The disturbing sleep deprivation (SD) on learning remains a controversial issue in the study of animal behavior. Previous scholars have reported on the matter of SD impairment on subsequent learning. For instance, in fifteen studies reviewed by Smith (1985), only six revealed clear impairment. The outcome perceptibly depends on various factors including the SD induction method, sleep deprivation duration, nature of the task, and on organismic and procedural factors. Short lasting SD - less than 24 hours- provoked the most remarkable learning impairment when applied instantaneously before of conditioned tats aversion (CTA).
In an experiment conducted by Danguir and Nicolaidis (1976), thirsty Rats were exposed to water-tank SD before injecting them with an isotonic LiC1 solution that served concurrently as the Unconditioned stimuli (US) and conditioned stimuli (CS). They reported that even at 7.5 hours remarkably decreased the succeeding aversion of the salty taste. In a different study by Tarpy and Mclntosh 1(977), this finding was confirmed employing an advanced SD technique. To inhibit the thirsty Rats from reaching the surrounding groundwater the tank platforms were placed on an electrified floor, and the ground shock forced the Rats to remain on the elevated platforms. After 24 hours, saccharin conditioned stimuli exposure followed by LiC1poisoning no conditioned Taste aversion was provoked. However, the findings of the studies can be affected by various including unknown factors like the levels of water deprivation in the first study by Danguir and Nicolaidis (1976) and the effects of electrotactile stimuli in the second study.
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The present study is aimed at examining the influence of sleep deprivation on conditioned taste aversion under environments better fitting with the water tank method. This was achieved by using water-deprived Rats rather than hungry Rats and offering the Conditioned stimuli in liquid form rather than solid form.
General Methods:
Subjects
Male Teklad Rats of Long-Evans strain were bought from the breeding center of the institute. Rats lived in Plexiglas home cages with corn-cob bedding; food was availed on ad lib, and water was availed for 15 minutes during the daily experiments. The room temperatures were 72 °F (22.222 °C) and natural lighting at 15 :9 lite/dark cycle. The sleeping chamber was a 68 Liter plastic tub with 10-inch terracotta flower-pot with a 5-inch base.
Apparatus:
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Drinking conditioned stimuli
Grape juice – fresh extracts- were administered to the rat for 15 minutes followed immediately with an I.P. injection of 0.15% Lithium Chloride LiCl(Carolina Biological Supply; dose at 2% of body weight);
Procedure
After purchase the 14 Rats, they were placed in their various feeding boxes with each feeder stacked with enough food to and allowed enough feeding time. After stabilization was achieved, 13 Rats were placed under the experiment and one left as a control specimen. The Rats were subjected to 24 hours sleep deprivation, and immediately offered 20mLs of water (tap water) for 15 minutes on the first day of the experiment. On the second day of the experiment the Rats were offered 15 MmLs of Grape juice – fresh extracts- were administered to the Rats for 15 minutes followed immediately with an I.P. injection of 0.15% Lithium Chloride LiCl (Carolina Biological Supply; dose at 2% of body weight). The consumption volumes were recorded. On the day, while recording the consumption volumes, the arts were exposed to a standard diet. Retentions were tested in a single-choice retrieval test with the feeder containing 20mLs of both grape juice and tap water. Consumption volumes were established as the difference between original volumes placed in the feeder and the remaining volumes after retrieval test.
Experiment
The sleep derived induced impairment of conditioned taste aversion was conducted using a single bottle method. The experiment, therefore, attempted to examine The effects of PSD on realization conditioned Taste aversion to liquid food under the environments of single-choice retrieval.
Method
The procedure described above was adopted. The Rats were adapted to the feeding schedule during the three days. Sleep deprivation was started immediately after conditioning and terminated on the day before the regulated feeding sessions of the experiment day. On the third day of the experiments, the Rats were given LiCi injection on day five – immediately after grape juice ingestion. On the sixth day, both received standard food of 20mLs water and grape juice.
Results and discussion
Two-tailed t-test indicates the consumption of the grape juice was remarkably increased on day 2 in the control rat (t12 = P < 0.06) and not in the SD group ((t12 = 2.14). Comparison of day 3 indicates a decreased consumption of the standard foods after Sleep Deprivation (t12 = 2.31, p0.04). Comparison of day three on both groups indicates decreased intake of grape juice as compared today. The decrease was pronounced in the Sleep deprived Rats (t12 = 5.93, P< 0.01) that the control rat.
