Differential effects of high-fat diet on endocrine, metabolic and depressive-like behaviors in male and female rats.

The complications of obesity extend beyond the periphery to the central nervous system (CNS) and include an increased risk of developing neuropsychiatric co-morbidities like depressive illness. Preclinical studies support this concept, including studies that have examined the effects of a high-fat diet (HFD) on depressive-like behaviors. Although women are approximately two-fold more likely to develop depressive illness compared to men, most preclinical studies have focused on the effects of HFD in male rodents. Accordingly, the goal of this study was to examine depressive-like behaviors in male and female rats provided access to a HFD. In agreement with prior studies, male and female rats provided a HFD segregate into an obesity phenotype (i.e., diet-induced obesity; DIO) or a diet resistant (DR) phenotype. Upon confirmation of the DR and DIO phenotypes, behavioral assays were performed in control chow, DR, and DIO rats. In the sucrose preference test, male DIO rats exhibited significant decreases in sucrose consumption (i.e., anhedonia) compared to male DR and male control rats. In the forced swim test (FST), male DIO rats exhibited increases in immobility and decreases in climbing behaviors in the pre-test sessions. Interestingly, male DR rats exhibited these same changes in both the pre-test and test sessions of the FST, suggesting that consumption of a HFD, even in the absence of the development of an obesity phenotype, has behavioral consequences. Female rats did not exhibit differences in sucrose preference, but female DIO rats exhibited increases in immobility exclusively in the test session of the FST, behavioral changes that were not affected by the stage of the estrous cycle. Collectively, these studies demonstrate that access to a HFD elicits different behavioral outcomes in male and female rats.

Pyridostigmine bromide elicits progressive and chronic impairments in the cholinergic anti-inflammatory pathway in the prefrontal cortex and hippocampus of male rats.

Gulf War Illness (GWI) is a multi-symptom illness that continues to affect over 250,000 American Gulf War veterans. The causes of GWI remain equivocal; however, prophylactic use of the acetylcholinesterase inhibitor pyridostigmine bromide (PB), and the stress of combat have been identified as two potential causative factors. Both PB and stress alter acetylcholine (ACh), which mediates both cognition and anti-inflammatory responses. As inflammation has been proposed to contribute to the cognitive deficits and immune dysregulation in GWI, the goal of this study was to determine the long-term effects of PB and stress on the cholinergic anti-inflammatory pathway in the central nervous system and periphery. We used our previously established rat model of GWI and in vivo microdialysis to assess cholinergic neurochemistry in the prefrontal cortex (PFC) and hippocampus following a mild immune challenge (lipopolysaccharide; LPS). We then examined LPS-induced changes in inflammatory markers in PFC and hippocampal homogenates. We found that PB treatment produces a long-lasting potentiation of the cholinergic response to LPS in both the PFC and hippocampus. Interestingly, this prolonged effect of PB treatment enhancing cholinergic responses to LPS was accompanied by paradoxical increases in the release of pro-inflammatory cytokines in these brain regions. Collectively, these findings provide evidence that neuroinflammation resulting from dysregulation of the cholinergic anti-inflammatory pathway is a mechanistic mediator in the progression of the neurochemical and neurocognitive deficits in GWI and more broadly suggest that dysregulation of this pathway may contribute to neuroinflammatory processes in stress-related neurological disorders.

Hippocampal-specific insulin resistance elicits behavioral despair and hippocampal dendritic atrophy.

Insulin resistance is a major contributor to the neuroplasticity deficits observed in patients with metabolic disorders. However, the relative contribution of peripheral versus central insulin resistance in the development of neuroplasticity deficits remains equivocal. To distinguish between peripheral and central insulin resistance, we developed a lentiviral vector containing an antisense sequence selective for the insulin receptor (LV-IRAS). We previously demonstrated that intra-hippocampal injection of this vector impairs synaptic transmission and hippocampal-dependent learning and memory in the absence of peripheral insulin resistance. In view of the increased risk for the development of neuropsychiatric disorders in patients with insulin resistance, the current study examined depressive and anxiety-like behaviors, as well as hippocampal structural plasticity in rats with hippocampal-specific insulin resistance. Following hippocampal administration of either the LV-control virus or the LV-IRAS, anhedonia was evaluated by the sucrose preference test, despair behavior was assessed in the forced swim test, and anxiety-like behaviors were determined in the elevated plus maze. Hippocampal neuron morphology was studied by Golgi-Cox staining. Rats with hippocampal insulin resistance exhibited anxiety-like behaviors and behavioral despair without differences in anhedonia, suggesting that some but not all components of depressive-like behaviors were affected. Morphologically, hippocampal-specific insulin resistance elicited atrophy of the basal dendrites of CA3 pyramidal neurons and dentate gyrus granule neurons, and also reduced the expression of immature dentate gyrus granule neurons. In conclusion, hippocampal-specific insulin resistance elicits structural deficits that are accompanied by behavioral despair and anxiety-like behaviors, identifying hippocampal insulin resistance as a key factor in depressive illness.

