Lecture 4: Essentials Neural Coding

What are spike trains?

Sequences of Action Potentials

What are the main topics of neural coding?

1. Statistic models of spike trains

2. Measuring Firing Rates

3. Reverse correlation analysis

What do measurements of neural responses look like? How do they vayr based on where they are collected from?

EPSPs and IPSPs are ____ signals.

analog

How is neural data processed?

Raw Data → Filtered Data → Spike Train

What is the neural response function?

Spike trains can be modeled as a _____ process.

Poisson

In Poisson process, what does Spike Count corrspond to? How about Inter-Spike Interval?

Spike count: Poisson Distribution

Inter-Spike Interval: Exponential Distribution

_____ periods modify the Poisson process model

Refractory

The randomness of a spike train can be measured by ____ ___ _____

“coefficient of variation (CV)”

How to simulate a Poisson Process?

General Method:

If u is a random variable of uniform distribution [0, 1], and F(t) is the

probability distribution function of random variable τ, then

w=F-1(u) is a random variable with probability distribution function F(t).

What is the best measure of spike train?

Inter-Spike Interval (ISI) Histogram

____ _____ ____ (or ____ _____ ____) is a function of the time window used in the calculation.

Average discharge rate (or mean firing rate)

Spikes trains encode the information about a sensory stimulus

in the form of ____ or __ ____ pattern

Spikes trains encode the information about a sensory stimulus

in the form of discharge rate or temporal discharge pattern

What is discharge rate?

How many spikes per unit of tim

How to make a period histogram?

Diff between Period and Peristimulus Histogram?

Period histogram starting reference is beginning of period, while PSTH is the beginning of the recording.

What is phase-locking?

Phase locking is a process where neurons synchronize their electrical firing (spikes) to a specific phase or point of a repeating external wave, such as a sound wave. [1]

Instead of firing randomly, a neuron will fire action potentials at the exact same part of the cycle over and over again. It usually does not fire on every single cycle, but when it does fire, it locks into that specific timing

What is used to ensure the measured phase locking is statistically significant?

Circular Statistics

Why does Phase Locking Matter for Neural Coding?

Phase locking matters for neural coding because it allows neurons to represent the precise timing of sensory stimuli rather than just their overall firing rate

Phase-locking in a spike train can be quantified by

_____ _____ (___ ___)

Phase-locking in a spike train can be quantified by

synchronization index (vector strength)

What is Reverse Correlation

Reverse correlation is another name for calculating the spike-triggered average (STA). It is a powerful data-analysis method used in neuroscience to figure out what kind of sensory input makes a neuron fire an electrical impulse, or spike.

Normally, an experimenter controls a stimulus and watches how the neuron reacts. Reverse correlation does the opposite (hence "reverse"): it looks at the output (the spikes) and works backward to see what the input looked like right before the spike happened. [1, 2]