Module 2 - Perception and Neurophysiology Flashcards
Sensation
receiving sensosy information from the environment
Perception
the interpretation of the information, assigning the information a meaning
How do we determine colours?
colours are determined by the different wavelength of light
- long nm = red
- short nm = blue
How do we determined if the colour is dull or bright?
The amplitude of the wavelength determines whether the colour is dull or dark
- longer wavelength means the brighter the colour
Cornea (outer layer)
Transparent layer in front of the eyes that bulges out
What is the process cornea is involved?
this structure of the eyes is involved in focusing an image
- an image falls in the back of the eyes, into the photoreceptors and triggering them (wants image to be as focus as possible)
Choroid (middle layer)
a structure in the eyes filled of blood vessels that bring oxygen and nutrients to the eyes
How does the choroid structure function?
this structure runs not around but covers the part where the cornea will not be disrupted
- so main purpose of the choroid structure is that blood vessels in here provides nutrients to the eyes and generates waste (not in cornea)
As there are no choroid structure in the cornea; How does cornea get nutrients and blood supply without disruption of visual?
There is a structure behind the cornea called the ANTERIOR CHAMBER which is a clear fluid that functions like blood as its function is to provide nutrients to the cornea to keep it alive and as well as generating waste
Vitreous humor (inner layer)
the inside chamber of the eyes that gives it shape
What is the purpose of vitreous humor?
it provide nutrients to all parts of the brain that the choroid does not reach
Iris (inner layer)
a muscle which controls the pupil and is the colours we see in the eyes
- so when the pupil is dilated more light gets into the eyes and if pupils are constricted less light gets into the eyes
Lens (inner layer)
behind the iris, this is attached to muscles which is a structure that changes it shape through engaging in the process called ACCOMODATION
Accomodation
the process where the lens changes it shapes to allow the focusing of objects near and object far
Critical period
the maximum amount of time to recover from the loss of a sensory system
- if defects not fixed by critical period, it will not be able to reverse action
e.g. congenital cataract
Retina
sheets of cells, these are the photoreceptors (rods and cones)
Bipolar cells
are one of the main retinal interneurons and provides the main pathways from photoreceptors to ganglion cells
i.e. the shortest and most direct pathways between the input and output of visual signals in retina
What happens if cortex is damaged?
when cortex is damaged, it causes less catastrophic impairment that are far more mysterious
e.g. people with damage in cortical vision
What happens if subcortex is damaged?
when part of the subcortex is damaged, the impairment are catastrophic but not mysterious
e.g. damage certain areas of subcortex can cause blindness
Dorsal stream
WHERE is the dorsal pathway which goes into the parietal lobe (important for knowing where an object is in space)
Ventral stream
WHAT is the ventral pathway which goes into the temporal lobe (important for knowing what the object is)
What system is the retinal ganglion associated with?
associated with both ventral and dorsal systems
Receptive field
the area of the retina which when stimulated by light causes a change in the neural activity of the cell
lateral inhibition
the capacity of excited neurons to reduce the activity of their neighbours (inhibits about 10% firing rate)
Right monocular blindness (right eye blind)
this condition occurs if damaged is in the optic nerve that is coming out from the right side of the eyes
Bitemporal hemianopia (loss both temporal visual field - half vision for both eyes)
this condition occurs if damage is in the crossing fibre (optic chiasm)
Left homonymous hemianopia (both left fields (no vision) are half vision)
this condition occurs if damage occurs after the optic chiasm of the right eyes, this causes blindness on the left visual field of both the left and right eyes
- a cut after the optic chiasm and up to the primary visual cortex
- V1 damaged could also results in left homonymous hemianopia (macular sparing)
What happens if damaged occurs in the primary visual cortex
It leads to a condition called blindsight
Achromatopsia
absence of colour vision due to damaged in V4
- people with this condition have their visual processing intact, but its just they see the world in shades of grey
Akinetopsia
absence of motion vision due to damaged in V5
- people with this condition struggle to process information when this visual information is set into motion
e.g. struggle to fill a glass of water
Visual agnosia
a loss in ability to describe an object yet have perfectly normal vision and be able to see anything normal
Apperceptive agnosia (peppery mask)
struggle to tell what the object is; failure in object recognition but due to profound visual perception problem (have preserved elementary functions; can see motions, colour but ability to see shapes is severely limited
Effect of damage in V1 to apperceptive agnosia?
