Drug Influences & Tools for Examining the Brain

● Blood-Brain Barrier (BBB)

○ A semipermeable network of tightly packed cells in the lining of the capillaries of the central nervous system. This network prevents many harmful substances including poisons, from reaching the brain or spinal cord.

■ Protects the brain from poisons, but also means that some potentially

helpful medications cannot enter the brain via the blood.

● Influences of Drugs on Neural Firing

○ In a neuron, if neurotransmitters are the

key, receptor sites are the lock.

○ Agonist drugs are a counterfeit key

■ Shaped like a real

neurotransmitter, but the fake

still gets the neuron to fire

○ Antagonist drugs are a broken key stuck

in the lock

■ Prevents the actual key from

entering the receptor site

● Agonist Drugs

○ Drugs or toxins that increase neurotransmission by either mimicking

neurotransmitter action or by blocking/delaying reuptake.

○ Mimicking

■ Alcohol mimics GABA

○ Blocking

■ Selective serotonin reuptake inhibitors (SSRIs)

■ Blocks the reuptake (meaning the serotonin stays in the synapse longer, giving it the chance to stimulate the next cell)

● Antagonist Drugs

○ Drugs or toxins that decrease neurotransmission often by binding to a receptor site in a way that does not cause the cell to fire and prevents the intended

neurotransmitter from binding to the site

○ Botulism

■ Prevents acetylcholine from entering the bloodstream — good for skin, bad for breathing.

● Methods for Studying the Brain

○ Accidents

■ Phineas Gage

○ Autopsy

■ Broca

● Paul Broca (found evidence that there is a place for language

production)

● Broca observed that a patient lost the ability to say anthing but the

word “tan” but could still understand language

● Broca found damage to a large area of the left frontal lobe in an

autopsy

● Broca’s area, frontal lobe, left side in the brain is named after him

(Creating language)

● Broca’s aphasia

○ Damage to Broca’s area results in an inability speak

language, but you can still understand.

■ Carl Wernicke

● Language comprehension region

○ Tow patients who suffered from a stroke and then could not

understand or create meaningful speech

○ Found damage to a large area of the left temporal lobe in an

autopsy

● Wernicke’s area, temporal lobe, left side, is named after him

(Understanding language and making phrases that are cohesive)

● Wernicke’s aphasia

○ Trouble understanding language or creating meaningful

sentences due to brain damage

■ Chronic Traumatic Encephalopathy (CTE)

● A chronic and degenerative brain disease that results from repeated head injuries. Only found in autopsies postmortem

○ Symptoms: Cognitive, moddo, behavioral problems that

often to not appear until many years after the injuries. CTE

can lead to neurocognitive disorders (e.g. dementia)

○ Imaging

■ Structure: techniques that allow researchers to study the physical make up of the brain

● CT or CAT (Computerized Axial Tomography)

○ An imaging method that involves taking a series of x-ray images (radiation exposure) from different angles and using a computer to combine the images into a 3D picture of the

structure of the brain.

○ CT scans are used to locate tumors and damage from blood clots or strokes

● Magnetic Resonance Imaging (MRI)

○ An imaging method that uses computer enhancement to create high-resolution images of brain anatomy from

exposure to magnetic fields and radio waves.

○ Greater detail than CT and there’s no radiation risk

○ Example: Can show brain shrinkage (enlarged ventricles) as seen in an MRI scan as a result of alcohol use disorder.

■ Functions: techniques that allow researchers to study an active working brain

● Electroencephalogram (EEG)

○ A noninvasive imaging method that is used to create

amplified recordings of electrical activity across the brain’s surface. Really only views surface activity, however.

○ Uses electrodes placed on the scalp

○ Diagnosis of epilepsy and sleep disorders

○ Sleep, dream, and cognitive research through the use of evoked potentials.

● Electrical Stimulation

○ A method that involves activating a brain region by sending a weak electrical current via an electrode to examine the

resulting impact on behavior and cognition

○ Pretty invasive, only used on animals

● Positron Emission Tomography (PET)

○ A brain imaging method that maps brain activity by

monitoring a harmless amount of short-lived radioactively

tagged glucose introduced into the brain via the blood

(metabolic process). Indicates the areas of the brain that are active during cognitive or motor tasks.

○ Used in the detection and study of brain diseases including strokes, Alzheimer’s, and Multiple Sclerosis

○ You can see different places and different functions and look at functions of even specific neurotransmitters.

