Glossary

Action potential A brief regenerative, all-or-nothing electrical potential that propagates along an axon.

Afferents Axons conducting impulses towards the central nervous system.

Anion A negative ion, such as Cl-.

Anode A positive pole, to which an anion is attracted.

Antidromic Descriptive of an impulse that travels from axon terminals to­wards the neuronal soma, i.e. opposite to the usual (orthodromic) direction.

Arachnoid See Cerebrospinal fluid.

Arborization The branching of nerve fibres.

Astrocytes See Neuroglia.

Attention Concentration on some sensory experience.

Axon The process or processes of a neuron conducting impulses, usually over long distances.

Axon collateral A branch from the main axon.

Axon hillock The region of the cell body at which the axon originates; often the site of impulse initiation.

Basophillic Dark staining of nerve cells.

Bouton A small terminal expansion of the presynaptic nerve fibre at a synapse; the site of transmitter release.

Cable transmission Transmission of a potential charge along a nerve fibre in the manner of an electric current through a fibre and not as an impulse.

Catecholamine A synaptic transmitter substance. See Synaptic vesicles.

Cathode A negative pole, to which a cation is attracted.

Cation A positively charged ion, such as Na+, K+, or Ca2+.

186 Glossary

Caudal Towards the tailor posterior end (in humans the term is 'inferior').

Central nervous system (CNS) The brain and spinal cord.

Cerebellum The smaller (posterior) part of the brain lying behind the cerebrum and responsible for movement control.

Cerebral hemispheres The components of the cerebrum.

Cerebral ventricle A cavity (lumen) in the brain filled with cerebrospinal fluid.

Cerebrospinal fluid (CSF) A clear liquid filling the ventricles of the brain and spaces between meninges, arachnoid, and pia.

Cerebrum The principal (anterior) part of the brain.

Channel An opening or 'pore' in a membrane through which ions or molecules can move.

Cognitive experience A conscious thought or experience.

Conductance The reciprocal of electrical resistance and thus a measure of the ability of a circuit to conduct electricity.

Contralateral Relating to the opposite side of the body.

Convergence The coming together and making of synapses by a group of presynaptic neurons on one postsynaptic neuron.

Coronal section A vertical section through the skull at right angles to the front-back (sagittal) axis, i.e. a plane parallel to the face.

Corpus callosum The tract of nerve fibres that connects the cerebral hemi­spheres.

Cortical columns The aggregate of cortical neurons sharing common properties, e.g. sensory modality, receptive field position, eye dominance, orientation, movement sensitivity.

Decussation The intercrossing of similar structures.

Dendrite The process of a neuron specialized to act as a receptor; the postsynaptic region of a neuron.

Dendron A composite made by the bunching of the apical dendrites of pyramidal cells.

Depolarization The reduction of a membrane potential from the resting value towards zero.

Glossary 187

Divergence The branching of a neuron to form synapses with several other neurons.

Dorsal Pertaining to or situated near the back of an animal.

Efferent Axons conducting impulses outward from the central nervous system.

Electrochemical potential The voltage difference between two solutions insulated from each other; it is derived by the Nernst equation from the logarithmic relationship of the concentrations of the charged particles on either side of the insulating membrane.

Electroencephalogram (EEG) The record taken of the electrical activity of the brain by external electrodes on the scalp.

Electrotonic potentials Localized, graded potentials produced by sub­threshhold currents, determined by passive electrical properties of cells.

Encephalon The brain.

Ependymal cells A layer of cells lining the ventricles of the brain. See Neuroglia.

EPSP Excitatory postsynaptic potential in a neuron.

Equilibrium potential The membrane potential at which there is no net passive movement of an ion species into or out of a cell.

Excitation A process tending to produce action potentials.

Exocytosis A process whereby synaptic vesicles fuse with presynaptic ter­minal membrane and empty transmitter molecules into the synaptic cleft.

Facilitation Greater effectiveness of synaptic transmission by successive presynaptic impulses, usually owing to increased transmitter release.

Fasciculus A bundle of nerve fibres.

Folium Any of the leaf-like subdivisions of the cerebral cortex.

Fusiform Long, tapering at both ends.

