Brain imaging reveals neuronal circuitry underlying the crow's perception of human faces.

Crows pay close attention to people and can remember specific faces for several years after a single encounter. In mammals, including humans, faces are evaluated by an integrated neural system involving the sensory cortex, limbic system, and striatum. Here we test the hypothesis that birds use a similar system by providing an imaging analysis of an awake, wild animal's brain as it performs an adaptive, complex cognitive task. We show that in vivo imaging of crow brain activity during exposure to familiar human faces previously associated with either capture (threatening) or caretaking (caring) activated several brain regions that allow birds to discriminate, associate, and remember visual stimuli, including the rostral hyperpallium, nidopallium, mesopallium, and lateral striatum. Perception of threatening faces activated circuitry including amygdalar, thalamic, and brainstem regions, known in humans and other vertebrates to be related to emotion, motivation, and conditioned fear learning. In contrast, perception of caring faces activated motivation and striatal regions. In our experiments and in nature, when perceiving a threatening face, crows froze and fixed their gaze (decreased blink rate), which was associated with activation of brain regions known in birds to regulate perception, attention, fear, and escape behavior. These findings indicate that, similar to humans, crows use sophisticated visual sensory systems to recognize faces and modulate behavioral responses by integrating visual information with expectation and emotion. Our approach has wide applicability and potential to improve our understanding of the neural basis for animal behavior.

Development of a 213Bi-Labeled Pyridyl Benzofuran for Targeted α-Therapy of Amyloid-ß Aggregates.

Alzheimer disease is a neurodegenerative disorder with limited treatment options. It is characterized by the presence of several biomarkers, including amyloid-ß aggregates, which lead to oxidative stress and neuronal decay. Targeted α-therapy (TAT) has been shown to be efficacious against metastatic cancer. TAT takes advantage of tumor-localized α-particle emission to break disease-associated covalent bonds while minimizing radiation dose to healthy tissues due to the short, micrometer-level, distances traveled. We hypothesized that TAT could be used to break covalent bonds within amyloid-ß aggregates and facilitate natural plaque clearance mechanisms. Methods: We synthesized a 213Bi-chelate-linked benzofuran pyridyl derivative (BiBPy) and generated [213Bi]BiBPy, with a specific activity of 120.6 GBq/µg, dissociation constant of 11 ± 1.5 nM, and logP of 0.14 ± 0.03. Results: As the first step toward the validation of [213Bi]BiBPy as a TAT agent for the reduction of Alzheimer disease-associated amyloid-ß, we showed that brain homogenates from APP/PS1 double-transgenic male mice (6-9 mo old) incubated with [213Bi]BiBPy exhibited a marked reduction in amyloid-ß plaque concentration as measured using both enzyme-linked immunosorbent and Western blotting assays, with a half-maximal effective concentration of 3.72 kBq/pg. Conclusion: This [213Bi]BiBPy-concentration-dependent activity shows that TAT can reduce amyloid plaque concentration in vitro and supports the development of targeting systems for in vivo validations.

Distinct neural circuits underlie assessment of a diversity of natural dangers by American crows.

Social animals encountering natural dangers face decisions such as whether to freeze, flee or harass the threat. The American crow, Corvus brachyrhynchos, conspicuously mobs dangers. We used positron emission tomography to test the hypothesis that distinct neuronal substrates underlie the crow's consistent behavioural response to different dangers. We found that crows activated brain regions associated with attention and arousal (nucleus isthmo-opticus/locus coeruleus), and with motor response (arcopallium), as they fixed their gaze on a threat. However, despite this consistent behavioural and neural response, the sight of a person who previously captured the crow, a person holding a dead crow and a taxidermy-mounted hawk activated distinct forebrain regions (amygdala, hippocampus and portion of the caudal nidopallium, respectively). We suggest that aspects of mobbing behaviour are guided by unique neural circuits that respond to differences in mental processing-learning, memory formation and multisensory discrimination-required to appropriately nuance a risky behaviour to specific dangers.

Brain Trauma Imaging.

