Brain Hammer

Gray bananas look more yellow than equally gray non-bananas. Your conceptual categorization of a stimulus as a banana has something to do with the perceptual appearance of the stimulus. But what more can be said about this “having something to do with” stuff? More later.

Fig. 1. These bananas are bluer than they seem.

We asked human observers to adjust the color of natural fruit objects until they appeared achromatic. The objects were generally perceived to be gray when their color was shifted away from the observers’ gray point in a direction opposite to the typical color of the fruit. These results show that color sensations are not determined by the incoming sensory data alone, but are significantly modulated by high-level visual memory.

I saw Gegenfurtner demonstrate some of this in a talk he gave at the Pasadena Neurophilosophy conference in June ‘05. Gray bananas did indeed look more yellow than their equally gray non-banana counterparts.

So, what’s going on here? One hypothesis, call it the “phenomenal hypothesis” is that the activation of “high-level visual memory” influences, but is in no way constitutive of, the appearance. Another, call it the “conceptual hypothesis” is that the activation of high-level visual memory partially constitutes the appearance. I favor the latter hypothesis. Why? More later. Which do you favor? Why?
Reference: Hansen, T., Olkkonen, M., Walter, S. & Gegenfurtner, K.R. (2006). Memory modulates colour appearance. Nature Neuroscience, DOI:10.1038/nn1794.

I was interviewed for a column appearing in today’s Wall Street Journal on an intriguing case of possible conscious states in a vegetative patient (“There May Be More To a Vegetative State Than Science Thought” by Sharon Begley).

In the case in question, scientists recorded brain activity in a vegetative patient in response to being asked to imagine playing tennis.

Remarkably, this made neurons fire in the premotor cortex, a region that hums with activity when you mentally practice sophisticated movement, from a jump shot to a backhand. Then they asked her to imagine walking through each room of her house. This time her parahippocampal gyrus, which generates spatial maps, became active, again just as in healthy volunteers.

I think that if the same activity also shows up in patients under general anesthesia, then that activity doesn’t suffice for consciousness. The proposal that people under general anesthetic are conscious after all is an intolerable skeptical hypothesis (do you really want to believe that people suffer their major surgeries?). Only a tiny bit of my point got into the article, though:

There also is the possibility that people in other mental states regarded as unconscious, such as patients under general anesthesia, may show similar brain activity, suggests philosopher Peter Mandik of William Paterson University, Wayne, N.J., who studies consciousness.

Lamme et al (1998) suggest that the responses elicited by stimuli in anesthetized animals constitute merely feed-forward activation of representations in perceptual networks and lack feed-back activations from representations higher in the processing hierarchy. I suggested (but it didn’t make it into the article) that a good case for consciousness in the vegetative patient could be made if the following was found in the vegetative but not anesthetized patients: reciprocal activity of higher-level representations (like abstract representations of tennis) and lower-level representations (like motor-representations in a body-centered reference frame) as in Mandik (2005).

(Cross-posted at Brains)

Update Sept. 12, 2006: On this elsewhere: @Mind Hacks; @Rebecca Skloot; @Milinda’s Questions.

References:
Begley, S. There May Be More To a Vegetative State Than Science Thought. Wall Street Journal September 8, 2006.

Lamme, V. A. F., et al. (1998). Feedforward, horizontal, and feedback processing in the visual cortex. Current Opinion in Neurobiology, 8, 529 – 535.

Mandik, P. (2005) Phenomenal Consciousness and the Allocentric-Egocentric Interface. In: R. Buccheri et al. (eds.); Endophysics, Time, Quantum and the Subjective. World Scientific Publishing Co.

There’s been some interesting discussion over at Dave Chalmers’ blog (Fragments of Consciousness) on the falsifiability or lack thereof of various theories of consciousness (in particular, Chalmers’ and Dennett’s). (See this, this, this, this, and this.) A paraphrase of the main question I’m interested in right now might go something like this:

What data, either first-person accessible or third-person-accessible, are predicted by your theory that could conceivably/possibly fail to obtain?

Since that wasn’t exactly the question put to Chalmers, it wouldn’t be exactly correct to say that he answered that there are none. I think, however, that’s something like the spirit of his responses, but don’t take my word for it, follow the links above and judge for yourself.

Re: data and consciousness, Eric Schwitzgebel has no shortage of interesting things to say about introspection over at his blog (The Splintered Mind). See, for example, his recent post on afterimages and weigh in on the question of whether conscious experience always involves afterimages (and how you would know).

