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08/21/19: Perceptual Process

What do you think are some of the steps that bring us from the thing that is out there in the world, to actually interacting with what is out there? -

Some of the steps include an environmental stimulus, such as a tree, the reflection of light, this light reaches the receptors, and then there is perception, recognition, and action. This does not always follow along linearly however.

The Perceptual Process 1. 2. 3. 4. 5. 6. 7. -

Environmental stimulus: ex smelling cookies, seeing a rainbow Stimulus on the receptors: ex for hearing = soundwaves, seeing = light Transduction: electrical signals Procession: after signals are received, the brain is going to process it Perception Recognition: taking whatever you perceive and put it into a category Action Knowledge plays a role in some of these processes. Which ones do you think it plays a role in? o I think it definitely plays a role in recognition and action. Another role is perception because for ex: last time we looked at a dress, we perceived the dress in a specific way, whatever light we’re interpreting that dress in is based on previous experience.

*** PROF SAYS BOOK IS WRONG Bottom-up = just pure data coming in, transduction occurs, but interpretation hasn’t occurred yet Top-down = interpretation Most perceptions involve both processes; every perception has to start with bottom-up processing Bottom-up vs Top-down Processing 12 13 14 14 16

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A 13 C D E

PQR5T 08/23/19: Methods and Neural Firing

Methods of Studying Sensation and Perception Levels of analysis -

Psychophysical level – stimulus and perception/behavior o Fechner’s Classical psychophysical methods o Magnitude Estimation o Recognition Testing o Reaction Time

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o Phenomenological Report o Physical Tasks and Judgement Physiological Level – stimulus and physiology/physiology and perception o Neural Recording o Brain Imaging

Thresholds -

Absolute threshold- smallest amount of a stimulus energy necessary to detect a stimulus What is an example of something that measuring a threshold could tell us about perception? o Thresholds are important for noticing if something is wrong (can’t hear, see, etc.)

Gustav Fechner -

Developed methods to measure the relationships between stimuli and perceptions His methods (3 methods) were the classic psychophysical methods

Method of Limits -

Stimuli presented in ascending or descending order o Person replies Yes or no Why is it important to vary between ascending and descending trials? Why is it important to vary the starting point between blocks? o Because otherwise people could cheat and notice the pattern

Method of Adjustment -

Continuous (vs. stepwise) Adjust stimulus until you can barely detect it

Method of Constant Stimuli -

5-9 stimuli presented in random order a number of times Threshold is the stimuli that is detected 50% of the time

Classical Psychophysical Methods -

Which of these would be the fastest to conduct? Method of adjustment Which would have the most bias? Method of adjustment thought to have the most bias because since you’re the one adjusting it, and so you believe you can still perceive it How about the least? Method of constant stimuli

How do we get rid of bias? -

Forced choice procedure o Two time intervals o Once without stimulus o Can be combined with Method of Limits of Method of Constant Stimuli o For which of these senses would this method work?  Seeing, hearing, touch, taste, pain, smell, for all of these senses!!

To Be Continued…. 08/26/19: Methods and Neural Firing Continued Ernst Weber -

Difference threshold- smallest difference between two stimuli that can be detected by the subject. o What types of stimuli can be tested? Weight, light, color, volume, can be done for any sense!! o What happens to the DL when you move from a 100g standard to a 200g standard? As the weight is getting heavier, the amount, difference is going up

Weber’s Law -

DL= K x S S= intensity of the standard K is a constant (different for different types of stimuli) Describe in words the relationship between the Standard and the Difference Threshold o As the Standard increases, the Difference increases o Absolute= the second that you detect the stimuli, it crosses your absolute threshold o Difference= being able to tell the difference between two different levels of stimuli (volume at 20 compared to volume at 10)

Magnitude Estimation -

We tend to underestimate brightness We tend to overestimate electric shock We tend to accurately judge apparent length

Recognition Testing -

Smell and eye chart= example of recognition testing; doctors test visual and hearing acuity

