Neuroscience

First, the brain is organized into functionally specific areas, and second, neurons in different parts of the vertebrate nervous system, indeed in all nervous systems, are quite similar. Small comparison with Computers A gross observation between computer’s transistors and human neurons is that there a big difference of numbers: trillions of transistors vs billions of neurons. 6 orders of magnitude frequency difference (Ghz versus 1kHz for neurons). Many many neural types and different types of connections. And the digital vs analog and chemical modes of communication. Parallel processor abilities. Fixed vs plastic architectures But this is comparing with transistors with one higher level object, so this comparison might not be completely fair. They are very different from this point of view. And only some brain areas are similar to real neural networks. ...

Metodi di registrazione informazione Ci stiamo chiedendo in che modo possiamo registrare attività del cervello e quindi cercare di fare decoding delle informazioni presenti Prima parliamo di alcune tecniche non invasive che ci permettono di vedere alcune attività presenti nel cervello. Metodi macroscopici Functional Magnetic Resonance Imaging Un metodo è fMRI. (ci sono cose ) TODO capire come funziona Electro-Encephalo-Gram EEG che prende direttamente dai segnali Ma il drawback di entrambi è che non registrano attività del singolo array. ...

How are inputs made into motion? We analyze feedback systems in auditory systems in birds. Motivation Birds are very good at producing and reproducing songs by moving their vocal cords complexly (sensory motor learning). We want to learn how they learn and then extrapolate on human or other kinds of speech learning. Birds and Humans do not have much of a common ancestry (last one was fishes). 71% of the birds, both female and male birds sing, for Zebra finch it is a mating behaviour, so only male sing. ...

Associative Conditioning Classical Conditioning First started with associative conditioning, which means cue -> reward signal and similars. Pavlov’s experiment Pavlov was interested in digestive systems of dogs, and discovered this by chance. Then he notices that if we show food to dog, they start to salivate (response to food stimulus). If paired with sound (tuning fork) they start to salivate even if they just hear the sound. He defines two states: ...

This note is just a collection of past useful notes to know to apply machine learning methods for the analysis of topics interesting in the neural sciences. Estimators You need to know all Parametric Modeling. We want to estimate unknown random variables with some observations. Maximum Likelihood See Bayesian Linear Regression. Bias-Variance Decomposition Fisher Information See Parametric Modeling#Fisher information. Applications Echo-locating bats Egyptian fruit flies bats use echo location to locate the target, emitting clicks and capturing echo to navigate the environment. Bats use to click slightly left and right compared to their direction of motion. It is interesting to observe and study how these bats are clicking around to move. ...

The Potassium Exchange values We use the measurement by Cole and Curthis 40mS/cm squared was their measure of Potassium ions leaving the membrane $$ \Delta Q = Idt = GA \Delta E dt $$The potassium concentration is 0.155 moles per litre. Where $G$ is the conductance per unit area, $A$ the membrane surface, $E$ voltage deflection Remember that the conductance is the reciprocal of the resistance, and $V = IR \implies I = \frac{V}{R} = GV$ ...

Vision is THE most important sense for humans. Most of the information we get is through vision 90% vision This is true for humans, but for mice for example it is different, they have probably a 64x64 pixel resolution equivalent. For humans, visual data is more important, it is faster compared to speech and other senses. We can also see this when we are talking about quantity of neurons: 30% of neurons in the cortex are for vision. 8% tactile, touch 3% hearing Rest is for other Precision of human vision Human vision is estimated to be about 576 Megapixels of data (3M snapshots patched together with saccades, that has that pixel image value), since it can distinguish 0.6arc-minutes (0.01 degrees). There is an estimate of about 60kk ± 12kk rods and 3kk ±0.5kk cones. This means that the image is constructed by high resolution saccades (patches). ...

We have a classical exploration-exploitation tradeoff, see Reinforcement Learning, a introduction. Why would animals explore, even if there is no immediate reward based on it? Animals are able to adapt and explore nonetheless. It would be thus nice to understand and implement these features in artificial systems. We will attack this from an evolutionary psychology perspective: Playfulness and intrinsic motivation. Curiosity Here we will talk about why animals are pushed to explore. ...

Here we attempt to answer what is memory, how is it stored and retrieved. Human Memory Definition of Memory Memory is a process by which information is: Encoded Stored Retrieved The brain has different types of memories, and certain brain regions are specialized for this task. Ebbinghaus Curves Other experiments destroy parts of the cortex and correlate this with recall. Types of memory We have the memory pipeline: ...

In general we want to understand how neurons encode the rate and temporal information to build specific features like place cells, grid cells, velocity, head direction, or how it can guide behaviour or coordination. Many neurons encode together some features, it is quite rare that you have the face neuron and similars. Imaging techniques help us to get more information about these parts. Basics of Microscopy Image of a classical microscope, from course slides ...