Midterm 1 notes - Instructor: Dr. James Reichert PDF

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Instructor: Dr. James Reichert...

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Chapter 1 - Psychology origins o Aristotle  Psyche: “the mind” – source of all human behaviour  Role of the brain      o

Rene Descartes and dualism  A nonmaterial mind governs advanced cognition  Body and brain direct all basic behaviours   

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The mind is outside the body The brain and body direct basic behaviours (5 senses) The brain is not involved in advanced cognition

Immanuel Kant  The critique of pure reason  Human experience is drawn from the structure of the mind  Human commonalities in thinking and reasoning   

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He didn’t feel this ability could be contained Within the biological body and therefore came up with The mind as an outside source of the body Memories were stored in the heart The mind cant die as it lives outside the body

Doesn’t define what the mind is All humans have the same structure Humans can come to a broad consciousness

Early psychologists o Science of the mind – goal to legitimize the study of psychology o Wilhelm Wundt  First experimental psychology lab  Introspection o o

Early psychologists wanted to legitimatize Psychology and make it scientific Introspection: you can put a person in an experiment and present them with a stimulus and get them to respond

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Used psychophysics experiments to measure human sensations Developed laws of perception that still apply today Break down the human sensation experience (5 senses) Finding out the quietest sounds we can hear, dimmest lights, slightest taste

Gustav Fechner  Founder of psychophysics – used physics and math to study the mind o Ernst weber  Measured sensitivity threshold Measuring thresholds o Perception of physical stimuli can be measured in either absolute thresholds or difference or difference thresholds o Absolute threshold measures the detection of a stimulus from zero (e.g. the faintest light, the quietest sound)

Difference threshold measures the detection of a change in a stimulus – how much of a difference is needed before it can be detected Absolute threshold: method of adjustment o The person being experimented on has control over the stimulus Absolute threshold: method of limits o Limits are set on the high and low side o Multiple trials are done starting at the high end (sounds you hear) then the next trial starting on the low end (sounds you can’t hear) o By doing this you get a mean value that is the absolute threshold for that person Absolute threshold: method of constant stimuli o The level of sound someone hears 50% of the time is the absolute threshold Staircase method o Increase from low to high asking if they hear it or not o When they say yes you go back down until they say no then back up till they say yes again and repeat. Difference threshold o Just noticeable difference o Expressed as a weber fraction o Can you detect a change in stimuli o When you add the weight do you notice o More likely to notice on the smaller weight o What is the minimum amount you can detect Magnitude estimation o Magnitude estimation experiments measure sensitivity to change o How much change do you perceive o Response compression: not as sensitive to the change in stimuli o Response expansion: extra sensitive to the change in stimuli (typically goes with painful stimulus) From sensation to perception o Distal stimuli  proximal stimuli  transduction  perception o

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Distal stimuli: what is happening, what you are doing Proximal stimuli: how the outside stimuli is being converted into a physical sensation (how is the stimuli entering your body) Transduction: physical energy (stimulus) is converted into neural signal Perception: conscious of what's happening

Bottom up information: early sensation, information is perceived by specific neurons. Information contained in neural signals from receptors o Top down information: the energy travels in the brain to somewhere that can make sense of what is happening. Observers knowledge, expectations and goals which can affect perception Neural communication o Is an extremely fast process o Electrical signals get passed between neurons Structure of a neuron

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Dendrite: receives the information Nucleus: the “brain” Cell body: contains the nucleus, all functions occur here Axon: where the neuron generates a signal Axon terminal: connect to the dendrites of another neuron Receive information from one neuron and pass it on to another

