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185 Cards in this Set
- Front
- Back
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Mathematical relationship between body size and brain size
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brain = k* body^(2/3)
brain size and body size both in log value |
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Other mathematical equations relating body size to particular body characteristics
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metabolism --> m = k*body^(2/3)
body surface area --> s = k*body^(2/3) |
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Mathematical relationship between brain size and life span
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life span = k* brain size^(1/3)
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Problems with aging bs. brain size argument
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-mammalian aging rate can be exceeded: chiroptera live 4x longer than expected from their brain size
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Argument in big brain emergence theory
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intense selection pressures for intelligence VS secondary consequence to another adaptation (accident)
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Human brain size relative to chimp
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3x the size - GIANT brain
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Hominid development timeline & jumps in brain size
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5m years ago - hominid separates from chimp
4m - australeopithecus 2m - genus homo 0-1m - species sapiens |
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Boskop man
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-emerged 10,000 years ago
-Brains 1600-1900 cc (avg. 1330) -childlike face; large cranium |
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Mathematical relationship between IQ and brain size
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IQ = 0.12(brain size) + 5.1
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Mosaic Hypothesis for the Origins of the Big Brain
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Regions of the brain associated with certain capacities grew large because of selection pressures for those capacities. Growth of brain parts is responsible for expansion of whole brain.
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Rubicon Hypothesis for the Origin of the Big Brain
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-Expansion changes the balance of brain parts; the cortex became disproportionally large
-No selection for individual features of intelligence |
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Correlation between body size at birth and brain size as an adult
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Direct correlation
OR NOT? pelvic adaptations removed constraints on baby size? big brain a secondary consequence of a secondary consequence? |
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Brain processing capacity
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100 billion neurons per head
100 million Millions Instructions Per Second (MIPS) |
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Brain vs. Computer evolution
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50-150 million years of evolution
VS 40-60 years of innovation/design |
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Alan Turing
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-Quantum mechanics
-Enigma cipher machine -Programming, neural nets, artificial intelligence -Turing Test for Machine Intelligence |
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Universal Turing Machine
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embodies the essential principle of a computer: a single machine which can be turned to any well-defined task by being supplied with an appropriate program
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Computer central processing
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1. Control: centralized
2. Input processing: sequential 3. Output processing: exclusive 4. Storage: by location 5. Initiation: input driven 6. Self processing: minimal |
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Wetware (brain) vs. Hardware (computer)
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"No computer-controlled robot could begin to compete with even a young child in performing some of the simplest everyday activities."
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Brain vs. Computer: Digital computer composition and characteristics
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-made from silicon
-accurate (essentially no errors) -fast (nanoseconds) -execute long chains of logical operations (billions) -don't think like us = irritating |
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Brain vs. Computer: Brain composition and characteristics
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-made from carbon
-inaccurate (low precision, noisy) -slow (milliseconds, 10^6 slower than computer) -short chains of parallel "alogical" operations (10 operations/sec) -largely understandable |
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Speed comparison of brains vs. computers
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Brain operations in Milliseconds, Computer operations in Nanoseconds
Brains 10^6 times slower |
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Material disadvantage of carbon vs. silicon
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Carbon 10^12 worse in product of speed and power
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Perceptual skills in which brain > computer
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-speech recognition
-object recognition -face recognition -motor control |
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Computer software strengths
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Modeling physics
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Computer software weaknesses
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Modeling human cognition
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Centralized vs. Decentralized control: computer
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-processing comes from/returns to a central processing unit
-if CPU fails, whole system fails |
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Centralized vs. Decentralized control: brain
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-distribute control among autonomous subsystems
-much more difficult |
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Left hemisphere processes...
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language
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Right hemisphere processes...
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space
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Connection between left & right hemispheres
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800 million nerve corpus callosum
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"Split brain" patients
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Results from cutting corpus callosum in cases of serious epilepsy
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Processing: computer
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-instructions processed one after another, quickly
-"parallel" port has 25 lines, increased processing in new computers |
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Processing: brain
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-slower but with massively parallel mechanisms
-Optic nerve has over a million fibers from retinal data processing |
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Neuron firing rate vs. computer rate
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neuron < 1,000 per second
computer 1,000,000,000 per second |
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Slow neurons - fast responses
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-humans recognize faces and read sentences 1/10th sec, faster than computers
-if brain processing were sequential (one neuron = one line of code), pattern recognition in 100 lines of code |
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Multi-level output processing: computer
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-locks output channels
-updates overwrite old programs with new ones |
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Multi-level output processing: brain
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-overlays old systems with new ones
-old systems stay as backups and first responders |
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Phineas Gage
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-Iron rod smashed middle/left loves of cerebrum
-Conscious and speaking -Showed disturbed behavior |
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Patient H.M.
