Neuroscience Test 2
Psychology 1 with 1 at Florida Institute of Technology
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Sensory Receptors
- How we receive information about the environment
- Specialized neurons that detect a variety of physical events
Sensory Transduction
- A process where stimuli impinge on the receptors and later their membrane potentials
- Sensory events are transferred into changes in the cells membrane potential
Receptor Potentials
- Electrical changes in the cells membrane potential
- They affect the release of neurotransmitters and modify the pattern of firing in neurons with which sensory receptors form synapses
- The information reaches the brain
Vision
- The sensory modality that receives the most attention because:
- The complexity of the sonsory organs of vision and large proportion of the brain that is devoted to the analysis of visual information
- 20% of the cerebral cortex plays a direct role in the analysis of visual information
Light
- Light is a narrow band of the spectrum of electromagnetic radiation with a wavelength between 380-760 nm is visible to humans
- Light is not qualitatively different from the rest of the electromagnetic spectrum ,but is part of the continuum that we humans can see
Color of Light
- Determined by the dimensions of hue, staturation, and brightness
- Light travels at a constant speed of 300K km per second
- Frequency of saturation varies, and slower oscillations lead to longer wavelengths, faster lead to shorter wavelengths
Perceptual Dimensions
- Wavelength determines the following perceptual dimensions of color:
- Hue: the dominant wavelength of color
- Brightness: Intensity of color
- Saturation: Purity of color
Wavelengths and color
- If all the radiation is of one wavelength, the perceived color is pure or fully saturated
- If the radiation contains all wavelengths, it produces no sensation of hue - appears white
- Colors with intermediate amounts of saturation consist of different mixtures of wavelengths
Vision
- An image must be focused on the retina in order for us to see
- The image causes changes in the electrical activity of million of neurons in the retina, which results in messages being sent through the optic nerves to the rest of the brain
Orbits
- Bony pockets in the front of the skull where the eyes are suspended
Sclera
- Tough, white outer coat of the eye
- Opaque and does not permit entry of light
- Eyes are held in place and moved by 6 extraocular muscles attached to the Sclera
Conjunctiva
- Mucous membranes that line the eyelid and fold back to attach to the eye
- Prevents contact lens that slipped off the cornea from falling behind the eye
Saccadic movement
The rapid, jerky movement of the eyes used in scanning a visual scene
Pursuit Movement
Movement that the eyes make to maintain an image of a moving object on the fovea
Cornea
- Outer layer at the front of the eye
- Transparent and admits light
Pupil
- Opening in the iris
- The amount of light that enters is regulated by the size of the pupil
Lens
- Situated directly behind the iris
- Consists of a series of transparent onion-like layers
Iris
- The pigmented ring of muscles situated behind the cornea
Ciliary Muscles
- A set of muscle fibers attached to the outer layer of the lens
- Can alter the shape of the lens because of the contractions of these muscles
Accommodation
Changes in shape of the lens that permit the eye to focus images of near or distant objects on the retina
Vitreous Humor
- A clear, gelatinous substance
- "glassy liquid"
Retina
- The neural tissue and photoreceptive cells located on the inner surface of the posterior potion of the eye
- Interior lining on the back of the eye
- Rods and cones (photoreceptors), layers of cell bodies, axons, and dendrites are located in the back of the retina
Cones (photoreceptor)
- Most prevalent in the central retina; found in the fovea
- Sensitive to moderate-to-high levels of light
- Provide information about hue
- Provide excellent acuity
- Provides us with the most information about our environment; responsible for our daytime vision
Rods (photoreceptor)
- Most prevalent in the peripheral retina; NOT found in the fovea
- Sensitive to low levels of light
- Provides only monochromatic information
- Provides poor acuity
- Highly outnumber Cones
Optic Disk
- The location of the exit point from the retina of the fibers of the ganglion cells that form the optic nerve
- Responsible for the blind spot because no receptors are located there
Bipolar Cells
- A bipolar neuron located in the middle layer of the retina, conveying information from the photoreceptors to the ganglion cells
- The photoreceptors form synapses with these bipolar cells
- Neurons whose 2 arms connect the shallowest and deepest layers of the retina and form synapses with ganglion cells
Ganglion Cells
- Neuron located in the retina that receives visual information from bipolar cells; its axons give rise to the optic nerve
- Its axons travel through the optic nerves and carry visual information into the rest of the brain
Horizontal and Amacrine Cells
- Neurons within the retina that interconnects adjacent photoreceptors and the outer processes of the bipolar cells
- Transmits information in a direction parallel to the surface of the retina and combines messages
Photoreceptors (General info)
