Contribution of behavioural variability to representational drift

Neuronal responses to similar stimuli change dynamically over time, raising the question of how internal representations can provide a stable substrate for neural coding. While the drift of these representations is mostly characterized in relation to external stimuli or tasks, behavioural or internal state of the animal is also known to modulate the neural activity. We therefore asked how the variability of such modulatory mechanisms can contribute to representational drift. By analysing publicly available datasets from the Allen Brain Observatory, we found that behavioural variability significantly contributes to changes in stimulus-induced neuronal responses across various cortical areas in the mouse. This effect could not be explained by a gain model in which change in the behavioural state scaled the signal or the noise. A better explanation was provided by a model in which behaviour contributed independently to neuronal tuning. Our results are consistent with a view in which behaviour modulates the low-dimensional, slowly-changing setpoints of neurons, upon which faster operations like sensory processing are performed. Importantly, our analysis suggests that reliable but variable behavioural signals might be misinterpreted as representational drift, if neuronal representations are only characterized in the stimulus space and marginalised over behavioural parameters.

Stress and the Cardiovascular System

<p>The research reported in this thesis is primarily concerned with systemic arterial pulse transit time (PTT) which is of physiological significance because it is the most appropriate indicator of arterial compliance, the primary determinant of cardiac load, PTT acceleration or deceleration being associated with an increase or decrease in cardiac load respectively. Initially, PTT was investigated in the context of active/passive coping. Obrist, et al., (1978) proposed that active coping is generated by tasks of moderate difficulty and is characterized by large, sustained cardiac accelerations. Interbeat interval (IBI) was measured as the reference response for active/passive coping. The assumption is that active coping is the behavioural state which provides the link between psychological stress and hypertension. However, contemporary cardiovascular physiologists put more emphasis on arterial compliance than IBI because it is not only significant in essential hypertension, but is also a critical determinant of circulation efficiency in health and disease. In Experiment 1 men and women completed mental arithmetic, problem solving, reaction time and personal tempo (voluntary button pressing). Acceleratory and deceleratory PTT changes were found during all tasks; IBI changes were predominantly acceleratory and their magnitude was determined by task difficulty. In Experiment 2 subjects completed problem solving tasks at two levels of difficulty. The results confirmed that unexplained directional variability characterized PTT changes and acceleration characterized IBI changes. It was hypothesized that subject state could be a determinant of PTT response direction. In Experiment 3 the State-Trait Anxiety Inventory, the Stress Arousal Checklist, the Eysenck Personality Inventory and the Jenkins Activity Survey were administered before problem solving at three levels of difficulty and personal tempo were completed. PTT directional variability was not accounted for by any of the measures used. IBI changes were again acceleratory and their magnitude was determined by task difficulty. Two extensions of the active/passive coping hypothesis were proposed: 1) that task difficulty and magnitude of IBI change are related along a continuum of behavioural coping; 2) that task type, not difficulty, determines the frequency of IBI acceleration. The effect of task contingency on IBI change was identified as requiring more detailed investigation. It was further hypothesized that relative subject state as measured by a change in resting IBI (Malmo, 1959) could predict the direction of PTT change during task. In Experiment 4 subjects completed all tasks from Experiment 3 in both parts of an extended experimental session. Half the subjects ingested caffeine. IBI decelerated during baseline from part 1 to part 2 and deceleratory PTT changes dominated task responding in part 2. However, a caffeine-induced deceleration in IBI across baselines was not associated with deceleratory PTT change, and directional variability continued to characterize PTT changes. In order to eliminate the directional variability of PTT changes during tasks a further experiment was undertaken which manipulated relative behavioural state prior to task by informing subjects on their first attendance at the laboratory that they would be required to perform a demanding problem solving task on their fifth attendance. From sessions 1 to 4 subjects attended the laboratory for short rest periods only during which cardiovascular activity was recorded. On the fifth session subjects also completed a task. In that experiment (Experiment 5), IBI acceleration over multiple session baselines in anticipation of a task was associated with uniformly acceleratory PTT changes during tasks, supporting the hypothesis that subject initial state is an important determinant of the direction of PTT change, and hence in whether cardiac load increases or decreases under stress.</p>

