Una introduccion al estudio del cerebro y la cognicion

Introduccion

1. The Brain and Behavior
Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses: What does the signal do?
•Reflexes: A model
•Brain Organizing Principles and Functions

2. Functions
•Communication
•Coordination
•Control
•Cognition
•Complexity

3. Outline: Start With A
Mechanistic View
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses: What does the signal do?
•Reflexes: A model
•Brain Organizing Principles and Functions

4. Evolution
•None
•Nerve net
•Segmented
•Cephalization: an organizing principle (brain-
mind correlation not always obvious!)
•Kineses
•Taxes
•Reflexes

5. Evolution

6. Brain Structure

7. Brain Structure

8. Brain Structure
DRUGS

9. Evolution
•None
•Nerve net
•Segmented
•Cephalization: organizing principle + brain-function rel.
•Kineses
•Taxes
•Reflexes

10. Reflexes
•Kinesis (potato bug)
•Taxis (moth / maggot / fly / tick)
•Reflex: (knee jerk)
–Descartes 161 St. Germaine on the Seine
–Pineal
–Mechanist

11. Reflexes
•Braightenberg: Vehicles

12. Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses
•Reflexes: A model
•Brain Organizing Principles and Functions

13. The Neuron
•100 billion
•Varied in size, shape, function
•Function of neuron sending signals in
real time (ex.)
•What is the signal? - electrical /
chemical

15. Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses
•Reflexes: A model
•Brain Organizing Principles and Functions

16. Origin of nerve signal
•Function of neuron sending signals in
real time (ex.)
•What is the signal? - electrical /
chemical

17. Generation
•Two forces:
–Electrical (ionic)
–Chemical (concentration)
–Give rise to steady-state voltage “resting
potential”
–Universal in cells

19. Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses
•Reflexes: A model
•Brain Organizing Principles and Functions

21. Action Potential

23. Movement of a Signal

25. Action Potential
•Cell actions
•Speed: Muller (light), Helmholtz (43
m/sec)
•Refractoriness
•All or none law
•Coding of intensity: analog-digital +
recruitment (organizing principle)

26. Neuron Communication
•Propagation is much faster if the axon is
myelinated:
•Depolarization proceeds down the axon by a
number of skips or jumps.
•The action potential obeys the all-or-none
law:
•Once it’s launched, further increases in
stimulus intensity have no effect on its
magnitude.

27. Neuron Communication
•Propagation is much faster if the axon is
myelinated:
•Depolarization proceeds down the axon by
a number of skips or jumps.
•The action potential obeys the all-or-
none law:
•Once it’s launched, further increases in
stimulus intensity have no effect on its
magnitude.
•Frequency signals intensity

29. Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses
•Reflexes: A model
•Brain Organizing Principles and Functions

30. Synapses: What happens when
signal reaches end of neuron?
•Two types of actions - excitatory /
inhibitory
•Chemical model with multiple &
functionally different neurotransmitters
•Temporal & spatial summation

32. Synapses

33. Release of Neurotransmitter

35. Synapses

36. Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses
•Reflexes: A model
•Brain Organizing Principles and Functions

37. A Model for building behavior
out of simple building blocks
•Reflexes
•Voting behavior
•Mirror neurons
•Other examples to follow

38. Reflexes: A model

39. Outline
•Functions
•Evolution: structure and behavior
•Basic Unit: The Neuron
•Generation: How does a signal get started?
•Action Potential: How does a signal move?
•Synapses
•Reflexes: A model
•Brain Organizing Principles and Functions

41. Brain Structure (midline)

42. Structure: Central Core

43. Structure: X-Ray View

45. Methods for studying the brain
•Single-cell and population recordings
–Animal studies
–Surgical patient studies
•Stimulation
–Animal studies
–Surgical patient studies
•Damage
–Animal lesions
–Human injury
–Human surgical lesions
•Neuroimaging

46. •Electroencephalogram (EEG) recording
–Electrodes are placed on the surface of the
scalp and record/amplify the electrical
signal given off by the brain
–Event Related Potentials (ERPs) are used
to study how the brain responds to different
stimuli or events

47. CT scan MRI scan

48. –Measures changes in blood-oxygen-
level-dependent (BOLD) activation
–Areas of the brain that are engaged
more in a task, require oxygen rich
blood
–Result show a very small but highly
significant percent change in BOLD
activation (the entire brain is active all
the time)
Functional Magnetic Resonance Imagingin (fMRI)

49. Connectivity measures

Structural connectivity –
measures the movement of
water molecules to chart the
white matter tracts
(visualizing anatomy)
Diffusion Tensor Imaging (DTI)
Diffusion Spectrum Imaging (DSI)
Functional connectivity – uses resting-state fMRI data to chart
cortical regions with temporal synchrony (correlation of
activation patterns)

50. Homunculus Map of Human Cortex

51. Homunculus Map of Human Cortex

52. •Localization of motor
and sensory function
•Topographical
organization
•Cortical representation
related to function not
mass
What does the homunculus tell us?