- Rods and Cones consist of an outer segment connected by a cilium to an inner segment which contains the nucleus
- Contains several hundred lamellae
Lamellae
- Thin plates of membrane
- Means "thin layer"
Photopigments
- Special molecules embedded in the membrane of the lamellae
- Its a chemical that takes part in the chain of events that lead to visual perception
- A protein dye bonded to retinal and is responsible for the transduction of visual information
- A human rod contains 10 million of these
Opsin
- Class of protein that, together with the retinal, constitutes the photopigments
- There are several forms such as rhodopsin
Retinal
- A chemical (Lipid) synthesized from Vitamin A
- Joins with an opsin to form a photopigment
Rhodopsin
- A particular opsin (photopigment), found in rods
- Before it is bleached by the action of light is has a pinkish hue
- When it is exposed to light it breaks into rod opsin and retinal and turns into a pale yellow
Photopigment and the Receptor Potential
- Splitting of the photopigment, rhodopsin, produces the receptor potential: a change in the membrane potential of the photoreceptor
- The receptor potential affects the release of neurotransmitter by the photoreceptor which alters the firing rate of the bipolar cells with which the photoreceptors communicates. This info is then passed on to the ganglion cells
Dorsal Lateral Geniculate Nucleus (LGN)
- A group of cell bodies within the body of the thalamus
- Receives inputs from the retina and projects to the primary visual cortex
- Contains 6 layers of neurons, each receives input from only one eye
- Neurons in the 2 inner layers contain cell bodies that are larger than those in the outer 4 layers
Magnocellular Layers
- Inner 2 layers of the LGN
- Transmits information necessary for the perception of form, movement, depth, and small differences in brightness to the primary visual cortex
Parvocellular Layers
- Outer 4 layers of the LGN
- Transmits information necessary for perception of color and fine details to the primary visual cortex
Koniocellular Sublayers
- Sublayers within the LGN
- Found ventral to each of the magnocellular and parvocellular layers
- Transmits information from short-wavelength (blue) cones to the primary visual cortex
Calcarine Fissure
A horizontal fissure in the medial posterior occipital lobe
Striate Cortex
- The primary visual cortex
- contains dark-staining layer
Optic Chiasm
- A cross shaped connection between optic nerves located below the base of the brain
The Primary Visual pathway
- The optic nerves join together to form the x-shaped optic chiasm
- Axons from ganglion cells cross through the chiasm and ascend to the dorsal lateral geniculate nucleus of the opposite side of the brain
- Axons from the outer halves of the brain remain on the same side of the brain
- The lens inverts the image of the world projected on the retina and each hemisphere receives infro from the contralateral half of the visual scene
Example of the Primary Visual Pathway
- If a person looks straight ahead, the right hemisphere receives information from the left half of the visual field and the left hemisphere receives information from the right
- You do NOT say that each hemisphere receives visual infromation soley from the contralateral eye
Other Pathways
- Other pathways, especially those that travel to the optic tectum and other midbrain nuclei, coordinate eye movements, control the muscles of the iris and ciliary muscles and help to direct our attention to sudden movements that occur in the periphery of our visual field
The Receptive field
- Part of the visual field that an individual neuron "sees'
- Place in which a visual stimulus must be located to produce a response in that neuron
- The location of the receptive field of a particular neuron depends on the location of the photoreceptors that provide it with visual infromation
Central vs. Peripheral Acuity
Ganglion cells in the fovea receive input from a smaller number of photoreceptors than in the periphery and hence provide more acute visual information
These receptor-to-axon relationships explain that our foveal vision is very acute but our peripheral vision is much less precise
These receptor-to-axon relationships explain that our foveal vision is very acute but our peripheral vision is much less precise
ON/OFF Cells
- ON cells excited by light falling in the central field and inhibitited by light falling in the surrounding field
- OFF cells respond in the OPPOSITE manner
- ON/OFF cells project to the superior colliculus, involved in the VISUAL reflexes; does not play a direct role in form PERCEPTION
Protanopia
- "first-color defect"
- Inherited form of defective color vision in which read and green hues are confused
- These people see shades of yellow and blue; both red and green look yellowish
- Visual acuities normal
- Sensitivity to lights of different wavelengths
- Red cones filled with green cone opsin
Deuteranopia
- "second-color defect"
- Defective color vision similar to Protanopia except green cones are filled with red cone opsin
Tritanopia
- "third-color defect"
- Rare form of defective color vision where hues and short wavelengths are confused
- See greens and red
- Retinas lack blue cones which causes their absence to not noticeably affect visual acuity
Receptive fields of color-sensitive ganglion cels
- Ganglion cells respond specifically to pairs of primary colors: red versus green and yellow versus blue
