Neuropsychology Quiz: Brain Damage Techniques

Cognitive Psychology - PSYC 365 - Cognitive Neuroscience

• The course is Cognitive Psychology, PSYC 365, specifically focusing on cognitive neuroscience.
• Objectives include defining and identifying neuron components, describing their role in representation, explaining brain study techniques, outlining cortical structures and functions, and comparing/contrasting hemispheric functions.

What are Neurons?

• Neurons are nerve cells.
• Their function is to create and transmit information.
• Neurons have characteristics including sending and receiving electrical signals.
• Neurons are interconnected in networks.
• On average, each neuron has 10,000 connections.
• The brain is a 3.5 lb structure.
• Neurons are the building blocks of the brain.

Three Components of a Neuron

• Dendrites: Receive messages from other neurons.
• Cell Body (Soma): Combines and processes incoming signals from dendrites. It contains vital cell structures like the nucleus and DNA.
• Axons: Send signals (electrical impulses) to other neurons, muscles, or glands.

Neural Representation

• Neural representation is the way the nervous system represents stimuli, not a direct contact.
• Sight is represented by light, and sound by sound waves.
• Taste and smell are represented by chemicals.
• Processing stimuli from sensory neurons triggers an action potential in neurons.
• Multiple brain regions work together for accurate representation.

Theories of Neural Representation

• Specificity Coding: Each stimulus is represented by a specialized neuron (e.g., "grandmother cell"). Problems include insufficient neurons and lack of evidence from single-cell recordings regarding new objects.
• Population Coding: Each stimulus is represented by a pattern of firing across many neurons. It has supporting evidence. Problems include the need for numerous neurons for all functions.
• Sparse Coding: Each stimulus is represented by a pattern of firing across a small subset of neurons (many not firing). This theory has reliable evidence and is considered most reliable.

Major Techniques for Studying the Brain

• Destruction:
• Animal studies: Ablation (removal), lesions (focused damage) using electrodes or chemicals
• Human studies: Lesions from accidents/diseases (e.g., stroke), or surgical lesions to control seizures
• Neuropsychology: Used with human tests. Assessing simple-to-complex functions, impairments, and severity. Standardized tests help.
• Techniques are used because destruction and stimulation of brain regions help see their effects in behavior.
• Stimulation: Mild electric current used; enhancing or disrupting cognitive functions. Used in invasive (e.g., brain surgery) or some less invasive ways.

Specific Brain Imaging Techniques

• CAT/CT: Computerized axial tomography, X-Ray imaging; good for localized tumors/lesions but poor spatial resolution and exposure to radiation.

• MRI: Magnetic resonance imaging; shows brain structures, reveals soft tissue abnormalities, great spatial resolution, non-invasive.

• EEG: Electroencephalography; Records electrical activity of large groups of neurons; excellent temporal resolution (milliseconds), but poor spatial resolution and sensitive to movement.

• fMRI: Functional magnetic resonance imaging; Measures blood flow changes correlating with oxygen usage; indirect measure of brain activity/cognition, inferring active areas based on oxygen use, similar advantages/disadvantages to MRI.

fMRI: Connectivity

• Brain areas connect and work together to form cognitive processes.
• Connections can be structural or functional.
• Neural networks exist where brain areas consistently communicate, extending sparse/distributed coding.

fMRI: Brain Networks

• Default network: Active brain areas during "rest" or mind wandering. Thinking about the past or future, ourselves and others.

Exercise: Naming a Technique for a Study

• fMRI would be a best method for a study of the amygdala and hippocampus during the processing of emotional information.

Cerebral Cortex

• The cerebral cortex is the top wrinkly layer of the brain, containing ~80% of neurons.
• Its ratio to the size of the brain differentiates humans from other mammals.
• Categorization groups similar functions into cortical areas. Some functions involve multiple areas.

Major Functions of Four Lobes

• Frontal: Many functions (speech, movement, planning, emotion).
• Parietal: Somatosensory (touch, temp) and high level vision.
• Temporal: Auditory and high level visual processing, memory.
• Occipital: Visual (color, form, spatial).

Primary Areas of Four Lobes

• Areas in the cortex where sensory information is first processed. The location is critical to the function.

Association Areas

• These areas exist in all four lobes, and they are involved in many higher mental functions. These areas combine multiple sensory/motor systems to achieve sophisticated outcomes eg language, problem-solving, memory encoding and recall.

Major Functions of Frontal Cortex

• Broca's area: Speech production.
• Motor cortex: Muscle movements.
• Prefrontal cortex: Executive functions (setting goals, planning, emotion regulation, self-awareness). If damaged, problems predict/produce actions, impulse control, and empathy. Also, recall of a sequence or prior learning.

Corpus Callosum & Split-Brain

• The corpus callosum is a nerve bundle for information transfer.
• In split-brain patients, the corpus callosum is severed.
• This can lead to unique performance patterns. Information in a specific visual field is processed more appropriately by the opposite side of the brain.

Commsissurotomy

• Commisurotomy is a technique to disconnect both hemispheres of the brain, in patients with severe epilepsy, allowing examination of the role of each separate brain region.

Split Brain Phenomenon

• In split-brain patients, hemispheres cannot communicate.
• Information from one visual field is only processed by the opposite hemisphere.

Lessons from Split-Brain Phenomenon

• The split-brain effect can be helpful to understand brain functionality and how hemispheres are interconnected.
• The method may not always be consistent, as functional abilities may be limited when specific areas are severed or limited by prior injury or conditions, or by other factors affecting brain functionality.