Re: afterimages and falsifiability again, one pretty sweet thing about various versions of psychoneural identity theory is that they do predict falsifiable data about consciousness. And not just third-person accessible data. Paul Churchland makes an excellent case for one such account in his recent “Chimerical Colors: Some Novel Predictions from Cognitive Neuroscience” in which very odd color experiences are predicted by a neural model of chromatic information processing. In brief, the differential fatiguing and recovery of opponent processing cells gives rise to afterimages with subjective hues and saturations that would never be seen on the surfaces of reflective objects. Such “chimerical colors” include shades of yellow exactly as dark as pitch-black and “hyperbolic orange, an orange that is more ‘ostentatiously orange’ than any (non-self-luminous) orange you have ever seen, or ever will see, as the objective color of a physical object” (p. 328). Such odd experiences are predicted by a model that identifies color experiences with states of neural activation in a chromatic processing network. Of course, it’s always open to the dualist to make an ad hoc  addition of such experiences to their theory, but no dualistic theory ever predicted them. Further, the sorts of considerations typically relied on to support dualism—appeals to intuitive plausibility and a priori possibility—would have, you’d expect, ruled them out. (Seriously, a yellow as dark as black? Whodathunkit?)

A video of Churchland lecturing on the topic is available here.

In other news, unless there are massive blackouts (or chimerically dark yellow-outs) in New York, NC/DC (the Neural Correlates of David Chalmers) is playing tonight. And if there are massive blackouts in New York tonight, don’t blame us.

Reference:
Churchland, Paul. 2005. “Chimerical Colors: Some Novel Predictions from Cognitive Neuroscience.” In: Brook, Andrew and Akins, Kathleen (eds.) Cognition and the Brain: The Philosophy and Neuroscience Movement. Cambridge: Cambridge University Press.

See also: The Phenomenal Consciousness of Inexistent Colors, Paul Churchland book,  Cognition  and the Brain

Brain

Originally uploaded by Isaac Mao.

While Googling myself the other day I found that my paper Fine-grained supervenience, cognitive neuroscience, and the future of functionalism was referenced in the Wikipedia entry on functionalism, which is nice. Also nice is that the paper’s central argument (that functionalism entails mental-mental supervenience, which violates physicalism) is discussed at some length. However, that argument is presented as a major player in the formulation of certain versions of functionalism, which, though flattering, can only be possible if time-travel is actual.

Anyway, here’s an excerpt from my paper:

[A]ccording to the bullet-biting functionalist, Searle’s rote rule following does give rise to genuine Chinese-understanding even though Searle himself seems not to understand Chinese. Likewise, the functionalist claims, Block’s nation’s walkie-talkie facilitated activities instantiate a mental event over and above the mental events of the individual citizens.

Such functionalist responses constitute an advocacy of mental-mental supervenience, which is to say that they allow for the possibility of a situation in which one mind or set of mental facts supervenes on another.

[…]

The possibility of mental-mental supervenience, however, poses a serious threat to theorists subscribing to the conjunction of the supervenience thesis and functionalism, because the possibility of mental-mental supervenience leads to a reductio ad absurdum of that conjunction. The key to the reductio is the fact that the possibility of mental-mental supervenience contradicts the supervenience thesis. Briefly, the supervenience thesis states that no mental differences can obtain without physical differences obtaining, but the possibility of mental-mental supervenience is the possibility of mental differences obtaining without physical differences obtaining.

Online demo of The McColloguh effect.
Stare at the black and white grid, then the colored grids, then the black and white grid again…

[G]aze at the two colored grids for a few of minutes. There’s no need to stare at a single point on a grid.

If you look at the black-and-white grid again, you should notice a green haze around the horizontal lines, and a magenta haze around the vertical lines. The intensity of this effect varies between individuals. If you don’t see this, go gaze at the colored grids for a while longer.

[…]

It is called the McCollough Effect, and was originally described by Celeste McCollough in a paper in Science in 1965. It has been the focus of on-going investigation ever since.

The effect typically lasts for hours, or even overnight. The duration can be changed by the consumption of coffee and other psychoactive drugs. One paper found that it is stronger in extroverts than introverts, and might be a reliable test for extroversion.

The precise cause of the effect is unknown, and currently under investigation. It is not a simple case of fatigued neurons: there are neurotransmitters involved and appear to be responsible for the long-lasting nature of the effect. It probably takes place in the V1 processing stage of visual information. This is the first image processing after the signal leaves the retina in the eye. The edge detection circuits somehow become associated with the color. At this stage the processing is monocular: the images from the two eyes have not been combined.

Decreased frontal-lobe efficiency is associated with negative thinking and depression. Which way, I wonder, do the arrows of causation point? Posted in Cog News:

“First, the people with late-onset depressive symptoms showed poorer performance on executive function tests than those with early onset depression.” “Executive decline” is a normal part of ageing linked to decreased efficiency in the brain’s frontal lobes. Typical signs of executive decline include disinhibition, rigid thinking, inattention and a decline in working memory.

“Second, we saw that executive decline was associated with rumination — a tendency for repeated negative thinking patterns — among those with late-onset depression,” says von Hippel, who is associate professor of psychology at the University of New South Wales. “We saw no such link among those who had early-onset depression.”