Action potential o The connection between two neurons is called a synapse o Synapse: is a little gap where the electrical signal passes from neuron to neuron o Action potentials are all or none o Speed at which the action potential travels down the axon of a given neuron is always the same, although the speed can differ in different neurons o Characteristics of an inducing stimulus reflected in neuron’s firing rate o Action potential is an electrical wave that travels along the axon o The strength of the wave remains constant o One size of an action potential o Doesn’t lose any strength as it travels down the axon o Strength of the stimulus doesn’t matter o The strength of the stimulus doesn’t increase the strength of the action potential, rather increase the rate of the action potential o Stronger stimulus induces action potentials with a higher firing rate The human brain o 1.35kg about 3lbs o 100 billion neurons in a healthy adult brain Divisions of the brain o Temporal lobe: auditory processing, language and memory, taste and smell o Frontal lobe: planning, organizing and motor control o Parietal lobe: touch and spatial awareness o Occipital lobe: visual processing o Cerebellum: movement and coordination o Forebrain (cortex): responsible for most complex behaviours o Brainstem: source of much of our unconscious behaviours that are critical for survival Directions of the brain o Dorsal: structures atop the brain o Ventral: structures towards the bottom of the brain o Medial: structures toward the midline of the brain o Lateral: structures towards the sides of the brain o Anterior: structures towards the front of the brain o Posterior: structures towards the back of the brain Anatomical orientation o Coronal: cut from top to bottom o Horizontal: cut anterior to posterior

Sagittal: cut about the midline - Cerebral hemispheres o Two specialized halves connected by the corpus callosum o Very similar in structure o Corpus callosum allows the two hemispheres to communicate - Blood circulation in the brain o Blood delivers oxygen to the brain, parts that are active require more oxygen - Studying sensation and perception o Most basic problems can be measured fairly simply at the sensory levels  Vision problems - Visual agnosia o An inability to recognize objects or forms o Not a problem of the visual system but in the brain o Can tell what it is but not what it does - Prosopagnosia o Unable to recognize faces* - Techniques for studying the brain o Histology  The brain is sectioned and sliced post mortem and neuronal loss is examined  Can examine in a very detailed way  Most precise way to study the brain o PET scanning  Detects compounds in blood such as glucose  Radioactive “tracer’  A person is awake and doing a task to see which parts of the brain re active during different situations o Functional magnetic imaging (fMRI)  Changes in oxygen content of the blood alters its magnetic properties  “functional” used while a person carries out a task  Detects areas that are more active during a task o Near-infrared spectroscopy  The use of light, shine light onto the skill  Unable to penetrate deeply Chapter 2 - Light waves o Amplitude: the height of the waves o Wavelength = distance between waves o The higher the wave the brighter the light - Electromagnetic spectrum o Very small part is visible to humans o Certain animals can see infrared o Longer the waves the more harmful o

The shorter the waves the more dangerous they are Optic array o Is constantly changing Field of view o Frontal eye position  Used to guide movement of hands and fingers  Allow high-resolution depth perception  Little bit of overlap with each eye allows for better perception  Limited field of view o Lateral eye position  Sacrifice binocular depth perception for expanded field of view  No overlap view in the front, not as good of depth perception  Can see more area around their head Anatomy of the eye o

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Sclera: white part of the eye, protective covering Choroid: at the back of the eye, allows blood to send nutrients and oxygen to the eye Cornea: protects things from getting in the eye, focuses images Iris: coloured part of the eye Pupil: center of the iris, regulated amount of light let in Retina: where the light is projected, turns light into a neural signal Lens: main focusing part of the eye, bends light and projects it to the back of the eye Fovea: the center of the field of view

Iris and pupil o In bright light, the iris contracts which constricts the pupil o In medium light, the iris contracts less which dilates the pupil o In dim light, the iris is fully relaxed, and the pupil is fully dilated Myopia (nearsightedness) o Focus point falls short of the retina  Lens bends light too much o Can see images that are close but not far o Eyeball can also be too long causing myopia Hyperopia (farsightedness) o Ideal focus point falls beyond the retina  Lens too rigid and fails to bend light enough o Can see things far but not close o Eyeball can be too short Retina o The image projected onto the retina is upside down Cell organization of cells in the retina o Five types of cells in the retina  Receptors: respond to light, a chemical reaction occurs and the receptors turn light into a neural signal, located at the furthest point from the light source

