Use of Neurolucida to assess the detailed morphology – including spines and synapses – of a layer 3 pyramidal neuron from the anterior cingulate cortex of a rhesus monkey. A) 40x confocal image of a layer 3 pyramidal neuron that was filled with biocytin during whole-cell patch-clamp recordings and subsequently processed with Alexa-Streptavidin-488. B) Basilar dendritic segment (indicated by the box in A), scanned in 2 channels: green= the neuron; red= VGat. C) Dendritic reconstruction indicated in light blue. Spine subtypes identified by the AutoSpine module (magenta= mushroom; yellow= thin; red= stubby). D) VGat-positive appositions (indicated by white dots) against the dendritic shaft and spines identified with AutoSynapse. Scale bars: A= 20 µm; B= 2 µm
The ball comes flying and you swing the bat. A car pulls out and you hit the brakes. As we go about our daily routines, we process everything we see in a region in the back of our brains known as the visual cortex. But when we sit down to plan a kitchen remodel, or next summer’s vacation, an area in the front of the brain gets activated, the prefrontal cortex, a region involved in higher level thinking.
Recent research has offered insight into the structure and function of neurons in these two distinct brain regions. Scientists at the Luebke Lab at Boston University set out to find out more about their morphology, and if their structural differences affect their behavior. Their study, published in the Journal of Neuroscience offers evidence that pyramidal neurons in the primary visual cortex (V1) and dorsolateral granular prefrontal cortex (dlPFC) of the rhesus monkey display “marked electrophysiological and structural differences.”
“We chose to examine these two areas because they represent distinct ends of the spectrum of neocortical complexity and specialization, from primary sensory processing by V1 to mediation of high-order cognitive processes by dlPFC,” the authors say in their paper.
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Life’s little pleasures often elude those suffering from depression, including rats, who show little interest in sugar water after experiencing stress. This behavior leads scientists to speculate that the illness might be characterized by a defect in the brain’s neural reward circuit.
Recent research focuses on a key element of this circuit – the nucleus accumbens (NAc), part of the brain region known as the ventral striatum, which is thought to regulate motivation and reward processing. In a new study of stress-induced depression in rats, researchers at the University of Minho in Braga, Portugal saw morphological changes in the dendrites of medium spiny neurons in the NAc, alongside disturbances in gene expression in this region. They also saw these changes reversed after administering antidepressants.
By using Neurolucida Explorer to analyze 3D reconstructions of medium spiny neurons generated with Neurolucida, the researchers observed longer than normal dendrites and greater spine density in the depressed rats. According to the paper, these findings contrast with studies of the hippocampus and prefrontal cortex, where chronic stress leads to shorter dendrites.
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