Category Archives: memory

Meaning of consciousness - part 3

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What is the function of consciousness? Is the function thinking? There is type 1 thinking, unconscious thinking, and type 2 thinking, which we are conscious of. But it appears that what we are really conscious of is working memory, and not conscious of how an item is created and put in working memory. Type 2 thought is just unconscious processes using working memory as a tool for certain sorts of processing (some language, step-wise logic chains or calculations for example) and the contents of working memory are rendered into consciousness. If type 2 thinking is a function of consciousness then it implies that working memory is somehow dependent of consciousness.

We tend to associate moral responsibility with decisions made consciously, but for thirty of so years there has been growing evidence that we make decisions and execute actions unconsciously before registering them consciously. Libet’s experiment and its descendants just will not go away in spite of decades of trying. The notion that free will and ‘free won’t’ are functions of consciousness just will not work. What seems to be in consciousness is a metaphorical note saying, “I intended this action, I did it, and I morally own it.” There is a phrase, ‘fringe qualia’, which seem to be metaphorical notes about non-sensory information: states of mood and emotion, recognitions, ownership of actions and thoughts, important so take note, and so on. None of these arise within consciousness; they are add from and by unconscious processes. Consciousness can register responsibility for an action but not actually cause the action. There is a theory that consciousness is required to insure that there are not overlaps and gaps in motor plans. The idea is that the motor system needs a working model of the body and environment to proof its plans. This is probably true but not necessarily.

Is the function to give us a sense of self? The impression we have is that we are seeing the world through a hole in our heads around the bridge of the nose from about an inch and a half or so into the brain. But the ‘self’ is a complex mixture of what we control with our muscles, the sensory feelings from inside our bodies, sensory signals from the skin, our memories making a personal narrative, and very especially our consciousness. We naturally seem to identify with some sort of conscious ‘me/I’. Consciousness, as an awareness of ‘ourselves in the world’, has to create the watcher, listener, actor, that is in the world. Self seems essential to consciousness but not perhaps the central function.

Can memory be a function of consciousness? If we think about it, consciousness and memory do seem to go together, at least episodic memory. We remember things that we are conscious of and not things that we are unconscious of. We are aware we have been unconscious when there is a discontinuity in our memory train. It does not seem to require some sort of translation to bring a memory into consciousness – it appears to happen easily. It seems that imaginings are constructed of bits and pieces of memories and they also seem to fit into consciousness without effort. In order to remember experiences, we have to have experiences, and what is it that we experience – it is consciousness. the action. Consciousness can be experimentally tricked into being wrong, taking responsibility for actions the individual did not cause. But we are usually right. Knowing which actions we intentionally cause must be important to judging outcomes and learning from experience. Consciousness seems connected to various short-term memory systems: working memory, sensory memory, verbal memory. Episodic memory also is held together by a continuous self, all events and episodes happen to the same self. Consciousness may be what is prepared for episodic memory, the ‘leading edge’ of episodic memory, so to speak. Or it may be a monitor or newly formed memories, like the monitor head on a tape recorder. The creation of episodic memory would certainly be a function worth the biological cost of consciousness. Being part of the episodic memory system would fit with being an important anchor of the ‘self’. Even the metaphorical notes of the fringe qualia would fit it this episodic memory.

The question is – what exactly is the dependency of memory on consciousness. Episodic memory, imagination and consciousness seem to have the same basic nature or structure or coding. And this structure must be the vehicle of the subjective experience. I have looked for a clear statement of this idea in the literature and the closest seems to be the global workspace of Bernard Baars. He proposed a architecture that would give momentary active subjective experience of events in working memory, consciousness, recalled memory, inner speech and visual imagery.

