Hummingbirds have a greatly enlarged hippocampal formation

Both field and laboratory studies demonstrate that hummingbirds (Apodiformes, Trochilidae) have exceptional spatial memory. The complexity of spatial–temporal information that hummingbirds must retain and use daily is probably subserved by the hippocampal formation (HF), and therefore, hummingbirds should have a greatly expanded HF. Here, we compare the relative size of the HF in several hummingbird species with that of other birds. Our analyses reveal that the HF in hummingbirds is significantly larger, relative to telencephalic volume, than any bird examined to date. When expressed as a percentage of telencephalic volume, the hummingbird HF is two to five times larger than that of caching and non-caching songbirds, seabirds and woodpeckers. This HF expansion in hummingbirds probably underlies their ability to remember the location, distribution and nectar content of flowers, but more detailed analyses are required to determine the extent to which this arises from an expansion of HF or a decrease in size of other brain regions.

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Offline ventral subiculum-ventral striatum serial communication is required for spatial memory consolidation

Nature Communications ◽

10.1038/s41467-019-13703-3 ◽

2019 ◽

Vol 10 (1) ◽

Cited By ~ 3

Author(s):

G. Torromino ◽

L. Autore ◽

V. Khalil ◽

V. Mastrorilli ◽

M. Griguoli ◽

...

Keyword(s):

Spatial Memory ◽

Memory Consolidation ◽

Ventral Striatum ◽

Spatial Information ◽

Hippocampal Formation ◽

Critical Role ◽

Brain Regions ◽

Complex Information ◽

Line Cross ◽

Insight Into

AbstractThe hippocampal formation is considered essential for spatial navigation. In particular, subicular projections have been suggested to carry spatial information from the hippocampus to the ventral striatum. However, possible cross-structural communication between these two brain regions in memory formation has thus far been unknown. By selectively silencing the subiculum–ventral striatum pathway we found that its activity after learning is crucial for spatial memory consolidation and learning-induced plasticity. These results provide new insight into the neural circuits underlying memory consolidation and establish a critical role for off-line cross-regional communication between hippocampus and ventral striatum to promote the storage of complex information.

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Intranasal administration of mitochondria improves spatial memory in olfactory bulbectomized mice

Experimental Biology and Medicine ◽

10.1177/15353702211056866 ◽

2021 ◽

pp. 153537022110568

Author(s):

Natalia V Bobkova ◽

Daria Y Zhdanova ◽

Natalia V Belosludtseva ◽

Nikita V Penkov ◽

Galina D Mironova

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Spatial Memory ◽

Intranasal Administration ◽

Brain Structures ◽

Brain Regions ◽

Dependent Manner ◽

Behavioral Experiments ◽

Hippocampal Cell Culture ◽

The Brain

Here, we found that functionally active mitochondria isolated from the brain of NMRI donor mice and administrated intranasally to recipient mice penetrated the brain structures in a dose-dependent manner. The injected mitochondria labeled with the MitoTracker Red localized in different brain regions, including the neocortex and hippocampus, which are responsible for memory and affected by degeneration in patients with Alzheimer's disease. In behavioral experiments, intranasal microinjections of brain mitochondria of native NMRI mice improved spatial memory in the olfactory bulbectomized (OBX) mice with Alzheimer’s type degeneration. Control OBX mice demonstrated loss of spatial memory tested in the Morris water maze. Immunocytochemical analysis revealed that allogeneic mitochondria colocalized with the markers of astrocytes and neurons in hippocampal cell culture. The results suggest that a non-invasive route intranasal administration of mitochondria may be a promising approach to the treatment of neurodegenerative diseases characterized, like Alzheimer's disease, by mitochondrial dysfunction.

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Hebbian plasticity in parallel synaptic pathways: A circuit mechanism for systems memory consolidation

PLoS Computational Biology ◽

10.1371/journal.pcbi.1009681 ◽

2021 ◽

Vol 17 (12) ◽

pp. e1009681

Author(s):

Michiel W. H. Remme ◽

Urs Bergmann ◽

Denis Alevi ◽

Susanne Schreiber ◽

Henning Sprekeler ◽

...