Ganglion A collection of neurons that send and receive impulses; many in the autonomic system relay synaptically to the viscera.

Glia See Neuroglia.

Golgi type II neurons A short-axoned neuron with an axon that arborizes in dendrite-like fashion in the neighbourhood of the cell body.

188 Glossary

Grey matter Part of the central nervous system composed predominantly of the cell bodies of neurons and fine terminals, as opposed to major axon tracts (white matter).

Hippocampus A special primitive part of the cerebral cortex.

Hyperpolarization An increase in membrane potential from the resting value, tending to reduce excitability.

Impulse See Action potential.

Inhibition The effect of one neuron upon another tending to prevent it from initiating impulses. Postsynaptic inhibition is mediated through a per­meability change in the postsynaptic cell, holding the membrane potential away from threshold. Presynaptic inhibition is mediated by an inhibitory fibre upon an excitatory terminal, reducing the release of transmitter. Elec­trical inhibition is mediated by currents in presynaptic fibres that hyperpo­larize the postsynaptic cell and do not involve the secretion of a chemical transmitter.

Initial segment The region of an axon close to the cell body; often the site of impulse initiation.

Intention Concentration on a proposed movement.

Interneuron A neuron that is neither purely sensory nor motor but con­nects other neurons.

Ipsilateral On the same side of the body.

IPSP Inhibitory postsynaptic potential.

Mauthner cell A large nerve cell in the mesencephalon of fishes and amphibians, up to 1 mm in length.

Meninges Glial coverings of the brain.

MEPP Miniature end plate potential; a small depolarization at a neuro­muscular synapse caused by spontaneous release of a single quantum of transmitter from the presynaptic terminal.

Mesencephalon The lower medial part of the brain.

Modality The class of sensation (e.g. touch, vision, smell).

Motoneuron (motor neuron) A neuron that innervates muscle fibres.

Motor unit A single motoneuron and the muscle fibre it innervates.

Muscle spindle A fusiform end organ in skeletal muscle in which afferent sensory fibres and a few motoneurons terminate.

Glossary 189

Myelin The white substance of fused glia ensheathing nerve fibres.

Neocortex The most recently developed part of the cerebral cortex, com­posing the cerebral hemispheres.

Nerve fibre An axon (the principal branch from a nerve cell) that may extend for long distances.

Neuroglia, or glia Non-neuron satellite cells associated with neurons. In the mammalian central nervous system the main groupings are astrocytes and oligodendrocytes; in peripheral nerves the satellite cells are called Schwann cells.

Neuron (nerve cell) The biological unit of the brain and of the remainder of the nervous system.

Neuron theory The theory that the nervous system is composed of indi­vidual neurons that are biologically independent but communicate informa­tionally by synapses.

Node of Ranvier A localized area devoid of myelin occurring at intervals along a myelinated axon.

Noise Fluctuations in membrane potential or current due to random open­ing and closing of channels.

Nucleus A large basophillic mass, usually centrally placed within the cell body; it contains the DNA that provides the genetic instruction for the cell.

Oligodendrocytes See Neuroglia.

Orthodronic See Antidronic.

Paracrystalline Crystal-like arrangements of nerve-cell structures.

Pia A glial sheath.

Postsynaptic membrane The nerve cell or other receptor cell membrane immediately related to the synapse formed by presynaptic fibres ending on it.

Presynaptic fibres The terminal branches of nerve fibres that end as synap­tic knobs.

Presynaptic vesicular grid (PVG) The presynaptic structure formed of synaptic vesicles and dense projections.

Pyramidal cells The principal neurons of the cerebral cortex of pyramidal shape.

190 Glossary

Quantal release Secretion of multimolecular packets (quanta) of transmit­ter by the presynaptic nerve terminal.

Quantal size The number of molecules of neurotransmitter in a quantum.

Quantum content The number of quanta in a synaptic response.

rCBF Regional cerebral blood flow.

Receptive field The area of the periphery whose stimulation influences the firing of a neuron. For cells in the visual pathway the receptive field refers to an area on the retina whose illumination influences the activity of a neuron.

Receptor 1. A sensory nerve terminal. 2. A molecule in the cell membrane that combines with a specific chemical substance.

