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Home , Instinct, Lateral inhibition

Brain and : Networks and

• Evolution and • Networks • Single neurons Mammalian brains: size and cell counts, emphasizing neocortex

Herculano-Houzel Front Hum Neurosci 2009 Tool use in Caledonian crows

Weir et al. Science 2002 Bird forebrain has all the mammalian parts – or – mammalian forebrain is like bird/reptile vertebrate lineage

Figure 2 Reiner et al., J Comp Neurol 2004 A canonical circuit with shared types is conserved in birds and

EAG2

ER81

ROR beta

Dugas-Ford et al. PNAS 2012 THE TREE OF

Scala Naturae

The ice cream scoop theory of brain evolution "It's like adding scoops to an ice cream cone," Linden says. "So if you imagine the lizard brain as a single-scoop ice cream cone, the way you make a mouse brain out of a lizard brain isn’t to throw the cone and the first scoop away and start over and make a banana split — rather, it's to put a second scoop on top of the first scoop." David Linden, Johns Hopkins University Niko Tinbergen The Study of

Brain and Behavior: Networks and Neurons

• Evolution and ethology (acoustic bias) • Singing in crickets, Drosophila • Singing in frogs • Electric fish electrolocation • Barn owl • Bat echolocation • Birdsong • Speech and language • Networks • Single neurons Glass-knife fish (Eigenmannia virescens) from living can be called bioelectric signals. Very likely there Table 1. Modes and roles of receptor function are biological meanings other than MODE ROLE the localization of prey-social signals between conspecifics, for example. Passive (animal detects fields from Electrolocation This is especially true for the a.c. external sources) Close range bioelectric fields emitted by the nu Animate (membrane potentials of passive detection of other fish merous species of , as we other ) active detection of objects and will see below. The field is just opening d.c. (e.g. gill potentials) spaces up. a.c.-slow (d.c. modulated by Long range slow movements) directional navigation In addition to the world of bioelectric a.c.-fast (muscle, heart, electric signals there is a world of inanimate organ action potentials) fields. We are now testing whether Inanimate sources Constant signals large homogeneous fields such as motion of water mass in earth's related to place, kind, sex, those induced by the motion of water magnetic field individual masses, like the great ocean currents electrochemical, atmospheric, Changing signals and rivers, through the earth's mag geological processes related to food, threat, attack, netic field can be used as navigational submission, mating clues. The signals are known to be present; the sharks are amply sensi Active (animal detects fields caused tive to detect them. Similarly, the by its own activity) fields caused by waves and tides and Animate (membrane potentials from by magnetic variations as well as by own body) the sharks' own swimming are strong d.c., a.c.-slow, a.c.-fast (same as enough to be detected by sharks, for passive mode above) though we voltsdo not per know meter that theyand uselocally even Inanimate sources Units of voltage them. higher. Man is "polluting" the waters induced +6 potentials+5 +4 from +3 swim+2 +1 :0 -4I and the ground with far higher cur ming in earth's magnetic field There may rents conceivably in return bepaths signals from power lines, I - I from local fieldsleakage, straying and high-power out from ore broadcasting. We are beginning to learn that many bodies of certain kinds, possibly useful potentials at sharp discontinuities catfish at a certain place in Japan fish normally detect and are influenced in the way topographic features of like river bottoms and at gradual during -A. L.. and for some hours before by feeble currents (Fig. 2). the landscape are. There are fields boundaries-perhaps less usable for earthquakes, behavior which is evi caused by earthquakes and other that reason-like river mouths and Resistivity ) milieu In what follows we shall recognize dently dependent on changes in the episodic events such as eruptions and thermoclines. (e =ca.200 electrical Q cm . currents in the earth, picked crustal movements. two modes In shallowof detection-passive water and active; two roles in the biology of the up by the freshwater stream (Hatai activity species-"electrolocation" results from atmo of objectsMany of the available fields may and Abe 1932; Kokubo 1934; Kalmijn spheric disturbances and "electrocommunication" such as lightning of socialrepresent background noise out of and Bullock 1973). and ionosphere