Reaction Time -

Stroop test- reading font color vs color being worded

Phenomenological Report

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What phenomenological reports have you given during the first couple of classes? o The dress o The black and white spotted cow and dog Describing what you see = phenomenological report

Methods of Studying Sensation and perception: Levels of Analysis -

Physiological level o Stimulus and physiology and perception o Neural recording o Brain imaging

Neurons -

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Dendrites, soma, axon D and A are both processes extending from the soma but, what are the main differences between them? o Dendrites receive information and axons send it o Dendrites are short, axons are long o Lots of dendrites, and one axon Electrical signals travel from neuron to neuron converting the stimulus into the perception of the stimulus…how? o Neurons receive a signal that is in either a chemical form or physical form  Receptor cells (sensory neuron)  Interneurons  These neurons bind to the dendrites  Physical = receptor neurons  Chemical = neuron to neuron in form of chemical signals o Sodium diffuses down through the dendrites and cell body  Not active process  Once they flow in, they drift throughout the water  All through dendrites and cell body, it’s just drifting o The electrical signal is activated and travels quickly down the axon to the axon terminals  What are some things that determine whether that signal is strong enough?  How many different signals are coming in, vs if a lot of signals are coming in  Inhibitory responses would decrease the current coming in  How close to the axon are the dendrites  The resting potential for most neurons is between -60 and -80 millivolts (inside cells)  Action potentials  A process that only occurs in axons  Actions potentials can travel at speeds up to 100m/sec  Action potentials remain constant in strength as they move, so signals are transmitted without loss

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Once threshold is reached, sodium channels open (inside of cell becomes more positive), triggers potassium channels to open (inside of cell become positively charged)  Sodium and potassium are positive  The axon is then returned to its resting potential The ion pump restores the normal distribution of Na+ and K+ ions (only part that uses energy)

TBC 08/28/19: Neural Firing Continued… Recap: -

Sodium channels open, sodium flows into cell, and potassium channels will be triggered to open because of positivity, and sodium channels close, and potassium flows out of cell. All or None Law: neuron fires or doesn’t, which depends if the sodium drifts fast/strong enough to pass through the threshold

Neuronal Activity -

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What can we learn from the Neuronal Activity? o A microelectrode can be carefully inserted into the axon of the cell so the firing rate of that cell can be recorded Pros of single cell recording? o Single cell recording can give us really precise info about timing of firing o Can tell precisely where in the brain something is happening, can tell spatial resolution Cons of single cell recording? o Can only see activity of one cell at a time, and our system consists of multiple cells o Very rarely can one use human participants for single cell recording; most come from animals, esp. cats o Have to have good idea of what specific stimulus is going to make that cell fire

Finding the receptive field of a cell -

The specific area of screen is illuminated, in which the monkey’s cell starts to fire rapidly, but if it isn’t in that specific are, then the cell fires more slowly in the image displayed on powerpoint

The End… Light, the Eye & Disorders of the Eye -

Environmental Stimulus- The actual object in the outside world Stimulus on the receptors-For the case of vision, the image that is cast on the retina Visual information is contained in light that is reflected from the environmental stimulus

Light travels in waves -

What are some of the ways light waves can vary? o Wave lengths

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Describe in your own words the relationship between wavelength and perception based on this image. o Wavelength is related to perception of color. For example, bigger wavelengths might be red, orange, and smaller wavelengths might be violet

The Electromagnetic Spectrum -

We can only see a small portion of the electromagnetic spectrum.