Resting potential The steady electrical potential across a membrane in the quiescent state.

Rostral Towards the rostrum or nose; thus, in the anterior direction in the central nervous system.

Sagittal section A section taken parallel to the anterior-posterior plane.

Saltatory conduction Conduction along a myelinated axon whereby the impulse leaps from node to node.

Sensorium The seat of sensation, located in the brain; it is often used to designate the condition of a subject relative to his or her consciousness or mental clarity.

Sensory modality The distinguishing names of all the various sensations arising from diverse inputs wth their specific receptor organs.

Seratonin A transmitter substance. See Synaptic vesicles.

Servomechanism A mechanism designed for feedback-control operation.

SMA Supplementary motor area.

Soma The cell body.

Striate cortex The primary visual region of the occipital lobe marked by striation of Gennari, visible wih the naked eye. (Also known as area 17 or visual!.)

Synapse Site at which neurons make functional contact; a term coined by Sherrington.

Glossary 191

Synaptic cleft The space between the membranes of the presynaptic and postsynaptic cells at a chemical synapse across which transmitter must dif­fuse.

Synaptic plasticity The property of synapses whereby they are changed in functional efficiency, probably by virtue of changes in size.

Synaptic vesicles Small membrane-bounded sacs contained in presynap­tic nerve terminals. Those with dense cores contain catecholamines and serotonin; clear vesicles are presumed to be the storage sites for other trans­mitters.

Threshold 1. The critical value of membrane potential or depolarization at which an impulse is initiated. 2. The minimal stimulus required for a sensation.

Transmitter A chemical substance liberated by a presynaptic nerve termi­nal causing an effect on the membrane of the postsynaptic cell, usually an increase in permeability to one or more ions.

Trophic influence An action from one part of a cell to another, or from one cell to another, that is concerned with the growth, maintenance, and metabolism of the cell.

Ventral Towards the under or belly side of the body.

Ventricles Cavities within the brain containing cerebrospinal fluid and lined by ependymal cells.

White matter Part of the central nervous system appearing white; con­sisting of myelinated fibre tracts.

Index

a rhythm 14 annulospiral endings 57 anticipatory evolution 122 apical dendrites (see dendrites) artificial intelligence-CAl) 176 attention 78, 173, 176 - mental act of 100 avian brain 123 axon terminal 130

binding problem 122, 178 biological naturalism 44 bird pallium 121 body-mind problem 45 bouton 55, pp 60, 130 - neocortical activity, bouton exocy­tosis 149 - quantal emission of 60 - quantal selection of bouton exocy-tosis 147 - synaptic 55, 62, 63 brain - brain-mind (see mind-brain) - and conscious experience 18, 81 - wonderful brain 181 bundles pp 93 - apical dendrites 95

Cartesina dualism 168 Cartesian theater 33 cerebral - cortex pp 87 - - basic receptive unit: the dendron 93 - - evolution and consciousness 118 - - mammalian pp 114, 122, 126 - - mind-brain interaction pp 87, 138, 139

- - neuronal composition 90 - - reptilian 119 - - silent thinking 78 - hemisphere, left 90 Changeux, IP 27 clusters 93 - apical dendrites 95 commissurotomy, forebrain 47 conpromissory materialism 168 conscious - existence as a self 179 - experience 11, 81 - - brain and conscious experience 18, 81 - will 162, 163 - world 167 consciousness pp 8, pp 28, 42, 45, 118 - accidentally 42 - by the action of its will 40 - cerebral evolution and conscious-ness 118 - Darwinist hypothesis for the origin of consciousness 123 - emergence of, evolution of complex­ity of the brain 125 - evolution of pp 113 - experienced in the brain 176 - fear of 45 - higher-order 35 - mammalian 122 - neurobiological theory 29 - primary 34 - quantum aspects of brain activity and the role of consciousness pp 143 - selected by evolution 37 - self conscious mind 22 - self consciousness 15, 89, 123, 139 - time delays 41

