Brain, Behavior and Evolution
Changes in Visual Responsiveness following Intercollicular Lesions and their Effects on Avoidance and AttackAndrew R.J.Ethology and Neurophysiology Group, School of Biological Sciences, University of Sussex, Sussex
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Article / Publication Details
Published online: April 01, 2008
Issue release date: 1974
Number of Print Pages: 25
Number of Figures: 0
Number of Tables: 0
ISSN: 0006-8977 (Print)
eISSN: 1421-9743 (Online)
For additional information: https://www.karger.com/BBE
Abstract
In the normal chick, conspicuous visual stimuli induce targetting and pecking together, with vocalization. All three are abolished by lesions of the intercollicular area (ICo) or of connections passing through its medial margin. After such lesions, chicks also cease to treat significant visual stimuli as if they were startling and exciting, and may delay response as a result. However, they are still able to recognise, orient accurately to, and respond appropriately to, a variety of complex visual stimuli (e.g. food grains, copulation object). In addition, they are little affected by strange surroundings. Lesion evidence suggests the mammalian subcollicular area to have similar functions to the ICo and to be homologous with it.A route (present in birds), which is well-known in mammals for its association with threat, defence and escape evoked by strange and frightening objects (amygdala-diencephalic periventricular system-central mesencephalic grey, A-DPS-CMG) is probably important in regulating visual responsiveness to conspicuous and significant stimuli via the ICo (subcollicular area). Two different mechanisms may be involved caudal to the ICo. One consists of tectal afferents which might modulate the evocation of targetting, pecking and other responses via the tectum. The other is the pre-dorsal system of tectal efferents which may mediate such responses. Classical syndromes of tameness and unresponsiveness produced by various interruptions of the A-DPS-CMG route may depend on interruption of connections to these midbrain mechanisms.Attack is depressed by ICo lesions as one aspect of reduced responsiveness to conspicuous and startling visual stimuli. Avoidance, which is apparently mediated by a separate system, much as in Anura, is facilitated.
© 1974 S. Karger AG, Basel
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Article / Publication Details
Published online: April 01, 2008
Issue release date: 1974
Number of Print Pages: 25
Number of Figures: 0
Number of Tables: 0
ISSN: 0006-8977 (Print)
eISSN: 1421-9743 (Online)
For additional information: https://www.karger.com/BBE
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