signals reverberations, (Table 1); and in two classes which signals must be extracted. Our cluding what of used sense to beorgans-receptors called "static," tuned understanding to of the uses made of The world of natural waters, being and also from low slowfrequency changes andlike thoseday tuned inanimate to fields is quite embryonic, a more or less good conductor, is night alternations. high frequency There are chemical (Fig. 3). The butthree it is as though a door has been busy with electrical Freshwater currents, on a dichotomies are not equivalent, opened. and Surprises can be expected \millimeter IN /and aI kilometer *., scale, many of the permutations are known Figure 2. Relationships and characteristics such as the well-documented hyper from d.c. to f hundreds t~e mi ca..2,000 of kHz, a cmt)from of electroreceptive or suspected-e.g. fish. passive detection sensitivity to mechanical stimuli in fractions of microvolts to several milli Distribution of objects byof low-frequency electroreceptivity receptors and receptors (the shark and flatfish case of Fig. 1), Notactive electrolocation by low-fre Resistivity g milieu quency receptors (the case of naviga Electroreceptive electroreceptive tion with the aid of currents induced ca. 200 0 cm) by swimming in the earth's magnetic field), and passive detection of social a signals from conspecifics by high a Electric fish frequency receptors. Nonelectric species Have electric organ lack electric organ 7 unrelated families Passive Figure 4. Schematic representationmarine elasmobranch of employs a long canal We have already seen one example of marine elasmobranch or to teleost put a inconsiderable seawater part of the external the passive mode in Figure 1 and (above) and elasmobranch voltage or teleost gradient adapted across its sensory membrane ; for freshwater (below). Notethe well-adapted that the mural freshwater form (Potamo suggested others, e.g. the navigation resistance of the skin intrygon ohm/cm2 or electric is rela fish) needs no long canal to by electric currents induced by water tively low in the marine achieve and thehigh same in theresult away from the elec masses such as the Gulf Stream moving freshwater forms shown, trical which equator are probably because the whole interior is in the earth's magnetic field (see typical for elasmobranchs virtually evolutionarily isopotential with the equator. adapted to the respective The habitats marine andform for does not load the external electric fish. A.L. = ampulla field becauseof Lorenzini, its tissue fluids are higher in Figure 3. Present knowledge with sensorypermits membranerecog resistivity; at the bottom the freshwaterand form loads the nizing two broad classes canal and with five very coding low resistance external jelly field and onlyvery moderately because its types of electroreceptors, high with resistance the charac walls. Theskin interior resistance repre is so high. 318 American teristics Scientist, Volume and 61 distributions sents meanshown tissue here. fluid resistivity (p). The EOD = electric organ discharge. ON refers to responses to stimulus onset. See Fig. 7 for explanation of coders. Low-frequency High-frequency receptors This content downloaded from 128.135.150.163 on Wed,High-frequency 04receptors Jan 2017 21:07:44receptors UTC All use subject to http://about.jstor.org/terms

1973 May-June 319

This content downloaded from 128.135.150.163 on Wed, 04 Jan 2017 21:07:44 UTC All use subject to http://about.jstor.org/terms Field perturbation from inanimate object

Neural Nets In Electric Fish - 2.1 Example of sympatric species (i.e. occupying the same territory)

2.7 Spectra of pulse-type fish

2.6 Spectra of wave-type fish

neurogenic (fast)

myogenic

(slow, no JAR)

2.5 Jamming Avoidance Response (JAR): dynamic behavior

3.2 The phase plane representation

3.4 JAR behavior is soo simple: move EOD discharge up or down in frequency, away from nearby conspecific

Obvious solution to JAR!! • compare with internal EOD

but the obvious solution is wrong: • 2 chamber experiments • silence EOD, artificial EOD different from natural EOD • Must understand from an evolutionary perspective Opening the loop

3.2 Two compartment experiments

No internal S1: • symmetrical SA/SB: no JAR • SA/SB (or EOD) to head or tail only: no JAR • JAR independent of EOD frequency • Don’t need a “pure” S1 3.6 Two interfering signals (S2, S 3) (orientation also matters)

S2 , S 3 ≤ 0.2 S1

S= S1+S2+S3 (vectoral summation) |S|=length of S H = phase between S and S1 3.14 What is the reference signal for phase?