Danish translation and validation of the Self-reported foot and ankle score (SEFAS) in patients with ankle related fractures.

BACKGROUND: The Self-reported Foot and Ankle Score (SEFAS) is a patient-reported outcome measure used to evaluate foot and ankle disorders. The purpose of this study was to translate, cross-culturally adapt and validate the Danish language version of the SEFAS in patients with ankle-related fractures. METHODS: Forward-backward translation, cross-cultural adaption and validation were performed. In total, 125 patients completed the SEFAS-DK and the Danish version of American Orthopaedic Foot and Ankle Score (AOFAS-DK) at three time points after the date of fracture. The evaluation was performed according to the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) guidelines. RESULTS: The intra-class correlation coefficient (ICC) level of the SEFAS-DK total score was 0.93 (95% confidence interval [CI]: 0.88-0.96). Cronbach's alpha (CA) for the SEFAS-DK was 0.93, while the floor and ceiling effect at week 6 post-injury was 22.4%. Construct validity was correlated with the AOFAS, and >75% of the pre-defined hypotheses could be confirmed. Responsiveness was analysed using longitudinal data. The minimal clinical important change (MCIC) showed that the SEFAS-DK detects changes in physical function over time. CONCLUSION: The Danish version of the SEFAS showed overall good reliability, validity and responsiveness. SEFAS-DK can be used to evaluate physical function in patients with ankle-related fractures. LEVEL OF EVIDENCE: level II, prospective cohort study.

Correction: Management of nystagmus in children: a review of the literature and current practice in UK specialist services.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Management of nystagmus in children: a review of the literature and current practice in UK specialist services.

Nystagmus is an eye movement disorder characterised by abnormal, involuntary rhythmic oscillations of one or both eyes, initiated by a slow phase. It is not uncommon in the UK and regularly seen in paediatric ophthalmology and adult general/strabismus clinics. In some cases, it occurs in isolation, and in others, it occurs as part of a multisystem disorder, severe visual impairment or neurological disorder. Similarly, in some cases, visual acuity can be normal and in others can be severely degraded. Furthermore, the impact on vision goes well beyond static acuity alone, is rarely measured and may vary on a minute-to-minute, day-to-day or month-to-month basis. For these reasons, management of children with nystagmus in the UK is varied, and patients report hugely different experiences and investigations. In this review, we hope to shine a light on the current management of children with nystagmus across five specialist centres in the UK in order to present, for the first time, a consensus on investigation and clinical management.

A systematic review and meta-analysis of functional outcomes and complications following external fixation or open reduction internal fixation for distal intra-articular tibial fractures: an update.

PURPOSE: To conduct a systematic review and meta-analysis comparing physical function and complications following DIATF surgery with external fixation (EF) or open reduction internal fixation (ORIF). METHOD: A search was conducted using PubMed, Embase, Cochrane CENTRAL, Open Grey and Orthopaedic Proceedings. Studies with a level of evidence of I-III on patients (≥ 18 years) with DIATFs operated on with either EF or ORIF were included. A total of 3814 studies were identified. The Cochrane Risk of Bias Tool for randomised controlled trials and the ROBINS-I tool for nonrandomised studies were used to assess risk of bias. RESULTS: Nine studies with 478 patients, 271 ORIF and 197 EF met the inclusion criteria. The mean follow-up ranged from 12 to 38 months. The meta-analysis showed a higher incidence of superficial wound infections (RR = 2.94, 95% CI 1.62-5.34, p = 0.0004) and malunions (RR = 2.62, 95% CI 1.27-5.43, p = 0.009) in the EF group compared to the ORIF group. Also worse physical function was associated with the EF group. However, the overall evidence was low. CONCLUSION: This systematic review is the first to report on physical function following DIATF surgery. In general, decreased physical function was reported. The meta-analysis showed lower incidence of superficial wound infection and malunion rates in the ORIF group. Heterogeneity was low. In conclusion, this review reports lower complication rates following ORIF for DIATF. The overall evidence was limited, and therefore, the authors cannot recommend ORIF to be superior to EF treatment for DIATF. More multi-centre studies with larger sample sizes are needed to assess long-term physical function and complications following DIATF surgery. LEVEL OF EVIDENCE: Level 1.