194 Index

cortical neurons, three-dimensional construct 94 Crick, F 29, 30

Darwinian evolution 139 Darwinist hypothesis for the origin of consciousness 123 death-awareness 19 deconvolution - analysis 65, 134 - techniques 65 dendrites, apical - bundles or clusters of 95 - of pyramidal cells 87 dendritic spine 62 dendron 74, 87, pp 95, 117, 131, 136, 140, 149 - basic receptive unit of the cerebral cortex 93 - dendron-psychon hypothesis 88, 107 - dendron-psychon linkage 178 - mental events, action of 104 - of neocortex, unitary linkage of met-al units to 10 1 - and psychons 88, 89 - - patterned relation between 88, 102 - - psychon-dendron game 176 - - psychon-dendron interactions 170 Dennett, DC 31 development noise 180 divine creation 180 drafts - locations, mUltiple 176 - theory, multiple 33 DSCT (dorso-spino-cerebellar tract) 152 dualism 38 - of Popper 46 - self-brain dualism - of world 1 and 2 dualist-interactionism 35, 67, 68, 89

167 168 3,4, pp 13,

- dualist belief of self and brain inter­action 168 - dualist-interactionist theory I-hypo­thesis 9, 76 - unitary hypothesis of 102

Edelman, G.M. 33 electromyogram 75 emission - quanta! 71 - probability 73 epiphenomenalism 3, 6, 10 EPSP (excitatory postsynaptic poten­tial) pp 58, 128, 152 - milli-excitatory 128 - monosynaptic 58 exocytosis 56, 57, 88, 114, pp 132, 140, 154 - neocortical acitvity, bouton exocy­tosis 149 - quantal selection of bouton exocy­tosis 147 - quantum mechanical model of exo­cytosis 154 - probability of 89, pp 134, 141, 158 - - momentarily increasing 160 - trigger process for 158, 163 - vesicle for 88 experiences 88 - they are the experiences 88 - conscious and brain 18, 81 - experience and delight 181 - experienced uniquess 180. - perceptual, unification of 109

femtosecond regime 158 forebrain - commissurotomy 47 - of reptiles 119

God - immanent - transcendent

180 180

Heisenbergs uncertainty relation higher-order consciousness 35 hippocampus 134 Hodgson, D 36

155

homo sapiens sapiens 167 how the self controls its brain human soul 180

181

hypothesis 81

identity - thesis - theory

66,89 3, 10, 89, 167

- - psychophysical 6 immanent God 180 insectivores 118 - insectivore neocortex 119 intracellular recordings 57

Koch, C 29, 30

left cerebral hemisphere 90 love 181

M-cell (Mauthner cell) pp 60, 65, 149 mammalian - cerebral cortex 114 - consciousness 122 - neocortex 126 Margenau, H. and quantum physics 23 materialism pp 7, 42 - history of 45 - materialist theories of mind 8, 66 - materialists 9, 23 - - challenge to all materialists 182 - promissory 7, 89 - radical 5 Mauthner cell pp 60 memory 81 mental - act of attention 100 - arithmetic 79 - events, unitary 101 - generation of neural events by men-tal events 137, 159 - influence 73, 81, 99 - intention 74, 103, 172 - operations 138 - units to dendrons of the neocortex 101 - world of psychons (world 2) pp 109 mind - materialist theories of 66 - mind, matter and quantum mech-anICS 52 - mind-brain (see there) - neurophysiological basis 15 mind-brain - brain-mind - - connection 50

Index 195

- - interaction 10, 80, pp 87, 117, 138, 139, 161 - - interface 51 - hypotheses 9, 14 - problem 2, 27, pp 55, pp 66, 80 - - introduction 66 - relationship 4 mindless 140 - living world 120, 125 - universe 181 momentarily increasing the prob­ability of exocytosis 160 monosynaptic EPSP 58 moral responsibility 171 morality 38 motoneuron, integrative action of Ia impulses 57 motor - area, supplementary (see also SMA) 67,74 - leaming 81 movement, voluntary 23, 163 multiple drafts - locations 176 - theory 33 myself 180

naturalism, biological 44 neocortex 87 - insectivore 119 - mammalian pp 126 - organization 131 - silent thinking 87 - unitary linkage of mental units to dendrons of the neocortex 101 neocortical activity, bouton exocytosis 149 neuronal - group selection, theory of (TNGS) 34, 122 - network 122 neurons - cortical, three-dimensional construct 94 - single SMA neurons 75 - and their synaptic connections 21, 92 neurophilosophy 27 neuroscience 17 noise, development 180

