Index

From Aristotle to Sherrington, neuroscientific exploration of the nervous system's integrative action has primarily focused on motor functions, yielding significant insights into the roles of the spinal cord and cerebral cortex.

Over two millennia, prominent neuroscientists have grappled with prevailing philosophical frameworks, particularly Cartesian dualism, shaping their understanding of nervous system integration. Aristotle's concept of "psuche" as the life principle laid early biological foundations, describing souls hierarchically from basic nutritive functions in plants to rational faculties in humans. Galen further developed anatomical and functional distinctions between sensory and motor nerves, while the medieval ventricular doctrine localized cognitive functions incorrectly within brain ventricles.

Thomas Willis shifted focus decisively towards the cerebral cortex, pioneering concepts of cortical control over psychological and motor functions. Subsequently, researchers like Broca, Fritsch, and Hitzig provided concrete evidence of functional localization within the cortex, significantly advancing neuroscience.

Despite explicit modern rejections of Cartesian dualism by neuroscientists like Crick, Edelman, and Zeki, a subtle dualism persists, evident in attributing cognitive properties directly to the brain rather than to the whole person. Contemporary neuroscience now calls for abandoning these Cartesian frameworks, advocating holistic, embodied views of cognition and consciousness.

Aristotle’s conception of psuche

  • Historical Context:
    • Aristotle, the first great biologist, profoundly influenced early scientific thought.
    • His concept of psuche informed early neuroscientific theories despite his minimal anatomical knowledge.
  • Definition of Psuche:
    • Translated often as "soul," but without religious or ethical implications.
    • Originally meant "breath" or "life breath."
    • Aristotle used it biologically as "the principle of life," relevant to all living organisms, including plants.
  • Psuche as Form:
    • Aristotle distinguished between form (essence) and matter (substance capable of change).
    • Psuche is the form of a living body with life potential, representing its first actuality (potential capacity).
    • The form is inseparable from matter; neither exists without the other.
  • Types of Change:
    • Accidental Change: Non-essential attributes (e.g., growth, color change); the substance persists.
    • Substantial Change: Essential attributes change, leading to a new substance (e.g., death, milk becoming cheese).
  • Actualities (Entelechiai):
    • First actuality (unexercised power): E.g., having sight or knowing a language even when not actively using it.
    • Second actuality (active exercise): E.g., actively seeing or speaking.
    • Psuche represents first actuality: essential powers of a living creature.
  • Analogies for Understanding:
    • An axe: matter is wood and iron; form is the capacity to chop (its function).
    • An eye: matter is the organ itself; form is the power of sight. The soul similarly represents essential life functions.
  • Hierarchy of Souls:
    • Nutritive Soul: Fundamental to all life (growth, nutrition, reproduction); present in plants.
    • Sensitive Soul: Adds perception, desire, locomotion; characteristic of animals.
    • Rational Soul: Includes reasoning and rational will; unique to humans.
  • Non-Dualistic View:
    • The soul is not separate from or a part of the body but the functional essence.
    • Aristotle explicitly rejects dualism (contrast Plato and later Descartes).
    • To have a soul means being "en-souled" (empsuchos)—integrally alive.

Aristotle’s Conception of the Sensus Communis

  • Definition and Function:
    • Central sensory faculty coordinating distinct senses.
    • Unified perception despite separate sensory organs (eyes, ears, etc.).
  • Reasoning for Sensus Communis:
    • Explains common sensory attributes (shape, motion, number) detected by multiple senses.
    • Allows unified perception of objects with multiple sensory properties (color, taste, shape).
    • Responsible for awareness of perceiving (knowing that we see or hear).
    • Enables distinguishing qualities across different sensory modalities (e.g., white from sweet).
    • Coordinates sleep/wake states affecting all sensory faculties.
  • Functions Attributed to Sensus Communis:
    • Apprehension of time.
    • Imagination (image-formation).
    • Memory formation.
    • Dreaming.
  • Aristotle’s Physiological Misconception:
    • Identified the heart as the sensorium (central organ of sensory integration).
    • Misassigned the brain’s integrative functions to the heart.

