Download Feb14lec - NeuralNetworksClusterS12

Feb 7 Review
• Discussed how the concept of vector and vector space
applies to modeling the encoding of faces
– Implications for facial concepts such as beauty and caricatures
• Discussed the goals of Hawkins book
• Described the basic organizational features of the
cerebral cortex
– The major regions of the cortex
– The 6 layer structure of the cortex
• Discussed Hawkins insight regarding the shared
architecture of all cortical areas
– Described the basic features of architectural maps and their
arrangement into hierarchies
Feb 7 Review- con’t
• Reviewed Churchland’s description of the architecture of
a facial recognition network
–
–
–
–
–
Principles of operation of a 3-layer network
Described how networks are trained via back-propagation
Differentiated between a training set and a testing set
Described how network can recognize degraded/occluded faces
Discussed the organization of the face space created and how
categories emerge (male/female)
– Described the vector dimensions of the middle layer – holons
– Described how basins of attraction induce categorization
Case Studies of Prosopagnosia
• A clinical case of prosopagnosia
• Oliver Sacks – The Man Who Mistook his
wife for a hat
• Paintings of Chuck Close
• The Prosopagnosia of Close
LeDoux – Building the Brain
• Neural networks – the false dichotomy
between nature and nurture
• The functions of proteins in developing
architecture – guiding, scaffolding
• Steps in neural development
Origin of Nervous System
Differentiation of Major Regions
Cells arise from ventricle and then migrate
Similar to Figure 4.1 in LeDoux
The Role of Stem Cells
Differentiation and the development of processes
Cell death and synaptogenesis
Development of neuroconnectivity in infancy
Issue of Selection vs. Instruction
• Historical Issues
• The major tenets of selection
– Exuberance, use and subtraction
• Hubel and Wiesel’s observations
– Visual cortical cells form columns that are sensitive to
one eye
– In young animals cells respond to both eyes
– If eye is suture, functional connections only develop
to good eye
– Axons increase in complexity during developmentactivity serves as instruction
Activity based
Neuroconnectivity
• An alternative to back-propagation
• Cells that fire together wire together –
Hebbian connectivity
• Hebbian principle’s operation during
development- synchronized waves along
retina
• Role of NMDA-glutamate receptors
• Role of neurotrophins
Implications for Evolutionary
Psychology
• A priori knowledge in classic nativism innate ideas
• A priori knowledge innate predispositions
– Plasticity present in all neural circuits within
systems
• Fear [Garcia effect]
• Language
• Neural network – nativism vs.
constructionism - Elman / Quartz /
Sejnowski
Ethology emphasize nativism
Predisposition to Learn- Constructivism
Garcia Effect- A classic study illustrating the interaction
between nature and nurture
Nature and nurture in language
Williams Syndrome illustrates how
plasticity is system specific
Although all motor maps are basically the same,
Merzenich studied how they can be constructed by
experience
This principle has been applied to dyslexia by providing
phonemic stimulation to dyslexic children