How are brain-reward thresholds measured by an ICSS test?

[Lightstryk]

I'm reading a scientific article about the effects of alcohol addiction and withdrawal on brain-reward functioning in rats (file attached to this post) and am having some trouble understanding the methods used. How are brain-reward thresholds measured and monitored through ICSS? (Intracranial self-stimulation) Also, what are response latencies discussed in the experiments?

To quote the first experiment from the attached file:
"Experiment 1 Statistical analyses indicated that there were
no significant differences in the absolute baseline brain
reward thresholds or the response latencies between the
control group and the alcohol group prior to the administration
of the liquid diets or prior to any of the withdrawal
sessions (Table 1). The average alcohol intake (weeks 1–
12) was 7.3±0.3 g/kg per day. The mean blood alcohol
concentrations (BAC) on the day prior to each withdrawal
session are shown in Table 2. Introduction of the liquid
diets induced a small but significant increase in brain
reward thresholds (prior liquid diet baseline vs. withdrawal
1 baseline; Time: F1,17=5.595, p<0.03) and did not affect
the response latencies. The baseline brain reward thresholds
and the baseline response latencies remained stable from
the first withdrawal session to the fourth withdrawal
session. Throughout the experiment, the alcohol rats and
the control rats were pair-fed, and there were no differences
in the body weights of the control rats and the alcohol rats immediately prior or at the end of the liquid diet procedure
(Table 3). After a period of 3 weeks, the alcohol liquid diet
was replaced by the control diet (withdrawal session 1).
Discontinuation of the alcohol liquid diet did not affect the
brain reward thresholds (Table 4). During the withdrawal
period, the response latencies of the control rats were
slightly increased compared to those of the alcohol rats
(Table 4; Treatment: F1,17=10.904, p<0.004). After a
period of 4 weeks, the alcohol liquid diet was again
replaced by the control diet (withdrawal session 2).
Discontinuation of the alcohol liquid diet did not affect
the brain reward thresholds (Table 4). There were also no
differences between the response latencies of the control
rats and the alcohol rats during the withdrawal period
(Table 4; Time: F4,68=3.540, p<0.011). After a period of
5 weeks, the alcohol liquid diet was replaced by the control
diet (withdrawal session 3). There were no differences
between the brain reward thresholds of the control rats and
the alcohol rats during the withdrawal period (Table 4;
Time: F4,68=2.577, p<0.045). There were also no differences
between the response latencies of the control rats and
the alcohol rats during the withdrawal period. After a
period of 12 weeks, the alcohol liquid diet was replaced by
the control diet (withdrawal session 5). During this final
withdrawal period, the brain reward thresholds of the
alcohol treated rats were elevated compared to those of
the control rats (Table 4; Treatment: F1,17=7.133, p<0.016;
time: F4,68=3.940, p<0.006). These findings suggest that elevations in brain reward thresholds are only detected after a prolonged (12 weeks) period of alcohol intake. Alcohol
withdrawal did not affect the response latencies (Table 4).

If I'm not already too much of a bother, an explanation of the results would be greatly appreciated! :]

Thanks for your help!

 

[DiracPool]

Try reading the "ICSS Reward Threshold Procedure" section of this article:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2442647/pdf/nihms55668.pdf

It seems as if they are both using Kornetsky and Esposito's procedure, and I think the article I referenced explains it much better.

 

[Lightstryk]

Thanks a lot; that really helped explain the procedure. And yes, they do both use the same ICSS method.
I'm not completely clear with how they conducted each "series" of trials, but I guess I'll figure it out later (I'm tired).

Thanks again for the help!