Do cognitive phenomena arise solely in primate brains?

One of the fundamental aims of neuroscience is to understand how processes in our brain give rise to various cognitive phenomena, such as perception, attention, emotion, learning, and the like. In their quest for uncovering these brain processes, neuroscientists employ a variety of model organisms: from the humble sea slug (Aplysia) to the more complex vertebrate species (fish and frogs), and at the highest-level, non-human primates (monkeys) and humans.

In his presidential special lecture delivered to the Society for Neuroscience (Nov.15, 2010), Prof. Robert Wurtz underscored the importance of non-human primates (monkeys) in cognitive neuroscience research. Monkeys can be trained on a variety of complex behaviors, and exhibit brain structures that are remarkably homologous to the human brain. Monkeys, thus, provide an unparalleled opportunity for invasive experiments of primate brain function. While acknowledging that the choice of model organism should be driven by the research question, Prof. Wurtz argued for the special status of monkeys as the model of choice for understanding the neural basis of cognitive phenomena, such as attention.

While appealing, Prof.Wurtz's argument begs the question: are such cognitive phenomena unique to primates? Take attention, for instance. Attention control in primates is known to be of two kinds: “goal-directed” and “stimulus-driven”. During the performance of a demanding task, we engage our attention on task-relevant stimuli in a “goal-directed” fashion. For instance, when driving to a friend’s place in an unfamiliar neighborhood, our attention is closely engaged in tracking street signs and other relevant landmarks, while ignoring irrelevant details of the landscape. On the other hand, unexpected and highly salient stimuli automatically draw (capture) our attention (“stimulus-driven”). For instance, a sudden, loud siren immediately draws our attention to the approaching fire truck, so we can get out of its way quickly, if need be.

How certain are we that similar kinds of attention control do not operate in the brains of other classes of (non-primate) animals? How about insects? Bees, for example, forage for nectar-bearing flowers matching a specific sensory template while carefully avoiding physically similar, but irrelevant objects. On the other hand, a sudden bright light, or a loud noise startles bees and quickly draws their (collective) attention to the source of the disturbance, as many a gardener who has accidentally disturbed a beehive could painfully attest. Hence, it is difficult to assert that similar forms of “goal-directed” and “stimulus-driven” attention control do not operate in the primitive insect brain.

Do insects share other “cognitive” phenomena besides “attention”? How about “motivation”? Symbolic communication? Learning? Memory? Perception? Where can we draw the line in the animal kingdom in terms of these phenomena? And where does this leave us with regard to the original question: Are monkeys indeed the ideal model for understanding the neural bases of cognitive phenomena?

Prof. Bob Wurtz’s argument is perhaps most relevant to cognitive neuroscientists who wish to understand the mechanistic basis of cognitive phenomena in the human brain. Indeed, such knowledge is fundamental to diagnose and treat cognitive disorders (such as schizophrenia, and autism) that afflict the human brain, and for which no cures are currently available. However, from a basic science perspective, Prof. Wurtz’s proposal leaves little room for understanding the emergent principles of brain circuits and their computations that give rise to cognitive phenomena, such as attention.

An analogy, might help illustrate this distinction. I have had the unique experience of trying to figure out the rules of American football by watching two professional teams compete. While I broadly understood that each team’s objective was to get the ball across the opponents’ line at the other end of the field, the gameplay proceeded so quickly, and with such intricately complex maneuvers, that I completely failed to decipher the essential rules: the rules of passing, the concept of a “first-down” and the like. The fact that the players on the field appeared to transform, without warning, into a completely different set of individuals did not help either. Perhaps, it would have been easier for me to figure out these essential rules, had I observed the simpler gameplay of middle schoolers less encumbered by advanced, and complex strategies.

A basic goal of cognitive neuroscience is to understand core principles by which cognitive phenomena arise in the intricate wetware of the brain. Prematurely restricting study of the neural basis of cognition to specific animal models raises the potential risk of “overfitting”, of failing to unravel fundamental principles of neural circuit operation that give rise to such phenomena.

This post is reproduced (with minor modifications) from my previous article in the Stanford Neuroblog (The official blog on Cognition and Behavior for the Society for Neuroscience 2010 annual meeting in San Diego).

Tattva in Tarski's theorem

Recently, I learnt of Tarski's undefinability theorem (closely related to Godel's incompleteness theorem), which states that [1]:

Let L be the language of first-order arithmetic, and let N be the standard structure for L. Thus (L, N) is the "interpreted first-order language of arithmetic." Let T denote the set of L-sentences true in N, and T* the set of code numbers of the sentences in T. Then, there is no L-formula True(x) which defines T*. That is, there is no L-formula True(x) such that for every L-formula x, True(x) ↔ x is true.

