Much of the research aimed at understanding how the brain works is motivated by the underlying assumption, explicit or implicit, that it works perfectly, our human brain for sure but that of animals as well. For those who do not believe that a Supreme Being has created a wonderful organ by fiat, it is Evolution that has achieved a similar result by toiling over hundreds of millions of years through trial-and-error. In the forthcoming issue of Neuron, Panikkassery and Treves, link two new studies to suggest that this may not always be the case, at least not for the representations of space the brain produces.
Both studies are mathematical/computational but based on recent experiments in bats flying in a long tunnel, which for the first time have shown how their hippocampi extended environments, not yet comparable to those encountered in the wild, but much more natural than the restricted ones used normally in the lab. The key observation is that these representations are very disorderly, with individual neurons activated in many different locations along the tunnel, some wide and some narrow, sometimes strongly and others weakly. In the same issue of Neuron, Mainali et al demonstrate mathematically that such disorder is very likely the result of a random process, which is not informed by any optimization or even any organizing principle. With a complementary calculation, Schönsberg et al show that dealing with that amount of disorder, their hippocampus is dangerously close to becoming dysfunctional as a memory system. Together, these studies urge us to go outside the lab, and look at how the brain operates in natural environments.
1 Panikkassery A, Treves A. Place cells full of sound and fury, signifying nothing Neuron. 2025 April; 113: in press.
2 Eliav T, Maimon SR, Aljadeff J, Tsodyks M, Ginosar G, Las L, Ulanovsky N. Multiscale representation of very large environments in the hippocampus of flying bats. Science. 2021 May; 372: eabg4020.
3 Mainali N, Zaredo da Silveira R, Burak Y. Universal statistics of hippocampal place fields across species and dimensionalities. Neuron. 2025 April; 113: in press.
4 Schönsberg F, Monasson R, Treves A. Continuous quasi-attractors dissolve with too much–or too little–variability. PNAS Nexus. 2024 December; 3: page525.