Imagine Magazine - Johns Hopkins - May/June 2016 - (Page 47)
by Timothy Boester, Ph.D.
Neuron Activation Level
Neurons transmit information electrochemically. When the soma, or cell body, of the
neuron switches from being inactive (grey circle) to being active (yellow circle),
the neuron transmits a signal down the axon, and then to other neurons at synapses
(arrows). These other neurons may or may not become active, depending upon their
receptor activation threshold.
A neuron with a positive (white numbered circle) activation threshold needs to receive
a signal from a certain number of other neurons for itself to become active. Thus, a
neuron with a +1 activation threshold requires at least one active synapse, while a +3
activation threshold requires at least three active synapses.
A neuron with a negative (black numbered circle) activation threshold needs a lack
of inhibitor signal from a certain number of other neurons for itself to become active.
In other words, it needs a certain number of synaptic connections to inactive neurons
to become active. Thus, a neuron with a -1 activation threshold requires at least
one inactive synapse, while a -3 activation threshold requires at least three inactive
The maximum activation threshold (positive or negative) for a neuron is equal to the
number of incoming synaptic connections (arrows pointing to it). No neurons have an
activation threshold of 0.
In this puzzle, you are given a set of neurons in one or more activation states. You need
to determine how to assign the available receptor activation thresholds to the neurons
in the bottom row so that the neurons behave as given. The same arrangement of
activation thresholds must work for both activation states given.
Solution for Knossos Games 23.4
Tim Boester is an educational
psychologist who studies how
people learn math. He has
more puzzles available at
Table of Contents for the Digital Edition of Imagine Magazine - Johns Hopkins - May/June 2016
In My Own Words Karl Deisseroth, Professor of Bioengineering and of Psychiatry, Stanford University
Mind Brain Philosophy and neuroscience at CTY
A Meeting of the Minds at the National Brain Bee
Mind over Matter Overcoming communication barriers via technology
A Fish of a Different Color My neuroscience internship
Immersed in Brain Science Summer research at Rockefeller University
Brain Training Four graduate students share their research
Prime Time for Brain Science Exciting new findings, from brain maps to mindfulness
Making the Connection Teaching kids about mind, media, and health
Selected Opportunities and Resources
Pitch Perfect The lure of rugby
My Stress-Free Adventure Scuba, sailing, and discovery
Off the Shelf Review of Kazuo Ishiguro’s The Buried Giant
Exploring Career Options Interview with neuropsychologist
One Step Ahead Ten commandments for college success
Planning Ahead for College Can your dream school become a reality?
Students Review New York University
Creative Minds Imagine Fiction contest winners
Mark Your Calendar
Mind + Brain Philosophy and neuroscience at CTY
Imagine Magazine - Johns Hopkins - May/June 2016