Maternal behavior of mice with cingulate cortical, amygdala, or septal lesions.

Nest building, pup retrieving, and pup survival and growth were evaluated in primiparous control mice and those with cingulate cortical, neocortical, amygdala, or septal lesions. Mice with neocortical or amygdala lesions showed little or no deficits in maternal behavior. Mice with septal lesions were severely impaired in all aspects of maternal care. These mice did not build nests, showed a variety of aberrant behaviors during pup retrieving, and their pups died or gained significantly less weight than those of controls. Mice with cingulate cortical lesions retrieved pups more slowly than controls, and retrieving deficits were correlated with the extent of retrograde degeneration found in the anterior thalamic nuclei.     

Preoperative enrichment and behavioral recovery in rats with septal lesions

To assess the behavioral effects of preoperative differential housing male rats were placed in either enriched or isolated environments at weaning prior to receiving either sham operations or septal lesions when 57 days of age. Rats with septal lesions showed reduced habituation of ambulation and initially made fewer rears in an empty open field but made more object-contacts coupled with a lack of habituation in the object-filled field. Septal rats also showed severe impairments when tested in a 12-arm radial maze with 7 arms baited and 5 arms unbaited. Preoperative enrichment did not significantly affect these lesion-induced changes. Nevertheless, enrichment significantly lowered ambulation (but did not affect habituation) in the open field and increased the number of manipulatory relative to nonmanipulatory contacts. However, preoperatively enriched septal rats showed a deficit in spontaneous alternation (45%) in contrast to the high levels (83%) shown by intact enriched rats, whereas both intact and septal isolated rats showed similar levels of spontaneous alternation (68%). These results conflict with earlier reports that preoperative enrichment "protects" rats against the deficits produced by septal lesions.     

Considering olfactory stimulation for adults with age-related dementia.

Behavioral interventions and activities for adults with age-related dementias sometimes use olfactory stimulation; however, limitations to the usefulness of such stimulation are suggested by both neurological studies which show a large amount of degeneration in the cells of the olfactory bulb and studies of perception which indicate that adults with Alzheimer's disease and related dementias perform poorly on tests of smell identification and detection. Current approaches to using olfactory stimulation as a component of interventions for adults with age-related dementia may need to be either abandoned or reassessed.     

Effects of D-cycloserine on extinction of learned fear to an olfactory cue

D-cycloserine (DCS), a partial NMDA receptor agonist, facilitates extinction of learned fear in rats and has been used to treat anxiety disorders in clinical populations. However, research into the effects of DCS on extinction is still in its infancy, with visual cues being the primary fear-eliciting stimuli under investigation. In both human and animal subjects odors have been found to associate strongly with aversive events. Therefore, this study examined the generality of the effects of DCS on extinction by testing odor cues. Sprague-Dawley rats were conditioned and extinguished to an odor using varying parameters, injected with either saline or DCS (15 mg/kg) following extinction, and then tested for a freezing response 24 h later. Experiment 1 demonstrated that after 3 odor-shock pairings, rats did not display short-term extinction and DCS had no effect on long-term extinction. Experiment 2 demonstrated that after 3 odor-noise pairings, rats displayed significant short-term extinction and DCS significantly facilitated long-term extinction. Following 2 odor-shock pairings in Experiment 3, half the rats displayed short-term extinction ("extinguishers") and half did not ("non-extinguishers"). DCS facilitated long-term extinction in the "extinguishers" condition but not in the "non-extinguishers" condition. In Experiment 4, following 2 odor-shock pairings and an extra extinction session, DCS had a significant facilitatory effect on long-term extinction. Thus, extinction of freezing to an odor cue was facilitated by systemic injections of DCS, but only when some amount of within-session extinction occurred prior to injection.     

A modified version of the unique cue theory accounts for olfactory compound processing in honeybees

We investigated the capability of honeybees to discriminate between single odorants, binary olfactory mixtures, and ternary olfactory mixtures in olfactory conditioning of the proboscis extension reflex. In Experiment 1, three single odorants (A+, B+, and C+) and three binary mixtures of these odors (AB+, AC+, and BC+) were reinforced while the ternary compound, consisting of all three odors (ABC-), was nonreinforced. In Experiment 2, only one single odorant (A+) and one binary olfactory compound (BC+) were reinforced while the ternary compound (ABC-) consisting of the single odor and the binary compound was nonreinforced. We studied whether bees can solve these problems and whether the course of differentiation can be predicted by the unique cue theory, a modified unique cue theory, or Pearce's configural theory. Honeybees were not able to differentiate reinforced from nonreinforced stimuli in Experiment 1. However, summation to ABC observed at the beginning of training contradicts the predictions of Pearce's configural theory. In Experiment 2, differentiation between the single odorant A and the ternary compound developed more easily than between the binary compound BC and ABC. This pattern of differentiation is in line with a modified unique cue theory and Pearce's configural theory. Summation to ABC at the beginning of training, however, again was at odds with Pearce's configural theory. Thus, olfactory compound processing in honeybees can best be explained by a modified unique cue theory.