In a very real sense, what I’m working from in writing this blog is the aftermath of writing a doctoral dissertation in 1982 as a grad student in the Humanistic and Behavioral Studies Department of Boston University’s School of Education. It took decades for me to shake off the academic tone I adopted in writing a 625-page book that, as far as I know, no one has read all the way through except me.

More particularly, I am working through the lessons I learned in writing Chapter 5, Pheromones to Phenomena, which dealt with the workings of the brain as understood at that time (largely based on animal studies). When I go back and read that chapter, I find what I wrote then is still true for me today. Not that my growth was stunted from then-on; more that what I hit upon in that chapter about the neural underpinnings of perception, judgment, and memory still serves as an excellent model for the mind revealed to me through introspection.

Of course we find in the world largely what we expect to find, so it sounds like I am indulging in a self-fulfilling prophesy. But that’s not what I mean. What I wrote then about the nature of consciousness still helps me to understand my mind of today. If it didn’t, I wouldn’t be writing this blog.

Not that I literally remember those thoughts from yesteryear. They surprise me every time I go back and read them. It’s the unspoken sense of concentration and commitment that drove me to write the dissertation that sticks with me. Now reduced to an intuitive feel for the topic I am writing about, a kind of silent presence in the background that guides me twenty-three years later.

I began Chapter Five, Pheromones to Phenomena, with the radical switch our species had to make from reliance on our ancestors’ sense of smell to living in a higher world with almost no smell at all. When we stood up on our hind legs, our jaws and snouts lessened, and we had to compensate for what we lost by rapidly developing our senses of vision and hearing, along with the ability to control muscles governing balance, posture, stance, and precise movement of our fingers.

It is the experience of thinking those thoughts that I retain to this day, not writing about what gradually happened to the amygdala, hippocampus, cerebral cortex, and other perceptual systems in having to adapt to a world without pheromones.

I was wholly engaged with my topic when I wrote my dissertation letter-perfect (with White-out) on an IBM Selectric typewriter, and it is what my brain has done with that engagement that I carry with me today, not the actual words and citations.

I know because I went back and read Chapter Five: there it all was in splendid detail. When I practice introspection in writing about the foibles of my own mind, that process is backed up by the deep concentration I put into clicking away at my typewriter day-after-day for over two years. And into scouring the sources I read in the years before that.

The difference between then and now is that today I am trying to write in English appropriate to a blog aimed at a general audience, not academic English as suited to dissertation committees and peer reviewers. It has taken this long to shed old habits learned in school, and as you can tell from reading these posts, I am still trying to overcome a natural bent to make simple things sound complicated.

Are my ideas now out-of-date because they are descendants of ideas I wrestled with in grad school? Or even earlier? I’ve written about the important role memory plays in perception, so that the words I write today go back to the language I babbled when I was an infant. Are my words as old as I am? I say, no, because I see myself as a trainable who can adapt to changing times. Words do change, but not as fast as people do. By reading a few notes, we can still make sense of Chaucer and Shakespeare, if not Beowulf—all far older than I am.

So what did I write in my dissertation? Here are some samples from Chapter Five of Metaphor to Mythology (Ann Arbor: University Microfilms International, 1982). In these excerpts, because olfactory bulbs (smell receptors) in our ancestors have such immediate access to the hippocampus and limbic system, the interactive components that make up that system are featured, including hippocampus, amygdala, and hypothalamus. I am using these bulleted quotations to illustrate the specialized world I inhabited in grad school.