Additional Notable Points

  • The "Fifth Element" (Aether):
    • Aristotle proposed a divine element distinct from earth, water, air, fire.
    • Linked "vital heat" (pneuma) present in semen, responsible for generation and muscular contraction.
  • Observation on Divided Insects:
    • Aristotle noted segmented insects maintain life functions temporarily after division.
    • Each segment momentarily retains sensory and motor capacities, indicating individual "segment souls," not a central master soul.
    • Relevant to later debates about distributed nervous system functions ("spinal soul" discussions in 18th-century neuroscience).

The Ventricular Doctrine: From Galen to Descartes

Galen: Motor and Sensory Centres

  • Historical context:
    • Aristotle’s conception modified by Galen (130–200 AD) based on anatomical observations.
    • Recognition that nerves from brain and spinal cord are essential for muscle contraction.
  • Vital and psychic pneuma theory:
    • Blood delivers vital pneuma to the brain.
    • Brain transforms vital pneuma into psychic pneuma, transmitted via nerves to muscles.
    • Psychic pneuma inflates muscles, causing contraction.
  • Galen’s motor nerve observations:
    • Motor nerves arise from spinal cord; voluntary movements below neck originate there.
    • Complete spinal cord transection results in loss of sensation and movement below lesion.
    • Partial cord transection (hemisection) results in ipsilateral paralysis.
  • Spinal cord and paralysis details:
    • Median longitudinal cord incision does not cause paralysis.
    • Damage at specific vertebral levels affects corresponding motor functions (respiration, voice).
  • Distinction between sensory and motor nerves:
    • Motor nerves: “hard,” from spinal cord, adapted for motion.
    • Sensory nerves: “soft,” from brain, adapted for sensation.
    • Mixed nerves originate between brain (soft nerves) and spinal cord (hard nerves).
  • Localization and nerve quality:
    • Lower spinal cord: hardest motor nerves.
    • Anterior brain: softest sensory nerves.
    • Intermediate regions: mixed nerves (motor and sensory).
  • Soul and psychological functions:
    • Galen adopted Aristotle’s conception of the soul (psuche), dividing functions into sensory and motor “souls.”
    • Sensory soul: senses (sight, hearing, touch, etc.).
    • Motor soul: responsible for muscular movement.
    • Rational functions (imagination, reason, memory) arise from principal faculty of soul.

Galen: Functional Localisation of Rational Soul

  • Brain substance and softness:
    • Brain’s softness seen as advantageous for sensory perception and imagination.
    • Anterior brain softer (for senses); posterior harder (for motor functions).
    • Separation between sensory and motor areas by the dura mater (tentorium cerebelli).
  • Ventricular localization of intellect:
    • Observations: damage to anterior brain affects face and intellect.
    • Intellectual functions linked specifically to lateral (anterior) ventricles.
  • Galen’s legacy:
    • Dominance for over a millennium.
    • Set stage for ventricular localization of higher cognitive functions.

Nemesius: Formal Ventricular Doctrine

  • Nemesius (~390 AD):
    • Expanded Galen’s doctrine explicitly assigning specific psychological functions to ventricles.
  • Ventricular function assignment:
    • Lateral ventricles: perception and imagination.
    • Middle ventricle: intellectual faculties (reasoning).
    • Posterior ventricle: memory.
  • Justification for ventricular theory:
    • Clinical observation: specific brain lesions produce specific deficits (e.g., front ventricles affect senses).
  • Nemesius’s soul conception:
    • Influenced by Christianity and neo-Platonism.
    • Soul viewed as separate, spiritual entity united temporarily with body.
    • Deviated from Aristotle by attributing psychological properties directly to the soul, not the whole organism (a conceptual error persisting in neuroscience today).

One Thousand Years of the Ventricular Doctrine

  • Influence across centuries:
    • Avicenna (980–1037 AD): detailed ventricular doctrine, assigned specific mental functions clearly to ventricles.
    • Quattrocento physicians (e.g., Antonio Guainerio) attributed memory loss to ventricular damage.
  • Leonardo da Vinci (1452–1519):
    • Accurate anatomical ventricular description.
    • Slight modification: moved perception from lateral ventricles to middle ventricles (sensory convergence).
  • Andreas Vesalius (1514–1564):
    • Provided detailed ventricular anatomy; questioned psychological functions assigned to ventricles.
    • Noted identical ventricular anatomy in humans and animals, challenging the intellectual localization theory.

