Week 1 - Interfacing brain and body

• neural basis of vision and action questions whether we are in command of our motor actions and whether conscious decisions are the cause of our actions
• neuroscience demonstrates that our actions are driven by brain processes that unfold outside of our consciousness
• Our CNS makes decisions in almost every movement
• planning invariants include duration, path, velocity, joint angles, muscle activity and neural firing pattern
• motor invariants are stereotyped trajectories for eye and arm movements including path and velocity
• path is a sequence of positions of the hand in space whereas velocity is the time sequence along a path
• Neuromuscular junction is a connection point between a nerve and muscle, where signals from the nerve cause the muscle to contract
• our eyes can deceive us due to the resolution and energy problem
• the resolution problem is if your eyes were cameras your brain would record everything (fine details/ ambiguity) however that amount of data needed to be captured is beyond our capability. This means we're unable to capture everything as it happened
• The energy problem is that if all of the cells in the retina were active all of the time the amount of energy required would be huge. We do not have this level of energy.
• solution to these issues (compression) include only transmitting certain info, dont transmit things we don't need to react to, focus on change across space and time and focus on new information
• changes across space = only detect edges
• changes over time = only detect things that move (new objects)
• the solution to the resolution and energy problem is known as compression as you reduce the amount of information your brain and eyes are taking in and attempting to understand
• spatial inhibition is more aggressive compression with less critical information in space due to the details not having to be taken in as much
• G cells detect green at different nearby locations
• spatial inhibitors turn off cells if their like minded neighbours are active
• every g cell has a spatial neighbour linked to it
• sensory adaptation is fast coming and disappears quickly
• the brain compresses signals that stay the same over space
• encoding changes over space
• Lateral inhibition disables the spread of action potentials from excited cells (ready to fire) to neighbouring cells
• Lateral inhibition enhances the contrast between stronger and weaker signals due to preventing the spread of AP
• Spatial enhancement of contrast improves the localisation of objects
• The lateral inhibition process is the same for the retina as the skin
• Each receptive field inhibits its neighbour
• Tactile inhibition actually occurs "upstream" in the spinal cord
• dynamic range of neurons is quite low
• dynamic range of stimulus can be huge
• Senses can adapt in response to changes in the environment
• sensory adaptation useful to preserve adequate sensitivity across a wide range of input intensities
• fast or slow time course of adaptation and can reflect neural changes, mechanical relaxation or both
• 2nd compression mechanism is temporal inhibition - this is shown in after-effect illusion types where information is inhibited over time
• Temporal inhibitors turn off cells if they are active for a long time
• Adaptation is slow as it takes time to build up and fade away
• The brain compresses signals that stay the same over time
• R,G and B cells obviously detect red, green and blue things
• when looking at R cells for a while our R cells are inhibited. White is a mixture of R,G and B. After looking at R if we then looked at a white object the G and B cells respond but the R does not due to inhibition. LEads to white looking blue/ green leading to colour after effects
• Filling in mechanism demonstrated in the Brien-Cornsweet illusion where your brain is tricked into perceiving a smoother transition then what is physically present
• the stimulus intensity determines the size of action potentials