Unit 2: Biological Approach to Behavior

Localization of function

Localization of function

the assumption that behaviors such as aggression, hunger, attention, speech, and embarrassment are located in certain locations in the brain

Nervous system

a physiological system composed of neurons (cells) that carry out the function of communication throughout the body

Central nervous system

the spinal cord and the brain

Cortex, cerebellum, limbic system, and brain stem

the major parts of the human brain

Cortex

a layer of neurons (brain cells) that cover the outer part of the brain. The folded part that gives the brain wrinkles

responsible for higher-order and abstract thinking.

Cortex

What is the "newest" part of the human brain?

4

How many lobes is the cortex split into?

frontal lobe, parietal lobe, occipital lobe, temporal lobe

What are the 4 lobes of the cortex?

Frontal lobe

lobe of the cortex associated with reasoning, planning, thinking, decision making, voluntary actions, and complex emotions

Parietal lobe

lobe of the brain associated with movement, perception, and recognition

Occipital lobe

lobe of the brain associated with visual

Temporal lobe

lobe of the brain associated with auditory, memory, and speech

2: the left and right hemisphere

How many sections is the brain divided into?

Corpus callosum

What divides the two hemispheres of the brain?

Cerebellum

structure that sits below the brain cortex and is commonly referred to as the "little brain"

associated with movement and balance

Limbic system

evolutionarily older part of the brain located in the inner regions of the brain. Sometimes referred to as the "emotional brain"

Thalamus, hypothalamus, amygdala, hippocampus

What are the 4 structures of the limbic system?

Thalamus

mostly responsible as a sensory "relay station" for the sensory organs. Where nearly all sensory organs have nerves that connect to

Hypothalamus

just "under" the thalamus and is responsible for the functions such as emotions, thirst, and hunger

Amygdala

involved in memory, emotion, and fear

Hippocampus

important in the functions of learning, memory, and converting short-term memories into long-term memories. Spatial orientation

Brain stem

just underneath the limbic system. Controls our more "basic" functions vital for life, such as breathing and heartbeat.

connects the brain to the spinal cord and is similar to the brains of lower animals such as reptiles.

"reptile brain"

Localization- a speech "center" in the brain

What did Paul Broca's case study discover?

Louis Leborgne ("Tan") lost his ability to speak when he was only 30. He developed gangrene and was subscribed surgery performed by Broca. By the time of the surgery, all he could pronounce was the syllable "tan" and was also losing his writing abilities. He died at 51 as a result of his condition, when Broca termed the condition as "Broca's aphasia," the loss of articulated speech. Broca then conducted an autopsy of Leborgne's brain where it was discovered that a lesion in the front area of the left hemisphere had existed. The region was termed "Broca's area."

Describe Paul Broca's case study.

Carl Wernicke- the lesion was more aggressive than originally thought. He dissected the brain and discovered that the lesion had grown to the inner part of the brain.

Who elaborated Broca's study and what did he discover?

Wernicke's aphasia

characterized by the impairment of language comprehension, while the same time speech production is intact

Wilder Penfield

Canadian researcher who furthered the mapping of the brain using the method of neural stimulation

Describe Penfield's work.

Penfield treated patients with severe epilepsy by destroying nerve cells that caused seizures. He would identify these parts of the brain by stimulating them with electrical pulses and observing the responses of the patients.

Cortical homunculus

a map of sensory and motor cortex. The original models show what parts of the brain cortex control what part of the human body such as eyes, tongue, nose, etc.

Karl Lashley

looked at memory in rats after inducing brain damage.

Karl trained the rats to run a maze without errors in search of food. After the rats had learned the maze, he would remove a portion of the rat's cortex. Karl removed varying portions of the rat's cortex ranging from 10% to 50%. He would then place the rat back into the maze and observe the change in behavior.

Hypothesis: if memory is located somewhere in the brain, then removing it would pinpoint that location.

Describe Lashley's experiment.

Memory was distributed rather than localized.

What did Lashley's experiment conclude?

On what basis did Lashley conclude that memory was distributed?

The principle of mass action, equipotentiality

On what basis did Lashley conclude that memory was distributed?

Equipotentiality

one part of the cortex could take over functions of another part

Principle of Mass Action

one part of the cortex could take over functions of another part

Relative localization

some functions are localized in the brain, but it addresses the limits of localization

Lateralization

the division of the functions between left and right brain hemispheres

Roger Sperry and MIchael Gazzaniga

Who studied lateralization?

Sperry and Gazzaniga Experiment

worked with patients who had their corpus callosum cut in order to control severe epilepsy. The findings from the research demonstrated a dominance by the left hemisphere in language. The right hemisphere showed dominance in visual construction. Findings showed that lateralization is not absolutely strict.