Cell lines derived from feline fibrosarcoma display unstable chromosomal aneuploidy and additionally centrosome number aberrations.

The purpose of the study was to evaluate clonality and presence of numerical chromosomal and centrosomal aberrations in 5 established feline fibrosarcoma cell lines and in a fetal dermal fibroblast cell line as a control. The clonality of all cell lines was examined using limited-dilution cloning. The number of chromosomes was counted in metaphase spreads. The immunocytochemical analysis of centrosome numbers was performed by indirect immunofluorescence using a monoclonal antibody that targets γ-tubulin, a well-characterized component of centrosomes. Monoclonal cell populations could be established from all cell lines. In all feline fibrosarcoma cell lines, the number of chromosomes deviated abnormally from the normal feline chromosome number of 2n = 38, ranging from 19 to 155 chromosomes per cell. Centrosome hyperamplification was observed in all 5 feline fibrosarcoma cell lines with a proportion of cells (5.7 to 15.2%) having more than 2 centrosomes. In the control cell line, only 0.6% of the cells had more than 2 centrosomes. In conclusion, the examinations revealed that centrosome hyperamplification occurs in feline fibrosarcoma cell lines. The feline fibrosarcoma cell lines possessed 10 to 25 times as many cells with centrosome hyperamplification as the control cell line. These observations suggest an association of numerical centrosome aberrations with karyotype instability by increasing the frequency of chromosome missegregation. The results of this study may be helpful for further characterization of feline fibrosarcomas and may contribute to the knowledge of cytogenetic factors that may be important for the pathogenesis of feline fibrosarcomas.

Hippocampal inputs mediate theta-related plasticity in anterior thalamus.

Hippocampally-driven oscillatory activity at theta frequency is found in the diencephalon, but an understanding of the fundamental role of theta in the hippocampo-diencephalic circuit remains elusive. An important strategy in determining how activity modifies oscillatory properties of hippocampo-diencephalic circuitry comprises investigations of anterior thalamic responses to their main inputs: the descending dorsal fornix and the ascending mammillothalamic tract. Here, we show that the amplitude of thalamic theta spectral power selectively increases after plasticity-inducing stimulation of the dorsal fornix, but not of the mammillothalamic tract in urethane-anaesthetized young male rats. Furthermore, we show that low-frequency stimulation (LFS) significantly augments the fornix-driven theta ratio (theta over delta power, T-ratio), in parallel with depressing thalamic synaptic responses. However, the mammillothalamic synaptic response after LFS did not correlate with the slow band of theta oscillation (low T-ratio), but did correlate positively with the fast band of theta oscillation (high T-ratio). Our data demonstrate that the descending direct fornix projection is a pathway that modulates theta rhythm in the hippocampo-diencephalic circuit, resulting in dynamic augmentation of thalamic neuronal responsiveness. These findings suggest that hippocampal theta differentially affects synaptic integration in the different structures with which the hippocampus is reciprocally connected.

Selective lamina dysregulation in granular retrosplenial cortex (area 29) after anterior thalamic lesions: an in situ hybridization and trans-neuronal tracing study in rats.