- Retina contains 2 kinds of color-sensitive ganglion cells: red-green cells and yellow-blue cells
- Response characteristics of these cells to light of different wavelengths are determined by circuits that connect the 3 types of cones with the 2 types of cells
Opponent-Color system
- Explains why we cannot perceive a reddish green or a bluish yellow
- An axon that signals red or green (or blue or yellow) can either increase OR decrease its rate of firing; cannot do both at same time
Simple Cell
- An orientation-sensitive neuron that have receptive fields organized in an opponent fashion
Layers of the Striate Cortex
- Consists of 6 principal layers and several sublayers arranged in bands parallel to the surface
- Layers contain the nuclei of cell bodies and dendritic trees that show up as bands of light or dark sections of tissue that have been dyed with a cell-body stain
General anatomy of Striate Cortex
- Contains a map of the contralateral half of the visual field
- Map is distorted; 25% of the striate cortex is devoted to the analysis of info from the fovea, which represents a small part of the visual field
Hubel & Weisel- Visual Cortex
- Discovered neurons in the visual cortex combines info from several sources
- It detects features that are larger than the receptive field of a single ganglion cell in the LGN
Orientation and Movement
- Most neurons in the cortex are sensitive to orientation
- Some neurons respond best to vertical lines, some to horizontal, and some to lines in between the two
- An orientation-sensitive neuron in the striate cortex will become active only when a line of particular orientation appears within its receptive field
Simple Cells
- When some orientation-sensitive neurons have receptive fields organized in an opponent fashion
Complex Cell
- A type of neuron that respond best to a line of a particular orientation but does not show an inhibitory surround; it continues to respond while the lines were moved within the receptive field
Hypercomplex Cells
- Respond to lines of a particular orientation but have an inhibitory region at the end (or ends) of the lines which means that the cells detect the location of ends of lines of a particular orientation
Sine-wave Grating
- Looks like a series of fuzzy, unfocused parallel bars
- Along any line perpendicular to the long axis of the grating, the brightness varies according to a sine-wave function
- This grating is designated but its spatial frequency
Spatial Frequency
- The spatial frequency of a sine-wave grating is its variation in brightness measured in cycles per degree of visual angle
- The relative width of the bands in a sine-wave grating
High vs. Low Spatial Frequencies
- Small objects, details within a large object, and large objects with sharp edges provide a signal rich in high frequencies
- Large areas of light and dark are represented by low frequencies
- An image deficient in high frequency info looks fuzzy and out of focus
- The most important visual info is that in low spatial frequencies because without it its difficult to perceive images
Retinal Disparity
- A stimulus that produces images on slightly different parts of the retina of each eye
- Points on objects located at different distances from the oberver will fall on slightly different locations on the 2 retinas
- Provides the basis for stereopis
Binocular Vision and Binocular Cells
- Neurons that respond to visual stimulation of either eye
- Many of the binocular cells have respond patterns that appear to contribute to the perception of depth
- In most cases the cells respond most vigorously when each eye sees a stimulus in a slightly different location
Depth Perception
- Perception of depth involves mostly cues that can be detected monocularly (one eye alone)
- Perseptive, relative retinal size, loss of detail through haze, and relative apparent movement of retinal images as we move our heads all contribute to depth perception and do NOT require binocular vision
Stereopis
- Important in the visual guidance of fine movements of the hands and fingers
Extrastriate Cortex
- Receives fibers from the striate cortex and projects to the inferior temporal cortex
Dorsal Stream
- Involved in the perception of spatial location, beginning with the straite cortex and ending with the posterior parietal cortex
Ventral Stream
- Involved in the perception of form, beginning with the striate cortex and ending with the inferior temporal cortex
Color Constancy
- Constant appearance of colors and objects viewed with the inferior temporal cortex
- Our visual system compensates for the source of the light by comparing color composition of each point in the visual field with the average color of the entire scene
- This compensation helps us to see what is actually there
Cerebral achromatopsia
- Inability to discriminate among different hues
- caused by damage to area V8 of the visual association cortex
- These patients cannont remember colors of objects they saw BEFORE their brain injury
Visual Agnosia
- Deficits in visual form perception in the abscence of blindness caused by brain damage (in the ventral stream)
- "failure to know"
- Inability to perceive or identify a stimulus by means of a specific sensory modality
Color Perception
- Our ability to perceive different colors helps us to perceive different objects in our environment
