“Prefrontal” Neuronal Foundations of Visual Asymmetries in Pigeons

Comparative transcriptomic analysis of left-right sensory differences in Haliotis discus hannai

Asymmetric development, in which functional differences occur between left-right symmetrical organs, is widespread in organisms, including fish and mollusks. However, the asymmetry of symmetrical sensory structures in Haliotis discus hannai, a gastropod with a sensitive sensory system, remains unknown. This study analyzed the transcriptomes of three sensory structures (eyestalks, cephalic tentacles, and epipodial tentacles) to explore potential asymmetries in this species. RNA-seq revealed functional differences in sensory ability and sperm-egg recognition between right and left eyestalks, with cephalic tentacles displaying asymmetry in cytoskeletal organization and cell cycle regulation. Epipodial tentacles showed similar asymmetries, including immune response differences. Moreover, the cAMP-protein kinase A (PKA)-CREB-binding protein (CBP) signaling pathway responded asymmetrically, with PKA responding to activators and inhibitors on both sides and CBP showing a stronger response on the right. These findings provide insights into sensory asymmetry in mollusks and guidance for further investigations of the molecular mechanisms underlying asymmetry in symmetrical organs.

Dynamics and development of interhemispheric conflict solving in pigeons

The dominance of one hemisphere for cognitive operations and decision making may be an efficient mechanism solving interhemispheric conflicts. To understand the ecological significance of the so-called metacontrol, we need better knowledge of its frequency and ontogenetic foundations. Since in pigeons, embryonic light experiences influence degree and direction of interhemispheric specialization and communication, it is conceivable that light affects metacontrol mechanisms. We therefore trained pigeons (Columba livia) with and without embryonic light stimulation in a colour discrimination task. Each eye/hemisphere learnt a different set of colours. After training, hemispheric-specific information was put into conflict and the analysis of conflict decision pattern allowed the identification of hemispheric dominance under binocular and monocular viewing conditions. A majority of pigeons displayed individual metacontrol independent of embryonic light experiences though not in the first test session. Reaction times indicate that interhemispheric mechanisms are critically involved in mediating the dominance of one hemisphere. The impact of interhemispheric components rises with increasing experience and even affects decision making under monocular seeing conditions. Overall results indicate that the hemispheres do not evaluate information independently and that interhemispheric communication in the pigeon brain is much stronger than previously thought and becomes more important with increasing experience.

Visual categories and concepts in the avian brain

Birds are excellent model organisms to study perceptual categorization and concept formation. The renewed focus on avian neuroscience has sparked an explosion of new data in the field. At the same time, our understanding of sensory and particularly visual structures in the avian brain has shifted fundamentally. These recent discoveries have revealed how categorization is mediated in the avian brain and has generated a theoretical framework that goes beyond the realm of birds. We review the contribution of avian categorization research-at the methodical, behavioral, and neurobiological levels. To this end, we first introduce avian categorization from a behavioral perspective and the common elements model of categorization. Second, we describe the functional and structural organization of the avian visual system, followed by an overview of recent anatomical discoveries and the new perspective on the avian 'visual cortex'. Third, we focus on the neurocomputational basis of perceptual categorization in the bird's visual system. Fourth, an overview of the avian prefrontal cortex and the prefrontal contribution to perceptual categorization is provided. The fifth section outlines how asymmetries of the visual system contribute to categorization. Finally, we present a mechanistic view of the neural principles of avian visual categorization and its putative extension to concept learning.