Repetition suppression of the rat auditory evoked potential at brief stimulus intervals.

An important prerequisite for the development of animal models of human auditory evoked potentials (AEP) is the accurate identification of homology. Prior research has revealed some remarkably similar response properties between rat and human AEPs, although there remains little consensus regarding the nature or validity of this correspondence. In the present study we seek to extend this research by examining the response properties of rat AEP as a function of stimulus repetition and interval. The aim being to determine whether rat AEP components show the same paradoxical reversal of repetition suppression observed for the human N100 AEP component at brief stimulus intervals. To achieve this, AEPs were recorded epidurally at the vertex in the freely moving rat in response to acoustic stimuli presented at random stimulus intervals between 50 and 5,000 ms. Using stimulation and analysis techniques to remove AEP waveform distortion due to overlapping AEP responses, the present results show that rat AEP components can be successfully resolved at intervals as brief as 50 ms. The results also demonstrate several fundamental types of correspondence between human and rat AEP components in terms of the sensitivity to stimulus interval and acoustic stimulus type. However the results found no evidence that rat AEP components show the reversal of repetition suppression at brief, relative to long, stimulus intervals as demonstrated for the N100 component in humans. The results are discussed in terms of EEG recording and AEP analysis procedures that provide promising avenues for future research.

Epidural Auditory Event-Related Potentials in the Rat to Frequency and duration Deviants: Evidence of Mismatch Negativity?

The capacity of the human brain to detect deviance in the acoustic environment pre-attentively is reflected in a brain event-related potential (ERP), mismatch negativity (MMN). MMN is observed in response to the presentation of rare oddball sounds that deviate from an otherwise regular pattern of frequent background standard sounds. While the primate and cat auditory cortex (AC) exhibit MMN-like activity, it is unclear whether the rodent AC produces a deviant response that reflects deviance detection in a background of regularities evident in recent auditory stimulus history or differential adaptation of neuronal responses due to rarity of the deviant sound. We examined whether MMN-like activity occurs in epidural AC potentials in awake and anesthetized rats to high and low frequency and long and short duration deviant sounds. ERPs to deviants were compared with ERPs to common standards and also with ERPs to deviants when interspersed with many different standards to control for background regularity effects. High frequency (HF) and long duration deviant ERPs in the awake rat showed evidence of deviance detection, consisting of negative displacements of the deviant ERP relative to ERPs to both common standards and deviants with many standards. The HF deviant MMN-like response was also sensitive to the extent of regularity in recent acoustic stimulation. Anesthesia in contrast resulted in positive displacements of deviant ERPs. Our results suggest that epidural MMN-like potentials to HF sounds in awake rats encode deviance in an analogous manner to the human MMN, laying the foundation for animal models of disorders characterized by disrupted MMN generation, such as schizophrenia.

Disclosing hepatitis C infection within everyday contexts: implications for accessing support and healthcare.

In this paper the authors quantify hepatitis C disclosure outcomes across social contexts and identify the factors associated with widespread disclosure of infection. In a cross-sectional survey of people with hepatitis C (N = 504) more than half reported receiving a bad reaction from someone following disclosure. Unauthorized disclosure occurred, and many participants had been pressured into disclosing their infection. The factors associated with widespread disclosure were: education level; knowing other people with hepatitis C; feeling fatigued; receiving disclosure advice; and experiencing unauthorized disclosure. Bad reactions following disclosure are common and may impede health-seeking behaviour including uptake of hepatitis C treatment.

Neonatal lipopolysaccharide and adult stress exposure predisposes rats to anxiety-like behaviour and blunted corticosterone responses: implications for the double-hit hypothesis.

The double-hit hypothesis posits that an early life genetic or environmental insult sets up a neural predisposition to psychopathology, which may emerge in the presence of a subsequent insult, or 'second hit' in later life. The current study assessed the effect of neonatal lipopolysaccharide (LPS) exposure on anxiety-like behaviours in the adult Wistar rat. Rats were administered either LPS (Salmonella enterica, serotype enteritidis, 0.05 mg/kg, i.p.) or saline (equivolume) on days 3 and 5 of life (birth=day 1). In adulthood (85 days), subjects were allocated to either "stress" or "no stress" treatment groups. For the "stress" group, subjects were exposed to a three-day stress protocol consisting of a 30 min period of restraint and isolation. The "no stress" group was left unperturbed but were handled during this period to control for handling effects between adult "stress" and "no stress" conditions. All animals then underwent behavioural testing using standardised tests of anxiety-like behaviour, including either the Hide Box/Open Field, Elevated Plus Maze (EPM) or Acoustic Startle Response (ASR). Time and event measures for restraint and isolation, the Hide Box/Open Field and EPM were recorded using automated tracking software. Startle amplitude and habituation across time was measured in the ASR test. Prior to and following behavioural test sessions, peripheral blood was collected to assess serum corticosterone and ACTH levels. Data analysis indicated that LPS-treated animals exposed to stress in adulthood exhibited increased anxiety-like behaviour across all behavioural tests compared to controls. Sexually dimorphic effects were observed with males exhibiting increased anxiety-related behaviours compared to females (p<.05). Neonatal LPS exposure induced a significant increase in corticosterone compared to controls (p<.05), whereas corticosterone responses to stress in adulthood were associated with a significantly blunted HPA axis response (p<.05). No differences in ACTH were observed. These results lend support to the double-hit hypothesis of anxiety-related behaviour, demonstrating that neonatal immune activation produces an enhanced propensity toward anxiety-related behaviour following stress in adulthood, and that this susceptibility is associated with alterations to HPA axis ontogeny.

