Biological - The Brain Flashcards
What are the major divisions of the brain?
Forebrain, midbrain, hindbrain.
*Forebrain: hemispheres,
limbic system, thalamus,
hypothalamus.
- Midbrain
- Hindbrain: cerebellum,
pons, medulla.
Describe the brain stem.
Upper brainstem: (forebrain) thalamus, hypothalamus.
Lower brainstem: midbrain
hindbrain (without cerebellum)
pons, medulla.
What is the function of the brain stem?
*Transmits information from and to the brain;
*Responsible for simple reflexive behaviour;
*Physiological states.
Describe the features of the hindbrain.
▪ Medulla (an extension of spinal cord)
– controls vital reflexes (heart rate, circulation,
respiration, salivation, coughing, sneezing)
▪ Pons (Latin: bridge) –axonal projections cross sides, i.e., become contralateral. Takes part in body balance, vision, and auditory processing. Contains centres related to sleep & arousal.
▪ Cerebellum – controls fine motor skills, coordination & balance
– Plays a role in motor learning
– Cognitive functions of attention and
language
Describe the features of the midbrain.
▪ The midbrain is located at the top of the brain stem and contains
structures that have secondary roles in vision, audition and movement
– The superior colliculi help guide eye movements and fixation of gaze
– The inferior colliculi help sound localisation
– The substantia nigra plays a role in reward, addiction, projects to the
basal ganglia to integrate movements (a dopamine-containing
pathway implicated in Parkinson’s disease)
- tectum (roof), tegmentum (covering)
Where are the thalamus and hypothalamus located and what’s their function?
In the upper brain stem.
▪ Thalamus – relays and processes information from sensory organs
(except olfaction) and transmits it to the cortex.
▪ Hypothalamus – regulates body temperature, hunger, thirst and
sexual behaviour (autonomic NS)
What are the brain lobes?
Frontal lobe:
▪ Important for movement and high
cognition
– the primary motor cortex
– Broca’s area: speech
production
▪ Prefrontal cortex
– plays a role in planning,
decision making, impulse
control
– adjusts behavior in response
to rewards and punishments
▪ Prefrontal lobe dysfunction:
– impaired ability to learn from
consequences & to control
impulses
– often found in depression
and schizophrenia
Parietal lobe:
▪ The parietal lobes are important for body sensations and spatial
localization
▪ The primary somatosensory cortex (the postcentral gyrus)
* receives information about the skin senses, body position, and
movement & maps these functions as a sensory homunculus
▪ Parietal association areas (inferior & superior parietal lobules +
precuneus)
* combines information from body senses and vision;
* identifies objects by touch, determine the location of the
limbs, and locate objects in space
* complex language processing
Occipital lobe:
▪ Hosts the primary visual cortex (V1) (aka striate cortex due to its striped
appearance in cross-section)
– Destruction in the striate cortex causes cortical blindness in the related part of the visual field
▪ Other visual areas that process individual components of a scene, including color, movement, and form.
Temporal lobe:
▪ The auditory cortex, which receives information from the ear
▪ Language and auditory and visual association areas
– Wernicke’s area: language comprehension and production. Damage results in meaningless speech and poor written and spoken
comprehension.
– Inferior temporal cortex: visual identification. Damage causes difficulty in recognizing objects and familiar faces (prosopagnosia).
Phineas Gage.
▪ In 1848 Phineas Gage, a 25-year-old
American railroad construction worker , survived an accident in which a large iron rod was driven completely through his
left cheek and out of his skull
– Gage was left with no speech,
movement, intelligence or learning
impairment
– The injury changed his personality and behaviour
→ link between a specific brain area and emotional behaviuor
Define the following:
Fissure, Sulcus, Gyrus.
*Gyrus (pl gyri) – a protuberance on a surface of the brain (a hill).
*Sulcus (pl. Sulci) – a fold that separates one gyrus from another (a valley).
*Fissure – a long, deep sulcus.
What is the primary cortex?
Area of the cortex responsible for the first stage of sensory processing. Receives inputs from lower structures (mainly thalamus). Sends
projections to higher level areas.
