psyc 3354 (neuro) - test 1

cognitive neuroscience

field of science that strives to understand the ways in which the brain influences how people think, feel and act (relationship btwn brain and mind)

-comprises investigations of how mental functions are linked to neural processes

-much of the early work comes from human neuropsychology that examined cognitive and emotional deficits in those with brain damage

cognitive neuroscientists

integrate findings from diff approaches to try to understand the relationship btwn brain and mind

ex brain imaging (fmri, etc), computer models, lab studies and clinical findings

-view the brain as an information processing system whose primary goal is to solve problems

dendritic tree

Part of the neuron that receives input from other cells.

Neurons

cells in the nervous system that communicate with one cells in the nervous system that communicate with one another to perform information-processing tasks by means of chemical and electrical signals

-connected through synapses which can be excitatory or inhibitory

3 main parts: dendritic tree, cell body, axon

another to perform information-processing tasks by means of chemical and electrical signals

-connected through synapses which can be excitatory or inhibitory

3 main parts: dendritic tree, cell body, axon

cell body

contains nucleus and other cellular apparatuses responsible for protein and enzyme manufacturing

Axon

the extension of a neuron, ending in branching terminal fibers, through which messages pass to other neurons or to muscles or glands

-can be very short (barely longer than dendrites) or very large (spanning distances btwn brain regions)

glia

support cells, influence communication btwn neurons by modifying chem environment, refine and sculpt physical connections, aid with recognition after brain damage by removing dead neurons, and serve nutritive needs and structural support

-guide neurons from site of creation to final position in brain

-also critical to maintaining BBB

blood-brain barrier

physical barrier preventing, toxins, nutrients, drugs and immune sys cells from reaching NS

-glia maintain- tightly packed glial cells between blood vessels and neurons

Myelination

the process by which axons become coated with myelin, a fatty substance that speeds the transmission of electrical signals

Nodes of Ranvier

gaps in the myelin sheath, allows for saltatory propagation (jumping APs- fast)

Oligodendrocytes

Type of glial cell in the CNS that wrap axons in a myelin sheath.

Schwann cells

Supporting cells of the peripheral nervous system responsible for the formation of myelin.

excitatory postsynaptic potential (EPSP)

a slight depolarization (makes more positive) of a postsynaptic cell, bringing the membrane potential of that cell closer to the threshold for an action potential

-happens when presynaptic neuron is excitatory

-increases probability that neurons will fire

inhibitory postsynaptic potential (IPSP)

temporary hyperpolarization of a membrane

axon hillock

where action potential begins

-near cell body

refractory period

a period of inactivity after a neuron has fired

-neurons can only fire so fast

Action Potential (AP)

What occurs when postsynaptic neuron has enough potential to reach threshold?

How postsynaptic potentials differ from action potentials?

-they are graded (the further they travel, the more they dissipate), where APs remain constant

-smaller magnitude than APs (bc they are small and dissipate, unlikely that one iwll cause a cell to fire- requires a few)

-postsynaptic can be excitatory or inhibitory, APs always excitatory (make cell fire)

Depolarization

resting potential gets closer to 0

Hyperpolarization

membrane potential becomes more negative (further from threshold)

-goes below resting

Repolarization

return to resting potential after depolarization

front of brain

anterior/rostral

back of brain

posterior/caudal

top of brain

dorsal/superior

bottom of brain

ventral/inferior

middle of brain

medial

towards outside of brain

lateral

brain sliced ear to ear to separate front from back

coronal

brain sliced to separate top from bottom

horizontal (also called axial or transverse)

brain sliced to separate left from right

sagittal

sagittal slice down middle of brain

midsagittal (or medial) section

sagittal slice to one side

lateral section

contralateral

opposite side

ipsilateral

same side

unilateral

one-sided

bilateral

both sides

Proximal

near

Distal

Farther from the trunk of the body

ex distal mucles in hands

Central Nervous System (CNS)

brain and spinal cord

-encased in bone because of fragility (brain in skull, sc in spinal column)

Peripheral Nervous System (PNS)

all neural tissue outside the CNS

cerebrospinal fluid (CSF)

between neurons and other bony encasements, similar composition to blood plasma

ventricles

fluid filled spaces in the brain, contain CSF

-lateral ventricles most prominent

seven main subdivisions of the central nervous system

1. spinal cord

2. medulla

3. cerebellum

4.pons

5. midbrain

6. hypothalamus and thalamus (diencephalon)

