Flexor-
Download
1 / 61

Flexor- Crossed Extensor Reflex Sheridan 1900 - PowerPoint PPT Presentation


  • 828 Views
  • Updated On :

Flexor- Crossed Extensor Reflex (Sheridan 1900). Reflex Circuits With Inter-neurons. Painful Stimulus. A Simple model or Minimum Circuit:. HIGHER LEVEL CONTROL. Pain Stimulus. MotoNeuron. +. +. +. Sensory Neuron. Inter Neuron. Inter Neuron. Flexor. MotoNeuron. -. -.

Related searches for Flexor- Crossed Extensor Reflex Sheridan 1900

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Flexor- Crossed Extensor Reflex Sheridan 1900' - albin


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Flexor-

Crossed

Extensor

Reflex

(Sheridan

1900)

Reflex

Circuits

With

Inter-neurons

Painful Stimulus


A simple model or minimum circuit
A Simple model or Minimum Circuit:

HIGHER LEVEL CONTROL

Pain Stimulus

MotoNeuron

+

+

+

Sensory

Neuron

Inter

Neuron

Inter

Neuron

Flexor

MotoNeuron

-

-

Inter

Neuron

Inter

Neuron

Extensor




Neural development

Neural Development

CS182/CogSci110/Ling109

Spring 2005

Srini Narayanan

[email protected]


Lecture overview
Lecture Overview

  • Summary Overview

  • Development from embryo

  • Initial wiring

  • Activity dependent fine tuning

  • Additional information/details

    • Principles of Neural Science. Kandel, Schwartz, Jessell, Mcgraw-Hill (2000).


How does this happen
How does this happen

  • Many mechanisms of human brain development remain hidden, but

    • Neuroscientists are beginning to uncover some of these complex steps through studies of

    • the roundworm, fruit fly, frog, zebrafish, mouse, rat, chicken, cat and monkey.

  • Many initial steps in brain development are similar across species, while later steps are different.

  • By studying these similarities and differences, we can learn how the human brain develops and how brain abnormalities, such as mental retardation and other brain disorders, can be prevented or treated.


Summary overview
Summary Overview

  • The Amoeba (ref. book) uses

    • complex sensing molecules penetrating its cell membrane to trigger

    • chemical mechanisms that cause it to move its blobby body towards food and away from harmful substances.

  • Neurons are also cells and,

    • in early development, behave somewhat like Amoeba in approaching and avoiding various chemicals.

    • But rather than the whole cell moving, neural growth involves the outreach of the cell’s connecting pathway (axon) towards its downstream partner neurons.


Summary overview1
Summary Overview

  • The basic layout of visual and other maps is established during development by millions of neurons

    • each separately following a pattern of chemical markers to

    • its pre-destined brain region and specific sub-areas within that region.

  • For example, a retinal cell that responds best to red light

    • in the upper left of the visual field will connect to cells in the brain that are tuned to the same properties and

    • these cells, in turn, will link to other cells that use these particular properties giving rise to specific connectivity and cell receptive field properties (topographic maps).


Summary overview2
Summary Overview

  • In the course of development,

    • detector molecules in the growing neuron interact with

    • guide molecules to route the connection to the right general destination, sometimes over long distances as in the connection from the spinal cord to the knee.

  • This process will get neural connections to the right general area, but

    • aligning the millions of neurons in visual and other neural maps also involves

    • chemical gradients, again utilizing mechanisms that are very old in evolutionary terms.


Summary overview3
Summary Overview

  • When an axon tip gets to an appropriately marked destination cell, the contact starts a process that develops rudimentary synapses.

  • Local competition among neural axons with similar marker profiles produces some further tuning at the destination.


Summary overview activity dependent tuning
Summary Overview:Activity Dependent Tuning

  • In fact, the initial wiring is only approximate and leaves each neuronal axon connected to several places in the neighborhood of each of its eventual partner neurons.

  • A second, activity dependent, mechanism is required to complete the development process.

  • The initial chemical wiring actually produces many more connections and somewhat more neurons than are present in adult brains.

  • The detailed tuning of neural connections is done by eliminating the extra links, as well as the strengthening functional synapses based on neural activity.


Summary
Summary

  • Neural development and learning is moving from a mystery to routine science.

  • We know enough to shape theories of how our brains learn skills, including language, and how we acquire and use knowledge.