196 Index

panpsychism 3, 5, 8, 10 paths - not perceptual 88 paracrystalline - PVG (presynaptic vesicular grid) 55, 106, 154 - structure 63 Penrose, R 39 perception 16, 17, 108 - tactile 108 - theory of 89 person 38 personhood 35 PET (positron-emission tomography) 117, 159, 175 philosophical renaissance 18 Popper, KR, dualism of 46 probability 64, 65, 158 - of exocytosis 89, 141 - momentarily increasing the prob-ability of exocytosis 160 - quantum mechanics pp 71, 88 - of vesicular emission 64, 73 promissory materialism 7, 89, 168 propensity 157 psychon 87, 88, 101, 103, 108, 117, pp 135, 140 - dendron-psychon hypothesis 88, 107 - dendron-psychon linkage 178 - and dendrons, patterned relation be-tween 88, 102 - for mental intention 103 - mental world of psychons (world 2) 109 - not perceptual path 88 - psychon - - complex of the self 179 - - world 178 - psychon-dendron - - game 176 - - interactions 170 psychophysical identity theory 6 pure ideation 137 purpose 39 PVG (presynaptic vesicular grid) 55, 63, 64, 73, 76, 88, 103, 105, 117, 131, 140, 149 - paracrystalline 55, 105, 154 pyramidal - apical dendrites 87, 93

- cells 76 - tract 67, 68, 78

qualia 113, 118 quantal - emission - - of a bouton 60 - - of the synaptic transmitter mole-cules 71 - selection of bouton exocytosis 147 quantum - aspects of brain activity and the role of consciousness pp 145 - mechanical model of exocytosis 159 - mechanics 52 - - mechanical model 159, 163 - - probability fields 71, 72, 88 - physics 23, 130 - theory, brain-mind interface 51

radical materialism 5 rCBF pp 76 readiness potential 162 recordings, intracellular 57 religious beliefs 38 reptilian cerebral cortex 119 reticular - activating system 81 - formation 28

scanning technique 117 SchrOdinger equation 148, 156 Searle, JR 42, 44 self 15, 17, 38, 139, pp 168 - dualist belief of self and brain inter­action 168 - meaning of conscious existence as a self 179 - myself 180 - psychon complex of the self 179 - self-brain dualism 167 - self concious mind 21 - self consciousness 15, 89, 123, 139 silent thinking pp 78 - neocortex 78 SMA (supplementary motor area) 67, pp 74 - SMA cells, learned inventory of 77 - SMA neurons, single 75

soul 38 - human soul Sperry, RW

180 47,48

spine - dendritic 62 - synapse 87, 91, 104 Stapp, HP pp 50 SVs, spherical 131 synapses 55 - chemically transmitting synapse in eNS of vertrebrates 62 synaptic - boutons 55, 62, 63 - cleft 62 - monosynaptic EPSP 58 - presynaptic vesicular grid (PVG) 55, 63, 64, 73, 76, 88, 103, 105, 117, 131, 140, 149 - spine synapse 87, 91, 104 - transmitter molecules, quantal emission of 71 - ultrastructure 131 - vesicle 55, 62, 105, 131

tendency 157 TNGS (theory of neuronal group se­lection) 34, 122 transcendent God 180 transmitting areas 91 trigger process for exocytosis 158, 163

ultramicroproperties unitary hypothesis

vesicles 104 - for exocytosis 88

114 102, 109

- synaptic 55, 62, 105, 131 vesicular - emission, probability of 64 - grid, presynaptic 55, 63, 64, 73, 76, 88, 103, 105, 117, 131, 140, 149 voluntary movement 23, 163

wonderful brain 181 world - conscious world 167 - dualism of 168 - mindless 120, 125 - psychon world 178

Index 197

- world 1 3, 4, 56, 80, 89, 106 - - closedness of 67, 78 - world 2 3, 4, 56, 80, 87, 89, 106 - - mental world of psychons (world 2) 109 - world 3 4 wulst 121

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