What are Brodmann areas?
- Map of brain based on its cytoarchitecture.
- Korbinian Broadmann (1868-1918), a German neurologist, distinguished 52 cortical areas via a cytoarchitectural analysis.
Eg
*1,2,3 – primary somatosensory cortex
*17 – primary visual cortex
*41,41 – primary auditory cortex
What is the secondary cortex?
Area of the cortex responsible for the second stage of sensory processing. Receives inputs from primary cortex.
*Analysis of the meaning of the stimulus.
What is the associative cortex?
Advanced stages of sensory information processing, multisensory integration, or sensorimotor integration.
What are the functions of cortex?
- Analysis of perceptual inputs
- Organization of movements
- “Higher” cognitive functions
Where is the basal ganglia located and what does it do?
Forebrain, sub-cortical.
Basal ganglia (the caudate nucleus,
putamen & globus pallidus) –
participates in planning behaviour
and emotional expression,
abundant connections with
prefrontal cortex. Direct intentional
movements
– undersupply of dopamine in BG in
Parkinson’s disease
Where is the limbic system located and what does it do?
Forebrain, sub-cortical.
▪ Hippocampus – creation of
new memories (learning) &
integration of new memories
into stable knowledge
▪ Amygdala – emotional
behaviour & formation of
emotional memories
▪ Cingulate cortex - linking
behavioral outcomes to
motivation & learning (critical
in depression & schizophrenia)
▪ Sometimes hypothalamus is
included as well
How were post mortem studies used to investigate the nervous system?
- Postmortem studies (19th & 20th century)
- Investigation of general anatomy
- Microscopic investigation of brain tissue
- brains of healthy individuals (to learn about brain structure) and of people with health issues (to
establish brain-function relationship) - Structural imagining (clinical and research application).
- Relationship between brain damage and loss of function.
Eg Damage to Broca’s area
in the left frontal lobe - area responsible for speech.
▪ Postmortem microscopic analysis of neural tissue –
How is the nervous system investigated in vivo?
▪ Structural Imaging – in vivo
▪ detailed brain anatomy of living people!
– Computerized tomography (CT scan)
– Magnetic resonance imaging (MRI)
How do CT scans work and pros/cons?
FOR STRUCTURE
▪ Computerized Tomography
- X-ray machine rotates around the
head taking multiple X-ray images from different angles.
- X-rays pass through the brain and
are absorbed in different amounts by
different types of tissue.
- Detectors measure the X-rays: After
passing through the brain, the X-rays
are detected by sensors on the other
side of the head.
- Computer creates images: A
computer processes all the data from
the detectors and combines it to create a detailed, cross-sectional image (or “slice”) of the brain (can be put together to form a 3D image).
– A contrast dye may be injected into the blood for better contrast (not compulsory).
Without contrast: A standard CT scan can show basic structures
of the brain (the skull, brain tissue, and large blood vessels). It is
useful for detecting issues like brain bleeding, fractures, or large
tumors.
With contrast: highlights blood vessels, tumors, and areas with
abnormal tissue, facilitating identification of specific issues like
tumors, infections, or vascular abnormalities.
▪ Advantages
- Fast and cost-effective
▪ Disadvantages
- X-ray exposure
- Less detailed than other methods (MRI)
How do MRI scans work and pros/cons?
FOR STRUCTURE
▪ MRI (magnetic resonance imaging):
Magnetic Field:
* The MRI machine generates a very strong magnetic field that causes the protons (hydrogen atoms in H2O) to align with the magnetic field.
Radio Waves:
* The MRI machine sends a pulse of radio waves, they disturb the alignment of the protons in the tissues of the brain. When the radio pulse stops, the protons return to
their original alignment.
Signal Detection:
* As the protons realign themselves, they send out signals, which are detected by the MRI machine. The way they realign (and the strength of the signals) depends on the
type of tissue.
Image Creation:
* A computer processes these signals and creates a detailed, cross-sectional image of the brain.
▪ imaging method to study
white matter tracts
▪ measuring the direction of diffusion
of water molecules (water diffusion in
the brain tends to track along bundles of white matter fibres).