Do other animals have consciousness? It certainly seems reasonable to assume that most vertebrates do. The source of the awake state comes from deep in the brain stem. Activity from there activates higher regions, the thalamus in particular. Awake, in animals, may not necessarily mean aware, but it would be wiser to assume awareness until proven otherwise, than to do as we have been doing, assume no awareness until proven otherwise. The cerebral cortex does not itself mount consciousness, it is done in partnership with the thalamus, probably be driven by the thalamus. It would seem that a rudimentary consciousness would be possible without a cerebral cortex. It has been found recently that split-brain subjects have one consciousness and not two. This implies that the source of consciousness is is not in the cerebral hemispheres, but must be in some lower region. But the vivid detail of the content must be from the cortex.

Still we do not have a explanation of the subjective nature of consciousness yet but that is for part 4.

 

Doing science backwards

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A recent article, (Trettenbrein, P. (2016); The Demise of the Synapse As the Locus of Memory: A Looming Paradigm Shift?; Frontiers in Systems Neuroscience, 10), questions what many consider settled science – plastic changes to synapses are the basis of learning and memory – may not be correct. Thanks to Neurosceptic for noting this paper (here).

“Actually, as of today, large parts of the field have concluded, primarily drawing on work in neuroscience, that neither symbolism nor computationalism are tenable and, as a consequence, have turned elsewhere. In contrast, classical cognitive scientists have always been critical of connectionist or network approaches to cognitive architecture.”Trettenbrein is in the classical cognitive scientist camp.

First Trettenbrein assumes that the brain is a Turing machine. In other words that the coinage of thought is symbols and that they are manipulated by algorithms (programs) that write to a stable memory and read from it. The brain is assumed to deal in representation/symbols as variables, stepwise procedures as programs and random access memory, giving together a Turing machine. “The crucial feature of a Turing machine is its memory component: the (hypothetical) machine must possess a read/write memory in order to be vastly more capable than a machine that remembers the past only by changing the state of the processor, as does, for example, a finite-state machine without read/write memory. Thus, there must be an efficient way of storing symbols in memory (i.e., writing), locating symbols in memory (i.e., addressing), and transporting symbols to the computational machinery (i.e., reading). It is exactly this problem, argue Gallistel and King (2009), that has by and large been overlooked or ignored by neuroscientists. …”

“Synaptic plasticity is widely considered to be the neurobiological basis of learning and memory by neuroscientists and researchers in adjacent fields, though diverging opinions are increasingly being recognized. From the perspective of what we might call “classical cognitive science” it has always been understood that the mind/brain is to be considered a computational-representational system. Proponents of the information-processing approach to cognitive science have long been critical of connectionist or network approaches to (neuro-)cognitive architecture, pointing to the shortcomings of the associative psychology that underlies Hebbian learning as well as to the fact that synapses are practically unfit to implement symbols.” So an assumption that we have a Turing machine dictates that it needs a particular type of memory which is difficult to envisage with plastic synapses.

I like many others believe, science starts with observations and moves on to explanations of those observations, or to state it differently, the theories of science are based on physical evidence. It is not science to start with a theoretical assumption and argue from that assumption what has to be. Science starts with ‘what is’ not ‘what has to be’.

Trettenbrein is not thinking that the brain resembles a computer in many ways (computer metaphor), he is thinking that it IS a computer (actual Turing machine). If the brain is an actual computer than it is a Turing machine, working in a stepwise fashion controlled by an algorithmic program. Then he reasons that the memory must be individual neurons that are - what? Perhaps they are addressable items in the random access memory. Well, it seems that he does not know. “To sum up, it can be said that when it comes to answering the question of how information is carried forward in time in the brain we remain largely clueless… the case against synaptic plasticity is convincing, but it should be emphasized that we are currently also still lacking a coherent alternative.” We are not clueless (although there are lots of unknowns) and the case for synaptic plasticity is convincing (as it has convinced many/most scientists) because there is quite a bit of evidence for it. But if someone starts with an assumption, then looks for evidence and finds it hard to produce – they are doing their science backwards.

Trettenbrein is not doing neuroscience, not even biology, in fact not even science. There are a lot of useful metaphors that we use to help understand the brain but we should never get so attached to them that we believe they can take the place of physical evidence from actual brains.