Brightness -

Larger waves = brighter perception Smaller waves = dimmer perception

Light also varies in purity -

Perception of saturation How much white/black is mixed in So what we experience as different colors are just different wavelengths of light that are being reflected into our eye o Blue birds are actually not blue! Color is a creation of our mind, there is no way to tell if one’s red is perceived the same as another person’s red o Blue jays have black melanin layer, and spongy carotin, the way sunlight bounces off and only blue wavelengths are reflected off. If feathers were grounded up, the feathers would actually look greyish o Ex: oil spill, sometimes one can see rainbow because of wavelengths/light reflected

The Cornea and the Sclera -

Cornea: o Main focusing part of the eye, does 80% focusing of the eye. When light comes in, it bends to be focused on the retina

The Pupil and the Iris -

Iris= colorful ring Pupil = opening in the center of the iris

The Lens and aqueous and vitreous humors -

Lens = does rest of focusing Aqueous humor = in front of lens Vitreous humor = jellylike fluid behind lens

Lens Accommodation -

When something is far away, cornea does most of bending The eye accommodates for close vision by tightening the ciliary muscles, allowing the pliable crystalline lens to become more rounded

The Retina

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Healthy retina = rosy color In middle is fovea with tightly packed cones Optic nerve where nerves take information and send it to brain

The Optic Nerve -

Cells gather in the back and exit towards the brain This occurs at the optic disc On this small part of the retina, there are no receptors

Disorders of the Eye -

Eye vision tests o Puffer of air o Tap eyeball o Line of light across eye o Bright flash of green light o Dilate

TBC… 08/30/19: Disorders of the Eye Continued **The myelinated sheath also saves energy** **Which step in perceptual process is most likely to inly include bottom-up? Transduction** Astimatism -

With Astigmatism, the cornea is misshapen causing a blurred distorted image. The optical power of the eye is different for different orientations Easily corrected with corrective lenses

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Specifically problems with orientations that are not reflefcting properly. For each individual misshapenness, there are going to be different orientations

Cataracts -

Lens does not work Gunk such as protein has built up in the lens Common in older people and older dogs Surgery to fix cataracts o Cut through cornea o Take lens out and break it down, and suck out pieces of lens they have broken down and insert artificial lens  False lens can no longer perform accommodation however, so now they will need to wear bifocals when having images closer to face

Myopia -

Nearsightedness More common, because people are spending more time indoors, children in particular With myopia, objects viewed at distances appear blurry and out of focus Eyeballs are becoming longer, and light is becoming eyeballs from growing Light that is entering the eye from far away is bent too much and image is focused in front on the retina

Hyperopia -

While some one with myopia can see things in the distance clearly, a hyperopic eye is unable to see things that are close clearly In hyperopia, the light is not bent enough and the image is focused on the retina

Presbyopia -

With age, the lens becomes stiff and muscles become weaker and loses its ability to accommodate Cannot see things close up, so need reading glasses

Optic Nerve Damage: Glaucoma -

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Lose peripheral vision, until it becomes coming in, leading to tunnel vision The optic never and aqueous humor are causal of glaucoma The aqueous is drained and pigments can end up blocking the drainage, so the pressure starts to build up in the eye and as the pressure increases, the optic nerve gets crushed, hence leading to tunnel vision With glaucoma, the flow of the aqueous humor is obstructed Pressure begins to build up in the eye putting pressure on the optic nerve Can be permanent if not treated

Solar Retinopathy -

Symptoms typically show up about 12 hours after the viewing event

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o Blurry vision o A central blind spot in one or both eyes o Increased sensitivity to light o Distorted vision o Changes in the way you see color, known as “chromatopsia” Many people with solar retinopathy recover from their symptoms, but some have lasting vision problems Retina becomes bleached by sun, a healthy retina is a rosy color

Diabetic Retinopathy -

In diabetic retinopathy, areas of the visual field are splotchy Blood vessels on the front surface of the eye become leaky and as the blood pools it cases blind spots Splotchy areas are where pools of blood have formed

Macular Degeneration -

With macular degeneration, the only thing you can’t see, is the thing you are trying to look at Opposite effect of glaucoma which starts at peripheral Causes are nature-nurture, genetic predisposition, increased risk if smoking

Retinitis Pigmentosa -

Opposite effect of macular degeneration Also tunnel vision, from outside working its way in

