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The Development of Neuropsychology (Localization of function -->…
The Development of Neuropsychology
Brain Theory: brain is the source of behavior & Neuron Theory: Unit of brain structure & function is the nerve cell
Neuron Theory
Descartes: nerves are fluid-containing tubes --> improvement of microscopes (cells are basic unit of nerves)
Staining Method: Golgi: visualizing entire neuron & its processes
Ramón y Cajal: drawings of neurons at different stages of growth
Galvani: how electrical conduction through the body might relate to the information flow in neurons
Fritsch & Hitzig: rabbit experiments showed that stimulating the cortex electrically produces movement
Sherrington: neurons are separated by junctions (synapses)
Loewi: chemicals carry the message across the synapse
Descartes: Dualism--> body = machine, role of the brain, pineal body as the site of action of the mind, mind-body problem
Contemporary: materialistic, neutral with respect to religion etc, scientific method, replication of earlier findings
Darwin: Materialism--> rational behavior can be explained by the workings of the NS, evolutionary theories, NS is an adaptation, epigenetics, neuroplasticity
Aristotle: Mentalism--> heart, non-material psyche
Localization of function --> Phrenology
Gall & Spurzheim: different parts of the brain have different functions
Cortex sends instructions to spinal cord to command muscles to move
two symmetrical hemispheres are connected by corpus callous (interact)
example: students with good memories had large eyes
personality analysis, individual differences
bumps: well-developed, greater capacity for a particular behavior
depressions: underdeveloped, reduced capacity
each trait assigned to a particular part of the skull
Cranioscopy
Limitations: characteristics such as faith, self-love are impossible to define & to quantify objectively, failed to recognise that superficial features on the skull reveal little about the underlying brain
Argument against: removing the cortex didn't eliminate any function completely but it seemed to reduce all functions somewhat
Lateralization of function (language) --> one cerebral hemisphere can perform a function not shared by the other
Paul Broca
Patient Tan: lost his speech, right side of his body was paralyzed, seemed intelligent, typical --> left frontal lobe
speech located only in the left hemisphere (if impaired: Broca's Aphasia)
Wernicke
1st model of how the brain produces language
temporal lobe aphasia/fluent aphasia: speak fluently but what they say makes little sense
Disconnection: although different brain regions have different functions, they are interdependent & must interact
Alexia: word blindness, disconnection between visual & Wernicke areas --> loss of the ability to read
Hierarchical Organisation
info is passed serially & organized as a functional hierarchy
higher level: control over more complex aspects of behavior (via lower levels)
Hughlings Jackson: NS has 3 levels: spinal cord, brainstem, forebrain
dissolution: opposite of evolution, damage to higher levels --> behavioral repertoire but behavior is simpler
Functions aren't represented in one location but are re-represented in neocortex, brainstem & spinal cord. Understanding a function requires understanding what each level of organization contributes to that behavior
Multiple Memory Systems
HM: removal of temporal lobes stopped epilepsy but induced amnesia
many neural structures encode memories separately & in parallel eg. neural structures for learning motor skills and those for remembering that one has those skills are separate
people encode different parts of the experience in different parts of the brain -> binding problem (nowhere in the brain do all aspects of the experience come together to form "memory" But we perceive a unified experience
Split Brain (Sperry)
each hemisphere has complementary self-awareness & social consciousness
Conscious/Unconscious Neural Streams
ventral (conscious) e.g.. visual form agnosia --> object identification
dorsal (unconscious) eg. ataxia --> guidance of action relative to objects
Conclusion: Vision (like language & memory) is not unitary and a lot is robotic & unconscious
Contributions from Allied Fields
Psychometrics & Statistical Evaluation: IQ measures --> for neuropsychology those are tools for measuring many aspects of brain function
Brain Imaging: allows rapid correlation between symptoms & brain pathology --> producing a functional atlas of the human brain (a task phrenology attempted but failed)
Neurosurgery: the surgeon would draw a map of a lesion to discover the exact extent of damage
Methods of measuring brain-behavior relationship
Experiments on animals --> Post mortem --> Lesion studies --> Split Brain --> Neuroimaging (in vivo)
Luria (father of modern NP assessment)
Antilocalization approach: elementary functions related to limited brain parts BUT higher mental functions are not localized (rather a "brain mass", general brain symptom)
it is impossible to relate a function to some limited part of the cortex or to conclude that its disturbance directly indicates lesion
any, especially higher function is a functional system based on the combined work of a dynamic structure --> cortical zones working together --> each time this functional system suffers in a unique way
a symptom might be of multiple significance and might have been evoked by damage in various locations
developed battery of NP tests during his clinical work with brain-injured victims of World War II
Principal research trends: linguistic aphasia, frontal lobe pathology, speech dysfunction, child neuropsychology