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Biomedical subjects

C Rittenhouse

Publications and source records attributed to C Rittenhouse.

3 recordsLinked to original sources
PubMed1999

Sleep-induced changes in associative memory.

The notion that dreaming might alter the strength of associative links in memory was first proposed almost 200 years ago. But no strong evidence of such altered associative links has been obtained. Semantic priming can be used to quantify the strength of associative links between pairs of words; it is thought to measure the automatic spread of activation from a "node" representing one word to nodes representing semantically related words. Semantic priming could thus be used to test for global alterations in the strengths of associative links across the wake-sleep cycle. Awakenings from REM and nonREM (NREM) sleep produce a period of state carry-over during which performance is altered as a result of the brain's slow transition to full wakefulness, and cognitive testing in this period can provide information about the functioning of the brain during the prior sleep period. When subjects were tested across the night--before and after a night's sleep as well as immediately following forced awakenings from REM and NREM sleep--weak priming (e. g., thief-wrong) was found to be state dependent (p = 0.016), whereas strong priming (e.g., hot-cold) was not (p = 0.89). Weak primes were most effective in the presleep and REM sleep conditions and least effective in NREM and postsleep conditions. Most striking are analyses comparing weak and strong priming within each wake-sleep state. Contrary to the normal pattern of priming, subjects awakened from REM sleep showed greater priming by weak primes than by strong primes (p = 0.01). This result was seen in each of three protocols. In contrast, strong priming exceeded weak priming in NREM sleep. The shift in weak priming seen after REM sleep awakenings suggests that cognition during REM sleep is qualitatively different from that of waking and NREM sleep and may reflect a shift in associative memory systems, a shift that we hypothesize underlies the bizarre and hyperassociative character of REM-sleep dreaming. Known changes in brainstem activity that control the transition into and maintenance of REM sleep provide a possible explanation of this shift.

Adult↗
PubMed1992

Dynamic suppression of REM sleep by parenteral administration of the serotonin-1 agonist eltoprazine.

The purpose of this study was to determine the effects of the serotonin-1 agonist eltoprazine on the control of rapid eye movement (REM) sleep. Continuous polygraph recordings were performed for 15-17 days in four adult male cats. During the first 5 control days cats received injections of 0.9% saline intraperitoneally (i.p.) twice per day (b.i.d.). Over the next 5-7 days cats received injections of 0.9% saline intraperitoneally (i.p.) twice per day (b.i.d.). Over the next 5-7 days cats received eltoprazine i.p. (1-2 mg/kg, b.i.d.). For the final 5 recovery days cats received saline alone. During the saline control period, the mean REM sleep percent was 13.8 +/- 0.91%. When eltoprazine was administered for the subsequent 5-7 days, the mean REM percent was reduced to 1.5 +/- 0.59%. During the 5-day recovery period, REM percent increased significantly (p less than 0.0001) above both control and drug injection values to a mean of 24.5 +/- 1.3% with a maximum on recovery day 1 of 28.4 +/- 2.6% (n = 4). In addition to REM suppression, eltoprazine produced other electroencephalographic changes: an increase in slow-wave sleep (S) percent without any change in overall wake (W) percent; an increase in electromyogram (EMG) amplitude; and a decrease in ponto-geniculo-occipital (PGO) wave activity. PGO wave frequency and REM% increased significantly during the recovery period. Thus our findings demonstrate REM and PGO suppression by eltoprazine and document dramatic rebound effects following its withdrawal.

Animals↗