Causal evidence of a line attractor encoding an affective state.

Continuous attractors are an emergent property of neural population dynamics that have been hypothesized to encode continuous variables such as head direction and eye position1-4. In mammals, direct evidence of neural implementation of a continuous attractor has been hindered by the challenge of targeting perturbations to specific neurons within contributing ensembles2,3. Dynamical systems modelling has revealed that neurons in the hypothalamus exhibit approximate line-attractor dynamics in male mice during aggressive encounters5. We have previously hypothesized that these dynamics may encode the variable intensity and persistence of an aggressive internal state. Here we report that these neurons also showed line-attractor dynamics in head-fixed mice observing aggression6. This allowed us to identify and manipulate line-attractor-contributing neurons using two-photon calcium imaging and holographic optogenetic perturbations. On-manifold perturbations yielded integration of optogenetic stimulation pulses and persistent activity that drove the system along the line attractor, while transient off-manifold perturbations were followed by rapid relaxation back into the attractor. Furthermore, single-cell stimulation and imaging revealed selective functional connectivity among attractor-contributing neurons. Notably, individual differences among mice in line-attractor stability were correlated with the degree of functional connectivity among attractor-contributing neurons. Mechanistic recurrent neural network modelling indicated that dense subnetwork connectivity and slow neurotransmission7 best recapitulate our empirical findings. Our work bridges circuit and manifold levels3, providing causal evidence of continuous attractor dynamics encoding an affective internal state in the mammalian hypothalamus.

Evaluation of a Photo Captioning Cognitive Empathy Intervention for Dementia Caregivers.

OBJECTIVES: The goal of this study was to develop and evaluate an intervention aimed at increasing cognitive empathy, improving mental health, and reducing inflammation in dementia caregivers, and to examine the relevant neural and psychological mechanisms. METHODS: Twenty dementia caregivers completed an intervention that involved taking 3-5 daily photographs of their person living with dementia (PLWD) over a period of 10 days and captioning those photos with descriptive text capturing the inner voice of the PLWD. Both before and after the intervention, participants completed questionnaires, provided a blood sample for measures of inflammation, and completed a neuroimaging session to measure their neural response to viewing photographs of their PLWD and others. RESULTS: 87% of enrolled caregivers completed the intervention. Caregivers experienced pre- to post-intervention increases in cognitive empathy (i.e. Perspective-Taking) and decreases in both burden and anxiety. These changes were paralleled by an increased neural response to photographs of their PLWD within brain regions implicated in cognitive empathy. CONCLUSION: These findings warrant a larger replication study that includes a control condition and follows participants to establish the duration of the intervention effects. CLINICAL IMPLICATIONS: Cognitive empathy interventions may improve caregiver mental health and are worthy of further investigation.

Elastic Shape Morphing of Ultralight Structures by Programmable Assembly.

Ultralight materials present an opportunity to dramatically increase the efficiency of load-bearing aerostructures. To date, however, these ultralight materials have generally been confined to the laboratory bench-top, due to dimensional constraints of the manufacturing processes. We show a programmable material system applied as a large-scale, ultralight, and conformable aeroelastic structure. The use of a modular, lattice-based, ultralight material results in stiffness typical of an elastomer (2.6 MPa) at a mass density typical of an aerogel (5.6 m g c m 3 ). This, combined with a building block based manufacturing and configuration strategy, enables the rapid realization of new adaptive structures and mechanisms. The heterogeneous design with programmable anisotropy allows for enhanced elastic and global shape deformation in response to external loading, making it useful for tuned fluid-structure interaction. We demonstrate an example application experiment using two building block types for the primary structure of a 4.27m wingspan aircraft, where we spatially program elastic shape morphing to increase aerodynamic efficiency and improve roll control authority, demonstrated with full-scale wind tunnel testing.