No abstract

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.

No abstract

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'.