competition degeneracy modularity feedback Elements of robustness:

Feedback

Controller ~100 ms retinal inputs Goal Feedforward Controller Eyeball + eye movement Sensed Variable feedback A classic example of feedback in neural circuits: error correction during smooth pursuit

Degeneracy

A classic example of degeneracy in biology: the genetic code

Swensen & Bean, J. Neurosci cell 1cell 2 Neuron-level degeneracy: robustness of bursting in cerebellar Purkinje cells acutely dissociated Purkinje somata

Swensen & Bean, J. Neurosci cell 1 cell 2 cell 3 cell 4 cell 5 cell 6 Neuron-level degeneracy: robustness of bursting in cerebellar Purkinje cells

Neuron-level degeneracy: robustness of bursting in cerebellar Purkinje cells Swensen & Bean, J. Neurosci. 2005

Neuron-level degeneracy: robustness of bursting in cerebellar Purkinje cells Swensen & Bean, J. Neurosci An acute decrease in Na + conductance produces a compensatory increase in voltage- dependent and Ca 2+ –dependent K + conductances.

Neuron-level degeneracy: robustness of bursting in cerebellar Purkinje cells Swensen & Bean, J. Neurosci. 2005

Neuron-level degeneracy: robustness of bursting in cerebellar Purkinje cells Swensen & Bean, J. Neurosci A chronic decrease in Na + conductance produces a compensatory increase in Ca 2+ conductance.

Degeneracy and feedback input output system variables set point homeostat

input output system variables set point homeostat Degeneracy and feedback

Goldman, Golowasch, Marder, & Abbott, J. Neurosci Mapping the state space of neuron-level degeneracy: robustness of bursting in stomatogastric ganglion neurons model stomatogastric ganglion neuron

Goldman, Golowasch, Marder, & Abbott, J. Neurosci Mapping the state space of neuron-level degeneracy: robustness of bursting in stomatogastric ganglion neurons model stomatogastric ganglion neuron

Evolvability - the capacity to adapt by natural selection Evolution - adaptation by natural selection Degeneracy can increase evolvability by distributing system outcomes near phenotypic transition boundaries.

Prinz et al. Nature 2004 Circuit-level degeneracy: robustness of patterns in the stomastogastric ganglion data

Prinz et al. Nature Neuroscience 2004 Circuit-level degeneracy: robustness of patterns in the stomastogastric ganglion model

Competition

A classic example of competition in neural circuits: the developing neuromuscular junction Luo & O’Leary, Ann. Rev. Neurosci. 2005

Another classic example of competition in neural circuits: developing ocular dominance columns Luo & O’Leary, Ann. Rev. Neurosci. 2005

Competitive synaptic interactions: spike-timing dependent plasticity Song & Abbott, Nat. Neurosci Abbott, Zoology 2003 pre leads postpre lags post

presynaptic rate = 10 Hzpresynaptic rate = 13 Hz Competitive synaptic interactions: spike-timing dependent plasticity Song & Abbott, Nat. Neurosci Abbott, Zoology 2003 Homeostatic control of total excitatory drive over a range of presynaptic firing rates.

Modularity

A classic example of modularity in biology: the domain structure of genes and proteins “Exon shuffling” was recognized early in molecular biology as a potential mechanism to generate diverse novel proteins based on existing functional building-blocks.

Bell, Han, & Sawtell, Annu. Rev. Neurosci Oertel & Young, Trends Neurosci Roberts & Portfors, Biol. Cybern Modularity in neural circuits a putative example: “cerebellar-like” circuits

Bell, Han, & Sawtell, Annu. Rev. Neurosci Oertel & Young, Trends Neurosci Roberts & Portfors, Biol. Cybern Modularity in neural circuits mammalian cerebellummammalian dorsal cochlear nucleusteleost cerebellum teleost medial octavolateral nucleusmormyrid electrosensory lobegymnotid electrosensory lobe “cerebellar-like” circuits in vertebrates

Bell, Han, & Sawtell, Annu. Rev. Neurosci Oertel & Young, Trends Neurosci Roberts & Portfors, Biol. Cybern Modularity in neural circuits common anatomical features of cerebellar-like circuits: large principal cells (often GABAergic) having large spiny dendrites principal cells receive excitatory input from a very large population of granule cells forming parallel axon bundles that target the spiny dendrites of principal cells principal cells also receive excitatory ascending input from sensory regions targeting the perisomatic/proximal region of principal cells common functional features of cerebellar-like circuits: parallel fibers carry “higher-level” information (higher-level sensory signals, corollary discharges, proprioceptive info) ascending inputs by contrast carry lower-level information (pertaining to the same sensory modality or sensorimotor task) parallel fiber signals can in principle “predict” the lower-level signals “prediction” is learned by pairing parallel fiber input with ascending sensory input pairing produces a depression of parallel fiber inputs (anti-Hebbian plasticity)

Modularity can permit an organism to process a new input without evolving an entirely novel circuit from scratch—in effect, building diverse objects using existing building-blocks. What “modules” (if any) might be the circuit-level equivalent of protein domains at the molecular level? Sharma, Angelucci, & Sur, Nature 2001 von Melchner, Pallas, & Sur, Nature 2001 Modularity in neural circuits re-routing experiments show that auditory cortex can process visual inputs

shorten summary (to ~400 words) add an assessment (probably >300 words) identify major problems, if any identify unusual strengths, if any for each major point, state the implications clearly for each major problem, indicate appropriate solutions