  • The entire cortex is an evolutionary derivative of the sense of smell (page 259).
  • Our erect posture, by distancing our olfactory receptors from the sources of smell, has deprived us of the benefits of pheromonal [olfactory signal] communication, so it is not surprising that we have increasingly come to rely on non-chemical means for integrating our internal state with our environment (page 260).
  • The limbic system operates basically as a “selection unit” to determine the biological value of sensory information in relation to various organic drives, and then functions to facilitate the storage of information deemed relevant to successful functioning of the organism (page 263).
  • The regulation of cognitive function shifts away from the processing of pheromonal signals to the identification and evaluation of cues in the visual and auditory modalities. What remains constant, however, is the crucial role of the hippocampus (and the limbic system in general) in learning, memory, communication, and social organization (page 264).
  • The interpretation of neurological studies often relies heavily upon the twin concepts of the internal and external milieu. . . . homologous to one-celled animals in which a semipermeable membrane separates an “inside” from an “outside.” The internal milieu represents the equilibrated chemical innards that constitute the life-sustaining works of the organism; the external milieu being the sum total of all ambient stimulation an investigator can imagine to be impinging upon its sensibilities (page 268).
  • [Hippocampal] function is related to the enduring consequences of a comparison (seeing one signal in terms of another, a kind of seeing-as) between two different classes of sensory input—one primarily sensory, the other . . . facilitated by precedent episodes of similar experience (page 277f.).
  • Under novel circumstances it would be the hippocampus that would effect a comparison between perception and memory, emitting a signal that would be proportional to the non-familiarity of the sensory signal, and leading to exploratory behavior designed to acquire a more coherent and detailed version of that signal. Comparisons resulting in a high degree of registration would enable the animal to make a response on the basis of an assumed identification to which the existing repertoire of behaviors would more likely be both adequate and appropriate (page 280).
  • Since an animal’s sensory stimulation will vary in accordance with its own locomotion, it is essential that some mechanism be available to distinguish between self-generated and environment-generated variation in sensory input. To accomplish this, signals that exhibit covariation with proprioceptive input from muscle spindles and receptors in tendons and joints must be credited to the organism itself and subjected to inhibition in order to determine the coherent pattern of sensation that can be attributed to stimuli in the environment (page 282).
  • The normal animal lives neither for the moment nor for the past, but is able to compare the two and make an appropriate response to adjust the difference. It is able to find meaning in its phenomenological milieu and, when it can’t, to embark on a series of excursions that will enable it to discover appropriate meanings for novel phenomena. And if those meanings are repeated often enough, or are important enough, then the normal animal is capable of remembering them (page 283f.).
  • The hippocampus, as a novelty detector, directs its output to several important destinations: to the hypothalamus, the custodian of the internal milieu; to the midbrain reticular formation, regulator of arousal and wakefulness; to the prefrontal areas in which so many separate signals are coordinated; and to itself, via a kind of reverberating feedback loop that turns momentary stimuli into enduring potentations that influence its own activity. In each case it acts like a switch that turns another operation on or off, depending on the disparity between the signals it receives. From its central location it influences motivation, arousal, sensory coherence, interference, memory, meaning, and behavior (page 284).
  • Since the business of memory is survival (by making lessons learned in the past available on suitable occasions in the present), it is not surprising that these survival-related functions form the core of many of our strongest memories (page 286).
  • The hippocampus (and its associated network of connectivities to related areas) thus makes it possible for repeated episodes of similar sensory signals to exert a systemic influence that renders them familiar and—beyond that—meaningful. Such signals are more readily “welcomed” by the perceptual system because they “speak” to prior experience, to the heritage of the perceiver. And, since they address not an identical replica of themselves but an abstraction derived from multiple repetitions (or approximations) over time, their reception occurs within a framework of historical reference that equates their existential pattern of sensory stimulation with something already in the perceiver’s possession, with a referential meaning that is already an aspect of the perceiving apparatus itself (page 292).
  • Sensory signals, . . . are like keys that acquire a meaning by being inserted into certain locks that anticipate their configuration; sensations are different from meanings in the same sense those keys are different from the locks that they open. And, to continue the simile, the hippocampus is the locksmith who adjusts the lock to fit those keys that are repeatedly or forcefully imposed upon their workings (page 292).
  • The salient feature of context-related memory is the influence it exerts upon the process of perception. . . . Its primary function is to direct attention toward those aspects of a situation that are most likely to prove pertinent to the motivational state of the individual perceiver. It is a reaching-out for perception on the basis of an authority vested in the ongoing interaction between self and world as it has been achieved in the current (or immediately prior) situation. Thus does experiential meaning, once unlocked, strive to perpetuate itself by [putting] itself forward on the basis of its recent successes, attempting to discriminate a world that would fulfill its current promise as if foretold as a kind of destiny—like a lock awaiting to be fulfilled by a certain key(page 295).
  • [I]t is no accident that our ideas nest within each other so conveniently, that our understanding is hierarchical in nature, allowing the most venial notion to coexist with our highest ideals, the mundane with the celestial, the profane with the sacred. For all its complexity, the paramount achievement of the brain is the selection and synchronization of its ongoing processes so that mind is characterized by a coherent flow of ideas that provides a continuous rationale for purposive behavior (page 301).
  • [Our] strategy [is] to present ourselves to the world from the security of our heritage of personal experience, and to weld whatever patterns we discovery firmly to the structure we have already built. The world we see is the world we have learned to see. That is the genius of our species and the secret of our survival: the world is always contingent upon the way we present ourselves to it—upon the way we have learned to seize it. No miracle is more profound because, instead of granting us eternal wisdom, it challenges us to pursue every opportunity for learning, and to remain open to the worlds that others have discovered for themselves (page 317).