damaged in V1 in this condition is caused by carbon monoxide poisoning where it creates lots of little pockets all over V1 this results in many blind spots in the real world; these blind spots are called SCOTOMA
What conditions are caused when damage in V1 occurs?
blindsight and apperceptive agnosia
what effect does having multiple scotoma?
multiple scotoma are seen as visual field impairment, which prevents a person from seeing what really the abject is due to the many blind spots in the visual (peppery mask)
Dorsal simultagonasia
can only perceive one object at a time, may experience difficulties in recognising and processing the overall scene or configuration of the object
- can identify all the object, but are unable to perceive the event of the photo as a whole
What is the effect of dorsal simltagnosia?
Patients can only recognize one object at a time as there is only one object visible among all the different objects
- they have difficulty in shifting attention from object to object
Ventral simultagnosia
a form of agnosia due to damage a little beyond V1, does not have as profound as perceptual impairment as someone who suffers from apperceptive agnosia
What area of the brain does dorsal simultagnosia and ventral simultagnosia occurs?
- a lesion to the occipital and or parietal lobe caused dorsal simultagnosia
- a lesion to the left temporal-occipital region caused ventral simultagnosia
What is the effect of ventral simultagnosia
Patients can only recognize one object but multiple objects is visible to visual
- the objects are in the right spatial position, it’s just that there are many other objects in the photo (one object is in focus mode while the rest is blurred)
Associative agnosia
a failure in object recognition due to higher order complex perceptual impairment
- this occurs in the far reach of the ventral stream (last processing of the area of the brain)
What is the effect of associative agnosia?
People who suffers from this condition looks like perception is intact but it isn’t
- e.g. when people who suffered this condition, was assigned a task of drawing something, they were constantly looking back and forth at the photo given and copying it detail by detail (obviously not normal)
Differentiate between top-down and bottom-up theories
In the bottom up processing , we allow the stimulus itself shape our perception, without any preconceive ideas whereas in the top down processing, we use our background knowledge and expectation to interpret what we see
Difference between monocular cues and binocular cues
Monocular cues operate when a person is looking with only one eye whereas binocular cues operates when both our eyes are working together
Retinal disparity
the fact that the left and right fields of vision will provide a slightly different visual images when focusing on a single object
Differentiate between divergence and convergence
Divergence means that there are two things moving apart whereas convergence implies that two forces are moving together
What are the six types of monucular cues
1) Interposition
2) relative size
3) linear perspective
4) low angles
5) texture gradient
6) light and shadows
Young-Helmholtz Trichromatic Theory
there are three types of cones in the eyes that are each maximally sensitive to a certain wavelength of light
Opponent-Process Theory
this theory suggest that looking at one colour for a long period causes those receptors cells to become fatigued. When they begin sending weaker signal, their opposing cells fire, sending signals that cause the perception of the opposing colour
Pineal gland
a peas size structure that is situated in between of the two massive hemisphere (left and right)
- called “sea of the soul” (Rene Descartes)
Phrenology
the idea of this is correlating a bumps and depression with certain faculties
- so if an area of the skull have a bump then there must be a well developed structure under there making you excel in a certain aspect
Broca’s aphasia
a problem with the motor aspect of speech caused by damaged in the left frontal lobe
- the problem is not in speech but in speaking (can understand what is being told but cannot speak a full sentence-only words)
Wernicke’s aphasia
this is often cause by damaged in the left temporal lobe
- people with this condition can speak normally but they have problem in comprehension of speech (will struggle in answering questions as they haven’t understood it yet)
What lobe of the brain is not multifunctional?
the occipital lobe
- this part of the brain is dedicated to only one sensory system which is visual
What conditions is caused if damage occurs in the occipital lobe?
