Neuropsychology: Apoptosis and the Nervous System

Norms & Expectations

• Prepare for class
• Listen
• Participate
• Revise
• Show up on time

Did You Know?

• The sympathetic nervous system creates more neurons that it will need
• When a neuron connects to a muscle, the muscle releases a protein called nerve growth factor (NGF) that promotes survival and growth of the axon
• An axon that lacks the NGF degenerates, the neuron's body dies
• Neurons begin life with a “suicide program” and will destruct if an appropriate postsynaptic cell is not contacted by a specified age
• Apoptosis is the name of this neuron self-destruction, or programmed cell death
• Apoptosis differs from necrosis, which is cell death caused by injury/toxic substances

Neuropsychology

• It is the scientific study of the relationship between behavior and brain function
• Neuropsychology incorporates fields like anatomy, biology, biophysics, ethology, pharmacology, physiology, psychology, and philosophy
• Investigation of the relationship between the brain and behavior can identify impairments stemming from trauma and diseases of the brain
• The field is strongly influenced by the brain theory and the neuron theory

Brain Structures

• The brain consists of two hemispheres, one on the left and one on the right
• The cerebral cortex is a thin external layer of the brain
• The brain has four lobes: occipital, temporal, parietal, and frontal
• Folds/bumps in the cortex are called gyri
• Cracks in the brain are called sulci
• The brain’s basic plan is a tube filled with cerebrospinal fluid (CSF), which cushions it and assists in the removal of metabolic waste
• Deep sulci are called fissures, the longitudinal fissure divides the two hemispheres, and the lateral fissure divides each hemisphere into halves
• Pathways are called commissures; the largest is the corpus callosum, which connects the hemispheres
• Each hemisphere has four lobes named after the skull bones
• The temporal lobe lies below the lateral fissure
• The frontal lobe is above the temporal lobe at the front of the brain
• The parietal lobe is located behind the frontal lobe
• The occipital lobe is at the back of each hemisphere

Three-Part Brain

• The three-part brain is conceptually useful evolutionarily, anatomically, and functionally
• Only spinal cords preceded brain stems and forebrains in animals from an evolutionary perspective
• In prenatal development, the spinal cord forms before the brainstem, which forms before the forebrain
• Functionally, the forebrain mediates cognitive functions, the brainstem mediates regulatory functions, and the spinal cord conveys and reacts to sensory information in the spinal cord

Aristotle: Mentalism

• Mentalism maintains that the mind is responsible for all behavior
• The central topic in neuropsychology is how the brain and behavior relate
• Aristotle developed a formal theory of behavior and said nonmaterial psyche is responsible for thoughts, perceptions, and emotions
• He was the first person to propose a formal theory of behavior
• Psyche was then said to govern behavior, which was later adopted by Christianity, in its concept of the soul
• Now, psyche has been translated to the mind
• Mentalism has influenced modern neuropsychology; terms like sensation, perception, attention, imagination, etc. still apply today

Descartes: Dualism

• Descartes was the first person to write a text about neuropsychology in 1684
• He was impressed by machines
• He said that the body is like a machine
• The mind is nonmaterial and without spatial extent
• The body operates on principles similar to those of a machine, but the mind decided what movements the machine should make

Dualism

• This perspective indicates that behavior is caused by two things: the mind and body
• Dualism originated the mind-body problem: a person is capable of consciousness and rationality due to having a mind, but how can a nonmaterial mind produce movements in a material body
• Descartes proposed that animals do not have minds and are only machinelike
• The mind develops with language during childhood, and mental disease impairs rational processes of the mind
• If animals could speak or reason, they would have minds

Darwin: Materialism

• Rational behavior can be explained by the workings of the nervous system without having to refer to a nonmaterial mind
• Materialism rooted from the evolutionary theories of Alfred Russel Wallace (1823-1913) and Charles Darwin (1809-1892)
• Adaptation and learning are enabled by the brain's ability to form new connections and pathways
• Neuroplasticity is the nervous system's potential for physical or chemical change that enhances environmental adaptability and the ability to compensate for injury
• Epigeneticists describe how gene influence leads to structural brain changes due to environment and experience

Neuroplasticity

• The work of previous physiologists and biologists challenged the idea of localized brain functions
• Removing small regions of cortex on animal models of human clinical cases lead both men to expect that certain functions would be lost
• Through time, the animals recovered their initial impairments and their typical actions

Understanding Neuroplasticity

• Goltz removed most of the cortex from 3 dogs studied for 57 days, 92 days, and 18 months
• Dog that survived 18 months was more active, and its periods of sleep/wake were shorter
• Dog walked well on uneven ground and was able to regain its balance after falling
• Dog was able to orient touches and pinches, snapping at objects that touched it
• It accepted meat soaked in milk, but rejected meat soaked in bitter quinine
• Dog also responded to light and sounds, although its senses were less sensitive
• The remaining brainstem could substitute for the cortex

What About Humans?