Fernel: Origins of Neurophysiology

  • Jean Fernel (1495–1558):
    • Defined “physiology” formally as studying bodily processes and functions (1542).
    • Distinguished clearly between anatomy (structure) and physiology (function).
  • Reflex concept introduced:
    • Recognized involuntary muscular movements (eye, breathing) independent of conscious will.
    • Originated modern concept of reflexes, later advanced by Sherrington in 20th century.
  • Legacy of Fernel:
    • Physiology textbook influential for a century.
    • Replaced eventually by mechanistic explanations inspired by scientific revolution (Harvey, Descartes).

Descartes: The Beginning of the End for Ventricular Doctrine

  • René Descartes (1596–1650):
    • Revolutionized thinking about mind-body relationships.
    • Mind identified purely as consciousness, distinct from the body (dualism).
  • Key departures from Aristotelian-Scholastic tradition:
    • Mind defined as purely thinking substance; animal functions explained mechanically.
    • Extended mental attributes to encompass all conscious states (thought, sensation, imagination).
    • Conceived human being as union of two distinct substances (mind/body), not a single unified substance.
    • Matter defined solely by spatial extension (mechanistic physics).
  • Animal spirits theory:
    • Replaced Galen’s psychic pneuma with mechanical particles (animal spirits).
    • Animal spirits flow from ventricles via nerves to muscles, causing movement.
    • Reflex actions explained by mechanical operation of nerve valves.
  • Pineal gland as mind-body interface:
    • Located interaction site of mind and body in pineal gland (incorrectly placed within ventricles).
    • Chosen due to central location, singular nature, ideal for “uniting” sensory images.
  • Errors and conceptual confusions:
    • Confused perception with internal representation viewed by the soul (mereological fallacy).
    • Failed to account adequately for the similarities in pineal anatomy among mammals.
  • Contribution despite errors:
    • Emphasized mechanical and causal explanations in biology.
    • Initiated rejection of ventricular localization of higher cognitive functions.
    • Paved way for later cerebral cortex-centric theories (e.g., Willis).

Overall Summary:

  • Galen: Developed pneumatic theory, distinguished motor and sensory nerves; placed psychological faculties within ventricles.
  • Nemesius: Formalized full ventricular localization theory (perception, intellect, memory).
  • Middle Ages and Renaissance: Doctrine persisted with minimal changes (Avicenna, Leonardo, Vesalius).
  • Fernel: Originated concept of neurophysiology, reflexes independent of consciousness.
  • Descartes: Initiated major shift away from ventricular localization, introduced mechanical corpuscular explanation, identified pineal gland as mind-brain interaction point, paving way for future cerebral-centric theories.

This historical progression eventually set the stage for the cerebral doctrine that followed.

The Cortical Doctrine: from Willis to du Petit

Thomas Willis: Origins of Psychological Functions in the Cortex

Background and Context

  • Thomas Willis (1621–1675), Professor of Medicine at Oxford, significantly shifted thinking from ventricles to cortex.
  • Used clinical and post-mortem observations on neurological patients to study brain functions.
  • Willis's key works:
    • Cerebri Anatome (1664)
    • De Anima Brutorum (1672)
  • His anatomical descriptions were greatly enhanced by illustrations by Christopher Wren.

Willis's Fundamental Theories

  • Psychological attributes depend on the cerebral cortex, not the ventricles.
  • First to propose cortical control of musculature and reflex actions.
  • Concept of two types of "spirits":
    • Vital spirits: derived from blood (in heart and vessels).
    • Animal spirits: distilled from vital spirits in the brain.

Corporeal Soul

  • Willis distinguished two types of souls:
    • Arises naturally with the body.
    • Diffused throughout body parts, crucial for bodily functions.
    • Corporeal Soul (material): present in both humans and animals ("brutes").
    • Rational Soul (immaterial): unique to humans, immortal, responsible for volitional acts.

Mechanism of Animal Spirits

  • Animal spirits generated in cortex and cerebellum from vital spirits.
  • Flow from cortex down through brainstem and spinal cord into nerves and finally muscles.
  • Muscular activation occurs due to flow of animal spirits.

Reflex Actions Explained by Willis

  • Sensory stimulation:
    • Causes inward movement of animal spirits from sensory organs.
    • If the stimulus is strong, spirits propagate through brain structures (corpus striatum, corpus callosum), engaging imagination or memory.
    • Reflected back from cortex into nerves, producing muscular movement (reflex arc).
  • In animals, movements considered entirely reflexive; humans also capable of voluntary movements.