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Horizontal cells: signal horizontal between receptors, allow communication between receptors  Bipolar cells: pass the signal from the receptors to the ganglion cells.  Amacrine cells: allow communication between ganglion cells  Ganglion cells: the axon forms the optic nerve o Cells are organized into sperate layers and certain cells communicate with other cells Receptors o Receptors convert light energy into a neural signal o Respond in a chemical reaction to light o Two types:  Rods: specialized for low light  Cones: specialized for normal light and colour perception Isomerization o The process by which receptors respond to light o Retinal separates from opsin in response to light, cannot send another signal until retinal reattaches Spectral sensitivity of rods and cones o 3 types of cones:  Short wavelength: respond to short wave lengths  Sensitive between 380-550  Most sensitive at: 443  Medium wavelength: respond to medium length waves  Sensitive between 400-700  Most sensitive at: 543  Long wavelength: respond to long length waves  Sensitive between 400-700  Most sensitive at: 574 Distribution of rods and cones o Have way more rods than cones o 120 million rods o Cones are concentrated in the fovea o Rods are all over the eye except in the fovea Measuring light sensitivity o Dark adaptation  

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When going from bright to dark you see nothing at first after a while you begin to see little pieces of light In an experiment you go into a room and are told to focus on a light, from there you are told to dim the light until you are unable to see the light, the experimenter then turns the rooms lights off so the only light is the test light, continue to stare and turn it down till you can no longer see it What will happen is you will turn it down till you cant see it but if you wait a little your sensitivity increases and you will be able to see the light again

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 Rods are much more sensitive than cones Disorders of the eye o o o o o o o

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The goal here is to wait till you reach maximum sensitivity, no matter how long you wait you can no longer see the light Looking directly at the light measures cones Doing the same experiment but looking at the fixation point measure rods

Macular degeneration: results from the loss of cones in the fovea, essentially the person gets a blind spot in their visual field Retinitis pigmentosa: loss of rods along the periphery, results in tunnel vision Presbyopia: point of where you can read a book from, more comfortable further away Strabismus: the muscle of the eyes get weakened, usually happens with one eye, can result in double vision, get a wandering eye Amblyopia: one of the eyes doesn’t develop properly so they cant see out of one eye Astigmatism: flaw in cornea or lens, images aren't focused on the retina properly Cataracts: age related, clouding of the lens

Ganglion cell receptive fields o The cells provide you with the full image, by combining all the receptive fields you are able to see to get the whole image o There are more than 20 types of RGCs in the retina - Overlapping receptive fields o Neighboring retinal ganglion cells receive their inputs from an overlapping set of photoreceptors o The receptive field of retinal ganglion cells overlap extensively so any two adjacent fields look almost the same - Ganglion cell receptive fields o Center surround receptive field: the center of the receptive field responds differently to stimulation than does the surrounding portion o On center receptive fields: increase in firing rate when the amount of light striking the center of the receptive field increases relative to the amount of light striking the surround o Preferred stimulus: for ganglion cells with on center receptive fields, the preferred stimulus is a spot of light that exactly fills the center of the receptive field o Off center receptive fields: respond optimally when light is shined on the surrounding area of the receptor field - Lateral inhibitions o is the process in which photoreceptor cells aid the brain in perceiving contrast within an image Chapter 3 - The optic nerve o The neural signal exits the retina along axons of ganglion cells that form the optic nerve o The optic disc is a blind spot in the eye - Recording along the optic nerve

