Sam's blog

Day 035 - Visual prostheses

Submitted by Sam on 24 June, 2011 - 23:48

Problems with the eye or the optic nerve are the leading causes of new blindness. In such cases, the visual cortex (the part of the brain responsible for processing the visual information) often remains largely intact, presenting the possibility of recovering some level of sight through the integration of an intracortical visual prosthesis.

There has been historical motivation for attempting to restore sight through electrical stimulation of the brain from at least 1918, when two German doctors reported that during an operation to remove bone fragments from a patient's head caused by a bullet wound, the patient described flickering in the right visual field when the left occipital lobe was electrically stimulated.

Using the same principles as those realized by the rat hippocampal prosthesis recently developed by Dr Berger, intracortical visual prostheses are being developed which could conceivably restore vision by simulating the pattern of neural activity usually associated with the sense-data provided by the eyes to provide the visual cortex with meaningful sensory input which it no longer receives.

The basic concept for the prosthesis involves implanting electrodes into the visual cortex, which would be connected to an implanted computer chip powered and controlled wirelessly. A camera would feed images to a computer system, which would encode images and transfer them to the cortex digitally, with each 'point' in the image represented by an electrical stimulation in the implanted electrode. These stimulations would create points of perceptual white light (phosphenes) in the appropriate place.

Whilst this bitmap approach to artificial sight is both promising and intuitive, it needs substantial alteration and improvement in order to be able to generate clear, highly-resolved colour imagery, as it seems that the visual system does not actually work on a point-by-point basis. Rather than encoded as pixels, our visual cortex interprets images in terms of colours, edges, orientation etc. Finding how these dimensions of vision are encoded in the brain, and how they may be mapped by an artificial system are among the stated goals of Illinois Tech's IntraCortical Visual Prosthesis Project.

Day 034 - Neural prosthesis

Submitted by Sam on 23 June, 2011 - 22:02

In a paper published last week, biomedical engineers from the University of Southern California detailed how they were able to selectively turn rats' memories on and off using a computer chip. The team artificially constructed neuron-to-neuron connections between the rats' normal brain circuitry and a computer circuit designed to duplicate the neural activity associated with encoding memory, ultimately allowing the scientists to turn certain memories on and off with the flip of a switch. As the lead author of the paper puts it: "Flip the switch on, and the rats remember. Flip it off, and the rats forget” 1.

The prototype cortical prosthesis demonstrated by the team was applied to the information processing areas of two sub-regions of the rats' hippocampi, areas which have previously been identified as being involved in the formation of long-term memory. The researchers taught the rats a task which involved pressing leavers in order to release droplets of water as a reward. During the learning process, the team used electrical probes to record the activity of the hippocampus, which converts short-term memory into long-term memory. By blockading the neural interactions of the two areas, the researchers were able to make their trained rats forget their long-term learned behaviour.

The team then integrated their artificial hippocampal system, which had been programmed to duplicate the patterns of electrical activity associated with the interaction of the two areas of study. When activated, the chip delivered electrical pulses which conformed to the normal firing of hippocampal output region, thereby simulating the memory-encoding function and restoring long-term memory capability in the pharmacologically blockaded rats.

As well as recovering switched-off memories in compromised rats, the researchers were able to show how the device could actually strengthen the memory generation and capability of rats with a normally functioning hippocampus.

The success of the prosthesis in both restoring and enhancing memory makes it a logical candidate for development into a human-viable prosthesis, with the potential to help sufferers of neurodegenerative diseases such as Alzheimer's, or victims of stroke or brain-injury.

  • 1. "USC - Viterbi School of Engineering - Restoring Memory, Repairing Damaged Brains." USC - Viterbi School of Engineering. 17 June 2011. Web. 23 June 2011

Day 033 - Insights from brain damage

Submitted by Sam on 23 June, 2011 - 00:48

Studying the effects of localized brain damage can help refine and verify theories of mind. As Professor Rama explains in his TED Talk below, the brain's modular structure means that injuries to small parts of the brain lead to highly-selective loss of function, which throws light on to the structural-functional relationships of the brain.

The examples that Rama cites reinforce several key points that have been covered from different perspectives elsewhere in this blog:

  1. The brain is highly modular. It is a robust system that does not suffer a system-wide degradation in performance when a single element is comprised. This is evidenced by Rama's first example of Capgras syndrome, which occurs when damage is sustained to the facial recognition are of the brain, the fusiform gyrus. Sufferers of the syndrome are unable to recognize other people's faces, but remain able to recognize people using other characteristics, such as the sound of their voice.
  2. The mind makes its own subjective reality. The brain has the capacity to provide utterly compelling subjective transformations of objective reality, even when such experiences conflict with sensory evidence. This is shown by the second example, that of the phantom limb. Amputees with phantom limb syndrome continue to vividly feel the presence of their missing limb, despite knowing that the limb is no longer there.
  3. Phenomenal experience is encoded by the neural network. In his third example, Rama shows how abnormal cross-wiring of areas of the brain can lead to synaesthesia, the mingling of senses. People with this condition might see a number or musical tone as coloured, whilst remaining normal in all other respects. The fusiform gyrus contains regions which specialize in numbers and colours located adjacently, and if these get accidentally cross-wired (perhaps due to a mutation in the gene which controls the trimming of interconnected regions in the developing brain preventing it from working correctly), then numbers will become neurally linked to colours.

