Chapter 2 Flashcards
What is Capgras syndrome
A typical accompaniment to alzheimer’s but also results from brain injuries. The victim can recognize family and friends but believes they are imposters
What are the two systems involved in facial recognition, which is disrupted in Capgras syndrome?
- cognitive appraisal (recognition of physical features)
- Emotional appraisal (Sense of familiarity/warmth)
> the second is distrupted in Capgras syndrome
What brain areas have been shown to play a role in Capgras syndrome?
- MRI scans show damage in the right temporal lobe disrupting circuits involving the amygdala the “emotional evaluator” of the brain
- fMRI shows diminished activity in the right prefrontal cortex which is responsible for careful analysis. With diminished functioning it becomes hard to tell what’s real and what’s not
In what 3 circumstances is the prefrontal cortex less active
- Capgras syndrome
- Schizophenics experiencing hallucinations
- While dreaming
What are 3 functions of the amygdala?
- supports the feeling of familiarity
- helps people remember emotional events
- Helps in emotional decision making
What does capgras syndrome teach us about brain function
Even the simplest tasks involve the working together of multiple brain areas
What are commissures? what is the largest?
Thick bundles of fibers that carry information b/w the 2 hemispheres allowing integration
> Largest = Corpus Callosum
How does one become a split brain patient?
By severing the corpus callosum, thus having two intact halves that cannot communicate
What are the R and L hemispheres responsible for (in general)
L = language R = Spatial judgement
Define Neuropsychology and clinical neuropsychology
- study of the brain’s structures and how they relate to brain function
- Understanding undamaged brains by scrutinizing brain damage cases
Explain the experiment with the spoon and fork performed on split brain patients
The left side of the brain will see the fork on the R side of the body and be able to verbalize it. The Right side of the brain sees the spoon on the L side, cannot verbalize it but when reaching to pick it up selects the correct object
define lesion
specific area of damage
Describe how the CT scan functions
- Used to study structure
- Relatively stable results
- Relies on X-rays to create a 3D picture of the brain
- The map tells us the shape, size and position of sturctures
Describe how a PET scan functions
- Used to study brain activity
- Highly variable results
- involves introducing a tracer substance (glucose) tagged with radioactivity to track which tissues are using more glucose and are thus more active
- The maps shows which regions are active
Describe how MRI and fMRI differ
MRI: relies on magnetic properties of the atom in brain tissue to yield detailed pictures
fMRI: measures oxygen content in blood which provides precise pictures of the brains moment by moment activities
What are neurotransmitters?
Chemical signals neurons use to communicate
What are the 2 types of communication among neurons?
Between neuron - a neuron releases the transmitter and activates or de-activates neurons adjacent to it
Within neuron - Movement of the signal from a neuron’s input to it’s output via an electrical pulse made possible by the flow of charged atoms moving through the neurons
What is an EEG
Recording of voltage changes occurring at the scalp that reflect activity in the brain
What is a TMS
Creates strong magnetic pulses at specific location on the scalp to temporarily “turn off” a certain brain area in otherwise healthy patients
what is localization of function
Different portions of the brain all have their own jobs to do!
where are rodes and cones located on the eye and what are their functions
Cones - located most densely in the fovea allow for better acuity
Rods - Located more densely in the peripheries are light-sensitive and can see better in dim lighting
Once visual input hits the rods and cones where does it go next??
These photoreceptors stimulate bipolar cells which excite the ganglion cells whose axons converge and form the optic nerve which carries (and analyzes) the visual input through the lateral geniculate nucleus and finally to the occipital lobe
Explain single cell recording and what it tells us
An electrode is placed near a single neuron to observe how often it fires when viewing certain stimulus. This allows us to define the cell’s receptive field
What is a center-surround cell
A cell that fires maximally when the stimulus is in the centre of the receptive field and minimally when the stimulus is on the edge of the feild. When it’s on both the firing rate doesn’t change from it’s baseline level
What are “edge detector” cells
Cells that fire maximally to an edge of a specific orientation and the further the edge is from it’s preferred angle the weaker the firing of the cell
What are movement detector cells?
Fire maximally to movement in a certain direction
What type of processing does the visual system rely on?
Parallel processing - A system in which many different steps/ forms of analysis are occurring simultaneously
ex. Area MT is processing movement while V4 is processing color and shape
What is serial processing
steps are carried out one at a time
What are the advantages of parallel processing?
- speed
2. Mutual influence : each type of analysis can be informed by the other
Whats another example of parallel processing in the occipital cortex?
- P cells (input for LGN’s parvocellular cells and responsible fpr spatial analysis) and M cells (input for LGN’s magnocellular cells and responsible for movement and depth perception)
- Rods and cones
Describe the What and where systems/pathways
WHAT: travels from the occipital cortex to the temporal lobe and plays a role in identification of objects
WHERE: travels from the occipital cortex to the parietal cortex and guides our actions based on location of objects
What occurs when the What/Where pathways are damaged
WHAT (Ventral): visual agnosia - can’t identify an object but can reach for it
WHERE (Dorsal) : the opposite - they can identify but have trouble reaching
What is the binding problem?
The task of reuniting various elements of a scene that are initially processed by different brain areas so that we see a coherent whole.
how does spatial postioning solve the binding problem?
By overlaying spatial maps one over the other (color, shape, movement..)
How does neural synchrony solve the binding problem
rhythms caused by neural firing that sync up are registered as belonging to the same object
How does attention solve the binding problem
Attention is essential for synchrony of neurons to occur. When attention is focused elsewhere people mak conjunction errors likewise people with ADHD struggle with tasks requiring feature conjuction
What are the 3 components of visual perception
- Form perceptions (what is it)
- Depth perception (where)
- Motion perception (what is it doing)
What is edge enhancement?
- Occurs in a very early stage of visual processing.
- Caused by lateral inhibition - the cell on the edge of the lighter band fires more than the other cells in the white band because on one side it has the cell from the darker band which is firing slower and thus provides less inhibition. The edge cell on the darker side fires even less than all other dark cells because the bright edge cell beside it (as just mentioned) is firing higher than all other bright cells and thus inhibits the dark edge cell more.
