PSY 463 EXAM 1 REVIEW

Does vision occur in the retina or in the brain? | CH 2

Focusing an image clearly onto the retina is the initial step in the process of vision. ◦We do not see the image on the retina, vision occurs in the brain. The light on the retina must activate the visual receptors in the brain before the brain can create vision.

Describe distributed representation of multidimensional stimuli. What areas of the brain can be activated by different aspects of faces? | CH 4

Faces are multidimensional --> they cause many different reactions, and these reactions are associated with activity in many different places in the brain. Occipital Cortex = initial processing Fusiform Face Area = Basic face processing Amygdala = emotional reactions/familiarity Frontal Lobe = Evaluation of attractiveness Superior temporal sulcus = gaze direction, mouth movements, general face movements.

Vision is based on.. | CH 2

visible light

What is absolute threshold and difference threshold? | CH 1

◦Absolute --> the smallest stimulus level that can just be detected ◦Difference --> the smallest difference between two stimuli that enables us to tell the difference between them.

Explain the roles of rods and cones in the dark-adaptation curve. What is the rod-cone break? | CH 2

◦As soon as the light is extinguished, the sensitivity of both the cones and the rods begin increasing. ◦However, because cones are more sensitive than rods at the beginning of dark-adaptation, we see using our cones right after the lights are turned off. ◦Once the cones have reached max sensitivity (after 3-5 minutes in the dark), the rods are still adapting. ◦At about 7 minutes in the dark, the rods sensitivity has become more sensitive than the cones, and rod adaptation becomes visible. Rod-cone break --> the place where the rods begin to determine dark-adaptation.

Explain the optic nerve/blind spot | CH 2

◦Blind spot --> the place where the optic nerve leaves the eye. --> We don't see it because one eye covers the blind spot of the other, it is located at the edge of the visual field, there is an absence of receptors, and the brain fills in the spot with what is around it.

Briefly describe Neural Processing in the Perceptual Process | CH 1

◦Electrical signals travel through a vast interconnected network of neurons that (1) transmit signals from the receptors, through the retina, to the brain, and within the brain, and (2) change these signals as they are transmitted. ◦Electrical signals from each sense arrive at the primary receiving area for that sense in the brain. **Although signals have changed, they still represent the stimulus.

Describe the Perceptual Process. What is principle of transformation vs principle of representation? | CH 1

1. Environmental stimuli are all objects in the environment that are available to the observer (Distal/environment vs proximate/internal) Ex--> An image on the retina is a proximal stimulus. 2. Observer selectively attends to objects. Light is reflected and focused. 3. Stimulus impinges on receptors resulting in internal representation (Receptor Processes) 4. Neural Processing 5. Behavioral Responses (actions, navigating environment) ------------------ ◦Principle of Transformation (transduction) --> stimuli and responses created by stimuli are transformed, or changed, between the distal (environmental) stimulus and perception. ◦Principle of Representation --> everything a person perceives is based not on direct contact with stimuli but on representations of stimuli that are formed on the receptors and the resulting activity in the person's nervous system. (We see whatever is reflected on our rods and cones)

What is the electromagnetic spectrum? | CH 2

A continuum of electromagnetic energy that is produced by electric charges and is radiated as waves

What are the relationships in the Perceptual Process? How are they studied? | CH 1

A: Stimulus-Perception(Behavior) ◦ Grating Acuity --> discriminating fine details. The smallest width of lines that subjects can detect. ◦◦Asks the subjects to indicate the gratings orientation with thinner and thinner lines. ◦◦The smallest line-width at which the subject can still indicate the correct orientation is the grating acuity. ◦ Oblique Effect --> Vertical and horizontal lines create more neural firing than diagonal lines do. B: Stimulus-Physiological ◦Presented lines with different orientations to ferrets. ◦◦Saw that horizontal or vertical orientations caused larger brain/neurological responses than oblique orientations. C: Physiology-Perception(Behavior) ◦Furmanski and Engel 2000 ◦◦Made both behavioral and physiological measurements of subjects' response to oriented gratings. ◦◦Behav. measurements made by decreasing intensity difference between light and dark bars, and physiological measurements were made using fMRI.

Describe infant visual acuity. What is preferential looking technique? Why do infant's have poor acuity? | CH 2

At one month, acuity is typically between 20/400 and 30/600. ◦Infant sees at 20 ft what adults see from 400 ft. ◦Smaller outer segment contains less visual pigment, and does not absorb light as effectively as adults. Preferential looking technique --> two stimuli are presented, and the experimenter watches the infant's eyes to determine where the infant is looking ◦If the infant looks at one more than the other, the infant can tell the difference between them. ◦When a grating stimulus is presented with a gray field that reflects the same total amount of light, if the infant looks more at the grating stimulus on randomized trials then we see that the infant notices the difference and the grating. ◦The infants poor acuity can be traced to the fact that infants cones are spaced far apart (light gets lost in between) and that the visual area of the brain is poorly developed at birth. --> The rapid increase from 6-9 months after birth can be traced to the fact that more neurons and synapses are being added to the cortex, and the infant's cones are becoming more densely packed.