Just because we use the same words does not mean that they describe the same thing. A neurological memory is not the same as a computer memory. Information in the neurological sense is not the same as the defined information of information theory. Brain simulations are not real brains. Metaphors give resemblances not definitions.

Time travel is not uniquely human

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There are constantly statements about what abilities humans have that are unique. One of these is mental time travel. Decades ago Tulving put forward the notion of episodic memory and at the same time stated his opinion that it was unique to humans and that animals do not have episodic memory or a conscious experience of remembering. Suddendorf and Corballis put forward the notion of mental time travel: “the human ability to travel mentally in time constitutes a discontinuity between ourselves and other animals”. Lately Corballis has changed his mind: “Mental time travel has neurophysiology underpinnings that go far back in evolution, and may not be as some (including myself) have claimed, unique to humans.” Other animals may experience remembering specific events and may experience the planning of future events. In fact, I would find it difficult to explain their behavior if they did not have these abilities.

Imaging the old grandmother elephant leading her family to the bones of dead relatives, where they can touch and look at bones of specific dead loved ones. We know elephants are conscious even self-conscious, have theory of mind, have long memories, know and can navigate huge territories and know individual elephants that are not part of their group. I find it very difficult to imagine that when they touch the bones they have come to visit, they are not experiencing vivid memories of their dead relatives.

Time travel has been indicated in rats, pigeons, jays and dolphins but without convincing all critics. Now another study is even more convincing. (Gema Martin-Ordas, Dorthe Berntsen, Josep Call; Memory for Distant Past Events in Chimpanzees and Orangutans; Current Biology, Volume 23, Issue 15, p1438–1441, 2013) Here is the abstract:

Determining the memory systems that support nonhuman animals’ capacity to remember distant past events is currently the focus an intense research effort and a lively debate. Comparative psychology has largely adopted Tulving’s framework by focusing on whether animals remember what-where-when something happened (i.e., episodic-like memory). However, apes have also been reported to recall other episodic components after single-trial exposures. Using a new experimental paradigm we show that chimpanzees and orangutans recalled a tool-finding event that happened four times 3 years earlier (experiment 1) and a tool-finding unique event that happened once 2 weeks earlier (experiment 2). Subjects were able to distinguish these events from other tool-finding events, which indicates binding of relevant temporal-spatial components. Like in human involuntary autobiographical memory, a cued, associative retrieval process triggered apes’ memories: when presented with a particular setup, subjects instantaneously remembered not only where to search for the tools (experiment 1), but also the location of the tool seen only once (experiment 2). The complex nature of the events retrieved, the unexpected and fast retrieval, the long retention intervals involved, and the detection of binding strongly suggest that chimpanzees and orangutans’ memories for past events mirror some of the features of human autobiographical memory.

It seems unscientific to assume the answer before asking the question. Why was it assumed that animals did not feel? Then why assume that they did not think? Then, anyway they were not conscious, right? And now that they cannot consciously remember personal events? There was tool using, then tool making, and then serial tool use, all disproved. The only thing that has come close is that animals have no language ability. Even that may be over turned by whales. This drive to find human uniqueness and the stubbornness in defending it, is unbecoming to science. It is not creationism – but somehow it has a tiny bit of the same odour. Science should be looking at why animals (including humans) have a episodic memory, how it helps them think, plan, react and not whether it has some mystical ‘autonoetic’ insight to its conscious experience in humans but not other animals.

To see others as we see ourselves

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In psychology there is a theory about the ‘fundamental attribution error’, the error in how we attribute causes to actions. When we look at our own actions, they are caused by our cognition in the circumstances in which we are deciding what to do. When we look at the actions of others, they are caused by their personality or character traits. So we do not really take into consideration the circumstances of others when we judge their actions. Nor do we consider the fixed patterns of our own behavior that do not enter into our conscious thoughts when we judge our own actions. We just do what is reasonable at the time and they just do what they always do. I can be too busy to help while they can be too thoughtless. This is a problem for us but at least we can understand the problem and occasionally overcome it. (My way to deal with it is to just assume that people are intelligent and well-meaning most of the time. If they do something that seems dumb or nasty, I look at the circumstances to see if there is a reasonable explanation. There very often is. I realize that this view of my own behaviour is somewhat ironic in its internal attribution – well nothing is perfect.)

