal Cortex as it relates to this type of decision making ( and note that the Parietal is surely where mathematics gets its life and expression in our brains)
Navigating actions through the rodent parietal cortex
doi: 10.3389/fnhum.2014.00293
These decisions will not be made and could not possibly be made on point to point analysis of vast arrays of information and 'matching' of past with present, but have to be processed in a way that is characterized by enhanced speed and efficiency (that allow survival and adaptation" as the availability of any algorithm is to plodding through calculations and data points.
This means that there is a whole lot of 'putting things together" in useful ways based on the user's capabilities and destinations that takes place. It is therefore not sufficient when we speak about sleep and its consolidation, for instance, to just leave it at that, and consider the Slow Wave Sleep to be sufficient conceptually to get our 'map" or "maps' in order.
As the Mosers have recently acknowledged,
"We now know that this coding system works like your own air traffic controller—monitoring every movement you make, knowing every step you ever made, and creating links to every event and experience you have had. Essentially, while your brain is making mental maps to help you navigate, it is also overlaying memories—experiences, smells—onto those maps.
They say, "This ability of the brain to overlay recollections creates a cognitive map—a multilayered collection of memories—rather than a mere cartographic map. It also means that learning how the brain computes navigation is a step toward understanding how networks are built up in the cerebral cortex, the part of the brain that is responsible for imagination, reasoning, and planning—thought processes that make us human. "
What must happen then for the person sleeping is that the organization of that 'map library", let's call it, in terms of events in their lives...must then be enacted in such a way that the work of that night proves useful to finding one's way in the world the next day.
The conclusion (from Scientific American)here is one the share whole heartedly"
"If our experience of time and space share similar neural correlates, it begets a fundamental question: are space and time truly distinct in the mind, or are they the product of a generalized neurocognitive system that allows us to understand the world?
While Kant had much more to say about space than time, contemporary cognitive neuroscientists have begun composing theories to address this question.
One proposal by Demis Hassabis and Eleanor Maguire suggests that the primary function of the hippocampus isn't to think about past and future, or to move about through space per se.
Rather, through cooperation in a larger network spread throughout the brain, the hippocampus allows us to construct a representation of the world in a spatiotemporal context that affords the ability to simulate past experiences in order to make predictions about the future, and to ultimately use this information to direct action in the present.”
They conclude, “Specifically, it suggests that the hippocampus is able to tune its activity to both spatial and temporal aspects of an experience, depending on what type of information needs to be encoded or recalled"
Our view of this "movement' is that it requires essentially moving through two spaces at once and the integration of those 'movements": The movement of our bodies through the three dimensional space of geometry and our placement with its three dimensions and, as well, the one dimensional space normally labelled "time" and our movement through that space via the language we use.
The REM sleep and its progressively increasing dreaming that occurs after the progressively increasing Slow Wave Consolidation events of the night must be giving us not only chunks of 'map" in some generic and vague sense of the word, but "maps based on different episodes in our lives" and useful for different purposes in our lives that might just happen.
And indeed these various guides for behaving must all be indexed and related to each other so that wherever we "are" or "wherever we might be headed" the next day we will be able to call up and use the right one for that mode of movement and that purpose.
Thus what we experience as the dreams of the REM state are the combination and permutation and the "trying on for size" of the work done earlier in the night via the consolidation of the hippocampal content into the cortex.
Do they represent fantasied "wish fulfillments"? Perhaps. But more likely they represent the anticipatory schema by means of which the hippocampus always works, day or night. Do they predict the future? Not exactly, but in some way they do..because they determine what manner of map we just might be using , and how it is put together...so they do predict how we are likely to try to make our way in the world when we are awake....either tomorrow or in the future.
For now, that's a nice part of the story of our nights and dreams that we must appreciate....and indeed that is how evolution must have worked its magic hand to allow all that to happen at night.
We should not close our eyes to all the rest that transpires between Slow Wave Sleep and our Dreams. There are countless maps, in fact an infinite number of them that are made possible by these processes that occur during sleep.
We may never use many of them or most of them. Perhaps sometimes we do, however, have to dig down and find re awaken those "maps" for ourselves. That may be how some mysticism works by encouraging us to lend credence to those dreams. and that is surely how much psychotherapy seeks to bring us 'back in touch" with our dreams...since they just might be the maps we forget to use.
And they might lead us the those "roads less traveled" if we conjure up those maps to guide us if we realize that our journey is very much based on which maps we bring with us...and which bring us.
