Central Nervous System

Main regions:

• cerebrum (cortex and white matter)
• cerebellum -- highly regular architecture, for timing and serial order
• thalamus eg, lateral geniculate nucleus (LGN) -- all visual info passes through
• basal nuclei - sensory and motor way stations

Neurons

a) afferent (to center), efferent (away)
b) excitatory vs. inhibitory (different connections)
c) spatial and temporal summation, refractory period
d) receptive potential (graded) in receptors only
e) action potential (fixed size) in all neurons (esp axon)

Architecture

a) maps everywhere - topical organization
b) lateral inhibition - for sharpening and gain control
c) connectivity patterns
d) broad tuning of indiv cells - refined tuning by groups

Embryology:

1) Darwinian devlopment: overconnect, compete, prune
2) Hebbian selection
3) plasticity - great early, poor later

Neural tube

Fish brain - fundamentally similar to embryonic mammal

Mammal - dominance of cerebrum,

Human - dominance of prefrontal

Cerebrum in Mammals

Visual Pathways - number of relevant cells

Visual Processing

1. Retina: extract freq components (with concentric lat-inhibitn rings) - as basis functions on retina - using center-surround pattern fragments, etc), Extracts freq and amplitude at all spatial frequencies and times, but compress dynamic range.

2. LGN (lat gen nuc), V1: more abstract generalizations about pattern

3. Other maps for other important visual properties. (most monkeys have 14 separate visual maps)

• hierarchy: microfeatures to larger features then to whole objects at various depths - simple cells, complex, hypercomplex, etc - both innate and learned - but `grandmother cells'??
• relevant categories of events out there - mostly learned,
• inferred (guessed) events - hypothesized events - some veridical, some not (like `apparent motion')

Language Motor Processes (based in part on T. Deacon's `Symbolic Species') [NOT LECTURED ON]

• lower brain stem: respiration, larynx, tongue (visceral motor system, fairly autonomous) breathing, swallowing, coughing
• mid brain stem (`reticular formation'): facial motor, jaw muscles (part of cortical/skeletal motor system)
• upper brain stem (`central gray area'): innate calls, startle, facial expression, laughing, sobbing (`limbic system')
• cortex: words, conscious imitation.

Broca's aphasia - no lang production, comprehension better than production

Wernicke's aphasia - poor comprehension, jargony but fluent production

Other aphasias (all of them cortical problems): alexia (lost reading ability), agraphia (lost writing despite speech, reading and motor skills), etc

Lateralization of cortical function: handedness and language only