Final practice percept & cogn

What does electromagnetic frequency and amplitude mean?

• frequency : hue

• amplitude/intensity : brightness

Opponent process colour theory

• we perceive colour in opposing processing pairs - like tug of war

• ex: red suppresses green, blue suppresses yellow

• colour processed in relation to each other

• red, green, blue. cones. LGN processes it into opposing colour pairs AFTER LEAVING THE RETINA

• comes up in colour blindness (red/green). also comes up in artists for striking colour combos. fatiguing the cones can create opposite images on your retina

Trichromatic colour theory

Young-Helmholtz theory

• we must have receptors which respond to shorter wavelengths, medium and for longer (blue, green, red) BEFORE LEAVING RETINA

• the cones overlap btw in what they can perceive

• see how this impacts colour blindness - we can see

Muller’s doctrine

• sensory pathway determines nature of perception. it is the neural code that is sent which is important

• origin of sensory information not important (stimulus)

• its all in your head

rods

• low res

• high sensitivity

• black/white

cones

• high res

• low sensitivity

• coloured sight

unconscious inference

• describes the unconscious, pre-rational processing of stimuli. reflexive action

• we see what we expect to see from past learning

• Hermann von Helmholtz

monocular cues

Occlusion or Interposition

Elevation

Relative Size

Linear Perspective

Aerial Perspective (clarity w distance)

Light & Shade

cortical colour blindness

colour blindness caused by damage in ventro-medial occipital and temporal lobes

olfactory pathways

Apperceptive agnosia

failure to

recognize objects, to discriminate

objects, shapes & basic forms

Associative agnosia

failure to link

perception with stored knowledge

Gestalt laws

The whole is greater than the sum of all its parts

1. Proximity

2. Similarity

3. Good Continuation

4. Closure

5. Common Fate

structuralism

We see whole objects

by combining elementary sensations

size constancy

Our perception of the size of objects is

relatively constant (& veridical) despite the fact

that the size of objects on the retina vary

greatly with distance.

• Our perception of size involves estimate of

distance

•When our perception of distance is erroneous,

size constancy breaks down

•This is illustrated in bad photography & in two

famous illusions, the moon illusion & the Ames

room illusion

what information can skin cells give us?

• nociception

• temperature

• pressure

What information active touch gives us

• texture

• size

• shape

• ??

what part of body has highest spatial resolution?

fingertips

Ian Waterman

• no proprioception head down

What do clinical cases suggest

about object & face recognition?

Separate stages of processing

(1) one in which we process the elements or parts

of an object

(2) one in which we process the whole structure

• First stage occurs in early visual processing

(occipital cortex)

Feature Detection Models

Selfridge (1959)

1. image demons. take in raw visual input

2. feature demons. detect specific components of visual information

3. cognitive demons. interpret signals and assign them meaning related to previous knowledge

4. decision demons. make final decision about what the stimulus is

What is colour for?

Scene Segmentation

camouflage

perceptual organisation

neuro-methods pros cons

CT, PET, MRI and fMRI: highest spatial, low temporal
EEG: high temporal, low spatial (lower than fMRI)

MEG: high temporal, good spatial (lower than fmri)

ERP: high temp, low spatial? (lower than fMRI)

TMS: high temp, high spatial, high interference

Pros of single-case methodology

allows for identification of the function of certain brain areas both through lesion and indepentently preserved areas

dual task paradigm

behavioral procedure in which subjects are required to perform two different tasks simultaneously.

AB on neural

Early Perception/Attention: (P1, N1) not modulated by reported visibilit

Categorization (N2) and Semantic Processing (N4) are linearly related to visibility

Working Memory update (N3, P3a,b) shows the “all-or-nothing” pattern of the AB, i.e. access to Global Workspace and awareness

Episodic buffer function

- Integrates information from PL and VSS into a coherent rich MULTIMODAL

representation.

- Includes “chunking” based on LTM (what forms a single entry in STM?).

- Accounts for awareness  Baddeley (2003): equivalent with the concept

of a GW for aware processing (e.g. Dehaene et al., 1998, 2003, 2006)

rao et al 1997

• Stimulus-specific neural populations in PFC = objects vs locations?

• BUT: neurons changed their response preferences when the task changed = can be easily “re-trained” Goes against innate, hard-wired preferences

Goldman-Rakic (1987; 1989), Fuster (1989)

: single cell recordings in monkey’s PFC

Goldman-Rakic (1996) argued for

• A division between the content of information

processed in dorsolateral and ventrolateral regions

D’Esposito et al., 2000

Dorsolateral: compensate capacity limitations during encoding, manipulation during delay, scanning memory during recall

ventrolaterall: PFC related to maintenance and to control of interference during recall

Petrides PFC and posterior

PFC: DLPFC - manipulate and monitor. VLPFC - maintain activity, retrieve info

posterior cortex: storage site of info

Tomita et al. (1999)

Top-down activation of object representations via PFC in

Tomita et al - conforming to Petrides’ view

• sever first POSTERIOR corpus callosum (still other pathways between hemispheres). cuts hemispherical visual processing

• patterns are activated top-down via the still intact connection between the two PFCs instead

• slightly slower than standard (bottom-up) processing found in posterior corpus callosum

• complete corpus callosum severing —) no PFC connection

top-down activity was what was activating it