Dharani The Biology of Thought

A Neuronal Mechanism in the Generation of Thought - A New Molecular Model
1. Auflage 2014
ISBN: 978-0-12-801161-4
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 248 Seiten

The question of 'what is thought' has intrigued society for ages, yet it is still a puzzle how the human brain can produce a myriad of thoughts and can store seemingly endless memories. All we know is that sensations received from the outside world imprint some sort of molecular signatures in neurons - or perhaps synapses - for future retrieval. What are these molecular signatures, and how are they made? How are thoughts generated and stored in neurons? The Biology of Thought explores these issues and proposes a new molecular model that sheds light on the basis of human thought. Step-by-step it describes a new hypothesis for how thought is produced at the micro-level in the brain - right at the neuron. Despite its many advances, the neurobiology field lacks a comprehensive explanation of the fundamental aspects of thought generation at the neuron level, and its relation to intelligence and memory. Derived from existing research in the field, this book attempts to lay biological foundations for this phenomenon through a novel mechanism termed the 'Molecular-Grid Model' that may explain how biological electrochemical events occurring at the neuron interact to generate thoughts. The proposed molecular model is a testable hypothesis that hopes to change the way we understand critical brain function, and provides a starting point for major advances in this field that will be of interest to neuroscientists the world over. - Written to provide a comprehensive coverage of the electro-chemical events that occur at the neuron and how they interact to generate thought - Provides physiology-based chapters (functional anatomy, neuron physiology, memory) and the molecular mechanisms that may shape thought - Contains a thorough description of the process by which neurons convert external stimuli to primary thoughts

Dr. Dharani graduated from Kurnool Medical College, Kurnool (Andhra Pradesh) in 1987, and did his Master of Surgery from Kasturba Medical College, Manipal (South Karnataka) in 1992. He completed his Senior Residency in Vascular Surgery from Nizam's Institute of Medical Sciences, Hyderabad (Andhra Pradesh) and is presently working as a Senior Civil Servant in AP Medical Services. He is also a science promotional writer, and has written a locally published book titled 'The Role of Cell Membrane in the Origin of Life. His articles have been published in various Indian Science Journals such as ScienceIndia, Amity College of Biotechnology (Noida), local magazines and others. He can be contacted with queries at [e-mail]."

Autoren/Hrsg.

