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Cognitive Architectures Introduction to Cognitive Neuroscience Based on book Cognition, Brain and Consciousness ed. Bernard J. Baars courses taught by Prof. Randall O'Reilly, University of Colorado, and Prof. Włodzisław Duch, Uniwersytet Mikołaja Kopernika and http://wikipedia.org/ http://grey.colorado.edu/CompCogNeuro/index.php/CECN_CU_Boulder_OReilly http://grey.colorado.edu/CompCogNeuro/index.php/Main_Page Janusz A. Starzyk EE141 1 … from the brain, and from the brain alone, arise our pleasures, joys, laughter and jokes, as well as our sorrows, pains, grief's and tears. Through it, in particular, we think, see, hear, and distinguish the ugly from the beautiful, the bad from the good, the pleasant from the unpleasant… » Attributed to Hippocrates, 5th century BC EE141 2 2 The Brain ... The most interesting and the most complex object in the known universe How can we understand the workings of the brain? On what level should we attack this question? An external description won’t help much. How can we understand the workings of a TV or computer? Experiments won’t suffice, we must have an understanding of the operating principles. To verify that we understand how it works, we must make a model. 3 EE141 How do we know anything? An important question: how do we know things? Examples: super diet based on dr. K, Chinese medicine and other miracle methods. How do we know that they work? How do we know that they are for real? Gall noticed that the skull shape decides about ones abilities. Thousands of cases confirmed his observations. Craniometry: measuring the bones of the skull to determine intelligence. Do I know or I only believe that I know? Not being certain allows to learn, certainty makes learning difficult. If we know how easy it is to err we could avoid a scientific fallacy. 4 EE141 http://www.harunyahya.com/image/darwinizm_kanli_ideolojisi_fasizm How to understand the brain? To understand: reduce to simpler mechanisms? Which mechanisms? Analogies with computers? RAM, CPU? Logic? Those are poor analogies. Psychology: first you must describe behavior, it looks for explanations most often on a descriptive level, but how to understand them? Physical reductionism: mechanisms of the brain. Reconstructionism: using mechanisms to reconstruct the brain’s functions To create: what must we know in order to create an artificial brain? We can answer many questions only from an ecological and evolutionary perspective: why is the world the way it is? Because that’s how it made itself ... Why does the cortex have a laminar and columnar structure? 5 EE141 From molecules through neural networks 10-10 m, molecular level: ion channels, synapses, properties of cell membranes, biophysics, neurochemistry, psychopharmacology; 10-6 m, single neurons: neurochemistry, biophysics, LTP, neurophysiology, neuron models, specific activity detectors, emerging. 10-4 m, small networks: synchronization of neuron activity, recurrence, neurodynamics, multistable systems, pattern generators, memory, chaotic behaviors, neural encoding; neurophysiology ... 10-3 m, functional neural groups: cortical columns (104-105), group synchronization, population encoding, microcircuits, Local Field Potentials, large-scale neurodynamics, sequential memory, neuroanatomy and neurophysiology. 6 EE141 … to behavior 10-2 m, mesoscope networks: sensory-motor maps, self-organization, field theory, associative memory, theory of continuous areas, EEG, MEG, PET/fMRI imaging methods ... 10-1 m, transcortical fields, functional brain areas: simplified cortical models, subcortical structures, sensory-motor functions, functional integration, higher psychic functions, working memory, consciousness; (neuro)psychology, psychiatry ... Cognitive effects Principles of interactions Neurobiological mechanisms 7 EE141 … to the mind Now a miracle happens ... 1 m, CNS, the whole brain and organism: An interior world arises, intentional behaviors, goal-oriented actions, thought, language, everything that behavioral psychology examines. Approximations of neural models: Finite State Machine, rules of behavior, models based on the knowledge of cognitive mechanisms in artificial intelligence. What happened to the psyche, the internal perspective? Lost in translation: neurons => networks => behavior 8 EE141 Inside the mind “What if … we were magically shrunk and put into someone’s brain while he was thinking. We would see all the pumps, pistons, gears, and levers working away, and we would be able to describe their working completely, in mechanical terms, thereby completely, describing the thought process of the brain. But that description would nowhere contain any mention of thought! It would contain nothing but descriptions of pumps, pistons, levers!’ - Gottfried Leibnitz 1690 EE141 9 Levels of description Summary (Churchland, Sejnowski 1988) Sensing outside and inside the body 10 EE141 Distance – from 10-10 m to one meter Small molecules can change brain functions and resulting behavior. Around year 1800 people were surprised to find out that nitrous oxide (N2O) changes their behavior – it produces small amount of neurotransmitter. 