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-epileptic patient
-underwent temporal lobectomy to reduce seizure activity -severe anterograde amnesia -temporally graded retrograde amnesia |
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Access by content: computer
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-location based information storage works like a filing cabinet
-one computer "fact" per place -can report memory full |
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Access by content: brain
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-access by content stores information in the connections
-over 10^15 interconnections allow 100,000,000 megabytes |
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Brain storage
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-virtually unlimited capacity
-losing a neuron does not mean you are losing a fact -imperfect recall -access by any feature - database indexed on every field! |
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Growth of Cells in Striate Cortex
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grows significantly with human development
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Input vs. process driven: computer
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-input driven (IPO) input-->processing-->output
-system passive to input |
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Input vs. process driven: brain
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-both input and process driven (POI) processing --> output --> input
-people without input are bored -hallucinate under sensory deprivation -people have active goals |
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Input vs. Process driven systems
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Input: BEHAVIORIST: real world stimuli define behavior
Process: CONSTRUCTIVIST: we create/construct a world, not the world |
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POI systems can alter their input
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-the brain is not just an input processor
-people can anticipate, expect, imagine, and seek what has never occurred |
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Self-processing: computer
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-"clever" mr. clippy is not aware of himself
-analyzed your actions but not his own -not smart enough to recognize rejection |
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Self-processing: brain
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-recursively processes its own processing
-people can have a self-concept, and can think about their thinking |
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Brain's processing tactics
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1. decentralized control
2. massively parallel input processing 3. multi-level output 4. storage by interconnectivity 5. process driven interaction 6. self-processing |
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The brain's processing in a nutshell
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RESPONDS in real time to complex, ambiguous, and incomplete information, with both fast and considered responses, to conditions that continuously change over time, and include other same-type systems
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Optimization of the brain vs. computer
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room sized computer...
-weighs 1000x more -occupies 10,000x more space -consumes 1,000,000x more power |
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Two types of parallel processing connections
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1. point-to-point connections
2. random access connections |
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What are genes?
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A sequence of coding (exon) and non-coding (intron) nucleotide triplets. Exon triplets define amino acid sequence in a protein
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How are base sequences held together?
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Joined by Phosphodiester bonds into the coded gene sequence
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How are genes listed?
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Sequences are generally listed from 5' to 3'
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mRNA
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-reads codes for proteins
-travels out through nuclear pores to RER (rough endoplasmic reticulum) studded with ribosomes, protein complexes with enzymes that read the triplet and guide tRNA which carry amino acids |
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possible amino acid codes
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64
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number of amino acids
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20
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average length of proteins
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300-500 amino acids
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human cells contain ____ genes
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25000-30000
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housekeeping genes
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responsible for routine metabolic functions common to all cells
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Crick & Watson 1953
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found the structure of DNA
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Genome
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hereditary information of an organism; all the information contained in the DNA of that organism
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Central Dogma
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information flows are unidirectional
DNA --> Transcription --> RNA --> Translation --> Protein |
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Genome size does not correlate with complexity
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yeast: .012 x 10^9 (about 5,500 genes)
human: 3 x 10^9 (about 30,000 genes) amoeba: 600 x 10^9 |
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What determines complexity if not gene number or genome size?
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chromosome number? average gene density?
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How does gene duplication give rise to biological diversity? CONVENTIONAL
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ancestral gene produces multiple genes via duplication, and the coding regions of the new genes undergo mutation
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How does gene duplication give rise to biological diversity? NON-CONVENTIONAL
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duplicated genes do not necessarily take on new functions, but instead acquire new regulatory DNA sequence
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Ways gene expression is changed during evolution (1)
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A given pattern-determining gene can itself be expressed in a new pattern. This will cause those genes whose expression it controls to acquire new patterns of expression
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Ways gene expression is changed during evolution (2)
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The regulatory protein encoded by a pattern-determining gene can acquire new functions. Thus, a regulatory protein that was an activator of a set of genes might now repress them.
