BIOL2005 exam all revision

what is sensation

process of sensing our environment using the 5 sense

what is perception

intepretation of the senses, uses representations

what does perception rely on

sense organ, receptor processes, cns, memory, past experiences, attention

what 3 levels does the cns handle information

sensory, association and motor

bottom up process

data based and based on incoming stimuli. data-driven processing. all information is derieved from the itself, no previous knowledge required

top-down processing

knoweldge based, based on cognitive factors, previous knoweldge, use of contextual information and represenations held in memory, intepretation to resolve ambuity, stored memory, knoweldge, cogntive processs, prediction

what is the stimulis/object

The actual thing you’re seeing, hearing, tasting

what is representation

The mental ‘image’ or ‘model’ of the stimulus/object

what are concepts

‘Categories’ of things

how does transmission of information work

receptor is stimulated, electrical activity travels along axon, neurotransmitters empty into synaptic cleft, neural transmitters are recieved on specific receptor sites, changes in second neuron to continue flow of information.

what are modules

Specific brain areas process information about specific stimuli, operate independently but are interconnected

what does light sensative tissue in the eye do

Converts chemical and electrical events into neural information, Transmits neural impulses to various areas of the visual cortex via the optic nerve

describe Rods

response best in dim light, useless in day, black and white vision, 120 mil per eye, pigment is rhodospin

describe cones

there are red, green and blue cones, not as sensitive to light, used for daylight vision, for color vision, there is 6 mil per eye (60% red 5-10 blue and 30% green, the pigment is odopsin

where are cones located

Cones: Heavily concentrated in the fovea, but no ‘blue’ cones in the central fovea • Rods: Absent from the fovea

what is Visual acuity

The spatial resolution of the visual processing system

what are receptive fields

Area on receptor surface that affects response of neuron • Receive and respond to light

what is horizontal transmission

Signals are sent horizontally between receptors by horizontal cells

what if Light in ON centre of receptive field

INCREASED FIRING in ganglion cell

what if Light in OFF surround of receptive field

DECREASED FIRING/ INHIBITED ACTIVITY in ganglion cell

what is simultaneous contrast

People see an illusion of changed brightness or color due to effect of adjacent area

how does the lateral genicule nucleus operate as a relay station

Receives input from retina • Has centre-surround cell structure • Sends output to V1

how does lateral genicule nucleus function as an amplifier

• Involved in filtering redundant information • Boosting signals from parts of the visual field • Modulating information from eyes

what is the magnocellular pathway

specialised for motion detection, broad outlines and depth, Dominant in peripheral vision and useful for rapidly detecting changes in the environment (large and fast cell)

what is the parvocellular pathway

specialised for form, color and detail, dominant in central vision (foveal), critical for object recognition, reading and identifying faces, small slow and sensitive

what is retinotopic mapping

Objects in the environment tend to be processed in approximately neighbouring regions in the retina, LGN & V1

what is cortical magnification

Central vision is over-represented in the LGN and V1. The fovea takes up far more neural tissue per degree than the periphery

how does top down processing work in the LGN

V1 feedback modulates LGN responses. It does this through boosting relevant features/locations, • Increases efficiency of neural responding • Attentional modulation • Anticipatory activity

what are simple cortical cells

Neuronal receptive fields have excitatory and inhibitory areas • Side-by-side, NOT centre-surround, V1 simple sells are uninterested spot of night, responded to line stimuli of a specific orientation at a specific location

what are hypercolumns

full set of orientations for both eyes for the same patch of visual field

what are edge maps

as V1 simple cells are the “building blocks” for object perception Outputs from V1 cells are combined in later visual processing areas to form shapes, objects, scenes, and faces as objects can be approximated from just the edges

what are End-stopped V1 cell

Responds to corners, angles, bars pf specific length moving in specific direction

what is Glaucoma

Progressive damage to retinal ganglion cells and the optic nerve due to intraocular pressure • Peripheral vision lost first; central vision preserved until late • Loss of centre-surround processing

what is multiple sclerosis

mmune system attacks myelin in the CNS = slower neural conduction

what is Akinotopsia

“Motion blindness” • Caused by damage to area MT/V5, see world through brains

what is visual form agnosia

• Caused by damage to lateral occipital cortex • Cannot consciously recognise objects • Can guide actions toward objects accurately

what is grouping

Visual events are grouped into units or objects

what is segregation

Areas or objects are separated

what does V2 do

• Borders of 2D figures • Integrates edge fragments even if separated • Differentiate object from background (shapes)

what does V4 do

• Encodes curvature of a preferred orientation • Position invariant • Represent objects by combining these “boundary primitives” (objects)

list 3 rules that the brain uses when grouping

1. Grouping rules (heuristics) 2. Physical/semantic regularities 3. Helmholtz's likelihood principle

list the figure cues

convexity, size (small), surroundedness (enclosed), lower regions, symmetry

what are physical regualarity

• Regularly occurring physical properties • Horizontal and vertical orientation easier to perceive • Objects defined by areas of same colour/texture

what are semantic reguarities

• Learned associations between scenes and the objects that typically appear in them • Knowing the scene generates expectations about what's likely to be there

what is Helmholtz’s likelihood principle

Perception settles on whichever interpretation is most likely given the retinal input

what is selective attention

prioritising some inputs for deeper processing while suppressing others

what is Spotlight metaphor

attention as a movable region of enhanced processing

Exogenous cueing

Spotlight deployed reflexively by salient peripheral events

Endogenous cueing

directed voluntarily based on goals or symbolic cues

what is ADHD

Characterised by developmentally inappropriate and impairing levels of inattention, hyperactivity and impulsivity