There is growing evidence that lesions of the anterior thalamic nuclei cause long-lasting intrinsic changes to retrosplenial cortex, with the potential to alter its functional properties. The present study had two goals. The first was to identify the pattern of changes in eight markers, as measured by in-situ hydridisation, in the granular retrosplenial cortex (area Rgb) following anterior thalamic lesions. The second was to use retrograde trans-neuronal tracing methods to identify the potential repercussions of intrinsic changes within granular retrosplenial cortex. In Experiment 1, adult rats received unilateral lesions of the anterior thalamic nuclei and were perfused 4 weeks later. Of the eight markers, four (c-fos, zif268, 5ht2rc, kcnab2) showed a very similar pattern of change, with decreased levels in superficial retrosplenial cortex (lamina II) in the ipsilateral hemisphere but little or no change in deeper layers (lamina V). A fifth marker (cox6b) showed a shift in activity levels in the opposite direction to the previous four markers. Three other markers (cox6a1, CD74, ncs-1) did not appear to change activity levels after surgery. The predominant pattern of change, a decrease in superficial cortical activity, points to potential alterations in plasticity and metabolism. In Experiment 2, wheat germ agglutin (WGA) was injected into the anterior thalamic nuclei in rats given different survival times, sometimes in combination with the retrograde, fluorescent tracer, Fast Blue. Dense aggregations of retrogradely labeled cells were always found in lamina VI of granular retrosplenial cortex, but additional labeled cells in lamina II were only found: (1) in WGA cases, that is never after Fast Blue injections, and (2) after longer WGA survival times (3 days). These layer II Rgb cells are likely to have been trans-neuronally labeled, revealing a pathway from lamina II of Rgb to those deeper retrosplenial cells that project directly to the anterior thalamic nuclei.

Surface glass transition in bimodal polystyrene mixtures.

Using the cluster-embedding method of V. Zaporojchenko et al. (Macromolecules 34, 1125 (2000)), we measured the glass transition temperature T (g) at the polystyrene/vacuum interface of bimodal mixtures of monodisperse polystyrenes of 3.5k and 1000k. Embedding of approximately 1 nm Au clusters was monitored in situ by X-ray photoelectron spectroscopy (XPS). The clusters were formed by evaporation of Au onto the polymer surface. Only one glass transition was observed in the mixtures. The surface glass transition temperatures are correlated to but are below the bulk values of the mixtures and obey the Gordon-Taylor equation. The results suggest that the earlier reported molecular-weight dependence of the surface glass transition is not due to segregation of short chains to the surface.

Measurement of intraocular pressure (IOP) in chickens using a rebound tonometer: quantitative evaluation of variance due to position inaccuracies.

Intraocular pressure (IOP), an important risk factor for glaucoma, is a continuous trait determined by a complex set of genetic and environmental factors that are largely unknown. Genetic studies in laboratory animals may facilitate the identification of genes that affect IOP. We examined the use of the rebound tonometer for measuring IOP in non-anaesthetised birds, along with the device's robustness to alignment errors. Calibration curves were obtained by measuring the IOP of cannulated chicken eyes with the rebound tonometer over a range of pressures. To simulate different types of alignment errors that might be expected with measurement of IOP in alert chickens, for some calibrations the tonometer was positioned (1) at various distances from the cornea, (2) laterally displaced from the visual axis, or (3) angled away from the visual axis. In vivo measurements were taken on three-week-old alert chickens from a layer line, a broiler line, and a layer-broiler "advanced intercross line" (AIL) designed to facilitate QTL mapping. The rebound tonometer showed excellent linearity (R2=0.95-0.99) during calibration, as well as robustness to variation in the probe-to-cornea distance over the range 3-5mm and to lateral displacement over the range 0-2mm. However, the tonometer appeared less robust to off-axis misalignment over the range 0-20 degrees (P<0.05). Also, the slope of calibration curves sometimes differed between eyes (P<0.001), presumably reflecting differences in ocular structure. The IOP measured in non-anaesthetised three-week-old AIL chickens was 17.51+/-0.13 mmHg (mean+/-S.E.; N=105 birds). IOP was significantly associated with corneal thickness (P<0.05) and body weight (P<0.001) in a regression model. Replicate measurements were necessary in order to gauge IOP accurately in individual birds; a series of seven tonometry sessions over a 12-h period during the light phase of the light/dark cycle permitted IOP to be measured with a 95% CI of +/-0.7 mmHg. IOP did not differ significantly between the broiler and layer chicken lines which served as the progenitor lines for the AIL. In conclusion, the rebound tonometer permits rapid estimation of IOP in chickens and is well tolerated. The small alignment errors that are expected when taking measurements in non-anaesthetised animals are unlikely to affect accuracy. Since high IOP is a major risk factor for glaucoma, identifying QTL controlling IOP may offer future health benefits. However, our preliminary findings highlight several obstacles to mapping such QTL using the chicken advanced intercross line evaluated here.

