Cognitive Neuroscience Basics

Cognitive Neuroscience

• Cognitive neuroscience is the scientific study of the relationship between the nervous system and cognition.
• Neuroscience is the scientific study of the nervous system.

Building Blocks of the Nervous System

• Neurons are specialized cells that receive and transmit information within the nervous system.
• The brain contains approximately 100 billion neurons and over 100 trillion synapses.
• Each neuron has a cell body, an axon, and dendrites.
• The cell body contains mechanisms to maintain the cell's function.
• The axon is a tube that transmits electrical signals to other neurons.
• Dendrites are branches that extend from the cell body and receive information from other neurons.

How Neurons Communicate

• Neurons receive signals from the environment.
• An action potential (spike) is an electrical signal that travels down the axon.
• The action potential is a brief change in membrane potential.
• When the action potential reaches the axon terminal, neurotransmitters are released.
• Neurotransmitters cross the synaptic space and bind to receptors on the receiving dendrite.
• Neurotransmitters can either be excitatory or inhibitory depending on their effects on the post-synaptic neuron. Excitatory neurotransmitters increase the likelihood of an action potential, while inhibitory neurotransmitters decrease the likelihood.
• Examples of neurotransmitters include glutamate (excitatory), GABA (inhibitory), and dopamine.

How Neurons Process Information

• Not all signals received by a neuron lead to an action potential.
• The cell membrane processes the number and timing of received impulses.
• An action potential only occurs if a certain threshold level is reached.
• Excitation and inhibition interact to determine whether an action potential occurs.

Representation in the Brain

• Feature detectors are neurons that respond optimally to specific stimuli.
• Simple cells respond best to light bars of a particular orientation.
• Complex cells respond best to oriented bars of light with a specific length.
• Specificity coding represents a particular stimulus with one specific neuron.
• Distributed coding represents stimuli with a specific pattern of neuron firing across multiple neurons.
• Sparse coding uses a limited number of neurons to represent different stimuli.

Localization of Function

• Specific functions are performed by particular areas in the brain.
• Cognitive functions can be affected by damage to specific areas of the brain.
• The cerebral cortex is a 3-mm thick layer that covers the brain and is responsible for many cognitive functions.
• Subcortical regions also play a role in cognition, like the basal ganglia.

Method: Lesions

• Lesions are one way to study cognitive functions.
• Researchers experimentally lesion non-human animals or study cases with accidental human lesions.
• Transcranial Magnetic Stimulation (TMS) can induce temporary lesions in humans.

Method: TMS

• TMS can be used to safely reproduce the effect of a temporary cortical lesion.
• TMS can also be used to temporarily add noise to neural activation.
• Sequence production is an example of a cognitive function that can be studied with TMS.

Method: Inactivation

• TMS is often restricted to cortical regions.
• Researchers use various inactivation methods for non-human animals.
• Muscimol is a GABA agonist, used to selectively inactivate brain regions with GABA receptors.
• The example shown regarding the basal ganglia and automatic sequence production was presented using this method.

Method: Brain Imaging

• Positron Emission Tomography (PET) measures changes in blood flow.
• fMRI measures blood flow changes using magnetic properties; no radioactive tracer is necessary.
• Subtraction techniques are used in PET and fMRI to identify areas active during a particular cognitive task.
• EEG measures electrical activity on the scalp.
• ERPs are calculated when EEG signals are time-locked and averaged over multiple trials.

Localization of Function: Subcortical areas

• Basal ganglia are involved in sequence processing and categorization.
• Hippocampus aids in the formation of memories.
• Amygdala handles emotions and emotional memories.
• Thalamus relays sensory information to the cortex.

Distributed Processing in the Brain

• Cognitive functions often involve many different areas of the brain working together.

Do brains make us lose our minds?

• Neuroscientific facts, while sometimes alluring to non-experts, don't necessarily improve explanations of psychological phenomena.
• Even good explanations can be made superficially more acceptable with neuroscientific embellishments, but bad explanations remain bad.

What about pictures of brains?

• Including brain images can influence evaluations of scientific reasoning, even though the images may not substantively change the quality of the reasoning.