  • Contemporary theories of learning are also heavily influenced by psychological experiments, some of which are described next week.


Lecture overview1
Lecture Overview

  • Summary Overview

  • Development from embryo

    • Neural tube development

    • Cell division and neuronal identity

    • Mechanisms for cell type formation and communication

  • Initial wiring

  • Activity dependent fine tuning

  • Plasticity and Learning


Development from embryo
Development from Embryo

  • The embryo has three primary layers that undergo many interactions in order to evolve into organ, bone, muscle, skin or neural tissue.

    • The outside layer is the ectoderm

      • (skin, neural tissue),

    • the middle layer is the mesoderm

      • (skeleton, cardiac) and

    • inner layer is the endoderm

      • (digestion, respiratory).


Neural tissue
Neural Tissue

  • The skin and neural tissue arise from a single layer, known as the ectoderm

    • in response to signals provided by an adjacent layer, known as the mesoderm.

    • A number of molecules interact to determine whether the ectoderm becomes neural tissue or develops in another way to become skin



In humans, during the 3rd week, this mesoderm begins to segment. The neural plate folds to form a neural groove and folds.


Other structures segment. The neural plate folds to form a neural groove and folds.

including heart,

Skeleton, etc.

The neural groove fuses dorsally to form a tube at the level of the 4th somite and "zips up” cranially and caudally and the neural crest migrates into the mesoderm (somites differentiate to form vertebrae, muscles).


BRAIN DEVELOPMENT. The human brain and nervous system begin to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.


Brain weight
Brain Weight to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.


Lecture overview2
Lecture Overview to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.

  • Summary Overview

  • Development from embryo

    • Neural tube development

    • Cell division and neuronal identity

    • Cell communication

  • Initial wiring

  • Activity dependent fine tuning

  • Plasticity and Learning

  • Development and Infant behavior


Neural cell categories
Neural cell categories to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.

  • After the ectodermal tissue has acquired its neural fate,

  • another series of signaling interactions determine the type of neural cell to which it gives rise.

  • The mature nervous system contains a vast array of cell types, which can be divided into two main categories:

    • the neurons, primarily responsible for signaling,

    • and supporting cells called glial cells.


Factors gradients in cell formation
Factors/gradients in cell formation to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.

  • Researchers are finding that the destiny of neural tissue depends on a number of factors, including position, that define the environmental signals to which the cells are exposed.

    • For example, a key factor in spinal cord development is a secreted protein called sonic hedgehog that is similar to a signaling protein found in flies.

    • The protein, initially secreted from mesodermal tissue lying beneath the developing spinal cord, marks young neural cells that are directly adjacent to become a specialized class of glial cells.

    • Cells further away are exposed to lower concentrations of sonic hedgehog protein, and they become the motor neurons that control muscles.

    • An even lower concentration promotes the formation of interneurons that relay messages to other neurons, not muscles.


Timing of cell differentiation
Timing of Cell Differentiation to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.

  • Remarkably, the final position of the neuron (its laminar position) is correlated exactly to its birthdate

    • The birthdate is the time of final mitosis

  • Cells leaving later migrate past the older neurons (in deeper cortical layers) to the outermost cortex.

  • The layering of the cortex is thus an inside-first outside-last layering.


Lecture overview3
Lecture Overview to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.

  • Summary Overview

  • Development from embryo

  • Initial Wiring details

    • Axon Guidance

    • Synapse formation

  • Activity dependent fine tuning

  • Plasticity and Learning

  • Development and Infant behavior


Axon guidance mechanisms
Axon guidance mechanisms to develop at three weeks’ gestation as the closing neural tube (left). By four weeks, major regions of the human brain can be recognized in primitive form, including the forebrain, midbrain, hindbrain, and optic vesicle (from which the eye develops). Irregular ridges, or convolutions, are clearly seen by six months.

  • Axonal growth is led by growth cones

    • Filopodia (growing from axons) are able to sense the environment ahead for chemical markers and cues.

    • Mechanisms are fairly old in evolutionary terms.

  • Intermediate chemical markers

    • Guideposts studied in invertebrates

  • Short and long range cues

    • Short range chemo-attraction and chemo-repulsion

    • Long range chemo-attraction and chemo-repulsion

  • Gradient effects


Axons locate their target tissues by using chemical attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.


Synapse formation
Synapse formation attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • The two cells exchange a variety of signals.

