Chapter 2 Cognitive Neuroscience

Cognitive neuroscience

Field concerned with studying the neural basis of cognition

Levels of analysis

A topic can be understood by studying it at a number of different levels of a system

Neurons

Cell that is specialized to receive and transmit information in the nervous system

Nerve net

A network of continuously interconnected nerve fibres (as contrasted with neural networks, in which fibres are connected by synapses).

Neuron doctrine

The idea that individual cells called neurons transmit signals in the nervous system, and that these cells are not continuous with other cells as proposed by nerve net theory

Cell body

Part of a cell that contains mechanisms that keep the cell alive. In some neurons, the cell body and the dendrites associated with it receive information from other neurons

Dendrites

Structures that branch out from the cell body to receive electrical signals from other neurons

Axons

Part of the neuron that transmits signals from the cell body to the synapses at the end of the axon

Synapse

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 that respond to environmental stimuli such as light, mechanical stimulation, or chemical stimuli

The concept introduced by Cajal—individual neurons, synapses, and neural circuits—are basic principles used today to explain…..

how the brain creates cognition

Resting potential

Difference in charge between the inside and outside of a nerve fibre when the fibre is at rest (no other electrical signals are present).

When the nerve is at rest, there is a difference in charge, called the resting potential, of,,,,

-70 millivolts (mV) between the inside and outside of the axon

Adrian recorded electrical signals from single neurons using…

Microelectrodes — small shafts of hollow glass filled with a conductive salt solution that can pick up electrical signals at the electrode tip and conduct these signals back to a recording device

Micro electrodes

small wires that are used to record electrical signals from single neurons

There are two electrodes:

a recording electrode and a reference electrode

Recording electrode

When used to study neural functioning, a very thin glass or metal probe that can pick up electrical single neurons

Reference electrode

Used in conjunction with a recording electrode to measure the difference in charge between the two.

Reference electrodes are generally placed where the electrical signal remains constant, so any change in the charge between the recording and reference electrodes reflects events happening near….

the tip of the recording electrode

As the impulse passes the recording electrode, the charge inside the axon rises to…

+40 millivolts, compared to the outside.

As the impulse continues past the electrode, the charge inside the fibre reverses course and the starts becoming….

negative again, until it returns to the resting potential. This impulse, which is called action potential, lasts about 1 millisecond (1/1000 of a second)

Nerve impulse

An electrical response that is propagated down the length of an axon (nerve fibre). Also called action potential

Adrian found that each action potential travels all the way down the axon without changing its height or shape. This property makes action potentials ideal for sending signals over a distance because it means…

That once an action potential is started at one end of an axon, the signal will still be the same size when it reaches the other end

Neurotransmitters

Chemical that is released at the synapse in response to incoming action potentials

Adrian studied the relation between nerve firing and sensory experience by measuring how….

the firing of a neuron from a receptor in the skin changed as he applied more pressure to the skin

If all nerve impulses are basically the same whether they are caused by seeing a red fire engine or remembering what you did last week, how can these impulses stand for different qualities?

Different qualities of stimuli, and also different aspects of experience, activate different neurons and different brain regions

Principle of neural representation

Everything a person experiences is based on representations in the person’s nervous system

In the 1960s, researchers began focusing on recording from single neurons in the primary visual region, the place where…

signals from the eye first reach the cortex

Vision dominated early research because…

stimuli could be easily controlled by creating patterns of light and dark on a screen and because a lot was already known about vision

Feature detectors

Neurons that respond to specific visual features, such as orientation, size, or the more complex features that make up environmental stimuli

Experience-dependent plasticity

A mechanism that causes an organism’s neurons to develop so they respond best to the type of stimulation to which the organism has been exposed

Visual Cortex

Area in the occipital lobe that receives signals from the eyes

Temporal lobe

The lobe on the side of the brain that consists 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 representation of a specific stimulus by the firing of neurons that respond only to that stimulus. An example would be the signalling of a person’s face by the firing of a neuron that responds only to that person’s face

Population coding

neural representation of a stimulus by the pattern of firing of a large number of neurons

Sparse coding

neural coding based on the pattern of activity in small groups of neurons

Localization of function

Location of specific functions in specific areas of the brain. For example, areas have been identified that are specialized to process information involved in the perception of movement, form, speech, and different aspects of memory

Cerebral cortex

The 3-mm-thick outer layer of the brain that contains the mechanisms responsible for higher mental functions such as perception, language, thinking, and problem solving

Subcortical regions

Areas of the brain below the cerebral cortex. Two examples of subcortical structures are the amygdala and the hippocampus

Brain imaging

Technique that creates pictures of neural structures

Action potential

Impulse responsible for transmitting neural information and for communication between neurons

What is the function of the myelin sheath of a neuron?