Imaging of mild traumatic brain injury (TBI) using conventional techniques such as CT or MRI often results in no specific imaging correlation that would explain cognitive and clinical symptoms. Molecular imaging of mild TBI suggests that secondary events after injury can be detected using PET. However, no single specific pattern emerges that can aid in diagnosing the injury or determining the prognosis of the long-term behavioral profiles, indicating the heterogeneous and diffuse nature of TBI. Chronic traumatic encephalopathy, a primary tauopathy, has been shown to be strongly associated with repetitive TBI. In vivo data on the available tau PET tracers, however, have produced mixed results and overall low retention profiles in athletes with a history of repetitive mild TBI. Here, we emphasize that the lack of a mechanistic understanding of chronic TBI has posed a challenge when interpreting the results of molecular imaging biomarkers. We advocate for better target identification, improved analysis techniques such as machine learning or artificial intelligence, and novel tracer development.

American crows that excel at tool use activate neural circuits distinct from less talented individuals.

Tools enable animals to exploit and command new resources. However, the neural circuits underpinning tool use and how neural activity varies with an animal's tool proficiency, are only known for humans and some other primates. We use 18F-fluorodeoxyglucose positron emission tomography to image the brain activity of naïve vs trained American crows (Corvus brachyrhynchos) when presented with a task requiring the use of stone tools. As in humans, talent affects the neural circuits activated by crows as they prepare to execute the task. Naïve and less proficient crows use neural circuits associated with sensory- and higher-order processing centers (the mesopallium and nidopallium), while highly proficient individuals increase activity in circuits associated with motor learning and tactile control (hippocampus, tegmentum, nucleus basorostralis, and cerebellum). Greater proficiency is found primarily in adult female crows and may reflect their need to use more cognitively complex strategies, like tool use, to obtain food.

Evaluation of 3-dimensional stereotactic surface projection rendering of arterial spin labeling data in a clinical cohort.

BACKGROUND AND PURPOSE: To assess the feasibility of 3-dimensional stereotactic surface projection (3D-SSP) as applied to arterial spin labeling (ASL) in a clinical pilot study. METHODS: A retrospective sample of 10 consecutive patients who underwent ASL as part of a clinically indicated MR examination was collected during this pilot study. Five additional subjects with normal cerebral perfusion served as a control group. Following voxel-wise M0-correction, cerebral blood flow (CBF) quantification, and stereotactic anatomic standardization, voxel-wise CBF from an individual's ASL dataset was extracted to a set of predefined surface pixels (3D-SSP). A normal database was created from averaging the extracted CBF datasets of the control group. Patients' datasets were compared individually with the normal database by calculating a Z-score on a pixel-by-pixel basis and were displayed in 3D-SSP views for visual inspection. Independent, two-expert reader assessment, using a 3-point scale, compared standard quantitative CBF images to the 3D-SSP maps. RESULTS: Patterns and severities of regionally reduced CBF were identified, by both independent readers, in the 3D-SSP maps. Reader assessment demonstrated preference for 3D-SSP over traditionally displayed standard quantitative CBF images in three of four evaluated imaging metrics (p = .026, .031, and .013, respectively); 3D-SSP maps were never found to be inferior to the standard quantitative CBF images. CONCLUSIONS: Three-dimensional SSP maps are feasible in a clinical population and enable quantitative data extraction and localization of perfusion abnormalities by means of stereotactic coordinates in a condensed display. The proposed method is a promising approach for interpreting cerebrovascular pathophysiology.

Artificial Intelligence for Brain Molecular Imaging.

AI has been applied to brain molecular imaging for over 30 years. The past two decades, have seen explosive progress. AI applications span from operations processes such as attenuation correction and image generation, to disease diagnosis and prediction. As sophistication in AI software platforms increases, and the availability of large imaging data repositories become common, future studies will incorporate more multidimensional datasets and information that may truly reach "superhuman" levels in the field of brain imaging. However, even with a growing level of complexity, these advanced networks will still require human supervision for appropriate application and interpretation in medical practice.

Deep-learning prediction of amyloid deposition from early-phase amyloid positron emission tomography imaging.