11 11 EE141 Time scales - 10 orders of magnitude Neurons can fire as fast as 1000 Hz. Our brain deals with events on the time range from years to milliseconds. 100ms is about the fastest we can react to an event. – Slower reaction time would prevent humans from protecting themselves from dangers and they would have no chance to survive and reproduce, – faster reaction time would overwhelm the brain to combine sensory inputs and determine the direction and speed of the attacker. Some skills take long time to master like playing guitar or learning how to speak. 12 12 EE141 Working Memory Observations, based on experimental data, are important in cognitive science. Concepts like working memory and their size (7+/-2) are not ‘given’ in nature but are inferred from experimental observations. Emerge from years of testing, working memory proposed after a 2 decade study of immediate memory 13 13 EE141 Neurocognitive Models Computational cognitive neuroscience: detailed models of cognitive functions and neurons. 14 EE141 Model of self-organization Topographical representations in numerous areas of the brain: visual system maps and maps of the auditory cortex. o Model (Kohonen 1981): competition between groups of neurons and local cooperation. Neurons react to signals adjusting their parameters so that similar impulses awaken neighboring neurons. x=data o=weights of neurons x o o o o x o o x o xo o N-dimensional input space o o Weights locate points in N-D neural network w 2-D 15 EE141 Dynamic model Strong feedback, neurodynamics. Hopfield model: associative memory, learning based on Hebb’s law. Vector of input potentials V(0)=Vini , i.e. input = output. Hopfield’s network reaches stationary states, or the answers of the network to the posed question Vini (autoassociation). Vi t 1 sgn I i t 1 sgn WijV j j j 16 EE141 Advantages of model simulations Models help to understand phenomena: enable new inspirations, perspectives on a problem allow to simulate effects of damages and disorders (drugs, poisoning) help to understand behavior models can be formulated on various levels of complexity models of continuous phenomena (e.g. motion or perception) models allow detailed control of experimental conditions and exact analysis of the results Models require exact specification of underlying assumptions: allow for new predictions perform deconstructions of psychological concepts (working memory?) allow to understand the complexity of a problem allow for simplifications enabling analysis of a complex system provide a uniform, cohesive plan of action 17 EE141 Disadvantages of simulations One must consider limitations of designed models: Models are often too simple, they should contain many levels. Models can be too complex, theory may give simpler explanation why there are no hurricanes on the equator? - due to Coriolis effect It’s not always known what to specify in a model. Even if models work, that doesn’t mean that we understand the mechanisms. Many very different models can explain the same phenomenon. Models need to be carefully designed to fit the observations: What’s important in building a model are general rules the more phenomena a model explains, the more plausible and universal it is. Allowing for interaction and emergence is very important. Knowledge acquired from models should accumulate. 18 EE141 Cognitive motivation Although the thinking process seems to be sequential information processing, more detailed models predict parallel processing Transition between conscious and subconscious processes Parallel processing of sensory-motor signals by millions of neurons Specialized areas of memory responsible for various representations e.g. shape, color, space, time Levels of symbolic representation More diffuse and fuzzy than binary logic Learning mechanisms as a foundation for cognitive science When you learn, you change the method of information processing in your brain Resonance between ”bottom-up” representation and ”top-down” understanding Prediction and competition of ideas 19 EE141 Brain Landmarks Most terms in neuroscience are Latin names. Medial (midline) view of the brain also called mid-sagittal is a slice from the nose to the back of the head. Corpus callosum is a fiber bridge flowing between right and left hemispheres, begins behind the frontal lobe and loops up and ends in front of the cerebellum. 20 20 EE141 Brain Landmarks Lateral (side) view of left hemisphere is shown here. Folds in the cortex are important part of anatomy. Longitudinal fissure runs along the midline between right and left hemispheres. Lateral sulcus runs forward at a slant along the side of the brain and divides the temporal lobe from the main cortex. Central sulcus divides the rear half (posterior half) of the brain from the frontal lobe. EE141 21 21 Brain Landmarks Temporal lobe points in the direction of the eye. The three major planes of section (cuts) are: Vertical section (sagittal) from the front of the brain to the back. – Slice through the midline is called midsagittal. Horizontal slice. Coronal section (named for its crown shape). 