Coding of subjective sensory experience in the crow brain
Final Report Abstract
The ability to experience and report subjective perceptions necessarily arises from brain processes that emerged through evolutionary history. Still, fundamental questions like when in phylogeny and from which neural structures consciousness can emerge are largely unknown. Based on our results, we conclude that the activity of neurons in the associative endbrain area NCL constitutes an avian neural correlated of subjective experience. We managed to answer the main questions of the project: NCL neurons respond as a function of the subjective sensory and memory experiences of crows. Our findings in the corvid bird speaks to the phylogenetic origins of sensory consciousness. It excludes the proposition that only primates and possibly other mammals possessing a layered cerebral cortex are endowed with sensory experiences. How, then, can this finding in crows be reconciled with mammals and primates? One scenario would postulate that birds and mammals inherited this trait of subjective experience from their last-common ancestor. If true, this would date the evolution of primary consciousness back to at least 320 million years when reptiles and birds on the one hand, and mammals on the other hand, evolved from the last common stem-amniotic ancestor. This scenario would predict that (at least) all amniote vertebrates are consciously aware. An alternative scenario would posit that consciousness was not inherited from an ancient common ancestor in the vertebrate lineage but emerged independently based on convergent evolution on different branches of the animal ‘tree of life’. According to this hypothesis, consciousness was absent in the common stem-amniotic ancestor, but—comparable to homeothermy—evolved later and independently during the rise of birds and mammals. Subjective experience as a convergently evolved trait might then even be found in very remotely-related but cognitively-advanced invertebrate species, such as hymenopteran insects (e.g. bees) or cephalopods. Combining measurements of brain signals with controlled behavioural protocols will help to further delineate the phylogenetic roots of conscious experience in the animal kingdom.
Publications
- (2017) Encoding of global visual motion in the nidopallium caudolaterale of behaving crows. Eur J Neurosci. 45(2):267–277
Wagener L, Nieder A
(See online at https://doi.org/10.1111/ejn.13430) - (2018) Neurons in the crow nidopallium caudolaterale encode varying durations of visual working memory periods. Exp Brain Res. 236(1):215–226
Hartmann K, Veit L, Nieder A
(See online at https://doi.org/10.1007/s00221-017-5120-3) - (2019) Neuronal Correlates of Spatial Working Memory in the Endbrain of Crows. Curr Biol. 29(16):2616–2624
Rinnert P, Kirschhock ME, Nieder A
(See online at https://doi.org/10.1016/j.cub.2019.06.060)
