perceptual processes exam 1

csu class with professor grace blatt, first exam

Bottom-up Vs. top-down processing

1.) The involuntary, unavoidable capture of attention by a salient perceptual stimulus, often driven by sudden changes in the environment, like a loud sound or abrupt movement​

2.) Deliberately paying attention to something in order to get information needed to achieve goals. This is a form of voluntary attentional control.

Brain Structures: What is the corpus callosum and its function

A large bundle of axons that constitutes the major connection between the two cerebral hemispheres.

function: It allows information to be shared and coordinated across both sides of the brain.

Brain Structurs: What is the thalamus and its function

The most important subcortical structure involved in perception; most neural signals originating in the sensory organs pass through the thalamus on their paths to the cortex.

It acts as a central hub for sensory information, relaying it from the sensory organs (such as the eyes, ears, and skin) to the appropriate areas of the brain for processing

Characteristics of rods and cones

1.) photoreceptors in the retina, highly sensitive to low light levels. They are specialized for night vision and have poor acuity (sharpness of vision). Rods do not detect color

2.) Photoreceptors that are responsible for high-acuity color vision. They function best in bright light and come in three types, each sensitive to different wavelengths of light (short, medium, and long) for color perception​

Characteristics of strong lenses Vs. characteristics of weak lenses

1.) These lenses are thicker and more rounded. They have a shorter focal length, meaning they refract (bend) light sharply, allowing them to focus light from nearer objects. This high refractive power makes them more suitable for close-up focusing tasks.

2.) These lenses are thinner and flatter. They have a longer focal length, meaning they refract light less sharply, which makes them ideal for focusing light from distant objects. Weak lenses are less powerful in terms of bending light​

Convergence

Many light-sensitive cells in your eye send their signals to one output cell. This helps you see in dim light but makes images less clear because signals are combined.

Dilation or change in pupil due to amount of light present

pupillary reflex

the automatic process by which the iris contracts or relaxes to control the size of the pupil in response to the amount of light entering the eye. In bright light, the iris contracts, causing the pupil to get smaller (constriction), while in dim light, the iris relaxes, causing the pupil to get larger (dilation)

Distal Vs. Proximal Stimuli

1.) A perceived object or event in the world.

2.) A physical energies evoked by a distal stimulus that impinges on the specialized cells of a sense.

Fechner’s Law

A statement of how the perceived intensity of a stimulus changes as its physical intensity changes.

Layers of cells in the retina 

Photoreceptor - Outer nuclear layer: Contains the photoreceptors (rods and cones).

Inner nuclear layer: Contains the bipolar cells, horizontal cells, and amacrine cells.

Ganglion cell layer: Contains the retinal ganglion cells (RGCs), which send visual information to the brain

Method of adjustment

A behavioral method used in psychophysical experiments; when used to measure the absolute threshold

• the participant adjusts the intensity of a stimulus (like a light or sound) themselves until they can just barely detect it (for absolute thresholds) or perceive a difference in intensity (for difference thresholds)

Method of constant stimuli & how to determine JND

 A behavioral method used in psychophysical experiments; when used to measure the absolute threshold, the participant is repeatedly presented with a fixed set of stimuli, in random order, covering a range of intensities, and the participant must indicate whether or not each stimulus was detected.

How to determine JND: the lowest intensity stimulus level that can be perceived 50% of the time.

On-center RGCs Vs. off-center RGCs

1.) If RCG is ________ increase their firing rate when the amount of light striking the center of the receptive field increases relative to the light striking the surrounding area. (excited by bright light)

2.) If RGC is ______ increase their firing rate when the amount of light striking the center of the receptive field decreases relative to the light striking the surrounding area (excited by dark)

Parts of a neuron and their function 

Neurons: Cells of the nervous system that produce and transmit information-carrying signals.

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Cell body: The part of a cell that contains the nucleus.

Dendrites: Projections that emanate from the cell body of a neuron and that receive signals from other neurons.

Axon: A projection that emanates from the cell body of a neuron and that conducts neural signals to the axon terminals, for transmission to other neurons.

axon terminals: Endings of an axon, where neural signals are transmitted to other neurons.