Role of the Rational Soul

  • Rational Soul perceives sensory images formed in brain (specifically corpus callosum).
  • Sensory impressions travel via animal spirits along nerves, forming images within brain regions.
  • Rational Soul "observes" these internal images, leading to volitional acts.

Willis's Neuroanatomical Contributions

  • Convolutions (gyri) of cortex:
    • Important for memory and imagination.
    • Greater complexity of gyri in humans explained by superior psychological capabilities.
  • Cortical substance (grey matter): production of animal spirits.
  • Medullary substance (white matter): distribution and conduction of animal spirits.

Interaction Problem (Mind-Body Issue)

  • Willis adopted Cartesian dualism (mind immaterial, body material).
  • Located the Rational Soul in corpus callosum (contrast with Descartes’s pineal gland).
  • Struggled with explaining the interaction between immaterial Rational Soul and material Corporeal Soul.

The Cortex 100 years after Willis

Continued Search for Functional Localization

  • Little advancement in cortical localization for about a century after Willis.
  • The late 18th century still seeking localization of the sensorium commune (common sensory center) in brain.
  • Prochaska (1784) localized mental processes in cerebrum and cerebellum, and sensorium commune in spinal cord and brainstem (little advancement from Willis).

Discovery of Decussation (Crossing of Nerves)

  • Domenico Mistichelli (1709):
    • Observed and illustrated decussation (crossing) of nerve fibers at the medulla-spinal junction.
    • Noted nerves on one side originate from opposite side in brainstem/spinal cord.
  • François Pourfour du Petit (1727):
    • Detailed tracing of pyramidal fibers from cortex through brainstem.
    • Identified motor cortex origins, passing through pyramids, crossing at medulla (decussation of pyramids).
    • Observed contralateral motor paralysis due to cortical injury.
    • Provided earliest explicit description of pyramidal (corticospinal) motor pathway.

The Spinal Soul, Spinal Sensorium Commune, and Reflex Concept

Early Understanding of Spinal Reflexes

  • Alexander Stuart (1739):
    • Showed spinal cord could mediate movement independent of brain.
    • Movement due to "animal spirits" displaced into muscles from spinal cord upon mechanical stimulation.
  • Robert Whytt (1751)
    • Described continued movement of decapitated animals (frogs, tortoises) attributed to a "sentient principle" (still considered spinal soul necessary for reflexes).
    • Identified early stretch reflex.
  • Jiri Prochaska (1784)
    • Proposed concept of sensorium commune extended to spinal cord, responsible for reflexes (unconscious).
  • Luigi Galvani (1791)
    • Demonstrated nerve conduction via electricity, eliminating the need for fluid "animal spirits."

Bell-Magendie Law (Differentiation of Spinal Roots)

  • Charles Bell (1811):
    • Demonstrated anterior roots of spinal nerves as motor.
  • François Magendie (1822):
    • Established posterior roots as sensory.
    • Confirmed Bell-Magendie Law: anterior roots motor, posterior roots sensory.

Marshall Hall and Reflex Action (1830s)

  • Hall clearly differentiated reflex action from sensation:
    • Reflexes mediated by spinal cord independent of brain, sensation, or volition.
  • Concept of "true spinal marrow"—solely reflexive:
    • Reflex arc: sensory nerve → spinal cord → motor nerve.
    • No sensation or volition needed, purely mechanical reflex activity.

Further Implications and Refinements

  • Müller (1831), Bernard (1858), and Vulpian (1866) supported mechanistic reflex theory.
  • Sechenov (1863):
    • Extended reflex theory to brain: proposed that all behaviors, including emotions and reasoning, are forms of reflex action mediated mechanically in brain and spinal cord.
  • Pavlov (1907):
    • Experimental demonstration of "psychic" (conditioned) reflexes supporting Sechenov's views.

Key Historical Shifts

  • From ventricles to cortex (Willis).
  • Mechanical understanding of nervous system (Marshall Hall, Galvani).
  • Distinction between sensory and motor pathways (Bell-Magendie).
  • Reflex theory and extension to higher brain functions (Hall, Sechenov, Pavlov).

