Cerebral cortex- The outer covering of the forebrain. Divides into lopes that provides different functions.
Four lobes:
1. Occipital- rear of the head. Provides vision.
2. Temporal- locate toward left/right side of head. Purpose hearing and slight vision.
3. Parietal- forward from occipital lope. Specialize for body senses.
4. Frontal- forward pole of the brain. Control fine movement.
Sensory:
A. Primary visual- vision
B. Somatosensory- strip in anterior portion of parietal lope. Touch in different body areas.
C. Auditory cortexes- hearing
Motor:
A. Prefrontal cortex- anterior section of frontal lope. Important for memory.
B. Primary motor cortex- controlling fine movement
-Amygdala- structure in the lope responds to emotional situation.
Huettel, Song, McCarthy (FMRI): What is fMRI? What is it used for? What does fMRI measure?
What is the central principle in measuring active and non-active brain regions?
-fMRI is a brain imaging technique that uses standard magnetic resonance imaging to measure changes in the brain over time (active function vs static)
- fMRI measures a correlate of a correlate (it measures the presence of deoxygenated hemoglobin, which is
a correlate of blood flow, which is a correlate of neural activity
Functional contrast, which is based on total deoxygenated hemoglobin the blood, and the magnitude of the change in deoxygenated hemoglobin is what distinguishes between active and non-active brain regions.
What are some of the criteria used to evaluate the appropriateness of any imaging technique?
1) What quantity does it measure?
2) How
sensitively can it measure that quantity?
3) How precisely in space does it measure that quantity?
4) How often can it make the measurement?
Define PET
- Positron Emission Tomography
- Creates images based on the movement of injected radioactive material
Define TMS
- Transcranial Magnetic Stimulation
- A technique
for temporarily stimulating a brain region to disrupt its function.
-Uses an electromagnetic coil placed close to the scalp; when current passes through the coil, it generates a magnetic field in the nearby brain tissue, producing localized electric currents
Define EEG
- Electroencephalography
- Measure of electrical potential of the brain, usually through electrodes placed on the surface of the
scalp.
Define MEG.
- Magnetoencephalography
- A noninvasive functional neuroimaging technique that measures very small changes in magnetic fields caused by the electrical activity of neurons, with potentially high spatial and temporal resolution.
What is contrast-to-noise ratio?
Magnitude of the intensity difference between different quantities divided by the variability in their measurements
important things to remember about BOLD
- There are TWO general ways of measuring neuronal activity (direct (electric potentials, chemical gradients) or via correlates (blood flow))
- BOLD Contrast is the basis for nearly all fMRI studies
- Spatial and temporal resolutions for fMRI are important to the ability to use it: Spatial (ability
to distinguish changes across spatial locations) = extremely good, Temporal (ability to distinguish changes in an image across time) = rather poor because hemodynamic responses are slow
Huettel, Song, McCarthy (FMRI): Functional neuroimaging methods measure what? Be very specific. Do they measure neuronal activity?
Functional neuroimaging methods do not directly measure neuronal activity. They use the fact that the presence of glucose and oxygen
is related to blood flow which is correlated with neuronal activity in order to obtain measurements.
Functional neuroimaging methods do not directly measure neuronal activity. They use the fact that the presence of glucose and oxygen is related to blood flow which is correlated with neuronal activity in order to obtain measurements.
Define BOLD fMRI, oxygenated and deoxygenated hemoglobin, diamagnetic and paramagnetic
- BOLD fMRI is fMRI that uses deoxygenated hemoglobin presence to create images. BOLD contrast is what allows this image to be developed.
Oxygenated = diamagnetic (weak repulsion from magnetic field) bc of paired e
Deoxygenated = paramagnetic (strong attraction to the magnetic field) bc of unpaired e
Define proton density
Weighted imaging type that is dependent on density of proteins
T1 vs T2, T2* contrast images
T1: Static imaging, image based on T1 time constant, repetition and echo times used to develop the image are short (fluid = black, gray matter = dark gray, white matter = light gray)
T2: Static imaging, image based on T2 time constant, repetition and echo times are long (fluid = bright, gray matter = light, white matter = dark)
T2: Used in fMRI, based on T2 time constant
Explain the following paradox, the MR signal increases during neuronal activity even though hemoglobin decreases MR signal.
Even though hemoglobin decreases MR signal, there is an excess amount of oxygen that is delivered to the brain that needs to be consumed. This oxygen displaces the deoxygenated hemoglobin during neuronal activity, which causes the signal to increase.
Fox, Raichle et al. argue that cerebral metabolic rate for oxygen (oxygen consumption) and cerebral metabolic rate for glucose (glucose metabolism) are uncoupled. What does this mean? What causes the uncoupling?
