How the brain works quiz 2

Luigii Galvani

Discovered animal electrcity by an electric spark hit from a metal surgical tool attached to nerve in frog leg

Gustav Fritsch and Eduard Hitzig

Used a dog brain to stimulate brain movement, mid/front of brain: leg movement, back of brain; no effect due to muscle contraction via motor nerves (motor cortex)

Walter Hess

Used cat brain to stimulate different behaviors: rage, fear, sniff, pant, eat; hypothalamus regulates homeostasis and coordinates behaviors needed for survival

Epilepsy

Sudden uncontrollable increase in brain activity in the cerebral cortex; activity spreads uncontrolled to the rest of the brain

Wilder Penfield

Used technique to map the function of the human brain; patient is fully conscious during procedure, patients describe what they are experiencing after each brain region

Motor homunculus

Motor cortex (pre-central gyrus), stimulation = body movement; contralateral response: right brain: left body, left brain: right body, motor control represnted in larger brain area (face, fingers)

Sensory homunculus

Sensory cortex (post-central gyrus), stimulation = body sensation (touch, tickle, itch, pain); contralateral lresponse, highly sensitive parts of body represnted by larger brain area

Auditory cortex

Temporal lobe; stimulation = non recognizeable sounds

Visual cortex

Occipital lobe; stimulation = flashes of light, no distinct images because of organized activation of dorsal and ventral streams

Temporal lobe

Stimulation = experimental and interpretive response; reliving past experiences with very vivid memory flashbacks or sudden change in interpretation of current experiences

Deja vu

New seems familiar

Jamais vu

Familiar becomes strange

Transcranial magnetic stimulation (TMS)

Non-invasive way to induce electrical stimulation of the brain using strong magnetic fields; high: increase brain activity (treatment for depression, does not cause epilepsy), low: decrease brain activity (treatment for schizophrenia)

Deep brain stimulation

Invasive technique to implant electrodes semi-permanently into particular brain regions (treats depression, parkinson’s disease, epilepsy)

Electrical stimulation and recording

Stimulation: stimulate location electrically to observe behavioral effects; recording: observe electrical events that correlate to behavior

Electrial recording

Stimulating the brain electrically through electrodes can induce motor behavior or sensory effects; different behavioral or cognitive brain states should correlate with different patterns of electrical activity

Electroencephalography (EEG)

Developed by Hans Berger; 20-60 electrodes are placed on scalp and recordings for 20-30 minutes, must pass skull and skin; signals are detected by produced synchronous activity in brain regions

Brain waves

Electrical signals produced by synchronous activity in large networks of the brain are read by the EEG as waves with varying frequency and amplitude, including delta, theta, alpha, beta, and gamma waves

Frequency

number of peaks per second (Hertz or Hz)

Amplitude

height of the peaks, indication of how strong the signal is

Complex brain waves

Sum of combination of frequencies and amplitudes

Alpha frequency range

High frequency fast wave activity (8-13 Hz)

Beta frequency range

HIgh frequency fast wave activity (13-30 Hz)

Theta frequency range

Low frequency slow wave activity (4-7 Hz)

Delta frequency range

Low frequency slow wave activity (1-3 Hz)

EEG Waves correlate with behavioral states

Beta (alert), Alpha (relaxed), Theta (drowsy), Delta (deep sleep)

REM sleep: dreaming stage

Stage where no muscle tone, no movement (except eyes), inhibitory signals from brainstem block muscle activity, hallucinating brain in a paralyzed body

Rapid eye movement (REM)

State where eye movement controlled by cranial nerve III; body muscles controlled through the spinal cord and spinal nerves, 70-95% of dreams occur; The “paradoxical state”: EEG resembles awake state, yet you are asleep and dreaming

Slow-wave sleep

No thoughts or normal everyday thoughts (10% claim dreams) EEG: low frequency, high amplitude, Decreased muscle tone, but still able to move; Sleep walking appears to occur