Visual contstuction

What did Sperry and Gazzaniga's experiment discover that the right hemisphere was responsible for?

Language

What did Sperry and Gazzaniga's experiment discover that the left hemisphere was responsible for?

Lateralization is not absolutely strict. Emotional responses are not lateralized and both hemispheres can process emotions. Some parts of the brain are very localized for particular functions while some aspects are not lateralized.

What was the conclusion of Sperry and Gazzaniga's experiment?

Localized weakly

Some functions of the brain (such as memory and emotions) are...

Neuroplasticity

the changes that occur in the brain as a result of the breaking and formation of synaptic connections between neurons

Neurons

cells that make up the brain

Genetic reasons or environmental reasons , such as learning or injury

What can affect neuroplasticity?

Synaptic plasticity

observing single neuron to neuron changes

Cortical remapping

when one area of the brain assumes the function of another brain due to injury.

Activity of the neurons. The more active the neurons are, the better they are at connecting to other neurons.

What does synaptic plasticity depend on?

Are less likely to form connections

Neurons that are not activated regularly...

Wire together

Neurons that fire together...

Fail to link

Neurons that fire out of synch...

Merzenich and Colleagues

studied cortical remapping in eight adult owl monkeys

Steps of the Merzenich Study

1. Sensory inputs for all the hand digits were mapped in the monkey cortex using electrodes that were inserted into the monkeys. The researchers then stimulated the fingers of the monkeys and noted what part of the brain activated (monkeys were anesthetized).

2. The third finger of the monkey's hand was amputated.

3. After 62 days, the monkey's cortex was then remapped to see if the cortical area had changed or responded after the amputation.

Results of the Merzenich Study

The brains of the monkeys had five distinct areas of the brain that controlled their digits. After the amputation of the third digit, the regions of the cortex that controls the fourth and second digits became larger and "spread" into the region that once controlled the third digit.

Draganski et al

investigated if the brain really could reshape from environmental demands or changes.

Draganski et al experimental design

Two groups were formed using random sampling for one group and self selected for the other group. A sample of volunteers was randomly allocated into a group of jugglers or non-jugglers. Each group had no experience in juggling before the experiment. A brain scan was performed when the groups were made.

Participants in the juggling group then spent 3 months learning how to juggle with 3 balls. A brain scan was performed again after the 3 months. Participants were then told not to practice their juggling routine and a third brain scan was performed.

Results of Drananski et al

1. The brain scans before the experiment began showed no significant difference between the two groups in brain structure.

2. The second scan, after the juggling group had practiced, showed significantly more grey matter (neuron growth) particularly in the mid-temporal area of both hemispheres.

3. The temporal area is known to be involved in coordination and movement.

4. At the third brain scan, the gray matter decreased but remained higher than the original scan.

5. The study also showed there was a correlation between juggling performance and the amount of change in the brain.

6. Participants who trained more often or frequently had more significant changes.

7. Participants who trained less or failed to practice had scans that showed a reduction in brain change.

Draganski Medical Study

Draganski studied 38 medical students before and after taking exams. Researchers scanned students' brains 3 months before their examinations. The researchers then scanned brains 1 or 2 days after the exam. Researchers scanned their brains a third time, three months after the exam.

Results of the Draganski Medical Study

1. The amount of grey matter increased significantly between the first scan and the second scan. Grey matter increased particularly in the parietal cortex of both hemispheres.

2. After the exam and the 3 month rest period there was nearly no reduction of grey matter in those regions.

3. In summary, studying more had a more lasting impact on the brain than practicing juggling.

Maguire et al London Taxi Study

investigated the brains of London Taxi drivers because of their skills at navigating a complex city. The original hypothesis speculated that the hippocampus of the drivers would be different because previous studies in animals show that the hippocampus is involved in spatial abilities.

Maguire et al Experimental Design

The participants were 16 right-handed male drivers. The average years of experience for the drivers was 14.3 years and all drivers had healthy medical profiles. The control group consisted of 50 right handed males who did not drive taxis.

Results of Maguire et Al

1. The brain scans of the taxi drivers showed higher levels of brain matter in the posterior hippocampus compared to the control group who did not drive taxis.

2. However, the control group showed higher volume of grey matter in the anterior hippocampus.

3. This meant that there was no difference in hippocampus volume, but there was a significant redistribution of grey matter from anterior to posterior. In other words, brain matter had "shifted" from the front to the back of the hippocampus.

Time spent as a taxi driver and hippocampal volume. The higher the gray matter volume, the more months/years a person spent as a taxi driver.

Maguire et al (2000) looked at the correlation between...

Adapt to changes in the environment

The brain is "plastic" meaning that it can...?

Paul Bach-y-Rita

one of the first neuroscientists to introduce the idea of sense substitution

Sense substitution

the idea that other senses can take over or be used to make up for another lost sense.

