Methods and Neuroanatomy Flashcards
What is Parallel Processing
Assumes some or all processes involved in cognitive tasks occur at the same time.
eg; skilled typest can think a few letters ahead, whereas novice focuses on one letter at a time.
Hierarchical organization
Memory viewed as a hierarchy with many component processes/systems
eg; explicit memory can be divided into episodic and semantic.
Episodic Memory (explicit memory)
remembering an experience in life including time and place
Semantic Memory (explicit memory)
Factual knowledge
Context effects
prior knowledge or experience influences new knowledge.
Cognitive Neuroscience
Study of all mental functions that are linked to neural processes and how those functions are organized in the brain to guide specific cognitive operations.
Lesion-Deficit Approach
Damage to a particular brain region results in an inability to perform a given task. Brain region assumed to be involved in task function.
Modularity
Isolated properties or modules that work independently as cognitive functions. Specialized processes.
Example; facial recognition may include semantic information which is separate than the perceptual component of the face.
Brain Damage
May impair only a small fraction of the total number of modules (ideally it impairs only one)
Encapsulated, automatic Perceptual Input Module
Unable to communicate with one another, and cannot be controlled by conceptual processes and unable to consciously reflect.
Central, conceptual processes Unencapsulated, controlled
Open to other modules and conscious awareness, controlled
eg; conductor of an orchestra; combining information
governs a wide variety of cognitive functions (reasoning, attention)
Lesion-Deficit Transparency
careful analysis of the pattern of intact and impaired performance will lead us to valid conclusions about the nature and function of the impaired module/modules.
difficult to infer on a single patient and a group to a particular region cause there may be other reasons why.
Single Dissociation
Lesion to Region A causes a disruption in Function A but not in Function B
Inference; Region A mediates performance on task A but not task B
Does not rule out other interpretations.
Double-Dissociation
Lesion to Region A causes a disruption in Function A but not in Function B, whereas lesion to Region B causes a disruption in Function B, but not in Function A.
Inference: Functions are independent because the viability of one cognitive function does not depend on the viability of other cognitive function.
Diaschisis Effect
altered functioning in intact tissue that is functionally connected to a damaged region.
Module A is damaged and Module B cannot function properly without Module A
K.C Case Study
Motorcycle accident:
bilateral hippocampal damage from head injury
preserved iq, perception, language, exeuctive function
preserved remote semantic memory
Impaired episodic memory for all times in his life.
H.C Case Study
Impaired autobiographical episodic memory despite more selective hippocampal system volume loss.
Structural MRI
Imaging individual slices of the brain that are close together which can be reconstructed in order to determine any structural abnormalities.
CT Scan
Many x-rays of the brain to construct the brain
An attenuation of tissue encountered along the path of the x-rays.
SPECT/PET Scan
Radiolabeled compounds injected in tracer amounts so that their proton emissions can be detected much like CT
Images made represent the accumulation of the labeled compound.
The compound may reflect blood flow, oxygen or glucose metabolism, or dopamine concentration.
Images often are shown with color scale.
Structural Neuroimaging MRI
Hydrogen atoms make up 63% of the human body.
Hydrogen nuclei have an Nuclear Magnetic resonance signal.
Magnetic resonance imaging primarily images the NMR signal from the hydrogen nuclei
Large number of Slices acquired
Applying radio waves and turning them off to observe the energy emitted in the form of radio waves.
Functional MRI (fMRI)
changes in neuronal activity are associated with local changes in physiological response.
Neural activity -> blood flow _> oxyhemoglobin -> MR signal.
Functional MRI: BOLD Response
Blood oxygen level dependent.
Functional MRI: BOLD Response
Blood oxygen level dependent.
Oxygen rich blood carried from the heart dimagnetic meaning it has magnetic properties
As blood passes through the capillary beds in the brain, oxygen is extracted and the blood loses its magnetic properties (para-magnetic)
BOLD RESPONSE:
The relative proportion of oxygenated blood to oxygenated blood increases in active brain regions.
Talairach Coordinate System
Since individual brains are different shapes and sizes, how can we compare or average brains?
squish or stretch brain into shoebox and extract 3D coordinate (x,y,z) for each activation focus.
Advantages: Widespread system
allows averaging of fMRI data between subjects
allows researchers to compare activation foci
easy to us
disadvantages
based on the squished brain of an elderly woman (how representative is that)?
not appropriate for all brains activation foci can vary considerably. other landmarks like sulci may be more reliable.
What are the advantages of neuroimaging vs. lesion methods
Neuroimaging
Advantages; healthy people
temporal resolution
able to view all regions involved in a task (who-brain analysis)
Disadvantages;
unable to determine if region necessary for a given task
interpretation of null results and “deactivation’s”
Transcranial Magnetic Stimulation (TMS)
Doesn’t image neural activity
Modulates or disrupts neural activity
creates a reversible lesion or scrambles neural activity
How
coils placed on scalp create a magnetic field that induces an electrical field
this alters membrane potential of neurons causing them to fire randomly.
Causes muscle movement.
Functional MRI: Subtraction Method
Example: Where are objects represented in the brain?
T1: View intact objects
T2: View Scrambled objects
T2-T1 = “object” areas
Possible factors added:
1) attentional salience (objects are more interesting than scrambled)
2) Memory (youve seen an apple before but problably not a scrambled apple )
Baseline
May be straightforward (vision studies often include fixation )
Sometimes baseline is less clear, especially during simple rest states
