Research Highlights: In Brief...

Manganese, a friend or foe to dopaminergic neurons?

GD Stanwood, DB Leitch, V Savchenko, J Wu, VA Fitsanakis, DJ Anderson, JN Stankowski, M Aschner, B McLaughlin (2009). Manganese exposure is cytotoxic and alters dopaminergic and GABAergic neurons within the basal ganglia. J Neurochem. 110 (1): 378-89.

Manganese is a naturally occurring element essential for the proper metabolism of amino acids, protein and lipids. It is crucial for maintaining proper cellular functioning including maintenance of redox states, facilitating protein conformation, modulating ion and energy homeostasis and overall signal transduction in neurons. Over exposure to manganese can result in various irreversible neurological phenomenon such as motor symptoms similar to that of Parkinsons, dystonia and gastrointestinal tract dysfunction. In this study, the authors explored the neurotxic potential of manganese in dopaminergic neurons in vivo in mice, looking especially at the vulnerability of nigrostrial pathways. They found that manganese chloride exposure, even at subtoxic doses changed the neuronal cytoskeleton of dopaminergic neurons. When the manganese treatment was extended to a period of 30days, a 20% reduction in TH-posiive neurons was observed in the substantia nigra pars compacta (SNpc), quantified by a widespread reduction in SNpc cell numbers through Nissil body staining. Parts of the basal ganglia including the striatum were also affected during treatment, showing sensitivity to nigrostriatal pathways. This study provides chronicles the timely repercussions of acute and chronic manganese exposure and provides an explanation for the motor manifestations observed from manganese intoxification.

 

How quickly can you detect a face? Temporal dynamics within neural constructs involved in the detection of familiar and novel faces

Blackford JU, Avery SN, Shelton RC, Zald DH. (2009). Amygdala temporal dynamics: temperamental differences in the timing of amygdala response to familiar and novel faces. BMC Neurosci. 10:145.

Inhibited temperament involves a predisposition of individuals to respond to new people, places or things with wariness or avoidance behavior, a characteristic trait known to be associated with increased risk for social anxiety disorder and major depression. Within the human brain, functional magnetic resonance imaging (fMRI) has shown the magnitude of blood oxygen level dependent (BOLD) responses in the amygdala for novel stimuli to be associated with inhibited temperament. The authors in this study used an event related fMRI paradigm to investigate the temporal dynamics (latency, duration and peak) of the BOLD response to novel stimuli within the amygdala. They presented both novel and familiar faces to both inhibited and uninhibited temperament populations. Results indicated that the amygdala in inhibited participants responded faster to novel faces than familiar faces. In addition, they found that the inhibited participants showed both a longer and greater amygdala response to all faces in comparison to the uninhibited population, even though there were no differences in the peak BOLD response. Blackford and colleagues speculate that this temporal computational bias for novel stimuli within the amygdala may lead to greater neophobic responses and could allude to a plausible mechanism for the development of social anxiety.