- Rates of consumption are not proportional since glucose is metabolized non-oxidatively.- Recent experiments are showing that it may actually be due to "superfluous perfusion of oxygenated
blood without a concomitant metabolic need."- Furthermore, recoupling can happen as stimulation continues
Huettel, Song, McCarthy
Explain the balloon model and its relationship to the initial dip found in some fMRI experiments. (what is initial dip, what is balloon model, explain relation)
- Initial dip: short term decrease in MR signal immediately following the onset of neuronal activity before the main positive component of the hemodynamic response. It can result from initial oxygen extraction before the later overcompensatory response.- Balloon model: model of the interaction between changes in blood volume and changes in blood flow associated with neuronal activity.- The initial dip is a result of greater blood flow flushing deoxygenated hemoglobin from the capillaries into the veins at a faster inflow than outflow rate, so there is a temporary decrease in MR signal.
What are some of the problems associated with relating neuronal activity and HDR?
- HDR = hemodynamic response- slow response timings and lack of precision (possible presence of false positives)- indirect measurement
What is the difference between modular vs. multimodal views of language and brain?
Modular views of language and the brain basically state that there are specific regions that do specific things (based on the classical model), but we know that multimodality is what is actually true for the brain. It means that each brain structure does many things, viewing language as not a monolith
In the context of the Gallese and Lakoff article, it states that conceptual knowledge is embodied, or mapped, within our sensory-motor system, however, sensory-motor brain mechanisms can adapt and serve new roles in reason and language while retaining older function, which is an example of multimodality.
What are the strengths of the Gallese/Lakoff article? How do they move the conversation forward?
- They acknowledge that language is multimodal, especially through talking about mirror neurons, however it poses the question about the localization of concepts in our sensory-motor system.- They also use various types of research to back up their findings (brain imaging, physical results)
Peirce vs. Gallese/Lakoff on the definition of "symbol"
Peirce defines symbol as the relationship between the sign and the signifier. Gallese/Lakoff define symbol as something that represents a real-life occurrence or something that exists in real life, as opposed to an abstract concept like "love" or "justice"
Mirror neurons in Gallese/Lakoff
A mirror neuron is a neuron that fires both when someone acts and when they observe the action completed by another.- Gallese/Lakoff --> mirror neurons are inherently multimodal because they respond to both seeing and performing
Define aphasia.
Loss of linguistic faculty as a consequence of a cerebral lesion
What is logorrhea?
Pathologically excessive talkativeness
What are the implications of a multimodal modeling system of language in the human brain?
Difficult to localize function, can't categorize brain structures
Causes of aphasia
Cranial trauma, infection, tumor, cerebral infarction (damage to brain as a result of interruption of blood supply), hemorrhage
Bucholtz and Hall: How do they define semiotics and what are the four semiotic processes that are so important to the construction of identity
practice, indexicality, ideology, performance
Bucholtz/Hall on identity
identities are attributes of situations and actions, not attributes of groups or individuals. The are emergent properties
Marked vs nonmarkedness
general and specific markedness: statement of A
general and specific unmarkeness: non-statement of A, statement of nonA
Gellatly: is all human perception mediated by language?
The spontaneous activities of looking, listening, and touching, together with the satisfaction of noticing, can proceed with or without language.
Do different languages pose different challenges for cognition and provide differential support to cognition?
According to the third phase studies, perception of color is subject to subtle cognitive influences. Ways in which color is labelled can affect how they are categorized, supporting the Sapir-Whorf theory of linguistic relativism. Differences in these color lexicons are influence because individuals exploit those differences and language predisposes rather than determines. Thus, different languages pose different challenges for cognition because of the Whorfian hypothesis as a psychological hypothesis about language performance, not language competence
Is there a culture that has a more "natural, unmediated experience of the world?"
Whorf conceived of an asymmetry between SAE speakers and members of 'other' cultures that enjoy a more natural, unmediated experience of the world, such as with spatial mediation of linguistic concepts versus direct experience of time.
1. Functional neuroimaging methods measure what? Be very specific. Do they measure neuronal activity?
2. Define BOLD fMRI, oxygenated and deoxygenated hemoglobin, diamagnetic and paramagnetic. Explain their relevance to BOLD fMRI.
3. The relationship between blood flow, glucose consumption and oxygen utilization are crucial to understanding BOLD contrast fMRI. Explain the following paradox: the MR signal increases during neuronal activity even though deoxygenated hemoglobin decreases MR signal.
initial dip
1. fMRI methods measure correlates of correlates (dHb, which is a correlate of blood flow, which is a correlate of neural activity)
2. BOLD fMRI: uses BOLD imaging and deoxygenated hemoglobin flow to create images. Oxygenated hemoglobin is diamagnetic (paired e-s) and deoxygenated hemoglobin is paramagnetic (unpaired e-s)
3. An excess amount of oxygen is delivered to the brain that needs to be consumed. This oxygenated hemoglobin replaces the dHb during neuronal activity, causing the signal to increase
- The initial dip is a result of greater blood flow flushing deoxygenated hemoglobin from the capillaries into the veins at a faster inflow than outflow rate, so there is a temporary decrease in MR signal.