Early-light embryonic stimulation suggests a second route, via gene activation, to cerebral lateralization in vertebrates.

Genetic factors determine the asymmetrical position of vertebrate embryos allowing asymmetric environmental stimulation to shape cerebral lateralization. In birds, late-light stimulation, just before hatching, on the right optic nerve triggers anatomical and functional cerebral asymmetries. However, some brain asymmetries develop in absence of embryonic light stimulation.

Sensory generalization and learning about novel colours by poultry chicks.

In nature animals constantly encounter novel stimuli and need to generalize from known stimuli. The animal may then learn about the novel stimulus. Hull (1947) suggested that as they learn animals distinguish knowledge based on direct experience from inference by generalization and in support of this view suggested that if a subject is directly trained to a stimulus subsequent extinction of responses is slower than when the response is based on generalization.

Patterns of early embryonic light exposure determine behavioural asymmetries in zebrafish: a habenular hypothesis.

Releasers of innate responses are more effective in many vertebrates when seen by the left eye. In zebrafish Brachydanio rerio, this asymmetry is linked with neuroanatomical asymmetry of the habenular complex (enlarged left lateral and right medial habenular nuclei): if habenular asymmetry is reversed, reader response to releasers shifts to the right eye. Light exposure (schedule: 14/10h,L/D) during the first few days of development post fertilisation (pf) controls the patterning of this asymmetry.

Time-window for sensitivity to cooling distinguishes the effects of hypothermia and protein synthesis inhibition on the consolidation of long-term memory.

The effects of hypothermia on memory formation have been examined extensively, and while it is clear that post-training cooling interferes with the process of consolidation, the nature of the temperature sensitive processes disrupted in this way remain poorly defined. Post-training manipulations that disrupt consolidation tend to be effective during specific time-windows of sensitivity, the timing and duration of which are directly related to the mechanism through which the treatment induces amnesia. As such, different treatments that target the same basic processes should be associated with similar time-windows of sensitivity.

Precise endogenous control of involvement of right and left visual structures in assessment by zebrafish.

Birds and fish use monocular viewing to bring to bear appropriate lateralised specialisations. In larval zebrafish, persistent left eye (LE) viewing of their own reflection is interrupted by a series of brief 'events', in which the right eye has equal use. These recur with precise 160 s periodicity, with the first beginning after 40s, and allow right and left mechanisms to assess the reflection.

The zebrafish as a model for behavioral studies.

Zebrafish genetics is developing at a rapid pace, and this opens up new approaches to understanding genetic control. This short review discusses recent results obtained in behavioral studies in this species, and also shows some promising ways of combining behavioral studies with modern genetic techniques. The zebrafish could provide behavioral models for understanding the neural and genetic control of species-specific behavioral patterns associated with feeding and predator avoidance.

fsi zebrafish show concordant reversal of laterality of viscera, neuroanatomy, and a subset of behavioral responses.

Asymmetries in CNS neuroanatomy are assumed to underlie the widespread cognitive and behavioral asymmetries in vertebrates. Studies in humans have shown that the laterality of some cognitive asymmetries is independent of the laterality of the viscera; discrete mechanisms may therefore regulate visceral and neural lateralization. However, through analysis of visceral, neuroanatomical, and behavioral asymmetries in the frequent-situs-inversus (fsi) line of zebrafish, we show that the principal left-right body asymmetries are coupled to certain brain asymmetries and lateralized behaviors.

A single time-window for protein synthesis-dependent long-term memory formation after one-trial appetitive conditioning.

Protein synthesis is generally held to be essential for long-term memory formation. Often two periods of sensitivity to blockade of protein synthesis have been described, one immediately after training and another several hours later. We wished to relate the timing of protein synthesis-dependence of behavioural long-term memory (LTM) formation to an electrophysiological correlate of the LTM memory trace.

Light experience and the development of behavioural lateralisation in chicks. II. Choice of familiar versus unfamiliar model social partner.

In late-stage embryos of domestic fowl, exposure of the right eye to light entering through the shell induces asymmetry of the thalamofugal visual pathway, together with differences in performance according to whether the right or left eye (RE, LE) is in use (Behav. Brain Res. 38 (1990) 211).

Early asymmetries in the behaviour of zebrafish larvae.

Zebrafish (Brachydanio rerio) larvae (8 days) were tested singly in a swimway made up of six compartments. The larva emerged into each compartment in turn, and its response to visual features (e.g.

Separate processing mechanisms for encoding of geometric and landmark information in the avian hippocampus.

Domestic chicks bilaterally or unilaterally lesioned to the hippocampus were trained to search for food hidden beneath sawdust by ground-scratching in the centre of a large enclosure, the correct position of food being indicated by a local landmark in the absence of any extra-enclosure visual cues. At test, the landmark was removed or displaced at a distance from its original position. Results showed that sham-operated chicks and chicks with a lesion of the left hippocampus searched in the centre, relying on large-scale geometric information provided by the enclosure, whereas chicks with a lesion of either the right hippocampus or both hippocampi were completely disoriented (landmark removed) or searched close to the landmark shifted from the centre (landmark displaced).

Hemispheric lateralization of memory stages for discriminated avoidance learning in the chick.

Memory formation following the one trial discriminated bead task in the chick falls into three stages (short-term, intermediate and long-term memory) that are defined by susceptibility to different classes of drugs. The stages show sharply timed offsets of sensitivity and loss at specific times after inhibition. Recall of the memory in the chick shows cyclical changes that differ in period between left and right hemispheres, and is marked by a series of brief windows of enhanced recall that recur with periods of about 16 and 25 min in the left and right hemispheres respectively.

The use of viewing posture to control visual processing by lateralised mechanisms.

Chicks were trained and tested to run to a dish and feed from it under one of four conditions. In three of these, the dish was covered by a light lid that the chicks readily learned to remove. The square lid (SL) had slightly protruding corners, so that it could be removed by a blow of the bill at a range of positions.

Critical time-window for NO-cGMP-dependent long-term memory formation after one-trial appetitive conditioning.

The nitric oxide (NO)-cGMP signaling pathway is implicated in an increasing number of experimental models of plasticity. Here, in a behavioral analysis using one-trial appetitive associative conditioning, we show that there is an obligatory requirement for this pathway in the formation of long-term memory (LTM). Moreover, we demonstrate that this requirement lasts for a critical period of approximately 5 hr after training.