1) blindness and blindsight: patients are unable to tell you what something is but can tell you where it is
2) apperceptive agnosia: if caused by carbon monoxide, this is difficulty in perceiving objects and naming objects
Middle and inferior gyrus (lateral surface of brain)
associated with the visual ventral stream (all visuals)
Superior gyrus (lateral surface of brain)
associated with the auditory cortical centre of the brain (all auditory)
Medial temporal lobe
a cortical tissue that has been wrapped up inside the brain which structure includes the hippocampus, amygdala and parahippocampal regions
- crucial for episodic and spatial memory
Effects of damage in the medial temporal lobe
- causes memory impairment
- damage to the right parietal lobe will cause memory impairments, the information contained is much less in right lobe lesions
- damage in left parietal lobe will cause less response into the visual memory impairment
Agraphia
damage in the left parietal lobe which is difficulty in writing (cannot organize information in a page)
Acalculia
damage in the left parietal lobe which is difficulty in math (unable to organise information spatially; they know the value of multiplying each of the individual numbers but they are unable to put these numbers in the right place)
Contralateral neglect
damage in the right parietal lobe, which in this case patients tend to neglect the left area (only able to identify the right side)
Ego-centered neglect
the idea is when looking at something, the body axis is imposed in the middle, there is a right side and a left side in the object we are looking
Object-centered neglect
Doesn’t matter where the body axis, not just the body axis but the figure itself, neglect the left hands side of the figure and seethe sight hand side of the figure
Four regions of the Frontal lobe
1) right and front of the lateral sulcus = motor cortex
2) pre motor cortex
3) prefrontal cortex
4) orbitofrontal cortex
Damage in the motor and pre motor cortex
causes impairment in motor functions
e.g. broca’s aphasia (caused as damaged is located in the front premotor cortex)
Imitation behaviour
patients with damage in frontal lobe tend to imitate more compare to patients with no damage in the frontal lobe
Utilization behaviour
patients with damaged in the frontal lobe has an incredible need to use something for it’s intended purpose even though it’s not required for them to do so
Why do we get deficits when we have damage in one area of the sensory system?
within the sensory system it is modular
e.g. Visual system
-you might be able to identify an object but not when it is moving
Does the visual system do just perception or sensation or both?
the visual area do all sensation and perception, it is just that earlier in the visual system there is more sensation and later in the visual system there is more perception
object discrimination
a simple task to train monkeys to play a game, so in the task there was two stimulus and within this the monkey had to find which object hides under the snack
landmark discrimination
addition of landmark into the object discrimination task
Double dissociation
when you damage the temporal lobe, you impair the object task but the spatial task is fine, but when you impair the parietal lobe it wipes out the spatial task and the object discrimination is fine
Results of the double dissociation effect for the monkeys?
the result was opposite, for the monkeys that had parietal lobe lesions, when they place into the landmark discrimination task they had no idea what to do but when they were place back into the object discrimination they performed the task very well
What does the double dissociation indicates?
it indicates that there is two visual pathways
- “WHERE” is the dorsal stream pathway
- “WHAT” is the ventral stream pathway
What affect rods and cones
it is sensitive to changes in illumination
- when it senses illumination it gets trigerred
Retinotopic Mapping
The visual world is mapped into the retina
- there is no retinotopic mapping after V1
Mishkin and Ungerleider (1982)
completed an experiment with monkeys where they were tested on both object discrimination and landmark discrimination
Effects on Damage to the superior temporal gyrus (auditory region of the brain)
- deafness
- wernicke’s aphasia
- auditory agnosia
Effects of Damage to the middle and inferior temporal gyrus
- Achromatopsia
- Akinetopsia
- Ventral Simultagnosia
- Associative Agnosia
Effect of Damage to the left medial temporal lobe
verbal memory impaired
- classic double dissociation
Effects on damage in the left parietal lobe
- agraphia
- acalculia
- dyslexia
- difficulty in drawing (details)
Effects on damage in the right parietal lobe
- contralateral neglect
- difficulty in drawing (overall shape)
- difficulty in recognizing unfamiliar views of objects
Effects on Damage in the frontal lobe
- impairment in IQ
- Impairments in motor function
- Loss of divergent thinking
- impairments in response inhibition
- environmental dependency syndrome
- changes in personality
Wisconsin Card Sorting Test
a powerful indicator as to whether you have sustained damaged to the frontal lobe of the brain
Stroop interference test
a test for impairment in response inhibition
- if an individual has a frontal lobe damage they will struggle to inhibit something
