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86 Cards in this Set
- Front
- Back
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What is PERCEPTION?
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Mental REPRESENTATION emerging from SENSORY PROCESSING of ENVIRONMENTAL STIMULI in order to GUIDE BEHAVIOR
It's the INTERPRETATION of Neural Symbols |
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Visual AGNOSIA is?
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Inability to RECOGNIZE objects
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BOTTOM-UP processing is?
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Data-base processing= Processing based on INCOMING STIMULI from the environment
It is PASSIVE |
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TOP-DOWN processing is?
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- Knowledge based
- ACTIVE - Based on perceiver's PREVIOUS KNOWLEDGE |
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What is the Psychophysical level of Analysis?
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Measures the Stimulus-Perception relationship
EX: Discriminating between colours |
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What is the Physiological level?
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stimulus-physiology relationship
Ex: colored light generates a neural response in cat's cortex |
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What is the Physiology perception level?
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Brain activity is monitored as a person indicates what he sees
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What is the ABSOLUTE THRESHOLD?
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Smallest amount of stimulus energy necessary to detect Stimulus
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What is the Method of LIMITS?
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- Stimuli of different intensity is presented in increasing or decreasing order.
- Observer responds if he sees stimulus or not - CROSS OVER point is the THRESHOLD |
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What is the Method of Adjustment?
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- Adjust the stimuli intensity in CONTINUOUS manner until observer detects it
-Need repeated trial |
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What is the Method of CONSTANT STIMULI?
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-Replicates method of limits but RANDOMIZE trial
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What is the DIFFERENCE THRESHOLD?
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SMALLEST difference between 2 stimuli a person can detect
--> As MAGNITUDE of stimuli increases so does the DIFFERENCE of THRESHOLD |
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What is the Webber Law?
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Difference threshold / Standard Stimuli
=CONSTANT |
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What is the response compression?
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As intensity increases, the magnitude increase BUT NOT as rapidly as the intensity
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What is the visible spectrum of light?
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400-700nm
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What are the 3 layers of the eye?
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- FIBROUS TUNIC
- VASCULAR TUNIC - VITREOUS TUNIC |
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What is the Fibrous Tunic?
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"white" dense inflexible material encapsulating most of the eye as a PROTECTIVE coat
Turns transparent into what is known as the CORNEA Cornea plays a crucial role in the formation of CLEAR IMAGES on the RETINA |
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What is the Vascular Tunic?
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Mostly made up of CHOROID
Nourishes the entire eye structure Reduces light scatter due to its dark & heavy pigmentation |
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What is the Vitreous Chamber?
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2/3 of volume of the eye
Bounded by the lens and the retina |
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What does the IRIS?
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- Formed from the ciliary body in the Anterior chamber
- it REGULATES the amount of light received by the eye & dept field |
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The IRIS is composed of?
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2 LAYERS:
- Outer-pigmented layer (circular muscle) -Inner Vascularized layer (Radial muscle) |
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What is the LENS'S function?
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ACCOMMODATION
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What is the LENS composed of ?
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- CAPSULE
- EPITHELIAL LAYER - Lens |
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What is the RETINA composed of?
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3 LAYERS
- Retinal Ganglion cells - Collector cells (BIPOLAR, AMACRINE & HORIZONTAL) - Photoreceptors (Rods and Cones) |
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What are the characteristic of RODS?
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Large and Cylindrical
126 million rods More concentrated at outer edges of retina, and are used in PERIPHERAL VISION Rods are more sensitive to light than cones More sensitive to SHORT wavelenght (500 nm) |
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What are the characteristics of CONES?
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Small and Tapered
5 million cones Function best in relatively bright light (most sensitive at 560 nm) |
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Where is vision MOST acute?
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MACULA (center of the retina)
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What is the NEAR POINT?
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Occurs when lens can NO LONGER ADJUST for close object
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When does visual transduction occur?
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Occurs when the RETINAL absorbs 1 photon= ISOMERIZATION
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What is the VISUAL PIGMENT REGENERATION?
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Process needed for transduction
Retinal molecule changes shape , opsin molecule seperates, the retina shows PIGMENT BLEACHING Retina and Opsin must RECOMBINE to respond to light |
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What is 1/ threshold?
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SENSITIVITY which produces the Spectral Sensitivity Curve
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What is the PURKINJE SHIFT?
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ENHANCED SENSITIVITY to SHORT WAVELENGHTS during dark adaptation when shift from cone to rod vision occurs
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When does cone pigment absorbs best at?
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419 nm
532 nm 558 nm --> 560 nm |
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What part of the eye does the FOCUSSING?
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Cornea (which is FIXED) accounts for 80% of the focussing
Lens adjusts shape for object distance (20%) |
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What results to ALL-CONE FOVEAL VISION?
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HIGH VISUAL ACUITY
(1 to 1 wiring leads to ability to discriminate details) |
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What is LATERAL INHIBITION?
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the capacity of an excited neuron to reduce the activity of its neighbors
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What is the Hermann Grid?
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Example of LATERAL INHIBITION
See spots at an intersection |
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What is the MACH BANDS?
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Example of LATERAL INHIBITION
Seeing borders MORE SHARPLY |
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What is the SIMULTANEOUS CONTRAST?
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Example of LATERAL INHIBITION
Seeing areas of different brightness due to ADJACENT AREAS |
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What is the NEAR POINT?
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Distance at which your Lens can NO LONGER ADJUST
PRESBYOPIA |
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What is MYOPIA?
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Person cannot see from FAR
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What is HYPEROPIA?
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Person cannot see from CLOSE
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What is Hetcht's Psychophysical experiment?