Explain the flexibility of receptive fields. What is contextual modulation? | CH 3

Because we live in an ever-changing environment, we need a perceptual system that is flexible and adapts to our needs. Kapadia et al. (2000): ◦Recorded from neurons in a monkey's visual cortex ◦When a bar was presented inside the neuron's receptive field, there is a small response. When two bars are flashed outside the receptive field, there is little to no response. But when two bars are presented outside the receptive field along with a bar inside the field, there is a large response. The response to stimulation within the receptive field can be affected by what is happening outside of it. --> This is called contextual modulation --> The large response that occurs may be related to perceptual organization. Whomelsdorf (2006): ◦Attention can also shift the location of a neuron's receptive field ◦When a monkey is looking at the fixation point but paying attention to locations (diamond or circle), the receptive field shifts when the monkey shifts attention from one location to the other.

How can experiences shape neural firing? What is the expertise hypothesis? | CH 4

Biological maturation is involved in the improvement in recognizing faces over time (Ex: there is evidence that some aspects of face recognition depend on the emergence of the fusiform face area) In addition, experience plays a role in perceptual development. ◦We grow up in an environment in which many features occur regularly (ex: oblique effect) The Expertise Hypothesis --> the fact that experience with the environment can shape the nervous system. Our proficiency in perceiving certain things can be explained by changes in the brain caused by long exposure, practice, or training. ◦Greeble Study: Initially, observers FFA responded well to faces but poorly to greebles. --> After training in greeble recognition, observers became greeble experts and were able to quickly identify greebles by their names. --> After training, observers FFA responded as well to greebles as it did to faces. Shows that the FFA responds to other complex objects as well.

What are end-stopped cells? Why are Hubel and Wiesel's discoveries important? | CH 3

Cells that fire to moving lines of a specific length or to moving corners or angles. Hubel and Wiesel's findings are important because it extended the idea that neurons respond selectively to oriented lines and stimuli with specific lengths. Helps determine how neurons respond to more complex objects.

Describe Behavioral Responses in the Perceptual Process | CH 1

Electrical signals are transformed into conscious experience. Involves action (Perception often leads to action). Perception is a continually changing process.

What are the problems with lateral inhibition as an explanation of the Chevreul Illusion and Hermann Grid? | CH 3

Chevreul Illusion: ◦When a chevreul staircase display is placed on a luminance ramp in both directions, the chevreul effect is decreased when the dark to light progression of the staircase is opposite to the luminance ramp, but enhanced if it is in the same direction as the ramp. ◦The background ramp should have no effect on lateral inhibition between one rectangle and the next. Hermann Grid: ◦When the Hermann Grid's usual straight lines are made curvy, the dark spots at the intersections vanish. ◦Making the lines curvy should have little or no effect on lateral inhibition

Describe the neural map on the striate cortex. What is cortical magnification? What is the cortical magnification factor? (Area V1) | CH 4

Determined by stimulating various places on the retina and noting where neurons fire in the cortex. ◦Retinotopic map: Locations on the cortex correspond to locations on the retina. --> Two points that are close together on an object and on the retina will activate neurons that are close together in the brain. --> Electrical signals associated with the part of the object near where a person is looking at are allotted more space on the cortex than signals associated with parts of the object that are located off to the side (More space for locations near the fovea than the peripheral retina). ◦Cortical magnification: Signals from the fovea account for 8-10% of the retinotopic map on the cortex. Cortical magnification factor --> the size of the magnification, determined using brain imaging.

What is distributed representation? What are two experiments that demonstrate distributed representation? | CH 4

Distributed representation occurs when a stimulus causes neural activity in a number of different areas of the brain. An fMRI experiment showed that the maximum activity for houses, faces, and chairs occurs in separate areas in the cortex. ◦However, all activity for each type of stimulus shows activity over a wide area of the cortex. Each type of stimulus causes activity in a number of areas. Huth et al. (2012) ◦Subjects viewed 2 hours of film clips while in a brain scanner. ◦Created a list of 1705 different objects and action categories to determine which categories were present in each film scene. ◦Showed that even though some stimuli activate specialized areas, the wide variety of stimuli we encounter cause activity that is distributed across a wide area of the cortex.

How do orientation-sensitive neurons respond to a scene? Explain tiling and how information about a scene is combined to create perception. | CH 4

Each circle on the tree trunk represents an area served by a location column. ◦The vertical tree trunk activates neurons in the 90 degree orientation columns in each location column. ◦The continuous tree trunk is represented by the firing of neurons sensitive to a specific orientation in a number of separate columns in the cortex. --> The cortical representation of a stimulus does not have to resemble the stimulus, it just has to contain information that represents the stimulus. At some point in the cortex, the information in the separate columns must be combined to create perception. ◦Tiling: each "circle" in a scene represents an area that sends information to one location column, and working together the columns cover the entire visual field. --> The visual field is served by adjacent and sometimes overlapping location columns.

