Representation of visual information within the dendritic tree of pyramidal cells in primary visual cortex

A fundamental aim in system neuroscience is to understand how sensory information is represented in the brain. While a wealth of studies investigated how visual stimuli are encoded in populations of neurons, little is known about how visual information is represented in a single cell at the level of the dendritic tree. This is due in part to difficulties in measuring dendritic activity within dendritic arbours, which are typically fine three dimensional structures. To overcome this, we have used a custom 3D two-photon acousto-optic lens microscope to measure visually-evoked dendritic activity in pyramidal cells in mouse primary visual cortex. Pyramidal neurons were sparsely co-labelled with the genetically-encoded calcium indicator GCaMP6f and with the red fluorophore TdTomato. Dendritic activity was monitored with GCaMP6f, and simultaneous recording of the activity-independent red TdTomato fluorescence was used to detect movement of the tissue. Random access point measurements were made at 80-120 Hz from multiple locations distributed in three dimensions, and this enabled me to monitor neuronal activity in a substantial fraction of the dendritic tree and in the soma near-simultaneously. Patterns of dendritic activity were characterized in layer 2/3 neurons and in the tuft of layer 5 pyramidal neurons during presentation of gratings in awake animals. In the tuft of layer 5 neurons, calcium transients tended to be either localized to 1-2 dendritic branches, or to occur in the full-dendritic tuft and in the soma. In contrast, in layer 2/3 neurons calcium transients were mainly local, and somatic calcium transients were rarely accompanied by global events. Visually-evoked dendritic activity was evident in layer 2/3 neurons, and I observed that dendrites tend to have similar orientation tuning curves as the soma. But several dendrites with different preferred orientations were present in all the cells imaged. Dendritic activity in layer 2/3 neurons was little affected by anaesthesia and locomotion. In contrast, apical dendrites of layer 5 neurons showed little response to visual stimuli, but they were strongly modulated by the state of the animal. Indeed, anaesthesia suppressed dendritic activity in these cells, while locomotion enhanced it compared to the resting state. These data suggest that dendrites in layer 5 and in layer 2/3 pyramidal neurons have different integration mechanisms in vivo, and that they process different types of synaptic inputs. While layer 2/3 neurons receive mainly feedforward (bottom-up) visual inputs, apical dendrites in layer 5 cells are driven primarily by top-down inputs (animal state)

Partial analytic validation of determination of cortisol in dog hair using a commercial EIA kit

The quantification of cortisol in hair samples is a relatively recent method that has been increasingly used for the evaluation of long-term cortisol secretion and chronic stress levels, in both humans and non-human animals. The use of hair presents many advantages in relation to the use of other biological matrices, e.g. a very low invasiveness of the sample collection. Besides, cortisol analysis in hair samples provides measurements over a long period of time, which can be used as a chronic stress indicator. Nevertheless, the physiology of cortisol in hair and the evaluation of reliable methods for its quantification in hair samples need to be further investigated. The aim of this study was to perform a partial analytical validation for the quantification of cortisol in domestic dog hair samples using a commercially available high sensitivity salivary cortisol enzyme immunoassay kit. Results on both precision and linearity tests were overall favorable, supporting that the kit can be used to reliably measure hair cortisol concentrations in dogs

Random-access scanning microscopy for 3D imaging in awake behaving animals

Understanding how neural circuits process information requires rapid measurements of activity from identified neurons distributed in 3D space. Here we describe an acousto-optic lens two-photon microscope that performs high-speed focusing and line scanning within a volume spanning hundreds of micrometers. We demonstrate its random-access functionality by selectively imaging cerebellar interneurons sparsely distributed in 3D space and by simultaneously recording from the soma, proximal and distal dendrites of neocortical pyramidal cells in awake behaving mice

Horses show individual level lateralisation when inspecting an unfamiliar and unexpected stimulus.

Animals must attend to a diverse array of stimuli in their environments. The emotional valence and salience of a stimulus can affect how this information is processed in the brain. Many species preferentially attend to negatively valent stimuli using the sensory organs on the left side of their body and hence the right hemisphere of their brain. Here, we investigated the lateralisation of visual attention to the rapid appearance of a stimulus (an inflated balloon) designed to induce an avoidance reaction and a negatively valent emotional state in 77 Italian saddle horses. Horses' eyes are laterally positioned on the head, and each eye projects primarily to the contralateral hemisphere, allowing eye use to be a proxy for preferential processing in one hemisphere of the brain. We predicted that horses would inspect the novel and unexpected stimulus with their left eye and hence right hemisphere. We found that horses primarily inspected the balloon with one eye, and most horses had a preferred eye to do so, however, we did not find a population level tendency for this to be the left or the right eye. The strength of this preference tended to decrease over time, with the horses using their non-preferred eye to inspect the balloon increasingly as the trial progressed. Our results confirm a lateralised eye use tendency when viewing negatively emotionally valent stimuli in horses, in agreement with previous findings. However, there was not any alignment of lateralisation at the group level in our sample, suggesting that the expression of lateralisation in horses depends on the sample population and testing context