These shifts profoundly influenced our modern understanding of nervous system integration and the mechanical basis of behavior.

Localisation of Function in the Cortex

Broca: Cortical Area for Language

  • Paul Broca (1824–1880) identified the first clear evidence of cortical specialisation in 1861.
  • Observed patient, Monsieur Leborgne ("Tan"), who exhibited aphasia (loss of speech).
  • Autopsy revealed a lesion in the left anterior frontal lobe.
  • Broca identified this as the cortical region responsible for language.
  • This area is now known as Broca’s area.

Fritsch and Hitzig: The Motor Cortex

Historical Context (pre-1870)

  • Limited understanding of cortical function between Thomas Willis’s death (1675) and 1870.
  • French physiologist Marie-Jean-Pierre Flourens (1794–1867) claimed:
    • Cortex responsible only for perception, intellectual abilities, and volition, not motor action.
    • Functions of the cortex were holistic, not localised.
    • Demonstrated (1858) respiratory motor control in the medulla, independent of the cortex.

Experiments of Fritsch and Hitzig (1870)

  • Gustav Fritsch (1838–1927) and Edouard Hitzig (1838–1907) conducted experiments published in Über die elektrische Erregbarkeit des Grosshirns, Conducted electrical stimulation experiments on exposed dog cortex with weak galvanic currents.
  • Key findings:
    • Identified discrete cortical areas eliciting muscle contractions in the opposite side of the body (face, neck, forepaw movements).
    • Unilateral removal (ablation) of motor areas impaired motor activity and posture, but not sensory perception.
  • Conclusion:
    • Cortex has distinct motor and non-motor areas (motor anteriorly located).
    • Introduced the concept of localisation of cortical functions.
    • Suggested psychological functions might similarly be localised in specific cortical areas.

Contributions of John Hughlings Jackson (1863 onwards)

  • Clinical observations on human epilepsy cases supported Fritsch and Hitzig’s findings.
  • Identified that epileptic convulsions typically affected the body side opposite cortical lesions.
  • Suggested motor cortex is organised somatotopically:
    • Areas controlling hand, face, and foot have the largest cortical representation due to specialised movements.

Confirmation by David Ferrier (1874)

  • David Ferrier (1843–1928) extended research to primates using alternating current stimulation.
  • Precisely mapped cortical regions responsible for specific movements.
  • Lesions to specific cortical regions caused paralysis of corresponding body parts (e.g., hand, forearm, biceps).
  • Confirmed somatotopic organisation of motor cortex.

Work of Victor Horsley (1887 onwards)

  • Confirmed precentral gyrus predominantly motor, postcentral gyrus predominantly sensory.
  • Defined motor cortex anteriorly positioned relative to Rolandic fissure.

Electrical Phenomena Supporting Motor Cortex Theory

  • Richard Caton (1875) discovered:
    • Cortical electrical oscillations could be recorded with surface electrodes in monkeys.
    • Oscillations altered by sensory input, anoxia, and anaesthesia.
    • Motor cortical regions (identified by Ferrier) showed electrical activity correlating with specific motor actions.
  • Confirmed later by Adolf Beck (1890), who provided further experimental evidence supporting localisation.

Challenges to Motor Cortex Localisation

Fredrich Goltz's Critique (1881)

  • Fredrich Goltz (1834–1902) challenged localisation theory at the Medical Congress, London (1881).
  • Presented dogs with cortical lesions but without significantly impaired motor function.
  • Suggested motor localisation findings (Fritsch, Hitzig, Ferrier) might be incorrect or exaggerated.

Resolution and Histological Examination

  • To validate Goltz’s lesions, dog brain tissue provided for histological examination to researchers.
  • J.N. Langley and Charles Sherrington (1883–1884) examined cortical lesions.
    • Led Sherrington to collaborate and study with Goltz.
    • Marked the beginning of Sherrington’s extensive contributions to cortical physiology.

Summary of Key Contributions to Cortical Localisation:

  • Broca (1861) – Language localisation in frontal cortex.
  • Fritsch & Hitzig (1870) – Motor cortex defined through electrical stimulation.
  • Jackson (1863 onwards) – Clinical confirmation of somatotopically organised motor cortex.
  • Ferrier (1874) – Detailed mapping and confirmation in primates.
  • Caton (1875) and Beck (1890) – Electrophysiological support of cortical localisation.
  • Goltz (1881) – Critical experimental challenge to the localisation concept.
  • Langley & Sherrington (1884) – Initiated further detailed research, reinforcing localisation theory.

