1 13 What do you know to be true Rene Descartes 1596 1650 1 all things he knows comes from his senses not the first to say this looked at what he knows and realized everything he knows comes from his senses 2 senses sometimes deceive him illusions one of the things he was concerned with was a stick in water takes the hard line and won t believe his senses thinks there is more than that worried about what he knows and believes so how does he know there isn t some evil genius his word plugged into his senses trying to deceive him at every turn he can t be sure 3 sometimes he dreams and his dreams appear real if theres an evil genius fooling you then your thoughts about your senses are real your senses of what you perceive might not be but the thought is real 4 an evil genius could be manipulating his senses 5 the only thing he can be sure of is Cogito Ergo Sum SENSES physiological functions for converting particular environmental features into electrochemical signals Three Problems 1 Radical Skepticism We can believe nothing about our world 2 Dualism the body and soul are separate a Philosophical questions 3 Materialism our perceptual world a Ex consciousness is an emergent property of our own body s activity b Everything you experience are a product of your brain one of those things that you experience are coming out of what you think Our perception is not the same as the physical world na ve realism we see world a certain way because that is the way the world really is we can t perceive what we can t sense how do electronics work the different smells dogs smell differently 1 our sensory range is limited but our waves have expanded to what we didn t know we had but can use 2 just because we can sense something doesn t mean we perceive it detect it 3 our perceptions are seldom in line with the exact physical situation seeing things upside down reality shaped not only by senses but by brains brains face recognizing machines if damaged can t recognize faces Perception Does not Just Happen we have to mix it into environment physics organism biology perception psychology 1 physiology 2 physiological psychology biopsychology 3 psychophysics Why do we study perception practical 1 when observations turn out be in error it may lead to accidents 2 we may want to replace the real world with some specially prepared substitute 3 we may wish to use a machine to replace or supplement human observer 4 medical diagnosis or treatment 5 perceptual questions concerning consumer preference in order for psychology to be useful behavior must be lawful 1 16 Brains brains From Different Mammals have Similar Structures nervous system structure of the nervous system tells us about brain function brains are also similar in development pattern of brain development is also very similar across species all brains contain neurons cells of the nervous system that produce transmit info carrying signals 10 billion to a trillion neurons in the brain many different sizes really really tiny to really really big big vs small determines the function of the neuron different types of task for each neuron communication with neuron Basics of Neural Signals neural signals are info carrying electrochemical signals produced transmited by neurons neurons are surrounded by a solution containing ions an atom that has an imbalance in the number of protons electrons that therefore has an electric charge ions carry an electrical charge sodium ions Na positive charge chlorine ions Cl negative charge potassium ions K positive charge electrical signals are generated when such ions cross the membranes of neurons membranes have selective permeability electricity is transmitted in neurons by changes in the membrane potential difference in electrical potential across cell membrance due to a difference in the concentrations of positive negative ions inside outside the cell membrane potential determined by voltage gated ion channels ion channels small pores in the cell membrane of neurons through which certain ions can flow into or out of the cell gate keeper that says what type of ions can get in if you give the ion channels a little bit of a jolt electricity or right chemicals it will open up and sodium ions will rush in normal resting depolarized polarized hyperpolarized sodium pump which brings it back to normal action potential electrochemical signal that begins in the dendrites of a neuron and travels down the axon to the axon terminals of a neuron sodium ions rush up at rest sodium ions on the outside potassium on the inside potassium ions rush down and out Properties of Action Potentials Action potentials stronger touch signals go closer together show propagated response remain the same size regardless of stimulus intensity increase in rate to increase in stimulus intensity have a refractory period follows an action potential where a brief period during which a new action potential cannot be initiated of 1 ms upper firing rate is 500 to 800 impulses per second show spontaneous activity that occurs without stimulation in a given neuron action potentials are always the same size stimulus intensity is encoded by the rate of the spikes in brain graph ion channels are opening and closing spike carries information Communication between Neurons billions of neurons that are all interconnected and each neuron has to communicate with eachother when action potential gets to final end of neuron end of axon projection that emanates from the cell body of a neuron receive signals from other neurons there is another neuron that they need to talk to Synaptic Transmission of Neural Impulses across a Neuron neurotransmitters chemical substances involved in the transmission of signals btwn neurons molecules relased into a synapse by the neuron sending a signal bind to receptors on the neuron receiving the signal are released by the presynaptic neuron from vesicles received by the postsynaptic neuron on receptor sites matched like a key to a lock into specific receptor sites see powerpoint Type of Neurotransmitters excitatory transmitters excitatory effect on postsynaptic neuron increases the probability that an action potential will be initiated cause depolarization inflow of positively charged ions causes the membrane potential to become markedly more positive neuron becomes more positive increases the likelihood of an action potential inhibitory transmitters inhibitory effect on postsynaptic neuron decreases probability that an action potential will