02.+Cognitive+Neuroscience

February 10, 2015
 * 02. Cognitive Neuroscience**

The brain Brain research techniques Applications
 * Outline**

Communication
 * The Brain**
 * Neurons **
 * Dendrites detect incoming signals
 * Axons send signals
 * Cell body contains the nucleus and cellular machine
 * Communication //within// neurons happens via electrical signals. If the post-synaptic cell reaches an electrical threshold, an action potential is fired
 * Communication //between// neurons happens via neurotransmitters (e.g., serotonin, dopamine, GABA, etc.)


 * Brain structures**
 * Hindbrain
 * sits atop the spinal cord
 * Controls rhythms of the heart and breathing
 * Includes the cerebellum, which coordinates movements and balance
 * Midbrain
 * sits above the hindbrain
 * coordinates movement, especially eye movement
 * includes part of the auditory pathways
 * regulates the experience of pain
 * Forebrain [[image:lobes.png width="214" height="178" align="right"]]
 * Comprises most parts of the brain that are visible from the outer surface.
 * Includes the cortex and subcortical structures
 * Four lobes: Frontal, Parietal, Temporal, Occipital
 * Two cerebral hemispheres connected by the corpus callosum
 * Subcortical structures: Thalamus, Hypothalamus, Amygdala, Hippocampus

Two types of photoreceptors (cells that respond to light) are found on the retina
 * The Visual Systems**
 * Rods
 * higher sensitivity (i.e., respond to dim light)
 * lower acuity
 * color-blind
 * found in the periphery of the retina
 * Cones
 * lower sensitivity
 * higher acuity
 * color-sensitive
 * found in the fovea (center of the eye)
 * Serial vs. Parallel Processing**
 * Serial processing[[image:serial processing.png width="102" height="99" align="right"]]
 * one step at a time
 * slow, effortful
 * Conjunction task: combination of features (red + square) require examining each item sequentially. Serial processing of one item at a time.
 * Parallel processing[[image:parallel processing.png width="111" height="109" align="right"]]
 * many steps at the same time
 * fast, easy
 * Single feature task: a single feature (red) "pops out." Parallel processing of all items at once


 * The Binding Problem**
 * Different features (shape, color, movement, etc.) are processed in different parts of the brain. This processing occurs in parallel
 * To perceive an object requires binding these features together
 * 2 elements that help solve the binding problem:
 * Spatial position: the visual areas processing features like shape, color, and motion each know the spatial position of the object
 * Neural synchrony: the visual areas processing features of the same object fire in a synchronous rhythm with each other


 * The Scientific Approach**
 * Behaviorists say: The mind is unobservable! The mind is a black box.
 * Cognition: looking in the black box
 * Cognition is the study of the mind


 * The Basic Logic**
 * Localization: if brain area X is involved in process A then:
 * removing area X should disrupt process A (lesion studies)
 * area X should be active during process A (imaging studies)

Visualization
 * Imaging Techniques**
 * Functional Magnetic Resonance Imaging (fMRI)
 * Measures blood flow
 * Good spatial resolution of the whole brain. Very precise
 * Bad temporal resolution. Signal takes about 6 seconds.
 * Magnetic Resonance Imaging (MRI)
 * Static image. Shows brain structure
 * Event Related Potential (ERP)
 * Measures electrical activity on scalp
 * Bad spatial resolution. Imprecise, the skull diffuses electricity. Limited: only measures surface.
 * Good temporal resolution. Accurate to the millisecond.
 * Single-cell recording
 * Good spatial resolution. Extremely precise. Unlike fMRI, doesn't measure whole brain
 * Good temporal resolution. Basically instantaneous
 * Mostly done with nonhuman animals, since it requires sticking a probe in the brain.
 * The Puzzle of Activation**
 * Let's say the hippocampus is active during the encoding of new memories. This could potentially mean...
 * the hippocampus does the encoding
 * the hippocampus is a relay station
 * the hippocampus is not necessary, but is incidentally activated by another area
 * fMRI can tell you that active regions are //correlated// with the task in question, but not whether they're //necessary// for the task
 * To tell whether a brain area is necessary, see if the function is compromised when the area is removed (lesion studies)
 * Lesion techniques:
 * TMS: Transcranial Magnetic Stimulation
 * strong magnet turns off nearby brain activity
 * good for determining causation
 * only works near the surface
 * poor spatial resolution
 * Lesions
 * Good for determining causation
 * But you can't do them to people on purpose. Results from surgery or brain injury/stroke, but such damage is rarely isolated to one structure
 * Applications**
 * When you visualize, your motor cortex acts like it's controlling muscles even when it isn't.
 * Experiment: participants practice motor movement on a keyboard. One group practiced mentally, one group practiced physically.
 * Result: equal or better performance following mental practice. Visualization works!