7. cerebral cortex

spinal cord

-comes up through spinal column

-portion of NS through which most sensory neurons relay info to the brain and through which motor commands from brain are sent to muscles

-first point of connection is to brainstem

medulla

the base of the brainstem (directly superior to sc); controls heartbeat and breathing so damage can be fatal

-contains many (not all) of the cell bodies of the 12 cranial nerves

-home to part of a set of neurons called reticular activating system (RAS)- receive input form cranial nerves and project to many other brain regions, important in arousal and regulation of sleep-wake cycle

Cerebellum

-important for regulation of muscle tone and motor activity, damage results in interference with precision of mvmt and disrupts balance/equilibrium

-cauliflower looking

-classic test to check for cerebellum damage is touch your nose then drs- will be able to do it but roughly and imprecise

pons

part of brainstem, superior to medulla and anterior to cerebellum

-acts as main connective bridge from rest of brain to cerebellum, and point of connection btwn most cranial nerves and brain

-important control centre for eye mvmts and vestibular functions (i.e balance)

-site of superior olive

midbrain

part of brainstem between diencephalon and pons

-contains nuclei of cells that form some of the cranial nerves

-contains two important structures on dorsal side: inferior colliculus and superior colliculus- plays role in orientating us to stimuli in auditory and visual modalities, respectively

hypothalamus

a neural structure lying below the thalamus; directs eating, drinking, body temperature; helps govern the endocrine system via the pituitary gland, and is linked to emotion

-homeostasis, also has intimate relationship with hormonal system

-forms diencephalon with thalamus

Thalamus

large relay center for almost all sensory info coming into cortex and almost all motor info leaving it

-forms diencephalon with hypothalamus

relay center

a brain region in which the neurons from one area of the brain synapse onto neurons that then go on to synapse somewhere else in the brain

-thalamus

basal ganglia

-important for motor control

-contains caudate nucleus, putamen, globus pallidus, and nucleus accumbens

-located near thalamus

-parkinsons and dopamine related to bg

-damage to globus pallidus leads to involuntary twisting and turning of limbs

-damage to caudate nucleus and putamen causes involuntary movements such as tremors while person is at rest

limbic system

-important for emotions

-contains amygdala, hypothalamus, anterior thalamus, cingulate cortex, mamillary body and hippocampus

-all structures inside the brain

cerebral cortex

primary role in many functions such as object recognition, spatial processing, and attention

-divided into two halves- cerebral hemispheres which differ in function and anatomy

gyrus (gyri)

convexity (bump) in the cortex

-allows us to pack more brain tissue into a smaller space

sulcus (sulci)

depression or groove in the surface of the cerebral cortex; fissure- deep

central fissure (Rolandic)

separates each brain hemisphere in an anterior-posterior dimension

-frontal lobe in front of this

-parietal directly behind central, but above sylvanian

Sylvanian/Lateral Fissure

separates each hemisphere of the brain in a dorsal-ventral dimension

-temporal lobe below

-parietal directly behind central, but above sylvanian

longitudinal fissure

separates left and right hemispheres

white matter

consists of myelinated axons- fatty hence why it shows white

gray matter

Brain and spinal cord tissue that appears gray with the naked eye; consists mainly of neuronal cell bodies (nuclei) and lacks myelinated axons.

lateral geniculate nucleus (LGN)

A structure in the back of thalamus(hence lateral),

-important in vision

medial geniculate nucleus (MGN)

section of the thalamus

-important for auditory

hypothalamic-pituitary-adrenal (HPA) axis

a body system involved in stress responses

hypothalamic pituitary gonadal (HPG) axis

involves reproductive hormones

major white matter tracts

association fibers, commissural fibers and projection fibers

association fibers

white matter tracts that connect one part of a specific brain region to another brain region in the same hemisphere

commissural fibers

interhemispheric, travel from hemisphere to the other, left to right or right to left. Most prominent commissural fiber bundle is the corpus callosum.

