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Brunwasser, S. J.

Publications and source records attributed to Brunwasser, S. J..

5 recordsLinked to original sources

Mice use predictive environmental cues to adapt predatory behavior in hunting tasks of variable difficulty

Prey capture has long served as a model of complex, multimodal behavior with ethological relevance. In this context, the ability of laboratory animals to capture fleeing prey has been investigated in terms of the sensory systems and neuroanatomical regions required for successful capture. While the ability to hunt is experience-dependent, prey capture is often assumed to be a reflexive behavior, governed by innate neural circuits and a basic drive to obtain food. Whether hunting performance depends on complex learning and cognitive strategy remains largely untested, in part because it is difficult to systematically manipulate the difficulty of predator-prey interactions. To address this, we varied ambient temperature across thousands of trials in which laboratory mice pursued cold-blooded cockroaches, whose movement speed was directly determined by body temperature. As expected, capture difficulty increased as a function of temperature. To test whether mice rely on external cues to adjust their predatory behavior, we then mismatched the ambient temperature and that of the prey, finding that mice learn to use relevant environmental information to inform their hunting strategy. Our results suggest that animals can extract and apply meaningful information from predictive environmental cues to adapt their learned behavior.

animal behavior and cognition↗

Temperature-dependent predation predicts a more reptilian future

Vertebrate diversity increases toward the tropics, but the extent to which this pattern varies with thermoregulatory strategy is unknown. A strong divergence, if confirmed, would imply a global restructuring of vertebrate communities with temperature. Here we present evidence for a novel latitudinal and thermal gradient of comparative vertebrate diversity. Synthesizing over 34,000 terrestrial species distributions, we observe a two-orders-of-magnitude shift in comparative richness with temperature, from endothermic dominance in temperate habitats and high elevations, toward parity with ectotherms in the lowland tropics. Next, we provide experimental support for an underlying thermal gradient of predation. Using machine vision tracking in over 4,500 endotherm-ectotherm predation trials, we show that thermally-mediated differences in performance favor endotherm predators in colder conditions and yield theoretically predicted outcomes, including strike count, distance traveled, and time to capture ectotherm prey. Finally, we integrate theory and data to forecast future patterns of diversity, revealing that as the world gets warmer, it will become increasingly reptilian.

ecology↗

A non-oscillatory, millisecond-scale embedding of brain state provides insight into behavior.

Sleep and wake are understood to be slow, long-lasting processes that span the entire brain. Brain states correlate with many neurophysiological changes, yet the most robust and reliable signature of state is enriched in rhythms between 0.1 and 20 Hz. The possibility that the fundamental unit of brain state could be a reliable structure at the scale of milliseconds and microns has not been addressed due to the physical limits associated with oscillation-based definitions. Here, by analyzing high resolution neural activity recorded in 10 anatomically and functionally diverse regions of the murine brain over 24 h, we reveal a mechanistically distinct embedding of state in the brain. Sleep and wake states can be accurately classified from on the order of 100 to 101 ms of neuronal activity sampled from 100 m of brain tissue. In contrast to canonical rhythms, this embedding persists above 1,000 Hz. This high frequency embedding is robust to substates and rapid events such as sharp wave ripples and cortical ON/OFF states. To ascertain whether such fast and local structure is meaningful, we leveraged our observation that individual circuits intermittently switch states independently of the rest of the brain. Brief state discontinuities in subsets of circuits correspond with brief behavioral discontinuities during both sleep and wake. Our results suggest that the fundamental unit of state in the brain is consistent with the spatial and temporal scale of neuronal computation, and that this resolution can contribute to an understanding of cognition and behavior.

neuroscience↗

Circuit-specific selective vulnerability in the DMN persists in the face of widespread amyloid burden.

The relationship between brainwide functional decline and accumulation of pathological protein aggregates in Alzheimers disease (AD) is complex and not well understood. A set of highly interconnected cortical regions known as the default mode network (DMN) exhibits selective vulnerability to both functional decline and amyloid beta (A{beta}) plaques in early AD. One possibility is that early A{beta} accumulation in the DMN drives vulnerability. However, it is unknown whether there is something intrinsic to neuronal projections within the DMN that biases these circuits towards dysfunction. Here we directly test this hypothesis using long-term recordings of the spiking activity of ensembles of single units in freely behaving mice characterized by global cortical and hippocampal A{beta} burden (APP/PS1). Specifically, we track the interactions of a population of neurons within a DMN region and two additional populations that comprise monosynaptic targets, one within and the other outside the DMN. In addition, we record single neurons in hippocampus and examine interactions between the in-DMN and out-DMN cortical circuits triggered on hippocampal sharp-wave ripples, stereotyped hippocampal events that contribute to memory consolidation in the cortex. We examine the statistics of local activity as well as inter-regional communication in a region, genotype, and brain-state dependent manner. Our data reveal dysfunction restricted to the in-DMN projecting circuit. In contrast, communication along neuronal projections that originate in the DMN but target an out-DMN population is equivalent in APP/PS1 and WT mice. Circuit dysfunction is most evident throughout sleep, and particularly disrupted within sharp-wave ripples. Summarily, our results indicate that, even in the face of transgene overexpression and widespread A{beta}, there is distinct intrinsic and selective vulnerability. This vulnerability to amyloidosis is circuit-specific and conditioned on target, and neither source nor amyloid burden. These data raise the possibility that neuronal function in the DMN is not universally vulnerable; DMN subnetworks whose interactions involve targets outside the DMN may be resilient to A{beta}.

neuroscience↗

Identification of activity-dependent EGR3 target genes reveals genes associated with DNA damage response and schizophrenia

Bioinformatics and network studies have identified the immediate early gene transcription factor early growth response 3 (EGR3) as a master regulator of genes differentially expressed in the brains of patients with neuropsychiatric illnesses ranging from schizophrenia and bipolar disorder to Alzheimers disease. However, few studies have identified and validated Egr3-dependent genes in the mammalian brain. We have previously shown that Egr3 is required for stress-responsive behavior, memory, and hippocampal long-term depression in mice. To identify Egr3-dependent genes that may regulate these processes, we conducted an expression microarray on hippocampi from wildtype (WT) and Egr3-/- mice following electroconvulsive seizure (ECS), a stimulus that induces maximal expression of immediate early genes including Egr3. We identified 71 genes that were differentially expressed between WT and Egr3-/- mice one hour following ECS. Bioinformatic analyses showed that many of these are altered in schizophrenia. Ingenuity pathway analysis revealed the GADD45 (growth arrest and DNA-damage-inducible) family (Gadd45b, Gadd45g) as the leading category of differentially expressed genes. Together with differentially expressed genes in the AP-1 transcription factor family genes (Fos, Fosb), and the centromere organization protein Cenpa, these results revealed that Egr3 is required for activity-dependent expression of genes involved in the DNA damage response. Our findings implicate EGR3 as gene critical for the expression of genes that are disrupted in schizophrenia and reveal a novel requirement for EGR3 in the expression of genes involved in activity-induced DNA damage response.

neuroscience↗