Thursday, June 24, 2010

Ardhanareeswar – The Bilateral Human Brain

Ardhanareeswar – The Bilateral Human Brain

The half-man half-woman Ardhanareeswar represents the union of Shiva and Shakti, the basic tenets of creation, the unchanging Consciousness and Drive that gives motility. The cosmic dance of Ardhanareeswar symbolizes the beginningless cycle of origination and dissolution of the world. Traditionally the feminine Shakti is shown to be the left half of the body and the right half is Shiva.

A story in Shiv Purana says that Brahma, the Creator, was not happy with the way the development of human beings was going on. So he prayed to Shiva. Shiva released his Shakti part and instructed her to be born as the daughter of Daksha, thus creating an active role for her in the world. The classical Indian picturization of Ardhanareeswar stops with the body and does not tell anything of the brain in the head.

We are now well aware that our brain consists of two distinct units (left and right hemispheres) interconnected by a bundle of 300 million axonal fibers. The right brain controls the left half of the body (including the left part of the face) and the left brain controls the right half of the body.

Characteristically the right hemisphere oversees a set of qualities which are typically associated with feminine traits and the left hemisphere oversees the masculine traits. The ancient Indians depicted correctly the left half of the human body to show Shakti (female quality) and the right half as Shiva (male)! This does clearly indicate their awareness of the human anatomy.

The work distribution between the left and right brains is broadly as given below:

Left Brain Functions:

1. Language Skills; 2. Numerical counting; 3. Reason/Logic; 4. Analytical and Scientific Skills and 5. Control of the right side of the body.

The left brain works like a serial processor, one task at a time in a sequential manner and is reductionist in approach, classifying things into clear yes/no boxes. It is truthful to the details. It is uncomfortable with uncertainty and looks for logical closure of issues.

Right Brain Functions:

1. Insight; 2. 3-D Visualisation; 3. Art/Music; 4. Imagination; and 5 Control of the left side of the body.

The right hemisphere specializes in reacting to emergencies, organizing items spatially, recognizing faces and processing emotions. It works more like a parallel processor, taking in many aspects at one time and giving a comprehensive holistic picture. It can live with esoteric and fuzzy ideas.

"The great pleasure and feeling in my right brain is more than my left brain can find the words to tell you", said the Nobel Laureate, Dr. Roger Sperry.

The divergent response in the way the right and left brains function is famously illustrated in the twitch in the smile of Bill Clinton when he was grilled on the Lewinsky affair. When he tried to cover up the truth in answering a question, the right side of the face (governed by the left brain) had half a smile on the lips (delivering calculated words) whereas the left side was twitching with uncontrolled gestures!

Left Brain and Right Brain Personalities:

All of us use both the brain hemispheres all the time. Still, we tend to be dominated by the characteristics of one or the other hemispheres.

In case the connectivity of the two hemispheres is ruptured (either because of an accident or surgically disconnected for pathological reasons), the behavioral response of the individual looks as though he is being instructed by two independent control centers in the brain. Scientists have been able to learn much about the way brain functions from these split brain studies.

Prof. R. Wiseman, Neuropsychologist and Magician, suggests easy and entertaining ways to discover whether you are left-brained or right-brained. One way is to clasp your hands casually and see whether right or left thumb is positioned on the top (see the picture). If the left thumb comes on top, you are right brained and artistic, adventurous and accommodative. If the right thumb is on the top, you are analytical, fluent with words and conservative.
You would hardly get a prize to guess which way Dr. Albert Einstein, the greatest of all Scientists, would clasp his hands!


Here is Rupert Spira, the Non-dual philosopher, clasping his hands and see which thumb is positioned on the top.

Where is “self”?

Dr. Jill Bolte Taylor, Neuroscientist and anatomist, describes in a fascinating detail how a blood vessel exploded in her left brain hemisphere in late 1996 and as a result how the left part of her brain completely deteriorated in its ability to process information. “On the morning of the hemorrhage I could not walk, talk, read, write or recall any of my life,” she said. With her right brain only functioning she felt, “I am an energy being connected to the energy all around me through the consciousness of my right hemisphere. We are energy beings connected to one another through the consciousness of our right hemispheres as one human family. And in this moment we are perfect. We are whole. And we are beautiful.”

The experience of Dr. Taylor gives the impression that our little self, the “me” (which gives me the feel of a 'separate' person) is located in the left part of the brain. That is not true. Subsequent research by others showed that the “self” could be on the right side. But actually it now looks that there is no identifiable “I”-spot in the brain representing a 'me'. The “self” is perhaps a gateway of a set of neuronal networks that act as a node at that point of time for “me” related information depending on which set of neuronal networks are called to action at that specific time.