OBJECTIVE: While the use of biomarkers for the detection of early and preclinical Alzheimer's Disease has become essential, the need to wait for over an hour after injection to obtain sufficient image quality can be challenging for patients with suspected dementia and their caregivers. This study aimed to develop an image-based deep-learning technique to generate delayed uptake patterns of amyloid positron emission tomography (PET) images using only early-phase images obtained from 0-20 min after radiotracer injection. METHODS: We prepared pairs of early and delayed [11C]PiB dynamic images from 253 patients (cognitively normal n = 32, fronto-temporal dementia n = 39, mild cognitive impairment n = 19, Alzheimer's disease n = 163) as a training dataset. The neural network was trained with the early images as the input, and the output was the corresponding delayed image. A U-net convolutional neural network (CNN) and a conditional generative adversarial network (C-GAN) were used for the deep-learning architecture and the data augmentation methods, respectively. Then, an independent test data set consisting of early-phase amyloid PET images (n = 19) was used to generate corresponding delayed images using the trained network. Two nuclear medicine physicians interpreted the actual delayed images and predicted delayed images for amyloid positivity. In addition, the concordance of the actual delayed and predicted delayed images was assessed statistically. RESULTS: The concordance of amyloid positivity between the actual versus AI-predicted delayed images was 79%(κ = 0.60) and 79% (κ = 0.59) for each physician, respectively. In addition, the physicians' agreement rate was at 89% (κ = 0.79) when the same image was interpreted. And, the actual versus AI-predicted delayed images were not readily distinguishable (correct answer rate, 55% and 47% for each physician, respectively). The statistical comparison of the actual versus the predicted delated images indicated that the peak signal-to-noise ratio (PSNR) was 21.8 dB ± 2.2 dB, and the structural similarity index (SSIM) was 0.45 ± 0.04. CONCLUSION: This study demonstrates the feasibility of an image-based deep-learning framework to predict delayed patterns of Amyloid PET uptake using only the early phase images. This AI-based image generation method has the potential to reduce scan time for amyloid PET and increase the patient throughput, without sacrificing diagnostic accuracy for amyloid positivity.

Cerebrocerebellar hypometabolism associated with repetitive blast exposure mild traumatic brain injury in 12 Iraq war Veterans with persistent post-concussive symptoms.

Disagreement exists regarding the extent to which persistent post-concussive symptoms (PCS) reported by Iraq combat Veterans with repeated episodes of mild traumatic brain injury (mTBI) from explosive blasts represent structural or functional brain damage or an epiphenomenon of comorbid depression or posttraumatic stress disorder (PTSD). Objective assessment of brain function in this population may clarify the issue. To this end, twelve Iraq war Veterans (32.0 ± 8.5 [mean ± standard deviation (SD)] years of age) reporting one or more blast exposures meeting American Congress of Rehabilitation Medicine criteria for mTBI and persistent PCS and 12 cognitively normal community volunteers (53.0 ± 4.6 years of age) without history of head trauma underwent brain fluorodeoxyglucose positron emission tomography (FDG-PET) and neuropsychological assessments and completed PCS and psychiatric symptom rating scales. Compared to controls, Veterans with mTBI (with or without PTSD) exhibited decreased cerebral metabolic rate of glucose in the cerebellum, vermis, pons, and medial temporal lobe. They also exhibited subtle impairments in verbal fluency, cognitive processing speed, attention, and working memory, similar to those reported in the literature for patients with cerebellar lesions. These FDG-PET imaging findings suggest that regional brain hypometabolism may constitute a neurobiological substrate for chronic PCS in Iraq combat Veterans with repetitive blast-trauma mTBI. Given the potential public health implications of these findings, further investigation of brain function in these Veterans appears warranted.

American Crow Brain Activity in Response to Conspecific Vocalizations Changes When Food Is Present.

Social interaction among animals can occur under many contexts, such as during foraging. Our knowledge of the regions within an avian brain associated with social interaction is limited to the regions activated by a single context or sensory modality. We used 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to examine American crow (Corvus brachyrhynchos) brain activity in response to conditions associated with communal feeding. Using a paired approach, we exposed crows to either a visual stimulus (the sight of food), an audio stimulus (the sound of conspecifics vocalizing while foraging) or both audio/visual stimuli presented simultaneously and compared to their brain activity in response to a control stimulus (an empty stage). We found two regions, the nucleus taenia of the amygdala (TnA) and a medial portion of the caudal nidopallium, that showed increased activity in response to the multimodal combination of stimuli but not in response to either stimulus when presented unimodally. We also found significantly increased activity in the lateral septum and medially within the nidopallium in response to both the audio-only and the combined audio/visual stimuli. We did not find any differences in activation in response to the visual stimulus by itself. We discuss how these regions may be involved in the processing of multimodal stimuli in the context of social interaction.