Recording of fibers along the optic nerve while visual images are presented to the eye Receptive fields o Recording from individual ganglion cell fibers that make up the optic nerve  The fiber responds only when a small area of the retina is illuminated  Receptive field o Receptive fields of fibers overlap  Shining a light on a specific spot on the retina can activate several ganglion cell fibers  The collective receptive fields of ganglion fibers allows for coverage of the entire retina Ganglion cell receptive field o Each ganglion cell responds to a round portion of the visual field o Ganglion cells can provide coverage and light/dark contrast within the visual field but not detail The visual pathway o Hubel and Wiesel studied receptive fields of neurons along the visual pathway o Neurons respond differently at different points along the pathway o Receptive fields of neurons in visual cortex more specific o Eye  optic nerve  lateral geniculate nucleus (LGN)  visual cortex o Once in the visual cortex the receptive fields become more specific Pathways from the retina to the brain o Left visual field projects to the right hemisphere o Right visual field projects to the left hemisphere o

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Visual pathway o Optic chiasm: point where some visual signals cross over to the opposite hemisphere  Signals from the right half of each retina (left visual field) stay in the right hemisphere  Signals from the left half of each retina (right visual field) stay in the left hemisphere

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Optic nerve  optic tract  lateral geniculate nucleus (LGN)  visual cortex  Optic nerve  optic tract  superior colliculus Pathway from retina to brain o The optic nerves – consisting of the bundled axons of the retinal ganglion cells – leave the eyes at each optic disk and meet at the optic chiasm, where they split apart and rebundle as the optic tracts o Neural signals from the left visual field project to the right hemisphere. Signals from the right visual field project to the left hemisphere o Some signals branch off from the optic tracts and travel to the superior colliculus and to other structures Secondary pathways o Tectopulvinar pathway  A subset of visual signals travel to the superior colliculus in the midbrain  Forms part of the “tectum”  Allows you to tract visual signals and maintain eye movement o Retinohypothalamic pathway  A small portion of signals make connections with the suprachiasmatic nucleus (SCN) in the hypothalamus  Sensitive to the brightness, is your internal clock, tells you when its time to be sleepy Geniculostriate pathway o Most signals along the optic tract synapse on neurons in the LGN (thalamus)  Singla project back and forth from the visual cortex  90% of signals travel along this path o Neural signals that travel to the LGN to the visual cortex (striate cortex) from increasingly complex networks  Retinotopic mapping: recreating the visual field projected onto the retina  Is constructed within the LGN o Each area on the retina has a corresponding are in the LGN  Functional specialization: cells responding to specific types of images o Signals become more streamlined between the retina and visual cortex  Signals are being refined through this process o Despite the organization within the LGN the visual image remains unrefined  If you stop here you don’t get a precise image Lateral geniculate nucleus (LGN) o Made up of 5 layers  Magnocellular are layers that get their information from rods and process information related to motion  Make up layer 1 and 2  Parvocellular are layers that get signals from cones, information about the colour and shape of the object  Make up layer 3 ,4, and 5

Each layer receives signals from one eye only Primary visual cortex (Area V1) o Entry point into the visual cortex from the LGN o Organized into columns based on location within the visual field Cortical location columns o Individual locations within the visual fields are segregated o Locations that are near each other on the retina are also physically near each other in the visual cortex Receptive fields of neurons in the visual cortex o Hubel and Wiesel documented the role of the visual cortex in vision  Flashed lights on the retina and recorded from neurons firing in the visual cortex o Within each location column there are different types of cells that process specific types of visual information within that location  Simple cells: respond optimally to a specific signal, deviation from the specific signal causes the cell to get weaker and weaker  Respond to static images  Complex cells: respond optimally to a specific signal, deviation from the specific signal causes the cell to get weaker and weaker  Responds to movement of lines Receptive field of simple cells o Simple cells help define line of orientation that allow for fine detail discrimination o Each location column contains enough simple cells to process all possible lines of orientation Receptive fields of complex cells o Different cells are sensitive to lines of specific orientation and moving in a specific direction Cortical magnification o Fixation point reflect on the fovea, most important part of the visual field o The fovea is small but is given more cortical real estate as it takes up more space and more cells are processing it because it is more important The visual cortex and beyond o Area V4 (visual cortex): responsible for colour processing o Area...