(My Kingdom for an “S1”! - not Shakespeare)

S2 > S1

same directions of rotation re S1

opposite directions of rotation re phase difference calculation

3.5 Eigenmannia electrosensory system follows the basic vertebrate body plan. (They’re vertebrates!)

3.1 All animals (except a few phyla such as sponges)

Have neurons Neurons have dendrites and axons

Neurons are connected, hence form networks Neurons are connected by chemical synapses or electrical synapses Changes (“plasticity”) at synapses drives learning

Most neurons spike (suprathreshold activity) All neurons receive subthreshold activity

Inputs to neurons can be excitatory or inhibitory Organization of Eigenmannia electrosensory system Preserved topography; multiple maps

4.1 T-unit and P-unit types of receptors The start of separable pathways for time and amplitude

“Suprathreshold” or spiking activity 4.2 S1, S 2 coding by T- and P-units

Rate code 4.3 Different synaptic architectures and patterns of convergence onto secondary cells from P-units and T-units. The concept of the receptive field. Consider P-unit projections onto first cells in CNS: Topographically organized excitatory and inhibitory inputs to individual cells. Gives rise to center-surround organization.

Basilar pyramidal neurons (or E cells) respond to rising stimulus amplitude

Non-basilar pyramidal neurons (or I cells) respond to falling stimulus amplitude

Different classes of cells Center-surround responses of mammalian retinal (visual) ganglion cell The concept of

Excitatory center

Inhibitory surround

-1/4 +1 -1/4 Lateral inhibition and topography: effects across an intensity gradient Lateral inhibition sharpens edges

Physical stimulus

Perceived stimulus Is this effect potent?

Consider T-unit projections onto first cells in CNS: considerable convergence, electrical synapses, temporal summation Summation of subthreshold post-synaptic potentials (PSPs) (ELL spherical cells)

“Subthreshold” activity (with spiking) 4.10 Reduction of jitter (T units vs. torus layer 6)

4.11 Separate pathways for time and amplitude maintained in second order projections

4.9 A solution to comparing different parts of body surface (lesson: interesting wherever topography breaks down)

Heiligenberg and Rose Trends Neurosci 1984 Figure 3 From receptors to electric organ

4.50 A hierarchy of neuronal response types

4.51 Single neurons: Extraordinarily sophisticated computational devices

The resting potential The

Voltage gated channels Intracellular calcium

Hodgkin Huxley framework General form of a voltage gated channel Molecular phylogeny of the Voltage-Gated Ion Channel Superfamily We want to understand networks as collections of neurons Typical constraints:

• Measure spiking (extracellular) activity of small (10s or 100s) of cells at once - can accomplish this during behavior in intact animals • Some if limited knowledge of the cell types and local connections (circuits) ********** • Measure intracellular calcium of populations of cells; or measure intracellular voltage (or current) of only one cell at a time (or a very few cells at once), mostly in reduced or limited preparation • Limited knowledge of the exact inputs to a given cell • Some if limited knowledge of the different classes of ion channels a cell expresses Should we give up?

Obviously, No!

Neuroethology is powerful Intracellular activity is • complex • different between cell classes • reliable within a cell class • amenable to manipulation by pharmacology generic Hodgkin Huxley formulation

dV (t) Cm = −∑ Ii (t,V ) dt i

I (t,V ) = g(t,V )(V −Veq )

p q g(t,V ) = g m(t,V ) h(t,V ) lots of parameters, most of which we cannot directly measure Te End - part 1