Intranasal Paclitaxel Alters Alzheimer's Disease Phenotypic Features in 3xTg-AD Mice.

BACKGROUND: Microtubule stabilizing drugs, commonly used as anti-cancer therapeutics, have been proposed for treatment of Alzheimer's disease (AD); however, many do not cross the blood-brain barrier. OBJECTIVE: This research investigated if paclitaxel (PTX) delivered via the intranasal (IN) route could alter the phenotypic progression of AD in 3xTg-AD mice. METHODS: We administered intranasal PTX in 3XTg-AD mice (3xTg-AD n = 15, 10 weeks and n = 10, 44 weeks, PTX: 0.6 mg/kg or 0.9%saline (SAL)) at 2-week intervals. After treatment, 3XTg-AD mice underwent manganese-enhanced magnetic resonance imaging to measure in vivo axonal transport. In a separate 3XTg-AD cohort, PTX-treated mice were tested in a radial water tread maze at 52 weeks of age after four treatments, and at 72 weeks of age, anxiety was assessed by an elevated-plus maze after 14 total treatments. RESULTS: PTX increased axonal transport rates in treated 3XTg-AD compared to controls (p≤0.003). Further investigation using an in vitro neuron model of Aß-induced axonal transport disruption confirmed PTX prevented axonal transport deficits. Confocal microscopy after treatment found fewer phospho-tau containing neurons (5.25±3.8 versus 8.33±2.5, p < 0.04) in the CA1, altered microglia, and reduced reactive astrocytes. PTX improved performance of 3xTg-AD on the water tread maze compared to controls and not significantly different from WT (Day 5, 143.8±43 versus 91.5±77s and Day 12, 138.3±52 versus 107.7±75s for SAL versus PTX). Elevated plus maze revealed that PTX-treated 3xTg-AD mice spent more time exploring open arms (Open arm 129.1±80 versus 20.9±31s for PTX versus SAL, p≤0.05). CONCLUSION: Taken collectively, these findings indicate that intranasal-administered microtubule-stabilizing drugs may offer a potential therapeutic option for treating AD.

Technical Note: Quantification of blood-spinal cord barrier permeability after application of magnetic resonance-guided focused ultrasound in spinal cord injury.

PURPOSE: To demonstrate that magnetic resonance-guided focused ultrasound (MRgFUS) facilitates blood-spinal cord barrier (BSCB) permeability and develop observer-independent MRI quantification of BSCB permeability after MRgFUS for spinal cord injury (SCI). METHODS: Noninjured Sprague-Dawley rats (n = 3) underwent MRgFUS and were administered Evans blue post-MRgFUS to confirm BSCB opening. Absorbance was measured by spectrophotometry and correlated with its corresponding image intensity. Rats (n = 21) underwent T8-T10 laminectomy and extradural compression of the spinal cord (23g weighted aneurysm-type clip, 1 min). The intervention group (n = 11) was placed on a preclinical MRgFUS system, administered microbubbles (Optison, 0.2 mL/kg), and received 3 MRgFUS sonications (25 ms bursts, 1 Hz pulses for 3 min, 3 acoustic W, approximately 1.0-2.1 MPa peak pressure as measured via hydrophone). The sham group (n = 10) received equivalent procedures with no sonications. T1w MRI was obtained both pre- and post-MRgFUS BSCB opening. Spinal cords were segmented manually or semiautomatically and a Pearson correlation with P ≤ 0.001 was used to correlate the two segmentation methods. MRgFUS sonication and control regions intensity values were evaluated with a paired t-test with a P ≤ 0.01. RESULTS: Semiautomatic segmentation reduced computational time by 95% and was correlated with manual segmentation (Pearson = 0.92, P < 0.001, n = 71 regions). In the noninjured rat group, Evans blue absorbance correlated with image intensity in the MRgFUS and control regions (Pearson = 0.82, P = 0.02, n = 6). In rats that underwent the SCI procedure, an increase in signal intensity in the MRgFUS targeted region relative to control was seen in all SCI rats (10.65 ± 12.4%, range: 0.96-43.9%, n = 11, P = 0.002). SCI sham MRgFUS revealed no change (0.63 ± 0.52%, 95% CI 0.320.95, n = 10). This result was significant between both groups (P = 0.003). CONCLUSION: The implemented semiautomatic segmentation procedure improved data analysis efficiency. Quantitative methods using contrast-enhanced MRI with histological validation are sensitive for detection of blood-spinal cord barrier opening induced by magnetic resonance-guided focused ultrasound.