Day 032 - Words

Submitted by Sam on 21 June, 2011 - 15:43

The difficulty of verbally articulating a new experience arises because there are several degrees of separation between the objective reality which stimulates the experience and the way in which words are used to encode that experience. Using the example of describing the 'red' of a red tomato, the degrees can be delineated as follows:

  • The objective red is the physical, real-world 'red'. Objective red is the physical, non-internalizable process by which electromagnetic radiation is emitted from a physical object to produce the property we refer to as 'red'. This electromagnetic radiation constitutes the physical properties of real-world 'colour', not 'colour' as we know it, which does not exist in the physical world, but is instead constructed from our internal transformations of 'objective red'.
  • Neural red is the transformation of the sensory input that detects objective red into patterns of neural activity in the brain.
  • Phenomenal red is the integration of the 'raw' experience of neural red into conscious processes. It is perceived as the 'what-it-is-like' of seeing red, and it was Mary 'learned' when she left her monochromatic room and experienced colour for the first time.
  • The word 'red' - refers to the ineffable experience of the phenomenal, but does not describe it. Therefore the word 'red' refers to objective-red, the real-world red, only indirectly.

Whilst phenomenal red can be described wholly by a complete physiological map of the associated neuro-activity in the brain, the experience cannot be duplicated in other brains through verbal explanations, which are merely designators of the experience, not complete encodings of it. The only way to transfer experiences, therefore, is to recreate an exact neurophysiological replica of neural red in the brain of the recipient.

The reason language works is because we have species-wide homologous brain structures, with a certain degree of genetically determined uniformity in the structures which realize phenomenal experience. This suggests that the basic qualities of experience are similar in most humans, and so we can reliably use words as designators for an assumed common-endowment of similar qualitative experiences. However, there is currently no way to verify that two interlocutors are actually talking about the same phenomenal experience, so it is more useful to think of words as connoting the phenomenal rather than describing it.

Day 031 - Tracing our experience of the real world

Submitted by Sam on 21 June, 2011 - 00:57

We've seen that nothing in the external world is ever directly in contact with our minds, as all perception of objective reality is mediated through nerve signals, patterns of electrical charge derived from sensory receptors. This electrical stimulation has to be interpreted by the neural network in order to derive meaning and create a relationship between the encoded signal and objective reality. When we 'see' a red tomato, for instance, we only actually see a construct of a red tomato, a mental impression generated from filtered sense-data. The translation of sensory-data into conscious processes creates 'the first obligatory step in the epistemic chain' 1 ; the basic building-block of conscious recognition and relationship with the outside world, serving as non-verbal thinking elements.

If the epistemic chain starts with the interpretation of sense-data into experiences (such as the electromagnetic waves emitted from a red tomato being transformed into the experience of seeing a 'red' tomato), an entirely non-verbal process, then it ends with the association of phenomenal experience with language, where names are given to experiences, and propositional knowledge becomes possible.

Without language, it can be seen that certain basic, primal experiences can contain meaning, as they have a capacity to refer. The feeling of hunger rapidly becomes associated with eating, and so the experience of hunger comes to refer to the need to eat, as the 'what-it-is-like' of hunger, gains the 'what-it-is-about' of eating, entirely without language. This is the most basic form of reference available to conscious organisms, allowing phenomenal experience (the experience of hunger, thirst or pain, for example) to effect behaviour (eating, drinking, moving etc.). In humans, this basic form of phenomenal reference has become linked to a verbal lexicon, where words become anchored by their related phenomenal experience(s) to create the final link in the epistemic chain.

  • 1. Musacchio, J. "The Ineffability of Qualia and the Word-anchoring Problem." Language Sciences 27.4 (2005): 403-35. Print.

Day 030 - Thought experiments

Submitted by Sam on 19 June, 2011 - 23:04

Like metaphors, thought experiments can be used as tools to compress complex ideas into tractable, workable concepts described in everyday language. Like metaphors, thought experiments have a very broad applicability, and can very usefully impart insight through analogy and extrapolation. However, just as metaphors forgo the tightly-controlled precision of technical language in favour of generalistic insight, so thought experiments leave behind the rigour and empiricism of traditional scientific experimentation in order to tackle phenomena that are difficult or impossible to test in the real-world. With their almost unavoidable appeals to common sense and intuition, thought experiments can contain a distressing degree of unscientific latitude, which can result in the propagation of the kind of misleading conclusions that Jackson drew from the Mary's room thought experiment.

