Costs and benefits of voluntary attention in crows

Neuronal correlates of endogenous selective attention in the endbrain of crows

The ability to direct attention and select important information is a cornerstone of adaptive behavior. Directed attention supports adaptive cognitive operations underlying flexible behavior, for example in extinction learning, and was demonstrated behaviorally in both mammals and in birds. The neural foundation of such endogenous attention, however, has been thoroughly investigated only in mammals and is still poorly understood in birds. And despite the similarities at the behavioral level, cognition of birds and mammals evolved in parallel for over 300 million years, resulting in different architectures of the endbrain, most notably the absence of cortical layering in birds. We recorded neuronal signals from the nidopallium caudolaterale, the avian equivalent to mammalian pre-frontal cortex, while crows employed endogenous attention to perform change detection in a working memory task. The neuronal activity profile clearly reflected attentional enhancement of information maintained by working memory. Our results show that top-down endogenous attention is possible without the layered configuration of the mammalian cortex.

Volitional spatial attention is lateralized in crows

Like humans and many other animal species, birds exhibit left-right asymmetries in certain behaviours due to differences in hemispheric brain functions. While the lateralization of sensory and motor functions is well established in birds, the potential lateralization of high-level executive control functions, such as volitional attention, remains unknown. Here, we demonstrate that carrion crows exhibit more pronounced volitional (endogenous) attention for stimuli monocularly viewed with the left eye and thus in the left visual hemifield. We trained four crows on Posner-like spatial cueing tasks using informative cues to evaluate their volitional top-down attention. The crows detected cued targets using either the left or right eye. As a measure of volitional attention, we calculated reaction time differences for detecting targets that were correctly (validly) and incorrectly (invalidly) cued, separately for the left and right visual hemifields. We found that cued targets were detected more quickly and efficiently in the left visual field compared with the right visual field. Because the left-eye system of the crow's brain processes information primarily from the left visual hemifield, these findings suggest that crows, like humans, exhibit superior executive control of attention in the left-eye/right hemisphere system of their brains.

Conscious Experience of Stimulus Presence and Absence Is Actively Encoded by Neurons in the Crow Brain

The emergence of consciousness from brain activity constitutes one of the great riddles in biology. It is commonly assumed that only the conscious perception of the presence of a stimulus elicits neuronal activation to signify a "neural correlate of consciousness," whereas the subjective experience of the absence of a stimulus is associated with a neuronal resting state. Here, we demonstrate that the two subjective states "stimulus present" and "stimulus absent" are represented by two specialized neuron populations in crows, corvid birds. We recorded single-neuron activity from the nidopallium caudolaterale of crows trained to report the presence or absence of images presented near the visual threshold. Because of the task design, neuronal activity tracking the conscious "present" versus "absent" percept was dissociated from that involved in planning a motor response. Distinct neuron populations signaled the subjective percepts of "present" and "absent" by increases in activation. The response selectivity of these two neuron populations was similar in strength and time course. This suggests a balanced code for subjective "presence" versus "absence" experiences, which might be beneficial when both conscious states need to be maintained active in the service of goal-directed behavior.