“Third, the link between executive decline and late onset depression was brought about by their joint association with rumination. That is, executive decline was only associated with late-onset depression to the degree that it led people to ruminate. When executive dysfunction did not lead to rumination, it did not predict late-onset depression.

“Clinical rumination is like problem-solving gone awry — it’s a wrong turn,” says Dr von Hippel. “Looking inward and being reflective is a useful thing to do, especially when negative events happen in our life. But if we get stuck in a pattern of saying ‘why me?’ there’s a risk that we can spiral into a pathology. Instead of solving the problem we just stew in it.”

Link.

Irving Biederman will get you high. With knowledge.

‘Thirst for knowledge’ may be opium craving

The “click” of comprehension triggers a biochemical cascade that rewards the brain with a shot of natural opium-like substances, said Irving Biederman of the University of Southern California. He presents his theory in an invited article in the latest issue of American Scientist.

“While you’re trying to understand a difficult theorem, it’s not fun,” said Biederman, professor of neuroscience in the USC College of Letters, Arts and Sciences.

“But once you get it, you just feel fabulous.”

The brain’s craving for a fix motivates humans to maximize the rate at which they absorb knowledge, he said.

“I think we’re exquisitely tuned to this as if we’re junkies, second by second.”

Biederman hypothesized that knowledge addiction has strong evolutionary value because mate selection correlates closely with perceived intelligence.

Only more pressing material needs, such as hunger, can suspend the quest for knowledge, he added.

The same mechanism is involved in the aesthetic experience, Biederman said, providing a neurological explanation for the pleasure we derive from art.

“This account may provide a plausible and very simple mechanism for aesthetic and perceptual and cognitive curiosity.”

Biederman’s theory was inspired by a widely ignored 25-year-old finding that mu-opioid receptors – binding sites for natural opiates – increase in density along the ventral visual pathway, a part of the brain involved in image recognition and processing.

The receptors are tightly packed in the areas of the pathway linked to comprehension and interpretation of images, but sparse in areas where visual stimuli first hit the cortex.

Biederman’s theory holds that the greater the neural activity in the areas rich in opioid receptors, the greater the pleasure.

Two neuroblogs have just announced calls for submissions for upcoming carnivals: Encephalon and the Synapse.

Re: Encephalon:

The first aim of Encephalon is to get contributions from as many neuroscience bloggers as possible, so I’d like the list of neuroscience blogs on the right to get shorter, and the list of contributors to get longer. The overall aim of the carnival is to find high quality writing about neuroscience, and to provide a resource of neuroscience blogs.

The first edition of Encephalon will be posted on the neurophilosopher’s blog on 3rd July, 2006.

Re: The Synapse:

I — and many of the other neuroscience-related bloggers on this site — sense a strong need for a neuroscience carnival — a way to regularly collect all of our valuable posts in a predigested form. So I am asking you to submit your best neuroscience posts over the next two weeks to me for the first “The Synapse” (a neuroscience carnival) to be published on June 25th.

brain

Originally uploaded by jimmythesuperstar.

Scientific American Mind article on games alleged to promote brain health.

Excerpt:

On the third day Kawashima surprised me. “Draw a giraffe,” he ordered. Then: “Africa.” Next, to humiliate me, he showed me a real giraffe and a real map of Africa. “Drawing objects from memory activates your prefrontal cortex!” As my scores improved, I was able to unlock new and more interesting games. Brain Age also allows multiple users; my fiancée insisted on playing, and we competed. She is a veterinarian and draws a mean giraffe. But her soft voice gave the controller trouble and slowed her on the Stroop test. “My brain age is 70!” she wailed. Unfortunately for my flagging sense of pride, that did not last long. She soon scored “younger” than I, and the brain age arms race was on.

After a week of exercises such as Low to High, Calculations×100, and Head Count, were my synapses any slicker? It is hard to say, when there is no external yardstick against which to measure progress. But one week into brain training, while taking a phone message, I found I could effortlessly hold one 10-digit number in my head and scribble down another. Maybe Kawashima is onto something

Here’s my stuff from this year’s excellent meeting of the Society for Philosophy and Psychology at Washington University in St. Louis:

Can neural realizations be neither holistic nor localized? Commentary on Anderson’s redeployment hypothesis

and

Neural Representation, Embodied and Evolved

the abstract of the latter being this:

What could representational content be such that appeal to it can be explanatory? I tackle such questions by addressing how representations that explain intelligent behavior might be acquired through processes of Darwinian evolution. I present the results of computer simulations of evolved neural network controllers and discuss the similarity of the simulations to real world examples of neural network control of animal behavior. I argue that focusing on the simplest cases of evolved intelligent behavior, in both simulated and real organisms, reveals that evolved representations must carry information about the creatures’ environments and further can do so only if their neural states are appropriately isomorphic to environmental states. Further, these informational and isomorphism relations are what are tracked by content attributions in folk-psychological and cognitive scientific explanations of these intelligent behaviors.