3 Controversial Hypotheses Primate Cortex

Apr 10, 2012 08:01 PM

1) are there independent functional modules  MODULAR MINDS

2)  is there a single algo at work, operating on many input in parallel?  SINGLE ALGO

3) is difference btwn humans and other primates due to (quantitative diff) in a scalable cortical architecture?  SCALABLE

he says YES to each....

MODULAR MINDS

modules operating thru well defined interfaces;

and neural substrate is under control of a modular genetic architecture.

units can be scaled to build larger working memory and support deeper recursions needed to

qualitat improve out ability to hand language, abstraciton, and social interaction.

page 2:  Brodmann area 4:  unique and final common pathway for all volitional body movement.= MOTOR STRIP:

motor homunulus.

BA3 sensory  (post central gyrus);

BA44/45 of dom hemisphere  BROCA's area   the left in 90% of us...

BA22  Wernickes area

Leda Cosmides and John Tooby:  reciprocity, social dominance, coalition alignment.

SINGLE ALGO:

Mountcastle 1978  cortical columns

cortical column is the unit of computation.

HYPERCOLUMN a bundle of smaller columns = 60,000 cells

cross-modal experiments:  visual stimuli is instead routed to auditory cortex.

FERRET expts:  von Melchner 2000:

In the experiments involving ferrets reported by von Melchner et al [2000], the connections to

the SC are rerouted to the medial geniculate nucleus (MGN) of the thalamus which serves the role of

the LGN for auditory stimuli. To extinguish any auditory stimuli from reaching the rewired cortex,

the SC is ablated and the normal input to the MGN from the auditory tract via the inferior colliculus

(IC) is severed. Not only is the ferret able to perform visual tasks using its auditory cortex, but

the auditory cortex develops a retinotopic map similar to that found in a normally functioning

ferret visual cortex. The neurons in the ferret primary auditory cortex (A1) develop visual response

characteristics including orientation selectivity, direction selectivity and an orderly retinotopic map.

Saxe et al [2011] point to these cortical rewiring experiments as evidence of a single-algorithm

at work, and their analysis of several biologically-inspired learning algorithms provides a plausible

list of properties that such an algorithm might possess. Saxe et al suggest that several existing

algorithms — including independent components analysis, sparse autoencoder neural networks,

restricted Boltzmann machines and sparse coding, all of which yield similar results with no single

algorithm obviously superior —

BROCA divided into  45 (more anterior... input from PFC BA area 10) and  44 (more posterior)

SCALABLE CORTEX Hypthesis:

Darwin  diff btwn man and animals is one of degree not kind...

Sapolsky:  agrees...  diff btwn us and chimps:  we have 3X the neurons.

of rounds of cell division...

chimps/bonobos and US  last common ancestor was 6 to 8M years ago;

mcaques and baboons  about 25MYA.

SPINDLE CELLS only in humans and most apes....  larger and more numerous in humans.

Anterior cingulate,  fronto-insular cortex  and  DL PFC.

decision making,  value judgments, error recog,  appetite reg and consc awareness;

see  John Allman 2010...

page 7:  role of SPINDLES:  BIG NEURONS have BIG AXONS  communicate FASTER

axon speed can be anywhere from 1 to 120 meters/sec... depends on size and myelination.

(Note:  big light turned on for me... node of ranvier is perhaps  1 micron or so in diameter but

internodal distance might a mm or so =>  therefore, must be the local field potential that

is causing the  ion exchange  1 mm away which leads to the saltatory jump.

(answers the question... is the LFP  doing anything or is it simply epiphenomenal...  absolutely... yes!)

of cortical areas:  chips = apes!

page 8:  PAX-6 gene  builds a fruit-fly eye in fruit flies and a mouse eye in mic.

GRANGER:  TCS loops:  thalamo-cortico-striatal loops  to do hierarchical inference,

itertive algos and recrusive embedding in lnaguage.

Randall O'Reilly  210  more anterior areas in PFC  provide higher level control reps.

He says  page 9:   big differences in anterior areas (pfc)  might confer:  bigger working memory;

which migh suport more complex relationships: longer chains of inference, and nested repres structures.

page 9  DISCUSSION:

In general, a deeper stack, whether this be realized in software or by replicating cortical structures,

allows for deeper procedural nesting and richer representations. The larger your memory and

the more powerful the ability to make fine distinctions and infer complex relationships, the larger

your social circle and the more subtle the laws that govern its behavior.

Better means of transferring

knowledge by acting to encourage mimicry and communicating to convey abstract ideas augment

a society’s ability to govern itself and create and share technology. In short, more computation can

propel a species to civilization if it starts out with a sufficiently broad repertoire of basic physical

and social behaviors.

The mystery of homo sapiens’ dominance might also be resolved by appeal to our strong social

instinct. Noting that apes have the capacity for abstract thinking and evidence localizing such

function in the prefrontal cortex, O’Reilly [2006] suggests the possibility that the critical difference may be due not to the hardware, despite its being quantitatively superior, but to “the motivations

that drive us to spend so much time learning and communicating what we have learned to others.”

3 Controversial Hypotheses Primate Cortex

of rounds of cell division...

of cortical areas: &#160;chips = apes!

Attachments

of cortical areas: chips = apes!