Charles Scott Sherrington: The Integrative Action of Synapses in Spinal Cord and Cortex

The Integrative Action of Synapses in the Spinal Cord

Overview

  • Charles Sherrington (1857–1952) was pivotal in systematically elucidating spinal cord functions.
  • Known for exceptional methodological rigor, clarity, and extensive experimentation.
  • His insights were based on precise experimental studies rather than technical innovations alone.

Key Experimental Findings:

  • Distribution of motor neurons: Sherrington (1892) demonstrated motor neurons controlling one skeletal muscle are scattered across the spinal segments responsible for that muscle.
  • Independent muscle contraction:
    • 1905 experiments showed stimulating afferent nerves from a muscle can trigger muscle contraction without simultaneous antagonist muscle activation.
  • Detailed reflex studies (1910 seminal paper):
    • Examined flexion-reflex (nociceptive reflex), extension-reflex, and crossed-extension reflex.
    • Flexion-reflex primarily protective, triggered by nocuous stimuli; can also be elicited by proprioceptive stimuli (passive limb movements).
    • Crossed-extension reflex: stimulation causing flexion in one limb often triggers extension in contralateral limb.
    • Established stepping reflex without direct ground contact, emphasizing rhythmic, coordinated alternating limb movements, and described its spinal basis.
    • Identified reflex standing as a spinal reflex post-midbrain transection, involving tonic muscular contraction of extensor muscles and inhibition of antagonist muscles, providing posture stabilization during movements like walking and running.
  • Concluded a conceptual framework initially suggested by Marshall Hall (1830), fully discarding the obsolete notion of a "spinal soul."

Major Principles Established by Sherrington:

  • Scratch Reflex:
    • Observed after cervical spinal cord transection in dogs.
    • Rhythmic, alternating hind-limb flexion-extension triggered by mechanical stimuli (tickling, hair pulling) within a defined dorsal skin area.
  • Concept of Inhibition:
    • Introduced spinal cord inhibition as central phenomenon.
    • Single afferent fibers have dual roles, excitatory and inhibitory, via branching terminals—termed "duplex centrally."
  • Final Common Pathway:
    • Proposed that motor neurons form a "final common pathway," passively controlled by diverse reflex arcs.
    • Illustrated through scratch reflex studies demonstrating mutual reinforcement of subthreshold stimuli from different receptive skin areas, emphasizing summation and reinforcement at spinal level.
  • Relation between Brain and Spinal Reflexes:
    • Suggested reflex neutrality (independence) observed in spinal animals does not exist when brain and higher pathways are intact.
    • Brain provides extensive integration ("crowning contribution") linking reflexes across different body parts into coherent responses.

Sherrington: Somatotopic Mapping of the Motor Cortex

  • Following Ferrier's initial identification of the primate motor cortex (1886), Sherrington and Grunbaum (1902) provided detailed somatotopic mapping of the primate motor cortex.
  • Key Contributions:
    • Precisely delineated the "motor area" of the cortex anterior to the central sulcus, clearly distinguishing it from posterior sensory regions.
    • Highlighted that motor cortex stimulation reliably triggered motor responses, while areas behind the central sulcus produced ambiguous responses.
  • Detailed Findings:
    • Frontal Eye Fields: Identified frontal cortical region causing conjugate eye movements, distinct from main motor area and separated spatially by a zone of non-responsiveness.
    • Advanced cortical stimulation methods (unipolar faradisation) allowed precise localization, surpassing previous double-electrode techniques.
  • Identified Motor Functions in Cortex:
    • Observed detailed somatotopy of specific body movements, including:
    • Movements of ears, nostrils, palate, vocal cords, mastication, sucking, chest and abdominal wall contractions, and pelvic muscle control.
    • Established clear segmental organization, matching craniospinal nerve distribution.
  • Impact and Legacy:
    • Sherrington's work definitively confirmed functional specialization in different cortical areas, laying foundational concepts in neurophysiology.
    • Established modern understanding of spinal and cortical integration mechanisms essential for coordinated motor behavior.