So, no, I’m not making-up these posts as I go along. They are deeply rooted in my life’s cumulative endeavors and experience. That is, in the flowing situations in my innermost parts that give meaning to my life.

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(Copyright © 2009)

 

In the movie Donovan’s Brain, poor Donovan is reduced to a brain hooked up to wires in a jar, sharing his thoughts through a loudspeaker in the lab. We often entertain the careless thought that, like Donovan, the brain represents the consciousness of a whole person. But the brain is only part of a body which keeps it active and alive. A brain abstracted from its body is a dead brain. In discussing activities in different parts of the brain, it is essential to remember that no mental activity would be happening apart from the context the body provides. The brain is not the motor under the hood (“bonnet” in England) that makes us work. Heart, liver, kidneys, fingers, toes, and all the other parts of a functioning organism are implicit in pictures of the brain by itself.

 

Having said that, right now I want to consider the human brain as a complex organ which itself is composed of parts. My focus is on parts of the brain which may contribute to consciousness in particular. If you read books or articles about the brain, you very quickly encounter terms used by neuroscientists, terms which have limited currency outside the lab. Since I myself have uses such terms in earlier posts (amygdala, hippocampus, cerebral cortex, cerebellum), I want to lay the groundwork for future posts so that such terms will be helpful in developing further insights into consciousness. To do that, I will refer to two illustrations. 

 

 

illustration-1-72

Illustration 1. Here, the left side of the cerebral hemisphere is divided into four lobes, each represented by a different color. The frontal lobe is shown in blue, parietal lobe in yellow, temporal lobe in green, and occipital lobe in pink. The cerebellum (not part of the cerebral cortex) is also shown, looking like a ball of yarn in black in white tucked under the temporal lobe.

 

cut-away-view-72

Illustration 2. Here outer layers of the left cerebral hemisphere are cut away to suggest the locations of several parts which lie deeper in the brain near the midline between the two hemispheres. (Clockwise from the top) The corpus callosum consists of nerve fibers connecting the two hemispheres. The cerebral cortex is made up of six layers of nerve cells and the fibers connecting them one to another. The thalamus is a complex relay station between the cerebral cortex and other parts of the central nervous system. The cerebellum contains over half the cells in the brain, and is largely devoted to eye and muscle coordination. The brain stem is the seat of cognitive and emotional arousal systems. The hippocampus facilitates long-term memory storage and retrieval. Not shown, but near the hippocampus is the amygdala which plays an essential role in emotional responses including fear and anxiety. The hypothalamus regulates the autonomic nervous system which maintains life-sustaining processes at appropriate levels; it is a key link between the body’s nervous and hormonal systems.

 

The human brain contains an estimated 100 billion nerve cells, each of which may form 1-10 thousand connections with other cells, producing well over 100 trillion opportunities for activation and feedback. When a given neuron (brain cell) fires, it receives feedback from other cells as a kind of consensus concerning whether it should continue to fire or not. Feedback shapes every activity in the brain and, ultimately, the conscious and unconscious processes governing bodily functions and behavior.

 

 

BBC Brain Map

 

For this post I will give a brief run-through of the functions of the various areas of the brain I have listed above, more or less according to the order in which they have been introduced.

 

Cerebellum. A fixture of the vertebrate brain, the cerebellum is particularly developed in primates and humans. It controls balance, spatial orientation, eye movements, muscle movements (as in reaching and locomotion), and planning of such movements. When there is a discrepancy between movements as planned and executed, the cerebellum facilitates correction.

 

Cerebral Cortex. Cell bodies in the cerebral cortex are arranged in thin layers near the outer surface of the cerebral hemispheres. This arrangement facilitates orderly routing of inputs and outputs between related areas of the brain. The surface of the cortex is larger than that of the inside of the skull because of its folding into valleys (sulci) and hills (gyri), which greatly expands the number of neurons that can fit into a small space. The bulk of the cortex consists of interconnecting fibers. Among vertebrates, humans have the most finely elaborated cortex, allowing detailed planning and execution of a wide diversity of behaviors. The cortex is divided into lobes (named after neighboring bones of the skull) based on prominent anatomical features. These designations are somewhat arbitrary, but the cellular architecture exhibited in different areas lends support to the integrity of different functions within separate lobes (see separate listings below).