Parts of the eye: Blind Spot/Optic disk

Location on the retina where the axons of RGCs exit the eye; contains no photoreceptors. (no light detecting cells)

Parts of the eye: Fovea

A region in the center of the retina where the light from objects at the center of our gaze strikes the retina; contains no rods and a very high density of cones.

Parts of the eye: retina

The inner membrane of the eye, made up of neurons, including the photoreceptors that convert the light entering the eye into neural signals.

Prevalence of rods and cones in fovea and peripheral retina

1.) there are no rod cells, but there are a lot of cone cells, which help you see sharp details and colors, especially in bright light.

2.) In the peripheral retina (the outer parts of your vision), there are many more rod cells, which help you see in dim light, but they don’t show details or colors as well.

Process of Action Potential

resting potential, depolarization, repolarization, hyperpolerization

Sensation Vs. perception

1.) The initial steps in the perceptual process, whereby physical features of the environment are converted into electrochemical signals that are sent to the brain for processing.

2.) The later steps in the perceptual process, whereby the initial sensory signals are used to represent objects and events so they can be identified, stored in memory, and used in thought and action.

Staircase method

A behavioral method used in psychophysical experiments; when used to measure the absolute threshold, the participant is presented with a stimulus and indicates whether it was detected, and based on that response, the next stimulus is either one step up or one step down in intensity.

How to determine JND: whenever the participant's response changes from a yes (they can sense it) or no (they cannot sense it) you take the number of those reversal responses and find the average. 

Steven’s Power Law 

 A statement of the relationship between the physical intensity of a stimulus and its perceived intensity

Transduction

The transformation of a physical stimulus (touching it physically) into neural signals (feeling it).

Two ways to measure light and what they produce

Wavelength: measurement gives information about the color of light, which is critical for understanding how we perceive different colors. It tells us the type of electromagnetic radiation based on how long or short the light waves are.

Photons: measurement relates to the quantity of light. Counting photons provides insight into how intense or bright the light is, which affects how much light is available to detect or interact with objects, surfaces, or biological systems.

Types of receptive fields (parasol and midget)

1.) larger receptive fields. They send signals to the magnocellular layers of the (LGN). These cells are more sensitive to motion and low light conditions.

2.) smaller receptive fields. They send signals to the parvocellular layers of the LGN and are more involved in processing color and fine detail

Visual acuity and adapting to dim light

1.) This is how well you can see fine details. It’s best where you’re looking directly because of the high number of cone cells in that area. Cones help with clear vision in bright light, while rods are better for seeing in low light but don’t provide as much detail.

2.)  This is when your eyes adjust to low light conditions, like when you enter a dark room. Rods, which help you see in the dark, take about 25 minutes to fully adjust and become more sensitive. Cones adjust faster but aren’t as good in dim light.

Weber’s Law

A statement of the relationship between the intensity (like size) of a standard stimulus and the size of the just noticeable difference 

Hyperopia

being farsighted

a condition in which the optic axis of the eye is too short, and accommodation (the eye's ability to adjust its lens) cannot make the lens thick enough to focus light from nearby objects on the retina.

Myopia

being nearsighted

a condition where the optic axis is too long. In this case, accommodation cannot make the lens thin enough to focus light from distant objects on the retina.

Macular Degeneration

(blurred center) - Damage to the central part of the retina, leading to vision loss, particularly in older adults

ec - Dry Macular Degeneration: The more common type, caused by the thinning of the macula and the accumulation of tiny clumps of protein called drusen.

Wet Macular Degeneration: Less common but more severe, caused by abnormal blood vessels growing under the retina, which can leak fluid or blood, leading to rapid vision loss

Retinitis Pigmentosa (tunnel vision)

A genetic disorder that slowly damages the retina, starting with night blindness and narrowing the field of vision

Optic nerve Vs. optic tract (At what point does it change its name?)

Nerve formed by the bundling together of the axons of retinal ganglion cells (RGCs); it exits the eye through the optic disk.