Brain activity underlying American crow processing of encounters with dead conspecifics.

Animals utilize a variety of auditory and visual cues to navigate the landscape of fear. For some species, including corvids, dead conspecifics appear to act as one such visual cue of danger, and prompt alarm calling by attending conspecifics. Which brain regions mediate responses to dead conspecifics, and how this compares to other threats, has so far only been speculative. Using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) we contrast the metabolic response to visual and auditory cues associated with a dead conspecific among five a priori selected regions in the American crow (Corvus brachyrhynchos) brain: the hippocampus, nidopallium caudolaterale, striatum, amygdala, and the septum. Using a repeated-measures, fully balanced approach, we exposed crows to four stimuli: a dead conspecific, a dead song sparrow (Melospiza melodia), conspecific alarm calls given in response to a dead crow, and conspecific food begging calls. We find that in response to observations of a dead crow, crows show significant activity in areas associated with higher-order decision-making (NCL), but not in areas associated with social behaviors or fear learning. We do not find strong differences in activation between hearing alarm calls and food begging calls; both activate the NCL. Lastly, repeated exposures to negative stimuli had a marginal effect on later increasing the subjects' brain activity in response to control stimuli, suggesting that crows might quickly learn from negative experiences.

Chronic elevation of plasma vascular endothelial growth factor-A (VEGF-A) is associated with a history of blast exposure.

Mounting evidence points to the significance of neurovascular-related dysfunction in veterans with blast-related mTBI, which is also associated with reduced [18F]-fluorodeoxyglucose (FDG) uptake. The goal of this study was to determine whether plasma VEGF-A is altered in veterans with blast-related mTBI and address whether VEGF-A levels correlate with FDG uptake in the cerebellum, a brain region that is vulnerable to blast-related injury 72 veterans with blast-related mTBI (mTBI) and 24 deployed control (DC) veterans with no lifetime history of TBI were studied. Plasma VEGF-A was significantly elevated in mTBIs compared to DCs. Plasma VEGF-A levels in mTBIs were significantly negatively correlated with FDG uptake in cerebellum. In addition, performance on a Stroop color/word interference task was inversely correlated with plasma VEGF-A levels in blast mTBI veterans. Finally, we observed aberrant perivascular VEGF-A immunoreactivity in postmortem cerebellar tissue and not cortical or hippocampal tissues from blast mTBI veterans. These findings add to the limited number of plasma proteins that are chronically elevated in veterans with a history of blast exposure associated with mTBI. It is likely the elevated VEGF-A levels are from peripheral sources. Nonetheless, increasing plasma VEGF-A concentrations correlated with chronically decreased cerebellar glucose metabolism and poorer performance on tasks involving cognitive inhibition and set shifting. These results strengthen an emerging view that cognitive complaints and functional brain deficits caused by blast exposure are associated with chronic blood-brain barrier injury and prolonged recovery in affected regions.

Paclitaxel Reduces Brain Injury from Repeated Head Trauma in Mice.