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Ways gene expression is changed during evolution (3)
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Target genes of a given pattern-determining gene can acquire new regulatory DNA sequences, and thus come under the control of a different regulatory gene. In this way, their pattern of expression is altered.
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Homeotic genes (Hox genes)
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specify the anterior-posterior axis and segment identity of most organisms during early embryonic development
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Mice vs. humans
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-roughly same number of genes (approx 28,000 protein-coding)
-approximately 80% of genes possess one-to-one sequence alignment with the other |
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Chimps vs. humans
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-genes vary by an average of just 2% sequence divergence
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B-catenin gene
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overexpression makes a bigger brain in mouse
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Regulatory protein FOXP2
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-reduced levels can cause severe speech defects
-a few differences with human placement of FOXP2 vs. that in mouse and chimp |
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Brain weight (adult)
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1300 g
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Brain weight (newborn)
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350 g
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Number of neurons - human brain
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100 billion (10 billion = cerebral cortex)
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Number of synapses
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60 trillion
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Rate of neuron growth in early pregnancy
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250,000 per minute
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Development: 3-4 weeks
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-endoderm: guts, lungs & liver
-mesoderm: connective tissue, muscle & vascular system -ectoderm: central & peripheral nervous systems |
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Development: 5-6 weeks
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-nervous system begins to function
-hind, mid, and forebrain are now distinguishable |
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Parts of forebrain
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-Telencephalon
-Diencephalon |
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Parts of midbrain
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-Mesencephalon
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Parts of hindbrain
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-Metencephalon
-Myelencephalon |
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Energy needs of human brain
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-humans allocate a larger share of daily energy to feed brains
-adult humans --> 20-25% resting energy demands -8-10% in other primates -3-5% in other mammals |
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Aiello & Wheeler 1995
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-reduction in gut size may account for the lack of increase in resting metabolic rate among humans and other primates
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Criticism of Aiello & Wheeler
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-primates do not have smaller gut size than other non-primates
-energy costs are compensated for by reduction in proportions of most body parts |
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Changes in brain metabolism: factors
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1. improvements in dietary quality
2. changes in body composition |
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Improvements in dietary quality: brain metabolism
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-diet quality = energy and/or nutrient density
-may result from changes in diet consumption, or the way the food is modified |
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Human diets
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-higher quality than expected for a primate of our size
-we need to eat less volume of food to get the energy/nutrients we require |
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First major increase in brain size (hominid)
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emergence of genus Homo (2.0-1.7 million years ago)
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Diet & Teeth/Jaws
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Homo erectus consuming a richer diet with less plant material and more animal foods (smaller teeth and jaws, but bigger body)
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Changes in body composition: brain metabolism
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-changes in relative proportions of adipose and muscle tissue (more fat, less muscle)
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Humans: under-muscled
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-low levels of skeletal muscle for primates of our size
-primates as a group are relatively under-muscled |
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Humans: fatter than other mammals
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-large energy reserve at birth (15% body fat)
-continue to gain body fat after birth |
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Reasons for improvements in dietary quality
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-more animal foods
-improved tool technologies -food sharing (hunting/gathering) -use of fire and development of cooking? |
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Systematics
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science of classification (Carl Linnaeus)
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Cladistics
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hierarchical classification of species based on evolutionary ancestry; focuses on evolution rather than similarities between species (Will Hennig)
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Phylogeny
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study of the evolutionary relationship among species
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Ontogeny
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study of development, from embryo to adult
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Homology
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similar characteristics in species because they inherited them from a common ancestor (does not imply identical structure)
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Analogy
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characteristics that have evolved independently
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2 main brain size jumps
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prosimian --> simian
ape --> human |
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Average human brain size
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1330 cc
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Models of evolution
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ladder: quantitative differences
tree: qualitative differences |
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Evolutionary trends in nervous system development
