PSYCH 455 Quiz #1

Who was a pioneer in direct electrical stimulation of the brain?

Wilder Penfield

Who said mental experience arise in the heart?

Aristotle

Who said mental experiences arise in the brain?

Plato

What does stimulation produce?

Mental sensations of thinking, percieving, etc.

Cognitive Neuroscience

Provides a brain-based account of cognitive processes (thinking, perceiving, remembering, etc.)

How was cognitive neuroscience made possible?

Through technological advances that are non-invasive and safe for the brain compared to Penfield

What is the Mind-Body Problem?

It deals with the question of physical substances producing mental experiences

Dualism

The mind and the body act as separate entities (Descartes)

Dual-Aspect Theory

Mind and body are two aspects of the same entity

Reductionism

The mind is explained by phsyical/biological theories; basis for many studies in cognitive neuroscience studies

Timeline of Historical Foundations

\-1929: EEG was developed

\-1950: Cognitive psychology emerges as a field of psychology

\- 1970: CT and MRI imaging is developed (enhanced imaging of lesions)

\- 1980: Development of PET (adapted to models of cognition)

\-1985: First study of TMS (non-invasive and safe)

\- 1990: fMRI development (blood oxygen used as a measure of cognitive function)

\-2010: Human Connectome Project (connectome mapping)

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Phrenology

A discredited field of science that suggests that differences in personality is accounted by the shape of a person’s school; also suggested that different parts of the cortex serve different functions

Functional Specialization

Different brain regions supporting different functions; a degree of specialization of neurons in various regions not just one

Broca’s Area

Responsible for language specialization and speaking; damage to this area creates poor speech comprehension

Wernicke’s Area

Responsible for language comprehension and production; damage to this area could happen independently between the two roles

Cognitive Neuropsychology

The study of brain-damaged patients to inform theories of normal cognition

Information-processing model

An analogy in which behavior is described in terms of a sequence of cognitive stages

What are the challenges of cognitive neuroscience?

It’s possible to study the mind without studying the brain; can tell where cognition is occurring NOT how

What explains the HOW of cognition?

Theories

Network

Cognitive functions are a dynamic exchange of information between regions

Connectomics

Mapping the brain regions and their connections

Human Connectome Project

\-180 distinct cortical areas

\-Emphasizes structural and functional connections

How many neurons does the brain have?

100 billion

How many other neurons can one neuron connect to?

10,000-if all our neurons were connected, our brain would be 12.5 miles in diameter

Neurogenesis

New generation of neurons; we’re not born with our full set of neurons

How often do we lose a neuron?

Every second

What does the structure of a neuron contain?

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Dendrites, cell body, axon- the basic structure

Axons

Transmit electrical signals known as action potentials from the cell body

Dendrites

Receive chemical signals originating from the synaptic cleft

Action potential

Sudden change in electrical properties of neuron membrane in axon; has several distinct phases

Neurotransmitters

Chemical signals that are released by one neuron and affect the properties of other neurons

What kind of effects can neurotransmitters have?

Inhibitory and excitatory effects

Inhibitory effects

When a neurotrasnmitter is less likely to fire; makes the inside of the postsynaptic neuron negative

\-Example: GABA

Excitatory effects

When a neurotransmitter is more likely to fire; makes the postsynaptic neuron more positive

Example: Glutamate

How do neurons code information?

By the number of action potentials produced per second

Spiking rate

Rate of responding; relates to the informational code carried by that neuron

Regional functional specialization

Neurons responding to similar types of information tend to be grouped together

Gray matter

Contains neuronal cell bodies and the visible part of the brain

White matter

Consists of axons, glia, and myelin; connects within between hemispheres and to sub cortical areas

Cerebrospinal Fluid

Contained in the ventricles and surrounds the brain; acts as a protective cushion and carries certain substances like waste or hormones

Anterior/frontal

Towards the front of the brain

Dorsal/superior

Towards the top of he brain

Posterior/caudal

Towards the back of the brain

Ventral/inferior

Towards the bottom of the brain

How many hemispheres are in the brain?

2; left and right

What are the four lobes of the brain?

Frontal lobe, temporal lobe, parietal lobe, and occipital lobe

Gyri

The peaks of the lobe

Sulci

The valleys of the lobes

Cytoarchitecture

Different brain regions are defined by layered composition of cells

Brodmann Areas

A way of referencing different regions in the brain; “BA”

Basal ganglia: Sub-cortex

Modulating both actions and thought by interaction with frontal lobes; implicated in Huntington’s and Parkinson’s disease

Limbic system:Sub-cortex

Connects an organism to its environment, responding to current needs and situation while drawing from past experiences; implicated in emotions, learning, and memory

Diencephalon: Sub-cortex

Thalamus: Processes sensory input (except smell) before the cortex

Hypothalamus: Manages bodily functions like temperature, eating, drinking, sexual activity, etc.