The Advaitic teaching on the origination of “I”-consciousness matches well with the above neurological model. Brain constantly goes on sensing the environment. As long as just the sensations happen no harm is done. For example, “When you look at a glass in front of you on the desk, it sets off a lot of reactions in your brain. Part of your brain categorizes it: "That's a glass!" Another part of the brain thinks about the glass's shape and size, its exact location, and what you would have to do with your hand and arm if you were going to reach out and grab it. All that activity goes on even if you just look at the glass.”

But if a claim of “me or mine” is made on what is sensed (the sensed object need not be a physical thing; it can be a thought in mind, a bodily sensation, or a thing perceived out there), “I”-consciousness pops up. The particular neural network node cognizing and identifying the object with a ‘name and form’ will be then the “I” at that particular moment. Depending on the ‘object’ sensed, the neural network node may be shifting in the brain.

Evolutionary Origins of the Right and Left Brain:

There is an evolutionary reason for the origin of two brain hemispheres. I shall present here a few extracts from the paper of Prof. P.F. MacNeilage, Prof. L.J. Rogers and Prof. G. Vallortigara published in Scientific American in July 2009.

Peter F. MacNeilage is a professor of psychology at the University of Texas at Austin. He authored the Book The Origin of Speech published by Oxford University Press in 2008. Lesley J. Rogers is an emeritus professor of neuroscience and animal behavior at the University of New England in Australia. Giorgio Vallortigara is a professor of cognitive neuroscience at the Center for Mind/Brain Sciences and in the department of cognitive sciences at the University of Trento in Italy.


The division of labor by the two cerebral hemispheres—once thought to be uniquely human—predates us by half a billion years. Speech, right-handedness, facial recognition and the processing of spatial relations can be traced to brain asymmetries in early vertebrates.

The specialization of each hemisphere in the human brain was already present in its basic form when vertebrates emerged about 500 million years ago. The more recent specializations of the brain hemispheres, including those of humans, evolved from the original ones by the Darwinian process of descent with modification.

The left hemisphere of the vertebrate brain was originally specialized for the control of well-established patterns of behavior under ordinary and familiar circumstances. In contrast, the right hemisphere, the primary seat of emotional arousal, was at first specialized for detecting and responding to unexpected stimuli in the environment.

The left hemisphere became the seat of self-motivated behavior, sometimes called top-down control. (We stress that self-motivated behavior need not be innate; in fact, it is often learned.) The right hemisphere became the seat of environmentally motivated behavior, or bottom-up control. The processing that directs more specialized behaviors—language, tool-making, spatial interrelations, facial recognition, and the like—evolved from those two basic controls.

Sheep can recognize the faces of other sheep (and of people) from memory and that the right hemisphere is preferentially involved. Similar behavior is also observed in monkeys.

In humans neuroscientists have recently recognized that the right hemisphere specializes in face recognition. Prosopagnosia, a neurological disorder that impairs that ability, is more often a result of damage to the right hemisphere than to the left.

Memories stored by the right hemisphere tend to be organized and recalled as overall patterns rather than as a series of single items. In contrast, the left hemisphere tends to focus on local aspects of its environment.

The uneven proportion of left- and right-type individuals in many populations thus indicates that the imbalance must be so valuable that it persists despite the increased vulnerability to predators. Rogers and Vallortigara have suggested that, among social animals, the advantage of conformity may lie in knowing what to expect from others of one’s own species.

What are the relative roles of the left and right hemispheres in having self-awareness, consciousness, empathy or the capacity to have flashes of insight? Little is known about those issues. But the findings we have detailed suggest that these functions—like the other human phenomena discussed here—will be best understood in terms of the descent with modification of pre-human capabilities.

MacNeilage has proposed that the making of syllabic utterances is an evolutionary modification of routine chewing behavior, which first evolved in mammals 200 million years ago.

[Please see the comments for some interesting latest scientific research results.]

Added on 25 Oct 2011:
Video of about 11 minutes:
"How have our two hemispheres evolved to relate -- and how did their relationship create our consciousness, our culture, and our ability to understand our own brains?"

Added on 22 Dec 2011:
About left-brain/right-brain differences: 
"The scientists found that signals coming from the left hippocampus led to a strengthening of long-term electrical connections between neurons. This strengthening of connections is a widely accepted model of learning and memory in the brain. It is thought to be associated with how we lay down new memories.In contrast, there were no such changes with signals coming from the right hippocampus.There was a striking difference. It suggests that the left and right hippocampus in the mouse have distinct functions in learning and memory processes."

Added on 09 Jan 2012:  
How does our brain know what is a face:
"On the left side of the brain, the fusiform gyrus — an area long associated with face recognition — carefully calculates how "facelike" an image is. The right fusiform gyrus then appears to use that information to make a quick, categorical decision of whether the object is, indeed, a face.
This distribution of labor is one of the first known examples of the left and right sides of the brain taking on different roles in high-level visual-processing tasks,  although hemispheric differences have been seen in other brain functions, most notably language and spatial perception."