Explain the what and how pathways in people without brain damage (length estimation, grasping task) | CH 4

Ganel et al. (2008) used an experiment designed to demonstrate a separation of perception and action in non-brain damaged subjects. ◦Line 1 is longer than line 2, but line 2 appears longer. ◦In length estimation task, they are asked to indicate how long the lines are with their fingers (ventral/what stream). ◦In the grasping task, they are asked to reach toward the lines and grasp each line by its ends (dorsal/where/how stream). --> Results indicate that participants judged line 1 as being shorter than line 2 in the length estimation task, but in the grasping task they separated their fingers apart more accurately to match its proper length. --> Supports the idea that perception and action are served by different mechanisms.

What is a receptive field? | CH 3

Hartline did research on the opened eyecup of a frog. He isolated a single fiber in the optic nerve, illuminated different areas of the retina, and found that the fiber he was recording from responded only when a small area of the retina was illuminated. Receptive Field --> the region of the retina that must receive illumination in order to obtain a response in any given fiber. Neuron's receptive field covers a much greater area than a single rod or cone receptor (meaning that the fiber is receiving converging signals from all of those receptors) ◦Receptive fields of many different nerve fibers overlap. ◦Football Analogy --> optic nerve fiber = spectator, retina = football field, receptive field = small areas viewed by each spectator.

Describe Lateral Inhibition in the Hermann Grid Illusion

Hermann Grid shows four black squares that appear to have gray spots in the white areas between them. Point A is where the dark spot appears. Inhibition sent by neurons B, C, D, and E each is 1/10th of the neurons initial response (to units of inhibition). ◦Point A receives 40 units of inhibition, so the final response of Point A to bipolar cell A is 60 and appears darker than the area surrounding it.

Explain the Mind-Body problem | CH 4

How do physical process like nerve impulses (body) become transformed into the richness of perceptual experience (mind). Ex --> Just showing that a neuron fires to a face or the color red doesn't answer the question of how the firing creates the experience of seeing a face or perceiving the color red.

Describe location and orientation columns in the cortex. What does Hubel and Wiesel's experiments show about this organization? | CH 4

Hubel & Wiesel carried out a series of experiments in which they recorded from neurons as they lowered electrodes into the cortex. ◦When the electrode is positioned perpendicular to the surface of the cat's cortex, they found that every neuron they encountered had its receptive field at about the same location on the retina. ◦Concluded that the striate cortex is organized into location columns that are perpendicular to the surface of the cortex. --> These neurons also all preferred stimuli with the same orientation. --> Also concluded that the cortex is organized into orientation columns, with each column containing cells that respond best to a particular orientation. Hubel and Wiesel also found that if an electrode is inserted obliquely (sideways) into the cortex, it crosses a sequence of orientation columns. ◦The preferred orientation of neurons in each column change in an orderly way as the electrode crosses the columns. ◦Moving the electrode 1 mm across the cortex passed orientation columns that represented the entire range of orientations.

Explain Hubel and Wiesel's rationale for studying receptive fields | CH 3

Hubel and Wiesel showed how neurons at higher levels of the visual system become tuned to respond best to more specific stimuli: ◦A neuron's receptive field is determined by presenting a stimulus, such as a spot of light, to different places on the retina. ◦Signals leaving the eye in the optic nerve travel to the lateral geniculate nucleus (LGN) to the occipital lobe of the cerebral cortex. --> The occipital lobe (Striate Cortex/V1) is the visual receiving area/ the place where signals from the retina and LGN first reach the cortex. --> Little change occurs in receptive fields when moving from optic nerve fibers to the LGN. LGN regulates neural information from the retina to the visual cortex. The information the LGN receives back from the brain may play a role in determining which information is sent up to the brain.

Weber's JND | CH 1

Just Noticeable Difference --> The minimum difference that must exist between two stimuli before we can tell the difference between them.

Explain Top Down vs Bottom up Processing. What does the rat man demonstration suggest? What is Charles Bonnet syndrome? | CH 1

Knowledge --> any information that the perceiver brings to a situation ◦Rat-Man demonstration example shows how recently acquired knowledge can influence perception. ◦Top Down (Knowledge-based Processing) --> Using stored information to interpret a current situation. ◦Bottom Up (date-based processing) --> processing based on the stimuli reaching the receptors. ◦Everything we do is a combination of top down and bottom up processing. ---- Some instances when bottom up is absent... ◦Charles Bonnet Syndrome --> Visual hallucinations that occur due to vision loss from any underlying cause.

What is lateral inhibition? Describe lateral Inhibition in the Limulus | CH 3

Lateral inhibition --> inhibition that is transmitted across the retina. The limulus eye is made up of hundreds of tiny structures called ommatidia. ◦It is possible to illuminate and record from a single receptor without illuminating neighboring receptors. ◦Hartline et al found that illuminating the nerve fiber of receptor A caused a large response. --> But when they illuminated three nearby receptors, the response of receptor A decreased. Illumination of neighboring receptors inhibited the firing caused by stimulation of receptor A, caused by lateral inhibition transmitted from B to A across the Limulus's eye by the fibers of the lateral plexus.