Dharani, Krishnagopal

Inhaltsverzeichnis

1;Front Cover;1
2;The Biology of Thought;4
3;Copyright Page;5
4;Contents;6
5;Preface;10
6;Introduction;12
6.1;What is ‘The Biology of Thought’?;12
6.2;How is This Book Organized?;13
6.3;Authors’ Note: On the Uses of the Molecular-Grid Model;15
7;Sources and Acknowledgments;18
8;I. Basic Concepts in Neurobiology;20
8.1;1 Functional Anatomy of the Brain;22
8.1.1;Overview;22
8.1.2;General Plan of the Nervous System;22
8.1.2.1;Anatomical Considerations;22
8.1.2.2;Types of Neurons;24
8.1.3;Structure of the Brain;28
8.1.4;Cerebral Cortex;28
8.1.4.1;Lobes of the Brain;29
8.1.4.2;Cortical Connectivity;33
8.1.4.3;Cortical Plasticity;35
8.1.4.4;Cerebral Asymmetry;35
8.1.5;Microscopic Anatomy of Cortex;36
8.1.5.1;Neuron;36
8.1.5.2;Neuroglia;37
8.1.6;Structural Types of Neurons;37
8.1.6.1;Pyramidal Cells;37
8.1.6.2;Laminar Organization of Cortex;38
8.1.6.3;Rebirth of Neurons;39
8.1.7;Diencephalon;39
8.1.7.1;Thalamus;40
8.1.7.2;Hypothalamus;41
8.1.7.3;Pituitary Gland;42
8.1.7.4;Pineal Gland;43
8.1.8;Basal Ganglia;43
8.1.8.1;Parkinson’s Disease;44
8.1.9;Brainstem;44
8.1.10;Cerebellum;45
8.1.10.1;Parts of Cerebellum;45
8.1.10.2;Cerebellar Circuits;46
8.1.11;Spinal Cord;47
8.1.12;Peripheral Nerves;47
8.1.12.1;Cranial Nerves;48
8.1.12.2;Spinal Nerves;48
8.2;2 Physiology of the Neuron;50
8.2.1;Overview;50
8.2.2;General Plan of Nervous System;50
8.2.2.1;Physiological Considerations;50
8.2.2.2;External Stimuli;50
8.2.2.3;Internal Stimuli;51
8.2.2.4;Signals That ‘Pass Up’;51
8.2.2.5;Interneurons;53
8.2.2.6;Signals That ‘Pass Down’;54
8.2.2.7;Complexity of Connections;54
8.2.3;Mechanism of Neuronal Electrical Activity;54
8.2.3.1;The Electrical Signal;54
8.2.3.2;Polarization, Depolarization and Hyperpolarization;55
8.2.3.3;Types of Ion Channels;57
8.2.3.4;Action Potentials;58
8.2.3.5;Graded Potentials;59
8.2.3.6;Unidirectional Flow of Information;61
8.2.4;Soma;61
8.2.4.1;Cytoskeleton;61
8.2.5;Dendrites;62
8.2.6;Axon;63
8.2.6.1;Myelinated Axons;63
8.2.7;Synapse;64
8.2.7.1;Types of Synapses;65
8.2.8;Signaling Activity of Neurons: A Summary;66
8.2.9;Neurotransmitters;68
8.2.9.1;A Few Examples of NTs;69
8.2.10;Energetics;71
8.3;3 Memory;72
8.3.1;Overview;72
8.3.2;How is Memory Initiated?;73
8.3.2.1;General Mechanism of Vision;73
8.3.2.2;Visual Neural Pathways;74
8.3.2.3;Other Sensations;75
8.3.3;Formation of Memory;76
8.3.3.1;Sensory Memory;76
8.3.3.2;Short-Term Memory;77
8.3.3.3;Working Memory;77
8.3.3.4;Long-Term Memory;78
8.3.3.5;Explicit Memory;79
8.3.3.6;Implicit Memory;81
8.3.4;Mechanism of LTM Formation;81
8.3.4.1;Outlines of LTM Formation;81
8.3.4.2;Hippocampus;82
8.3.4.3;The Papez Circuit;84
8.3.5;Neuronal Basis of Memory;85
8.3.5.1;Synapses and Neuronal Networks;85
8.3.5.2;Synaptic Plasticity: The Role of NTs;87
8.3.5.3;Synaptic Plasticity: The Role of Dendritic Spines;89
8.3.6;Factors Affecting Memory;90
8.3.7;Some Phenomena Related to the Brain;91
8.3.7.1;Language;91
8.3.7.2;Sleep and Dreams;92
9;II. The Molecular-Grid Model;94
9.1;4 Primary Thoughts and Ideas;96
9.1.1;Overview;96