Being no logician, I had to resort to the layman's version of the theorem, one of which is given below (adapted from [1]):

The theorem [shows that in] any sufficiently strong formal system, "truth" in the standard model of the system cannot be defined within the system.

So what does this have to do with Tattva? I am going to speculate on how this theorem can help understand a troubling intuition I call the "virtual reality" dilemma: Why do we (normal people) have no problem with believing that we exist (we can "truly" be conscious of ourselves), whereas we cannot be sure of other people's existences (deep down we can never be sure if other people really exist, or if the external world is part of a virtual reality simulation, inspiring movies like the Matrix)?

Let us ask what it means for Tarski's formal system to be "sufficiently strong"[1]?

The resulting theorem applies to any formal languages with negation, and with sufficient capability for self-reference...

So it requires: 1) Negation, 2) Self-reference. I propose the following two axioms for how it can explain the "virtual reality" dilemma.

i. My mind is capable of generating a logic system that has negation and self-reference as applied to entities other than myself. Since it has both of these properties, it can never define "truth" of those external entities within its language, and can consequently never "truly" believe in their existence.

ii. However (and here is the catch), my mind generates a second "I"-referential logic system which has self-reference, but no concept of negation, ie, my "I"-referential logic system can refer to me (itself), but cannot refer to my "absence" (negation).

In other words, while I ("I"-referential system) can believe the truth of the statement "This (self) is I", I cannot believe the truth of the statement "This (self) is not I". So, since my "I"-referential logic system does not have negation, Tarski's undefinability (of "truth" within the system) no longer holds.

Ergo, I can "truly" believe I exist without any confusion or conflict of intuition.

Perhaps all of this is just a restatement of Tarski's theorem. Anyhow, I felt it was interesting that the word Tattva (sometimes interpreted as "That-is-you") reads like a dual of the self-referential statetement "This-is-I". Maybe there are deeper waters here than I had anticipated.

Of course, I realize I have muddled into exotic territory leaving open several questions such as if formal language theory is applicable to the mind, and why the "I"-referential logic system has no concept of negation. But stupid as it may sound, I feel intuitively that some of the "virtual reality" dilemma can be resolved by positing two logic systems in the brain (one with and one without the concept of negation).

To cap all of this wild speculation with "science" I posit that these two logic systems could reside in the left and right brains. Oh wait.. or was it in the "frontal" and "parietal" cortices?

The Spiritual Brain: Selective Cortical Lesions Modulate Human Self-Transcendence

Ok, here's the grand unified spin: The logic system with the concept of no-negation resides in the frontal cortex that gives rise to a (non-conflicting) sense of "I". The logic system with the concept of negation resides in the parietal cortex, and gives rise to the (conflicting) sense of "other". With parietal damage, the frontal cortex takes over and you identify with everyone else, and transcend your (limiting) self.

References:

[1] http://en.wikipedia.org/wiki/Tarski's_undefinability_theorem

Concerning the Japanese automaker recall

While in no way connected with the purpose of this blog, I couldn't help but comment on the ongoing massive car recalls by Japanese carmakers.

I was recently going over why Toyota is recalling so many cars, and found the following report on stuck accelerator pedals and uncontrolled acceleration: Report here [1]

Toyota had 52 complaints (41%). Ford had 36 (28%). And the wording of complaints seem not very different to me.

While human life is precious, what surprises me is the scale of this recall: 2.3 million cars to address 52 complaints? The total number of vehicles recalled seems to have swollen to ~7.5 million (until yesterday), almost as many as Toyota sold in all of 2009!! [2]

Honda just yesterday recalled over half a million vehicles over some kind of "faulty switch" [3]

Also, these recalls apply pretty much only to American/European cars. I quote: "Toyota has said the defective pedal was not used in any of its cars in Japan, Australia and Asia excluding China...Toyota has not recalled any cars in Japan, where it uses different suppliers." [2]

The conspiracy theorist in me is beginning to wonder if this is a concerted attempt by vested interests in America/Japan (in cahoots with Toyota & Honda), to give American carmakers a fresh lease of life (by scaring people away from japanese cars, and into the open arms of American carmakers).

Interestingly, the financial situation for Japanese carmakers seems very different from that of their American counterparts -- apparently they are flush with cash reserves, but due to the credit freeze, have been unable to extend dollar credit to US consumers [4]. So overall, neither carmaker (Japanese/American) has been successful in continuing to sell vehicles in their biggest markets (US/Europe).