Charles Sherrington (1857–1952)

  • Research Contribution:
    • Clarified spinal cord reflexes and cortical localization of functions.
    • Addressed historical ideas from Aristotle and Jean Fernel, attempting to contextualize the mind-body relationship.
  • Mind-Cortex Relationship:
    • Initially acknowledged Aristotle’s view on the unity of body and mind but misunderstood its implications.
    • Gravitation towards Cartesian dualism:
    • Distinguished between 'energy' (matter/brain) and 'psyche' (mind) as separate categories.
    • Conceived mind as intangible, invisible, and distinct from energy.
    • Believed mind and brain interact but admitted uncertainty about how this occurs.
  • Philosophical Confusions:
    • Erroneously treated the mind as a tangible entity capable of causal interactions.
    • Confused conceptual distinctions (mind-body-person relationships), leading to insoluble dualistic puzzles.
    • Acknowledged philosophical difficulty without fully recognizing his conceptual confusions.

Edgar Adrian (1889–1977)

  • Research Contribution:
    • Shared Nobel Prize with Sherrington (1932).
    • Established the electrical basis of nerve signals (action potentials).
    • Identified brain rhythms (e.g., Berger rhythm).
  • Mind-Brain Views:
    • Avoided firm commitments on dualism; acknowledged mind-brain issues but hesitant to theorize.
    • Emphasized introspection as crucial for understanding self-consciousness and identity.
    • Inclined towards Cartesian view of consciousness as distinguishing humans from machines.
    • Believed scientific and introspective accounts of mind would eventually converge.

John C. Eccles (1903–1997)

  • Research Contribution:
    • Student and collaborator of Sherrington; focused on synaptic transmission and brain physiology.
    • Intracellular recordings revealed precise neuronal activities underlying reflexes and synaptic integration.
  • Mind-Brain Views:
    • World 1: Material objects (including brains)
    • World 2: Mental states
    • World 3: Abstract entities (e.g., propositions)
    • Embraced explicit dualist-interactionism, heavily influenced by Popper’s "Three Worlds":
  • Argued empirical support for dualism based on:
    • Kornhuber's readiness potentials preceding voluntary movements.
    • Sperry’s split-brain research, suggesting hemispheric specialization linked to self-consciousness.
    • Proposed "liaison brain" theory, claiming mind scans neuronal activity, actively selecting and integrating brain modules to achieve conscious unity.
  • Philosophical Errors:
    • Misconceived mind as a causal entity interacting with the brain.
    • Problematic attribution of conscious decisions and awareness directly to the mind, separate from the person.
    • Failed to resolve fundamental interactionist dilemmas (e.g., how mind could selectively control neural mechanisms).

Wilder Penfield (1891–1976)

  • Research Contribution:
    • Student of Sherrington; pioneer in neurosurgical techniques for epilepsy.
    • Discovered cortical localization of functions, notably sensory, motor, speech, and memory areas.
    • Identified temporal lobe and hippocampal roles in memory.
  • Mind-Brain Views:
    • Observed epileptic automatisms, interpreting them as brain functioning independently from a "mind."
    • Stimulation experiments showed patients could differentiate voluntary actions from those electrically induced, leading Penfield to conclude volition is mind-driven.
    • Proposed "highest brain mechanism" as interface between mind and brain, suggesting a non-neuronal energy form might mediate interaction.
    • Initially aimed to explain the mind entirely by neuronal activity.
    • Late career led to dualistic conclusions:
  • Philosophical Confusions:
    • Mistakenly treated the mind as a separate causal entity that programs or directs brain activities.
    • Erroneously believed choice between dualism or neural explanations for the mind was empirical.
    • Overlooked conceptual clarification that psychological attributes belong to persons, not to minds or brains.

Dualist conceptions - current relevance

  • Sherrington, Adrian, Eccles, and Penfield were each influenced by dualist conceptions of the mind-brain relationship, particularly Cartesian dualism.
  • Common errors:
    • Treating the mind as a causal substance, separate from the person.
    • Misunderstanding the mind’s conceptual (not empirical) nature.
    • Conflating empirical (scientific) and conceptual (philosophical) questions regarding mind-brain relations.
  • Proper philosophical stance:
    • Mind should be understood not as an entity, but as an array of abilities or capacities (following an Aristotelian perspective).
    • Psychological attributes (thinking, deciding, believing) belong to persons, not brains or independent minds.
    • The mind-brain interaction problem arises from conceptual confusion, not empirical ignorance.
  • Contemporary Neuroscience Relevance:
    • Current neuroscientists should avoid ascribing psychological functions directly to brains (common error today).
    • Proper conceptual clarification remains necessary to address fundamental issues in neuroscience and philosophy of mind.