What we believe is that, while it makes good sense to finally provide a narrative of how our bodies in a three dimensional geometric space move around and find their way to new places and experiences, it also makes sense to speak of our "Selves' are traveling in one dimension, that of verbally mediated (integration of past moments) and how that Self can find its way in that one dimension related to time to new experiences.
Just as we noted occurs whenever we "go" somewhere on whichever roads we travel, there is an essential back and forth that must occur between the past "episodic" elements ordered in time and the present spatial plans and movements oriented in space.
This recent publication deals with \interactions between the prefrontal cortex and the hippocampus as they play a critical role in the modulation of goal-directed self-action and the strengthening of episodic memories
A Prefrontal-Hippocampal Comparator for Goal-Directed Behavior: The Intentional Self and Episodic Memory
10.3389/fnbeh.2015.00323
These authors write "Action plans are essential for successful goal-directed behavior, and are elaborated by the prefrontal cortex. When an action plan is initiated, the prefrontal cortex transmits an efference copy (or corollary discharge) to the hippocampus where it is stored as a working memory for the action plan (which includes the expected outcomes of the action plan).
The hippocampus then serves as a response intention-response outcome working memory comparator.
Hippocampal comparator function is enabled by the hippocampal theta rhythm allowing the hippocampus to compare expected action outcomes to actual action outcomes. If the expected and actual outcomes match, the hippocampus transmits a signal to prefrontal cortex which strengthens or consolidates the action plan.
If a mismatch occurs, the hippocampus transmits an error signal to the prefrontal cortex which facilitates a reformulation of the action plan, fostering behavioral flexibility and memory updating.
The corollary discharge provides the self-referential component to the episodic memory, affording the personal and subjective experience of what behavior was carried out, when it was carried out, and in what context (where) it occurred."
However as we noted above, the exquisite "mathematical sense of the parietal cortex" must play a role here as it does in most of our actions, although mathematics is not fully appreciated as being at the core of our Selves and of our Brain Function.
It's our central mathematical sense and capacity that allows such an "integration" and in the course of that integration we find ourselves experiencing a Self as an index of that integration and not located within either time or space data points.
Thus in "Navigating actions through the rodent parietal cortex (see the link above)
they write, "parietal neurons encoded route progress irrespective of spatial position or direction of motion, and the fact that they did so equally well in darkness or light implied a possible function in path integration.
Based on the finding that PPC firing fields, unlike hippocampal place cells, scaled flexibly to match maze segments when they were lengthened or shortened, it was concluded that PPC cells were more tightly linked to the reference frame of the animals' route than a world-based spatial reference frame
Many of the basic questions relating to cognitive motor functions, though, are not necessarily specific to one species or another—such as the time course over which a movement plan evolves relative to action initiation, the cortical representation of movement goals, or the computational contribution of common anatomical pathways.
Evolutionary date implies s that place cells and grid cells date back at least 65–100 million years to the common ancestor of placental mammals and it is quite likely that such spatial circuitry arose long before in even simpler, more ancient organisms.
The same principle applies to the parieto-frontal pathway, which is another common feature of all mammalian nervous systems.
As opposed to generating spatial maps, it enables the synthesis of efficient movements and meaningful interactions with objects within those spatial maps, computing behavioral solutions to everyday problems which terrestrial vertebrates have encountered for countless millennia."
In the end, it is not some indefinable, dualistically problematic, Self, however, which magically travels and puts together various decisions and game plans for moving through space and/or time...but it is the need to conduct those movements by an organism's brain which requires it to experiences its moments of life via a 'Self".
The "reality" of the Self leads to much, far too much, endless quibbling about issues that only beg of our understanding of that notion, many of them dependent on 'locating" a "Self" as an entity, or, as we prefer to say, "entitizing it" as existing in either/or both space and time.
That is how we put 'space and time" together to function as organisms That is how the 'self" can be considered quite "REAL" but not situated in either space or time. In fact our "self" and our "self talk" are ordered very much as are the natural numbers in one dimension as we know it is the "measure" of time just as much as our geometric "maps" of our movements and their possibilities is a measure of “space"
If, however, we consider what we believe to be the "reality" status of the "center of gravity" when we discuss natural law via Newtonian theory, we realize that this concept of “self” not outside of space and time but being a manifestation of our computation of space and time, is as "real" as anything of which we can speak, as it allows us to engage in the vary acts of speaking that describe how movement occurs in space and change arises over time.
As Anais Non wrote, "Dreams pass into the reality of action. From the actions stems the dream again; and this interdependence produces the highest form of living." -