Cognition - Chapter 2: Cognitive Neuroscience

Cognitive neuroscience

The study field concerned with studying the neural and physiological basis of cognition

Levels of analysis

The idea a that a topic can be studied in many different ways

Levels of analysis (con’t)

Each approach contributes its own dimension to our understanding

e.g. When someone perceives a person they’re talking with along with the park they’re in, and then remembers the person and the convo while passing by the park a few days later

Neurons

Cells that create and transmit information along the nervous system about what we experience and know

Nerve net

A network of continuously interconnected nerve fibers

Neuron doctrine

The idea that neurons transmit signals in the nervous system, and that these cells are not continuous with other cells

Camilo Golgi’s contribution

He developed a staining technique in which a thin slice of brain tissue was immersed in a solution of silver nitrate to distinguish neural cells

Cell body

The metabolic center of the neuron that keeps the neuron alive through mechanisms housed within it

Dendrites

Tree-like branches that extend outward to receive information from other cells

Axons (nerve fibres)

Long extensions of the nerve body that transmit information along the neuron from cell body to synapse

Synapse

The space between the end of an axon and the cell body or dendrite of the next axon

Neural circuits

Group of interconnected neurons that are responsible for neural processing.

Receptors

Specialized neural structures (in the eyes, nose, mouth) that respond to environmental stimuli

e.g. light, mechanical stimulation, or chemical stimuli.

Resting potential

Difference in charge between the inside and outside of a nerve fiber when there’s no charge (-70mv)

Microelectrodes

Small wires that are used to record electrical signals from single neurons.

Recording electrode

A very thin glass or metal probe that can pick up electrical signals from single neurons while studying neural functioning

Reference electrode

An electrode generally placed where the electrical signal remains constant

Reference electrode (con’t)

Any change in charge between the recording and reference electrodes reflects events happening near the tip of the recording electrode.

Action potential (nerve potential)

An electrical response that’s responsible for transmitting neural information along the axon and for communication between neurons.

Neurotransmitters

Chemicals that are released at the synapse in response to incoming action potentials.

Neurotransmitters (con’t)

These chemicals make it possible for the signal to be transmitted across the gap that separates the end of the axon from the dendrite or cell body of another neuron

Adrian’s connection between nerve firing and experience

He said if nerve impulses “are crowded closely together the sensation is intense, if they are separated by long intervals the sensation is correspondingly feeble” [The Basis of Sensation (1928)]

Adrian’s connection between nerve firing and experience (con’t)

Electrical signals represent the intensity of the stimulus, so pressure that generates “crowded” electrical signals feels stronger than pressure that generates signals separated by long intervals

Quality and neural firing

Refers to the different experiences associated with each of the senses

e.g. Perceiving light for vision, sound for hearing, smells for olfaction, etc

Quantity and neural firing

When the rate of neural firing is related to the intensity of stimulation, which, in turn, is related to the magnitude of an experience

e.g. Feeling pressure on the skin or experiencing the brightness of a light.

Principle of neural representation

States that everything a person experiences is based on representations (something that stands for) in the person’s nervous system

Two key facts discovered about the primary visual region and neurons

1. Many neurons at higher levels of the visual system fire in response to complex stimuli like geometric patterns and faces

2. A specific stimulus causes neural firing that is distributed across many regions of the cortex

How are cognitive functions generated?

By their primary region, as well as many different brain regions

Feature detectors

Neurons that respond to specific stimuli such as orientation, movement, and length

e.g. Size, orientation

Experience-dependent plasticity

When experience changes the structure of the brain.

Visual cortex

The area in the occipital lobe that receives signals from the eyes

Visual cortex (con’t)

Some of these visual regions receive signals directly from the visual cortex, others are part of a sequence of interconnected neurons, and some are far down the line from the visual cortex.

Temporal lobe

The lobe on the side of the brain that contains mechanisms responsible for language, memory, hearing, and vision.

Hierarchical processing

Processing that occurs in a progression from lower to higher areas of the brain.

Problem of sensory coding

The problem of determining the neural representation for the senses.

Sensory code

How neural firing represents various characteristics of the environment.

Specificity coding

The idea that an object could be represented by the firing of a specialized neuron that responds only to that object

e.g. The signaling of a person’s face by the firing of a neuron that responds only to that person’s face.

Population coding

The neural representation of a particular object by the pattern of firing of by a large number of neurons

Population coding’s advantage

A large number of stimuli can be represented because large groups of neurons can create a huge number of different patterns.

Sparse coding

Neural coding based on the pattern of activity in small groups of neurons.

Sparse coding (con’t)

Occurs when a particular object is represented by a pattern of firing from only a small group of neurons

Localization of function

When specific functions are performed by specific regions of the brain.

e.g. Areas have been identified that are specialized to process information involved in the perception of movement, form, speech, etc

Cerebral cortex

The 3-mm-thick outer, wrinkled layer of the brain that contains the mechanisms responsible for higher mental functions

e.g. Perception, language, thinking, etc

Subcortical regions

Areas of the brain below the cerebral cortex

e.g. The amygdala and the hippocampus.

Neuropsychology

The study of the behavior of people whose brains have been damaged by traumatic injury

Cortical equipotentiality

The 1800s idea that the brain operates as an indivisible whole, as opposed to operating based on specialized areas.

Broca’s area

An area in the frontal lobe associated with the production of language.

Broca’s area (con’t)

Damage to this area causes Broca’s aphasia

Broca’s aphasia

A condition associated with damage to Broca’s area, in the frontal lobe, characterized by labored ungrammatical speech and difficulty in understanding some types of sentences.

Wernicke’s area

Area in the temporal lobe associated with understanding language.

Wernicke’s aphasia

A condition (caused by damage to Wernicke’s area) that is characterized by difficulty in understanding language, as well as fluent, grammatically correct, but incoherent speech.