But this problem with attribution is much greater than human social interaction. We do the same thing with animals. Elephants were tested for self recognition with the mirror test. If they recognize a black spot appearing on their forehead then it is clear that they know it is their forehead. Elephants failed the test and so they were said to not have a sense of self. It turned out that the mirrors used were too small. The elephants could not make out that it was an elephant in the mirror let alone themselves. If we start out underestimating an animals intelligence, and either not test that assumption or test it in a way that is inappropriate for the animal – then we are making a big attribution error.

There is an assumption on the part of many that vertebrate brains are quite different in the various sorts of vertebrates. This is not true! All animals with a spine have the same brain pattern with the same regions. All vertebrates have seven parts and no more or less: accessory olfactory bulb; cerebellum; cerebral hemispheres; medulla oblongata; olfactory bulb; optic tectum; and pituitary gland. There are differences in size, details and subdivisions, but there are no missing parts. (R.G. Northcutt; Understanding Vertebrate Brain Evolution; Integr. Comp. Biol. 2002 42(4) 743-756). There is every reason to believe that the brain works in fundamentally the same way in mammals, birds, reptiles, amphibians and fish. And by and large, this same pattern of brain has the same functions – to move, find/eat food, escape enemies and so on. It is obvious that animals have motor control and sensory perception.

What evidence is there that other animals have emotions, memory, or consciousness? Can they be automatons with no mental life? The reports trickle in year after year that add to the evidence that animals have a mental life similar to ours.

Reptiles probably dream. “Most animal species sleep, from invertebrates to primates. However, neuroscientists have until now only actively recorded the sleeping brains of birds and mammals. Shein-Idelson et al. now describe the electrophysiological hallmarks of sleep in reptiles. Recordings from the brains of Australian dragons revealed the typical features of slow-wave sleep and rapid eye movement (REM) sleep. These findings indicate that the brainstem circuits responsible for slow-wave and REM sleep are not only very ancient but were already involved in sleep dynamics in reptiles.” (Shein-Idelson, Ondracek, Liaw, Reiter, Laurent; Slow waves, sharp waves, ripples, and REM in sleeping dragons; Science 2016 Vol 352 (6285) 590-596) These wave types in sleep also are evidence for a memory system similar to ours.

Fish don’t make noise or wave their fins to show emotion but that does not mean they don’t have emotions. “Whether fishes are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fishes is an inability to show stress-induced hyperthermia (SIH), a transient rise in body temperature shown in response to a variety of stressors. This is a real fever response, so is often referred to as ‘emotional fever’. It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups. According to this view, lack of emotional fever in fishes reflects a lack of consciousness. We report here on a study in which six zebrafish groups with access to a temperature gradient were either left as undisturbed controls or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher temperatures, achieving an estimated rise in body temperature of about 2–48C. Thus, zebrafish clearly have the capacity to show emotional fever. While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes.” (Rey, Huntingford, Boltana, Vargas, Knowles, Mackenzie; Fish can show emotional fever: stress-induced hyperthermia in zebrafish; 2015 Proc. R. Soc. B 282: 20152266)

One of the problems with comparing the brains of different vertebrates is that they have been named differently. When development is followed through the embryos, many differently named regions should really have a single name. Parts of the tectum are the same as our superior colliculus and they have been found to act in the same way. They integrate sensory stimuli from various senses. They can register whether events are simultaneous. For example in tadpoles the tectum can tell if a sight and vibration stimulus are simultaneous. That is the same function with the same development in the same part of the brain in an amphibian and a mammal. (Felch, Khakhalin, Aizenmen; Multisensory integration in the developing tectum is constrained by the balance of excitation and inhibition. 2016 eLife 5)

We should be assuming that other vertebrates think like we do to a large extent – just as we should assume that other people do - and try to understand their actions without an attribution error.