The End 09/04/19: The Retina **For Friday: read up to pgs. 49-58 **2 WEEKS FROM EXAM 1!!** ** Try to study 15 minutes every other day. Multiple choice exam. **HW #2 Due next Monday (Dark Adaptation)- dark adapt 1 eye and write about it (more specific directions in assignment) The Retina -

Receptors in the cell within the eyeball are behind all of the cells that are then going to takae infor to brain Light has to pass through gangly cells and other types of cells before it reaching rods and cones Light is coming in, has to pass through ganglie and then bipolar cells, rods and cones = where transduction happens, where electrical signals begin; send electrical signals back to gangli cells

The Retina magnified -

Epithelium provides nutrients for retina = top layer

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Vitreous humor would be at the bottom, filling the eyeball

The back of a person’s retina -

Rosy color, used to be believed it was pale yellow Dense packing of receptors in fovea

Rods and Cones -

There are two types of visual receptors on the retina They have different shapes and properties

How do rods detect light? -

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Each little disc within the rod contains rhodopsin which is made up of retinal and a protein called opsin At top of rod = disc which has protein called rhodopsin o Rhodopsin = pigment molecule o When a single light is absorbed by opsin, it changes shape, called isomerization o This process causes the light energy to be turned into electrical energy When retinal and rhodopsin are together, they are pink? (bright color), and when separated they are bleached

Bleaching of Rhodopsin -

The retinal image of rabbit looking out the window Parts were bleaching where one could distinguish window

Bleaching Retina Mini Experiment/Activity -

We were told to look at board, which had a blank white slide with center image of light bulb (black) and stared at it without moving eyes When slide was turned to a blank white slide, we could still see the light bulb Why did this happen? o Receptors are gonna try to transduce bright white slide (2nd slide) o First image showed, had image, and so image was “burned” into retina, and everything except light bulb was bleached. Retinal and opsin was separating. When staring at first image, parts of retina where white areas were, retinal and opsin were not there, but where bulb was, retinal and opsin are still there. On 2nd image, part that used to be black, can now transduce light, and white background since there was no rhodopsin, we have much more rhodopsin readily available where black parts used to be so brain interprets this as seeing light o For transduction to happen, retinal and opsin have to be together = rhodopsin

Rods and Cones -

What do you notice about the difference in distribution of the rods and cones across the retina? o Cones are mainly in the fovea o No rods, at all, in the fovea!! IMPORTANT TO KNOW

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No receptors in the blind spot (both rods and cones drop down to zero) Many more rods in the retina than there are cones

Rods vs Cones -

There are about 120 million rods in the retina and about 5 million cones Cones are responsive to bright light. They are responsible for color vision and our ability to see fine detail Rods are more numerous than cones are more sensitive to dim light. They are mainly used for night vision One type of cones absorbs short wavelength, one type absorbs medium wavelengths, and the final type absorbs long wavelengths

Dark Adaptation Procedure -

Fixation point in middle of screen, and light on to the side, and someone is adjusting brightness of light, across time, how are they going to adjust the brightness Would A or B be the direction the light would go? o A o When first going into dark, you need light to be bright, but as you are in the dark longer and longer, the dim the light. The more your threshold for light decreases over time

Dark Adaptation Curve -

What is this bump? o The rods are more sensitive here o Cones adapt faster o But rods continue adapting longer and longer o Just shine light on fovea to get dark adaptation for cones o Shine light on periphery to get rods and cones

TBC 09/06/19: The Retina Cont. -

The more rhodopsin you have, the dimmer light you’ll be able to see

The Purkinje Shift -

Shift in the brightness of colors Brightness and color are separate In daytime vision, the colors look a lot brighter, but as it changes to night vision, the brightness is dimmer What do you notice about the change in color? Why does this happen? What about the brightness? Why does this happen? o You go from having color vision to not having color vision because there is less light being reflected, hence switching to gray scale. Since there is no light, the cones are not activated, and you onl...