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Steve Joordens

Lect 14 Sensory processing Transduction (translation process), (how do we get from here to 0101010) Sensory coding- how are they extracted from input? How does changes in environment by translated into 010101010? 010101 is called Morse code. Elementary component. Psychophysics We hear by sound wave, Biological process, interpretation. What puts it all together. There is evidence but no proof. Transduction Sense organ convert environment into energy that brain can understand. Specialized receptor cells. Two types of coding: anatomical coding by means by which our brain represent the outer world. and temporal coding has to do with the means of firing of neurons and then translated to the world, how fast or slow the firing of neurons. Occurs after we understand the coding, occurs after anatomical coding. Sensing the world around us Psychophysics- the study of the relationship between the physical aspects of stimuli and our psychological experience of them. Trys to model how transduction happens. How much stimuli is needed? Develop general laws. Like auditory and visual. Stimulus- energy that produces a response in a sense organ. Varies in both type and intensity Absolute Thresholds The smallest intensity of a stimulus that must be present for it to be detected. When the sound can be heard by a person. Detected 50% of the time., we call it absolute threshold. Sensing the World Around Us Noise- background stimulation that interferes with the perception of other stimuli. Ex. Stuff that interfere with your pure data. Difference Thresholds: Noticing Distinctions Between stimuli Webers law- A basic law of psychophysics stating that a just noticeable difference is in constant proportion to the intensity of an initial stimulus. Two are related. Higher intensity and better the visual, the dots represent different thresholds. JND- Just noticeable Difference Intensity is physical and perception is psychological Lec 15 Vision Light The eye and its functions Transduction of light Eye movements Colour vision Light Electromagnetic energy small portion of light. We see light because it bounces off. Light can be classified by wavelength (physical distance from one wave length to another, changes in wave length is changes in colour, they can wave length from 400 nanometres Next physical property is intensity, amount light that falls on a given object, increase or decrease of brightness Structure of the eye Image is projected to back of eye. This happens through two things: the cornea and lens. Cornea protected outer layer, lens sits behind the pupil. Together they focus the colour of image. The light passes through them. Relaxing and tightening the muscle changes the size of pupil. As that happens the eye regulates how much light comes in. Dim light larger pupil allow more light, vice verse. The role of lens is to focus the light gets to the back for the eye, for it to transduction to the brain. Human eye focus accomplished by the lens its self. When the light reaches the RETINA thin layer, covers the back inside of the eye. It is here where transduction happens. Happens by PHOTORECPTORS. Light transduces from phycial to electrical energy that the brain understands PHOTORECPTOR- many of them in the back of the eye, all react to light. The light causes chemical reaction cause neuron impulse. U dont see through your eyes directly otherwise it will be upside down Travels through optical nerves Each receptor contains a PHTOPIGMEANT which reacts to light. We dont see with our eyes, but with our back of the brain, but we dont know preset location. Brain corrects the inverted image we see. The length of the eye matches the bending of the light ray produced by the cornea and the lens. Sometimes retina needs to correct its slef to get the length of light corrected for proper image. Convex lens correct farness. Recetors two type, rods and cons. 6 million cons and few rods, rods long and thin, cons shot and thick. The cons are concentrated on center of retina, they need alot fof light, compared to rods, used for colour vision and clearity. When we move from bright to dark, it takes 25 min to adjust to lit environment. After hits back of eye rthe light, goes forward, towards to the light. Cons and rods, contacted by polar and from there neurons take to optical nerve and image is flipped and processed by the brain and we see the image. They are like fibres budle up, and those fibres called OPTIC NERVES. They form visual translation cable. Portion of retina where there is a gap is called blind spot. Structure of the eye Sending message from the eye to the brain Bipolar cells-receive information directly from the rods and cones and communicate that information to the ganglion cells Ganglion cells- collect and summarize visual information, which is then moved out of the back of the eyeball and sent to the brain via the optic nerve Eye Movements Vergence movement: no sudden changes. Cooperative movements of the eye. Is keeping focus on finger and moving it back and forth. Saccadic movements: rapid movements of the eyes, used for scanning a visual scene. Moving quickly from one to another image. Look from one spot to another. Pursuit Movements: movements made to keep a moving image on the foveas. Keeps moving and you try to focus on it. Can be related to vergerence movement. Purity: experience, intensity of wavelength. Colour mixing is adding on more wavelengths. Not same as paint mixing. White light is actually combination of all possible wavelength. White is in the middle because combination. Defects in Colour visions Protanopia: red cones filled with green photopigment, Deuteranopia: green cones filled with red photopigment Tritanopia: lack of blue cones McCollough Effect It can last for hours. Red moves to other pigment. Mystery of perception. They believe it has something to do with high level of sighting. Lec 16 Audition Sound The ear and its functions Detection and localizing sounds Age-related losses in hearing Sounds informs us about who we are Physically input received by the auditory system travels as a wave. Unlike light, sounds is mechanical energy. Sound begins with vibrating movement. Vibration pushes air molecules into space and collision occurs, like a travelling chain reaction begins, a chain of traveling and bumping by molecules. PINNA capture sound, and follows it down to the auditory canal and to the ear drum. From there it is going ot travel to a COCHLEA where transduction occurs, the message is sent through the auditory nerve and the brain can help us experience the sound. AMPLITUDE-= height a sound wave reaches, loud has longer wave, increases in amplitude result in loud or soft hearing. Usualyl by loudness. Amplitude of wave measured in Db, highest Db is bass. Frequency- its the rate of vibration of object. The source of sound turns frequency, the number of times the measure wave moves from peak to peak, measured in HERTZ, one cycle per second. High pitch and low pitch. C note on keyboard about 160 hertz. The human hear is sensitive to 20 hertz to 20000 hertz. The frequency that we are most sensitive is speech of 1000 to 5000 hertz. COMPLEXITY the tender of sound. Tender of sounding. Sound travels through hteh PENIA to the sympatic membrance, through vibrating. Transmits vibration through three bumps. The bumps purpose is to intensify the vibration make it vibrant make transduction from air to fluid. The COCKLIY-the mechanically energy gets tranduce to chemical energy. COCKLIY- the third bone in ear is connected to opening in COCKly, it displace flexible membrane called BAZERLER membrane. This membrane vibrates with it. Controls pitches. The close high frequency sound, and further away is low pitch. This is called teh PLACE THEORY, as place changes the pitch changes. THE FREQUENCY THEORY-pitch is determined by the neuron travelling up the auditoy canel. Tiny hair cells called CILIA, extend outward due to sound. Movement of membrane cause CELLI to move up, action potential is released. It is the celli that can be damged due to loud sound. TIMBRE Characteristic of sound. Top of graph a magenta. Underneath that is basic pitch of a sound. Evenly distributed. The curves below it show aplitude and complexity of whay you see in magenta. Together they form a complex tone, at teh top. Harmonics or over tones- unique set of tone each instrument creates. Detecting and locailizing sounds
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