Effect of housing system on reproductive behaviour and on some endocrinological and seminal parameters of donkey stallions

Reproductive management of male donkeys employed for artificial breeding has been poorly studied. The aim of this study was to evaluate the effect of housing system, with the animals grouped together in a paddock or kept in individual boxes, on sexual behaviour, cortisol and testosterone concentration and seminal characteristics of adult male donkeys. The study included four Amiata donkey jacks (stallions) from which ejaculates, saliva and blood were collected during two distinct 3 weeks periods, one in the group and one in the box housing system. Time needed for semen collection was shorter when donkeys were kept in paddocks compared to when they were kept in single boxes (14:57 ± 07:27 and 20:52 ± 09:31 min, p < .05). Native semen characteristics were not influenced by housing system, while cooled preservation in an Equitainer(®) showed that sperm motility parameters were significantly higher during the paddock period compared to the box period. Salivary cortisol was influenced by housing system, both before and 60 min after ejaculation, being statistically higher when donkeys were housed in paddocks. On the contrary, overall and basal testosterone concentrations were significantly higher when animals were kept in boxes. In conclusion, in the present study, good quality semen could be successfully collected from donkeys irrespective of the housing system despite some differences in hormone concentrations

The emergence of functional microcircuits in visual cortex.

Sensory processing occurs in neocortical microcircuits in which synaptic connectivity is highly structured and excitatory neurons form subnetworks that process related sensory information. However, the developmental mechanisms underlying the formation of functionally organized connectivity in cortical microcircuits remain unknown. Here we directly relate patterns of excitatory synaptic connectivity to visual response properties of neighbouring layer 2/3 pyramidal neurons in mouse visual cortex at different postnatal ages, using two-photon calcium imaging in vivo and multiple whole-cell recordings in vitro. Although neural responses were already highly selective for visual stimuli at eye opening, neurons responding to similar visual features were not yet preferentially connected, indicating that the emergence of feature selectivity does not depend on the precise arrangement of local synaptic connections. After eye opening, local connectivity reorganized extensively: more connections formed selectively between neurons with similar visual responses and connections were eliminated between visually unresponsive neurons, but the overall connectivity rate did not change. We propose a sequential model of cortical microcircuit development based on activity-dependent mechanisms of plasticity whereby neurons first acquire feature preference by selecting feedforward inputs before the onset of sensory experience--a process that may be facilitated by early electrical coupling between neuronal subsets--and then patterned input drives the formation of functional subnetworks through a redistribution of recurrent synaptic connections

Consistency and flexibility in solving spatial tasks: different horses show different cognitive styles

Individual animals vary in their behaviour and reactions to novel situations. These differences may extend to differences in cognition among individuals. We tested twenty-six horses for their ability to detour around symmetric and asymmetric obstacles. All of the animals were able to get around the barrier to reach a food target, but varied in their approach. Some horses moved slowly but were more accurate in choosing the shortest way. Other horses acted quickly, consistently detoured in the same direction, and did not reliably choose the shortest way. The remaining horses shifted from a faster, directionally consistent response with the symmetric barrier, to a slower but more accurate response with the asymmetric barrier. The asymmetric barrier induced a reduction in heart rate variability, suggesting that this is a more demanding task. The different approaches used to solve the asymmetric task may reflect distinct cognitive styles in horses, which vary among individuals, and could be linked to different personality traits. Understanding equine behaviour and cognition can inform horse welfare and management

Somatostatin Receptor 1 and 5 Double Knockout Mice Mimic Neurochemical Changes of Huntington's Disease Transgenic Mice

Selective degeneration of medium spiny neurons and preservation of medium sized aspiny interneurons in striatum has been implicated in excitotoxicity and pathophysiology of Huntington's disease (HD). However, the molecular mechanism for the selective sparing of medium sized aspiny neurons and vulnerability of projection neurons is still elusive. The pathological characteristic of HD is an extensive reduction of the striatal mass, affecting caudate putamen. Somatostatin (SST) positive neurons are selectively spared in HD and Quinolinic acid/N-methyl-D-aspartic acid induced excitotoxicity, mimic the model of HD. SST plays neuroprotective role in excitotoxicity and the biological effects of SST are mediated by five somatostatin receptor subtypes (SSTR1-5). and R6/2 mice. Conversely, the expression of somatostatin receptor subtypes, enkephalin and phosphatidylinositol 3-kinases were strain specific. SSTR1/5 appears to be important in regulating NMDARs, DARPP-32 and signaling molecules in similar fashion as seen in HD transgenic mice.This is the first comprehensive description of disease related changes upon ablation of G- protein coupled receptor gene. Our results indicate that SST and SSTRs might play an important role in regulation of neurodegeneration and targeting this pathway can provide a novel insight in understanding the pathophysiology of Huntington's disease