Explain phototransduction in receptors (Opsin, Retinal, Visual Pigments, Isomerization, Bleaching) | CH 2

Light entering visual receptors triggers electrical signals when the light is absorbed by light-sensitive visual pigment molecules in the receptors. ◦Visual transduction transforms light into electricity, and occurs in the rod and cone receptors. Receptors have outer segments that contain visual pigment molecules. Visual pigment molecules have two components: ◦Opsin, a large protein ◦Retinal, a light sensitive molecule When opsin and retinal are combined, the resulting molecule absorbs visible light. Visual transduction occurs when the retinal absorbs a photon. ◦The retinal changes shape (isomerization) from being bent to straight, creating a chemical chain reaction that activates thousands of charged molecules to create electrical signals in receptors. When the retinal separates, it cause the molecule to become lighter in color (visual pigment bleaching).

Describe light in relation to the electromagnetic spectrum.. | CH 2

Light is a part of the electromagnetic spectrum. ◦Energy is described by wavelength (the distance between the peaks of the electromagnetic waves) ◦The spectrum ranges from short wavelength gamma rays to long wavelength radio waves. ◦The visible spectrum for humans ranges from 400 to 700 nanometers. --> For humans and some other animals, the wavelength of visible light is associated with the different colors of the spectrum.

Describe the process of the cornea and lens in focusing light onto the receptors. What is accommodation? Describe normal vision. | CH 2

Light reflected from an object into the eye is focused onto the retina by a two element optical system: the cornea and the lens. ◦The cornea (fixed) accounts for about 80% of focusing, the lens (adjusts shape for object distance) accounts for 20% of focusing. ◦Accommodation --> the change in the len's shape that occurs when the ciliary muscles at the front of the eye tighten and increase the curvature of the lens so that it gets thicker. --> Light rays pass through the lens more sharply and focus near objects on the retina. ◦In normal vision, the eye is relaxed when the object is far and the image falls on the back of the retina. When the object is near, a relaxed eye would reflect the image beyond the retina and cause it to look blurry. --> However, in normal vision, the eye accommodates for the near object and thickens the lens so that the focus point falls on the retina and appears clears.

Explain the techniques for measuring neural activity. What is the Subtraction Technique? | CH 4

MRI: creates images of structures within the brain, a standard technique for detecting tumors and brain abnormalities. Doesn't indicate neural activity. fMRI: takes advantage of the fact that blood flow increases in areas of the brain that are activated. ◦Hemoglobin (carries oxygen in the blood) contains an iron molecule and has magnetic properties. ◦Active brain areas use more oxygen, and hemoglobin molecules lose some of their oxygen and become more magnetic. fMRI detects changes in the magnetic response of hemoglobin. PET scan:

Describe streams for information about what and how in people with brain damage. Explain the case of Patient D.F. | CH 4

Milner & Goodale (1995) suggest that the dorsal (where) stream does more than indicate where an object is. ◦The dorsal stream provides information about how to direct action with regard to a stimulus. Used the method of determining double dissociations to study D.F., a woman who suffered damage to her ventral (what) pathway. ◦She was unable to match the orientation of a card held in her hand to different orientations of a slot. ◦But when asked to put the card through the slot, she could do it. --> Indicates that there is one mechanism for judging orientation and another for coordinating vision and action. A better description for the dorsal pathway may be the "how" or "action" pathway, because it determines how a person carries out an action.

What is modularity? | CH 4

Modularity --> The idea that specific areas of the cortex are specialized to respond to specific types of stimuli. Areas that are specialized to specific types of stimuli are called modules.

What are neural circuits? Describe neural convergence | CH 2

Neural circuits: interconnected groups of neurons Signals generated in the receptors (rods and cones) travel vertically through: ◦bipolar cells ◦ganglion cells ◦ganglion axons Signals are sent horizontally: ◦Between receptors by horizontal cells ◦Between bipolar and between ganglion cells by amacrine cells. Convergence --> occurs when a number of neurons synapse onto a single neuron. ◦There is higher convergence of rods than cones --> Average of 120 rods to one ganglion cell --> Average of six cones to one ganglion cell. --> Cones in the fovea have one to one relation to ganglion cells.

Describe chemical properties (ions) of action potentials. Explain neural communication, and excitatory vs inhibitory neurotransmitters | CH 2

Neurons are surrounded by a solution containing ions Ions carry an electrical charge: ◦Sodium (Na+) ◦Chlorine (Cl-) inhibitory ◦Potassium (K+) Electrical signals are generated when ions cross the membranes of neurons. Membranes have selective permeability. Neural Communication: 1. Resting potential (-70 mV) 2. Synaptic Activity causes Na+ to flow into cell 3. Action Potential at +40 mV 4. Ca++ flows in and binds to vesicles in the membranes to release NTs ◦If NT is excitatory (depolarization), Na+ will flow into the new cell, depolarizing the neuron (Excitatory Postsynaptic Potential EPSP) ◦If NT is inhibitory (hyperpolarization), Cl- will flow into new cell, hyperpolarizing the neuron (Inhibitory Postsynaptic Potential IPSP)

Explain double dissociations in neuropsychology | CH 4

Neuropsychology --> the study of the behavioral effects of brain damage in humans. In one person, damage to one area of the brain causes function A to be absent while B is present. In another person, damage to another area of the brain causes function B to absent while A is present. ◦The fact that the two tasks can be disrupted separately and in opposite ways means that the two functions operate independently of one another.

