Brain Sates
o What is the lifetime risk of schizophrenia?
.7%
What is the amount of external information constituting conscious perception (in bits/sec)? If your computer operated on this bandwidth, how long would it take to download a small (e.g., 200 KB) picture? (1 byte = 8 bits)
100 bits per second 4 hours and 44 min
o What measures can one use to describe a dysfunctional brain organization? The author mentions five of them. Don't memorize the list, but be able to recognize and explain each of the measures.
Abnormal small world architecture Dysfunctional subdivisions: are you having primary sensory problems, sub-cortical, limbic Compensatory subsystems identification of dysfunctional hubs disease identification, onset and progression
What is the DMN, functionally and anatomically?
Acts as the brains conductor ensuring all brain regions are ready to react to stimuli Medial prefrontal cortex, medial parietal cortex, lateral temporal cortex, lateral parietal cortex
o How is the DMN affected by natural aging and Alzheimer's disease?
Alzheimer's seems to target DMN regions and people over 60 show a reduction DMN pattern
What brain disorders can be better understood by considering the DMN?
Alzheimer's: DMN areas tend to atrophy with the development of the disease Depression: DMN areas seem to be disconnected with areas involved in emotion
o What are the three core neurocognitive networks (according to Vinod Menon)? What brain structures are they anchored in?
Central Executive Network: frontal parietal system anchored in the dlPFC and posterier parietal cortex DMN: anchord in the posterior cingulate cortex and mPFC Salience Network: dorsal anterior cingulate cortex and fronto insular cortex
o Shine et al. (2014) and Menon (2011) refer to three brain networks. They use some different names, but these networks are essentially the same. Pair them up ({SN, CEN, DMN} and {VAN, DAN, DMN}) and decide which nomenclature you like better. Use it.
DAN=CEN SN=VAN
o Which of the three networks may act as a switch for the other two?
DMN
o What is the small-world architecture? Is it present in the brain? How about social networks?
Dense local clustering connections between neighboring nodes and short path length between nodes
What are the slow cortical potentials (SCPs) and how do they compare to the heartbeat?
Groups of neurons that fire approx every 10 sec similar to heart rate. ensures that the right computations occur at the right time. different brain areas have different SCP which are overseen by the DMN
o What is the hypothesized role of SCP-phase resetting? Notice "Bayesian" between the lines
Helps match predictions to changing environmental contingencies
o What is graph theory?
In a graphical representation of a brain network a node corresponds to a brain region whereas an edge corresponds to the functional interactions between two brain regions
o What are the "hierarchy of prediction" and the "propagation of prediction errors"? Be able to explain Figure 3. What kind of updating do these errors cause, and why can this ultimately lead to delusions?
Miller86 discussed the process of delusion formation in terms of an increased willingness to see meaningful associations in the world, whereas Gray, Hemsley and others suggested that the key problem is a diminished ability to integrate new experiences with stored knowledge based on previous experiences87. In either case, a consequence might be the development of strange conclusions on the basis of evidence or experience that supported these conclusions only very weakly
o When is the brain physiologically at rest
Never. Resting state is defined as being awake while resting eyes or fixating at a neutral stimuli
o Is it correct to say that the brain constructs reality strictly from the bottom up? What does it mean?
No, not from the bottom up. This means we process everything we see which would take too long
What was the discovery made by Dr. Michael Greicius and colleagues? What is the anatomical relationship between the posterior cingulate cortex (Figure 2(a)) and the medial parietal cortex
Noise in BOLD responses have striking pattern of coherence Found pattern of coherence in the DMN elicited by placing a region of interest either in the posterior cingulate cortex or vmPFC brain areas are widely seperated
o How is perception affected by the absence of perceived control?
People become susceptible to detecting patterns in an effort to regain some sense of control
o Does the DMN spatial coherence disappear in sleep or under anesthesia? Has the DMN been discovered in other species?
Present during sleep and found in other species
What are the two views of brain function?
Reflexive view Intrinsic view
o Which of the three networks is closely associated with the amygdala, the substantia nigra, and the ventral tegmental area (VTA)?
Salience network
o Which of the three networks is involved in the processing of pain and the empathy for pain?
Salience network
o What are the slow cortical potentials (SCPs) and what are their frequencies? What is their relationship to the fMRI (BOLD) signal?
Slow event related, direct current shifts in EEG, orienting from large cell assemblies in the upper cortical layer (300 milliseconds to several seconds Spontaneous fluctuations in BOLD are correlated with SCP
o According to Dr. Marcus Raichle, is the brain hierarchically organized? If so, what is at the top of the pyramid?
The DMN
o According to "major class of theories," what is the primary cause of positive symptoms?
The primary cause of positive symptoms is abnormal sensory experiences and delusions follow as a consequence of attempts to understand the sensory experience
o What is the location of neurons which, when silenced, blur the line between the self and the rest of the world?
a bundle of neurons in the superior parietal lobe
o How much more energy does the brain typically consume in response to task-related activities?
brain uses 20% of the body's energy and is 2% of the body additional energy from changes in brain activity is less than 5%
o What is unique about the insula from the network perspective? Where is it located?
co activated with the Anterior cingulate cortex, parietal cingulate cortex and vlPFC identifies the most homeostatic-ally relevant among several internal and extra-personal stimuli to guide behavior
How does the rising phase of an SCP control the strength (amplitude) of higher frequencies?
electrical activity at frequencies above that of the SCP's synchronize with the oscillations of phases of the SCP's
o Match the following: {expected, unpredictable} and {high DMN activity, low DMN activity}.
expected: high DMN activity unpredictable: low DMN activity
o How does increased dopamine activity (in the substantia nigra → ventral striatum pathway) affect learning from gains and losses? Why can this affect Prob(O)?
increases rate of learning from gains but not losses
o What are the nodes and edges in a brain network? (In graph theory, nodes can also be called vertices.)
node=brain region edges= functional interactions between two brain regions
o What are the hypothesized effects of the VAN being overactive
overactive VAN would misinterpret and over-ascribe salience to miss perceived stimulus
o How are the phenomena of "latent inhibition" and "blocking" affected in schizophrenia? What does it have to do with Bayesian inference?
patients learn more rapidly than control subjects in response to stimuli they have previously been exposed to there is a partial loss of blocking in people with schizophrenia and people on amphetamines
o What is the recent paradigm shift in the study of brain dysfunction? (Don't itemize; extract the main idea.)
research into how multiple brain regions interact with one another over time rather than singling out areas
o How do the rising and falling phases of the DMN affect the power (amplitude) of the higher frequencies (Fig. 4)?
rising phase: amplitude increases initially and the decreases falling phase: amplitude continues to decrease but increases toward the end
o What is the traditional experimental approach to brain activity? Why can it be misleading?
traditional studies are task-evoked responses encouraging a reflexive view of brain function
o What are the hypothesized effects of the DAN being underactive? Where does the DMN fit in this picture?
under active DAN leads to over reliance on other attention networks like the DMN to interpret ambiguous stimuli
o Do invertebrates use reality models to guide their behavior?
yes
o Is the DMN unique in its organized functional activity in the resting state?
yes, typically brain areas' activity decreases during the resting state
