Tools in Neuroscience Research

Question 1

what are the common ways that we design an experiment in behavioural neuroscience to infer the relationship between brain and behaviour?

Answer 1

• induce a loss of function - deliberately disrupt functioning in brain, expect to see disruption in behaviour, understand behaviour
  
  • lesions, turning off brain areas, using neurotransmitters
• induce a gain of function - increase functioning, expect to see increase in behaviour
  
  • is trickier to turn up a brain area than to turn it down
  • increase activity can cause things like seizures
• monitor behaviour and brain activity simultaneously - brain imaging is correlational

Question 2

what is the main difficulty in conducting experiments in behavioural neuroscience?

Answer 2

sometimes a true experiment isn’t feasible - can’t always have a true independent variable

• studying people who have addictions, we can’t control who is addicted

Question 3

what do we mean when we say there’s no one ideal method to answer a question in neuroscience?

Answer 3

usually have major trade-offs in terms of time-scales, spacial-scales, and overall noise/recording sensitivity

Question 4

how is fMRI in terms of time and spacial scales?

Answer 4

• fMRI - records on the order of seconds, so every snapshot is capturing hundreds of thousands of action potentials
  
  • action potentials are on the order of milliseconds
  • fMRI operates at 1mm cubed voxels on the spacial scale - 13 million neurons
  • pretty good resolution but are capturing activity of a million neurons in a voxel (doesn’t go small enough)
  • but can capture larger scale behaviour and has good coverage across the brain

Question 5

how is a single electrode in terms of time and spacial scales?

Answer 5

• single electrode - records extremely fast, have small (good) temporal resolution (sub-milliseconds)
  
  • better at capturing action potentials and EPSPs
  • at the spacial level they’re also good because they can measure single neurons
  • downside is that we can’t infer what is happening in other neurons by just looking at one

Question 6

what are the ways that we can record the brain’s electrical activity?

Answer 6

• single-cell recording
• electroencephalography (EEG)
• event-related potentials (ERP)

Question 7

how do we use single-cell recordings?

Answer 7

• record with two electrodes, one on the inside of the cell (intracellular) and another on the outside (extracellular)
• can be challenging to put one electrode inside and another outside so close to each other in the brain
  
  • we can compare one electrode to a “ground” (something neutral)
• if the electrode landed inside the cell - baseline is negative, it will flip into positive during AP
  
  • very rare
• if the electrode landed outside the cell - baseline is positive, it will flip into negative during AP

Question 8

how do we interpret single cell recordings of electrical brain activity?

Answer 8

using raster plots
- shows neuronal firing patterns in relation to specific behaviors
- each time a behavior occurs, it is marked in the brain recording
- events are synchronized to the time of the behavior, allowing clear comparisons of APs
- some neurons fire more around certain behaviors in one context but not in another
- helps identify which behaviors specific neurons are active for

Question 9

what is the idea of population coding?

Answer 9

• population coding - many neurons encode for a complex stimuli
  
  • no one neuron is responsible for a single behaviour
  • some neurons fire more for certain things, but population coding is the norm
  • take all recordings of context vs. situations and examine the pattern

Question 10

what is convergence?

Answer 10

• convergence - when multiple neurons or sensory inputs send their signals to a single neuron
  
  • integration allows the brain to combine information from various sources, enhancing the precision and reliability of the signal that reaches the target neuron
  • crucial for sensory processing and decision making

Question 11

what is divergence?

Answer 11

• divergence - where a single neuron’s signal is distributed to multiple neurons
  
  • allows information to be shared broadly across different areas, enabling the same signal to have widespread effects
  • crucial for motor control and sensory distribution

Question 12

what is parallel processing?

Answer 12

• parallel processing - different brain areas processes different send signals in a bunch of different directions (divergence), process all at once, and then bring it all together (signal converges)
  
  • way of getting around limitations of speed in our brain

Question 13

what is the idea of distributed representations?

Answer 13

• distributed representations - visual world is represented in different parts of the brain
  
  • another of way of saying population coding

Question 14

what is the idea of the grandmother cell?

Answer 14

• grandmother cell - old idea that we cannot have a single cell that represents our grandmother, because…
  
  1. grandmother has complicated aspects (their appearance, their smell, memories associated with them)
  2. if we only had one cells and that cell was destroyed, then the whole memory of grandma would be gone

Question 15

what is the halle berry neuron?

