A bird-brain view of episodic memory.

In humans, the hippocampus plays a critical role in the formation of episodic memories. Although non-human animals are unable to report whether they also re-experience past events, at least some birds and mammals exhibit 'episodic-like' memory characterized by an ability to recall what happened where and when. In mammals, the hippocampus interacts closely with virtually the entire neocortex to form episodic-like memories. The hippocampus receives highly processed information from high-order association areas, and thereby the rest of the neocortex. Distinct neurophysiological hippocampal rhythms (theta and sharp-wave ripples) coordinate activity between the hippocampus and high-order association areas during the encoding and retrieval of information contributing to episodic-like memories. Although recent studies have demonstrated that food hoarding birds are able to remember what food they hid where and when, neuroanatomical and neurophysiological studies suggest that there may be a fundamental difference between episodic-like memory in birds and mammals. In contrast to the mammalian hippocampus, the avian hippocampus only receives visual and olfactory input; most high-order association areas in the avian brain involved in performing functions similar to those performed by neocortical association areas do not project to the hippocampus or structures providing it with direct input. Consistent with this neuroanatomical difference, mammalian-like rhythms involved in communicating between the hippocampus and neocortical high-order association areas have not been found in birds. Collectively, this suggests that information contributing to episodic-like memory is more limited and processed in a different manner in birds when compared to mammals.

Effects of sleep deprivation on wound healing.

Sleep deprivation is widely regarded as a stressor and has been shown to have significant effects on host defences. Severely sleep-deprived rats develop lesions on their paws and tails, suggesting possible deficits in the healing process. The purpose of this study was to assess the impact of rapid eye-movement (REM) sleep deprivation (RSD) on wound healing in a rat model. Male dark-hooded Long-Evans rats, 2-4 months old, were subjected to dorsal application of two sterile punch biopsies, each 3.5 mm in size. Biopsies were performed either immediately before or immediately after 5 days of sleep deprivation. Wound healing in REM sleep-deprived animals was compared with home cage control and yoked control animals. RSD did not produce differences in the rate of healing, regardless of the timing of the biopsy punch. RSD does not appear to have significant effects on wound healing and thus appears to act differently from other types of stressors on wound healing.

Anandamide modulates sleep and memory in rats.

In this study we have assessed the effect of the intracerebroventricular administration of anandamide (ANA) as well as its precursor metabolite arachidonic acid (AA), on the sleep-wakefulness cycle, memory formation, locomotor activity and pain perception. Our results have indicated that ANA strikingly increases slow-wave sleep (SWS)2 and rapid-eye movement (REM) sleep at the expense of wakefulness (W); while deteriorating memory consolidation. ANA also increases locomotor activity but does not modify pain perception threshold. In contrast, AA increases W and reduces SWS2, while deteriorating memory consolidation and increasing locomotor activity. AA has no effect on pain perception. These results suggest that the brain cannabinoid system participates in the modulation of the vigilance states and mnemonic processes. Additionally, they suggest that the effect on pain perception may be a peripheral rather than a central effect.

Fulminant amebic colitis: analysis of 55 cases.

UNLABELLED: Fulminant amebic colitis is a rare disease with high morbidity and mortality. PURPOSE: This study was designed to identify the most frequent clinical and histopathologic features of fulminant amebic colitis and to analyze results of surgical treatment and the existence of risk factors for mortality. MATERIALS AND METHODS: A retrospective analysis was conducted of clinical and histopathologic data of 55 patients with fulminant amebic colitis. Data were obtained from the files of autopsies and surgical operations that had been performed at a referral center in Mexico from 1943 through 1994. RESULTS: Median age was 52 (range, 18-79) years. There were 34 men (62 percent) and 21 women (38 percent). Diabetes mellitus and chronic alcoholism were the most frequent diseases in association with fulminant amebic colitis (40 and 31 percent, respectively). The most frequent clinical manifestations were abdominal pain, diarrhea, rectal bleeding, and fever. There was a coexistent amebic liver abscess in 54 percent of patients. The main histopathologic characteristics were necrosis, presence of trophozoites, and acute and/or chronic inflammation. Of 25 patients who underwent surgery, only six survived (operative mortality, 76 percent; overall mortality, 89 percent). The variables that correlated with mortality were longer duration of symptoms, lower count of leukocytes, nonsurgical treatment, nonresective surgical procedure, hospital admission before 1971, and invasion of trophozoites into or through the muscularis. CONCLUSIONS: The results may help to obtain an earlier diagnosis and establish proper treatment of fulminant amebic colitis.