How did Dougherty et al. (2003) use brain imaging to demonstrate cortical magnification in the human visual cortex? | CH 4

Observer looks directly at the center of the screen, so a dot at the center falls on the fovea. ◦Stimulus light presented in two places: near the center which illuminated a small area near the fovea, and farther from the center which illuminated an area in the peripheral retina. ◦Stimulation of the small area near the fovea activated a greater area on the cortex than the stimulation of the larger area in the periphery. Although the space on the cortex for places we are looking at are large, it does not mean that we perceive that thing as being larger. We see the details of the image better, more space on the cortex translates to better detail vision rather than larger size.

Explain the process needed for transduction. How does this relate to/demonstrate the dark adaptation curve? Describe Rushton's findings on darkening of the human retina. | CH 2

Process: ◦Retinal changes shape ◦Opsin molecule separates ◦Retina shows pigment bleaching ◦Retinal and opsin must recombine to respond to light ◦Visual Pigment regenerates Regeneration: ◦When pigments are in the lighter bleached state, they are no longer useful for vision and must be regenerated (retinal returns to bent shape and reattaches to opsin) ◦When we are in the dark, there is no isomerization/bleached pigments (because no/less light is being absorbed) so sensitivity to light in the dark increases. Rushton observed darkening of the human retina during dark adaptation, and found that it matched the curve. ◦Cone pigment takes 6 minutes to regenerate completely, rod pigment takes more than 30 minutes ◦Our sensitivity to light depends on the concentration of visual pigment ◦The speed at which our sensitivity increases in the dark depends on the regeneration of the visual pigment.

Describe the "What" and "Where" pathways in relation to the LGN | CH 4

Properties of the ventral (what) and dorsal (where) streams are established by two different types of ganglion cells in the retina, which transmit signals to different layers of the LGN. ◦The pathways are not totally separated and have connections between them ◦Signals not only flow up the pathway toward the parietal and temporal lobes but also back down as well.

Describe how perception can meet memory (Halle Berry/Steve Carell neurons, Homer Simpson neurons) | CH 4

Quiroga recorded from eight patients with epilepsy who had electrodes implanted in their hippocampus or medial temporal love to help localize where their seizures originated. ◦Patients saw a number of different views/stimuli and a number of neurons responded to some of those stimuli. ◦However, some neurons responded to a number of different views of just one person or building, or to a number of ways of representing that person or building. --> A neuron responded to pictures of Steve Carell, another neuron responded to photos, drawings, and the words "halle berry." --> The neurons are not responding to visual features of the pictures, but to concepts that the stimuli represent. However, just because a hippocampus neuron responds to a visual stimulus doesn't mean it is responsible for seeing. It is responsible for remembering. Homer Simpson Neurons: ◦Had epilepsy patients view a series of 5-10 second video clips a number of time while recording neurons in the MTL. ◦A neuron in one of the patients responded best to a clip from The Simpsons. --> Asked patients to think back to any of the clips they had seen. Found that the neuron responded weakly when remembering other clips, but caused a large response when they remembered the simpson's clip.

What is important to always remember about receptive fields? | CH 3

Receptive fields are always on the receptor surface because that is where the stimuli are received.

Describe receptive fields in terms of Hubel and Wiesel (center-surround, antagonism) | CH 3

Recorded from optic nerve fibers in the cat and discovered that the cat's receptive fields are arranged in a center-surround organization. ◦The area in the center responds differently to light than the area in the surround. ◦Output of the receptive fields change depending on the area that is stimulated Center-surround antagonism --> comes into play when a spot of light becomes large enough that it begins to cover both the excitatory area and some of the inhibitory area. ◦Stimulation of the inhibitory surround counteracts the center's excitatory response, causing a decrease in the neuron's firing rate. --> Therefore, the neuron responds best to a spot of light that is the size of the excitatory center of the receptive field. Only the excitatory area is stimulated = highest response Only the inhibitory area is stimulated = lowest response Both areas stimulated = intermediate response

Describe higher level neurons. Explain Gross (1972) inferotemporal cortex experiments in monkeys. What is the fusiform face area? | CH 3

Removing parts of the inferotemporal (IT) cortex in monkeys affects the ability of them to tell the difference between objects. ◦Presented lines, squares, and circles to the monkeys, some stimuli were light and some dark. ◦Found a neuron that would not respond to standard stimuli like oriented lines or circles or squares, but suddenly responded when a researcher stuck out their hand. ◦It was determined that the neuron responded to a handlike shape with fingers pointing up. Neural processing that occurred beyond the initial receiving areas studied by Hubel and Wiesel had created neurons that responded best to very specific types of stimuli. ◦Researchers also discovered an area on the temporal lobe called the fusiform face area (responds strongly to faces)

Describe rod sensitivity vs cone sensitivity | CH 2

Rods are more sensitive to light than cones ◦In a dark adapted-eye, rod vision is more sensitive than cone vision ◦Rods take less light to respond because of the rod's greater convergence to the ganglion cell. ◦Rods have greater convergence, which results in summation of the inputs of many rods into ganglion cells, increasing the likelihood of response. ◦Rods cannot distinguish detail All cone foveal vision results in high visual acuity ◦One to one wiring leads to ability to discriminate details ◦Firing of two separate ganglion cells apart from one another indicates that there are two spots of light as opposed to one. ◦Cones need more light to respond than rods.