9.1.2;Concept of Primary Thought;96
9.1.3;Primary Thought as a Fundamental Unit;97
9.1.3.1;What Is a Primary Thought?;97
9.1.3.2;What is an Idea?;98
9.1.3.3;Characteristics of Primary Thoughts;99
9.1.3.4;Characteristics of Ideas;100
9.1.3.5;Examples of Primary Thoughts and Ideas;102
9.1.4;Primary Thoughts and Memory;103
9.1.4.1;Primary Thoughts and Molecular Gadgets;103
9.1.4.2;Primary Thought and Memory are Interdependent;103
9.1.4.3;A Few Examples;104
9.1.5;Sensory Experience is the Same Irrespective of Stimulus;104
9.1.5.1;Explanation;104
9.1.5.2;One Interesting Phenomenon is That of Phosphenes;105
9.1.5.3;Why are There so Many Receptors?;105
9.1.6;We Can Only Sense What our Mind Knows;106
9.1.6.1;Explanation;106
9.1.7;How Innovative is Human Thought?;107
9.1.7.1;Explanation;107
9.1.7.2;The Alien;108
9.1.7.3;Dreams and Hallucinations;108
9.1.7.4;Fiction is No More Fiction;109
9.1.8;Primary Thoughts are Inherited;109
9.1.8.1;Explanation;109
9.2;5 The Perceptual Neurons;112
9.2.1;Overview;112
9.2.2;Pathways of Perception;113
9.2.2.1;Touch Sensation;113
9.2.2.2;Pain Sensation;115
9.2.3;Perceptual Neurons;117
9.2.3.1;The Generation of Primary Thoughts;118
9.2.3.2;Referral Actions;119
9.2.3.3;Interneurons;120
9.2.4;Simple Ideas and Complex Ideas;121
9.2.4.1;The Human Sensory Cortex;122
9.2.4.2;Generation of Simple Ideas and Complex Ideas;122
9.2.4.3;Information Processing in Other Cortical Areas;124
9.2.5;Locating Perceptual Neurons in the Cortex;125
9.2.5.1;Transmission of Signals in the Neocortex;125
9.2.5.2;Level-IV Neurons as Perceptual Neurons;127
9.3;6 Dendrites and Primary Thoughts;128
9.3.1;Overview;128
9.3.2;General Outlines;128
9.3.3;Events at Synapses;129
9.3.3.1;Axodendritic Synapses;129
9.3.4;Events at Axons;131
9.3.4.1;‘Labeled Line’ Principle;132
9.3.5;Events at Dendrites;132
9.3.5.1;Dendritic Spines;133
9.3.5.2;Protein Synthesis and Dendrites;134
9.3.5.3;Pruning of Dendrites;134
9.3.6;Electrical Activity at Dendrites;134
9.3.7;Where in The Neuron?;136
9.3.7.1;Refuting ‘The Whole Neuron Concept’;136
9.3.7.2;Dendrites Generate Primary Thoughts;137
9.3.7.3;Conclusion;138
9.3.7.4;Which Portion of Neuron?;139
9.3.8;The Final Conclusion;141
9.4;7 Molecular-Grid Model;142
9.4.1;Overview;142
9.4.2;Cell Membrane;142
9.4.2.1;Structure of Cell Membrane;143
9.4.2.2;Selective Permeability;145
9.4.2.3;Types of Transport;145
9.4.3;Lipid Rafts and Microdomains;146
9.4.3.1;The Lipid Component;147
9.4.3.2;The Protein Component;148
9.4.4;Signal Transduction in Neurons;148
9.4.4.1;Receptors in Neurons;149
9.4.4.2;Ion Channel-Linked Receptors and Graded Potentials;151
9.4.5;Anatomy of Molecular Grid;152
9.4.5.1;What is a Molecular Grid?;152
9.4.5.2;Proofs of Molecular Grids;154
9.4.6;Mechanism of Generation of Primary Thoughts;155
9.4.6.1;The ‘Thought-Potentials’;156
9.4.6.2;What is a Primary Thought?;158
9.4.7;Genetic Basis of Primary Thoughts;159
9.4.8;Molecular Grids as ‘Biological Transistors’;160
9.5;8 Memory, Intelligence and Molecular Grid;162
9.5.1;Overview;162
9.5.2;Memory: A Review;162
9.5.2.1;Progression of Memory;163
