Imaging the Brain

Question 1

types of brain imaging

Answer 1

• Computerized Axial Tomography (CAT)
• Positron Emissions Tomography (PET)
• Magnetic Resonance Imagery (MRI)
• Functional MRI (fMRI)
• Diffusion Tensor Imaging (DTI)
• Transcranial Magnetic Stimulation

Question 2

traditional model of brain imaging

[not on study sheet]

Answer 2

1. Information flow is linear and unidirectional: Receptor—Sensation—Perception—Cognition—Action & Memory
2. Behavioral and mental functions are localized in discrete cortical areas
3. The system is organized hierarchically

• Basically: Afferent System (inputs), Efferent System (outputs), CNS mediates between them

Question 3

parallel distributed control models

[not on study sheet]

Answer 3

• Perception and Movement
• Interdependent subsystem: Perceptual modalities & motor systems
• Characterized by converging streams of information, parallel processing and multimodal inputs.

Question 4

what are focal lesions?

Answer 4

Infarct (dead brain tissue) of specific area typically caused by:

• Ischemic stroke (cascade of cell death following inadequate blood supply)
• Intracerebral hematoma (bleeding within cerebral regions)
• Penetrating head injury (bullets, tamping irons)
• neurosurgery
• viruses

Question 5

what is diffuse brain damage?

Answer 5

Broad effects implicating many brain areas (cortical and subcortical) caused by:

• Closed head injury
• Degenerative pathology (e.g., Alzheimer’s disease),
• Subarachnoid hemorrhage/Subdural hematoma
• Genetic Disorders

Question 6

behavioral consequenses of brain damage

Answer 6

• Deficit, dysfunction, symptom, impairment, disorder
• Syndrome: group of symptoms
• Labels: agnosia, apraxia, aphasia, agraphia

Question 7

localization of function:

double dissociation method

Answer 7

• Compare deficits that affect some functions and spare others
• Find contrasting pairs of patients with distinct lesions that show opposite pattern of disruption and sparing of function
• Conclude that distinct areas are localized for distinct functions
• Specific deficits might also co-occur with some kinds of damage and not others
• Problems in interpretation

Question 8

CAT scan

Answer 8

• Computer Tomography (CT)
• X-ray images of brain “slices” yielding images of gray and white matter and ventricles

Question 9

PET scan

Answer 9

• Positron Emission Tomography (PET)
• Regional Cerebral Blood Flow (rCBF)
• rCBF uses an inert radioactive element (Xenon is dissolved in the blood by being breathed in, or injection of heavy water)
• As the blood flow increases decreases, the radioactivity serves as a marker of the amount of the blood flow to different parts of the brain

Question 10

MRI

Answer 10

• Magnetic Resonance Imaging
• Signals how hydrogen atoms respond to perturbations of the magnetic field
• More detailed brain image

Question 11

fMRI

Answer 11

• Functional Magnetic Resonance Imaging
• Blood flow to regions of the brain compared during task vs. control condition

Question 12

DTI

Answer 12

• Diffusion Tensor Imaging
• Uses MRI technology
• Measures magnetic fields associated with diffusion of water along white matter tracts

Question 13

TMS

Answer 13

• Transcranial Magnetic Stimulation
• Intense, but focused magnetic fields can cause a population of neurons to discharge their action potential and may cause them to stop functioning temporarily
• Can create a virtual brain lesion