WHAT are the 3 inverse problems are why

color: one cone response byt multiple physical light mixtures

depth: one flat image but infinite 3d scenes

size: One retinal size could result from a small and near object, or large far object

Brain compensates using cues and assumptions

what is additive vs subtractive color mixture

by combining lights (additive) or by combining physical materials like paints and inks (subtractive)

Trichromatic Theory

Colour is the ratio of activity across the three cones, not which single cone fires

Metamerism

multiple inputs collapse into the same output

Opponent-Process Theory

Colour vision caused by opposing physiological responses to: • Blue and yellow/red and green, Bipolar and ganglion cells in LGN excited by one colour and inhibited by the opposite colour

Oculomotor cues: Convergence

• Inward movement of eyes • Focus on objects nearby ( .)(. )

Oculomotor cues: Accommodation

• Changing shape of the lens • Focus at different distances ( . )( . )

examples of monocular cues

occulusion, relative size, vanishing point, height in field, texture gradient

what is Motion parallax

When you move, near objects sweep across the visual field faster than far ones

what is Binocular disparity and stereopsis

u have two eyes, difference between images and when the brain successfully merges twodimensional images from each eye to obtain a single 3D image

why is perception the root of behaviour?

An organism that could not act would have no need to perceive, output of perception is behaviour

what is the visual stream for recognising

ventral

what is the visual stream for acting

dorsal

Ungerleider & Mishkin monkey lesion paradigm, what happened if temporal lobe lesion

impaired object discrimination (what pathway)

Ungerleider & Mishkin monkey lesion paradigm, what happened if parietal lobe lesion

impaired landmark discrimination but object task largely spared. (where” pathway)

what is Optic ataxia

Dorsal stream damage, Can report seeing a target, but can’t reach accurately towards it

is ventral and dorsal pathways unconscious or uconscious?

ventral is largely conscious where dorsal is not

function of ventral pathway

Recognition, a conscious percept

functional of dorsal pathway

Motor control, guided movement

why is motion crucial for survival

• Detecting threats • Navigation • Object tracking • Social interaction

what is local motion

single edges moving across small parts of the visual field, complex cells in the V1 respond to this

what is global motion and how does it occure

coherent motion over larger regions of space. V1 motion signals go to MT(V5), MT neurons pool multiple local motion signals, which results in global motion

(top down influences on motion processing), what is the flash-lag effect?

briefly flashed object and a continuously moving object that are physically aligned at the exact same position are perceived as being separated

(top down influences on motion processing), what is implied motion?

Static images can produce a sensation of movement

(top down influences on motion processing), what is apparent motion?

two static images in quick succession are seen as one thing moving can be affected by expectations

what does optic flow mean

As you move forward, the visual world streams outward in a structured pattern, flow guides movement and carries out information about environment structure

what is focus of expansion

Flow radiates from a single point

what is transport and the brain areas associated with it

carrying the hand to where the object is, superior parietal (V6A) & parietal reach region → dorsal premotor cortex

what is grip and the brain areas associated with it

shaping the hand to what the object is (size, shape, and orientation), anterior intraparietal area (AIP) → ventral premotor cortex (F5)

what is Gibson’s (1979) Ecological Approach

rejected the idea that perception requires reconstruction of the world, Argued optic flow directly specifies the environment for us to interact with

what is affordance

what the environment offers an animal for action

what is Psychophysics

Relating the physical stimulus to the psychological response

what is absolute threshhold

the smallest stimulus that can be detected

what is difference threshold

the smallest detectable difference between two stimuli

what is Random dot kinematograms and the brain part associated with it

• A field of moving dots wherein a proportion move together (signal), the rest move randomly (noise)

• MT/V5 pools local dot motion into a single global-motion signal

what is perception without awareness, and an example

stimuli can be processed, but never consciously experienced • Binocular rivalry; blindsight

what is perception without input, and an example

stimuli can be consciously experienced, but nothing is there • Charles Bonnet; dreams; hallucinations; schizophrenia

what is atypical activation and an example

Stimuli from one sense can trigger an experiences in another sense • Synaesthesia

what is blindsight and the associated brain region

Damage to V1 → blindness to part of the visual field , Patients report seeing nothing But perform above chance at detecting motion, location orientation

what is charles bonet syndrome

Vivid visual hallucinations in people losing their sight, Reduction in sensory input to the brain causes spontaneous activity in visual association cortex

what are hallucinations

Simulated sensory activation in the absence of any external input, can be drugged induced of psychatric, also sense deprevation and sleep

what is synethesia

stimulation of one sensory or cognitive pathway leads to involuntary experiences in a second sensory or cognitive pathway, (seeing colors when listening to music

physical vs perceptual definition of sound

physical: changes in pressure in air, perceptiual: experience of hearing

what is condensation

Speaker diaphragm moves out, pushing air molecules TOGETHER

what is refraction

Diaphragm moves in, pulling air molecules APART

what is frequency

Number of CYCLES of pressure change per second, measured in HZ, related to pitch

what is amplitude

Difference in pressure between high and low peaks of wave, experience of loudness, large changes in air pressure = more loud

what is loudness

Most closely related to level or amplitude of an auditory stimulus, measured in decibles

what is pitch

low pitch, slow vibration, produce by larger, the opposite for high pitch

what is the human hearing range

Human auditory system most sensitive to frequencies ~2000 - 5000Hz