Comparison of the difference in grape juice intake on day 2 and 3 indicate the intake of the juice decreased significantly in Sleep Deprived Rats s. Food intake during the retrieval phase the experiment food intake was similar in all the Rats. Results of the experiment indicate that the polarity of the grape juice counteracted dislike and increased food intake in the control rat. Lower consumption of the grape juice may provoke the idea that the sleep deprival in the experiment Rats enhanced dislike/neophobia.
Conclusion and discussion
The finding of the study indicates that taste properties of liquid diets are differentially affected by sleep deprival. Strong conditioned taste aversion was realized in foods causing marked neophobia. These findings rea supported by earlier reports and research findings, however, the SD-induced impairment of Conditioned Sleep Deprival was less pronounced in the resent experiment. The single-choice retrieval method was not robust enough to demonstrate the week Conditioned Taste Aversion with enough clarity (Ogilvie and Broughton, 2009).
The weakening of the CTA to indigestible grape juice stimuli realized after the SD can mirror emotionality changes. It is likely that the development of shot lived gustatory elements is enhanced by fear-provoking properties of given flavors. SD prompted a reduction of neophobia in Rats and it is indicated by enhanced exploration and decreased urination and defecation of the Rats. Sleep Deprival enhances innovation in a Y-maze and reduces dislike towards fresh food. that was not the case with neophobia towards fresh taste which was not reduced by Sleep Deprivation but rather increased by SD in the current study (Hicks and Moore, 2009). It is more likely that the removal of the tank-stressful environments renders that Rats less sensitive to the surrounding ecological risks without reducing instinctive fears (Burešová and Bureš, 1980). The finding that Sleep Deprival did not affect AN to the tasted stimuli but somehow influenced the development of Conditioned Taste Aversion to the same stimuli agrees with the notion that both CTA and Neo-phobia are independent occurrences. Such a conclusion also supported by the other evidence syndicating that CTA is less sensitive than AN to functional lesions and disruptions (Gilley and Franchina, 1985).
The above contemplations support the conclusion that less than 24 hours Sleep Deprival does not hinder recognition of fresh taste but increases the neophobic dismissal. The gustatory elements produced during the initial presentation of the fresh taste is not remarkably affected by Sleep Deprival because it supports comparable AN in both controlled animals and Sleeps Deprived induced animals. Sleep deprival augmentation of Weak Conditioned Taste Aversion links to increased neophobia, and it is in agreement with the deep-rooted view that flavors producing marked rejection produce a strong Conditioned Taste Aversion (Hicks and Moore, 2009).
On the other side, CTA weakening by SD cannot be linked to the reduced salience of the gustatory trace. However, there are chances because of the reduce link-ability of the gustatory elements with the ensuing poisoning. Further research is needed of establishing the associability of SD to CTA considering other neutral factors not considered by this study like rat bread, controlled stimuli ingredients and ecological changes of the animals under study to help in specifying the environments conducive for CTA disruption and CTA enhancement.
References
Burešová, O. and Bureš, J. (1980). Post-ingestion interference with brain function prevents attenuation of neophobia in Rats. Behavioural Brain Research , 1(4), pp.299-312.
Danguir, J. and Nicolaidis, S. (1976). Impairments of learned aversion acquisition following paradoxical sleep deprivation in the rat. Physiology & Behavior , 17(3), pp.489-492.
Gilley, D. and Franchina, J. (1985). Effects of preexposure flavor concentration on conditioned aversion and neophobia. Behavioral and Neural Biology , 44(3), pp.503-508.
Hicks, R. and Moore, J. (1979). REM sleep deprivation diminishes fear in Rats. Physiology & Behavior , 22(4), pp.689-692.
Ogilvie, R. and Broughton, R. (2008). Sleep Deprivation and Measures of Emotionality in Rats. Psychophysiology , 13(3), pp.249-260.
Smith, C. (1985). Sleep states and learning: A review of the animal literature. Neuroscience & Biobehavioral Reviews , 9(2), pp.157-168.
Tarpy, R. and McIntosh, S. (1977). Generalized latent inhibition in taste-aversion learning. Bulletin of the Psychonomic Society , 10(5), pp.379-381.
