Question

Imagine that two groups of neurons (A&B) send their signals to another group of neurons (C) Action potentials generated simultaneously by all the neurons of group A lead to a response in C such that a select number of neurons in group C are activated ( number of activated neurons = C1); action potentials generated simultaneously by all the neurons of group B lead to a response in C such that C2 is the number of activated neurons. What might the magnitude of the response be in C if action potentials were generated simultaneously by all the neurons in both groups A & B? Can it be bigger than, smaller than, or equal to ( C1+ C2)? Why?

Answer 1

Hello,
To understand this, let us first consider some basic concepts.
1. Action potentials follow all or none law, that is, their magnitude remains the same irrespective of the stimulus.
2. C1 and C2 are not necessarily completely exclusive of each other. What this mean is that, A and B might be stimulating some common neurons amongst group C neurons.

So, suppose C group contains 12 neurons. Now, A group neurons stimulate 1 to 7 neurons; and B group stimulates 5 to 12 neurons. Here, 5,6 and 7 are common for both. As a result, when both A and B will fire simultaneously all 12 neurons will fire, but this is less than the sum of 7 of A and 7 of B. Therefore magnitude here is less.

Now suppose A stimulated 1 to 6 neurons of C and B stmilated 7 to 12 neurons of C. If simulation of A and B were to occur simultaneously, all 12 neurons of C will get stimulated. Here, the sum of individual stimulation of A and that of B is equal.

But, the sum of individual stimulation of A and B, can never exceed individual stimulations. Because no matter what, extra neurons within C bundle will never be stimulated.

Hope I helped
Thank you
Ask any doubt in comments.

Answer 2

The magnitude of the response in group C when action potentials are generated simultaneously by all the neurons in both groups A and B can be either bigger than, smaller than, or equal to the sum of the individual responses C1 + C2, depending on the specific neural circuitry and connections involved.

1. Bigger than C1 + C2: If the neurons in groups A and B converge onto a common set of neurons in group C and these neurons exhibit strong excitatory interactions, then simultaneous activation of both groups A and B can lead to a synergistic effect. In this case, the combined activation may result in more neurons being activated in group C than the simple sum of C1 + C2.

2. Smaller than C1 + C2: Conversely, if the neurons in groups A and B converge onto a common set of neurons in group C, but these neurons exhibit inhibitory interactions or competitive interactions, then simultaneous activation of both groups A and B may lead to cancellation or competition between the two signals. As a result, the number of neurons activated in group C may be less than the sum of C1 + C2.

3. Equal to C1 + C2: In some cases, the simultaneous activation of groups A and B might have no additional effect on the response in group C compared to the individual responses C1 and C2. This can occur if the neurons in groups A and B project to separate and non-overlapping sets of neurons in group C or if their interactions balance each other out.

Ultimately, the outcome depends on the specific wiring and synaptic connections between the neurons in groups A, B, and C. The complexity of neural circuits and the presence of excitatory and inhibitory connections make it challenging to predict the exact magnitude of the response in group C without detailed knowledge of the underlying neural architecture and network properties.