NEURONS

cells specialized to receive and transmit information in the nervous system

each neuron has a cell body, axon and dendrites

AXON

MYELIN

TERMINAL BUTTONS

DENDRITES

SENSORY RECEPTORS

ACTION POTENTIAL

(Edgar Adrian)

neuron receives signal from environment --> information travels down the axon of that neuron to the dendrites of another neuron

measuring action potentials:

-microelectrodes pick up electrical signal

-measure the electrical wave that it emits

-the rate of firing is measued: low intensities = slow firing, high intensities = fast firing

SYNAPSE

a space between the axon of one neuron and dendrite of another

 - when the action potential reaches the end of the axon, synaptic vesicles open and release chemical neurotransmitters that cross the synapse.

neuronal communication: 

electric: Using gradients of charged ions to propagate the Action Potential down the axon

chemical: using neurotransmitters to communicated across the synapse

NEUROTRANSMITTERS

chemicals that affect the electrical signal

excitatory: increase chance neuron will fire

inhibitory: decrease chance neuron will fire

LOCALIZATION OF FUNCTION

specific functions are served by specific areas of the brain

the cerebral cortex contains mechanisms responsible for most of our cognitive functions

FRONTAL LOBE

(lobe of the cerebral cortex)

(localization of function: language)

responsible for:

reasoning and planning

language, thought, memory, motor functioing

tells you where to attend your attention 

*the frontal lobe takes information from other parts of the brain and tries to make sense of it, control*

Broca's Area : language production is impaired by damage to Broca's Area in the frontal lobe

PARIETAL LOBE

(localization of function: perception)

responsible for: touch, temperature, pain and pressure

TEMPORAL LOBE

(localization of function: perception)

responsible for: auditory and perceptual processing + language, hearing, memory, perceiving forms

ALSO in the temporal lobe:

Fusiform Face Area: (FFA) responds specifically to faces

 - damage to this area causes prosopagnosia (inability to recognize faces)

Parahippocampal Place Area (PPA): responds specifically to indoor/outdoor scenes

Extrastriate Body Area (EBA): responds specifically to pictures of bodies and body parts. 

OCCIPITAL LOBE

(localization of function: perception)

responsible for: visual processing

WERNICKE APHASIA

impacts langage comprehension and the production of meaningful language

difficulty udnerstanding spoken language but are able to produce sounds, phrases, and word sequences

while these utterances have the same rhythm as normal speech, they are not language because no information is conveyed. 

BROCA'S APHASIA

·      Impairment of language ability

·      Develop quickly as a result of head injury or stroke

·      Loss of the ability to produce language

·      Speech is difficult to initiate, non-fluent, labored, and halting

Positron Emission Tomoraphy (PET)

·      Blood flow increases in areas of the brain activated by a cognitive task

·      Radioactive tracer is injected into person’s bloodstream

·      Measures gamma ray signal emitted indirectly by a positron-emitting radionuclide tracer at each location of the brain

·      Higher signals indicate higher levels of brain activity

·      Often used in clinical oncology, i.e. medical imaging of tumors and the search for metastases

·      Tracer is trapped in any cell that takes it up, until it decays, since phosphorylated sugars, due to their ionic charge, cannot exit from the cell

·      Results in intense radiolabeling of tissues with high glucose uptake, such as the brain, the liver and most cancers

Functional Magnetic Resonance Imaging (fMRI)

MRI: magnetic resonance imaging – looks at the structure of the brain

fMRI: functional MRI – attends to specific places

the percentage of signal change tells you what function uses what part of the brain

               Subtraction Technique

         Measures brain activity before and during stimulation

                         You come up with different condition you can compare

Advantage: no radioactive tracer needed, high spatial resolution

Disadvantage: response is very slow

Event-Related Potential (ERP)

·      Neuron “firing” is an electrical event

·      Measure electrical activity on the scalp and make inferences about underlying brain activity

·      Averaged over a large number of trials to calculate ERP’s

Advantage: continuous and rapid measurements

Disadvantage: does not give precise location

Imaging Compared

·      MEG and EEG record the magnetic or electrical fluctuations that occur when a population of neurons is active

·      Excellent for measuring the time-course of neural events (on the order of milliseconds,) but generally bad at measuring where those events happen

·      PET and fMRI measure changes in the composition of blood near a neural event

Diffusion Tensor Imaging (DTI)

·      Magnetic Resonance Imaging (MRI) method which came into existence in the mid-1980s

·      It allows the mapping of the diffusion process of molecules, mainly water, in biological tissues, in vivo and non-invasively

·      Can reveal abnormalities in white matter fiber structure and provide models of brain connectivity

Synesthesia

·      Neurological condition in which stimulation of one sensory or cognitive pathway leads to automatic, involuntary experiences in a second sensory or cognitive pathway

·      Grapheme à color synthesia or color graphemic synesthesia, letters or numbers are perceived as inherently colored