The effects of talker familiarity on spoken word identification in younger and older listeners.

The present study was designed to examine age differences in the ability to use voice information acquired intentionally (Experiment 1) or incidentally (Experiment 2) as an aid to spoken word identification. Following both implicit and explicit voice learning, participants were asked to identify novel words spoken either by familiar talkers (ones they had been exposed to in the training phase) or by 4 unfamiliar voices. In both experiments, explicit memory for talkers' voices was significantly lower in older than in young listeners. Despite this age-related decline in voice recognition, however, older adults exhibited equivalent, and in some cases greater, benefit than young listeners from having words spoken by familiar talkers. Implications of the findings for age-related changes in explicit versus implicit memory systems are discussed.

Depression in schizophrenia: are neuroleptics, akinesia, or anhedonia involved?

To investigate the presence of a full depressive syndrome in schizophrenia years after the acute phase and factors linked to these depressive syndromes, 75 schizophrenia and schizoaffective patients and 32 patients with bipolar affective disorders were studied prospectively at index hospitalization and followed up 4.5 years later as part of the Chicago Followup Study. Over 30 percent of the schizophrenia patients showed full depressive syndromes during the followup year. Schizophrenia patients on neuroleptics were significantly more likely to show full depressive syndromes than those not on neuroleptics during the followup year. This relationship held after the level of posthospital psychosis was controlled. The data suggest that neuroleptic use is one factor linked to the depressive-like syndromes found in the posthospital phase in non-chronic schizophrenia samples. The results did not support the view that these depressive-like syndromes are only a function of akinesia, although they suggest that akinesia is probably one factor involved. The data indicate a strong link between neuroleptic use and anhedonia. These data suggest that one factor involved in the depressive-like symptoms found in schizophrenia patients could be interference by neuroleptics with the mesolimbic dopamine reinforcement system or the dopamine reward system.

In vitro toxicity of various classes of test agents using the neutral red assay on a human three-dimensional physiologic skin model.

A new three-dimensional human skin model consisting of several layers of actively dividing and metabolically active human neonatal foreskin-derived fibroblasts and epidermal keratinocytes grown on nylon mesh has been used to assess the in vitro toxicity of test agents from various classes. Utilizing a slight modification of the published neutral red viability assay for endpoint determination, we have assayed and obtained dose-dependent toxicity curves for test agents from the following classes: detergents (n = 15), alcohols (n = 5), metal chlorides (n = 10), perfumes and colognes (n = 5), shampoos (n = 4), conditioners (n = 3), moisturizers (n = 3), pesticides (n = 3), and antimicrobial preservatives (n = 4). Limited comparisons to in vivo ocular irritancy data with alcohols and detergents are encouraging. We have demonstrated the utility of this metabolically active dermal substrate containing naturally secreted collagen and other extracellular matrix proteins along with the neutral red viability assay for assessing the toxicity of a number of test agents from a variety of different classes with broad industrial applications.

Cytotoxicity testing using neutral red and MTT assays on a three-dimensional human skin substrate.

The use of a three-dimensional dermal culture system as a substrate in cytotoxicity assays is described. This substrate consists of several layers of dermal fibroblasts, derived from human foreskin, grown on pretreated nylon mesh. This physiological model of the human dermis has been used in conjunction with the neutral red assay and the MTT assay to assess the in vitro toxicity of a panel of 15 test agents from several different classes. NR(50) and MTT(50) endpoints (test agent concentrations yielding 50% viability) were obtained for compounds/formulations from the following groups: surfactants, alcohols, antimicrobial preservatives, metal chlorides and pesticides. In addition, the carboxylic ionophore, monensin, was tested in both assays. Limited comparisons of the in vitro neutral red and MTT results, using the three-dimensional culture system, with existing in vivo rabbit ocular irritancy data look promising. This three-dimensional model may afford several advantages over monolayer cultures.