Explain face neurons in the monkey's IT cortex and the fusiform face area in humans. What are areas for places and bodies in humans? | CH 4

Rolls & Tovee (1995) found many neurons that respond best to faces in monkeys. ◦There are areas in the monkey temporal lobe that are rich in these neurons. ◦Presented different images of faces, bodies, fruits, gadgets, and patterns, and classified neurons as face selective if they responded at least twice as strongly to faces as to nonfaces. --> found that 97% of the cells were face selective. Kanwisher et al. (1997) used fMRI to determine brain activity in response to pictures of faces and other objects. ◦Subtracted the response to other objects from the response to faces, and found that activity remained in an area called the fusiform face area. (Roughly equivalent to the face area in the monkey) --> Prosopagnosia: difficulty recognizing the faces of familiar people. Parahippocampal place are (PPA) --> activated by pictures depicting indoor and outdoor scenes. ◦Increased activation occurs both to empty rooms and to rooms that are completely furnished. Extrastriate body area (EBA) --> activated by pictures of bodies and parts of bodies (but not by faces)

Use the neural circuit to explain center-surround receptive fields | CH 3

See page 57-58 in the textbook. Center-surround receptive fields are created by the interplay between excitation and inhibition

Describe how selective rearing is evidence for feature detectors being involved in perception. How was it demonstrated in Blakemore & Cooper's kitten study? | CH 3

Selective rearing --> the idea behind it is that if an animal is reared in an environment that contains only certain types of stimuli, then neurons that respond to these stimuli will become more prevalent. Experience-dependent plasticity: the idea that the response properties of neurons can be shaped by perceptual experience. --> Rearing an animal in an environment that only contains vertical lines should result in the animal's visual system having neurons that respond predominantly to verticals. Blakemore & Cooper (1970) ◦Reared kittens in striped tubes so that each kitten is exposed to only one orientation, either vertical or horizontal ◦After 5 months, the kittens seemed blind to orientations that they had not seen in the tube. If raised in a vertical environment, the horizontally responding neurons were lost because they were not used.

Distinction between sensation and perception? | CH 1

Sensation involves detecting elementary properties of stimuli and perception involves the higher brain functions involved in interpreting events and objects.

What is sensory coding? Specificity coding? Population coding? Sparse coding? | CH 3

Sensory code refers to how neurons represent various characteristics of the environment. Specificity coding: the idea that an object could be represented by the firing of a specialized neuron that responds only to that object. Population coding: the representation of a particular object by the pattern of firing of a large number of neurons. ◦A large number of stimuli can be represented Sparse coding: occurs when a particular object is represented by a pattern of firing of only a small group of neurons, with the majority of neurons remaining silent. Features or objects are represented by the pattern of firing of groups of neurons. Sometimes the groups are small (sparse coding), sometimes large (population coding)

Describe lateral inhibition in the Chevreul Illusion | CH 3

Simultaneous contrast: seeing areas of different brightness due to adjacent areas. Chevreul Illusion shows four gray rectangles placed side by side, ranging from light to dark. ◦The light intensity in each rectangle is the same across one edge to the other ◦BUT the perceived lightness is different: The border the edges show one edge (B) as being lighter and the other edge (C) being darker. These differences are not present in the actual physical stimuli. --- Each of the six receptors (X,A,B | C,D,Y)in the circuit sends signals to bipolar cells, which sends lateral inhibition to their neighbors on both sides. ◦Initially, receptors in the lighter rectangle have a response of 100, while receptors on the dark side have response of 20. ◦The amount of inhibition is equal to 1/10th of the cell's initial response. ◦Therefore, Receptor X and A diminish to 80, D and Y diminish to 16, and B and C create the light and dark bands at the edge (B = 88) (C = 8)

Describe "one location column = many orientation columns." What does this mean for perception? What is a hypercolumn? | CH 4

The 1 mm dimension for location columns mean that one location column is large enough to contain orientation columns that cover all possible orientations. ◦Because a location column contains some neurons that respond to each orientation, any oriented object that falls within the location column's area on the retina will cause some of the neurons in this location column to fire. --> Hypercolumn: a location column with all of its orientation columns. Receives information about all possible orientations that fall within a small area of the retina.

Describe Spectral Sensitivity. How is it measured? What is the Purkinje Shift? | CH 2

The eye's sensitivity to light as a function of the light's wavelength Rod spectral sensitivity: ◦More sensitive to short-wavelength light ◦Most sensitivity at 500 nm ◦Measured after the eye is dark adapted, by presenting test flashes in the peripheral retina off to the side of the fixation point. Cone Spectral Sensitivity ◦Most sensitive at 560 nm ◦Measured by having a subject look directly at a test light so that it stimulates only the cones in fovea. Purkinje Shift --> enhanced sensitivity to short wavelengths (blue-green end of spectrum) during dark adaptation when the shift from cone to rod vision occurs. Absorption Spectrum --> a plot of the amount of light absorbed versus the wavelength of the light.