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1. bilaterality
2. cephalization 3. increased number of neurons |
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Cnidaria nervous system
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-nerve net
-locomotion, active feeding -sensory/motor neurons |
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Flatworm central nervous systems
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-interneurons
-bilateral symmetry -clustering of cells (centralization) -rostral specialization (cephalization) -faster and more efficient communication |
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Mammalian Central Nervous System subdivisions
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-Forebrain (telencephalon, diencephalon)
-Midbrain (mesencephalon) -Hindbrain (metencephalon, myelencephalon) |
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Evolution of mammals from reptiles marked by the ___
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emergence of the neocortex
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Brain organized and specialized in 3 dimensions
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-anterior/posterior
-dorsal/ventral -left/right |
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___ region of brain shows greater development than other regions
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tencephalon (forebrain)
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Features of mammalian brain evolution
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-increased size of associational areas
-increased laminar differentiation -increased circuitry for biophysical senses -increased density and diversity of cell types -increased number of specialized areas -increased myelination |
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Associational areas - rat. vs. man
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Rat: 16%
Man: 80% |
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Three parts of the Neocortex
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-lateral paleocortex (olfactory piriform cortex)
-medial archicortex (hippocampus & subiculum) -neocortex or isocortex (overlying cortex |
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6 Layers of Neocortex
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1. cell free zone
2-3. cortico-cortical connections 4. receives thalamic input 5. output to subcortical areas 6. output to thalamus |
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Mammalian cortex subdivided into ___ specialized areas
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10-30
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Locations of specialized areas in cortex
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-primary areas surrounded by secondary/tertiary
-visual area in back -somatosensory in front -auditory in between |
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Encephalization
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fraction of gross brain size that represents neuronal processing capacity that is not related to body size
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Encephalization quotient
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ratio of the actual brain mass to the expected brain mass of a typical animal that size (rough estimate of intelligence)
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Evolution of Cognition: Why are we smart?
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-complex social relations among higher primates
-complexities involved in obtaining a varied diet -complexity is not in finding food but in extracting it |
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Strategies for obtaining a better diet
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-change in digestive system to handle different foods
-behavioral strategies to search for high quality, easy to digest foods (tools, increased memory, recognition, verbal signals) |
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Unique features in olfactory system
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-direct projection from olfactory bulb to olfactory cortex in a random access mode
-direct projection from olfactory cortex to hippocampus (memory) and amygdala (emotions) |
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Functions of Smell
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-gatekeepers
-orient in space -mark territory -guide to find other animals -guide to find food -sex -detect spoiled food -detect fire -anosmia -sex -we can smell happiness or fear -twins have identical smell |
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Olfactory receptors: dogs vs. humans
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-dogs have 1.000.000.000.000 receptors
-we have 10.000.000 |
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Three parts to the smell system
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1. olfactory
2. vomeronasal 3. somatosensory |
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Olfactory receptor neurons
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-replaced every 60 days
-about 10,000,000 in humans -about 1000 types |
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Olfactory convergence
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about 10^8 (10,000,000) olfactory receptors converge by a factor of 10^5, into 1000 glomeruli
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Glomeruli
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balls of tangled connections between mitral cells and olfactory receptor neurons
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Questions to be answered upon odor presentation
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Is the odor familiar or not?
Is it dangerous or attractive? Is it associated with rewards or punishment? Is it associated with certain places, objects, or events? What actions need to be taken? |
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Four subcortical structures
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Striatum
Amygdala Hippocampus Thalamo-cortical loop |
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Striatum function
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initiation of movements
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Amygdala function
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emotional responses and stimulation of hormonal responses
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Hippocampus function
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encoding of new memories
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Thalamo-cortical loop function
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evaluation and planning
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Basal Ganglia functions
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-motor planning, sequencing, learning, maintenance
-rule-based and habit (reinforcement) learning -predictive control -working memory -attention -switches in behavioral set |
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Striatum effect on thalamus
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striatum output is inhibitory, basal ganglia can be described by "brake hypothesis"
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Parkinson's disease
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hypokinetic movement disorder; patients cannot activate the supplementary motor area
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Amygdala
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complex interconnection of brain areas to facilitate behaviors involved with defense or alarm in response to threat. Threat can be from odors, bodily threat, possessions, or social relationship.