- V8 involved in color perception
- To perceive and understand what is in front of us, info about color must be combined with other forms of info
V8
- Color sensitive region in the inferior temporal cortex
- Involved in color perception and memories of colors of certain objects
Color Form
- The analysis of info that leads to the perception of form begins with neurons in the striate cortex that are sensitive to orientation and spatial frequency
- These neurons send info to V2, then relayed to subregions of the ventral stream
Lateral Occipital Cortex (LOC)
- Involved in perception of objects other than peoples bodies and faces
- Large region of the ventral stream
- Responds to a wide variety of objects and shapes
Prosopagnosia
- Common symptom of visual agnosia
- Inability to recognize particular faces
- Cannot recognize the particular configuration of these features that identifies an individual face
Fusiform Face Area (FFA)
- Special face-recognizing circuits are found in the FFA
- Involved in the perception of faces
- Shows greatest response to faces
Extrastriate Body Area (EBA)
- Involved in the perception of the human body and body parts other than faces
- Region of the ventral stream
- Shows greatest response to headless bodies and body parts
Parahippocampal Place (PPA)
- Region in the medial temporal cortex
- Involved in perception of particular places or "scenes"
- Activated by the sight of scenes and backgrounds
- Scene recognition does not depend on recognition of particular objects found within the scene
Facial Composition Recognition
- 3 ways to recognize individual faces- differences in features, contour, and configuration of features
Optic Flow
- Motion of points in the visual field caused by relative movement between the observer and environment
- Provides info about the distance of objects from the observer and the direction of movement
- Will tell you where you are heading, how fast you are approacing an item in front of you, and whether you will pass to the left or right
Akinetopsia
- Inability to perceive movement
- Brain damage to the V5
Intraparietal Sulcus (IPS)
- Involved in perception of location, visual attention, and control of eye and hand movements
Pitch
- Determined by the frequency of vibration
Hertz
- Cycles per second (measures pitch)
Loudness
- Corresponds to intensity
Timbre
- Corresponds to complexity
- Provides info about the nature of the particular sound
- Specific mixture of different frequencies of vibration determine the sounds timbre
Tympanic Membrane
- Eardrum
- Vibrates with sound
Ossicle
- 1 of 3 bones of the middle ear
- Set into vibration by the tympanic membrane
Malleus
- 1st of 3 osscles
- "hammer"
- Connects with the tympanic membrane and transmits vibrations via the incus and stapes to the cochlea
Cochlea
- Snail shaped structure of the inner ear that contains the auditory transducing mechanisms
- Contains the receptors
- Filled with fluid therefore sounds transmitted through the air must be transferred into liquid medium
Oval Window
- Opening in the bony process surrounding the cochlea
Sound Waves
- Changes in air pressure from sound waves move the ear drum in and out
Organ of Corti
- Sensory organ on membrane that contains auditory hair cells
- Receptive organ
Hair Cell
- Receptive cell of the auditory apparatus
Deiters's Cell
- Anchors the hair cells to the basilar membrane
Round Window
- Membrane-covered opening that allows the fluid inside the cochlea to move back and forth
Cilia
- Involved in the movement of auditory sensory info
- Within the hair cells
Tip Link
- Elastic filaments attached to the tip on one cilium to the side of the adjacent cilium
Insertional Plaque
- Points of attachments between the ciliums
Cochlear Nerve
- Branch of the auditory nerve that transmits auditory info from the cochlea to the brain
- Receive info from the the inner hair cells (95%)
Cochlear Nucleus
- Group of nuclei in the medulla that receive auditory info from the cochlea
Superior Olivary Complex
- Involved with localization of the source of sounds
Lateral Lemniscus
- Band of fibers that carries fibers through the auditory system
Tonotopic Representation
- Topographically organized mapping of different frequencies of sound that are represented in a particular region of the brain
Dorsal vs. Ventral Streams
- Dorsal: Terminates in the posterior parietal cortex, involved with sound localization
- Ventral: Terminates in the parabelt region and is involved in the analysis of complex sounds
Place Code
- System by which info about different frequencies is coded by different frequencies is coded by different locations on the basilar membrane
Cochlear Implant
- Electronic device surgically implanted in the inner ear that can enable a deaf person to hear when they have damage to hair cells
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STUDYBLUE makes things that make you better at school.
Things like online flashcards with photos and audio.
Things like personalized quizzes and friendly reminders about when (and what) to study next.
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STUDYBLUE exists to make studying efficient and effective for every student, for free. Join us.
“I have used this website for three exams, and I see a huge difference in my test results.”
Naj
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