Workshops 1 - 5 Flashcards
In assessing a person’s state of mind, what does the term affect mean? (noun not verb)
A person’s emotional responsiveness
Define hallucination
False perception that occurs in the absence of a causative sensory stimulus yet is experienced as real. (Could be due to activity in temporal lobes)
Define delusion
A delusion is a firmly held belief that is false or bizarre with reference to a conventional view of reality.
Failure of reality testing refers to?
Abnormal mental processing leads to faulty perceptions and/or fixed ideas that are incorrect or bizarre – i.e. inconsistent with conventional reality.
There are three requirements for clinical diagnosis of schiz
1) Presence of some characteristic symptoms
2) Significant reduction in social or occupational functioning
3) Prolonged abnormality, that is active psychosis for at least 1 month and continuing disturbance for at least 6 months.
Thought disorder
Thoughts and conversation appear illogical and lacking in sequence and may be delusional or bizarre in content
Difference between second and third person auditory halluncinations
A second person verbal hallucination is the voice of some other person that addresses the subject as “you”.
A third person verbal hallucination is one or several voices that talk about the subject as “she” or “he”.
Do antipsychotics reduce positive or negative symptoms in schiz?
Positive - makes negative symptoms worse
*Curative not palliative
Fundamentally, MRI is based on “reading” a signal from each voxel, individually. What is the relationship between slices and voxels? What is the relationship between voxels and pixels in MRI?
Voxel - small cube of tissue (each pixel in 2D image is a visual rep of signal strength from corresponding voxel)
Slice - array of voxels
Pixels have one to one relationship with voxel (smaller the voxels = the better the resolution)
How does MRI work?
As H2 is paramagnetic, it’s like a spinning magnet. Due to the water, tissues have lots of protons spinning around with random orientation of the spin axis. Strong magnetic fields align the spin axes. Radiowaves disrupt this alignment, when they re-align, they give off radio waves. Hence, MRIs measure radio waves (harmless) and hence water in brain hence grey & white matter is different as there is a difference in water distribution.
How does fMRI work?
BOLD - blood oxygen level dependent - exploiting haemoglobin (paramagnetic) where properties differ whether its bound to O2 or not. Increased oxy-Hb = increased MR signal
*BOLD effect is 4 to 5 secs after onset of neural activity
Approximately, what is the best possible temporal resolution with any type of current brain MRI?
Under 1 second
With any form of brain MRI, we generally lose spatial resolution if we improve temporal resolution, or vice versa. Explain why this is. Voxel size is important for this. Which resolution requires many small voxels? Which resolution is favoured by fewer, larger voxels?
Good spatial resolution needs to be done as long as possible where else good temporal resolution needs to be done ASAP
Small voxels = spatial
Large voxels = temporal
List some strategies for reducing image acquisition time to improve temporal resolution in fMRI.
- Limit scanning to regions of interest (less slices with fewer voxels)
- Larger voxels – again fewer voxels, and also each one is easier to scan. This sacrifices a detailed view for a quick view.
- Using a quicker pulse sequence (each voxel requires at least one BOLD-suitable pulse sequence).
- Optimising the electronics and software for imaging and data processing.
T/F: fMRI can capture a single thought
F
Do BOLD signals require small or large voxels?
Voxel must be large enough to contain some capillaries and enough tissue to drive blood flow changes.
Is the temporal resolution of the fMRI similar to that of ERP-mapping
No - ERP is faster (< 1 ms)
Which commissure connecting the two hemispheres is responsible for sharing images between hemispheres? What other routes are there?
Corpus callosum
Cerebellum, Brainstem, Spinal cord, the other commissures (Ant, post, hippocampal, habenula)
Consider a scenario where the written word “bell” is presented visually to the right hemisphere, and the written word “music” is presented visually to the left hemisphere. What would be the likely response if the person was asked “what word did you see?” Also, what would be the likely response if that person was instead asked to point, with their left hand, to an image that represents the word they saw?
They would respond to the verbal question with “music”; they would point to the image of a bell when asked to indicate which image best represents the word they saw.
Wernike’s aphasia
Receptive aphasia (fluent aphasia) - Damage PSTG = X sensory area = X Inability to understand language (written or spoken) *Patient unaware of problem *Wernicke's like What? Wernicke's is all confused. Makes Word salads for a living.
Broca’s aphasia
Expressive aphasia - Damage frontal lobe = X motor area = X speech production area
- Patients have insight to their problem and are frustrated
- Broca is broke - speaks broken words - frustrated because he is broke
In reading, would you expect the phonological strategy to be faster than lexical word recognition, or vice versa? Explain why.
The lexical pathway would be expected to be faster, as it takes in the word in one hit, rather than deconstructing it to graphemes and then phonemes, before running through the speech pathways using your internal voice.
Why does it take longer to identify pseudo-words compared to real words when we are presented to them?
Reaction time is consistently lower for words v. nonwords. This may be due to the need to run through every possible word (or word structures) in the lexicon to ensure it is not an English word, while English words may be confirmed before the whole lexicon is searched. The latter will, on average, be quicker.
*An alternative explanation for the slowness to recognise nonsense words is that nonsense words will have to analysed phonologically as they are all by definition unfamiliar. The need to use the slower phonological route may explain some of the difference in reaction time.
Explain what you think “priming” is
Priming is thought to subliminally activate the language pathways. In doing so, it is thought to activate all words associated with the prime. All possible associations seem to be primed, including synonyms, antonyms, homophones, semantically related words and words that often occur together
She reports seeing “furry white walls”, “moving pink squares”, and “snakes coming out of the ground”. Can you relate each of these to a particular level of the visual hierarchy?
V2 – low level visual features like texture, colour, shapes
The mixture of motion is probably just overactivity in the dorsal stream of the visual processing that is getting incorporated into the picture too
Why are hidden objects (face in coffee bean) so hard to see?
Visual processing is aided by conscious expectation and when the brain is forced to work with incomplete data, it needs time to extract an explanation that makes sense. Once you know what you are looking for, it becomes easier and quicker.
Colour spreading phenomenon
2 errors:
- Illusory contour defining a circular shape
- Misplacement of colour information that gives the illusory shape a ghostly colour.
Perhaps the subsystem trying to recognise a circle somehow exaggerates / extends colour perception to help it define the shape.
2-D cubes have same coloured surface but looks to be different colours in alternating rows- why?
The illusory difference in luminance between alternate rows of cube top/bottom surfaces is primarily due to the fact the retina detects relative contrast (centre-surround organisation).. It is probably exaggerated perceptually (in visual cortex) because it supports a 3D interpretation.
Similar texture is grouped as one item
Similar texture is grouped as one item
Charles Bonnet syndrome
Visual hallucinations are vividly conscious visual perceptions occurring when there is little or no damage to V1. They correspond to abnormal cortical processing, probably hyperactivity or sensitisation of V1 cortex or other visual cortical regions. Typically, V1 is deprived of normal inputs because the retinas are damaged.