Midbrain

Contained ineferior (hearing) and superior colliculi (gaze orienting); part of the subcritical routes

Hindbrain

Contains the pons and medulla oblongata; governs vital functions like breathing and heart rate 

Cerebellum

Linked to hindbrain; integrates motor commands with sensory feedback for fluid movement; important for dexterity and smooth execution of movement

Mental representation

Cognition copied or stimulated the outside world (e.g., objects)

Neural representation

The outside world is reflected in neural signals (e.g. , varying spiking rates for different stimuli); cognitive neuroscience links these two representations

Single-cell recordings

Electrodes are invasive, positioned or near a neuron (intracellular or extracellular of the axon); measured action potentials per second- appears like “Morse Code”

Electroencephalography (EEG)

Electrodes are non-invasive, placed on the skull; measures combined electrical potentials from millions of neurons

Grandmother cells

A neuron that is hypothesized to respond to just one stimulus; however this may be unlikely since there’s a 1 to 1 mapping between a mental representation and the response of single neurons

Local representation

Like grandmother cells; one neuron carries all information about a stimulus

Sparse distributed

Small number of neurons carry all information about a stimulus (e.g., face processing)

Fully distributed

All neurons in a specific area carries all information about a stimulus

Face Processing with Sparse Distribution

Neurons are not specific to people but rather the visuo-spatial features that vary from face to face

In what contexts are EEGs used in cognitive neuroscience research?

Oscillations and event-related potentials (ERPs)

Oscillations

EEG readings over a period of time; neurons often fire in synchrony at varying rates-specific frequencies relate to certain cognitive functions

Event-related potentials (ERPs)

EEG readings linked to a specific event; considered an enhanced temporal resolution; capture a series of negative and positive peaks

* Pro: Has excellent temporal resolution (related to neural activity)
* Con: Has poor spatial resolution (not possible to tell where the source of signal is coming from in the brain)
* Signal to noise ratio is low; signal can be blocked by doing unconscious behaviors (i.e., blinking or scratching your head; but the signal can become stable over time

ERP and face recognition

Different ERP peaks relates to various face processing stages

\-Stages

1) Perceptual coding of the face

2) Face recognition (identity processing)

3) Person recognition (faces and names)

Difference between EEG and ERPs

* ERPs are measured in milliseconds while EEGS are measured in seconds
* ERPs are measured for particular events

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Structural Brain Imaging

Look at the brain anatomy and function

What are the different types of structural imaging?

* Computerized tomography (CT)
* Magnetic resonance imaging (MRI)

Computerized topography (CT)

Images brain via X-ray absorption; has relatively poor temporal resolution compared to MRI; used to pinpoint tumors in people with cancer

Magnetic resonance imaging (MRI)

Images brain via magnetic fields

What are the advantages of MRI over CT?

* No ionizing radiation exposure
* Better spatial resolution and contrast for white vs. gray matter
* Can be adapted for fMRI to assess brain function

MRI Physics

* Strong magnetic field is applied to the body
* Hydrogen protons align randomly when the magnetic field is applied
* Scanner field strength is 3T, which is greater than that of the Earth
* The spins from the protons produce the MRI signal
* Scans can be developed in 2 seconds or less

Voxel-based morphometry (VBM)

* Measures white and gray matter density in voxels (600k neurons each)
* Used to identify the differences between groups or correlate with cognitive measures
* Can differ from person to person (i.e, people with larger hippocampus and memory)

Diffusion Tenor Imaging (DTI)

Measures organization of white matter

* Based on diffusion of water molecules in axons
* Can see how white matter changes developmentally
* Individual/Group Differences

Functional Brain Imaging

Resolution and functions activation due to convergence of structural imaging and fMRI

Functional Imaging

* Neural activity consumes oxygen and produces electrical signals
* More blood is pumped into the “active” region to compensate for increased oxygen consumption
* Response time is slow, takes several seconds

PET

* Measure regional blood flow and movement around the brain
* More invasive

fMRI

* Measures blood oxygenation
* Offers good spatial resolution but poor temporal resolution
* Measures concentration of deoxyhemoglobin in blood or BOLD (Blood Oxygen Level Dependent contrast)

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BOLD signal

A signal that reflects changes in deoxyhemoglobin and hemodynamic response functions with distinct phases

* HRF peaks at 6-8 seconds which is much longer than ERP

How is a BOLD signal predicted?

* Based on multiples HRFs, voxels with changes according to experiment design and HRF shape

Functional Near-Infrared Spectroscopy (fNIRS)

* Measures BOLD response similarly to fMRI but with a different method
* Uses infrared light that scatters based on oxyhemoglobin vs. deoxyhemoglobin levels
* Flexible with portability and head movement
* Limited to get imaging on deep brain structures; light scattering only reaches the surface of the brain

What does it means for a brain region to be “activated”?

Brain is constantly needing a supply of blood and oxygen without it damage or death is possible

* No thoughts can be read and so the entire brain appears “active”
* A region is active if there is a heightened response in one condition over another

Is it true that we only use 10% of our brain?

No! We basically use every part of our brain and most of the brain is active all the time

Control Condition

* A baseline found in fMRI
* Choosing poor conditions can lead to misleading results

Cognitive Subtraction

A type of experimental design in functional imaging in which activity in a control task is subtracted from activity in an experimental task

Conjunction Analyses in fMRI

Used to determine commonalities across multiple cognitive tasks

* Assess shared regions of activation across various subtractions instead of a singular subtraction

Parametric Designs

* Treats variables as continuous, not categorical (like on/off)
* Correlates brain activity with changes in a variable, instead of contrasting activity between conditions

Functional Connectivity

* Focuses on communication between regions
* Different from functional localization

Default Mode Network (DMN)

* Discovered in the 1900s
* A set of brain regions that is more hemodynamically active during rest than during tasks
* Rest state was hypothesizes to produce spontaneous thought
* Exhibits “deactivation” compared to other tasks