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Asymmetric top-down modulation of ascending visual pathways in pigeons
Nadja Freund1, Carlos E Valencia-Alfonso2, Janina Kirsch3
1Department of Psychiatry, University of Tübingen, 72076 Tübingen, Germany.
Neuropsychologia
|August 19, 2015
Summary
Cerebral asymmetries in pigeons show the left hemisphere dominates experience-based visual tasks. Descending pathways in the left brain hemisphere modulate thalamic responses, influencing behavior and confirming left-hemisphere superiority.
Area of Science:
- Neuroscience
- Comparative Psychology
- Animal Behavior
Background:
- Cerebral asymmetries are common across species, with the left hemisphere often linked to categorization and experience-based behaviors.
- Pigeons possess an asymmetrically organized visual system, making them a suitable model for studying brain lateralization.
Purpose of the Study:
- To investigate how descending forebrain pathways asymmetrically modulate visual responses in the pigeon thalamus.
- To determine the functional impact of these asymmetries on behavior, particularly in experience-based visual tasks.
Main Methods:
- Recording neuronal activity in the nucleus rotundus (thalamic visual relay) while modulating descending pathways from left and right hemispheres.
- Behavioral experiments involving monocular color discrimination tasks and interhemispheric conflict stimuli.
- Transient inactivation of specific hemispheric pathways to assess their role in behavioral dominance.
Main Results:
- Left and right hemispheric descending systems differentially modulated visually evoked responses in thalamic neurons.
- The left hemisphere showed greater modulation of thalamic activity, suggesting a role in processing experience-based information.
- Behavioral tests revealed left hemisphere dominance in visual discrimination tasks, which was reduced by inactivating left-hemispheric pathways.
Conclusions:
- Functional asymmetries in descending systems play a crucial role in the left hemisphere's superiority in experience-based visual tasks.
- Top-down control from the forebrain asymmetrically influences ascending visual pathways at the thalamic level.
- These findings contribute to understanding the neural basis of brain lateralization and its behavioral consequences across vertebrates.
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