Echolocation in blind humans

Example of sense substitution

Behavior is the product of physiology

The first principle of biological approach to behavior states that

Neurons

carry information from the brain and senses

The body, dendrites, axon

3 parts of the Neuron

Dendrites

receive signals from other neurons

Axons

transmit signals further on/across the neuron

Cell body

holds DNA of the neuron

Synapse/synaptic gap

location where a neuron ends and meets another neuron

Chemically and electrically: electrical signals move across neurons, but chemical signals pass between neuron to neuron at the synaptic gap

How is information in the nervous system transferred?

Threshold of excitation

the neuron must receive a "strong enough" of a signal to "fire" or carry a signal

Action potential

A brief electrical pulse generated by a neuron reaching its threshold of excitation that travels across the neuron.

Neurotransmitter

a type of chemical found in the brain that is stimulated by electrical pulses reaching the synaptic gap

It can either be destroyed (metabolized). pulled back into the synapse (reuptake), or bound to the receptors on the other neuron at the post-synaptic membrane

What happens to neurotransmitters after being released into the synaptic gap?

Excitatory neurotransmitters

travel across the synapse and create an impulse in the adjacent neuron. Stimulate the brain

Inhibitory neurotransmitters

stop impulses, or prevent neurotransmitters from crossing the synapse. These produce calming effects in the brain.

Agonists

chemicals that increase or encourage the action of neurotransmitters

Antagonists

chemicals that prevent or inhibit a neurotransmitter from being passed on

SSRIs

selective serotonin reuptake inhibitors, type of antagonist

Serotonin

inhibitory neurotransmitter that is responsible for maintaining a balanced mood and regulating sleep

Biological factors

Neurotransmitters are based on...

Crockett et al Experimental Design

A sample of 30 healthy subjects was recruited (mean age 26). The individuals were split into two groups, one was given citalopram (a highly selective SSRI) in order to boost the concentration of serotonin in the synapses. The second group was given a placebo.

After taking the drug, the participants were given a series of moral dilemmas. Participants had to choose between utilitarian outcomes (saving 5 lives) and aversive harmful actions (killing an innocent person). Aversive actions were divided into personal actions (such as pushing a man off a bride to save 5 lives) or impersonal ones (pressing a lever to move a train off a track, killing 5 people).

Crockett et al results

1. Responses in the impersonal version were unaffected by citalopram.

2. People who took citalopram were less likely to push the man off the bridge in the personal scenario than participants in the placebo.

3. In other words, normal (placebo) people were against pushing the person off the bridge, but individuals who took citalopram were significantly more "against" pushing the person off the bridge.

Serotonin produces prosocial behavior because they were less willing to accept personal harm which promotes personal behavior.

Crockett et al Conclusion

Dopamine

excitatory neurotransmitter that has been linked to motivation, reward, and pleasure centers and regulated emotional responses.

Fisher, Aron, and Brown (2005)

studied neural mechanisms of romantic love

Fisher, Aron, Brown Experimental Design

Through word of mouth and recruiting via flyers, 10 men and 7 women were recruited. Everyone had been in a relationship of "intense love" for at least 7 months. Participants in this study were not dating each other. Participants were then scanned using a functional magnetic resonance imaging (fMRI).

Participants were shown pictures of their loved one for 30 seconds. Participants were then asked to count back from a given number for 40 seconds. Participants were then shown an emotionally neutral acquaintance for 30 seconds. Participants were then asked to count back from a given number for 20 seconds.

These steps were repeated 6 times. Total procedure time: 720 seconds.

Fisher, Aron, Brown Results

1. When patients saw images of their loved one, there was a significant increase in activity in the Ventral Tegmental Area (VTA) and caudate nucleus. These areas are known to be dopamine rich and form the dopaminergic pathway.

Dopaminergic Pathway

system in the brain that produces and transports dopamine throughout the brain. reward system because dopaminergic activity has been shown to be associated with motivation and feelings of pleasure.

Parkinson's disease

degenerative disease that degrades the motor functions of the nervous system. Symptoms: shaking, rigidity, difficulty moving and walking. Cognitive ability and behavioral problems occur.

Freed et al

studied the relationship between dopamine and Parkinson's disease

Freed et al Experimental Design

A sample of 40 patients who were 34-75 years old and had severe Parkinson's disease, were taken. The mean length of time with Parkinson's was 14 years. The patients were divided into two groups: a transplant group which received a transplant of nerve cells and a control group which underwent a mock surgery.

For the experimental group, the dopamine-producing nerve cells were inserted into the putamen via holes drilled through the frontal none via long needles. Patients who received the mock surgery just had holes drilled in the skull, but never penetrated the membrane surrounding the brain.

To ensure uniformity and reduce bias

Why did Freed et al drill holes into the heads of all of the participants?