It speeds the processing of the electrical signal down the axon

Default mode network (DMN)

Network of structures that are active when a person is not involved in specific tasks

Test location

When measuring resting-state functional connectivity, the activity at the test location is compared to the activity at the seed location to determine the degree of functional connectivity between the two locations

Time-series response

The way fMRI response changes over time

Seed location

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

Resting-state functional connectivity

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

Resting-state fMRI

The fMRI response recorded when a person is at rest (not involved in any cognitive tasks).

Functional connectivity

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

Connectome

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

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 fibres

Structural connectivity

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

Neural networks

Groups of neurons or structures that are connected together

Distributed representation

Occurs when a specific cognition activates many areas of the brain

Multidimensional

The multidimensional nature of cognition refers to the fact that even simple experiences involve combinations of different qualities

Extrastriate body area (EBA)

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

Parahippocampal place area (PPA)

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

Fusiform gyrus

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

Fusiform face area (FFA)

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

Task-related fMRI

The fMRI response that occurs in response to a specific cognitive task

Voxels

Small cube-shaped areas in the brain used in the analysis of data from brain scanning experiments

Functional magnetic resonance imaging (fMRI)

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

Diffusion Tensor Imaging

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. This technique allows for the visualization and mapping by the brain’s structural connectivity by revealing white matter fibres

Trancranial Magnetic Stimulation

A non-invasive procedure that uses magnetic fields to stimulate nerve cells in the brain. A TMS device generates a magnetic pulse that induces an electrical current in specific areas of the brain, which can temporarily disrupt localized brain activity

Near-Infrared Spectroscopy

A non-invasive imaging technique that uses near-infrared light to measure changes in blood oxygenated and blood volume in the brain. NIRS can infer the levels of oxygenated and deoxygenated hemoglobin in the brain by producing near-infrared light and detecting the light that is reflected

Magnetoencephalography

A non-invasive neuroimaging technique that measures the magnetic fields produced by neural activity in the brain. These magnetic fields are generated by electrical currents in neurons

Electroencephalography

A non-invasive neuroimaging method used to record electrical activity of the brain that involves placing electrodes on the scalp to detect and measure the electrical signals produced by neurons

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 (i.e., Person 1: function A is present, function B is damaged; Person 2: function A is damaged, function B is present).

Prosopagnosia

Condition caused by damage to the temporal lobe that is characterized by an inability to recognize faces

Frontal lobe

The lobe in the front of the brain that serves higher functions such as language, thought, memory, and motor functioning

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

Occipital Lobe

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

Wernicke’s aphasia

A condition, caused by damage to Wernicke’s area, that is characterized bu difficulty in understanding language, and fluent, grammatically correct, but incoherent speech

Wernicke’s area

Area in the temporal lobe associated with understanding language. Damage to this area causes Wernicke’s aphasia

Broca’s aphasia

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

Bronca’s area

An area in the frontal lobe associated with the production of language. Damage to this area causes Bronca’s aphasia

Cortical equipotentiality

The idea, popular in the early 1800s, that the brain operates as an individual whole, as opposed to operating based on specialized areas

Neuropsychology

The study of the behaviour effects of the brain damage in humans

True or false: Cognition neuroscience focuses only on the psychological component of cognition

False. Cognitive neuroscience does not focus on psychology but on the physiology of cognition

Chemical processes —> Neurons activated —> Brain structures activated —> Groups of brain structures activated —> Perception

Physiological

What is the basic building block of the nervous system?

Neuron

What transmits the message?

axon

What has long branches?

Dendrite

What is also called nerve fibre?

Axon

What receives the message

Dendrite

Which part of a neuron is covered in myelin?

Axon

Neurons transmit signals that begin as ……. and are converted to …..?

They begin as electrical and then are converted to chemical

Winona is an 80-year-old individual who is suffering from tremors and difficulty remembering things. Which part of the neuron is likely affected by this condition?

Myelin

Which lobe of the brain is responsible for temperature and pain perception?

Parietal