Inferior Temrporal Cortex
train a classifier on the neural output activity
predict the class from that output activity
nearest neighbor classifier based on correlation coefficient
what information is present in a particular area, and when is it present?
how is that information represented?
sample stimulus category
decision stimulus category
can we rejuvenate by transplanting brains?
can we combine human brains and robot bodies?
head transplant - feasible today, result would be quadriplegia; rejection drugs allow this, BCI allows better quality of life
brain transplant - theoretically possible; fewer rejection problems, BCI essential; classical "brain in a box"
partial brain transplant - easier or harder, requires stem cells
brain ages and deteriorates
it's unknown whether this is intrinsic to the brain or caused primarily by the body
it's unknown how much the brain is dependent on a functioning body (e.g., for stem cells)
the brain is divided into areas with highly specific and conserved functions
the brain itself is composed of neurons; each neuron operates both chemically and electrically, and these electrical activities can be recorded and stimulated
electrical activity in the motor cortex generates signals that are conducted via nerves to muscles
light arriving in the eye generates nerve signals that travel to the visual cortex and are processed there
brain and nervous system anatomy is extremely complicated and sensitive
things that sound nice theoretically ("let's interface directly with the brain") are messy, risky, and complicated
there is a big need for brain computer interfaes for the disabled
brain surgery has made enormous advances
Utah electrode array
problems, inflammation due to friction and stiffness (insertion requires stiffness), inflammation due to unnatural materials, limited density, limited spatial resolution, fixed geometry, multiple neural targets (more a problem for stimulation than recording), transcutaneous connections, power, etc.
solutions, biocompatible surface coatings, stiffness during insertion with biodegradable matrix
ECOG arm, ECOG background
process, electrodes are hooked up to motor areas (the same areas that control muscles), human learns to generate the necessary control signals similar to learning a regular motor skill
status, experimental, costly, stationary, functional, potentially useful, other potential application: electronic bridging of severed spinal cord
auditory, cochlear implant, brainstem implant, process, fairly easy mapping of sounds into electrical signals, status, routine, high quality perception possible
visual, retinal implants, cortical implant, process, difficult, manual mapping of cortical locations to spatial locations, (how does this happen naturally?), status, highly experimental, poor quality, no real perception, but still useful
measures correlated synaptic activity of post-synaptic potentials in the cortex
high temporal resolution
delta waves - slow-wave sleep, attention (4 Hz)
theta waves - idle (4-8 Hz)
alpha waves - relaxation (8-13 Hz)
beta waves - alertness (13-30 Hz)
gamma waves - complex perceptual tasks (30 Hz and higher)
irregular - transient effects, states; epilepsy
generally, collection of signals from many channels
each channel is a different mixture of multiple sources
problem: "blind source separation"
solution: ICA (independent component analysis), assuming statistical independence of the different components
pure brain-based interfaces