10 research outputs found
Dominance of Objects over Context in a Mediotemporal Lobe Model of Schizophrenia
Background: A large body of evidence suggests impaired context processing in schizophrenia. Here we propose that this impairment arises from defective integration of mediotemporal ‘what ’ and ‘where ’ routes, carrying object and spatial information to the hippocampus. Methodology and Findings: We have previously shown, in a mediotemporal lobe (MTL) model, that the abnormal connectivity between MTL regions observed in schizophrenia can explain the episodic memory deficits associated with the disorder. Here we show that the same neuropathology leads to several context processing deficits observed in patients with schizophrenia: 1) failure to choose subordinate stimuli over dominant ones when the former fit the context, 2) decreased contextual constraints in memory retrieval, as reflected in increased false alarm rates and 3) impaired retrieval of contextual information in source monitoring. Model analyses show that these deficits occur because the ‘schizophrenic MTL ’ forms fragmented episodic representations, in which objects are overrepresented at the expense of spatial contextual information. Conclusions and Significance: These findings highlight the importance of MTL neuropathology in schizophrenia, demonstrating that it may underlie a broad spectrum of deficits, including context processing and memory impairments. It is argued that these processing deficits may contribute to central schizophrenia symptoms such as contextuall
Recommended from our members
Oxidative discolouration in whole-head and cut lettuce: biochemical and environmental influences on a complex phenotype and potential breeding strategies to improve shelf-life
Lettuce discolouration is a key post-harvest trait. The major enzyme controlling oxidative discolouration
has long been considered to be polyphenol oxidase (PPO) however, levels of PPO and subsequent development of discolouration symptoms have not always correlated. The predominance of a latent state of the enzyme in plant tissues combined with substrate activation and contemporaneous suicide inactivation
mechanisms are considered as potential explanations for
this phenomenon. Leaf tissue physical properties have
been associated with subsequent discolouration and
these may be influenced by variation in nutrient
availability, especially excess nitrogen and head maturity at harvest. Mild calcium and irrigation stress has
also been associated with a reduction in subsequent
discolouration, although excess irrigation has been
linked to increased discolouration potentially through
leaf physical properties. These environmental factors,
including high temperature and UV light intensities,
often have impacts on levels of phenolic compounds
linking the environmental responses to the biochemistry
of the PPO pathway. Breeding strategies targeting the
PALand PPOpathway biochemistry and environmental
response genes are discussed as a more cost-effective
method of mitigating oxidative discolouration then
either modified atmosphere packaging or post-harvest
treatments, although current understanding of the
biochemistry means that such programs are likely to
be limited in nature and it is likely that they will need to be deployed alongside other methods for the foreseeable future
Effects of combined Abiotic Stresses on Growth, Trace Element Accumulation, and Phytohormone Regulation in Two Halophytic Species
for 1 month with an irrigation solution supplemented with 200 mM NaCl and 400 μM Cd2+ or 400 μM Cu2+ was evaluated. The effect of the combined stress conditions on hormone signaling was also assessed. Biomass production and chlorophyll content decreased under Cd2+ stress in both species, whereas Cu2+ had a lower impact on plant performance. The different plant sensibilities to the two trace elements assayed indicate that each metal has a different effect on plants. Furthermore, the deleterious effect of metal toxicity was alleviated when NaCl was added to the irrigation solution, demonstrating that NaCl improves plant performance and tolerance of halophytic species to cope with trace element intoxication. Results show that both species accumulated important quantities of Cd2+ and Cu2+ in roots (Cd2+: 2,690–3,130 μg g−1 DW and Cu2+: 2,070–2,770 μg g−1 DW); this finding allows us to classify these species among the hyperaccumulator plants. Cd2+ and Cu2+ differently affected endogenous phytohormone contents in both species. Data suggest an essential involvement of roots on the regulation of tolerance to trace elements. Therefore, indole-3-acetic acid levels increased in roots of both species irrigated with high levels of Cd2+, which suggests that the auxin may stimulate root promotion and growth under these stress conditions. Other compounds, classically considered as “stress hormones” showed very different patterns of accumulation. Whereas, salicylic acid (SA) levels in roots and leaves increased in response to Cd2+, root contents of jasmonic acid (JA), and abscisic acid (ABA) decreased. In leaves, the rambling pattern of accumulation observed for JA and ABA suggested the lack of a specific role in regulation against trace element toxicity. Together, data suggest that SA could act as a specific signal that detects trace element toxicity, whereas JA and ABA promote general responses against abiotic stress