What are lesion and ablation experiments? | CH 4

The goal of lesion experiments is to determine the function of a particular area of the brain. ◦Ablation refers to the destruction or removal of tissue in the nervous system. Lesion procedure: ◦Animal is trained to indicate perceptual capacities. ◦Specific part of the brain is removed or destroyed. ◦Animal is retrained to determine which perceptual abilities remain.

What is dark-adaptation? How is it measured? What is dark-adapted sensitivity? | CH 2

The process of increasing sensitivity in the dark. Measured by determining a dark adaptation curve --> shows that as adaptation proceeds, the subject becomes more sensitive to light. ◦The red dark adaptation curve increases rapidly for the first 3-4 minutes after the light is extinguished and then levels off. At 7-10 minutes, it begins increasing again and continues until you've been in the dark for about 20-30 minutes. The sensitivity at the end (dark-adapted sensitivity) is roughly 100,000 times greater than light-adapted sensitivity that was measured before the adaptation began.

Describe receptive fields of neurons in the visual cortex (feature detectors). What are simple cortical cells and how do they work? What are complex cells? | CH 3

The striate cortex (V1) is where signals first arrive in the cortex. By flashing spots of light on different places in the retina, Hubel and Wiesel found cells in the striate cortex with receptive fields that have excitatory and inhibitory areas. ◦But the areas are arranged side by side, and cells with side by side receptive fields are called simple cortical cells. --> A cell with this layout responds best to vertical bars, and as the bar is tilted so that the inhibitory area is also illuminated, firing of the cell decreases. The relationship between orientation and firing is indicated by a neuron's orientation tuning curve. ◦There are other simple cells that respond to other orientations Complex Cells: Hubel and Wiesel also found that many cortical neurons respond best to moving barlike stimuli with specific orientations. ◦Many complex cells respond best to a particular direction of movement. ◦Since these neurons don't respond to stationary flashes of light, their receptive fields are indicated by outlining the area that elicits a response when stimulated.

Describe stream pathways about information for what and where. What is the object discrimination problem vs the landmark discrimination problem? | CH 4

Ungerleider & Mishkin (1982) used lesioning to better understand functional organization of the brain. ◦Presented monkeys with two tasks: (1) an object discrimination problem and (2) a landmark discrimination problem. Object discrimination problem: ◦Monkey was shown one object and was then presented with a two choice task. ◦If the monkey pushed aside the target/initial object, it received a food reward hidden in a well underneath the object. Landmark discrimination problem: ◦The monkey is supposed to remove the cover of the food well that is closest to the tall cylinder. Part of the monkey's temporal lobe was removed, and behavioral testing after ablation showed that the object discrimination problem became very difficult. ◦Indicates that the pathway that reaches the temporal lobes is responsible for determining an objects identity. --> The "What" Pathway (pathway leading from the striate cortex to the temporal lobe). Monkeys who had their parietal lobes removed had difficulty with the landmark problem, indicating that the pathway that leads to the parietal lobe is responsible for determining object location. The "Where" Pathway

Describe selective adaptation | CH 3

When we view a stimulus with a specific property, neurons tuned to that property fire. ◦The firing causes neurons to become fatigue (adapt) ◦Adaptation causes the neurons firing rate to decrease and the neuron fires less when the stimulus is immediately presented again Adaptation is selective because only the neurons that were responding to verticals or near-verticals adapt, and neurons that were not firing do not adapt. --> Adaptation is a short term effect.

Why is transduction by the visual pigments crucial for perception? How do visual pigments shape perception? | CH 1

Without it information about the representation of a stimulus formed on the retina would not reach the brain and perception would not occur. ◦Visual pigments shape perception because (1) the ability to see light depends on having a high concentration of light-sensitive pigment in the receptors and (2) there are different types of pigments which respond best to light in different parts of the visible spectrum.

Measuring Perception/Classical Psychophysical Methods (Fechner) | CH 1

◦Fechner proposed a number of methods for measuring the relation between mental and physical (Psychophysics). ◦Method of Limits --> Experimenter presents stimuli in either ascending or descending order. ◦◦Observer responds to whether they perceived the stimulus. The averaged cross over point is the threshold. ◦Method of Adjustment --> Stimuli of different intensities presented in ascending and descending order. ◦◦Observer responds and controls the change in stimulus intensity. ◦◦Averaged crossover points is threshold. ◦Method of Constant Stimuli --> Stimuli of different intensities presented in random order ◦◦Observer responds across many trials ◦◦Detection at 50% of trials is the threshold. ◦ Large number of trials increases statistical power/makes it more accurate.

Explain macular degeneration vs retinitis pigmentosa (destruction of the retina) | CH 2

◦Macular degeneration --> Fovea and small surrounding area are destroyed. --> Creates a "blind spot" on retina --> Most common in older individuals. But environmental factors do play a role. ◦Retinitis Pigmentosa --> Genetic disease (passed from one generation to the next) --> Rods (peripheral retina) are destroyed first. You can see in the center, but peripheral is blurred/blind. --> Foveal cones can also be attacked in severe cases, resulting in complete blindness

Explain psychophysical measurement of the effect of selective adaptation to orientation | CH 3

◦Measure a person's contrast threshold with a number of different orientations --> Contrast threshold is the minimum intensity difference between two adjacent bars that can be detected ◦Adapt the person to one orientation by having them view a high contrast adapting stimulus for a minute or two ◦If the high contrast grating decreases the functioning of neurons that determine the perception of verticals, this should cause an increase in contrast threshold so it is more difficult to see low contrast vertical gratings. Orientation detectors play a role in perception. When we look at a complex scene, feature detectors that are firing to the orientations in the scene are helping construct perception of the scene.