Parasomnias: groups of sleep disorders

Non - REM sleep parasomnias: Sleep terror, Sleep walking, Confusional arousals; REM sleep parasomnias: Nightmare disorder, REM sleep behavior disorder, Recurrent isolated sleep paralysis

REM sleep behavior disorder

• In REM sleep behavior disorder, the paralysis that normally occurs during REM sleep is incomplete or absent 

• People can “act out” dreams, particularly those that are vivid, intense, and violent

Sleep paralysis

• Flip side of REM sleep behavior disorder

• Muscle paralysis (or atonia, lack of muscle tone) occurs either before sleep begins, or persists after sleep ends

Basal (ventral) forebrain:

Promotes slow wave sleep (deep sleep) in the hypothalamus,  lesion in this region can produce insomnia

Part of the hypothalamus

Coordinates other sleep centers, regulating orderly stages of sleep

Brainstem

Contains reticular formation, activates and stimulates the brain to promote wakefulness

Subcoeruleus (small region in the brainstem)

Activates parts of the brain to promote REM sleep 

Sleep is important for

Conservation of metabolic energy, consolidation of memory in long-term storage, clearance of toxins from the brain

Using EEG to determine brain functions

Exposes subject to some kind of sensory stimulus, read brain waves occurring in a subject

• Changes are called evoked potentials (EPs) or event-related potentials

  • (“potential” refers to change in voltage=electricity)

• One, called the P300, is seen when the subject sees something familiar, but unexpected in that context

The EEG technique advantages

• Non-Invasive, can test living, talking human subjects 

• Inexpensive compared to other methods

• Very fast, excellent temporal (time) resolution

The EEG technique disadvantages

• Not very sensitive as signal is very small

• Can not detect activity in all parts of the brain

  • Only the cortex because it is close to the surface 

• Cannot localize a given brain wave pattern to which part of the brain is active 

  • Poor spatial resolution

EEG techniques also measure

• Blood flow

• Brain oxygen levels OR

• Brain glucose levels

Positron Emission Tomography (PET)

• Inject a radioactive form of glucose into the bloodstream (fluorodeoxyglucose)

• The fluorine isotope decays and releases a positron (the antimatter version of an electron)

• Distribution of this positron emission can be imaged by a computer; provides measure of glucose utilization in the brain

Functional Magnetic Resonance Imaging (fMRI)

• Does not require any injections or radioactivity

• Uses signals given off naturally by iron atoms in the blood’s hemoglobin to measure use of oxygen by the brain

• Change in magnetization of oxygen-rich vs. oxygen-poor blood

• Best resolution, least invasive

Function of fMRI

• Areas that “light up” are not the only active regions

• Entire brain is active all of the time

• Blue or red areas are those whose blood flow changes when given a task

3 hypothesized components to love

• The drive (lust, libido)

• Attraction (romantic love, being in love, infatuation)

• Attachment (pair bonding, long term stable relationship)

Headaches

• pain or discomfort located in the head

  • Primary: occurs independently

  • Secondary: byproduct of another condition

  • Localized nociceptive event

Migraines

• a distinct, chronic neurological disorder

  • Head pain is only one feature, can be absent in some patients

  • Systemic brain disorder

Migraines pt 2.

• Can have a genetic component

• Can consist of moderate to severe headaches

  • Typically unilateral

• Nausea

• Heighted (hypersensitivity) response to light and sound, etc.

• Last hours to days, recurrent

• May have an “aura”

  • Visual, sensory, or neurological warning signs before the onset of the migraine

fMRI can show

Cortical Spreading Depression in migraines - a wave of electrophysiology hyperactivity followed by a wave of inhibition

• Implicated in migraine auras

  • Can be seen as spreading of a wave of vasoconstriction following vasodilation and prolonged sustained vasoconstrictions

Reductionist approach advantages

• Can understand actual mechanisms

• Critical to fixing problems

• Use animal models

• Utilize broad range of techniques

Reductionist approach disadvantages

• Difficult to study humans

• Can be difficult “to see the forest for the trees”