    • Vesicles cluster at the pre-synaptic site

    • Transmitter receptors cluster at the post-synaptic site.

  • The Synaptic Cleft forms

    • When the growth cone contacts the target cell (immature muscle cell in the case of a motor neuron), a cleft (basal lamina) forms.

    • Multiple growth cones (axons) get attracted to the cleft.

  • All but one axon is eliminated.

  • A myelin sheath forms around the synaptic cleft and the synaptic connection is made.


Overall process
Overall Process attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.


Basic process
Basic Process attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Neurons are initially produced along the central canal in the neural tube.

  • These neurons then migrate from their birthplace to a final destination in the brain.

  • They collect together to form each of the various brain structures and acquire specific ways of transmitting nerve messages.

  • Their processes, or axons, grow long distances to find and connect with appropriate partners, forming elaborate and specific circuits.

  • Finally, sculpting action eliminates redundant or improper connections, honing the specificity of the circuits that remain.

  • The result is the creation of a precisely elaborated adult network of 100 billion neurons capable of a body movement, a perception, an emotion or a thought.


Nature requires nurture
Nature requires Nurture attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Initial wiring is genetically controlled

    • Sperry Experiment

  • But environmental input critical in early development

    • Occular dominance columns

      • Hubel and Wiesel experiment


Sperry s experiment
Sperry’s experiment attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Each location in space is seen by a different location on the retina of the frog

  • Each different location on the retina is connected by the optic nerve to a different location in the brain

  • Each of these different locations in the brain causes a different movement direction.

  • In a normal animal, a retinal region which sees in a particular direction is connected to a tectal region which causes a movement in that direction


Innervation of the optic tectum
Innervation of the Optic tectum attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Ganglion Cells in the retina map systematically to cells in the optic tectum.

  • The image of the external stimulus is inverted in the retina and the mapping from the retina to the optic tectum reverts to the original image.

  • The Nasal ganglion cells of the retina map to the posterior region of the Optic tectum and the temporal ganglion cells map to the anterior region of the tectum


Sperry s experiment1
Sperry’s experiment attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Sperry took advantage of the fact that in amphibians, the optic nerve will regrow after it has been interrupted

  • Sperry cut the optic nerve and simultaneously rotated the eye 180 degrees in the eye socket.

  • In 'learning’ movements to catch prey, the part of the retina now looking forward (backward) should connect to the part of the brain which causes forward (backward) movement.


Sperry s findings
Sperry’s findings attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • After regeneration,

  • his animals responded to prey items in front by turning around and

  • to prey items behind by moving forward. and

  • kept doing this even though they never succeeded in reaching the prey.


Conclusion from experiment
Conclusion from experiment attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • The conclusion from this (and some supporting experiments) is

  • that the pattern of connections between retina and tectum, and the movement information represented is not based on experience.

  • It is innate based on the initial distribution of chemical markers in the brain.


Lecture overview4
Lecture Overview attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Summary Overview

  • Development from embryo

  • Initial wiring

  • Activity dependent fine tuning


The role of the environment
The role of the environment attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • The development of ocular dominance columns

    • Cat and later monkey (Hubel and Wiesel)

  • Retinal input connects to the LGN (Thalamus)

    • LGN is composed of layers. Each layer receives input (axons) from a single eye

  • LGN connects to layer IV of the visual cortex

    • The visual cortex develops ocular dominance columns

    • Cells that are connected to similar layers in the LGN get stacked together in columns forming stripes.

http://neuro.med.harvard.edu/site/dh/


LGN attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

VISUAL CORTEX


Monocular deprivation critical period
Monocular deprivation critical period attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • Hubel and Wiesel deprived one of the eyes of the cat (later macaque monkey) at various times 1 week – 12 weeks (in the monkey case) 4 weeks – 4 months (for the cat).

  • The found that the ocular dominance cell formation was most severely degraded if deprivation occurred at 1 – 9 weeks after birth.

  • Deprivation after the plastic period had no long-term effect.


C attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

C

C

C

C

C

C

I

I

I

I

I

I

I

2

4

1

3

6

5

7

Cat Striate Cortex Layer IV

CLOSED

EYE

OPEN

EYE

Monkey Striate Cortex Area 17 (V1) Layer IV


Critical periods in development
Critical Periods in Development attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • There are critical periods in development (pre and post-natal) where stimulation is essential for fine tuning of brain connections.

