UCSD COGS 101A - Midterm 1

sensation

The process of transforming physical stimuli to electrical (neuronal) signals

perception

The process of interpreting electrical (neuronal) signals for conscious awareness or for action

top-down processing

Processing that is based on knowledge (e.g. after hearing the word "dog", it is easier to see a dog in the image)

bottom-up processing

Processing that is only based on the stimuli received

theoretical construct

Entity/concept that we are interested in but that are not physically observable and measurable (e.g. a person's experience of color)

operational definition

An external behavior that "stands in" for a theoretical construct we are interested in, so we can observe and measure it

criterion of falsifiability

A theory has to be falsifiable in order to be scientific (e.g. humans need oxygen to survive)

psychophysics

The study of the relationship between mental and physical experience

method of limits

Stimulus is presented in order of intensity until undetectable

method of constant stimuli

Participant is presented with a fixed set of stimuli covering a range of intensities that are presented repeatedly in random order, and the participant must indicate whether or not each stimulus was detected

method of adjustment

Participant adjusts the intensity of a stimulus until it is detected (less accurate than method of limits)

adaptive staircase

Stimuli intensity is adjusted based on participant response

computational

The Marr's level of analysis that is the most abstract, asking: What does this system do? What kind of problems does it solve?

algorithmic

The Marr's level of analysis that asks: How does the system do it? What steps did it take to solve the problem?

implementation

The Marr's level of analysis that is the most concrete, asking: How is it physically instantiated in the brain? What happens to the system when I snip the circuit?

qualia

Individual instances of subjective, conscious experience

accommodation

The unconscious action of the ciliary muscles changing the shape of the lens in order to create a focused, clear image at different distances

blind spot

Area in our vision due to the lack of photoreceptors where the optic nerve leaves the eye

spectral sensitivity

The sensitivity of visual receptors to different parts of the visible spectrum

absorption spectrum

The range of a pigment's ability to absorb various wavelengths of light.

neuron

Nerve cell, has dendrites, a cell body, and an axon

propogated response

When an action potential travels along an axon without decreasing in size

depolarization

When the membrane potential becomes more positive, moving towards the threshold

hyperpolarization

When the membrane potential becomes more negative, moving away from the threshold

inhibition

A hyperpolarizing postsynaptic potential that is likely to decrease or stop the firing rate of a downstream neuron it synapses on

spontaneous activity

The baseline firing rate of a neuron with no stimulation

neural convergence

Synapsing of a number of neurons onto one neuron

lateral inhibition

Act of neurons in a neural circuit inhibiting its neighbors, making a stimulus easier to perceive and have more contrast (e.g. Hermann grid)

neural circuit

Group of connected neurons that fire as a unit (lateral inhibition and convergence only occur with these)

cones

Photoreceptors that detect color, operate under normal daylight conditions, and allow us to focus on fine detail (acuity), less neural convergence; there are many less of these, distributed in the middle of vision

rods

Photoreceptors that become active under low-light conditions for night vision (sensitivity), more neural convergence; there are many more of these

receptive field

Area that affects a neuron's firing rate

doctrine of specific nerve energies

The nature of a sensation depends on which sensory fibers are stimulated, not on how the fibers are stimulated

LGN

In the thalamus, receives and processes visual information from the retina (has more axons coming from the retina than axons sent to the cortex, and receives a lot of feedback from the cortex)

mind-body problem

Are mind and body separate and distinct, or is the mind simply the physical brain's subjective experience?

dualism

Mind and body are separate entities

materialism

Matter is the only reality; the mind is the brain

inverted eye

The outer segments of rods and cones are oriented to the back of the eye. Since the outer segment is the segment that interacts with light, light now has to travel through the optic nerve fibers and the inner segment, making it harder for the light to get to the photo-receptors inside our eye. We have the fovea centralis, which is avascular (no blood vessals), has minimal neural tissue, minimizing light scattering, allowing for high-acuity vision.

distal stimulus

Stimulus that is "out there" in the environment

proximal stimulus

Stimuli's representation on sensory receptors

transduction

Conversion of one form of energy into another (e.g. light energy that is transformed into electrical energy)

perceptual process

This has the following stages for vision:

1. Stimulus in the environment

2. Light is reflected and focused

3. Receptor processes (sensory receptors and transduction)

4. Neural processing

5. Perception (seeing something)

6. Recognition (seeing a dog)

7. Action