Keyword(s):

Memory Consolidation ◽

Computational Models ◽

Hippocampal Formation ◽

Spatial Scales ◽

Single Cells ◽

Brain Regions ◽

Quantitative Agreement ◽

Long Term Memory ◽

Hebbian Plasticity ◽

Mathematical Analyses

Systems memory consolidation involves the transfer of memories across brain regions and the transformation of memory content. For example, declarative memories that transiently depend on the hippocampal formation are transformed into long-term memory traces in neocortical networks, and procedural memories are transformed within cortico-striatal networks. These consolidation processes are thought to rely on replay and repetition of recently acquired memories, but the cellular and network mechanisms that mediate the changes of memories are poorly understood. Here, we suggest that systems memory consolidation could arise from Hebbian plasticity in networks with parallel synaptic pathways—two ubiquitous features of neural circuits in the brain. We explore this hypothesis in the context of hippocampus-dependent memories. Using computational models and mathematical analyses, we illustrate how memories are transferred across circuits and discuss why their representations could change. The analyses suggest that Hebbian plasticity mediates consolidation by transferring a linear approximation of a previously acquired memory into a parallel pathway. Our modelling results are further in quantitative agreement with lesion studies in rodents. Moreover, a hierarchical iteration of the mechanism yields power-law forgetting—as observed in psychophysical studies in humans. The predicted circuit mechanism thus bridges spatial scales from single cells to cortical areas and time scales from milliseconds to years.

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FMRI Investigation of Spatial Memory Abilities in Individuals Living With Schizophrenia Spectrum Disorders

10.32920/ryerson.14652849 ◽

2021 ◽

Author(s):

Leanne K. Wilkins

Keyword(s):

Spatial Memory ◽

Brain Regions ◽

Response Strategy ◽

Schizophrenia Spectrum Disorders ◽

Spatial Strategy ◽

Impaired Performance ◽

Starting Position ◽

Schizophrenia Spectrum ◽

Hippocampal Lesions ◽

Spectrum Disorders

Different strategies dependent on different brain regions may be spontaneously adopted to solve most spatial memory and navigation tasks. For this dissertation, I used brain-imaging and cognitive tasks to test the hypothesis that individuals living with schizophrenia spectrum disorders (SSD) have selective hippocampal-dependent spatial memory impairment. A hippocampal-dependent spatial strategy (locale/allocentric/cognitive map/viewpoint-independent) involves relying on learning the relations between landmarks in the environment, whereas a response strategy (taxon/egocentric/viewpoint-dependent) is more associated with caudate function and involves learning a sequence from a single starting position. In Experiment 1, I examined performance and brain activation with fMRI during the 4-on-8 virtual maze (4/8VM) to test the hypothesis of intact response versus impaired spatial memory in SSD. The SSD participants who adopted a spatial strategy performed more poorly and had less hippocampal activation than other groups. In Experiment 2, I further examined these data using multivariate PLS (partial least squares) analyses to identify whole-brain patterns of activation associated with group and strategy differences on the 4/8VM. Results revealed clusters of correlated activation within the temporal lobe unique to the SSD-Spatial group. The SSD Response group activated the same regions as the Healthy groups, but to a greater extent suggesting over-activation. In contrast to the between-subjects nature of strategy differences on the 4/8VM, for Experiment 3 I used the Courtyard Task to seek converging evidence of a selective hippocampal-dependent impairment in spatial memory using a within-subjects design. The Courtyard Task has previously demonstrated impaired performance among individuals with hippocampal lesions under shifted-view (allocentric) but not same-view (egocentric) conditions. Consistent with a profile of hippocampal dysfunction, the SSD group demonstrated a particular deficit under the shifted-view condition. The results support the development of protocols to train impaired hippocampal-dependent abilities and harness non-hippocampal dependent intact abilities. Overall, this dissertation provides valuable information characterizing spatial memory and highlights the importance of strategy use in SSD.