Added on 02 Mar 2012:
When one side does not know about the other one
"Whenever we are doing something, one of our brain hemispheres is more active than the other one. However, some tasks are only solvable with both sides working together. Based on a pigeon-model, they are proving for the first time in an experimental way, that the ability to combine complex impressions from both hemispheres, depends on environmental factors in the embryonic stage."

Added on 19 Mar 2012:
The split brain studies: 

"Through studies of this group, neuroscientists now know that the healthy brain can look like two markedly different machines, cabled together and exchanging a torrent of data. But when the primary cable is severed, information — a word, an object, a picture — presented to one hemisphere goes unnoticed in the other. The brain isn't like a computer, with specific sections of hardware charged with specific tasks. It's more like a network of computers connected by very big, busy broadband cables. The connectivity between active brain regions is turning out to be just as important, if not more so, than the operation of the distinct parts. The left-brain interpreter, Gazzaniga says, is what everyone uses to seek explanations for events, triage the barrage of incoming information and construct narratives that help to make sense of the world."

Added on 21 Apr 2012:
Your left side (of face) is your best side:
"Your best side may be your left cheek, according to a new study by Kelsey Blackburn and James Schirillo from Wake Forest University in the US. Their work shows that images of the left side of the face are perceived and rated as more pleasant than pictures of the right side of the face, possibly due to the fact that we present a greater intensity of emotion on the left side of our face."

Added on 06 June 2012:
Are emotions and feelings the domain of the right hemisphere only?
"Ours is the first study from patients with dementia to show that language-based areas of the brain, primarily on the left, are important for extracting emotional meaning from music. Our findings suggest that the brain considers melodies and speech to be similar and that overlapping parts of the brain are required for both."

Added on 03 Nov 2012:
'New beginning' in split-brain research:
"Split-brain research has been conducted for decades, and scientists have long ago shown that language processing is largely located in the left side of the brain. When words appear only in the left visual field –– an area processed by the right side of the brain –– the right brain must transfer that information to the left brain, in order to interpret it. The new study at UCSB shows that healthy test subjects respond less accurately when information is shown only to the right brain. While hemispheric specialization is considered accurate, the new study sheds light on the highly complex interplay  –– with neurons firing back and forth between distinct areas in each half of the brain.This study shows that the strength of communication across the brain changes dynamically, when information is exchanged between the right and left hemispheres via the corpus callosum, which connects both sides of the brain."

Added in Nov 2012:
Uncommon features of Einstein's brain might explain his remarkable cognitive abilities:
Portions of Albert Einstein's brain have been found to be unlike those of most people and could be related to his extraordinary cognitive abilities, according to a new study led by Florida State University evolutionary anthropologist Dean Falk.
Falk, along with colleagues Frederick E. Lepore of the Robert Wood Johnson Medical School and Adrianne Noe, director of the National Museum of Health and Medicine, describe for the first time the entire cerebral cortex of Einstein's brain from an examination of 14 recently discovered photographs. The researchers compared Einstein's brain to 85 "normal"  and, in light of current functional imaging studies, interpreted its unusual features.
"Although the overall size and asymmetrical shape of Einstein's brain were normal, the prefrontal, somatosensory, primary motor, parietal, temporal and occipital  were extraordinary," said Falk, the Hale G. Smith Professor of Anthropology at Florida State. "These may have provided the neurological underpinnings for some of his visuospatial and mathematical abilities, for instance."
Added on 4 Oct 2013:
Well-connected hemispheres of Einstein's brain sparked brilliance?:
"The left and right hemispheres of Albert Einstein's brain were unusually well connected to each other and may have contributed to his brilliance, according to a new study conducted in part by Florida State University evolutionary anthropologist Dean Falk.

"This study, more than any other to date, really gets at the 'inside' of Einstein's," Falk said. "It provides new information that helps make sense of what is known about the surface of Einstein's brain."

The study, "The Corpus Callosum of Albert Einstein's Brain: Another Clue to His High Intelligence," was published in the journal Brain. Lead author Wei wei Men of East China Normal University's Department of Physics developed a new technique to conduct the study, which is the first to detail Einstein's corpus callosum, the brain's largest bundle of fibers that connects the two cerebral hemispheres and facilitates inter-hemispheric communication.

Added on 23 Oct 2013: 
Right brained? Left brained?  A 30 sec test:

Added on 22 Nov 2013:  
Different gene expression in male and female brains:
UCL scientists have shown that there are widespread differences in how genes, the basic building blocks of the human body, are expressed in men and women's brains.
Based on post-mortem adult human brain and spinal cord samples from over 100 individuals, scientists at the UCL Institute of Neurology were able to study the expression of every gene in 12 brain regions. The results are published today in Nature Communications.
They found that the way that the genes are expressed in the brains of men and women were different in all major brain regions and these differences involved 2.5% of all the genes expressed in the brain.