Gaze Strategy in the Free Flying Zebra Finch (Taeniopygia guttata)

Fast moving animals depend on cues derived from the optic flow on their retina. Optic flow from translational locomotion includes information about the three-dimensional composition of the environment, while optic flow experienced during a rotational self motion does not. Thus, a saccadic gaze strategy that segregates rotations from translational movements during locomotion will facilitate extraction of spatial information from the visual input. We analysed whether birds use such a strategy by highspeed video recording zebra finches from two directions during an obstacle avoidance task. Each frame of the recording was examined to derive position and orientation of the beak in three-dimensional space. The data show that in all flights the head orientation was shifted in a saccadic fashion and was kept straight between saccades. Therefore, birds use a gaze strategy that actively stabilizes their gaze during translation to simplify optic flow based navigation. This is the first evidence of birds actively optimizing optic flow during flight

Imprinting.

Imprinting is a type of learning by which an animal restricts its social preferences to an object after exposure to that object. Filial imprinting occurs shortly after birth or hatching and sexual imprinting, around the onset of sexual maturity; both have sensitive periods. This review is concerned mainly with filial imprinting. Filial imprinting in the domestic chick is an effective experimental system for investigating mechanisms underlying learning and memory. Extensive evidence implicates a restricted part of the chick forebrain, the intermediate and medial mesopallium (IMM), as a memory store for visual imprinting. After imprinting to a visual stimulus, neuronal responsiveness in IMM is specifically biased toward the imprinting stimulus. Both this bias and the strength of imprinting measured behaviorally depend on uninterrupted sleep shortly after training. When learning-related changes in IMM are lateralized they occur predominantly or completely on the left side. Ablation experiments indicate that the left IMM is responsible for long-term storage of information about the imprinting stimulus; the right side is also a store but additionally is necessary for extra storage outside IMM, in a region necessary for flexible use of information acquired through imprinting. Auditory imprinting gives rise to biochemical, neuroanatomical, and electrophysiological changes in the medio-rostral nidopallium/mesopallium, anterior to IMM. Auditory imprinting has not been shown to produce learning-related changes in IMM. Imprinting may be facilitated by predispositions. Similar predispositions for faces and biological motion occur in domestic chicks and human infants. WIREs Cogn Sci 2013, 4:375-390. doi: 10.1002/wcs.1231 For further resources related to this article, please visit the WIREs website.This review is written in memory of the late Sir Gabriel Horn, in recognition of his pioneering work on the neurobiology of imprinting. I am indebted to Robert Levin, Alister Nicol, Revaz Solomonia, Rie Suge, and two anonymous referees for valuable comments on a draft manuscript. The review was written while in receipt of a project grant from the Biotechnology and Biological Sciences Research Council.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/wcs.123

Unusual postnatal development of visually evoked potentials in four brain areas of white zebra finches

Bredenkotter M, Bischof H-J. Unusual postnatal development of visually evoked potentials in four brain areas of white zebra finches. BRAIN RESEARCH. 2003;978(1-2):155-161.The central visual system of white zebra finches is physiologically different from normally coloured (wild type) birds, although the eye pigmentation and the retinofugal projection appear to be normal. Ipsilaterally evoked potentials in the white birds are enhanced in comparison to wild type birds, whereas in albino mammals the ipsilateral component of visually evoked potentials is reduced. The present study shows that the enhancement of ipsilateral responses in white zebra finches is detectable in all areas of the tectofugal pathway, and also in the visual wulst, the only station of the thalamofugal pathway examined so far in white zebra finches. In all investigated areas, the enhancement is already obvious at 20 days after hatching, the earliest age that allows reliable recordings. A deficit in inhibition of ipsilateral stimuli, probably combined with a general increase in the number of ipsilateral projections, may cause the observed enhancements of ipsilateral responses in white birds. (C) 2003 Elsevier Science B.V. All rights reserved

Visual system alterations in white zebra finches

Bredenkotter M, Engelage J, Bischof H-J. Visual system alterations in white zebra finches. BRAIN BEHAVIOR AND EVOLUTION. 1996;47(1):23-32.Visual system anomalies in albino mammals are generally seen to be caused by a lack of retinal pigment and misrouting of retinofugal optic fibers. This study shows that the central visual system of white zebra finches is physiologically different from normally colored (wild type) birds, although the eye pigmentation and the retinofugal projection appear to be normal. Ipsilaterally evoked potentials in our white birds are enhanced in comparison to wild type birds, whereas in albino mammals the ipsilateral component of visually evoked potentials is reduced. Picrotoxin-induced blockade of inhibitory synapses in the ectostriatum reveals remarkable differences between wild type and white zebra finches. In wild type zebra finches, a significant shift of ipsilateral to contralateral stimulus response ratios is observed. However, there is no detectable shift in the white morph. The data suggest that inhibition of ipsilateral stimulus processing, as observed in wild type zebra finches, is significantly reduced in the white morph. Our results indicate that the effects observed in white zebra finches cannot be explained by the theories that have been developed for albinotic animals. We assume that in white zebra finches a genetic defect, which causes the white plumage, is coupled with the demonstrated deviations of inhibitory mechanisms in the central visual system

Flash visual evoked potentials in diurnal birds of prey

The objective of this pilot study was to evaluate the feasibility of Flash Visual Evoked Potentials (FVEPs) testing in birds of prey in a clinical setting and to describe the protocol and the baseline data for normal vision in this species. FVEP recordings were obtained from 6 normal adult birds of prey: N. 2 Harris's Hawks (Parabuteo unicinctus), n. 1 Lanner Falcon (Falco biarmicus), n. 2 Gyrfalcons (Falco rusticolus) and n. 1 Saker Falcon (Falco cherrug). Before carrying out VEP tests, all animals underwent neurologic and ophthalmic routine examination. Waveforms were analysed to identify reproducible peaks from random variation of baseline. At least three positive and negative peaks were highlighted in all tracks with elevated repeatability. Measurements consisted of the absolute and relative latencies of these peaks (P1, N1, P2, N2, P3, and N3) and their peak-to-peak amplitudes. Both the peak latency and wave morphology achieved from normal animals were similar to those obtained previously in other animal species. This test can be easily and safely performed in a clinical setting in birds of prey and could be useful for an objective assessment of visual function