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Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1008 ◽

2015 ◽

Vol 282 (1810) ◽

pp. 20151008 ◽

Cited By ~ 25

Author(s):

Kristina Noreikiene ◽

Gábor Herczeg ◽

Abigél Gonda ◽

Gergely Balázs ◽

Arild Husby ◽

...

Keyword(s):

Body Size ◽

Brain Size ◽

Additive Genetic Variance ◽

Genetic Correlations ◽

Relative Size ◽

Strong Support ◽

Brain Evolution ◽

Brain Regions ◽

Independent Evolution ◽

Mosaic Model

The mosaic model of brain evolution postulates that different brain regions are relatively free to evolve independently from each other. Such independent evolution is possible only if genetic correlations among the different brain regions are less than unity. We estimated heritabilities, evolvabilities and genetic correlations of relative size of the brain, and its different regions in the three-spined stickleback ( Gasterosteus aculeatus ). We found that heritabilities were low (average h 2 = 0.24), suggesting a large plastic component to brain architecture. However, evolvabilities of different brain parts were moderate, suggesting the presence of additive genetic variance to sustain a response to selection in the long term. Genetic correlations among different brain regions were low (average r G = 0.40) and significantly less than unity. These results, along with those from analyses of phenotypic and genetic integration, indicate a high degree of independence between different brain regions, suggesting that responses to selection are unlikely to be severely constrained by genetic and phenotypic correlations. Hence, the results give strong support for the mosaic model of brain evolution. However, the genetic correlation between brain and body size was high ( r G = 0.89), suggesting a constraint for independent evolution of brain and body size in sticklebacks.

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Brain regions associated with visual cues are important for bird migration

Biology Letters ◽

10.1098/rsbl.2015.0678 ◽

2015 ◽

Vol 11 (11) ◽

pp. 20150678 ◽

Cited By ~ 11

Author(s):

Orsolya Vincze ◽

Csongor I. Vágási ◽

Péter L. Pap ◽

Gergely Osváth ◽

Anders Pape Møller

Keyword(s):

Visual Cues ◽

Optic Lobe ◽

Brain Size ◽

Relative Size ◽

Bird Species ◽

Interspecific Variation ◽

Brain Regions ◽

Long Distance ◽

Migration Distance ◽

Whole Brain

Long-distance migratory birds have relatively smaller brains than short-distance migrants or residents. Here, we test whether reduction in brain size with migration distance can be generalized across the different brain regions suggested to play key roles in orientation during migration. Based on 152 bird species, belonging to 61 avian families from six continents, we show that the sizes of both the telencephalon and the whole brain decrease, and the relative size of the optic lobe increases, while cerebellum size does not change with increasing migration distance. Body mass, whole brain size, optic lobe size and wing aspect ratio together account for a remarkable 46% of interspecific variation in average migration distance across bird species. These results indicate that visual acuity might be a primary neural adaptation to the ecological challenge of migration.

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Environmentally induced changes to brain morphology predict cognitive performance

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2017.0287 ◽

2018 ◽

Vol 373 (1756) ◽

pp. 20170287 ◽

Cited By ~ 10

Author(s):

Thomas W. Pike ◽

Michael Ramsey ◽

Anna Wilkinson

Keyword(s):

