- The insular cortex is thought to be involved in compassion and empathy, taste, perception, motor control, self-awareness, cognitive functioning, and interpersonal experience. In this paper, the focus is its role in substance abuse. Which of these is not mentioned by the authors in explaining the link between the insular cortex and drug-seeking behaviors?
lesions in the insular cortex interrupt drug-seeking behaviors
individuals with substance abuse history showed reduced activity in the insular cortex
there are no drug-related receptors in the insular cortex
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the anterior agranular insula subregion contains dopamine and opioid receptors
- The authors used 35 day old rats because
35 days is adolescent, when initial drug exposure occurs often in humans
35 days corresponds to the age at which rats in the wild begin buying drugs
Rats do not develop an insular cortex until 30 days
The rat brain has no insular cortex so it doesn’t matter
- How did limited and extended intravenous self-administration training differ?
- Did pressing the lever during a test result in a predictable delivery of cocaine or an unpredictable dose? Why do you think it was done this way?
- Did cocaine-seeking behaviors increase or decrease on withdrawal day 45, relative to withdrawal day 1? Did this effect depend on the amount or duration of prior cocaine use (that is, limited or extended)?
- An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls; this is an essential part of neuron signaling.
What is meant by rise time, decay time, half‐amplitude duration , and amplitude of action potentials?
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- How are the rise time, decay time, half‐amplitude duration, and amplitude of action potentials in pyramidal neurons of the insular cortex affected by cocaine training?
- When a depolarizing current is injected into a nerve cell, the resultant decrease in the membrane potential activates voltage-dependent Na+ channels. The activation of the Na+ channels in turn accelerates the depolarization process, producing the rising phase of the action potential.
This causes the neuron to fire, or spike.
Injecting depolarizing current is done to assess whether the sensitivity of a neuron is changed by a procedure (which would be measurable as a change in the spike rate of the neuron).
In this paper, would you say that cocaine administration was shown to alter the sensitivity of insula pyramidal neurons to stimulation? Why or why not?
- For any given neuron, there is also a threshold of action potential. What does that mean?
- Is the action potential threshold shown to be changed by limited or extended cocaine training? How do you know this?
- It is generally thought that extended drug exposure has more robust effects on drug‐seeking and drug‐taking behaviors than limited use. Does this study support or contradict this bit of conventional wisdom? How?
- In this model, rats learn that pressing a lever is rewarded with an injection of cocaine. However, some rats with a history of extended training seem not to press the lever. What might explain this?
- What is the main difference (as the authors describe it) between the methods of this study and those of other rat cocaine studies?