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When a person sees light 7 visual pigment molecules are ACTIVATED
ONLY 1 visual Pigment is ISOMERISED per Rod & 7 RECEPTORS Must be activated Simltaneously |
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The ISOMERISATION of a single visual pigment molecule triggers?
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ENZYME CASCADE
= thousands of chemical reactions |
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What is MACULAR DEGENERATION?
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Destruction of cone rich fovea
= creates blind spot in central vision --> Person cannot see what they are looking at |
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What is RETINIS PIGMENTOSA?
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Degeneration of retina
=Attacks Peripheral ROD receptors --> poor vision on peripheral field |
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What is the DARK ADAPTATION?
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Process that causes the eye to INCREASE its sensitivity in the dark
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What are the 2 phases of DARK ADAPTATION?
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1) Rapid Increase for the 1st 3-4min (cone)
2) Increase again at 7-10min and 20-30min --> As soon as the light is extinguished BOTH cones and rods sensitivity increases. Cones are more sensitive at beginning |
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The RATE of DARK ADAPTATION matches the rate of?
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VISUAL PIGMENT REGENERATION
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What is Visual Pigment regeneration?
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Retinal molecule seperated from larger opsin molecule--> this seperation causes PIGMENT BLEACHING
To turn light into ELECTRICAL Energy RETINAL and OPSIN must be rejoined Cone pigment regenerates in 6 min Rod Pigment regenerates in over 30 min |
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When is the ROD-CONE BREAK?
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7-10 min
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Where is LOWEST Threshold for light?
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Middle of the spectrum
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Rods and Cones send signal VERTICALLY through?
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Ganglion cells, Ganglion Axons and Bipolar cells
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Signals are sent HORIZONTALLY through?
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Horizontal cells and Amacrine cells
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How do you determine spectral sensitivity?
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Using Monochromatic light flashes
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What is CONVERGENCE?
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Multiple neurons send signals to 1 neuron
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How many signals do each ganglion cells receive?
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Each ganglion cell receives 126 signals
(1 m ganglion and 126 m receptors) |
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What is the order of visual transduction?
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RETINA --> LGN (thalamus) --> STRIATE CORTEX (occipital lobe)--> signals are transmitted along 2 pathways: Temporal Lobe & Parietal LOBE
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What is the SUPERIOR COLLICULUS involved in?
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Controlling eye mvmt
Processing in the LGN 10% of fibers (90% --> LGN) |
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What are the LGN functions?
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- REGULATES neural info as it flows from the retina to visal cortex
- TRANSMITS signals to the CORTEX - ORGANIZES visual info (LGN receives more imput back from cortex than retina) |
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Layers 2,3,5 of LGN receive signals from?
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IPSILATERAL eye
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Layers 1,4,6 of LGN receive signals from?
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CONTRALATERAL eye
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What is the RETINOTOPIC MAP?
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Map in which EACH point on LGN corresponds to a point on the retina
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Simple cortical cell:
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Excitatory and inhibitory areas arranged side by side.
Responds best to bars of a particular ORIENTATION --> BEST to VERTICAL BARS |
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Complex cortical cell:
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Responds best to MOVEMENT of a correctly ORIENTED bar across the receptive field.
Many cells respond best to a particular direction of movement |
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End-stopped cortical:
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Responds to CORNERS, ANGLES, or bars of a particular length MOVING in a particular DIRECTION
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What is the CORTICAL MAGNIFICATION FACTOR?
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FOVEA has more cortical space than expected --> provides extra processing per high-acuity task
Fovea accounts for .01% of the retina, signals from the fovea account for 8 to 10% of retinotopic map on cortex |
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What are the LOCATION COLUMNS?
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Receptive fields at the same location on the retina are within a column
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What are the Orientation columns?
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Neuron within columns fire maximally to the same orientation of stimuli
Adjacent columns change preference in an orderly fashion |
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What is the Ocular Dominance column?
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Neuron in cortex responds preferentially to 1 eye
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What is the HYPER COLUMN?
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Location c. + Orientation c. + Ocular Dominance c.
=PROCESSING MODULE |
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What is the VENTRAL PATHWAY?
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- Located in TEMPORAL LOBE
-"WHAT" pathway -It begins in small or medium ganglion cell = called P CELLS -Axons synapse in layers 3,4,5,6 of LGN= PARVOCELLUAR LAYERS |
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What is the DORSAL PATHWAY?
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- "Where or HOW" pathway
(parietal lobe) -Begins in LARGE ganglion cells called M cells Axons synapse in layers 1 and 2 of LGN= MAGNOCELLULAR LAYERS |
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Places activate which part of brain?
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PARAHIPPOCAMPAL part
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Bodies activate which part of the brain?
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EXTRASTRIATE BODY AREA
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What is PROSPOAGNOSIA?
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Can't recognize faces
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What is NEURAL PLASTICITY?
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Neurons need environmental stimuli to develop fully
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Optic Nerve converge at?
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OPTIC CHIASM
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Temporal fibres project to?
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IPSILATERAL HEMISPHERE
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Nasal Fibres project to?
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CONTRALATERAL HEMISPHERE
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What is a FEATURE DETECTOR?
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Neurons that fire to SPECIFIC FEATURES of a stimulus
EX: Simple cortical cells, Complex cortical cells and End stopped cortical cells |
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What is SELECTIVE REARING?
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Use it or Loose it
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PARVO CHANNELS SEND:
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COLOR
TEXTURE SHAPE DEPT INFO |
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MAGNO CHANNELS SEND:
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MOTION INFO
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Single dissociation is:
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2 functions involve DIFFERENT MECHANISMS
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DOUBLE Dissociation is:
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2 functions involve different mechanism and Operate independently
(double dissociation between ventral and dorsal pathways) |