9.5.3;Molecular Mechanism of Memory;164
9.5.3.1;Formation of Memory Traces;164
9.5.3.2;Dendrodendritic Synapses;166
9.5.3.3;The Role of Electrical Synapses;167
9.5.3.4;Chemical Synapses;168
9.5.4;Storage of Memory and Recall;170
9.5.4.1;Dendritic Pleats;170
9.5.4.2;Dendritic Pleats and Progression of Memory;172
9.5.4.3;Memory Recall;173
9.5.4.4;Mechanism of Durability of Memory;174
9.5.4.5;Dendritic Plasticity: Formation of New Memories;175
9.5.4.6;Protein Synthesis and Memory;175
9.5.4.7;Evidence for Dendritic Pleats;176
9.5.5;Forgetfulness;176
9.5.6;Intelligence;177
9.5.6.1;Proteins and Intelligence;178
9.5.6.2;Lipids and Intelligence;178
9.5.7;Some Weird but Explainable Phenomena;178
9.5.7.1;Are There Memory Traces at Birth? (Memory Traces sans Memories);179
9.5.7.2;Child Prodigy;179
9.5.7.3;Hallucinations and Déjà vu;180
10;III. The Evolution of Human Mind;182
10.1;9 Mind and Consciousness;184
10.1.1;Overview;184
10.1.2;Evolution of the Human Mind;184
10.1.2.1;Perception as Awareness;185
10.1.2.2;Origin of Consciousness and Mind;186
10.1.2.3;The Human Mind;187
10.1.3;Evolution of the Central Executive;190
10.1.3.1;The Unique Central Executive!;191
10.1.3.2;Will and Volition;193
10.1.3.3;The Will in Plants and Microorganisms;196
10.1.3.4;Can the Will Be Conquered?;197
10.1.3.5;The Phenomenon of Reproduction;198
10.1.4;Volition, Memory and Central Executive;198
10.1.4.1;Memory and Central Executive;199
10.1.4.2;Evolution of Central Executive;199
10.1.5;Will Versus Volition;201
10.1.5.1;The Conflict between Will and Volition: The Origin of Emotions;201
10.1.5.2;When the Will Loses the Battle!;203
10.1.6;The Wine-Glass Analogy!;204
10.2;10 Metaphysics of Thought;206
10.2.1;Overview;206
10.2.2;The Problem of the Observed: The Enigma of the External World;207
10.2.2.1;Determinism;207
10.2.2.2;Indeterminism;209
10.2.3;The Problem of the Observer: The Paradox of the Human Mind;210
10.2.3.1;Realism versus Idealism;210
10.2.3.2;How Dependable are Our Senses?;211
10.2.3.3;The Paradox of Free Will;213
10.2.3.4;The Illusion of Free Will (No Free Will);215
10.2.3.5;Man, The Super Animal (Free Will Present);216
10.2.3.6;Free Will in Animals;216
10.2.4;How is Thought Initiated?;217
10.2.4.1;A de novo Thought;217
10.2.4.2;Externally-Induced Thoughts;217
10.2.4.3;A Third Type of Thought Inducement;218
10.2.5;Who am ‘I’?;218
10.2.5.1;Neuron as the Observer;219
10.2.5.2;The Ultimate Paradox;221
10.2.5.3;A Final Note: Roads to Quantum Consciousness;222
11;IV. The Computer and the Brain;224
11.1;11 Molecular Grids and Computers;226
11.1.1;Overview;226
11.1.2;The Essentials of a Computer;226
11.1.2.1;Transistors;227
11.1.2.2;Diodes and Triodes;227
11.1.3;THE Neuron as The Chip;229
11.1.3.1;‘Bio-electrical Supply’;230
11.1.3.2;‘Biological Transistor’;230
11.1.3.3;‘Biological Chips’;231
11.1.3.4;RAM and STM;231
11.1.3.5;Input/Output Devices;231
11.1.4;Some Highlights in the Comparison;232
11.1.4.1;Processing Speed and Memory Capacity;232
11.1.4.2;Artificial Intelligence: Do Computers Surpass Human Brain?;232
12;References;234
13;Glossary;236
14;Index;240