22 EE141 Body Landmarks The three major planes of section : Vertical section (sagittal) from the front to the back. Horizontal (transverse) section. Frontal (coronal in the brain) section. Other important directions: Superior (dorsal) and inferior (ventral) Medial and lateral Anterior (rostral) and posterior (caudal). EE141 23 Mind and Brain Visual perception: viewing natural imagery we must understand ways of encoding objects and scenes. Spatial awareness: considering the interaction between streams of visual information will let us simulate concentration Memory: modeling hippocampal structures allows us to understand various aspects of episodic memory, and learning mechanisms show how semantic memory arises. Working memory: explaining the capacity to simultaneously hold in the mind several numbers, while performing calculations requires specific mechanisms in the neural model. 24 EE141 Mind and Brain Andreas Vesalius (1514-1564), a Belgian physician, published the first known detailed anatomy based on dissections of human body. He showed that both men and women have the same number of ribs. Illustrations, like the brain shown here, were done by Titian. 25 25 EE141 Mind and Brain Paintings, like the Rembrandt (The Anatomy Lesson of Dr.Tulp), show the excitement generated by dissection of human body. René Descartes (1596 -1650) a mathematician and philosopher is considered as the originator of modern mind/body philosophy. He said most famously, cogito ergo sum ("I think, therefore I am"). Thinking is thus every activity of a person of which he is immediately conscious. Descartes' "error" pointed by António R. Damásio was the separation of mind and body. 26 26 EE141 Mind and Brain Charles Darwin (1809 –1882) wrote a book “Expression of emotions in man and animals” pointing towards biological origins of emotions and not just cultural as people thought. He also stressed the importance of culture and environment, that helps to resolve “nature vs nurture” debate. 27 27 EE141 Mind and Brain Santiago Ramon y Cajal (1852–1934) founder of brain science studied properties of neurons. He observed neurons under microscope and showed that they are single cells that end with synapses Nerve impulses travel down the axon to synapses In 1952 Hodgkin and Huxley constructed action potential model for a spiking neuron 28 28 EE141 Neurons Cajal’s drawing of a slice of chicken brain exposed using Gogli staining method A Modern version 29 EE141 Mind and Brain Pierre Paul Broca (18241880) discovered the region in the brain responsible for speech production In 1861 he studied a patient with epilepsy who lost ability to speak On the patient’s death Broca performed autopsy and showed a damage to the posterior part of the third frontal convolution in the left hemisphere and associated it to speech production Much of what we know about brain was first discovered by studying various deficits 30 30 EE141 Mind and Brain Wernicke’s area (W), in the left upper part of the temporal lobe is responsible for receptive language (understanding). Carl Wernicke (1848-1905) published his finding shortly after Broca’s work The two areas are connected for speech comprehension and production. Damage (in or near) leads to: Broca’s area (B): Expressive aphasia, Wernicke’s area (W): Receptive aphasia, Fibers between B & W: Disconnection aphasia. 31 EE141 Mind and Brain Left hemisphere is responsible for language production and listening while right hemisphere is concerned with emotional aspects of language. Angelo Mosso (1846-1910), found a way to measure blood pressure during demanding mental tasks. Mosso’s work anticipated current measures of brain blood flow like fMRI. fMRI measures local blood flow changes in the brain. The fMRI shows whenever some brain regions require more oxygen and glucose. 32 32 EE141 Mind and Brain Nineteen century scientists were very interested in consciousness. William James (1890) declared psychology as a science of conscious mental life. Many scientists (Helmholtz, Loeb, Pavlov) disagreed – they took on a physicalistic view of mental life. Pavlov experiments with dogs (1900) on classical conditioning convinced psychologists that all behavior can be derived from simple reflexes. 33 33 EE141 Mind and Brain In 1970-ies many scientists were dissatisfied with behaviorism. Different methods of testing conscious and unconscious brain events were developed Figure compares results of study using visual backward masking method based on fMRI to compare brain activity for conscious and unconscious visual words. 34 34 EE141 Conclusion Debates in cognitive neuroscience: Local vs distributed functions in brain The question of consciousness Unconscious inferences in vision Capacity limits in the brain Short-term and long-term memory – separate or not? The biological basis of emotions Nature vs nurture – genes vs environment http://psychandneuro.duke.edu Cognitive neuroscience combines psychology, neuroscience and biology to answer questions about mind and brain. Modeling cognitive functions of the brain helps to understand psychological phenomena and predict behavior. It may simplify complex cognitive processing with full control of experimental conditions. It helps to build working models of embodied intelligence 35 35 EE141