Occipital lobe

The lobe at the back of the brain that is devoted primarily to analyzing incoming visual information.

Occipital lobe (con’t)

Damage to it resulted in blindness

Parietal lobe

The lobe at the top of the brain that contains mechanisms responsible for sensations caused by stimulation of the skin and also some aspects of visual information.

Frontal lobe

The lobe in the front of the brain that serves higher functions

e.g. language, thought, memory, and motor functioning.

Prosopagnosia

An inability to recognize faces caused by damage to the temporal lobe

Double dissociation

A situation in which a single dissociation can be demonstrated in one person, and the opposite type of single dissociation can be demonstrated in another person

Double dissociation example

Person 1: function A is present, function B is damaged; Person 2: function A is damaged, function B is present

Electroencephalography (EEG)

A non-invasive neuroimaging method where electrodes are placed on the scalp to measure and record electrical brain activity

Magnetoencephalography (MEG)

A technique that measures the magnetic fields (generated by electrical currents in neurons) produced by neural activity in the brain.

Near-Infrared Spectroscopy (NIRS)

Uses near-infrared light to measure changes in blood oxygenation and blood volume in the brain

Near-Infrared Spectroscopy (NIRS) [con’t]

Can infer the levels of oxygenated and deoxygenated blood in the brain by producing near-infrared light and detecting the light that is reflected through the scalp and skull

Transcranial Magnetic Stimulation (TMS)

Uses magnetic fields to stimulate nerve cells in the brain by generating a magnetic pulse that induces an electrical current in specific areas of the brain, which can temporarily disrupt localized brain activity.

Diffusion Tensor Imaging (DTI)

A specialized type of magnetic resonance imaging (MRI) that focuses on measuring the diffusion of water molecules in human (or other animal) tissue, particularly in white matter tracts of the brain.

Diffusion Tensor Imaging (DTI) [con’t]

Allows for the visualization and mapping of the brain’s structural connectivity by revealing the pathways of white matter fibres.

Functional magnetic resonance imaging (fMRI)

A brain imaging technique that measures how blood flow changes in response to cognitive activity

Voxels

Small, cube-shaped regions of the brain (about 2 or 3 mm on a side) and are used in the analysis of data from brain scanning experiments.

Voxels (con’t)

They aren’t brain structures, but are simply small units of analysis (pixels) created by the fMRI scanner

Fusiform face area (FFA)

An area in the temporal lobe that contains many neurons that respond selectively to faces.

Fusiform face area (FFA) [con’t]

Damage to this brain region can result in prosopagnosia

Fusiform gyrus

A brain structure that spans the basal surface of the occipital and temporal lobes of both hemispheres.

Parahippocampal place area (PPA)

An area in the temporal lobe that contains neurons that are selectively activated by pictures of indoor and outdoor scenes.

e.g. Information about spatial layout, because increased activation occurs when a person views pictures both of empty rooms and of rooms that are completely furnished

Extrastriate body area (EBA)

An area in the temporal cortex that’s activated by pictures of bodies and parts of bodies, but not by faces or other objects.

Multidimensional

Refers to the fact that even simple experiences involve combinations of different qualities.

Distributed representation

Occurs when a specific cognition activates many areas of the brain.

Visual memories

Sight-related memories

e.g. Picturing someplace you often visit

Olfactory memories

Smell-related memories

e.g. A smell triggering memories for a familiar place

Auditory memories

Sound-related memories

e.g. Remembering a favorite song

Neural networks

Interconnected regions of the brain or neuron structures that can communicate with each other

The 4 principles of neural networks

1. There are complex structural pathways called networks that form the brain’s information highway.

2. Within these structural pathways, there are functional pathways that serve different functions.

3. These networks operate dynamically, mirroring the dynamic nature of cognition.

4. There is a resting state of brain activity, so parts of the brain are active all the time, even when there is no cognitive activity.

Structural connectivity

The physical connections between different brain regions, established through neural pathways.

Structural connectivity (con’t)

The brain’s “wiring diagram”, created by nerve axons that connect different brain regions.

Structural connectivity (III)

Has been likened to “fingerprints” that are different for every person

Track-weighted imaging (TWI)

A technique for determining connectivity in the brain that is based on detection of how water diffuses along the length of nerve fibers.

Connectome

A map of the brain that details the complex network of neurons and their connections.

Connectome (con’t)

Indicates the “structural description of the network of elements and connections forming the human brain”

Functional connectivity

The extent to which the neural activity in separate brain areas is correlated with each other

Resting-state fMRI

The fMRI response recorded when a person is at rest

Resting-state fMRI (con’t)

Is uninvolved in any cognitive tasks

Resting-state functional connectivity

A method for determining functional connectivity that involves determining the correlation between the resting-state fMRI in separated structures.

Seed location

The area of the brain associated with carrying out a specific cognitive or motor task that serves as the reference area for the resting-state functional connectivity method.

Time-series response

The way the fMRI response changes over time

Test location

Comparing the activity at it with the seed location’s activity to determine the degree of functional connectivity between the two locations

Dynamics of cognition

Changes in the flow of activity within and across the functional networks in the brain, depending on conditional changes

Default mode network (DMN)

A network of structures that are active when a person is not involved in specific tasks.

Double dissociation (con’t)

A process by which it is determined that different functions are served by different mechanisms

Nervous system

An electrochemical communication network consisting of nerve cells that fire together from the central and peripheral nervous system

Nervous system (con’t)

Consists of groups of neurons that work together in neural networks

Central nervous system

Consists of brain and spinal cord (the body’s decision makers)

Peripheral nervous system

Sensory & motor neurons connecting the central nervous system and to the rest of the body for transmitting information