Leseproben

Introduction
What is ‘The Biology of Thought’?
The human brain is the thinking organ, and neurons are its fundamental units. The myriad thoughts emanating from the magnificent human brain, minute after minute, are the products of the functioning neurons – and therefore we can say that neurons are the thinking machinery of the brain. However, it is still a puzzle how these neurons are designed to produce cascades of thoughts and can store them up in seemingly endless memory – all we know is that the sensations we receive from the outside world leave some sort of molecular signatures inside our brains that are imprinted in some form for future retrieval. What are these molecular signatures, and how are they made? How are these memory traces stored in the neurons? Our present science has no comprehensive answer – not yet. The question of ‘what is thought’ is almost as ancient as human civilization. Thought is an abstract phenomenon occurring in the human brain. Thoughts underlie all human actions and interactions, and they make up the core of human mind and the background of human consciousness. The idea of ‘thought’ may mean so many different things to each of us. We have thoughts of material things such as flowers and mountains; or we may think of such abstract things such as the beauty of nature, solution to a problem, principle of a theory, etc.; or we have thoughts related to the past or future, and so on. These mental processes are so varied and diverse that it is impossible to group all these thoughts into a single definition. And all these thoughts are complex cerebral events requiring several areas of the brain operating together to produce coherent ideas. However, we are not concerned with such complex thoughts here in this work. ‘Thought’, in this book, means the most fundamental unit of mental processes happening in the brain. This work is concerned with the generation of the most basic unit of thought right at the level of neurons. There is no current theory in modern neuroscience as to how a stimulus from the external world is converted into a perception in the brain. Clearly, the human brain has some mechanism for this conversion. For example, we can perceive the color blue only when we are capable of converting the color blue we receive from the external world into internal thoughts of blue color in the brain. On the other hand, we fail to perceive ultraviolet light (or infrared rays, for that matter) because we do not possess the necessary mechanism to convert the UV light wavelengths into internal signals (as bats and butterflies do). Where is this mechanism located in the neurons? And how does this mechanism function? These questions are left unexplored and unanswered by modern science, and thus have remained a mystery until now. This book, The Biology of Thought, is about the mechanism by which thought is generated and stored in the human brain. It describes a new molecular model by which thought is generated at the micro level in the human brain – right at the level of neurons. This work demonstrates how the biological electrochemical events occurring at the neuron interact with its molecular mechanisms to generate thoughts. In other words, here we have laid biological foundations for the generation of thought, hence the title of this book, The Biology of Thought. Thus, the hitherto abstract thought is shown to have a solid physical origin in the neuron, and this is showcased in a hypothesis called the ‘Molecular-grid Model’. How is This Book Organized?
Now we can see that to study such a complex issue as the generation of thought in the brain, the reader must have an overall idea of the anatomical and functional aspects of the brain to assist him/her to fully understand the mechanism. For easy sailing, the book is presented in four parts. Part I (Basic Concepts in Neurobiology). Part I of the book consists of three chapters which gives us some basic information on the structure of the brain and its functioning. Chapter 1 deals with the general plan of the human nervous system and the anatomy of the brain. Chapter 2 deals with the functioning of neurons – all the complicated electrochemical events occurring in a neuron are discussed in a simple and lucid way so that even a non-physiologist can grasp the electrical properties of neurons. Chapter 3 discusses the phenomenon of memory – the current concepts of the formation of memory along with the molecular basis of its storage are described briefly. Part I is obviously meant for those readers who want to brush up their knowledge on these basic concepts of the brain; however, this discussion may also interest a neuro-academic, because the presentation is a little out of the ordinary, to suit the purpose of the book. Part II (The Molecular-Grid Model). This part of the book deals with the crux of the problem of the generation of thought by neurons. It consists of five chapters which attempt to answer the following three questions: 1. What is the fundamental unit of thought? 2. Where is it generated in the neurons? 3. How is it generated? The sensory receptors sense various stimuli from the external world and send them up to the neurons in the brain, where they are converted into perceptions. This initial step generates the most fundamental units of thought in the neurons. Chapter 4 examines these fundamental units of thought (called the ‘primary thoughts’), and describes the properties of these primary thoughts. In Chapter 5 it is shown conclusively that only certain types of sensory neurons are designed to convert the external stimuli into primary thoughts (thus introducing the concept of ‘perceptual neurons’). In Chapter 6 it is shown that neurons have a certain molecular mechanism to receive the external stimuli and convert them into primary thoughts. A scientific discussion is undertaken to study the precise location of these molecular gadgets in the neurons. Chapter 7 examines the structure of these molecular gadgets (now called the molecular grids) and shows how they operate to generate primary thoughts. Chapters 4–7 take all the well-established concepts in neuroscience and show them in a new light, which helps us reach some far-reaching conclusions – and this can finally lead us to the concept of the molecular-grid model. Having proposed a working model for the generation of thought by the neurons, we should now see how it works – now the molecular-grid model has to pass the acid test. As with any good scientific model, it must be able to explain at least a majority (if not all) of the concerned phenomena, and thus our new model must now explain the most obvious phenomenon of the brain, that is the phenomenon of memory. Therefore, Chapter 8 applies the molecular-grid model to explain the molecular basis of memory and its storage – and alongside, also explains other equally intriguing features of the brain, such as forgetfulness, intelligence, and such others. Part II is the work-book of a theoretical scientist – because it consists of all the new concepts in the field of neuroscience, which can open new vistas in the field of neuroscience. Throughout Part II, thought is dealt with as an electrochemical process – i.e., a stimulus traveling to the neurons, exciting them electrochemically and generating primary thoughts. But it should be pointed out to the reader that the phenomenon of thought is far more elusive. We have seen, in the preceding chapters, only a physical mechanism by which thoughts are generated, but we have studied nothing about mind and consciousness or about the exact nature of thought itself. Part III (The Evolution of Human Mind). The human mind is not a single entity but has many varied aspects – such as perceptions, cognition, memory, reasoning, emotions, desires, etc. Likewise, consciousness is also a vague phenomenon. Historically, mind and consciousness have eluded a precise definition, mostly because they cannot be examined by a strict scientific method. Part III consists of two chapters. Chapter 9 engages the reader in a scientific discussion of mind and consciousness, and arrives at important definitions. Alongside, we also examine intriguing aspects of the human mind, like intelligence and emotions. Chapter 10 treats thought as a metaphysical entity (in contrast to the electrochemical process described in Part II). The ambiguous issues dealt with here are very complex; however, we will deal with them in a stepwise fashion to unravel the mystery of thought, and we approach these philosophical aspects of thought in a strictly scientific manner (or, at least, as strictly as abstract philosophical thought allows). At the end, we will examine the perplexing metaphysical conundrum that has bothered philosophers for ages – the mind-and-matter problem – and see how the molecular grids become relevant in this discussion. The philosophical presentation in Chapter 10 may appear a little out-of-place to a student of biology, but even a pragmatic biologist who studies human thought dispassionately must be aware of these hard questions to remind him/her of the limitations of human knowledge. And biologists must also realize that there are a lot of loose ends in the fabric of our knowledge in the field of...