what is single unit recording
recording from single neurons using one of more microelectrodes
can you accurately tell if you measuring from one cell or not?
no (hard to tell)
how is single unit recording highly invasive?
- requires direct access to the brain
- trauma to scalp and skull
- risk of infection
- insertion of electrodes ay damage brain tissue
(usually done on animals)
when would SUR may be used on humans (it has a high threshold for use)
- already entering the brain for medical reasons (ex, epilepsy relief)
- potential to address severe disability (ex, quadraplegia)
animal experiments are acceptable if: (2) (opinion)
- suffering is minimized in all experiments
- human benefits are gained which could not be obtained using other methods
animal experiments are not acceptable because: (3) (opinion)
- it causes suffering to animals
- the benefits to human being are not proven
- any benefits to human being that animals testing does provide could be produced in other ways
how does the brain machine interface work?
- what is its purpose?
- 2 microelectrode arrays are implanted into the left motor cortex of the patients brain where their hair thin electrodes detect neuron signals
- neuron signals pass to connectors, attached to the skull
- amplified signals are fed to a brain machine interface which interprets them and passes them on to the arm
- interface operates robotic arm in real time
- to bi pass the damage in the brain stem or spinal cord and get the signals out in an effective way (they read out signals from motor cortex)
4 types of recording
- intracellular: voltage clamp/current clamp, patch clamp
- extracellular: single unit recording, multicellular recording, field potentials
- in vitro versus in vivo (vivo = animals)
- anaesthetized vs awake
recorded from inside a cell
- done in animals
- manipulated the single cell
intra cellular
this is recording electromagnetic fields near those neurons to get an idea of inhibitory
post synaptic potentials (but we will focus on action potentials)
field potentials
what does single unit and multi unit recordings record?
action potentials of individual cells
what are the challenges of recording AP fro single cells
- how to find the ‘right’ neurons
2. how does this neuron relate to the other 100 billion
you can use a ____ electrode or an _____
single, array (2mm apart with 100)
reading from each electrode, neurons will be closer
to some and further form others, but in general
each electrode will recieve signals from multiple neurons and
there will be alot of overlap
- array of electrodes
ex, implanted tetrode
in multi unit recording, 6 electrodes are sunk down into brain tissue, each electrode has ____ recording sites on it, so you are getting ___ recording simultaneously from the brain
–> when you see a spike what does this mean?
- 8, 64
- could be one neurons firing but it will show up in multiple electrode readings so you have sort the data - clustering
how do you sort data from multiple unit recordings when they overlap in time and space
each neuron has its own characteristics and in slightly
different location
- you can take the height and the width of the AP and make a
plot of them
- will get a cluster of AP that had similar height and width and
a cluster of others
- can then assume the ones of similar height and width are from the same neuron
if you lesion right DLPFC what do you no longer remember?
spatial location of the right side of space
memory for spatial relationships in environment
cognitive map theory
fire when an animal is a particular location
place cells
whole body is represented roughly in the order
that it is actually in but upside down
and right and left switched as well
topographic and cortical magnification
the somatosensory cortex is right next to ______ and is roughly the same ______ organization
–> help each other
motor cortex, topographic
each hemisphere of the body controls the ________ side of the body
contralateral
neurons in the spinal cord are recieving input from?
- multiple neurons in the motor cortex as well sending signals to multiple neruons (not 1-1 relationship)
using response time to infer the content, duration, and sequencing of cognitive processes
mental chronometry