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Role of Amygdala with lateral/basolateral nuclei
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Nuclei of the amygdala that receive sensory information from the neocortex, thalamus, and hippocampus and send projections to the ventral striatum, the dorsomedial nucleus of the thalamus, and the central nucleus
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Role of Amygdala with central nucleus
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The region of the amygdala that receives information from the basolateral division and sends projections to a wide variety of regions in the brain, involved in emotional responses. Most involved in the expression of emotions
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Role of Amygdala with medial nucleus
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A group of nuclei of the amygdala that receives sensory input, including information about the presence of odors and pheromones, and relays it to the medial basal forebrain and hypothalamus
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Amygdala projections
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-locus coeruleus (increased vigilance - norepinephrine)
-periaqueductal gray matter (behavior arrest - freezing) -trigeminal, facial, motor nuclei (facial expressions of fear) |
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Conditioned emotional responses
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-a classically conditioned response that occurs when a neural stimulus is followed by adverse stimulus
-influenced by lesions to the amygdala |
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Coping response
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a response through which an organism can avoid, escape from, or minimize an aversive stimulus; reduces stressful events of an aversive stimulus
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Each neuron has about ____ synapses
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1000 - 10,000
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Dendrite
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neuron that receives information
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Axon
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neuron that sends information
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"knowing how" vs. "knowing that"
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fundamental distinction, may account for how our permanent memories are organized
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Types of long term memories capable of access
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1. Requires conscious recollection of unique temporally distinct past experience
2. Requires conscious recollection of knowledge, but no unique “experience” 3. Unanswerable - unconscious learning |
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Bilateral damage to hippocampus results in ___
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anterograde amnesia
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Function of Basal Ganglia & Cerebellum
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memory for skills, habits and responses
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Function of Thalamus
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formation of new and working memories
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Function of cortical areas
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encoding of factual memories, storage of episodic and semantic memories, skill learning, priming
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Three stages of memory
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1. sensory memory (priming) representation of stimulus, processed in sensory system
2. short-term memory - working memory - limited capacity (7 items) and duration of 30 seconds 3. long-term memory - large capacity and long duration |
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Two types of LTM
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-semantic memory: factual
-episodic memory: autobiographical information to where and when something happened |
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Recognition
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when a specific cue (face or name) is matched against LTM
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Recall
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when a general cue is used to search memory
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Relearning
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situation where person learns material a second time (quicker)
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Amygdala and hippocampus project to ___
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venal striatum
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Stirato-thalamo-frontal cortex loop
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striatum --> DMN --> frontal cortex --> back to striatum: PLANNING
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Cortex to behavior: hungry animal
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Hippocampus determines if the odor is familiar or new
Amygdala determines the intensity and valence (good or bad) of the odor Frontal-thalamo-cortical-striatum loop influences what the animal will do next: planning of future action Repeat the cycle, forming a working memory and directing animal’s behavioral sequences |
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Frontal lobe location
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deep in the frontal bone of the skull
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Role of frontal cortex/lobe
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-memory formation
-emotions -decision making / reasoning -personality |
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Temporal lobe function
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memory, emotion, hearing, language
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Parietal lobe function
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reception and processing of sensory information from body
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Occipital lobe function
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vision
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Human visual system has more than __ areas of processing
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35
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Human vision process
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retina --> thalamus
midbrain organizes information and packages it |
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Human vision process
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retina --> thalamus
midbrain organizes information and packages it |
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Brain processing of visual thoughts: routine
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-active input
-construction -feedback -reconstruction |
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Brain processing of visual thoughts: routine
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-active input
-construction -feedback -reconstruction |
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Human brain: evolution of association cortex
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enlargement
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Human brain: evolution of association cortex
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enlargement
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Processes of thinking
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distributed throughout the brain, especially in the frontal lobe
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Processes of thinking
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distributed throughout the brain, especially in the frontal lobe
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SSRIs
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selective serotonin reuptake inhibitors (increase serotonin levels in the brain)
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SSRIs
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selective serotonin reuptake inhibitors (increase serotonin levels in the brain)
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Depression and derangement of Biogenic Amine pathways:
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1. serotonin
2. norepinephrine or noradrenaline 3. dopamine |
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Depression and derangement of Biogenic Amine pathways:
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1. serotonin
2. norepinephrine or noradrenaline 3. dopamine |
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Projections from frontal cortex
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1. to motor cortex: activate motor responses
2. to striatum then thalamo-cortical circuits: activate coordinated sequences of motor responses; stretch activity across time 3. to association cortex: organization of actions and thoughts |
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Projections from frontal cortex
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1. to motor cortex: activate motor responses
2. to striatum then thalamo-cortical circuits: activate coordinated sequences of motor responses; stretch activity across time 3. to association cortex: organization of actions and thoughts |