X-ray reflectivity study on the surface and bulk glass transition of polystyrene.

The surfaces of polystyrene (PS) films decorated with gold nanoclusters were investigated by x-ray reflectivity measurements. The thicknesses of the films are much larger than the radii of gyration of the different PS samples. By annealing the films above the glass transition temperature T(g) an embedding process of the clusters into the polymer is detected which is accompanied by a substantial increase in the cluster layer thickness due to Brownian motion. These processes start at a sufficiently low viscosity and may be regarded as a probe of the glass transition in the near surface region of the PS films. Simultaneously the thermal expansion of the entire film and hence its approximate bulk behavior were monitored. Two samples of different molecular weight do not show a significant difference between the surface and bulk T(g) values.

Oxygen modulates the release of urokinase and plasminogen activator inhibitor-1 by retinal pigment epithelial cells.

The aims of this study were to examine the effect of oxygen, in the presence or absence of exogenous growth factors, on the release of plasminogen activators and plasminogen activator inhibitor-1 by cultured human retinal pigment epithelial cells. Antigen and activity levels of urokinase, tissue plasminogen activator and plasminogen activator inhibitor were measured in conditioned media after cells were exposed to three different oxygen environments: hypoxia, normoxia and hyperoxia. Overall proteolytic balance was determined by zymography. The effects of exogenous basic fibroblast growth factor and transforming growth factor-beta were also examined. it was found that retinal pigment epithelial cells released urokinase, tissue plasminogen activator and plasminogen activator inhibitor in measurable quantities. After 48 h, urokinase levels were highest at normoxia, reaching 7.2ng/10(6) cells (+/-2.0 SEM), whereas plasminogen activator inhibitor 1 levels were highest at hyperoxia, reaching 67.5ng/10(6) cells (+/-3.7 SEM). Tissue plasminogen activator levels were minimal (<0.5ng/10(6) cells) and unaffected by both oxygen and growth factors. Overall proteolytic activity was also greatest at normoxia. Fibroblast growth factor stimulated urokinase production dose-dependently, but plasminogen activator inhibitor only minimally. Transforming growth factor-beta stimulated plasminogen activator inhibitor production dose-dependently but urokinase only at higher concentrations. These results suggest that both oxygen tension and growth factors may interact to modulate the proteolytic properties of the human retinal pigment epithelium.

Using fos imaging in the rat to reveal the anatomical extent of the disruptive effects of fornix lesions.

Activity of the immediate early gene c-fos was compared across hemispheres in rats with unilateral fornix lesions. To engage Fos production, rats first performed a radial arm maze task that is severely disrupted by bilateral fornix lesions. Using immunohistochemical techniques, Fos-positive cells were visualized and counted in 39 sites in both hemispheres. Fornix lesions led to a significant reduction in Fos in all ipsilateral hippocampal subfields, as well as the entorhinal cortex and most of the subicular complex. Other sites that showed reduced activity included the ipsilateral retrosplenial, anterior cingulate, and postrhinal cortices. Subcortical regions showing significant Fos decreases included the anterior thalamic nuclei, supramammillary nucleus, diagonal band of Broca, and lateral septum. Thus, the effects of fornix lesions extended beyond the hippocampal formation and included sites not directly innervated by the tract. These changes were nevertheless selective, as shown by the lack of hemispheric difference in any of the preselected control sites, the perirhinal cortex, or nucleus accumbens. Furthermore, there were no hemispheric differences in an additional group of animals with unilateral fornix lesions that were killed directly from the home cage. The location of Fos changes closely corresponded to those brain regions that when lesioned disrupt spatial working memory. Moreover, there was a correspondence between those brain regions that show increased Fos production in normal animals performing the radial arm maze task and those affected by fornix lesions. These results show that fornix transection has widespread, but selective, effects on a network of structures normally activated by spatial memory processes, with these effects extending beyond the hippocampal formation.

Protein kinase C isoenzyme expression in retinal cells.