Out of the box

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I have not been reading science reports as much of late and have not been writing. My mind has wandered to less conventional ideas. I hope you find them entertaining and maybe a little useful.

Because we got stuck years ago with a computer model for thinking about the brain, we may have misjudged the importance of memory. It is seen as a storage unit. Memory has been shown to be a very active thing, but still seen as an active storage thing. We know it is involved with learning and imagining as well as recalling, but thinking functions are seen as just how we may use what is remembered. No matter how people think of the brain or the mind, memory stays over to the side as a separate store. Even though there are many types of memory (implicit, explicit and working for a start) they are still just storage. They are seen as the RAM and hard disks of the mind.

Suppose (just for an exercise) that we had started out putting memory in the role of an operating system when we first started using the computer model to get our bearings on thought. Think of it as a form of Windows rather than a hard disk. Actually, this is not as far-fetched as you may think. There is a system called MUMPS which runs on a computer without any other operating system under it and consists of a single large data storage structure and a computer language to use the data. It was invented in the ’60s and is still used in many medical computer systems because it is very fast, and accurate in that it does not impose format restrictions on the data. I am not supposing that the brain is like MUMPS, far from it; but simply pointing out that there is more than one way to view the role of memory.

So – back to the ‘what if’.

The interesting thing about the brain is its plasticity. The changes are not rare or special but are happening all the time. Whatever the brain does leaves it changed a bit. The greatest producers of change are remembering, learning, imagining, recalling - or anything that involves the memory. Every time one neuron causes another neuron to fire, the synapses between those two neurons are strengthened. Remembering makes changes to the connectivity of the brain or in computer terms it changes the architecture of the hardware.

Connecting separate memories (memory integration) is how we make inferences; chains of inferences lead to decisions. If my memory A is connected to B, and B is connected to C, than C and A can be connected. That is the sort of thing that happens when we think. Recognition is also a memory function. If I say it is greenish, you might think of vegetation or Ireland or toys. If it is upside down, it is not Ireland but other things become more likely. But if I then say that it is furry – well then it is likely to be a sloth or some silly soft toy. Saying that it moves slowly would clinch it. The word green is connected to a great many other words and so is upside down but their intersection is small. It gets tiny when it must overlap with the fur connections.

Memory is waiting to help. When I am someplace doing something with some aim, everything I sense and everything I know about the place and the activity, all the memories that may be useful to me are alerted and stand primed, really to be useful. I would not be aware of all these alerted memories until I use them and even then I might be unaware of them. It is actually extremely difficult (probably impossible) to have memory-free thoughts. Even something like vision is not just stimuli processed into image, it is wrapped in memories to connect one moment with the next, predict what will be next, identify objects and give meaning to the image.

The mechanisms that store memories appear to provide our sense of place, the consecutive order of events, the flow of time and the assigning of cause and effect links. It even involves part of our sense of self. We either store memories that way because that is how we understand the world or we understand the world that way because of how we remember it. These sound like two opposed ideas but really are the same idea if memory is in effect our ‘operating system’.

We can see memory as the medium of our thoughts and the mechanisms for using memories as part of our cognition. But it could be seen as even more fundamental than that. We live in a model of the world and ourselves in that world. We project that model around us. We seem to view the projection through a hole in our heads from a vantage point a couple of inches behind the bridge of the nose. It is not just visual but includes sound and other senses. This model houses our consciousness but also our recollections and our imaginings. It is a sort of universal pattern or framework for consciousness, memory and a fair bit of cognition. It seems possible that this framework and the elements in it may be one of the ways that different parts of the brain can share information. (Like Baar’s global workspace and similar theories.)