● Functional Magnetic Resonance Imaging (fMRI) (does both!) ○ A brain imaging method that uses magnetic fields to produce images of brain structure and tracks blood flow to study the function of an active brain.

○ Tracks real-time brain activity by measuring oxygen level changes in the blood flow (metabolic process)

● Transcranial Magnetic Stimulation (TMS)

○ A noninvasive method that uses magnetic pulses to temporarily enhance or depress activity in targeted regions of the brain

○ The temporary blocking of impulses by TMS creates the effect of a virtual lesion and allows for the study of

lesioning in humans and animals without tissue destruction. ○ Used as a treatment method as well as a research tool.

The Brain

● The reticular formation is a series of fibres that run through the brainstem and into the forebrain. Related to arousedness (consciousness)

● Hindbrain

○ Cerebellum: Balance, fine motor skills, procedural memory (how to walk, ride a bike)

○ Medulla: Vital functions (heart rate, breathing) and some reflexes (sneezing, blinking, coughing)

○ Pons: Connects cerebellum to cortex, responsible for sleep, voluntary movement, and facial expressions

● Midbrain

○ Midbrain and hindbrain make up brain stem

● Forebrain

○ Thalamus: Sensory relay center (all senses are sent here except olfaction) that sorts sensory information and sends it to the other areas of the brain. Located in the frontal lobe.

○ Subcortical Forebrain

■ Limbic system: donut shaped group of structures including the… which collectively relate to memory (creation), learning, emotion, and motivation ● Hypothalamus: maintenance functions (hunger, thirst, stable body

temp)

● Hippocampus: Memory encoding and learning

● Amygdala

(there’s

actually two):

strong

emotions

(fear,

aggression)

■ Pituitary gland:

endocrine gland

located below the

cortex and below

the hypothalamus

Cerebrum (Synonymous with Forebrain):

the largest area of the brain including the

surface (cortex) and subcortical regions in

each of the two hemispheres. Functions

include language, complex thought,

consciousness, and sensory and motor

processing.

● Every structure has two places

(one on each hemisphere). The

corpus callosum is a group of nerve fibres that relay information between the two halves of the brain.

● Frontal lobe: cerebrum including the cortex located right behind the forehead that deal with language, planning, and higher level learning, and some places regulate motor movement

● Parietal lobe: processing somatic (touch) sensory information.

● Occipital lobe: visual processing

● Temporal lobe: auditory processing, includes the limbic system deep inside, and allows people to recognize faces

● Motor and Somatosensory homunculus: a

model of the proportion of the motor cortex

dedicated to moving each body part and sensory

cortex dedicated to souch sensation for each

part of the body is depicted by its size on the

distorted figure (bottom right

The Cerebral Cortex is a thick, wrinkled outer layer of

the brain that covers both hemispheres (it is a part of

the cerebrum). Includes the motor cortex, somatosensory cortex, auditory cortex, visual cortex, and olfactory and gustatory areas. It also contains numerous association areas for thought, language, and reasoning.

● Association Areas are the regions on the cerebral cortex that are not responsible for either sensory or motor functions that are instead related to higher level thinking including language (Broca’s area and Wernicke’s area) and reasoning

Left Brain VS Right Brain

● Left hemisphere

○ Left motor cortex controls the movement of the right half of the body, left somatosensory cortex controls the perception of touch on the right side of the body, and the left hemisphere contains most language-related functions (Broca’s and Wenicke’s areas)

● Right hemisphere

○ The right motor cortex controls the movement of the left half of the body, the right somatosensory cortex controls the perception of touch on the left side of the body, and the right hemisphere contains areas specializing in recognizing faces and emotional responses

● Split-brain Surgery

○ A procedure in which the corpus callosum is cut to treat severe epileptic seizures. There is no effect on personality or intellect and seizures were mostly eliminated. ○ In research, split-brain participants are put in front of an apparatus that presents an image to one focal point (either the left or right visual field (eye)) and flashes it. Words shown to the Left Visual Field are sent to the Right hemisphere. The right

hemisphere controls the left hand. Words or symbols shown to the Right Visual Field are sent to the left hemisphere. The left hemisphere controls the right hand. If there is a word placed in the left visual field, the image gets “stuck” in the right hemisphere, which cannot process the word because the hemisphere does not have any language association areas. Similarly, they can’t draw it with their right hand because the right hemisphere does not control the right hand.