  • Other examples of columns

    • Orientation columns


Pre natal tuning internally generated tuning signals
Pre-Natal Tuning: Internally generated tuning signals attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • But in the womb, what provides the feedback to establish which neural circuits are the right ones to strengthen?

    • Not a problem for motor circuits - the feedback and control networks for basic physical actions can be refined as the infant moves its limbs and indeed, this is what happens.

    • But there is no vision in the womb. Recent research shows that systematic moving patterns of activity are spontaneously generated pre-natally in the retina. A predictable pattern, changing over time, provides excellent training data for tuning the connections between visual maps.

  • The pre-natal development of the auditory system is also interesting and is directly relevant to our story.

    • Research indicates that infants, immediately after birth, preferentially recognize the sounds of their native language over others. The assumption is that similar activity-dependent tuning mechanisms work with speech signals perceived in the womb.


Post natal environmental tuning
Post-natal environmental tuning attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

  • The pre-natal tuning of neural connections using simulated activity can work quite well –

    • a newborn colt or calf is essentially functional at birth.

    • This is necessary because the herd is always on the move.

    • Many animals, including people, do much of their development after birth and activity-dependent mechanisms can exploit experience in the real world.

  • In fact, such experience is absolutely necessary for normal development.

  • As we saw, early experiments with kittens showed that there are fairly short critical periods during which animals deprived of visual input could lose forever their ability to see motion, vertical lines, etc.

    • For a similar reason, if a human child has one weak eye, the doctor will sometimes place a patch over the stronger one, forcing the weaker eye to gain experience.


Adult plasticity and regeneration
Adult Plasticity and Regeneration attractants (blue) and repellants (orange) located around or on the surface of guide cells. Left: An axon begins to grow toward target tissue. Guide cells 1 and 3 secrete attractants that cause the axon to grow toward them, while guide cell 2 secretes a repellant. Surfaces of guide cells and target tissues also display attractant molecules (blue) and repellant molecules (orange). Right: A day later, the axon has grown around only guide cells 1 and 3.

The brain has an amazing ability to reorganize itself through new pathways and connections rapidly.

  • Through Practice:

    • London cab drivers, motor regions for the skilled

  • After damage or injury

    • Undamaged neurons make new connections and take over functionality or establish new functions

    • But requires stimulation (phantom limb sensations)

  • Stimulation standard technique for stroke victim rehabilitation


When nerve stimulation changes, as with amputation, the brain reorganizes. In one theory, signals from a finger and thumb of an uninjured person travel independantly to separate regions in the brain's thalamus (left). After amputation, however, neurons that formerly responded to signals from the finger respond to signals from the thumb (right).


Possible explanation for the recovery mechanism
Possible explanation for the recovery mechanism brain reorganizes. In one theory, signals from a finger and thumb of an uninjured person travel independantly to separate regions in the brain's thalamus (left). After amputation, however, neurons that formerly responded to signals from the finger respond to signals from the thumb (right).

  • The initial pruning of connections leaves some redundant connections that are inhibited by the more active neural tissue.

  • When there is damage to an area, the lateral inhibition is removed and the redundant connections become active

  • The then can undergo activity based tuning based on stimulation.

  • Great area for research.


Summary1
Summary brain reorganizes. In one theory, signals from a finger and thumb of an uninjured person travel independantly to separate regions in the brain's thalamus (left). After amputation, however, neurons that formerly responded to signals from the finger respond to signals from the thumb (right).

  • Both genetic factors and activity dependent factors play a role in developing the brain architecture and circuitry.

    • There are critical developmental periods where nurture is essential, but there is also a great ability for the adult brain to regenerate.

  • Next lecture: What computational models satisfy some of the biological constraints.

  • Question: What is the relevance of development and learning in language and thought?


5 levels of neural theory of language
5 brain reorganizes. In one theory, signals from a finger and thumb of an uninjured person travel independantly to separate regions in the brain's thalamus (left). After amputation, however, neurons that formerly responded to signals from the finger respond to signals from the thumb (right). levels of Neural Theory of Language

Spatial Relation

Motor Control

Metaphor

Grammar

Cognition and Language

Computation

Structured Connectionism

abstraction

Neural Net

SHRUTI

Computational Neurobiology

Triangle Nodes

Biology

Neural Development

Quiz

Midterm

Finals


ad