 

Corpus Callosum. Nerve fibers connecting corresponding areas of the left and right cerebral hemispheres cross the midline of the brain in a large bundle known as the corpus callosum. These fibers appear white because of the myelin sheaths wrapping individual fibers, greatly increasing the speed of transmission. Each fiber is the axon connecting the body of a particular cell on one side of the cortex to related cells on the opposite side. In general, nerve cells (neurons) on one side of the brain control functions performed on the other.

 

Frontal Lobe. The frontal lobe of cerebral cortex extends forward of the central sulcus at the top of the brain which separates it from the parietal lobe to the rear. Cells in the primary motor area are arranged along the central sulcus as a topographical map of the muscles in areas of the body which they control, extending from feet represented in the fissure between hemispheres, through legs, trunk, arms, hands, fingers, head, face, and mouth arrayed across the surface of the primary motor area of the cortex. Forward of that is the premotor area where planning of motor behaviors takes place. Speech muscles in tongue and lips are controlled in Wernicke’s area within the frontal lobe. Working memory (or focused attention) integrate three different areas—lateral, orbital, and cingulate—within prefrontal cortex to provide what some researchers believe to be the neurological basis of consciousness.

 

Parietal Lobe. Similar to the motor map in the frontal lobe, a sensory map of the body spreads across neurons at the leading edge of the parietal lobe. Touch, pain, and temperature signals are processed in the parietal lobe, which also processes the interplay between visual and bodily sensations.

 

Occipital Lobe. At the back of the brain, the occipital lobe is devoted entirely to primary and subsequent visual processing. There are some 40 visual processing areas in the brain, but they all depend on signals received from the occipital lobe.

 

Temporal Lobe. Primary auditory processing takes place in the temporal lobe, as well as later stages of visual processing, including image recognition. The amygdala and hippocampus exist in pairs (one on each side of the brain) and are located deep within the temporal lobes near the midline between the two hemispheres.

 

Thalamus. As a relay station, the thalamus receives signals from sensory receptors and sends output to cortical sensory processing areas. Thalamic activity coordinates electrical activity in cortical neurons, giving rise to synchronized waves (basis of the electroencephalogram—the EEG). Consciousness, it is thought, represents synchronized activity throughout the cerebral cortex. Ascending pathways from the brain stem and hypothalamus pass through the thalamus en route to the cerebral cortices, conveying vital signals that maintain arousal, vigilance, and responsiveness to sensory stimuli. Injury to the thalamus can bring about loss of consciousness.

 

Brain Stem. The difference between sleep and wakefulness is largely told by neurons in the brain stem where both autonomic and emotional stimuli come into play with profound implications for arousal, attention, and consciousness. Though this region of the brain is primitive in some senses, its involvement in such basic processes suggests that consciousness is not necessarily a latecomer on the evolutionary totem pole.

 

Hippocampus. A specialized region of cortical cells near the midline of the brain, the hippocampus is essential to laying down and retrieving long-term memories. It is involved in learning and establishing spatial relations. Alzheimer’s disease involves failure of hippocampal function.

 

Amygdala. The amygdala comes into play in threatening situations. Sensory input reaches the amygdala from the thalamus by two different routes, one slow but made clear by the cerebral cortex, the other fast but relatively unprocessed and therefore crude. In emergencies, the fast route may spur immediate, life-saving action. The amygdala generates outputs affecting blood pressure, stress hormones, and both startle and immobilizing reflexes. It also kicks into the hippocampus, enabling long-term memory of emotional situations. Feelings of fear, anxiety, anger, and loathing are conscious signs of activity in the amygdala, location of a sophisticated early warning network.

 

Hypothalamus. The hypothalamus maintains homeostasis across a wide range of circumstances by providing inputs to the autonomic nervous system (which silently regulates bodily functions, including sexual arousal), the hormonal system, and the motivational system. It maintains a feedback loop by which neuronal activity can stimulate hormone production, and hormones in turn can affect brain activation. By such means, the hypothalamus integrates autonomic and hormonal functions with behavior.

 

Anterior Cingulate Cortex. On the medial surface of the cerebral hemispheres, the cingulate cortex arcs above the fibers of the corpus callosum crossing beneath it. Much like the brain stem, anterior cingulate cortex participates in homeostasis, emotions, attention, sleep and wakefulness, learning, and consciousness itself. Cingulate cortex also receives musculoskeletal inputs, and sends a large variety of output signals to motor areas related to speech, movement, and other bodily responses. Lesion studies suggest that patients with damage to this area are deprived of an active inner (conscious) life.

 

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