Maybe this recall effort will boost car sales for American carmakers by creating a temporary vacuum in the car market (left by Toyota and Honda), restore confidence in the industry (partly driven by misguided sentiments of patriotism), get dollar credit flowing in the automobile sector again, which will help kickstart slumping car sales overall (this is of course, a madeup scenario, and only one among several possibilities).

Of course, once the recall hubbub is over, the Japanese automakers will bounce back with more dollar reserves (from any shadow investments in GM) and a spanking clean image (and perhaps a spanking new hybrid model or two) of having done the "right" thing, despite undergoing "huge expenses". The consumers will be left with no clue of what happened behind the scenes.

Given that public memory has a very limited span these days, the scenario doesn't sound implausible at all to me. In fact, this almost reminds me of Bill Gates bailing out Apple back in 1997...hmm...

What makes humans special...

I have read several accounts where, within the animal kingdom, humans are said to be privileged possessors of "consciousness" or "self-awareness". While it is assumed that all other "lower" animals operate almost like machines, humans have this special, almost miraculous, self-introspective power. Humans can "look within", be aware of their mental and bodily states, and establish a unique sense of self-identity -- thanks to their exceedingly complex brains.

I am not so sure. All animals with comparable brain complexity should have a comparable sense of self-awareness and self-identity (as evidenced by dophins, apes and even magpies passing mirror tests for "self" identification). The way I see it, humans are perhaps special in their ability to extrapolate their consciousness universally. To be able to feel that their identity is not tied to their body, their selves. To be able to experience a "self" that, by definition, is not an entity that limits, but one that liberates.

In this context, the last part of a video (pointed to me by a friend) is relevant [1,2]:
http://www.ted.com/talks/vs_ramachandran_the_neurons_that_shaped_civilization.html

Notes:
[1] I have not been able to verify the scientific claim on inducing touch sensation on anesthetized arms by touching another person ("dissolving barriers between humans"). The closest I could get was this article: Sathian. Intermanual referral of sensation to anesthetic hands. Neurology 2000;54:1866-1868 (which is not about inducing touch across people, just across arms of the same person).

[2] A related question is if visual input is needed for the touch sensation to be "perceived". If so, one is still left with the question of how "mirror" neurons could truly help "dissolve barriers" (or link consciousnesses) without sensory input.

South India's ancestry: Japanese and Tamil

Several divides separate southern from northern India. The Dravidian languages of south India are postulated to be a distinct class from the north Indian Indo-Aryan family. The Hindu religion practiced by Dravidian cultures also has distinct elements and practices. According to an established model, the Dravidians were supposed to have arrived in the Indian subcontinent c. 5000 years ago) before the arrival of Vedic Indo-Aryans (c. 3500 years ago) [1].

But this picture is being challenged by a recent genetic study [2] that claims that almost all of India is an admixture of two main ancestral populations: the ancestral north Indians (ANI), and ancestral south Indians (ASI), both of whom arrived in South Asia between 750 and 2500 years ago, well after the arrival of the Indo-Europeans [3]!

Where did these ancestral populations originate? Apparently, the ANI share some genetic structure with middle Easterners and Europeans, whereas the ASI seem to be unrelated to other mainland groups (the only East Asian population considered being Chinese). Thus, south India's ancestry: the ASI (as per the new theory), or the Dravidians (as per the old) remains a mystery.

While it is clear that many questions remain to be answered, in my personal investigations, I have found remarkable similarities between the south Indian and Japanese languages and cultural practices. I have moved most of the details on this (ongoing) investigation to a separate page:

http://japanese-dravidian.blogspot.com

The origin of the Japanese people, language and culture is itself a hotly researched area. Interestingly, the Yayoi people in Japan (who integrated with the native Jomons), brought rice paddy cultivation with them into Japan about 2500 years ago. Is the similar date for the arrival of ancestral South Indians into south Asia a coincidence? Tune in to the above page for updates.

[1] DNA_points_to_Indias__two-pronged_ancestry
[2] Reich, D., Thangaraj, K., Patterson, N., Price, A. L. & Singh, L. Nature 461, 489–494 (2009). | Article
[3] Chakravarthi A. Human Genetics: Tracing India's invisible threads. Nature 461, 487-488 (2009). | Article

Description

This blog is an ambitious attempt to inquire if ancient Indian spiritual concepts go beyond systems of mere belief, and have a basis in empirical science. My interests extend to other aspects of ancient India, including its (pre)history, languages and culture. The title of the blog represents my search for the (essential) truth about concepts in, and the origins of, Indian religion, philosophy, and culture.

The title's background photograph was taken at Point Reyes, CA. It symbolizes the spirit of this blog: the confluence of spiritualism (heaven) and materialism (earth).

There are no answers here, only questions. With salutations to the spirit that moves man to question.