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Ruhr-Universität Bochum
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News & Views

Pigeons forage more than expected in a location where food is unpredictable

One major survival-related activity of organisms is to seek food in their environment. To this end, they exploit previously rewarding locations and attempt to approach the cues predictive of the edible items they detect or expect. But foraging is unlikely to be a matter of reinforcement only. If it was, however, foraging activity should follow principles of extinction learning: It should be abolished in a location without reinforcement and proportionally be reduced in a partially reinforced location relative to a fully reinforced one containing the same number of food items. We tested these two hypotheses using a foraging board, which allowed pigeons to find food items hidden in perforated holes. Our results showed that the overall time spent and the overall number of pecks given in one area was related to reinforcement density in that area. To a lesser extent, the same phenomenon occurred with respect to the number of visits per area. However, the time-per-visit and pecks-per-visit ratios were higher in the partially vs. fully reinforced area, suggesting that the pigeons foraged more than expected when food was uncertain. These results will be discussed in the context of the matching law and optimal foraging.

Anselme, P., Wittek, N., Oeksuez, F., Güntürkün, O. (2022). Overmatching under food uncertainty in foraging pigeons. Behavioural Processes, 201, 104728.


News & Views

the trigeminal system of the elephant brain

In August 2021, our PhD student John Tuff visited the lab of Prof Michael Brecht at the Bernstein Center for Computational Neuroscience Berlin, Humboldt-Universität zu Berlin as part of his Max Planck School of Cognition PhD program. In this time, he and the team from Berlin investigated the trigeminal system of the elephant brain and compared it with other sensory nerves as well as the spinal cord. They found the trigeminal ganglia to be huge, larger than a macaque monkey brain, and the maxillary branches, which lead down to the trunk, were thicker than the spinal cord, indicating that the connections to the trunk are more substantial than the nerves to the rest of the body. The infraorbital nerve, which runs through the trunk, was several times as thick as other sensory nerves. These findings suggest that while elephants are mainly known for their excellent sense of hearing, it is possibly underestimated how much these animals rely on their trunks for sensory input.

Purkart, L., Tuff, J. M., Shah, M., Kaufmann, L. V., Altringer, C., Maier, E., Schneeweiß, U., Tunckol, E., Eigen, L., Holtze, S., Fritsch, G., Hildebrandt, T. & Brecht, M. (2022). Trigeminal ganglion and sensory nerves suggest tactile specialization of elephants. Current Biology


News & Views

Acute stress increases left hemispheric activity measured via changes in frontal alpha asymmetries

Each half of the brain is specialized for processing different tasks. The left hemisphere is more strongly involved in language processing while the right hemisphere is dominant for face perception. For example, frontal asymmetries measured with EEG have been linked to both emotional processing in healthy individuals and affective disorders like depression. Stress provides a particularly strong source of negative emotion and has also been related to the pathogenesis of affective disorders. Hence, the aim of the present study was to investigate how acute stress affects frontal EEG asymmetries. For this purpose, continuous EEG data were acquired from 51 healthy adult participants during stress induction with the Trier Social Stress Test. In addition, EEG data were also collected during a non-stressful control condition. Furthermore, EEG resting state data were acquired after both of these conditions. In the stress condition, participants showed stronger left hemispheric activation over frontal electrode sites as well as reduced left-hemispheric activation over occipital electrode sites compared to the non-stressful control condition. There were no stress-related changes in the subsequently recorded resting state data. Our results are in line with predictions of the asymmetric inhibition model, which postulates that the left prefrontal cortex inhibits negative distractors, like the negative emotions resulting from acute stress. Moreover, the results support the capability model of emotional regulation, which states that frontal asymmetries during emotional challenge are more pronounced compared to asymmetries during rest conditions. These models suggest that left frontal activity could be indicative of stronger emotion regulation, which is more pronounced during emotional challenge.

Berretz, G., Packheiser, J., Wolf, O. T., & Ocklenburg, S. (2022). Acute stress increases left hemispheric activity measured via changes in frontal alpha asymmetries. iScience, 103841.


News & Views

Neurons in the pigeon visual network

Discriminating between object categories is a crucial function of primate and bird visual systems. However, brain structures responsible for visual processing greatly differ between birds and mammals.  Here, we examined whether a similar hierarchical organization that operates for processing faces in monkeys also exists in the avian visual system. While pigeons viewed images of faces, scrambled controls, and sine gratings, single neurons were recorded from three visual forebrain regions: the Wulst, the entopallium (ENTO) and mesopallium ventrolaterale (MVL). A greater proportion of single MVL neurons fired to the stimuli, and the population response of MVL neurons distinguished between stimuli with greater capacity than ENTO and Wulst neurons. In contrast to the primate system, no neurons were strongly face-selective and some responded best to the scrambled images. These findings suggest that MVL is primarily involved in processing local features of images, much like the early visual cortex.

Clark, W., Chilcott, M., Azizi, A., Pusch, R., Perry, K. & Colombo, M. (2022) Neurons in the pigeon visual network discriminate between faces, scrambled faces, and sine grating images. Sci Rep 12, 589.


News & Views

perceptual categorization in pigeons

Categorizing helps us to cope with the vast variety of objects in our environment. Although categorization represents a core cognitive function, stimulus features that drive behavior and underlying strategies for categorizing objects often remain elusive. To elucidate these issues, we performed behavioral experiments with pigeons - classic model animals to investigate perceptual categorization. We generated two categories of artificial stimuli called digital embryos and analyzed the pigeons pecking behavior using machine learning. Our results show that pecking is indicative of the upcoming choice and thus related to features of interest. However, individual animals use different stimulus aspects to base their decision on. By using defined artificial stimuli in addition with a detailed analysis of the pecking behavior, our study paves the way to pinpoint stimulus features as well as individual strategies to solve the task.


Pusch, R., Packheiser, J., Koenen, C. Iovine, F. & Güntürkün, O. (2022) Digital embryos: a novel technical approach to investigate perceptual categorization in pigeons (Columba livia) using machine learning. Anim Cogn.

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