But what could be the connection between consciousness and explicit memory? Again we can look at something that is more familiar – a tape recorder. The little head with its gap writes on the tape as the tape passes by it. There is another head very close to the writing head that reads the tape. The tape can be monitored using this head and earphones almost simultaneously with the sounds being recorded, but they are the sounds that have just been recorded being read from the tape. This may be what consciousness is – an awareness of what has just been put in memory. There is something to think about.

 

Two things on language

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There are a couple of interesting reports about language.

First, it has been shown that repeating something aloud helps us remember it. But a recent study goes further – we remember even better if we repeat it aloud to someone. The act of communication helps the memory. The paper is: Alexis Lafleur, Victor J. Boucher. The ecology of self-monitoring effects on memory of verbal productions: Does speaking to someone make a difference? Consciousness and Cognition, 2015; 36: 139 DOI:10.1016/j.concog.2015.06.015.

From ScienceDaily (here) Previous studies conducted at Professor Boucher’s Phonetic Sciences Laboratory have shown that when we articulate a sound, we create a sensory and motor reference in our brain, by moving our mouth and feeling our vocal chords vibrate. “The production of one or more sensory aspects allows for more efficient recall of the verbal element. But the added effect of talking to someone shows that in addition to the sensorimotor aspects related to verbal expression, the brain refers to the multisensory information associated with the communication episode,” Boucher explained. “The result is that the information is better retained in memory.“

No one can tell me that language is not about and for communication.

The second item is reported in ScienceDaily (here) Infants cannot perceive the difference between certain sounds when their tongue is restricted with a teether. They have to be able to mimic the sounds in order to distinguish them. The paper is: Alison G. Bruderer, D. Kyle Danielson, Padmapriya Kandhadai, and Janet F. Werker. Sensorimotor influences on speech perception in infancy. PNAS, October 12, 2021 DOI: 10.1073/pnas.1508631112.

From ScienceDaily: …teething toys were placed in the mouths of six-month-old English-learning babies while they listened to speech sounds-two different Hindi “d” sounds that infants at this age can readily distinguish. When the teethers restricted movements of the tip of the tongue, the infants were unable to distinguish between the two “d” sounds. But when their tongues were free to move, the babies were able to make the distinction. Lead author Alison Bruderer, a postdoctoral fellow in the School of Audiology and Speech Sciences at UBC, said the findings call into question previous assumptions about speech and language development. “Until now, research in speech perception development and language acquisition has primarily used the auditory experience as the driving factor,” she said. “Researchers should actually be looking at babies’ oral-motor movements as well.”

hey say that parents do not need to worry about using teething toys but a child should also have time to freely use their tongue for good development.

 

Memory switch

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A new tool has been used for the first time to look at brain activity - ribosomal profiling. The method identifies the proteins that are being made at any time. Ribosomes make proteins using messenger RNA that was copied from the DNA of genes. The method is to destroy all the messenger RNA that is not actually within a ribosome, or in other words, being actively used to make protein. The protected RNA can be used to identify the genes that were being translated into proteins at the moment that the cell was broken and the free RNA destroyed.

ScienceDaily reports on a press release from the Institute for Basic Science describing the use of this technique to study memory formation. (here) The research was done in the IBS Center for RNA Research and Department of Biological Sciences at Seoul National University. There is a on-off switch for formation of memories that is based on changes in protein production.

“When an animal experiences no stimulus in an environment the hippocampus undergoes gene repression which prevents the formation of new memories. Upon the introduction of a stimulus, the hippocampus’ repressive gene regulation is turned off allowing for new memory creation, and as Jun Cho puts it, “Our study illustrates the potential importance of negative gene regulation in learning and memory”.”

I assume this research will appear in a journal paper and that the technique will be used in other studies of the brain. It is always good to hear of new methods being available.

Islands and ocean of memory

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Episodic memories are tagged with information about time and place. If we remember an event then it is almost certain we will remember where it happened and where it lies in the temporal sequence of events. Research has shown that an activity pattern in a part of the brain involved in memory, the entorhinal cortex, feeds where and when information to the hippocampus which forms the new memory.