53. Cortical Damage
•Much of what we know about the cortex comes
from studying brain damage
•Damage at identifiable sites can produce:
•Disorders of planning or social cognition
•Apraxias (disorders in action)
•Agnosias (disorders in perception)
•Aphasias (disorders of language)

54. Case Study: Phineas Gage

56. Disorders of Planning and Social
Cognition
•Caused by damage to prefrontal area
–Disrupts executive control– processes that
allow us to direct and regulate our own
cognitive activities
•e.g., setting priorities, planning, strategizing,
ignoring distracters

57. Apraxias
•Difficulty in carrying out purposeful
movements without the loss of muscle
strength or coordination
–Disconnection between primary and non-
primary motor areas
–Able to carry out each part of a complex
movement, but disruption lies in coordination of
the movements

58. Agnosias
•Visual agnosia: disturbance in recognizing visual stimuli
despite the ability to see and describe them
–Patient video
•Prosopagnosia: inability to recognize faces (fusiform face area)
–Patient video
–Patient video
•Neglect Syndrome: complete inattentiveness to stimuli on one
side of the body
–Patient video
•Akinetopsia: inability to perceive movement
–“I see the world in snapshots – like frames of a move but
most of the frames are missing”

59. Aphasias
•Broca’s Aphasia: disturbance in speech production,
caused by damage to Broca’s area
–Patient video
•Agrammaticism
•Anomia
•Difficulty with articulation
•Wernicke’s Aphasia: disturbance in speech
comprehension, caused by damage to Wernicke’s area
–Patient video
•Disruption in recognition of spoken words
•Disruption in comprehension of the meaning of words
•Inability to convert thought into words

60. Aphasias

61. Localization of Function
•Different regions of the brain serve
specialized functions
•Sensory Information
•Motor Control
•Planning and Social Cognition
•Perception
•Language

62. Connectivity
Congenital Prosopagnosics
show typical BOLD
activation to faces but
severe behavioral deficit in
face processing
DTI show degradation of
tracts connecting posterior
and anterior regions
engaged in face processing
(Thomas et al., 2009)

63. Connectivity
•Autism – Neurodevelopmental disorder
marked by social and communicative deficits
and presence of repetitive behaviors
•Underconnectivity theory – autism phenotype
comes from reduction in global connectivity
(long distance connections between frontal
and parietal/occipital regions) and increase in
local connectivity (particularly in visual areas)
Temple Grandin underconnectivity

64. (Van Essen & Dierker, 2007)
Association cortex – regions not receiving direct
sensory input. Involved in perception, language,
social and executive functioning.
Comparison of human
and macaque monkey
brain show that major
areas of cortical
expansion occur in
association cortex

65. Cerebral Cortex
•Most projection areas have contralateral
organization:
–Left hemisphere receives information from
right side of body (sensory), or controls
right side of body (motor)
–Right hemisphere receives information
from left side of body (sensory), or controls
left side of body (motor)

66. Split Brain

68. Split Brain
Split brain patient

69. Phantom Limb Pain
•Amputees often feel pain in a limb after
it has been removed
–Mirror box therapy video
•Sensation in limb can be felt when
touching other areas of body (most
common: lost hand feels touch of face)

70. Neural remapping

71. Plasticity
•The brain is plastic—subject to alteration in the way
it functions, such as:
•Changes in the brain’s overall architecture
•The central nervous system can grow new neurons:
•But appears unable to do so with cortical injury
•This promotes stability in the brain’s connections but is an
obstacle to recovery from brain damage.

72. Plasticity
•Neurons are subject to alteration in the way
they function, such as:
•Changes in how much neurotransmitter a
presynaptic neuron releases
•Changes in neuron sensitivity to neurotransmitters
•Creating new connections by growing new
dendritic spines

73. Principles and Functions
•Cephalization
•All-or-None Law
•Frequency Coding of Intensity
•Doctrine of Specific Nerve Energies
•Localization of Function (+ Integration)
•Topographic Projection (& Distortion)
•Split Brain (Crossed Connections)
•Connectivity & Functional Connectivity
•Neuro-plasticity & Reorganization