projection fibers

defined by moving from one level of the nervous system to another level of the nervous system. For example connection of cerebral cortex to brain stem

neurotransmitters

the chemicals that neurons release that allow them to communicate with one another

different aspects of neural transmission are influenced by the type of neurotransmitter

amino acids

major class of NT found throughout the CNS

glutamate and GABA

Glutamate has an excitory effect and

GABA (gamma-aminobutyric acid) has an inhibitory effect

second major class of nt

neurons are organized into system that each are produced then project to specific brain regions

four neurotransmitter systems

cholinergic, dopaminergic, noradrenergic and serotonergic

cholinergic system

Responsible for synthesizing and distributing acetylcholine (ACH)

Synthesizes from Basal Forebrain and PDT

Responsible for general cortical excitability

linked to production of REM

implicated in attention (vigilan and memory

implicated in Alzheimer's

also skeletal muscle

dopaminergic system

Responsible for synthesizing and distributing dopamine (DA)

consist of three subsystems

Nigrostriatal - cell bodies in substantia nigra, important in motor control

Mesolimbic - cell bodies in ventral tegmental area, linked to reward-related control

Mesocortical - VTA, influence various functions, including working memory

Loss of Dopamine - Role in Parkinson's

Increases - Related to schizophrenia

noradrenergic system

Emits Noradrenaline (NA)

originates primarily in the locus coeruleus

influences arousal and attention,

also. linked to both short term and long term aspects of memory processing.

implicated in major depression and mania

serotonergic system

Releases Serotonin (5HT)

cell bodies in the raphe nuclei of the midbrain, pons, and medulla

project to hypothalamus, hippocampus, and amygdala as well as to the striatum, cortex, cerebellum, and thalamus.

influences a large variety of behaviors, including sleep, mood, sexual behavior, eating, and memory

some of the most popular drugs to treat depression are serotonin specific reuptake inhibitors (SSRIs)

Roman Galen

noticed that gladiators with injury to the head or brain did not retain power of thought

inferred that the brain was linked to the mind

Paul Broca

provided evidence that a particular region of the brain is critical in language processing

led to the concept of localization of function

localization of function

specific brain regions are responsible for specific mental functions

20th Century - Heyday of the Lesion Method

The lesion method allows scientists to make inferences about what function a brain region performs from observing what behaviors are compromised or absent after damage to that region is sustained.

Scientists made many important linkages between the brain and behavior in their interactions with many veterans of the two World Wars, especially those who had sustained missile wounds. X-rays showing damaged areas of the skull suggested, by extension, damage to brain regions below.

Lesion Method: An Example

Brenda Milner and colleagues discovered the critical role of the hippocampus in memory

preformed planned lesion

excision of regions in and around the hippocampus is associated with difficulties in forming new long-term memories

also excision of other brain regions (frontal lobe) did not lead to such memory difficulties

planned lesion

unilateral surgical removal of portions of the temporal lobe as treatment for epilepsy

Single Case Lesion Methods

Strengths

Provides invaluable insights, such as HM who was able to be tested for over 30 years on the role of the temporal lobe in memory

Weakness

Cannot generalize patterns, left-handers have a neural organization for cognitive function distinct from right handers

Overcoming weakness

Group studies with patients with brain damage who have similar characteristics

Can be "messy" due to the people within the group being quite heterogenous along a number of dimensions

Scientists use a multiple-case-study approach to deal with heterogeneity

Multiple-case study approach

Determine average behaviour across the group

Determine the variability within the group

Also, examine the relationship between a cognitive deficit and a factor of interest

Hemispheric Specialization: Split-brain Studies

Because the hemispheres were surgically isolated from one another, split-brain studies allowed researchers to test the competency of each hemisphere in isolation.

Researchers found that only the left hemisphere could verbally name objects and pictures, while the right hemisphere could demonstrate its knowledge of objects by using them correctly or by pointing

Animal Studies: Single-cell recordings

In single-cell recordings, the tip of an electrode, which is otherwise insulated, is placed in contact with the cell

The tip of another insulated electrode serves a reference

After establishing a baseline firing rate for a given cell, researchers then determine what properties of a stimulus make the cell fire maximally above that baseline (e.g., light, movement, etc.)

This information is fed into an amplifier

The activity is output on a computer monitor that show the size of the electrical activity overtime.