Abstract-concept learning carryover effects from the initial training set in pigeons (Columba livia).

Three groups of pigeons were trained in a same/different task with 32, 64, or 1,024 color-picture stimuli. They were tested with novel transfer pictures. The training-testing cycle was repeated with training-set doublings. The 32-item group learned the same/different task as rapidly as a previous 8-item group and transferred better than the 8-item group at the 32-item training set. The 64- and 1,024-item groups learned the task only somewhat slower than other groups, but their transfer was better and equivalent to baseline performances. These results show that pigeons trained with small sets (e.g., 8 items) have carryover effects that hamper transfer when the training set is expanded. Without carryover effects (i.e., initial transfer from the 32- and 64-item groups), pigeons show the same degree of transfer as rhesus and capuchin monkeys at these same set sizes. This finding has implications for the general ability of abstract-concept learning across species with different neural architectures.

Prophylactic role for complementary and alternative medicine in perinatal programming of adult health.

BACKGROUND: The health status of an individual in adulthood is proposed to be determined by events occurring in the prenatal and early postnatal period. A common early life event proven to have long lasting effects on the developing fetus is stress, including pain. Exposure of fetal and neonatal infants to repetitive psychological (e.g., maternal stress) or physiological (e.g., pain, infection, and noise) stress during this period is proposed to alter mechanisms involved in the regulation of stress, immunological maturation, pain perception, and cognition. Such changes, which persist into adulthood, may occur via alterations in the development of the hypothalamic-pituitary-adrenal (HPA) axis. This process is typically referred to as 'perinatal programming'. Ontogenic alterations in the development of the HPA-axis have been related to a number of adult pathologies such as cardiovascular disease, type 2 diabetes, asthma, as well as psychopathologies such as anxiety and depression. OBJECTIVE: In this review, the effectiveness of complementary and alternative medicine (CAM), such as music, dietary supplements, massage and aromatherapy, in reducing perinatal stress in mothers and infants is examined. An emphasis is placed on these therapies as preventative measures which may be of value to individuals at risk of developing disease profiles associated with the consequences of adverse perinatal programming. The widening interest in perinatal programming and CAM suggests the potential for CAM to become a valuable tool in offsetting negative adult health outcomes resulting from perinatal programming associated with adverse gestational early life environments.

Domestic pigeons (Columba livia) discriminate between photographs of male and female pigeons.

We investigated whether pigeons are able to discriminate color photographs of male and female pigeons, using a categorical discrimination procedure. In Experiments 1 and 2B, 10 out of 14 pigeons learned the discrimination. Of these, 5 pigeons showed transfer to novel stimuli, demonstrating the categorical nature of the trained discrimination. Experiment 3 showed that the discriminative behavior was based primarily on the body, as opposed to the head and the neck region. In 1 out of 3 pigeons, the discriminative behavior was maintained by the black-and-white photographs. The results suggest that some pigeons have the ability to discriminate the sex of conspecifics without behavioral cues.

Domestic pigeons (Columba livia) discriminate between photographs of individual pigeons.

In two experiments, we examined the discrimination of photographs of individual pigeons by pigeons, using go/no-go discrimination procedures. In Experiments 1A and 1B, the pigeons were trained to discriminate 4 photographs of one pigeon from those of a number of pigeons. The subjects learned the discrimination, but their discriminative behavior did not transfer to new photographs taken from novel perspectives. When the pigeons were trained to discriminate between 20 photographs of five pigeons taken from four perspectives as the S+ and 20 photographs of five different pigeons as the S-, the subjects learned the discrimination, and this discriminative behavior partially transferred to new photographs taken from novel perspectives (Experiments 2A-2C). The results suggest that pigeons are able to discriminate among conspecific individuals, using stationary visual cues. This strengthens the assumption in evolutionary theory that animals can discriminate among individuals and encourages further investigation as to how this ability is used in various behaviors of animals.

HIV treatments optimism is associated with unprotected anal intercourse with regular and with casual partners among Australian gay and homosexually active men.

We examined HIV optimism and unprotected anal intercourse (UAI) in a nationwide sample of gay and homosexually active men. Questionnaires were distributed throughout Australia through pornographic catalogues. 1832 men responded, 1181 (64.5%) classified as gay community attached (GCA) and 651 (35.5%) as non-GCA (NGCA). Mean HIV optimism scores tended toward scepticism rather than optimism, with no significant difference between GCA and NGCA men. Men who had UAI with regular partners were significantly more optimistic than men who did not (P<0.001). There was a significant UAI-casual/GCA interaction (P<0.001). GCA men who engaged in UAI-casual were significantly more optimistic than GCA men who did not (P<0.001). Likewise, NGCA men who had UAI-casual were significantly more optimistic than NGCA men who did not (P<0.001). These findings corroborate earlier evidence that gay men's UAI is associated with - not necessarily caused by - HIV optimism. Importantly, these data come from a broad national sample rather than one drawn from within a 'gay precinct'.