Module A - Brain machine interface Flashcards
Describe the observations from the 1870 study by Fritsch and Hitzig on stimulation of the cortex:
Electric excitability of the cerebellum in dogs and observations from battlefield open head wounds
1. Motor cortex was responsible for motor control
2. Areas of cortex connected to specific muscles
Limitation: Not very well localised
Describe the observations from the 1954 study by Wilder Penfield on mapping by stimulation:
Mechanisms of voluntary movement
Epilepsy study of proving different parts of the brain
Overlapping areas not well defined but recorded motor homunculus
Describe the observations from the 1968 study by Evarts on neural activity and force:
Relation of pyramidal tract activity to force exerted during voluntary movement
Single cell firing encodes force of contraction (neurons behave like muscles)
Describe Evarts observations on muscles with no load:
Flexors don’t fire during extension and fire during flexion (tonic EMG)
Extensors fire during extension and don’t fire during flexion (tonic discharge)
CTN active with agonist muscle
Describe Evarts observations on muscles with flexor load:
Flexors fire during flexion with increased firing rate and tonic discharge
Extensors don’t fire
CTN activity increases with increased load
Describe Evarts observations on muscles with extensor load:
Flexors don’t fire
Extensors fire during extension and fire at the end of flexion to hold against the load
No CTN activity because flexion movement results from relaxation of antagonist
Describe the observations from the 1983 study by Georgopoulos on neural activity and direction:
The relations between 2D arm movements and cell discharge in the primate motor cortex
Neurons represent direction (neurons fire when the arm moves in a particular direction, not in response to force)
Describe the directionality of firing and preferred directions:
Maximal firing rate occurs in a neurons preferred direction
What does the following equation calculate:
Firing rate=baseline + modulation depth (movement direction-preferred direction)
Predicts the max firing rate of neurons
Describe the observations from the 1988 study by Swchartz on preferred directions in 3D:
Primate motor cortex and free arm movements
Populations of neurons in preferred directions are uniformly distributed in space (all directions equally represented)
Describe the observations from the 1988 study by Georgopoulos on the population vector algorithm:
Coding of the direction of movement by a neuronal population
Take an average vector to give population vector which always points in the direction but have different firing rates
This depends on knowing scaling factor beforehand to normalise firing rate
Describe the certainty of the PVA:
Certainty detected by bootstrapping to form a confidence cone around the preferred direction vector
Calculate the preferred direction from random combinations of neurons activity from the multiple trials’ recording
Do this 100 times and report angle encompassing 95% of the resulting
A smaller angle and tighter confidence cone is desirable
Describe the 4 parameters of the PVA:
Normalised (firing rate, baseline, modulation depth)
Smoothened
Pooled (preferred direction)
Integrated
Describe the observations of the 1999 study by Kaheri, Hoffman and Strick on muscles and direction:
Monkey can move hand up/down in 3 wrist conformations
Substantial group of M1 neurons displayed changes in actvity that were muscle-like, and an even larger group displayed change sin activity that were related to change sin actual wrist movements in space (independent of muscle activity generated)
Both muscles and direction strongly represented in M1
Describe the other considerations (regions) needed to be taken into account during the muscles vs direction argument:
Primary motor cortex Supplementary motor area Premotor cortex Dorsolateral prefrontal association cortex Somatosensory cortex Posterior parietal cortex (area 5 + 7)