Microelectrode Methods

Microelectrodes are inserted directly into

brain areas of awake rats, monkeys, cats,

and people.

Action, and local field, potentials are

measured during ongoing cognitive

processes

Strengths

Direct measure of neural activity, highly specific, high sampling rate

Weaknesses

Invasive - Small samples, confined to only hospitals that also do research, involves a special population - research findings might not generalize to people without epilepsy

The 1980s and 90s: Anatomical Methods

Computerized Axial Tomography (CAT, or CT)

• Derivative of x-rays. Dense tissue such as bone

appears white, whereas less dense material, such as

cerebrospinal fluid (CSF), appears black.

• Regions of the brain that were damaged long ago

appear darker than surrounding tissue as they are

filled with CSF.

• Regions where a hemorrhage has recently occurred

appear lighter, as blood is denser than brain tissue

Quicker than MRIs, use X Rays rather than a magnet

Invention of this method enabled standardized bra alases, which could be used to co-register damage across patients and link damage in a given area across individuals to similarities in behavioural deficits

neural psychology

studies brain damage and mental function

what is measured by psychologists in studies to infer cognitive function?

reaction time and accuracy

might see preserved accuracy but changes in reaction. time depending on task

Magnetic Resonance Imaging (MRI)

"provides the ability to examine both brain anatomy and brain function without the use of ionizing radiation, which vastly expanded the questions and populations that could be examined with brain imaging. Moreover, it provided greater anatomical resolution than CAT scans and greater temporal resolution than PET studies, and as such has become a mainstay of cognitive neuroscience research."

Positron Emission Tomography (PET) (80s and 90s)

"uses the decay of a radioactive isotope introduced into the brain, typically either glucose or oxygen, to examine brain metabolism. Areas of the brain that are particularly active will take up more of the isotope and provide a greater signal. The use of PET allowed researchers for the first time to record activity from specific brain regions in response to cognitive and emotional demands, thus showing the neurologically normal brain in action."

levels where we can gather information for the brain

Neuroanatomical

Neurochemical

Neurophysiological

In parallel, different aspects of behavior can be assessed in distinct populations ofi ndividuals

Cognitive neuroscientists must consider how the information they gather is influenced by the choice of a particular population and a particular method.

Each choice biases the researcher toward observing some aspects of functioning and notothers.

method of converging operations

Researchers aim to gather information on the same question by using a variety of methods with a variety of population

multilevel and multimodal approaches

These approaches involve using multiple tools intandem.• In some cases, researchers combine information from two measures derived from the same acquisition technique

e.g., Structural MRI provides information on brain anatomy

Functional MRI provides information on brain function

In other cases, researchers combine information from two measures that have differing strengths and are complimentary•

e.g., Functional MRI to provide information on where in the brain activity is occurring

ERPs to provide information on when that activity is occurring Multilevel and multimodal approaches

Techniques for analyzing behaviour: Assessment of behaviour in brain-damaged populations

One approach is to use a standardized neuropsychological test battery

While fixed batteries allow direct comparisons, a one size fits all approach isn't always best in non-typical cases.

A more recent trend is towards a more customized and flexible battery

Typically consist of tasks designed to assess core competencies

Memory, visuospatial abilities, language, psychomotor speed and attention andexecutive/goal-oriented functions.

And consist of tasks designed to tap abilities that rely on different regions ofthe brain.Techniques for analysing behaviour

Assessment of behavior in brain-damaged populations• A neuropsychological battery will often contain measures of intelligence

Most widely used measures of intelligence are the Wechsler family of intelligence tests that include:• All consist of about a dozen subtests, leading to an overall IQ score as well as subscale scores

Certain abilities can be relatively unaffected by brain damage and are used to obtain an

estimate of premorbid functioning - a reasonable guess as to how well the person was performing before the injury

MRI - How it works

MRI machines create a constant magnetic field

Perturbations in this field are induced

The response of the atoms in the brain is used to derive maps of brain structure and function.

Tissues vary in hydrogen concentration (e.g., CSF, myelin, skull, white/grey matter)

MRI - Strengths and Weaknesses

Strengths

Generally easily accessible to researchers, most powerful tool for researchers

Weaknesses

Not everyone can undergo an MRI scan. People with pacemakers or metal parts in their body cannot have an MRI taken