* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download COLOUR VISION Newton`s Prism Experiments: a white light beam
Survey
Document related concepts
Emotional lateralization wikipedia , lookup
Stimulus (physiology) wikipedia , lookup
Perception of infrasound wikipedia , lookup
Psychophysics wikipedia , lookup
Emotion perception wikipedia , lookup
Visual selective attention in dementia wikipedia , lookup
Sensory cue wikipedia , lookup
Neuroesthetics wikipedia , lookup
C1 and P1 (neuroscience) wikipedia , lookup
Cognitive neuroscience of music wikipedia , lookup
Feature detection (nervous system) wikipedia , lookup
Sensory substitution wikipedia , lookup
Inferior temporal gyrus wikipedia , lookup
Embodied cognitive science wikipedia , lookup
Transcript
COLOUR VISION Newton’s Prism Experiments: a white light beam refracts into all colours of the visible light spectrum when passed through a prism – can only be split once but can be converged to form white again The Electromagnetic Spectrum: a continuum of all wavelengths (not discrete groups) – visible wavelengths range from 400700nm - Small = dangerous (dangerous -> pretty -> useful) Wavelength: difference between two troughs for crests – objective (cannot be argued with) Colour: - Subjective – not absolute, purely in your head, “colour is an experience” - Colour is a continuum not a series of discrete categories (categories came from newton – 7 categories because he wanted to match the number of colours to the number of notes in a music scale) - Objects appear to be whichever colour they reflect i.e. white is reflecting all wavelengths, black is absorbing all - Colour is an experience resulting from a perceptions of wavelengths therefore black and white qualify as colours - Light – Additive colour mixtures i.e. areas have an addition of more wavelengths so white is “seen” - Paint – Subtractive colour mixtures i.e. areas have less wavelengths being reflected because more wavelengths are being absorbed by the addition of more paint so a mix of all results in black being “seen” - More than one wavelength is reflected from an object to create “colour” Photoreceptors: Rods (NIGHT – SCOTOPIC) - Only one type – as a result, they are not tuned to - Several types, each tuned to a different wavelength Principle of Univariance: a receptor’s activity - Mostly in fovea is related to the number of photons it catches - Lower sensitivity not the type (wavelength) of photon - Day vision: photopic – rods are all over-stimulated so its wavelengths so colour is not “seen” just brightness o o - Cones (DAY – PHOTOPIC) Probability of absorbing photons is heighted down to cones during the day None in central fovea, high sensitivity, night vision (scotopic) Young’s Colour Theory - Logic says that the number of cones should be limited Metamers: two different stimuli’s appear to be identical due to the equal ratios of wavelengths If there were 2 cone types: - We could match any given wavelength by adjusting the intensities of almost any two other wavelengths (metamers) and there would be a single wavelength appearing grey (“neutral point”), where the firing of both channels is equal - This isn’t how it works in humans Colour Matching Experiments (Young, 1802) - For humans, metamers are created by mixing 3 or fewer primary wavelengths to create an intensity matching that of a single wavelength so they are seen as the same “colour” MULTISENSORY PROCESSING Important Principles: • Spatial Correspondence: info to different senses from the same event from SAME SPACE • Temporal Synchrony: info to different senses from the same event comes SAME TIME Evidence: • McGurk Effect (Stimulus identification): mismatching information changes perception -> auditory component paired with visual component of a sound -> third sound created. Demonstrates: spatial and temporal synchrony. • • Crossmodal Cueing: irrelevant sounds influence visual detection o Task: is there a visual target? (Present vs. absent), Conditions: irrelevant auditory cue (in/valid) o Finding: irrelevant auditory stimuli can influence the detection of a visual target Ventriloquist Effect: vision effects auditory – demonstrates temporal synchrony: the brain infers that the visual and auditory information must be from the same source – which should be in the same location • The Rubber Hand Illusion: visual-tactile integration – illustrates the importance of temporal synchrony • Summary: this evidence behaviourally reflects multisensory interactions Mechanisms: • Multisensory Convergence Zones (Feedforward Processing) • Initial processing in sensory specific zones • Subsequent (later/higher) processing by multisensory ‘convergence zones’ Standard View Of Multisensory Processing: • Initially in unimodal sensory cortex – subsequent in multisensory convergence zones = Feedforward connections/processes • Evidence for multimodal responses in primary sensory area = feedback and lateral connections Anatomical Tracing Studies: Highly interactive network that integrates information from the senses for conscious perception (Not just Feedforward / strictly hierarchical) Mechanisms Summary: Several key areas of the brain contain neurons that respond to sensory inputs from two or more modalities (e.g., superior colliculus, parietal, temporal and prefrontal cortex) and are superadditive. Needs revision to include direct connections between sensory areas, & more extensive feedback connections. Cross-Modal Mappings & Synaesthesia • Synaesthesia: perception of a specific stimulus induces a concurrent and distinct experience within a modality/s • Measures • o Direct: subjective report, consistency over time – can characterise phenomenon but doesn’t say how it occurs o Indirect: look at the effect it has on other tasks – objective and may indicate mechanisms Implications: synaesthetic congruency effects give objective measures of the experiences