Wednesday, March 19, 2014

Intention: The Limits of the Imagination and Memory

Every thing possible to be believ'd is an image of truth.

My intention is to memorize 1000+ items in this proportion:

100 Poems (65 Realized) POESIS
100 Prose Passages (20 Realized) SCRIPTUM
100 Systems or Lists (40 Realized) OSSA
100 Songs of My Own (50 Realized) CANTICUM
100 Songs of Others (50 Realized) ALTER CANTICUM
100 Notions about Numbers - MATHEMATICA
100 Jokes (15 Realized) IOCULARIA
154 Sonnets by Shakespeare - QUATIT HASTATUS CANTUUM
146 Classical Melodies - MUSICA - Recognition and Recall of Titles and Composers

PICTURA - Recognition and Recall of Titles and Artists - Immediate Focus on the Louvre and National Museum

What Is the Memory Capacity of the Human Brain?

Although there must be a physical limit to how many memories we can store, it is extremely large. We don’t have to worry about running out of space in our lifetime. 
The human brain consists of about one billion neurons. Each neuron forms about 1,000 connections to other neurons, amounting to more than a trillion connections. If each neuron could only help store a single memory, running out of space would be a problem. You might have only a few gigabytes of storage space, similar to the space in an iPod or a USB flash drive. Yet neurons combine so that each one helps with many memories at a time, exponentially increasing the brain’s memory storage capacity to something closer to around 2.5 petabytes (or a million gigabytes). For comparison, if your brain worked like a digital video recorder in a television, 2.5 petabytes would be enough to hold three million hours of TV shows. You would have to leave the TV running continuously for more than 300 years to use up all that storage.

Multi Store Model of Memory - Atkinson and Shiffrin, 1968

Solomon Shereshevsky

Shereshevskii participated in many behavioral studies, most of them carried out by the neuropsychologist Alexander Luria over a thirty-year time span. He met Luria after an anecdotal event in which he was told off for not taking any notes while attending a work meeting in the mid-1920s. To the astonishment of everyone there (and to his own astonishment in realising that others could apparently not do so), he could recall the speech word by word. Along the years Shereshevsky was asked to memorize complex mathematical formulas, huge matrices and even poems in foreign languages and did so in a matter of minutes. Despite his astounding memory performance, Shereshevsky scored no better than average in intelligence tests. 
On the basis of his studies, Luria diagnosed in Shereshevsky an extremely strong version of synaesthesia, fivefold synaesthesia, in which the stimulation of one of his senses produced a reaction in every other. For example, if Shereshevsky heard a musical tone played he would immediately see a colour, touch would trigger a taste sensation, and so on for each of the senses. The images that his synaesthesia produced usually aided him in memorizing.

Funes, The Memorious by Jorge Luis Borges

He was, let us not forget, almost incapable of ideas of a general, Platonic sort. Not only was it difficult fo rhim to comprehend that the generic symbol dog embraces so many unlike individuals of diverse size and form; it bothered him that the dog at three fourteen (seen from the side) should have the same name as the dog at three fifteen (seen from the front).

Acquisition of a memory skill - K.A. Ericcson, W.G. Chase, S. Faloon - Science 6 June 1980: Vol. 208 no. 4448 pp. 1181-1182

After more than 230 hours of practice in the laboratory, a subject was able to increase his memory span from 7 to 79 digits. His performance on other memory tests with digits equaled that of memory experts with lifelong training. With an appropriate mnemonic system, there is seemingly no limit to memory performance with practice.
With only a few hundred hours of practice, S.F. would be classified as a beginner at most skills. However, in his field of expertise, memory for random digits, he compares favorably with the best-known mnemonists, such as Luria's S. and Hunt and Loves V.P, (2). For example, after about 6 months of practice, we set SF. the task of recalling a matrix of 50 digits because data on this task are available for both S. and Hunt and Love's V.P.. S.F's study times and recall times were at least as good as those of the lifetime memory experts.