As the Mary's room thought experiment was originally proposed by a philosopher it suffered from its inception by being conducted in a 'laboratory' (to risk extending the metaphor) lacking in neuroscientific expertise, and burdened by a heavy philosophical bias. However, by merit of the experiment's eminent repeatability (transferability and repeatability being the whole point of thought experiments), it was rapidly re-run in many other minds, and analyzed from perspectives with varying areas of expertise and predispositions. Through this organic review process, experimenters equipped to resist 'intuitive' answers to its implications, like Dennett, were able to successfully counter its non-physicalist implications and make a strong case for the use of empirical science as the primary mode of research and discovery rather than models like thought experiments which are easily affected by fallible subjunctive reasoning and knowledge-gaps.

Day 029 - Who senses the sensors?

Submitted by Sam on 19 June, 2011 - 00:57

The brain's inability to accurately report on its own hardware is a further reason why intuitions about the non-physicality of phenomenological experience should not be considered authoritative. This inability arises because the structure of the brain has evolved to avoid the costly regress of sensors sensing sensors (or neurons reporting on neurons ad infinitum) in order to be biologically efficient. By avoiding biologically irrelevant complexity to maximize the efficiency of the cognitive system, the machinery of the brain is transparent to the 'self' it generates, thereby preventing clear introspective perception and analysis of its inner workings. From a first-person perspective therefore, accurate analysis (or indeed, awareness) of the physical mechanisms which generate one's own consciousness is ultimately impossible without some form of third-person aid.

As the first-person perspective cannot perceive the physicality of the brain which produces the mind, there is a common propensity towards anti-physicalist intuitions, an illusion which José Musacchio has described as “a serious philosophical handicap1.

In order to understand qualia, therefore, it is necessary to recognize that the nature of mind cannot be accurately explored through introspection alone, as the system which enables this introspection is critically limited in its ability to analyze its own relation to reality. This is not only because of the lack of 'hardware' monitors, but because objective reality is never actually directly available to a consciousness, as all senses which feed it are filtered, trimmed and processed, so that nothing can be perceived directly in some kind of 'raw' state. As we have seen, this filtering is a result of “cognitive shortcuts” which funnel all perceptual information into easily understandable packets, evolutionarily optimized to deal with predators and prey very rapidly, but as a side-effect falsifying reality. Proof of both the success and the fallibility of this system can be found in our ability to accurately perceive physical shapes in the space around us, but yet fall victim to optical illusions which 'trick' the brain into visualizing something which does not exist in objective reality.

  • 1. Musacchio, José M. "Why Do Qualia and the Mind Seem Nonphysical?" Synthese 147.3 (2005): 425-60. Print.

Day 028 - The language of qualia

Submitted by Sam on 17 June, 2011 - 23:52

The physicalists' deconstruction of Jackson's 'knowledge argument', of which Dennett's argument 1 is perhaps the most powerful, has proven so convincing that in 1998 Jackson himself publicly reversed his position in regards to the non-physicality of qualia, rejecting his original knowledge argument as false and accepting that the sensory side of psychology is, in principle, deducible from the physical world 2. In the same article, Jackson re-aligns the question of Mary's room to ask why our intuition that she learns something when she leaves the room is so strong, proposing one possible explanation.

Part of the reason our (or more accusingly, Jackson's) intuition about Mary was wrong can be identified in Dennett's thirteenth 'intuition pump' in Quining Qualia, where the ineffable properties of qualia are challenged based on the practicality of expressing their defining characteristics. Dennett argues that qualia are not substantively ineffable, but are instead only impossible to accurately describe in a practical sense, as language (or indeed any other form of extant communication) can only ever convey an incomplete likeness of the experience in question. The example Dennett uses is the experience of hearing the sound of an osprey cry for real contrasted with reading a description of what to listen for in a bird book, which falls far short of capturing and conveying the experience's 'qualia-complex'.

The intuition that Mary would learn something new seems to arise from an inability to comprehend the true scope of what a complete understanding of 'all the physical facts' about the perception of colour would entail. This misunderstanding is predicated on by the perhaps subconscious recognition that, as a mere human, Mary could never hope to actually possess and understand this level of detail, no matter how brilliant a scientist she happened to be. Subsequently the working definition of 'all of the physical facts' might mistakenly be scaled down into 'all those physical facts which could practically be held in Mary's mind', which would consist of facts that are essentially compact enough to be expressed by a manageable number of words. The sheer number of words necessary to completely specify 'all of the physical facts', to precisely delineate the exact states of every relevant sub-atomic particle and all of their near-infinite interactions, would clearly be too great for any human Mary to ever hold in her mind.

