Perception Flashcards
Ventral stream (or ‘What’-pathway)
One half of the ‘two-streams hypothesis’; the ventral stream carries visual information from the primary visual cortex in the occipital lobe to the temporal lobe, and is involved with object identification and recognition.
The ventral stream has strong connections to the medial temporal lobe, which stores long-term memories, as well as the limbic system, which controls emotion.
Agnosia
A general term for the inability to process sensory information.
It exists in different forms such as apperceptive agnosia and associative agnosia.
Associative Agnosia
The inability to recognize complex objects. The person is able to recognize simple shapes and can copy drawings, however, is unable to recognize complex objects even after copying them.
Apperceptive agnosia
The inability to recognise simple shapes or to draw shapes. Deficit in early visual processing.
The primary visual cortex
The first cortical area to receive visual input
Edge detectors
They respond positively to light on one side of a line and negatively to light on the other side
Bar detectors
They respond positively to light in the center and negatively to light in the periphery, or vice versa.
Stereopsis
The ability to perceive 3-D depth
Gestalt principles of organization
Gestalt principles of organization help explain how the brain segments visual scenes into objects
There are six individual principles commonly associated with gestalt theory: similarity, continuation, closure, proximity, figure/ground, and symmetry & order.
Look at figure: 2.12 on page 47.
Phonemes
Phonemes are the smallest unit of speech distinguishing one word (or word element) from another
(Example: the differences between “tap”, “tab,” “tag,” and “tan.”)
Template matching
Theory of pattern recognition: a way to identify objects by aligning the retinal image of a stimulus to a stored template of a pattern.
Fusiform gyrus
Particular region of temporal lobe associated with face recognition.
Retina
The innermost layer of cells within the eye contains two photoreceptor types: cones, responsible for color vision and high resolution, and rods, which require less light but provide lower resolution and no color information.
Cones
It’s one of the two photoreceptors in the eye, Cones handle color vision and produce high resolution. We primarily use cones during the day.
Rods
it’s one of the two photoreceptors in the eye, Rods need less light to trigger a response, but they produce poorer resolution and no information about color. Rods are what we primarily use when we see in the dark.
Ganglion Cells
Ganglion cells are a type of neuron found in the retina of the eye. They are the final output neurons of the retina and play a crucial role in transmitting visual information from the eye to the brain. Ganglion cells receive input from other types of retinal neurons, such as photoreceptor cells (rods and cones) and bipolar cells, which process visual stimuli and convert them into electrical signals.
Bottom-up processing
Involves information traveling ‘up’ from
the stimuli, via the senses, to the brain
Voicing
A feature of phonemes produced by the vibration of the vocal cords.
Place of articulation
Refers to the location at which the vocal tract is closed or constricted in the production of a consonant phoneme.
The “Where”-pathway
The pathway going to the parietal lobe specializes in representing spatial information and coordination.
Fovea
It’s a part of the retina, where the cones are especially concentrated.
Top-down processing
The contribution or guidance of prior knowledge, experiences, and expectations on incoming information (“What we know/expect, influences what we perceive.”
Word superiority effect
This effect describes the fact that it is easier to recognize a letter when it is a part of a word, than when it stands for itself. Such as the example. “The cat or Tae cht” (page. 63)
Feature analysis
A pattern recognition model, where stimuli are thought of as elemental features.
Change blindness
The inability to keep track of all information in a complex scene.
2½-D sketch and 3-D model
Proposal made by David Marr (1982): Various sources of information come together to create the so-called 2½-D sketch, that identifies where various visual features are located in space relative to the viewer. Creation of a 2½-D sketch requires a lot of information but a lot more is necessary to translate such a sketch into an actual perception of the world. Such a sketch represents only parts of surfaces and does not yet identify how these parts go together to form images in the environment. The term 3-D model is used to refer to such a later representation of objects in a visual scene.
Deep Convolutional Network
Object recognition method used by AI: The image processing starts from the stimulus - a pixel representation of an image - followed by 5 (or more) layers of pattern recognizers.
Early phase of vision
Shapes and objects are extracted from the visual scene
Later phase of vision
Shapes and objects are recognized
The process of visual perception in 4 steps?
1) Light enters through the cornea
2) Light passes through the aqueous humor
3) Light passes through pupil, lens, and vitreous humor
4) Light strikes and stimulates the retina.
The blind spot (location)
We have a blind spot where the optic nerve is. There isn’t a retina to receive the signal in the blind spot, because all the signals are collected here.
Texture gradient
Elements tend to appear more closely packed together as the distance from the view increases
Motion parallax
Provides 3D information about when an object is in motion
What part of the brain is responsible for face recognition?
Fusiform gyrus.
A different part of the brain creates object recognition
Prosopagnosia
Face blindness
(Brain trauma to the fusiform gyrus)
Categorical perception
We are better at distinguishing between categories than within them
The McGurk effect
An auditory-visual illusion that illustrates how perceivers merge information for speech sounds across the senses
(For example, when we hear the sound “ba” while seeing the face of a person articulate “ga,” many adults perceive the sound “da,” a third sound which is a blend of the two.)
Principle of proximity (Gestalt principles)
That items close together are likely to be perceived as part of the same group
Principle of similarity (Gestalt principles)
When items share some visual characteristic, they are assumed to be related in some way
Psychological nystagmus
A tremor! Our retinal image of an object is not constant. Its position changes over times. Parts of an image start to disappear from our perception when the tremor doesn’t occur.
Principle of closure (Gestalt principles)
People will fill in blanks to perceive a complete object whenever an external stimulus partially matches that object
On-off cell
When the light hits the centre of responsive field the rate of spontaneous firing of the cell increases.
Accommodation (The lens)
The Lens changes shape to focus incoming light falling on the retina onto the fovea
Off-on cell
When the light hits the centre of receptive field the rate of spontaneous firing decreases.
Organisation of a Hypercolumn in the Visual Cortex.
The hypercolumn is organized in one dimension according to whether input is coming from the right eye (R) or left eye (L). In the other dimension, it is organized according to the orientation of lines to which the receptive cells are most sensitive. Adjacent layers of cells represent similar orientations
Photochemical process
e.g. conversion of light into neural signals that happens in photoreceptors (rods, cones) in the eye
What did Kuffler’s research showe and when?
In 1953 Kuffler showed how information is encoded by the ganglion cells in the retina.