• Not clear how individual components work together to result in a whole complex

The light microscope

• One or more convex lenses in a tube

• Allows magnification of up to 1000-fold

• Leeuwenhoek built a microscope and applied microscopy to biology

Robert Hooke and identification of cellular structure

• Also constructed a microscope

• Viewed cell structure in a thin slice of pork 

• Thought he saw cells in a monastery

Cell theory of Schleiden and Schwann

• All living matter is made of cells and products of cells

• Cell is the most elementary unit that can contain life

• All cells come from other cells

• Cell is surrounded by plasma membrane that separates it from the environment

• All cells have similar chemical composition with organelles that perform specific function

How can we see brain cells in the microscope?

• First: must fix the tissue

  • Brain is soft, must be hardened for cutting or freezing

  • Prevent tissue from rotting

• Second: must section the tissue

  • Make thin slices; millionths of a meter

  • Transparent and hard to see

• Third: must stain these sections

  • Different stains stick to different organelles and reveal overall structure, cell types, and even individual molecules

Nucleus

Contains DNA (genes); transcription of DNA into messenger RNA

Ribosomes

transcribe messenger RNA into proteins (translates gene code to protein code) located on the rough endoplasmic reticulum

Organelle

Each is specialized for a particular task

The Nissl Stain

• Stain reveals cell bodies organized into SIX layers in the cerebral cortex

  • Stains rough endoplasmic reticulum 

• Different stains give different patterns

  • Weigert or Weil Stain

  • Labels the fatty insulation found on many nerve fibers called myelin - white matter

Stains for gray matter

Nissl stain: cell bodies (darker) fiber tracts (lighter)

Stains for white matter

Weil stain: cell bodies (lighter), fiber tracts (darker)

Bordmann areas defined by Nissl stain

• Defined 50 brain area with different “cytoarchitecture” revealed with Nissl stain

• Saw layers and clusters of neurons called nuclei (in the CNS) or GANGLIA (in the PNS)

Camillo Golgi

• Created the Golgi stain “the black reaction”, filled a few % of all neurons revealing their true shape

• Labels a random subset of neurons, but outlines them completely (fibers AND cell bodies)

Dendrites

• Shorter, thicker/tapering, many of them, more branches to the cell body

• Recieve and integrate nerve impulses

Axons

• Longer, thinner/untapered, only one per neuron, fewer branches on the cell body

• Transmit nerve impulses to terminals

Cell body

Gene expression and protein production

Synpases

Release neurotransmitters to activate electrical and chemical changes in connected neurons

Brainbow

Genes for jellyfish and coral proteins that glow under various light wavelengths that can be inserted into the mouse genome to make fluorescent neurons

Nervous system to neuronal function

• Acquire information from the external (and internal) environment

  • Sensory signals must enter the CNS

• Produce behavior based on information

  • Motor signals must leave CNC to contact muscles

Nervous system to neuronal function pt.2

• Input and output is performed through axons called “nerves” in the PNS and “tracts” white matter in the CNS

• Bundle of axons arising from neurons in ganglia (clusters of neurons in the PNS) or within the CNS

Sensory neuron

• Detect specific stimuli in the environment

• Carry that information into the CNS via. Axons

  • Cell bodies lie in the periphery (PNS)

  • Detector can be a specialized sensory organ (tongue, nose, eye) or a free nerve ending (skin, internal organs)

Dorsal root ganglia (DRG)

• Contains cell bodies of somatosensory neurons (touch, tickle, itch, pain, etc.)

• Neurons have a fiber that goes to the periphery and one that provides input to the cord

Motor neurons

• Sends motor signals to muscles that regulate their contraction

• Spinal motor neurons have cell bodies in ventral cord

• Sends axons out the ventral roots to the skeletal muscles

Interneurons

• Contained in 97% of the CNS

• Cell bodies and axons/dendrites lie entirely within the CNS

• Perform analysis of sensory signals and initiate behavioral decision making