Repetitive mild traumatic brain injury (rmTBI) is known to disturb axonal integrity and may play an important role in the pathogenic cascades leading to neurodegeneration. One critical approach to reduce the future onset of neurodegeneration is to intervene in this process at an early stage following a brain injury. Previously we showed that direct application of the microtubule-stabilizing drug, paclitaxel, on the brain following controlled cortical impact improved motor function and reduced lesion size. Herein, we extended these findings to a model of mild brain injury induced by repeated closed-skull impacts. Paclitaxel was administered intranasally to circumvent its poor transport across the blood-brain barrier. Mice received five mild closed-skull impacts (one per day for five days). Intranasal paclitaxel was administered once only, immediately after the first impact. We found that paclitaxel prevented injury-induced deficits in a spatial memory task in a water tread maze. In vivo magnetic resonance imaging (MRI) and positron emission tomography with 18F-flurodeoxyglucose (FDG-PET) revealed that paclitaxel prevented structural injury and hypometabolism. On MRI, apparent, injury-induced microbleeds were observed in 100% of vehicle-treated rmTBI mice, but not in paclitaxel-treated subjects. FDG-PET revealed a 42% increase in whole brain glucose metabolism in paclitaxel-treated mice as compared to vehicle-treated rmTBI. Immunohistochemistry found reduced evidence of axonal injury and synaptic loss. Our results indicate that intranasal paclitaxel administration imparts neuroprotection against brain injury and cognitive impairment in mice. The results from this study support the idea that microtubule-stabilization strategies hold therapeutic promise in mitigating traumatic brain injury.

A unique representation of heat allodynia in the human brain.

Skin inflammation causes innocuous heat to become painful. This condition, called heat allodynia, is a common feature of pathological pain states. Here, we show that heat allodynia is functionally and neuroanatomically distinct from normal heat pain. We subtracted positron emission tomography scans obtained during painful heating of normal skin from scans during equally intense but normally innocuous heating of capsaicin-treated skin. This comparison reveals the specific activation of a medial thalamic pathway to the frontal lobe during heat allodynia. The results suggest that different central pathways mediate the intensity and certain qualitative aspects of pain. In making this differentiation, the brain recognizes unique physiological features of different painful conditions, thus permitting adaptive responses to different pain states.

Assessing Spatial Memory Impairment in a Mouse Model of Traumatic Brain Injury Using a Radial Water Tread Maze.

Despite the recent increase in use of mouse models in scientific research, researchers continue to use cognitive tasks that were originally designed and validated for rat use. The Radial Water Tread (RWT) maze test of spatial memory (designed specifically for mice and requiring no swimming) has been shown previously to successfully distinguish between controlled cortical impact-induced TBI mice and sham controls. Here, a detailed protocol for this task is presented. The RWT maze capitalizes on the natural tendency of mice to avoid open areas in favor of hugging the sides of an apparatus (thigmotaxis). The walls of the maze are lined with nine escape holes placed above the floor of the apparatus, and mice are trained to use visual cues to locate the escape hole that leads out of the maze. The maze is filled with an inch of cold water, sufficient to motivate escape but not deep enough to require that the mouse swim. The acquisition period takes only four training days, with a test of memory retention on day five and a long-term memory test on day 12. The results reported here suggest that the RWT maze is a feasible alternative to rat-validated, swimming-based cognitive tests in the assessment of spatial memory deficits in mouse models of TBI.

Magnetic resonance imaging-guided focused ultrasound to increase localized blood-spinal cord barrier permeability.

Spinal cord injury (SCI) affects thousands of people every year in the USA, and most patients are left with some permanent paralysis. Therapeutic options are limited and only modestly affect outcome. To address this issue, we used magnetic resonance imaging-guided focused ultrasound (MRgFUS) as a non-invasive approach to increase permeability in the blood-spinal cord barrier (BSCB). We hypothesize that localized, controlled sonoporation of the BSCB by MRgFUS will aid delivery of therapeutics to the injury. Here, we report our preliminary findings for the ability of MRgFUS to increase BSCB permeability in the thoracic spinal cord of a normal rat model. First, an excised portion of normal rat spinal column was used to characterize the acoustic field and to estimate the insertion losses that could be expected in an MRgFUS blood spinal cord barrier opening. Then, in normal rats, MRgFUS was applied in combination with intravenously administered microbubbles to the spinal cord region. Permeability of the BSCB was indicated as signal enhancement by contrast administered prior to T1-weighted magnetic resonance imaging and verified by Evans blue dye. Neurological testing using the Basso, Beattie, and Breshnahan scale and the ladder walk was normal in 8 of 10 rats tested. Two rats showed minor impairment indicating need for further refinement of parameters. No gross tissue damage was evident by histology. In this study, we have opened successfully the blood spinal cord barrier in the thoracic region of the normal rat spine using magnetic resonance-guided focused ultrasound combined with microbubbles.