Announcements Jamming Avoidance Response (JAR) Writing assignment - PDF document

9/30/2011 Neuronal Implementation of the Announcements Jamming Avoidance Response (JAR) • Writing assignment due Monday (W22) Df = f neighbor - f own • Check links on website for lecture related supplements • No discussion on Wed after fall break 402 Hz EOD Df = -4 Hz • Wiki-titles due Monday, Oct. 3 Frequency (Hz) 398 Hz Df = +4 Hz 390 Hz Neuronal Implementation of the Walter Heiligenberg (1937-1994) Jamming Avoidance Response (JAR) 410 Hz Df = f neighbor - f own 402 Hz EOD Df = -4 Hz Frequency (Hz) 398 Hz Df = +4 Hz 390 Hz 4 Question: Does the fish compare the Question: Does the JAR depend stimulus with its own pacemaker? on stimulus geometry? Fish’s discharge silenced by curare Stimulus (S2) S2 Fish (S1) Fish (S1) Stimulus (S2) Fish’s discharge silenced by curare S1 S1 + S2 JAR X Pacemaker Pacemaker X JAR JAR Stimulus (S2) Stimulus (S2) EOD Replacement (S1) Answer: No! The JAR relies solely on sensory information Answer: Yes! The JAR only occurs under differential geometry 1

9/30/2011 Combining Two Periodic Signals Results Minimal Stimulus Conditions for JAR in a Beat (Amplitude Modulation) S 1 =300 Hz S 1 =300 Hz (1) Two signals: S1 + S2 + + (2) |Df| < 5 Hz S 2 = 302 Hz S 2 = 298 Hz || || (3) Differential geometry +Df -Df Combined Signal is Also Two sine waves combine to produce a complex wave Modulated in Phase (Timing) (amplitude modulation and phase modulation). S 1 S 2 S 1 + S 2 Relationship Between Amplitude and Fish’s own EOD Neighbor’s EOD Phase Depends on the Sign of Df +Df -Df S 1 S 1 + S 2 Note: go to “links” page to see Flash Video of JAR 2

9/30/2011 Peripheral Electroreceptors Amplitude Increases / Phase Delays +Df Amplitude Decreases / Phase Advances Amplitude Increases / Phase Advances -Df Amplitude Decreases / Phase Delays T-units T-units Note: go to links page to download flash video of T-unit P-units P-units Go go links page to download P-unit video 3

9/30/2011 Together, T-units and P-units provide the Neuroanatomy of the JAR necessary information for executing the JAR +Df -Df Heiligenberg (1991) In: Neural Nets in Electric Fish Neuroanatomy of the ELL T-units converge onto spherical cells • Combining inputs from several T-afferents results in even more precise action potential times Neuroanatomy of the ELL P-units project to pyramidal cells inhibitory interneurons • E-units respond to amplitude increases • I-units respond to amplitude decreases 4

9/30/2011 Neuroanatomy of the JAR The torus is a laminated structure Spherical cells Phase comparisons are made in lamina VI and pyramidal 1) Giant cells receive direct cells project to excitatory input from different laminae spherical cells 2) Spherical cells also send fibers to tiny dendrites of small cells • Pyramidal cells 3) Small cells receive project to several excitatory inputs from laminae in the torus giant cells onto their soma (3, 5, 7, and 8) 4) Small cells receive • Spherical cells convergent timing input from different parts of the project exclusively to body surface lamina 6 5) Small cells respond to differences in timing between different parts of the body surface Convergence of Responses of torus neurons to jamming stimuli amplitude and phase information within Amplitude-sensitive cell (E-unit) Phase-sensitive cell (adv-unit) the torus -Df +Df -Df +Df 1) Small cells in layer 6 project to other layers of AM the torus DPM 2) Phase sensitive neurons are found in layers 5, 7, 8a, 8b, 8c, and 9 delay -Df +Df advance 3) E and I inputs from ELL Sign-selective cell project to layers 5, 7, 8a, and 8c (E/adv-unit) 4) Phase and amplitude information converge in layers 5, 7, and 8 5

9/30/2011 Model of a sign-selective cell Neuroanatomy of the JAR Phase advance unit E unit I unit -Df-selective +Df-selective neuron neuron Neuroanatomy of the JAR nE integrates input from sign-selective neurons sPPn in the torus and drives prepacemaker nuclei -Df-selective E/adv nE PPn I/del Pn +Df-selective E/del sPPn nE I/adv The African fish Gymnarchus The electrosensory systems of Gymnarchus also performs the JAR and Eigenmannia evolved independently Gymnarchus Eigenmannia EOD EOD electroreception electroreception 6

9/30/2011 Neuronal implementation of Gymnarchus also has separate amplitude- the JAR in Gymnarchus and time-coding primary afferents S-unit • Like Eigenmannnia , Gymnarchus does not have a corollary discharge • Gymnarchus uses the same algorithm of combining information about O-unit amplitude and differential phase Masashi Kawasaki Amplitude-sensitive cell in ELL Phase-sensitive cell in ELL • Gymnarchus has E-units • Eigenmannnia • Gymnarchus and I-units in ELL, just calculates differential calculates differential like Eigenmannia phase in the torus phase in ELL Sign-selective cells in the torus What have we learned from studying the JAR? 1) It is sometimes advantageous to study novel behaviors because they are well-suited to neurophysiological study 2) Task-specific functions are encoded in separate, often parallel, channels. Time and amplitude channels serve specialized functions (similar to barn owl) 3) Recognition units emerge at higher levels in the sensory hierarchy. The complex recognition properties arise from • Gymnarchus has sign- successive analysis of features selective neurons in the torus, just like Eigenmannia 4) Recognition units may drive motor output 5) Identical computational algorithms may evolve in unrelated species by convergent evolution 6) Neuronal substrates for similar functions may involve very different neuronal subtypes 7