Stress and the Cardiovascular System

<p>The research reported in this thesis is primarily concerned with systemic arterial pulse transit time (PTT) which is of physiological significance because it is the most appropriate indicator of arterial compliance, the primary determinant of cardiac load, PTT acceleration or deceleration being associated with an increase or decrease in cardiac load respectively. Initially, PTT was investigated in the context of active/passive coping. Obrist, et al., (1978) proposed that active coping is generated by tasks of moderate difficulty and is characterized by large, sustained cardiac accelerations. Interbeat interval (IBI) was measured as the reference response for active/passive coping. The assumption is that active coping is the behavioural state which provides the link between psychological stress and hypertension. However, contemporary cardiovascular physiologists put more emphasis on arterial compliance than IBI because it is not only significant in essential hypertension, but is also a critical determinant of circulation efficiency in health and disease. In Experiment 1 men and women completed mental arithmetic, problem solving, reaction time and personal tempo (voluntary button pressing). Acceleratory and deceleratory PTT changes were found during all tasks; IBI changes were predominantly acceleratory and their magnitude was determined by task difficulty. In Experiment 2 subjects completed problem solving tasks at two levels of difficulty. The results confirmed that unexplained directional variability characterized PTT changes and acceleration characterized IBI changes. It was hypothesized that subject state could be a determinant of PTT response direction. In Experiment 3 the State-Trait Anxiety Inventory, the Stress Arousal Checklist, the Eysenck Personality Inventory and the Jenkins Activity Survey were administered before problem solving at three levels of difficulty and personal tempo were completed. PTT directional variability was not accounted for by any of the measures used. IBI changes were again acceleratory and their magnitude was determined by task difficulty. Two extensions of the active/passive coping hypothesis were proposed: 1) that task difficulty and magnitude of IBI change are related along a continuum of behavioural coping; 2) that task type, not difficulty, determines the frequency of IBI acceleration. The effect of task contingency on IBI change was identified as requiring more detailed investigation. It was further hypothesized that relative subject state as measured by a change in resting IBI (Malmo, 1959) could predict the direction of PTT change during task. In Experiment 4 subjects completed all tasks from Experiment 3 in both parts of an extended experimental session. Half the subjects ingested caffeine. IBI decelerated during baseline from part 1 to part 2 and deceleratory PTT changes dominated task responding in part 2. However, a caffeine-induced deceleration in IBI across baselines was not associated with deceleratory PTT change, and directional variability continued to characterize PTT changes. In order to eliminate the directional variability of PTT changes during tasks a further experiment was undertaken which manipulated relative behavioural state prior to task by informing subjects on their first attendance at the laboratory that they would be required to perform a demanding problem solving task on their fifth attendance. From sessions 1 to 4 subjects attended the laboratory for short rest periods only during which cardiovascular activity was recorded. On the fifth session subjects also completed a task. In that experiment (Experiment 5), IBI acceleration over multiple session baselines in anticipation of a task was associated with uniformly acceleratory PTT changes during tasks, supporting the hypothesis that subject initial state is an important determinant of the direction of PTT change, and hence in whether cardiac load increases or decreases under stress.</p>

Characterisation of the Behavioural Effects of a Thoracic Squeeze in Healthy Newborn Piglets

A thoracic squeeze has been observed to cause both healthy and low vigour neonatal foals to enter a ‘less-responsive state’, characterised by loss of posture, eye closure and cessation of movement, from which they rapidly recover to express normal healthy behaviours when the squeeze is released. To date, there have been no systematic studies characterising the responses of healthy neonates of other mammalian species to a thoracic squeeze. We describe the responses of healthy newborn piglets (n = 17) to a standardised application of the thoracic squeeze and evaluate the effect of the method of squeeze application on the response. Neonatal piglets were squeezed around the chest with either a soft fabric rope as has been used in foals (n = 8) or a novel purpose-made inflation cuff (n = 9). Both methods were effective at inducing a less-responsive behavioural state in all piglets, with neural reflexes reduced or absent in over half of them. The inflation cuff appeared to induce the less-responsive state faster than the rope, and more piglets squeezed with the cuff remained in this state for the full 10-min squeeze. These findings suggest that the behavioural response of foals to thoracic squeezing can be generalised to neonates of other precocial mammalian species. This initial study provides a foundation for further research using the inflation cuff to explore mechanisms underlying the thoracic squeeze and ways in which it may be applied whilst performing husbandry procedures.

Hippocampal theta oscillations are modulated by behaviour in the ferret but persist during both locomotion and immobility

Theta oscillations are a hallmark of hippocampal activity across mammalian species and play a critical role in many hippocampal models of memory and spatial navigation. To attempt to reconcile the cross-species differences observed in the presence and properties of theta, we recorded hippocampal local field potentials in rats and ferrets during a localisation task designed to vary locomotion and sensory attention. Here we show that theta oscillations occur during locomotion in both the ferret and rat, however during periods of immobility, theta oscillations persisted in the ferret, contrasting starkly with the switch to large irregular activity (LIA) in the rat. Theta during immobility in the ferret was identified as Type 2 theta due to its sensitivity to atropine and was modulated by behavioural state, with the strongest theta observed during reward epochs. These results demonstrate that even under similar behavioural conditions, there is a variable relationship between theta and behavioural state across different species.