Dr. P (The Man Who Mistook His Wife for a Hat), Perception vs Recognition | CH 1

◦Perception --> conscious awareness of the stimuli ◦Recognition --> placing the stimuli in a category giving it meaning ◦Patient had difficulty remembering some things and was diagnosed with visual form agnosia. ◦He would talk to objects and wait for them to talk back. ◦When shown a glove, he was able to identify the components of the glove but could not tell what the object was. Perception was intact but recognition was not.

Explain Perception. Include the historical and modern view. | CH 1

◦Perception→ Conscious experience that results from stimulation of the senses. ◦Our whole experience of the world is dependent on sensory receptors, and perception is the conscious element of that stimulation. ◦Historic: Perception is simple, perceiving machines easy. ◦Modern: Perception is super complex

Describe Visual Impairments (Presbyopia, Hyperopia, Myopia, and Astigmatism) | CH 2

◦Presbyopia (Old Eye) --> Age related far sightedness due to the hardening of the lens and weakening of ciliary muscles --> Distance of near point increases --> Corrective lenses are needed for close activities such as reading ◦Hyperopia --> Farsightedness not age related --> Inability to see nearby objects clearly, the focus point is behind the retina/image is projected beyond the eye and appears blurry. --> Usually caused by an eyeball that is too short, and constant accommodation for nearby objects can lead to eyestrain and headaches. ◦Myopia --> Nearsightedness, image is focused in front of retina/inability to see distant objects. --> Occurs when the optical system brings parallel rays of light into focus at a point in front of the retina, so the image that reaches the retina is blurred. --> Caused by refractive myopia (cornea or lens bends too much light) or axial myopia (eyeball too long) ◦Astigmatism --> Image lands in multiple places on the retina --> Blurry vision near and at a distance, due to mismatch in curvature of cornea and lens. The image is not focused as one point, causing it to appear blurry or doubled.

Briefly list and describe the anatomy of the eye | CH 2

◦Pupil --> the opening at the front that allows light in ◦Cornea --> hard outer shell that does most of the focusing ◦Lens --> Stretch and contract to change thickness of the lens ◦Retina --> Sharp images are formed on the retina. The retina is the network of neurons that covers the back of the eye and contains the receptors for vision. ◦Fovea --> When we look directly at an object, the object's image falls on the fovea. ◦Receptor cells (rods, cones, visual pigments in outer segments) ◦Pigment Epithelium ◦Optic Nerve --> contains a million optic nerve fibers that conduct signals toward the brain.

What are the differences between rods and cones? | CH 2

◦Rods are large and cylindrical. Rods can be found in the peripheral retina (all of the retina outside of the fovea) along with cones. ◦Cones are small and tapered, and can be found in both the fovea and the peripheral retina.

Briefly describe Receptor Processes in the Perceptual Process. What are sensory receptors? What is transduction? | CH 1

◦Sensory Receptors --> cells specialized to respond to environmental energy, with each sensory system's receptors specialized to respond to a specific type of energy. ◦Rod and cone receptors line the back of the eye and (1) change light energy into electrical energy and (2) shape perception by the way they respond to different properties of stimuli. ◦Visual Receptors transform light energy because they contain a light-sensitive chemical called visual pigment (which reacts to light) ◦Transduction --> changes environmental energy to another form of energy (electrical energy)

Describe the basic properties of action potentials | CH 2

◦Show propagated response. Once the response is triggered, it travels all the way down the axon without decreasing in size. -->Enables neurons to transmit signals over long distances. ◦Increasing stimulus intensity can increase the rate of firing. ◦Have a refractory period of 1ms -- upper firing rate is 500 to 800 impulses per second ◦Show spontaneous activity that occurs without stimulation

What is Mind-Body Dualism? What did Fechner propose about this view? | CH 1

◦The body and mind are completely separate things. The body is physical and can be studied, but the mind is not and is impossible to study. ◦Fechner proposed that the mind and body should not be thought of as totally separate but as two sides of a single reality. The mind could be studied by measuring the relationship between changes in a physical stimulation and a person's experience.

Measuring sensory experience above threshold (Thresholds arent everything). Explain magnitude estimation, recognition testing, reaction time, and phenomenological report. | CH 1

◦Thresholds arent absolute (dark Tunnel example) ◦Magnitude Estimation --> "Standard" is first presented and assigned a value. Observer sees the same stimulus at different intensities and assigns it a value based on the standard. ◦Recognition Testing --> Ask brain damaged patients to name objects. Recognition also used to assess the perceptual abilities of people without brain damage. ◦Reaction Time --> Ask subjects to keep their eye fixed on a target and push a button whenever a dark target flashes anywhere on the display. ◦Phenomenological Report --> Describing what is out there. They define the perceptual phenomena we want to explain...