Linguistic birds : exploring cognitive abilities in zebra finches by using artificial grammars

The aim of this thesis is to shed light on whether some capacities that are considered linked to, or characteristic for, language are shared between humans and nonhuman animals, which can help to understand the basic cognitive abilities from which the evolution of human language may have arisen. The thesis starts with comparing human language with other communication systems. Then Chapter 2 addressed the question: what mechanisms are involved in learning a sequence of vocal items in zebra finches. Chapter 3 addressed whether zebra finches are able to discriminate between, and generalize, affixation patterns. Chapter 4 dealt with a controversial topic that is recently getting a lot of attention: whether animals show the ability to learn __algebraic__ rules that are relevant to syntax learning in humans. Chapter 5 examined the ability of zebra finch to learn nonadjacent dependency that is important for learning the hierarchical structure of languages. Altogether, this thesis provides positive evidence for similarities between humans and songbirds in using transitional information, generalizing surface transformations of human affixation patterns and detecting nonadjacent dependencies.UBL - phd migration 201

The foraging behaviour of hummingbirds through space and time

Central place foragers, such as territorial hummingbirds, feed from resources that tend to be constant in space and to replenish with time (e.g. nectar in flowers). The ability to remember both where and when resources are available would allow these animals to forage efficiently. Animals that feed at multiple locations would also benefit from forming routes between these multiple locations. Hummingbirds are thought to forage by repeating the order in which they visit several locations following a route called a “trapline”, although there are no quantitative data describing this behaviour. As a first step to determining how and if wild free living hummingbirds forage by traplining, I decomposed this behaviour into some of its key components. Through five field experiments, where I trained free-living hummingbirds to feed from artificial flowers, I confirmed that territorial hummingbirds will, in fact, trapline. Birds will use the shortest routes to visit several locations and will prioritize those locations that are closest to a usual feeding site. Additionally, even though hummingbirds can learn to use temporal information when visiting several patches of flowers, the spatial location of those patches has a larger influence in how these birds forage in the wild. Since male and female hummingbirds were thought to forage differently I also tested whether there were sex differences in the types of cues they use when foraging. Contrary to expectation, female hummingbirds will also use spatial cues to relocate a rewarded site. Using the foraging ecology of rufous hummingbirds to formulate predictions as to what information these birds should use has lead me to discover that these birds forage in a completely different way than previously thought

Investigation of Memory Related Cortical Thalamic Circuitry in the Human Brain

This dissertation examined the role of medial prefrontal cortex (mPFC) and the hippocampus (HC) in episodic memory, and provides a novel approach to identify the midline thalamus mediating mPFC-HC interactions in humans. The mPFC and HC are critical to the temporal organization of episodic memory, and these interactions are disrupted in several mental health and neurological disorders. In the first study, I provide evidence that the mPFC is involved in ordinal retrieval, and the HC is active in temporal context retrieval in remembering the order of when events happen. In the second study, I focus on the anatomical basis of the mPFC-HC interactions which is reliant on the midline thalamus. I review in detail the anatomy of the midline thalamus both in location, and connectivity profile with the rest of the brain comparing the extensive anatomical evidence in rodents with the available evidence in monkeys and humans. This section also elaborates on the role of the midline thalamus in memory, stress regulation, wakefulness, and feeding behavior, and how pathological markers along the midline thalamus are a vanguard of several neurological disorders including Alzheimer’s Disease, schizophrenia, depression, and drug addiction. Lastly, I devised a new approach to identify the midline thalamus in humans in vivo using diffusion weighted imaging, capitalizing on known fiber connections gleaned from non-human animals, focusing on connections between the midline thalamus and the mPFC, medial temporal lobe and the nucleus accumbens. The success of this approach is promising for translational imaging. Overall, this dissertation provides new evidence on 1) complementary functional roles of the mPFC and HC in sequence memory, 2) a cross-species anatomical framework for understanding the midline thalamus in humans and neurological disorders, and 3) a new method for non-invasive identification of the midline thalamus in humans in vivo. Thus, this dissertation provides a new fundamental understanding of mPFC-midline thalamic-HC circuit in humans and tools for its non-invasive study in human disease