In the shadow of Descartes

  • Charles Sherrington and his contemporaries struggled with understanding cortical functions within the Cartesian dualistic framework.
  • Modern neuroscientists (e.g., Blakemore, Crick, Damasio, Edelman, Libet, Young, Zeki) explicitly reject Cartesian dualism, claiming liberation from Descartes's philosophical legacy.
  • Despite explicit rejection, contemporary neuroscientists remain subtly influenced by Cartesian thinking.

Persistence of Cartesian Influence

  • Contemporary neuroscientists reject Descartes's notion of an immaterial mind interacting with a material body.
  • Instead, they replace the immaterial "mind" with the material "brain," explaining psychological functions purely through neural processes.
  • However, this replacement inadvertently perpetuates a form of Cartesian dualism, substituting a "mind/body" dualism with a "brain/body" dualism.
  • The dualism persists logically rather than substantively, maintaining Cartesian conceptual structures.

Dualism in Contemporary Neuroscience (Brain/Body Dualism)

  • Current neuroscience attributes psychological properties traditionally ascribed by Descartes to the "mind," now to the "brain."
    • Descartes: mind perceives, thinks, wills, feels emotions.
    • Modern neuroscience: brain perceives, thinks, decides, remembers, feels emotions.
  • Psychological attributes are thus assigned directly to the brain rather than to the whole person.

Examples from Modern Neuroscientists

  • Crick: Explains visual perception as "brain's beliefs, guesses, interpretations."
  • Edelman: Brain "manipulates rules," "forms concepts," categorizes activities.
  • Blakemore: Brain "knows," "reasons inductively," "constructs hypotheses."
  • Young: Brain "poses questions," "constructs hypotheses."
  • These attributions parallel Cartesian descriptions of mind functions, now transferred to the brain.

The Mereological Fallacy

  • "Mereological Fallacy": Logical error of attributing properties to a part (brain/mind) that can logically belong only to the whole (person).
  • Examples of Mereological Fallacy:
    • Incorrect: "Mind feels pain," "brain knows," "brain believes."
    • Correct: "Person feels pain," "person knows," "person believes."
  • Psychological experiences (pain, perception, thinking, reasoning, remembering) belong to human beings, not isolated parts like mind or brain.

Mistaken Attribution to Brain vs. Person

  • Errors of attribution by neuroscientists:
    • Blakemore: brain "knows."
    • Crick: brain "believes," "interprets."
    • Young: brain "constructs hypotheses."
    • Gregory: brain "makes logical decisions."
  • Such psychological attributes correctly apply only to living, conscious persons or animals, not isolated brains.

Consequences of the Cartesian Legacy

  • Cartesian influence leads to ongoing confusion and mystification around consciousness.
  • Descartes redefined the mental explicitly in terms of consciousness, leading contemporary neuroscientists into a persistent struggle to explain consciousness itself.
  • Modern neuroscience views consciousness as an epiphenomenon or mysterious accompaniment of brain activity, reflecting unresolved Cartesian thinking.

Need for Radical Break from Cartesianism

  • To resolve contemporary issues (e.g., the mystery of consciousness), neuroscientists must abandon Cartesian conceptual structures more thoroughly.
  • Overcoming the mereological fallacy requires a shift toward attributing psychological phenomena to the holistic, embodied human being rather than isolated components (brain).

Conclusion

  • Despite explicit rejection, contemporary cognitive neuroscience remains deeply influenced by Cartesian philosophical frameworks.
  • True liberation from Cartesian thinking necessitates a conceptual revolution beyond substituting "mind" with "brain," embracing holistic, non-dualistic conceptions of human nature and psychological processes.

Cover image: The School of Athens fresco created between 1509 and 1511 by the Italian Renaissance painter Raffaello Sanzio, located in the Stanza della Segnatura, one of the four “Vatican Rooms”, located inside the Apostolic Palaces. In the Center, we can find Plato and Aristotle. On the left with the green dress explaining his truth, there is Socrates.