Cognitive Performance ◽

Optic Tectum ◽

Relative Size ◽

Brain Regions ◽

Cognitive Capacity ◽

Brain Morphology ◽

Chemical Information ◽

Brain Anatomy ◽

Short Term ◽

Olfactory Bulbs

The relationship between the size and structure of a species' brain and its cognitive capacity has long interested scientists. Generally, this work relates interspecific variation in brain anatomy with performance on a variety of cognitive tasks. However, brains are known to show considerable short-term plasticity in response to a range of social, ecological and environmental factors. Despite this, we have a remarkably poor understanding of how this impacts on an animal's cognitive performance. Here, we non-invasively manipulated the relative size of brain regions associated with processing visual and chemical information in fish (the optic tectum and olfactory bulbs, respectively). We then tested performance in a cognitive task in which information from the two sensory modalities was in conflict. Although the fish could effectively use both visual and chemical information if presented in isolation, when they received cues from both modalities simultaneously, those with a relatively better developed optic tectum showed a greater reliance on visual information, while individuals with relatively better developed olfactory bulbs showed a greater reliance on chemical information. These results suggest that short-term changes in brain structure, possibly resulting from an attempt to minimize the costs of developing unnecessary but energetically expensive brain regions, may have marked effects on cognitive performance. This article is part of the theme issue ‘Causes and consequences of individual differences in cognitive abilities’.

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Serotonin and panic

The British Journal of Psychiatry ◽

10.1192/bjp.172.6.465 ◽

1998 ◽

Vol 172 (6) ◽

pp. 465-471 ◽

Cited By ~ 67

Author(s):

C. J. Bell ◽

D. J. Nutt

Keyword(s):

Panic Disorder ◽

Selective Serotonin Reuptake Inhibitors ◽

Monoamine Oxidase Inhibitor ◽

Brain Regions ◽

Oxidase Inhibitor ◽

Tryptophan Depletion ◽

Laboratory Studies ◽

The Uk ◽

The Relationship

BackgroundTricyclic (TCA) and monoamine oxidase inhibitor (MAOI) antidepressants are effective in the treatment of panic disorder. Two selective serotonin reuptake inhibitors (SSRIs) have also been licensed in the UK for this indication and studies with three other SSRIs have recently been completed. These provide further evidence for the role of serotonin in panic.MethodReview of clinical, animal and laboratory studies.ResultsSSRIs have been shown to be effective in the treatment of panic disorder. The reported rates of improvement of 60–70% of patients taking SSRIs are similar to those seen withTCAs and greater than placebo. Other serotonergic agents do not appear to be effective. Animal work and human studies including measures of 5-HT in plasma, cerebrospinal fluid and platelets, challenge paradigms and tryptophan depletion show that the relationship between 5-HT and anxiety is complex.ConclusionClinical trials have shown that of all the serotonergic agents only the SSRIs are effective in panic disorder. They are as beneficial as the TCAs and seem to be better tolerated which may be particularly significant in view of the chronic nature of the condition. Serotonin plays a role in panic disorder and serotonergic dysfunction, however the results and evidence do not fit one theory alone. It is also likely that different brain regions and 5-HTreceptors are involved in specific ways.

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Homologous laminar organization of the mouse and human subiculum

10.1101/2019.12.20.883074 ◽

2019 ◽

Author(s):

Michael S. Bienkowski ◽

Farshid Sepehrband ◽

Nyoman D. Kurniawan ◽

Jim Stanis ◽

Laura Korobkova ◽

...

Keyword(s):

Gene Expression ◽

Hippocampal Formation ◽

Expression Patterns ◽

Pyramidal Cells ◽

Longitudinal Axis ◽

Brain Regions ◽

Brain Atlas ◽

Fiber Density ◽

Laminar Organization ◽

Hybridization Data

SummaryThe subiculum is the major output structure of the hippocampal formation and one of the brain regions most affected by Alzheimer’s disease. Our previous work revealed a hidden laminar architecture within the mouse subiculum. However, the rotation of the hippocampal longitudinal axis across species makes it unclear how the laminar organization is represented in human subiculum. Using in situ hybridization data from the Allen Human Brain Atlas, we demonstrate that the human subiculum also contains complementary laminar gene expression patterns similar to the mouse. In addition, we provide evidence that the molecular domain boundaries in human subiculum correspond to microstructural differences observed in high resolution MRI and fiber density imaging. Finally, we show both similarities and differences in the gene expression profile of subiculum pyramidal cells within homologous lamina. Overall, we present a new 3D model of the anatomical organization of human subiculum and its evolution from the mouse.

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