Prey and habitat distribution are not enough to explain predator habitat selection: addressing intraspecific interactions, behavioural state and time

Background Movements and habitat selection of predators shape ecological communities by determining the spatiotemporal distribution of predation risk. Although intraspecific interactions associated to territoriality and parental care are involved in predator habitat selection, few studies have addressed their effects simultaneously with those of prey and habitat distribution. Moreover, individuals require behavioural and temporal flexibility in their movement decisions to meet various motivations in a heterogeneous environment. To untangle the relative importance of ecological determinants of predator fine-scale habitat selection, we studied simultaneously several spatial, temporal, and behavioural predictors of habitat selection in territorial arctic foxes (Vulpes lagopus) living within a Greater snow goose (Anser caerulescens atlantica) colony during the reproductive season. Methods Using GPS locations collected at 4-min intervals and behavioural state classification (active and resting), we quantified how foxes modulate state-specific habitat selection in response to territory edges, den proximity, prey distribution, and habitats. We also assessed whether foxes varied their habitat selection in response to an important phenological transition marked by decreasing prey availability (goose egg hatching) and decreasing den dependency (emancipation of cubs). Results Multiple factors simultaneously played a key role in driving habitat selection, and their relative strength differed with respect to the behavioural state and study period. Foxes avoided territory edges, and reproductive individuals selected den proximity before the phenological transition. Higher goose nest density was selected when foxes were active but avoided when resting, and was less selected after egg hatching. Selection for tundra habitats also varied through the summer, but effects were not consistent. Conclusions We conclude that constraints imposed by intraspecific interactions can play, relative to prey distribution and habitat characteristics, an important role in the habitat selection of a keystone predator. Our results highlight the benefits of considering behavioural state and seasonal phenology when assessing the flexibility of predator habitat selection. Our findings indicate that considering intraspecific interactions is essential to understand predator space use, and suggest that using predator habitat selection to advance community ecology requires an explicit assessment of the social context in which movements occur.

Legal Complexities of Animal Welfare in Australia: Do On-Animal Sensors Offer a Future Option?

The five freedoms and, more recently, the five domains of animal welfare provide internationally recognised frameworks to evaluate animal welfare practices which recognise both the physical and mental wellbeing needs of animals, providing a balanced view of their ability to cope in their environment. Whilst there are many techniques to measure animal welfare, the challenge lies with how best to align these with future changes in definitions and expectations, advances in science, legislative requirements, and technology improvements. Furthermore, enforcement of current animal welfare legislation in relation to livestock in Australia and the reliance on self-audits for accreditation schemes, challenges our ability to objectively measure animal welfare. On-animal sensors have enormous potential to address animal welfare concerns and assist with legislative compliance, through continuous measurement and monitoring of an animal’s behavioural state and location being reflective of their wellbeing. As reliable animal welfare measures evolve and the cost of on-animal sensors reduce, technology adoption will increase as the benefits across the supply chain are realised. Future adoption of on-animal sensors by producers will primarily depend on a value proposition for their business being clear; algorithm development to ensure measures are valid and reliable; increases in producer knowledge, willingness, and trust in data governance; and improvements in data transmission and connectivity.

Regulation of dietary intake of protein and lipid by nurse-age adult worker honeybees

Essential macronutrients are critical to the fitness and survival of animals. Many studies have shown that animals regulate the amount of protein and carbohydrate they eat for optimal performance. Regulation of dietary fat is important but less often studied. Honeybees collect and consume floral pollen to obtain protein and fat but how they achieve the optimal balance of these two macronutrients is presently unknown. Here, using chemically defined diets composed of essential amino acids and lipids (lecithin), we show that adult worker honeybees actively regulate their intake of lipids around optimal values relative to protein in diet. We found that broodless, nurse-age worker honeybees consume foods to achieve a ratio between 1:2 and 1:3 (essential amino acids:lipid) or ∼1.25:1 protein:fat. Bees fed diets relatively high in fat gained abdominal fat and had enlarged hypopharyngeal glands. In most cases, eating diets high in fat did not result in increased mortality. Importantly, we also discovered that the total quantity of food the bees ate increased when they were given a choice of two diets relatively high in fat, implying that dietary fat influences bee nutritional state in a way that in turn, influences behaviour. We speculate that dietary fat plays a critical role in maintaining workers in the nurse-like behavioural state independently of the influence of queen pheromone.

How deep is the rift between conscious states in sleep and wakefulness? Spontaneous experience over the sleep–wake cycle

Whether we are awake or asleep is believed to mark a sharp divide between the types of conscious states we undergo in either behavioural state. Consciousness in sleep is often equated with dreaming and thought to be characteristically different from waking consciousness. Conversely, recent research shows that we spend a substantial amount of our waking lives mind wandering, or lost in spontaneous thoughts. Dreaming has been described as intensified mind wandering, suggesting that there is a continuum of spontaneous experience that reaches from waking into sleep. This challenges how we conceive of the behavioural states of sleep and wakefulness in relation to conscious states. I propose a conceptual framework that distinguishes different subtypes of spontaneous thoughts and experiences independently of their occurrence in sleep or waking. I apply this framework to selected findings from dream and mind-wandering research. I argue that to assess the relationship between spontaneous thoughts and experiences and the behavioural states of sleep and wakefulness, we need to look beyond dreams to consider kinds of sleep-related experience that qualify as dreamless. I conclude that if we consider the entire range of spontaneous thoughts and experiences, there appears to be variation in subtypes both within as well as across behavioural states. Whether we are sleeping or waking does not appear to strongly constrain which subtypes of spontaneous thoughts and experiences we undergo in those states. This challenges the conventional and coarse-grained distinction between sleep and waking and their putative relation to conscious states. This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.