Protein kinase C (PKC) is involved in both the physiological and pathophysiological processes in the retina and plays an important role in signal transduction. The aim of this study was to determine the PKC isoenzyme profile in three retinal cell types in culture, namely RPE cells, pericytes and retinal microvascular endothelial cells. Confluent cultures were lysed and isoenzyme expression detected by Western blotting. PKC isoenzymes alpha, beta(2) and delta were observed for all three cell types while beta(1) was specific for RPE cells. This study has characterised the PKC isoenzyme profile in three retinal cell types and suggests that defining the cell-specific isoenzyme pattern is an important step in understanding their precise physiological role and regulation in the retina.

Fos imaging reveals differential patterns of hippocampal and parahippocampal subfield activation in rats in response to different spatial memory tests.

We compared neuronal activation, as measured by Fos staining, during different spatial tasks in two experiments. The counts of Fos-stained neurons in the hippocampus increased as the spatial demands of the tasks increased, the tasks having been carefully matched for other factors. In Experiment 1, matched groups of rats either ran a standard eight-arm radial maze task or were trained to run up and down just one arm of the maze; the number of runs and rewards was identical in both conditions. In Experiment 2, rats were trained on the eight-arm maze but in different rooms. On the critical test day, both groups were run in the same room so that one group now performed with novel landmarks. All hippocampal subfields (dentate gyrus, CA3, CA1, dorsal, ventral, and caudal subiculum) showed a relative increases in c-fos activation in the eight-arm (Experiment 1) and novel room (Experiment 2) conditions, the sole exception being the ventral subiculum in Experiment 2. Although increased c-fos activation was found in both dorsal and ventral hippocampus, in Experiment 2 the relative increase was significantly greater in the dorsal hippocampus. Parahippocampal cortices responded heterogeneously: the perirhinal cortex failed to show increased activation in both experiments, in contrast to the entorhinal and postrhinal cortices. Subsequent comparisons confirmed that the perirhinal and postrhinal cortices responded in qualitatively different ways, the perirhinal cortex differing from the rest of the hippocampal formation. These experiments, which provide the first analysis of hippocampal Fos production during tests of allocentric spatial working memory, reveal that all components of the hippocampus are activated, but that under certain conditions the dorsal hippocampus is disproportionately involved.

Highly potent and selective inhibition of varicella-zoster virus by bicyclic furopyrimidine nucleosides bearing an aryl side chain.

In addition to our recent report on the potent anti-varicella-zoster virus (VZV) activity of some unusual bicyclic furopyrimidine nucleosides bearing long alkyl side chains, we herein report the further significant enhancement of the antiviral potency by inclusion of a phenyl group in the side chain of these compounds. The target structures were prepared by the Pd-catalyzed coupling of a series of para-substituted arylacetylenes with 5-iodo-2'-deoxyuridine, to give intermediate 5-alkynyl nucleosides which were cyclized in the presence of Cu to give the desired bicyclic systems. The compounds display extraordinary potency and selectivity for VZV; the most active are ca. 10 000 times more potent than the reference compound acyclovir and ca. 100 times more potent than the alkyl analogues earlier reported by us. The current compounds show little cytotoxicity, leading to selectivity index values >/= 1 000 000. From a range of DNA and RNA viruses tested, only VZV was inhibited by these compounds indicating their extreme selectivity for this target virus. The novelty of the molecules, coupled with their extreme potency and selectivity, their desirable physicochemical properties, and their relative ease of synthesis, makes them of considerable interest for potential drug development for VZV infections.

Neurochemical evidence for at least two regional subdivisions within the homing pigeon (Columba livia) caudolateral neostriatum.

The distributions of one neurotransmitter, two neurotransmitter-related substances, and five neuropeptides were examined within the homing pigeon caudolateral neostriatum (NCL). All eight neuroactive substances were found within a tyrosine hydroxylase (TH)-dense region that defines the NCL. Overall regional variation in the relative density of these substances suggested at least two neurochemically distinct portions of NCL. Dorsal NCL contained relatively dense staining for TH, choline acetyltransferase, and substance P, whereas vasoactive intestinal polypeptide was more abundant in ventral portions of NCL. Serotonin and cholecystokinin were found to be densest in intermediate portions of NCL. Somatostatin and leucine-enkephalin were homogeneously distributed throughout NCL. The results suggest that NCL may consist of multiple subdivisions. Investigations into the behavioral importance of these regions are necessary to clarify the role of this brain region in avian behavior.