The Adaptable Brain

Neuroplasticity: the ability of the human brain to modify itself in response to experience or repair itself after damage.

● Changes in the brain occurring as a result of learning through the strengthening or adding of synapses to neural networks.

● Changes that occur after an injury or illness in which non-damaged areas take over the functions of lost cells.

Drugs

Freud’s Theory

● Ego: Mostly conscious, makes peace between the id and the superego ● Superego: internalized ideals

● Id: unconscious energy

● Preconscious: outside awareness but accessible (what did you have for breakfast?) Consciousness: a state of awareness about one’s internal thoughts and one’s environment Altered State of Consciousness: A temporary state of awareness that differs from normal waking consciousness (sleep, meditation, drug use, daydreaming)

Unconscious: Subliminal processing that

occurs outside of awareness

Psychoactive Drugs

● Depressants: category of drugs that

decrease CNS activity that are all

agonist drugs (of dopamine or, for

opiods, endorphins).

○ Symptoms: drowsiness,

muscle relaxation, reduced

heart rate, coma, lowered

blood pressure, etc.

○ Examples: alcohol

(dopamine, serotonin, and

GABA agonist), opioids

(morphine, heroine

(endorphin and dopamine

agonist (pretends to be an endorphin), codeine), hypotics, anxiolytics, or antianxiety medications (benzodiazepines)

● Simulants: category of drugs that increases the CNS activity

○ Symptoms: alertness, euphoria, increased physical cognitive energy, reduced appetite, etc. Generally are norepinephrine and serotonin agonists

○ Examples: caffeine,

nicotine, cocaine

(dopamine agonist

(blocks reuptake to the

cell fires more)),

amphetamines,

methamphetamine,

MDMA (ecstasy)

● Hallucinogens: category of

drugs that result in distorted

sensations and perceptions.

Generally serotonin agonists.

○ Symptoms: hallucinations, mild delusions, relaxation, reduced motivation, panic ○ Examples: cannabis, LSD, mescaline (peyote), psilocybin

● Antagonist Drugs include naloxone (Narcan; endorphin antagonist used to treat opiate/narcotic overdose by not allowing the heroin stimulate the cell) or antipsychotic meds (dopamine antagonist used to treat schizophrenia by blocking dopamine transmission)

● (Drug Disorders) Drug use becomes a disorder when there are a minimum of two symptoms from any of these four areas. Mild with 2-3 symptoms, moderate with 4-5 symptoms, and severe for 6 or more

○ Substance intoxication:symptoms that are due to current use including disturbances in mood, perception, cognition, behavior

○ Substance withdrawal: substance-specific problems resulting from ending or reducing the use of the drug

Sleeping & Dreaming

Circadian rhythms: A 24 to 25 hour biological clock related to sleep and wake cycle involving changes in hormones, blood pressure and internal temperature

● The way it works: light enters the retina and sends this information to the suprachiasmatic nucleus in the hypothalamus which signals the pineal gland to stop melatonin production. The opposite happens during the night.

Sleep Cycle: The approximately 90-minute repeating pattern of NREM and REM stages that occurs during sleep. Each stage has distinctive brain wave activity.

NREM: non-rapid eye movement where dreams are less common that includes stages 1, 2, and 3 REM: sleep stage characterized by rapid eye movements where most dreams occur. EEG activity shows brain wave activity that is like an awake state (also called paradoxical sleep)

● Beta waves are for awake and alert consciousness, alpha for awake and relaxed, theta for slow regular waves of light sleep, delta for deep stage 3 sleep, and “Beta-like” REM sleep

● Stage 1 NREM: hypnagogic sensations (hallucinations, feel like you’re falling, jerking) ● Stage 2 NREM: sleep spindles (bursts of brain activity), K complexes (one spike) ● Stage 3 NREM: most dreams, sleep terrors, sleepwalking/talking

● REM: breathing and heartbeat increase, but muscles relax. Waves similar to awakeness Purposes for sleep

● Sleep evolved for protection (safety, energy conservation, we can’t see in the dark) ● Recovery (repair cells, strengthen immune system)

● Memory consolidation (key role in learning)

● Growth (pituitary releases growth hormone during sleep)

Dream Theory wish-fulfillment information-processing physiological function activation-synthesis

cognitive development

Sleep-Wake Disorders: category of disorders related to the amount or quality of sleep that cause distress and dysfunction. (Insomnia Narcolepsy (Cataplexy; linked to hypocretin) Sleep Apnea)