▪ Advantages
- No X-ray exposure
- Great spatial resolution
▪ Disadvantages
- Expensive and time consuming
How do EEGs work and pros/cons?
▪ electrical brain activity measured on the scalp in living people (active, asleep or in coma).
– sensitive to postsynaptic dendritic
currents generated by a population of neurons that are active in synchrony.
▪ Advantages
- Excellent temporal resolution (< 1 ms)
- Inexpensive, accesible
▪ Disadvantages
- Poor spatial resolution (scalp signal is a sum of signals from different brain sources whose locations are difficult to infer)
Describe single cell recordings.
Neuron behavior can be
examined through microelectrodes
▪ Records electrical activity of a single neuron (but doesn’t stimulate it).
What is ERP?
EEG activity time-locked to an external event (e.g. sound, visual signal, response etc)
– averaged across multiple occurrences of the same event to reduce noise
▪ ERP peak direction (positive, negative), amplitude and timing used to investigate brain processes in different cognitive domains.
What is MEG?
Magnetoencephalography (MEG)–
recording of magnetic fields produced by electrical currents in the brain using arrays of SQUIDs (superconducting quantum
interference devices).
+ signal unaffected by skull, good spatial resolution,
- expensive, limited availability.
What is functional imaging?
▪ Functional imaging measures changes related
to neuronal activity
▪ Indirect energy consumption
▪ Functional imaging methods:
▪ Functional Magnetic Resonance Imaging (fMRI)
▪ Positron Emission Tomography (PET)
How does fMRI work and pros/cons?
▪ Functional Magnetic Resonance Imaging
▪ Structure measurement: MRI
▪ Activated neurons requires more oxygen.
▪ blood flow increases to the active brain region, and the oxygen level in the blood goes up.
▪ fMRI detects this change in oxygen levels in the blood using a method
called BOLD (Blood Oxygenation Level Dependent) imaging (Oxygen-rich blood has slightly different magnetic properties compared to oxygen-poor blood).
▪ Computer creates detailed images of brain activity plotted against
structural MRI pictures. Active areas of the brain appear brighter on the fMRI scan.
▪ Advantages
- Excellent spatial resolution
▪ Disadvantages
- Poor temporal resolution
- Very expensive
- Discomfort
- Susceptible to artifacts (head shape, movement)
How does PET work and pros/cons?
▪ Measures brain activity, local blood flow, and metabolism.
▪ Injection of a Tracer (a small amount of radioactive material) into
bloodstream (usually glucose)
▪ Emission of Energy: As the tracer breaks down (radioactive decay), it emits positrons (antielectrons). When these positrons meet electrons, they cancel each other out, radiating energy (gamma rays).
▪ The PET scanner detects gamma rays and creates detailed images
based on where the tracer has been used most (is accumulated).
▪ Advantages
- Can be used to study neurotransmitter systems
(radioactive tracers can be designed to bind specifically to certain neurotransmitter receptors)
- Sensitive to subtle changes
▪ Disadvantages
- Radiation exposure
- Low spatial / temporal resolution
- Expensive / limited availability
- Discomfort
How does modern brain stimulation work?
▪ Examination of effects of
stimulating selected brain areas
– In healthy participants (non-
invasive): transcranial magnetic
stimulation (TMS) Neurons are
excited/inhibited by externally
applied time-varying
electromagnetic fields generated
by a coil located above the head.
What causes epilepsy and how can it be intervened?
Large electrical discharge in
focal area then spreads
throughout the brain.
Generalized, Grand Mal drop
seizures are potentially
dangerous as they can lead to
further injuries.
Surgical intervention ->
separation of the brain
hemispheres
What is each brain hemisphere specialised for?
Left Hemisphere
Speech and Language
Problem Solving
Arithmetic
Local processing
Right Hemisphere
Visuospatial Abilities
Perceptual Grouping
Face Processing
Global processing
What do Wernicke’s and Broca’s area do, and where are they located?
- understand spoken language -
Wernicke’s area in the temporal
lobe, close to the auditory
cortex - speaking - Broca’s area in -
frontal lobe