Answer 15

• a specific type of neuron discovered in the medial temporal lobe of the human brain
• neuron was found to fire selectively in response to images of actress Halle Berry, as well as the written or spoken name “Halle Berry.”
• suggests that the brain encodes abstract concepts, like a person’s identity, in specific neurons
• we also call them concept neurons
• neuron responds to a very specific concept or individual, not just visual features like shape or color
• high convergence in the brain, neuron integrates diverse inputs, like visual and auditory information, into a unified conceptual response
• important for re-activating patterns of activity across the brain

Question 16

what are the two main limitations to directly recording electrical activity?

Answer 16

1. getting more electrodes into the brain
   
   • putting in a lot of electrodes can limit free movement and impact data collection
   • can put single electrodes that have multiple sensors vertically stacked
2. making sense of tremendous amounts of data
   
   • harder to understand and track multiple variables across time and space

Question 17

what is electroencephalography (EEG)?

Answer 17

• electrodes measure brain voltage from the scalp
  
  • measuring brain areas on the outside of the cortex
  • use an amplifier to turn up the activity so we can detect it

Question 18

what are the characteristics of waves measured by EEG?

Answer 18

• waves have both a frequency and amplitude
  
  • frequency - how fast the waves are, number of voltage fluctuations per second
  • amplitude - how big the waves are
• frequency is measured in Hz (cycles/second)
• see a bunch of different types of waves, can be differentiated with computers

Question 19

what are the different categories of waves?

Answer 19

• usually categorized based on frequency
  
  • high frequency - alpha (8-12Hz), beta(12-30Hz), gamma (26-100Hz)
  • low frequency - theta (waking and sleeping, 4-7Hz), delta (0-3Hz)
• general patterns of waves gives an idea about the general states that a person is in
  
  • useful in tracking sleep

Question 20

what do sleep phases look like?

Answer 20

• during wakefulness we have a lot of alpha, beta, and gamma
• as we slip into non-rem sleep, we see theta first and then delta
• can use waves to see what state of sleep people are in
• REM sleep - the body looks asleep, but brain has lots of alpha and beta waves

Question 21

other than EEG, what do we do to measure sleep phases?

Answer 21

• EMG - electromyograms used to measure electrodes on muscles to give baseline level of muscle tone
  
  • body becomes basically paralyzed in REM sleep
• EOG - electrooculogram used to measure muscles around the eyes
  
  • REM is called rapid eye movement

Question 22

what type of activity are EEG waves measuring?

Answer 22

• measure electrodes in the rats brain and electrodes on the outside of the head
  
  • found that EEGs more likely represent post-synaptic potentials more than action potentials
• we are measuring activity, not necessarily action potentials
• in our cortex, the axon of our pyramidal cells is the deepest/furthest from the outer surface

Question 23

how do we know if brain waves are synchronized? which phases have more and which have less synchrony?

Answer 23

• waves are consistent, so they show us population synchrony
• we have higher amplitude signals when neurons are firing together (synchronized)
• delta - slower, higher amplitude waves (more synchronization)
  
  • neurons don’t fire much, but when they do, they fire at the same time
• gamma/alpha/beta - have smaller amplitude, fire less as we fall into sleep but become more synchronized

Question 24

what do the different types of waves tell us about consciousness?

Answer 24

• alpha/beta - conscious brain activity
• theta ripple - may be when we transition from one sleep state to another
  
  • result of activity in the medial temporal lobe
  • related to learning and memory, also related to the halle berry neuron
• delta - was unclear before, but new ideas suggest they’re related to sleep
  
  • when people lose out on a night’s sleep, the biggest rebound is in the amount of delta they get

Question 25

what are gamma waves related to?

Answer 25

• we think gamma is related to information processing, diverting attention to a task/problem
  
  • people think they’re related to what we’re consciously aware of and focusing on
• probably related to a higher level of cognition

Question 26

what was the relationship between gamma waves and meditation? why does this happen?

Answer 26

• highest amplitude gamma was recorded during meditation
  
  • gamma changes with skill level of meditation
  • buddhist monks had the highest amplitude gamma waves
• rhythm/synchrony likely mediated by fast-spiking, GABAergic interneurons
  
  • interneurons are responsible for synchronizing in the brain
  • neurons that are most related to gamma waves are GABA interneurons

Question 27

what are event-related potentials (ERPs)?

Answer 27

• taking the average response to a stimulus
• idea is to make someone do something multiple times
  
  • the more times you do it, the smoother the average becomes
  • until you start to see waves that show up during the tasks
• waves correlate with some aspects of cognition and behaviour
  
  • when you write down a word, waves correlate with whether or not you will remember the word