• Neuroscientists distinguish several stages in the development of neurons
• Proliferation is the production of new cells, especially in early development
• In development, the cells lining the ventricles in the brain divide
• Some cells function as stem cells, while others transform into neurons that migrate across the nervous system
• Most human migration occurs before birth. Some continue the first month after birth
• Humans' brains have long periods of neuronal proliferation, especially in chimpanzees
• Neurons form within the first 28 weeks of gestation, but premature birth inhibits neuron formation

Neuronal Migration

• Primitive cells (not yet neurons) begin roaming in development
• Immunoglobulins and chemokines dictate this action, and can lead to impairments/retardation if chemicals are low
• The brain has many kinds of immunoglobulins and chemokines, demonstrating intricate brain development
• A cell will then differentiate into a neuron, in order to form dendrites, axons, and synapses
• Synaptogenesis is the formation of synapses that begins long before birth and continues throughout life
• Neurons form new synapses and discard old ones
• Most neuron development slows in older people, as does the formation of new dendritic branches

Neuronal Birth

• It was once believed that vertebrate brains formed all their neurons in the early stages of life only modifying in adulthood
• Vertebrate brains can still generate new neurons as suggested by later researchers
• Research has shown that heart cells are more or less as old as the person
• It appears that the body only ever replaces approximately one percent of heart cells per year
• It was later confirmed that a stroke does not affect the human cortex which still forms new neurons
• The concentration of the human hippocampus indicates that 2% are replaced per year
• Replace some neurons of the parts in the caudate nucleus, putamen and nucleus accumbens
• The hippocampus and basal ganglia are important to new learning and continue releasing neurons through life

Types of Plasticity

• There are two types of plasticity occurring in a healthy brain
• Experience-expectant plasticity happens during development
• The brain then has special types of experience to develop
• A development of ocular dominance columns is an example in the visual cortex
• Experience-dependent plasticity: brain changes modify the neuronal areas that are already present
• The animal learns to depend on new experiences and their brain areas will either expand/shrink
• Topographic maps can also be affected by how certain drugs impact the brain area

Proof for Plasticity?

• One window used to observe stroke is brain plasticity
• If patients that have major brain areas still have the ability to recover and continue function, then function has been taken over by change
• It is common to use brain techniques like PET, fMRI, and TMS to repeatedly see if the cerebal is being actiavted and funtioning
• Following reviews come major conclusions If the surviving sensorimotor cortex survives a stroke, there may be improvement with time
• Hemiparesis follows the stroke
• Damaged efferent fiber tracts will still cause hemiparesis
• Activated motor areas during limb movements will require an activated large cortical area
• Particular movements can lead to activate larger motor cortex areas
• Also, even face movements may require parts associated with the hand or the limb

Stroke in Detail

• Large cortical areas are activated by the motion of the patient Also, a major issue is the parietal and premotor areas In this case major areas of activation are required for motor function and language
• The reorginization won't be restricited to only on hemishpere, there may be bilateral issue
• Performing a unilateral motor task activates the brain but strokes can increase or need more bilatieral activation

How To Understand Damage?

• Consider the patient R.L. who was in an accident and rear ended
• Had brain trauma, but the CT and MIR machines did not find problems, yet the symptoms said otherwise
• Signs are cognitive deficits or other preinjury lifestyles
• These can be tested using nuero testing

Neuropsychological Tests

• They measure how the brain of a person is working and can measure reading or learning capabilities
• Focus on clinical pscyhology
• Testing is done to address a behavior
• Intelligence and achievement assessment
• There may be issues with areas of the brain due to a specific disorder
• Anxiety and specific emotions
• They can vary depending on the situation and disorder

Clinical Testing and Assesment

The goals between clinical neuropsychology differs from that of a nuero pyschology • Can help aim what a person is capable of doing depending on their pysch • Provides acurate descriptions on where on individuals cogntive abilities • Can hep with care and rehabilitation Serial assessment • Diagnose if there are additional problems Distirbances in mild and diognostic issues Degenerative issues will occur in patients • Identfies brain trauma • There is a lack of proper orginization for a variety of reasins These tests can vary

Tests must check that patient are healthy and have no issue