Spike (action potentials) frequency adaptation, which is usually lumped together with other concepts as sensory adaption, is the progressive decrease in the number of spikes elicited in a neuron by the repeated presentation of the same sensory stimulus. Research suggests that spike frequency adaptation enhances the flow of information transmission in the brain’s sensory pathways. This is consistent with the observation that an individual becomes worse at detecting a stimulus as it’s presented repeatedly but they’re increasingly able to discriminate amongst fine differences between the similar stimuli.
Recently it’s been shown that spike frequency adaptation strongly shapes thalamic synchrony (the firing of action potentials at about the same time across thalamic neurons) and defines the timing of signal integration in the target cerebral cortex. The authors of today’s paper asked how spike frequency adaption shapes the amount and the kind of information conveyed through the thalamus to the cerebral cortex.
Today’s paper is titled “Thalamic synchrony and the adaptive gating of information flow to cortex” and was published December 2010 in Nature Neuroscience.
The research reported in today’s paper included simultaneous recordings from neurons in the rat’s whisker (vibrissae) related thalamus and cerebral cortex (barrel cortex). The research team recorded from the neurons responding to a particular whisker while they provided stimuli in a particular direction and at specified velocities. They report that spike frequency adaptation potentially enhances the rat’s ability to discriminate whisker deflection direction and velocities.
I added the qualifier “potentially” because this experiment does not include behavioral tests. They use an “ideal observer” technique that, in essence, measures the potential information conveyed by the signals. From this measure they may conclude that the information exists (or does not exist) that would enable the rodent to detect stimuli or discriminate amongst stimulus characteristics. Measures of potential information are important and useful. However, we may not finally conclude that the potential information is or is not utilized until we test the animal’s ability to carry out the detection or discrimination.
Most interesting is the research team’s observation that it is spike frequency adaptation’s effect on synchronous activity in the thalamus that is responsible for the changes in information they observed in the cerebral cortex. They show that stimulus intensity can modulate synchronous activity in the thalamus more effectively in the adapted state.
Other whisker related blog posts:
Wiggling Whiskers: Neurons in the Barrel Cortex and Object Localization
Adult Brain is Continually Modified by Experience: Demonstration in the Whisker System