The research is reported in a recent paper: Takashi Kitamura, Chen Sun, Jared Martin, Lacey J. Kitch, Mark J. Schnitzer, Susumu Tonegawa. Entorhinal Cortical Ocean Cells Encode Specific Contexts and Drive Context-Specific Fear Memory. Neuron, 2015; DOI: 10.1016/j.neuron.2015.08.036.

The entorhinal area involved has been likened to an ocean of context specific ‘where’ cells with islands of ‘when’ cells. The ocean cells signal the CA3 cells of the hippocampus and the island cells signal the CA1 cells. If ocean cells are blocked, animals cannot learn to connect fear with a particular environment. Island cells seem to react to the speed an animal is moving at and manipulating their signals changed the gap between events being linked in an animals memory. This is probably one of many ingredients in the processing of time-and-space.

Absract: “Forming distinct representations and memories of multiple contexts and episodes is thought to be a crucial function of the hippocampal-entorhinal cortical network. The hippocampal dentate gyrus (DG) and CA3 are known to contribute to these functions, but the role of the entorhinal cortex (EC) is poorly understood. Here, we show that Ocean cells, excitatory stellate neurons in the medial EC layer II projecting into DG and CA3, rapidly form a distinct representation of a novel context and drive context-specific activation of downstream CA3 cells as well as context-specific fear memory. In contrast, Island cells, excitatory pyramidal neurons in the medial EC layer II projecting into CA1, are indifferent to context-specific encoding or memory. On the other hand, Ocean cells are dispensable for temporal association learning, for which Island cells are crucial. Together, the two excitatory medial EC layer II inputs to the hippocampus have complementary roles in episodic memory.”

Forming memories

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The contents of episodic memory (but not other types of memory) are formed in the medial temporal lobe (the hippocampus and neocortical areas adjacent to it, including the entrorhinal area). This part of the brain seems to pick out moments of our conscious experience and commit them to memory. A recent paper looks at individual neurons involved in this memory formation. (Matias J. Ison, Rodrigo Quian Quiroga, Itzhak Fried. Rapid Encoding of New Memories by Individual Neurons in the Human Brain. Neuron, 2015; 87 (1): 220 DOI: 10.1016/j.neuron.2015.06.016)

The researchers used the method of asking cooperation from patients who are awaiting surgery for epilepsy and have been fitted with electrodes in a particular area of the brain to locate the exact focus of the epilepsy. This is probably the only ethical way in which studies can be done involving the recording from individual neurons in humans.

It is thought that memories are established by associations. But it is a puzzle how associations can be made by single exposures to unique natural events. The researchers showed patients many images of people, animals and places. Images that activated a single neuron from those that were being recorded were set aside for use. The images were made into composites where one person or animal image was put into one place image to appear to be the person/animal in that setting. The neurons that had responded to one of the images but not the other began responding to both original images after being exposed to the composite. A neuron was forming an association of the two parts of the composite. Associations formed rapidly in an all-or-nothing manner.

After rapid capture, these associations are probably manipulated and consolidated (or destroyed) in the production of more permanent and complex memories.

Abstract: “The creation of memories about real-life episodes requires rapid neuronal changes that may appear after a single occurrence of an event. How is such demand met by neurons in the medial temporal lobe (MTL), which plays a fundamental role in episodic memory formation? We recorded the activity of MTL neurons in neurosurgical patients while they learned new associations. Pairs of unrelated pictures, one of a person and another of a place, were used to construct a meaningful association modeling the episodic memory of meeting a person in a particular place. We found that a large proportion of responsive MTL neurons expanded their selectivity to encode these specific associations within a few trials: cells initially responsive to one picture started firing to the associated one but not to others. Our results provide a plausible neural substrate for the inception of associations, which are crucial for the formation of episodic memories.”