Wikipedia: Holonomic brain theory

The holonomic brain theory, developed by neuroscientist Karl Pribram initially in collaboration with physicist David Bohm, is a model of human cognition that describes the brain as a holographic storage network.  
Pribram suggests these processes involve electric oscillations in the brain's fine-fibered dendritic webs, which are different than the more commonly known action potentials involving axons and synapses. These oscillations are waves and create wave interference patterns in which memory is encoded naturally, in a way that can be described with Fourier Transformation equations.  
Gabor, Pribram and others noted the similarities between these brain processes and the storage of information in a hologram, which also uses Fourier Transformations. 
In a hologram, any part of the hologram with sufficient size contains the whole of the stored information. In this theory, a piece of a long-term memory is similarly distributed over a dendritic arbor so that each part of the dendritic network contains all the information stored over the entire network. 
This model allows for important aspects of human consciousness, including the fast associative memory that allows for connections between different pieces of stored information and the non-locality of memory storage (a specific memory is not stored in a specific location, i.e. a certain neuron). [...]
There is evidence for the existence of other kinds of synapses, including serial synapses and those between dendrites and soma and between different dendrites. 
Many synaptic locations are functionally bipolar, meaning they can both send and receive impulses from each neuron, distributing input and output over the entire group of dendrites. 
Processes in this dendritic arbor, the network of teledendrons and dendrites, occur due to the oscillations of polarizations in the membrane of the fine-fibered dendrites, not due to the propagated nerve impulses associated with action potentials. 
Pribram posits that the length of the delay of an input signal in the dendritic arbor before it travels down the axon is related to mental awareness. 
The shorter the delay the more unconscious the action, while a longer delay indicates a longer period of awareness. 
A study by David Alkon showed that after unconscious Pavlovian conditioning there was a proportionally greater reduction in the volume of the dendritic arbor, akin to synaptic elimination when experience increases the automaticity of an action. 
Pribram and others theorize that, while unconscious behavior is mediated by impulses through nerve circuits, conscious behavior arises from microprocesses in the dendritic arbor. 
At the same time, the dendritic network is extremely complex, able to receive 100,000 to 200,000 inputs in a single tree, due to the large amount of branching and the many dendritic spines protruding from the branches. 
Furthermore, synaptic hyperpolarization and depolarization remains somewhat isolated due to the resistance from the narrow dendritic spine stalk, allowing a polarization to spread without much interruption to the other spines. This spread is further aided intracellularly by the microtubules and extracellularly by glial cells. These polarizations act as waves in the synaptodendritic network, and the existence of multiple waves at once gives rise to interference patterns.

Capacity limits of information processing in the brain by Rene Marois and Jason Ivanoff - (2005) Trends in Cognitive Sciences 9, 296–305

Despite the impressive complexity and processing power of the human brain, it is severely capacity limited. Behavioral research has highlighted three major bottlenecks of information processing that can cripple our ability to consciously perceive, hold in mind, and act upon the visual world, illustrated by the attentional blink (AB), visual short-term memory (VSTM), and psychological refractory period (PRP) phenomena, respectively. 
A review of the neurobiological literature suggests that the capacity limit of VSTM storage is primarily localized to the posterior parietal and occipital cortex, whereas the AB and PRP are associated with partly overlapping fronto-parietal networks. The convergence
of these two networks in the lateral frontal cortex points to this brain region as a putative neural locus of a common processing bottleneck for perception and action.
The human brain is heralded for its staggering complexity and processing capacity: its hundred billion neurons and several hundred trillion synaptic connections can process and exchange prodigious amounts of information over a distributed neural network in the matter of milliseconds. Such massive parallel processing capacity permits our visual system to successfully decode complex images in 100 ms, and our brain to store upwards of 109 bits of information over our lifetime, more than 50 000 times the text contained in the US Library of Congress. 
Yet, for all our neurocomputational sophistication and processing power, we can barely attend to more than one object at a time, and we can hardly perform two tasks at once. 
A rich history of cognitive research has highlighted three major processing limitations during the flow of information from sensation to action, each exemplified by a specific experimental paradigm. 
The first limitation concerns the time it takes to consciously identify and consolidate a visual stimulus in visual short-term memory (VSTM), as revealed by the attentional blink paradigm. 
This process can take more than half a second before it is free to identify a second stimulus. 
A second, severely limited capacity is the restricted number of stimuli that can be held in VSTM, as exemplified by the change detection paradigm. 
Finally, a third bottleneck arises when one must choose an appropriate response to each stimulus. 
Selecting an appropriate response for one stimulus delays by several hundred milliseconds the ability to select a response for a second stimulus (the ‘psychological refractory period’). 
To be sure, these are not the only processes exhibiting capacity limitations. Indeed, it can be safely argued that all processing stages are capacity limited. However, these three bottlenecks are arguably the most severe ones that can impair our ability to be aware of, hold in mind, and act upon visual information. 
A recent flurry of neuroimaging studies, together with earlier brain lesion and electrophysiological work, have begun to unravel the neural underpinnings of these bottlenecks, and several recent behavioral studies have made great strides in isolating the underlying cognitive processes.  
The purpose of this article is to review our current understanding of the neurobiology of these bottlenecks of human information processing in the context of their extant cognitive models

Limits on the memory storage capacity of bounded synapses - Stefano Fusi & L F Abbott - Center for Neurobiology and Behavior, Kolb Research Annex, Columbia University College of Physicians and Surgeons

Our results indicate that good memory performance requires multistate synapses, but that the multiple states should not differ simply in their synaptic efficacy. We have suggested elsewhere that longer-term memory storage is possible using synapses the combing plasticity with metaplasticity in a cascade of states . The experimental implication of our results is that connecting synaptic plasticity to memory requires more than simply accumulating evidence about long-lasting modifications of synaptic efficacy. Rather, we must map out the full synaptic state space and focus on transitions not merely between states with different strengths but, more importantly, between states that are subject to different degrees and forms of plasticity.

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