Neuronal responses to motion and apparent motion in the optic tectum of chickens.

The ability to detect moving objects is crucial for survival and is a basic capability in the animal kingdom. In the optic tectum, a major center of the visual pathway of birds, neurons have been found that seem to be perfectly suited to encode motion. These cells, located in the stratum griseum centrale, receive a direct retinal input at their distal dendrites.

Multimodal integration in the chicken.

In everyday life we constantly perceive and discriminate between a large variety of sensory inputs, the vast majority of which consist of more than one modality. We performed two experiments to investigate whether chickens use the information present in multimodal signals. To test whether audiovisual stimuli are better detected than visual or acoustic stimuli alone, we first measured the detection threshold with a staircase paradigm.

Processing of motion stimuli by cells in the optic tectum of chickens.

The ability to detect motion is crucial for the survival of animals. In the avian optic tectum, motion-sensitive output neurons in the stratum griseum centrale have large dendritic fields and receive direct retinal input at their distal dendrites (bottlebrush endings). It has been hypothesized that the activation of each ending elicits a burst in the neuron.

Shaping a lateralized brain: asymmetrical light experience modulates access to visual interhemispheric information in pigeons.

Cerebral asymmetries result from hemispheric specialization and interhemispheric communication pattern that develop in close gene-environment interactions. To gain a deeper understanding of developmental and functional interrelations, we investigated interhemispheric information exchange in pigeons, which possess a lateralized visual system that develops in response to asymmetrical ontogenetic light stimulation. We monocularly trained pigeons with or without embryonic light experience in color discriminations whereby they learned another pair of colors with each eye.

Mapping of the receptive fields in the optic tectum of chicken (Gallus gallus) using sparse noise.

The optic tectum plays a key role in visual processing in birds. While the input from the retina is topographic in the superficial layers, the deep layers project to the thalamic nucleus rotundus in a functional topographical manner. Although the receptive fields of tectal neurons in birds have been mapped before, a high resolution description of the white and black subfields of the receptive fields of tectal neurons is not available.

Lateralized reward-related visual discrimination in the avian entopallium.

In humans and many other animals, the two cerebral hemispheres are partly specialized for different functions. However, knowledge about the neuronal basis of lateralization is mostly lacking. The visual system of birds is an excellent model in which to investigate hemispheric asymmetries as birds show a pronounced left hemispheric advantage in the discrimination of various visual objects.

Ascending and descending mechanisms of visual lateralization in pigeons.

Brain asymmetries are a widespread phenomenon among vertebrates and show a common behavioural pattern. The right hemisphere mediates more emotional and instinctive reactions, while the left hemisphere deals with elaborated experience-based behaviours. In order to achieve a lateralized behaviour, each hemisphere needs different information and therefore different representations of the world.