The learning of concepts

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I once tried to learn a simple form of a Bantu language and failed (not surprising as I always fail to learn a new language). One of the problems with this particular attempt was classes of nouns. There were 10 or so classes, each with their own rules. Actually it works like the gender of nouns in most European languages, but it is much more complex and unlike gender it is less arbitrary. The nouns are grouped in somewhat descriptive groups like animals, people, places, tools etc. Besides the Bantu languages there are a number of other groups that have extensive noun classes, twenty or more.

Years ago I found the noun classes inexplicable. Why did they exist? But there has been a number of hints that it is a quite natural way for concepts to be stored in the brain – faces stored here, tools stored there, places stored somewhere else.

A recent paper (Andrew James Bauer, Marcel Adam Just. Monitoring the growth of the neural representations of new animal concepts. Human Brain Mapping, 2015; DOI: 10.1002/hbm.22842) studies how and where new concepts are stored.

Their review of previous finds illustrates the idea. “Research to date has revealed that object concepts (such as the concept of a hammer) are neurally represented in multiple brain regions, corresponding to the various brain systems that are involved in the physical and mental interaction with the concept. The concept of a hammer entails what it looks like, what it is used for, how one holds and wields it, etc., resulting in a neural representation distributed over sensory, motor, and association areas. There is a large literature that documents the responsiveness (activation) of sets of brain regions to the perception or contemplation of different object concepts, including animals (animate natural objects), tools, and fruits and vegetables. For example, fMRI research has shown that nouns that refer to physically manipulable objects such as tools elicit activity in left premotor cortex in right-handers, and activity has also been observed in a variety of other regions to a lesser extent. Clinical studies of object category-specific knowledge deficits have uncovered results compatible with those of fMRI studies. For example, damage to the inferior parietal lobule can result in a relatively selective knowledge deficit about the purpose and the manner of use of a tool. The significance of such findings is enhanced by the commonality of neural representations of object concepts across individuals. For example, pattern classifiers of multi-voxel brain activity trained on the data from a set of participants can reliably predict which object noun a new test participant is contemplating. Similarity in neural representation across individuals may indicate that there exist domain-specific brain networks that process information that is important to survival, such as information about food and eating or about enclosures that provide shelter.”

Their study is concerned with how new concepts are formed (they have a keen interest in education). “Collectively, the results show that before instruction about a feature, there were no stored representations of the new feature knowledge; and after instruction, the feature information had been acquired and stored in the critical brain regions. The activation patterns in the regions that encode the semantic information that was taught (habitat and diet) changed, reflecting the specific new concept knowledge. This study provides a novel form of evidence (i.e. the emergence of new multi-voxel representations) that newly acquired concept knowledge comes to reside in brain regions previously shown to underlie a particular type of knowledge. Furthermore, this study provides a foundation for brain research to trace how a new concept makes its way from the words and graphics used to teach it, to a neural representation of that concept in a learner’s brain.”

This is a different type of learning. It is conceptual knowledge learning rather than learning an intellectual skill such as reading or a motor skill such as juggling.

The storage of conceptual knowledge appears to be quite carefully structured rather than higgly piggly.

Here is the abstract. “Although enormous progress has recently been made in identifying the neural representations of individual object concepts, relatively little is known about the growth of a neural knowledge representation as a novel object concept is being learned. In this fMRI study, the growth of the neural representations of eight individual extinct animal concepts was monitored as participants learned two features of each animal, namely its habitat (i.e., a natural dwelling or scene) and its diet or eating habits. Dwelling/scene information and diet/eating-related information have each been shown to activate their own characteristic brain regions. Several converging methods were used here to capture the emergence of the neural representation of a new animal feature within these characteristic, a priori-specified brain regions. These methods include statistically reliable identification (classification) of the eight newly acquired multivoxel patterns, analysis of the neural representational similarity among the newly learned animal concepts, and conventional GLM assessments of the activation in the critical regions. Moreover, the representation of a recently learned feature showed some durability, remaining intact after another feature had been learned. This study provides a foundation for brain research to trace how a new concept makes its way from the words and graphics used to teach it, to a neural representation of that concept in a learner’s brain.”