The problem with qualia and the knowledge argument seems to be bound to a problem with language. It may seem intuitive that Mary would learn something new when she sees colour for the first time, but only because we make a tacit assumption that her knowledge is fundamentally human, that is, built on language, resulting in a misleading recalibration of the meaning of her physically complete understanding of the perception colour. In fact, the hypothetical Mary is closer to being a mini Laplace's demon than a 'brilliant scientist', as she would have to possess a practically incomprehensible level of understanding of the physical universe, which would take a correspondingly staggering number of words to specify.

Qualia can't be shared because human language is unable to accurately compress the richness of experience into manageable chunks. Through projects like The Blue Brain Project, however, it seems plausible that qualia could be shared by removing the middle-man, by circumnavigating human language entirely and dealing directly with the fundamental electro-chemical 'language' of the brain itself.

  • 1. Dennett, Daniel C. "Quining Qualia." Consciousness in Modern Science (1988). Print.
  • 2. Jackson, Frank C. "Postscript on Qualia." Mind, Method and Conditionals (1998). Print.

Day 027 - A physicalist response to Mary the super-scientist

Submitted by Sam on 16 June, 2011 - 23:09

Japanese scientist Ken Mogi disagrees with the philosophers who identify an explanatory gap arising from the implications of the Mary's Room thought experiment, insisting that percepts can be fully represented by the interconnected firings of spatially disperse neurons, and therefore that all perception has a foundation in physical phenomenon. He keeps company with the philosopher and cognitive scientist Daniel Dennett when he claims that “the time has come, when qualia is to be liberated from the studies of philosophers, and to become a subject of an empirical science” 1.

Dennett made the argument that if Mary truly knew everything there is to know about colour, she would necessarily have to have an unimaginably precise atomic-level understanding of the neurology of the human brain, and would therefore be able to interpret the minute changes in the brain's electro-chemistry that each stimulus would produce, and thus would have a complete understanding of the stimulus' corresponding quale. Dennett asserts that the thought-experiment is misleading because whilst it requires 'all physical knowledge', such an omniscient state is unimaginable for a human to possess, and so twists our intuitions. If she really did possess all physical knowledge, she would be able to pre-determine the electro-chemical morphology of her brain when it is presented with a colour stimulus, and would therefore be able to accurately model her 'experience' of seeing colour for the first time.

In order to further elucidate this claim, Dennett uses the hypothetical example of 'RoboMary', an exceptionally intelligent robot who perceives the world through a monochromatic software filter. Other robots exist like RoboMary, but who are able to perceive the world with colour vision. RoboMary is able to create a simulation of the colour-vision of these robots (which is ultimately entirely determined by their software and circuitry), and is able to see exactly how their internal states are configured when they are presented with a coloured impulse. With reference to the internal states of the other robots, she is able to project exactly how she would react without a monochromatic filter when presented with colour. In doing so, she is able to know exactly what it is like to see the colour red, without actually ever having seen it in reality.

Day 026 - Mary's room

Submitted by Sam on 15 June, 2011 - 21:54

One of the most widely discussed philosophical thought-experiments about qualia was proposed by Frank Jackson in his 1982 article “Epiphenomenal Qualia”, and is known variously as 'Mary's room' and 'Mary the super-scientist'.

In this thought-experiment, Mary is a scientist who is confined to a monochromatic room, and has never been exposed to colour. She is a brilliant scientist, specializing in the neurophysiology of vision, and we are to suppose that she obtains all of the “physical information” that exists on what happens when colour is perceived; in short, she knows everything there is to know about colour, but she has never experienced it. Jackson asks what will happen to Mary if she is released from her black and white room and sees colour for the first time – will she learn anything or not?

If she does obtain new knowledge when she leaves the room, then the implications are that qualia exist, and that perfect physical knowledge is inadequate to describe all experience. This is what Jackson concluded in 1982:

“It seems just obvious that she will learn something about the world and our visual experience of it. But then it is inescapable that her previous knowledge was incomplete. But she had all the physical information. Ergo there is more to have than that, and Physicalism is false” 1.

Others have taken a similar view, concluding with Jackson that Mary would learn something new when she sees colour for the first time, and thus there must be an unbridgeable gap between the physical and the mental worlds, and that experiences and feelings must have subjective, non-physical qualities. This is known as the explanatory gap, and its strongest proponents (antimaterialists) argue that it can never be closed, and that the mind is substantially and qualitatively more than the sum of the brain's physical parts.

  • 1. Jackson, Frank (1982). "Epiphenomenal Qualia". Philosophical Quarterly (32): 127–136.
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