 After ______ ______ reaches a crossing point in the brain called the optic chasm, it continues as the ______ ______ and fibers regroup and send information to different sides of the brain

Optic chiasm

a critical point in the visual system where the optic nerves from both eyes partially cross

Process and pathways of cells from left and right visual fields traveling from each eyes to the LGN and V1

• Light enters from each visual field (left visual field to the right side of both retinas, right visual field to the left side).

• Optic nerves carry signals from each eye to the optic chiasm.

• At the optic chiasm, nasal fibers cross to the opposite side, while temporal fibers stay on the same side.

• Signals continue through the optic tracts to the LGN in the thalamus.

• From the LGN, signals are sent to the primary visual cortex (V1) for processing.

Contralateral Vs. Ipsilateral

1.) Opposite-side organization, in which stimulation of neurons on one side of the body or sensory organ is represented by the activity of neurons in the opposite side of the brain​

ex - if you see something in your left visual field, it is processed in the right hemisphere of your brain.

2.) Same-side organization, where the signals from one side of the body are processed on the same side of the brain.

ex - the right ear sends some signals to the right side of the brain without crossing over.

LGN organization

Magnocellular layers (1 and 2) handle movement and dynamic visual information.

Parvocellular layers (3 to 6) handle color, texture, and form.

Koniocellular layers are interspersed between the other layers, handling additional color information.

This layered structure allows the brain to process different aspects of vision (like motion and color) separately.

Characteristics of magnocellular layer

layers of the LGN containing neurons with large cell bodies.

Characteristics of parvocellular layer

 layers of the LGN containing neurons with smaller cell bodies.

Characteristics of koniocellular layer

are thinner layers within the LGN, containing even smaller cell bodies.

contralateral layers

Layers 1, 4, and 6 of the LGN

Ipsilateral layers

 Layers 2, 3, and 5 of the LGN

Percentage of RGCs that connect to the LGN

90%

Characteristics of simple and complex cells in V1

______ ______ respond to bars or edges of specific orientations in precise locations, with clear excitatory and inhibitory regions, while ____ _____ also respond to oriented stimuli but across a wider area, without sensitivity to exact positioning, and can detect both light and dark contrasts​

Function of ocular dominance columns

They help with visual activity

Characteristics of dorsal pathway

V1/V2 → MT → parietal cortex

path for objects motion/location

where or how pathway

Characteristics of ventral pathway

V1/V2 → V4 → inferotemporal cortex

path for objects identity (color/shape)

what pathway

Fusiform Face Area (FFA)

This brain region is crucial for recognizing and processing human faces, helping us identify individuals and interpret facial expressions.

Parahippocampal Place Area (PPA)

processes visual information related to places and environments, allowing us to navigate spaces and recognize locations.

Representation vs Recognition

1.) a pattern of neural activity in the brain that contains information about a stimulus

2.)  the process of matching a current stimulus's representation to a stored representation in memory, based on prior encounters with that stimulus

Figure vs. ground

1.) part of an image or visual scene that is perceived as the object of focus, often in the foreground.

2.)  the background or surrounding area that provides context for the figure but is not the main focus. It is often perceived as less detailed or prominent​

Good continuation

This refers to a Gestalt principle of visual perception which states that humans tend to perceive lines or patterns as following a smooth path.

Occlusion

 the phenomenon where one object partially covers or blocks another object, providing a cue about their relative positions in space.

EX - if a tree is blocking part of a car in a scene, we understand that the tree is closer to us, while the car is farther away, even though we don't see the entire car.

Curvature in V4

the processing of curved shapes and contours in the brain's visual area V4, a region responsible for the perception of complex features such as color and shape in visual stimuli.

Grandmother cells

A neuron that responds to a particular object at a conceptual level, firing in response to the object itself, a photo of it, its printed name, and so on

Types of agnosias

Visual, prosopagnosia, topographic agnosia

bayesian approach to perception

Visual system unconsciously combines “Two probability” to infer what type of scene produced the currently experienced retinal image

prior probability of all possible scenes, and

for each possible scene, the probability that it produced the current retinal image.