Biological mechanosensation has been a source of inspiration for advancements in artificial sensory systems. Animals rely on sensory feedback to guide and adapt their behaviors and are equipped with a wide variety of sensors that carry stimulus information from the environment. Hair and hair-like sensors have evolved to support survival behaviors in different ecological niches. Here, we review the diversity of biological hair and hair-like sensors across the animal kingdom and their roles in behaviors, such as locomotion, exploration, navigation, and feeding, which point to shared functional properties of hair and hair-like structures among invertebrates and vertebrates. By reviewing research on the role of biological hair and hair-like sensors in diverse species, we aim to highlight biological sensors that could inspire the engineering community and contribute to the advancement of mechanosensing in artificial systems, such as robotics.

Learning to navigate a changing environment requires the ability to detect when a reward no longer matches a previous expectation. While the hippocampus is essential for adapting behavior strategies when reward expectations are violated and is known to integrate goal-related information into spatial maps, the precise dynamics by which these maps update during an unexpected reduction in reward magnitude is not well understood. Using longitudinal calcium imaging of neuronal activity in behaving mice, we found that hippocampal CA1 population activity encodes reward magnitude through elevated event rates at high value locations. Within this population, we discovered a specialized group of reward tethered place cells that bind spatial context to reward magnitude. These reward tethered place cells exhibit spatial fields across the environment while simultaneously exhibiting activity anchored to high-value reward locations. Upon reward reduction, CA1 population activity equalizes and these neurons undergo a selective and rapid remapping that precedes behavioral adjustment to the reward downshift. The broader spatial map remains intact, indicating that this change allows the animal to update the value of a goal while preserving a stable representation of its surroundings. This selective reorganization of hippocampal firing patterns could support adaptive decision making by updating internal models of the world when expectations are violated. Abstract Figure: Graphical Masala N., Donahue M., etal.:

Objective: Memory problems are comorbid with temporal lobe epilepsy (TLE). Animal models of TLE reveal impairments in spatial firing fields of hippocampal place cells, providing a potential neural substrate for memory problems. Each subfield of the hippocampus carries out unique aspects of spatial memory, yet little is known about how individual subfields are perturbed. Here, we investigated the spatial coding properties of the three major subfields of the hippocampus. Methods: Single unit recordings were made from CA1, CA3, and the dentate gyrus (DG) of mice ( n = 10, 6 male [M]/4 female [F]) induced with epilepsy using the suprahippocampal kainate model and in control mice injected with saline ( n = 6, 3 M/3F). Place cell activity was measured while mice foraged in highly familiar environments to assess basic place cell properties and in novel environments to assess remapping. Results: A lower percentage of cells were classified as place cells in CA1 of epileptic mice, whereas percentages were similar in CA3 and DG compared to control. Place fields of CA1 were less coherent, place fields of CA3 were less stable, and place fields in DG had smaller differences between in‐field and out‐of‐field firing. All regions constructed new distinct maps within the first session of exposure to a novel environment; however, new maps in CA3 trended toward instability. Significance: These results point to specific deficits within subfields of the hippocampus, which may indicate that there are different cellular and network mechanisms at play. Such heterogeneity would be predicted to contribute differently to memory deficits.

Structured Objective: Memory problems are comorbid with Temporal Lobe Epilepsy (TLE). Animal models of TLE reveal impairments in spatial firing fields of hippocampal place cells, providing a potential neural substrate for memory problems. Each subfield of the hippocampus carries out unique aspects of spatial memory, yet little is known about how individual subfields are perturbed. Here, we investigated the spatial coding properties of the three major subfields of the hippocampus. Methods: Single unit recordings were made from CA1, CA3 and the dentate gyrus (DG) of mice (N = 10, 6M/4F) induced with epilepsy using the supra-hippocampal kainate model and in control mice injected with saline (N = 6, 3M/3F). Place cell activity was measured while mice foraged in highly familiar environments to assess basic place cell properties and in novel environments to assess remapping. Results: A lower percentage of cells were classified as place cells in CA1 of epileptic mice, whereas percentages were similar in CA3 and DG compared to control. Place fields of CA1 were less coherent, place fields of CA3 were less stable, and place fields in DG has smaller differences between in-field and out of field firing. All regions constructed new distinct maps within the first session of exposure to a novel environment, however new maps in CA3 trended toward instability. Significance: These results point to specific deficits within subfields of the hippocampus, which may indicate that there are different cellular and network mechanisms at play. Such heterogeneity would be predicted to contribute differently to memory deficits. Key Points: CA1 exhibits place map quality problems; CA1 has fewer place cells and those remaining have reduced spatial coherence CA3 exhibits place map stability problems; CA3 has lower spatial correlation within sessions and trends toward not forming stable new maps in a novel environment. DG exhibits reduced signal to noise; DG has smaller differences between in-field and out of field firing rates.